# Thread for questions with scientific answers



## violadude

First question: Why does having mint in your mouth make water colder, sometimes to the point where it's so cold it hurts?


----------



## Dodecaplex

I don't know.


Second question: why is Newtonian mechanics incompatible with Maxwell's equations?


----------



## Mesa

violadude said:


> First question: Why does having mint in your mouth make water colder, sometimes to the point where it's so cold it hurts?


I prefer to handle the heavy science with visual aids.


----------



## Cnote11

This thread just took a turn for the amazing.


----------



## mmsbls

Dodecaplex said:


> I don't know.
> 
> Second question: why is Newtonian mechanics incompatible with Maxwell's equations?


The technical answer is that Maxwell's equations are not invariant under Galilean transformations, but Newton's equations are invariant. That sounds complicated, but it's not so hard to understand.

Newton's equations are the same whether you measure motion in a reference frame at rest or whether the reference frame is moving at a constant velocity (and assume that time is the same in both frames). Imagine someone on a stationary train throwing a ball at 10 kilometers per hour (kph). Someone on the ground (outside the train) will measure the ball's velocity as 10 kph. If the train is moving at 10 kph in the direction the ball is thrown, the person on the ground will measure the ball's velocity as 20 kph. In other words the velocities add (the train's and ball's velocities). The velocity of the ball _is not the same_ in the two situations. That is what Newton's equations would predict.

In Maxwell's equations, something different happens. Imagine someone shining a flashlight on a stationary train. Someone on the ground measures the light beam traveling at the speed of light. We use c as the speed of light (i.e. c ~ 300,000 kilometers per second). If the train is moving at 10 kph in the direction of the light, Newton's equations would "expect" that the person on the ground would measure the speed of the light beam to be c plus the speed of the train or c + 10 kph. Maxwell's equations say that the speed of a light beam is the same in all reference frames (i.e. c). So Maxwell's equations predict that the person on the ground will measure the light beam to travel at c _and not_ at c + 10 kph when the train is moving.

Newton's equations contradict Maxwell's equations in that the former does not allow for certain speeds to be the same in different moving reference frames. I mentioned that we have to assume that time is the same in both frames for Newton's equations. It turns out that the solution to the contradiction involves time being measured differently in the two reference frames, but that's rather complicated.


----------



## Dodecaplex

Beautiful. Special relativity never ceases to amaze me, no matter how many times I go and read its basic premises over and over again. It is a scientific poem.


----------



## regressivetransphobe

Why is the sky blue? Why is water wet? Why did Judas rat to Romans while Jesus slept?


----------



## Lukecash12

Is _H. habilis_ one species or two? I would say that the differences between KNM-ER 1470 and KNM-ER 1813 are too great to be explained away by sexual dimorphism, especially when it comes to dentition.


----------



## violadude

regressivetransphobe said:


> Why is the sky blue? Why is water wet? Why did Judas rat to Romans while Jesus slept?


I must be missing something. I don't understand the connection between the questions and the picture.


----------



## Igneous01

violadude said:


> I must be missing something. I don't understand the connection between the questions and the picture.


the lyrics were from a wutang song, which I remember linking to, and now forgot the name of it AGAIN!!!


----------



## Chrythes

Why does the Tesseract has that particular shape? 
What does the cube has to gain/change in order to become like this?


----------



## Cnote11

violadude said:


> I must be missing something. I don't understand the connection between the questions and the picture.


----------



## Kopachris

violadude said:


> First question: Why does having mint in your mouth make water colder, sometimes to the point where it's so cold it hurts?


Since no one else answered it: it doesn't. Menthol stimulates the nerves in your mouth in the same way as capsaicin, but opposite. While capsaicin produces an irritating, burning effect, menthol can be used as an analgesic or a counter-irritant. Menthol triggers cold-sensitive TRPM8 receptors just as capsaicin triggers heat-sensitive receptors. Neither menthol nor capsaicin readily dissolve in water, but water does help them reach the right heat/cold receptors in the mouth.

And now my question: why does stainless steel neutralize the smell of garlic and onion?


----------



## mmsbls

regressivetransphobe said:


> Why is the sky blue? Why is water wet? Why did Judas rat to Romans while Jesus slept?


The first question is a scientific one. Water does not have a property of wetness, but rather our we psychologically place that property onto it.

The sky is blue due to a phenomenon known as Raleigh scattering. Particles in the atmosphere smaller than the wavelength of light will scatter light. The scattering is a function of the wavelength - the smaller the wavelength, the larger the scattering. Blue light has a smaller wavelength than red, orange, yellow, and green light. Consequently, light toward the blue end of the spectrum scatters more, so when we look toward the sky but away from the sun, we see the color of the most scattered light (i.e. blue).


----------



## Philip

mmsbls said:


> The technical answer is that Maxwell's equations are not invariant under Galilean transformations, but Newton's equations are invariant. That sounds complicated, but it's not so hard to understand.
> 
> Newton's equations are the same whether you measure motion in a reference frame at rest or whether the reference frame is moving at a constant velocity (and assume that time is the same in both frames). Imagine someone on a stationary train throwing a ball at 10 kilometers per hour (kph). Someone on the ground (outside the train) will measure the ball's velocity as 10 kph. If the train is moving at 10 kph in the direction the ball is thrown, the person on the ground will measure the ball's velocity as 20 kph. In other words the velocities add (the train's and ball's velocities). The velocity of the ball _is not the same_ in the two situations. That is what Newton's equations would predict.
> 
> In Maxwell's equations, something different happens. Imagine someone shining a flashlight on a stationary train. Someone on the ground measures the light beam traveling at the speed of light. We use c as the speed of light (i.e. c ~ 300,000 kilometers per second). If the train is moving at 10 kph in the direction of the light, Newton's equations would "expect" that the person on the ground would measure the speed of the light beam to be c plus the speed of the train or c + 10 kph. Maxwell's equations say that the speed of a light beam is the same in all reference frames (i.e. c). So Maxwell's equations predict that the person on the ground will measure the light beam to travel at c _and not_ at c + 10 kph when the train is moving.
> 
> Newton's equations contradict Maxwell's equations in that the former does not allow for certain speeds to be the same in different moving reference frames. I mentioned that we have to assume that time is the same in both frames for Newton's equations. It turns out that the solution to the contradiction involves time being measured differently in the two reference frames, but that's rather complicated.


My commutation skills are not as developed as mmsbls'. I would've said, because:

c = 1/√ε[SUB]0[/SUB]μ[SUB]0[/SUB]

where c, ε[SUB]0[/SUB], and μ[SUB]0[/SUB], are, respectively, the speed of light, the electric constant, and the magnetic constant.


----------



## Mesa

Is it just me or does Clara Schumann radiate like a hot body?


----------



## samurai

@ Philip, I'll take your word on that.


----------



## science

If I understood George Williams (which I doubt I did), infertile ants share more genes with their mother's children than they would with their own children. If that's right, how does it work? If it's wrong, what's the thing with ants and genes and why it's good for the genes of the sterile workers to be sterile workers?


----------



## Fsharpmajor

mmsbls said:


> The sky is blue due to a phenomenon known as Raleigh scattering. Particles in the atmosphere smaller than the wavelength of light will scatter light. The scattering is a function of the wavelength - the smaller the wavelength, the larger the scattering. Blue light has a smaller wavelength than red, orange, yellow, and green light. Consequently, light toward the blue end of the spectrum scatters more, so when we look toward the sky but away from the sun, we see the color of the most scattered light (i.e. blue).


This is also why blue eyes appear blue. There isn't actually a blue pigment in the irises of blue eyes.


----------



## Fsharpmajor

science said:


> If I understood George Williams (which I doubt I did), infertile ants share more genes with their mother's children than they would with their own children. If that's right, how does it work? If it's wrong, what's the thing with ants and genes and why it's good for the genes of the sterile workers to be sterile workers?


I might be able to take a stab at this one if you can provide a link for me to read. Googling it doesn't seem to turn up anything very relevant.


----------



## Cnote11

Fsharp, your new avatar is breathtaking.


----------



## mmsbls

science said:


> If I understood George Williams (which I doubt I did), infertile ants share more genes with their mother's children than they would with their own children. If that's right, how does it work? If it's wrong, what's the thing with ants and genes and why it's good for the genes of the sterile workers to be sterile workers?


Species such as bees and ants exhibit haplodiploidy. Females are diploid (they have two pair of each chromosome) while males are haploid (they only have one of each chromosome). Males come from unfertilized eggs, and females come from fertilized eggs. As a result, daughters are more related to each other than they are to their mother or brothers.

Assume the mothers chromosomes are A and B. The father's chromosome is C. Then -

Daughters = AC or BC
Sons = A or B

Daughters have, on average, 75% of the same genes (some are related 100% the same and some are 50% the same depending on which chromosome they inherit from their mother ). Daughters have 50% of their mother's and offspring's genes. So daughters are more closely related to their sisters than to their offspring. In theory they would "want" to create more sisters than to have children of their own. These daughters are worker ants (or bees) and work to allow their mother to make more sisters (and a few males to mate with queens in other nests).


----------



## science

mmsbls said:


> Species such as bees and ants exhibit haplodiploidy. Females are diploid (they have two pair of each chromosome) while males are haploid (they only have one of each chromosome). Males come from unfertilized eggs, and females come from fertilized eggs. As a result, daughters are more related to each other than they are to their mother or brothers.
> 
> Assume the mothers chromosomes are A and B. The father's chromosome is C. Then -
> 
> Daughters = AC or BC
> Sons = A or B
> 
> Daughters have, on average, 75% of the same genes (some are related 100% the same and some are 50% the same depending on which chromosome they inherit from their mother ). Daughters have 50% of their mother's and offspring's genes. So daughters are more closely related to their sisters than to their offspring. In theory they would "want" to create more sisters than to have children of their own. These daughters are worker ants (or bees) and work to allow their mother to make more sisters (and a few males to mate with queens in other nests).


I think I've got it! Thanks!


----------



## Polednice

I'm going to ask a dumb question or two about probabilities now because my little monkey brain has a hard time understanding.

So, is there some kind of mathematics (what's it called? how do you do it?) where you can work out a percentage confidence in a chance event occurring? Say, for example, a lottery ticket has a 1 in 10 million chance of winning. If you were to buy 10 million tickets, could you say that you are X% confident that you have a winning ticket? And how far do you need to go to push that confidence upwards of 99%? I take it that 100% confidence is impossible because that would mean the event is no longer down to chance - is there an upper limit?

And, given even the most unlikely events, if you were to do enough iterations, could you always be confident that something would occur? For example, if I was tossing a coin and wanted to see a billion heads in a row, could I do an astronomical number of tosses and be extremely confident that I would see a billion heads, or is the chance of a billion heads so ridiculously low that no number of iterations is likely to see it happen?


----------



## starthrower

regressivetransphobe said:


> Why did Judas rat to Romans while Jesus slept?


He was sick of eating insects and chewing on roots. He figured he'd make a little coin and have a nice meal.


----------



## mmsbls

Polednice said:


> So, is there some kind of mathematics (what's it called? how do you do it?) where you can work out a percentage confidence in a chance event occurring? Say, for example, a lottery ticket has a 1 in 10 million chance of winning. If you were to buy 10 million tickets, could you say that you are X% confident that you have a winning ticket? And how far do you need to go to push that confidence upwards of 99%? I take it that 100% confidence is impossible because that would mean the event is no longer down to chance - is there an upper limit?


The general field is called Probability and Statistics, and there are many equations (depending on the conditions) that allow one to calculate probabilities of specific events occurring. Further you can calculate the confidence level that an event will occur given a number of trials. I'm not sure how much detail you're asking for.

100% confidence is not impossible. If one asks, "How many socks will I have to remove from a drawer containing 2 colors of socks to be certain that I will have a matching pair?" The answer is 3 with 100% confidence.



Polednice said:


> And, given even the most unlikely events, if you were to do enough iterations, could you always be confident that something would occur? For example, if I was tossing a coin and wanted to see a billion heads in a row, could I do an astronomical number of tosses and be extremely confident that I would see a billion heads, or is the chance of a billion heads so ridiculously low that no number of iterations is likely to see it happen?


Any event that has a non-zero probability will eventually happen given enough trials. While tossing a billion heads in a row is possible, it is absurdly unlikely. If every subatomic particle in our universe had tossed a coin 350 times every nanosecond since the beginning of our universe, the probability that there would be a single instance of 350 heads in a row would be roughly 50%. The probability is roughly 1 out of 10 to the 106 power.


----------



## Guest

mmsbls said:


> The probability is roughly 1 out of 10 to the 106 power.


I like those odds!!!


----------



## Philip

Polednice said:


> I'm going to ask a dumb question or two about probabilities now because my little monkey brain has a hard time understanding.
> 
> So, is there some kind of mathematics (what's it called? how do you do it?) where you can work out a percentage confidence in a chance event occurring? Say, for example, a lottery ticket has a 1 in 10 million chance of winning. If you were to buy 10 million tickets, could you say that you are X% confident that you have a winning ticket? And how far do you need to go to push that confidence upwards of 99%? I take it that 100% confidence is impossible because that would mean the event is no longer down to chance - is there an upper limit?
> 
> And, given even the most unlikely events, if you were to do enough iterations, could you always be confident that something would occur? For example, if I was tossing a coin and wanted to see a billion heads in a row, could I do an astronomical number of tosses and be extremely confident that I would see a billion heads, or is the chance of a billion heads so ridiculously low that no number of iterations is likely to see it happen?


The probability of something happening is not the same thing as the confidence level. The confidence level has to do with determining the minimum sample size to conduct a survey in a population, which has a certain distribution with respect to a measured parameter. It's usually something like 95% or 99%, which means 95% (or 99%) of the population is within an arbitrary margin of error (confidence interval). It can be quite confusing.

Now for probabilities... if you do a coin toss, intuitively, the "chances" of winning don't add up normally, ie. two coin tosses don't guarantee (100%) one heads, even if the probability is "twice 50%". To add them up properly, in that particular case, you have to take into account all possible outcomes: {HH, HT, TH, TT}, but first you must define your actual problem:

*What is the probability of getting H at least once after 2 trials, given that the coin is fair and that all trials are independent from one another?*

To solve this, the best way is to subtract the probability of getting no H (or all Ts), p[SUP]n[/SUP], from the total probability, 1. That is:

P = 1 - p[SUP]n[/SUP] = 1 - (0.5)[SUP]2[/SUP] = 75%

where P is the probability of getting at least one H, p is the probability of getting one H in a single trial, and n the number of trials

*The probability of getting a billion heads in a billion tosses:*

P = p[SUP]n[/SUP] = (0.5)[SUP]1,000,000,000[/SUP] = very small

*How many tickets must I buy to get 99% probability of winning a 1 in 10 million lottery?*

This problem is not really solvable as it is stated... Does there have to be a winner? Can there be multiple winners? How is 1 in 10 million calculated? Is it a number lottery?

If the case of a number lottery, you have to evaluate the total number of permutations given by the restrictions applied on the numbers, eg. can numbers be repeated?

The probability of winning is simply 1 over the total number of permutations times the number of tickets you purchased. For example:

P = (1/10,000,000)*n

where P is the probability of winning a 1 in 10 million number lottery, and n the number of unique tickets you purchased

That is, if you buy all possible tickets, your chances of winning are 100%.

Edit:

Thus... in a 6/49 lottery, in which you have 1 in 13,983,816 chances of winning, you'd have to buy at least *13,843,978* unique tickets to get over *99%* probability of winning.


----------



## Polednice

Thanks for the responses guys, that was extremely helpful! I also realise now that my lottery example was a bit silly.


----------



## science

That reminds me of a calculation I saw years ago in a creationist book, something like: 

(the age of the universe in seconds) x 
(the number of interactions a subatomic particle can undergo in a second) x 
(the number of particles that could fit in the volume of the visible universe) = 
the maximum number of events that could have happened in the history of our visible universe 

I'm not sure how all that is figured out, but anything substantially less probable than that can be assumed not to have happened. 

Anybody heard of anything like this?


----------



## Polednice

Not precisely that one, but I have silly creationist maths that tries to show the probability of my consciousness is too small for it to be down to "random chance".


----------



## Polednice

Why is some squash (diluted juice) called "cordial"?


----------



## mmsbls

science said:


> That reminds me of a calculation I saw years ago in a creationist book, something like:
> 
> (the age of the universe in seconds) x
> (the number of interactions a subatomic particle can undergo in a second) x
> (the number of particles that could fit in the volume of the visible universe) =
> the maximum number of events that could have happened in the history of our visible universe
> 
> I'm not sure how all that is figured out, but anything substantially less probable than that can be assumed not to have happened.


The general idea is that some creationists maintain that the probability of some molecule being created by chance is inconceivably small compared to anything in the real universe so it could never have happened. For example, the beta globin molecule (part of hemoglobin) has 146 amino acids. Since there are 20 different amino acids that make up proteins, the probability that the beta globin molecule will form by chance from a random amount of amino acids is 1 out of 20^146 or roughly 1 out of 10 to the 190 power.

The universe is 4 x 10^17 seconds old (4 times 10 to the 17)
There are roughly 10^80 particles in the known universe
Assume 10^12 interactions per second

That only gives 10^109 interactions for all the particles since the beginning of time. This is much (much, much, much) smaller than the probability of creating a beta globin molecule so beta globin molecules could not have formed spontaneously.

Another creationist argument gives the time since humans first existed at roughly 4000 years (Morris ed., Scientific Creationism). Morris et. al. assume that human generations are roughly 40 years, humans lifetimes are roughly 40 years, and the number of children per adult pair is 2.46. In 100 generations (4000 years) there will be roughly 2 billion people (2 x 1.23^100). If humans were around for a much longer time, there would be far too many humans; therefore, humans have been around for about 4000 years.

A similar argument gives a different figure. E. coli have generation times of 17 minutes and can live for a much, much longer time. After a bit more than 3 days, there will be more E. coli than subatomic particles in the universe. Therefore, the universe certainly is less than 4 days old. Who knew?


----------



## Philip

mmsbls said:


> The general idea is that some creationists maintain that the probability of some molecule being created by chance is inconceivably small compared to anything in the real universe so it could never have happened. For example, the beta globin molecule (part of hemoglobin) has 146 amino acids. Since there are 20 different amino acids that make up proteins, the probability that the beta globin molecule will form by chance from a random amount of amino acids is 1 out of 20^146 or roughly 1 out of 10 to the 190 power.
> 
> The universe is 4 x 10^17 seconds old (4 times 10 to the 17)
> There are roughly 10^80 particles in the known universe
> Assume 10^12 interactions per second
> 
> That only gives 10^109 interactions for all the particles since the beginning of time. This is much (much, much, much) smaller than the probability of creating a beta globin molecule so beta globin molecules could not have formed spontaneously.
> 
> Another creationist argument gives the time since humans first existed at roughly 4000 years (Morris ed., Scientific Creationism). Morris et. al. assume that human generations are roughly 40 years, humans lifetimes are roughly 40 years, and the number of children per adult pair is 2.46. In 100 generations (4000 years) there will be roughly 2 billion people (2 x 1.23^100). If humans were around for a much longer time, there would be far too many humans; therefore, humans have been around for about 4000 years.
> 
> A similar argument gives a different figure. E. coli have generation times of 17 minutes and can live for a much, much longer time. After a bit more than 3 days, there will be more E. coli than subatomic particles in the universe. Therefore, the universe certainly is less than 4 days old. Who knew?


That's what happens when you adopt a lawyer-type mentality instead of a scientific approach. That is, having a preconceived idea and then going to the field, looking for evidence of it; as opposed to collecting facts and subsequently developing a falsifiable, more general theory. Two methods going in opposite direction.


----------



## aleazk

mmsbls said:


> The general idea is that some creationists maintain that the probability of some molecule being created by chance is inconceivably small compared to anything in the real universe so it could never have happened. For example, the beta globin molecule (part of hemoglobin) has 146 amino acids. Since there are 20 different amino acids that make up proteins, the probability that the beta globin molecule will form by chance from a random amount of amino acids is 1 out of 20^146 or roughly 1 out of 10 to the 190 power.
> 
> The universe is 4 x 10^17 seconds old (4 times 10 to the 17)
> There are roughly 10^80 particles in the known universe
> Assume 10^12 interactions per second
> 
> That only gives 10^109 interactions for all the particles since the beginning of time. This is much (much, much, much) smaller than the probability of creating a beta globin molecule so beta globin molecules could not have formed spontaneously.
> 
> Another creationist argument gives the time since humans first existed at roughly 4000 years (Morris ed., Scientific Creationism). Morris et. al. assume that human generations are roughly 40 years, humans lifetimes are roughly 40 years, and the number of children per adult pair is 2.46. In 100 generations (4000 years) there will be roughly 2 billion people (2 x 1.23^100). If humans were around for a much longer time, there would be far too many humans; therefore, humans have been around for about 4000 years.
> 
> A similar argument gives a different figure. E. coli have generation times of 17 minutes and can live for a much, much longer time. After a bit more than 3 days, there will be more E. coli than subatomic particles in the universe. Therefore, the universe certainly is less than 4 days old. Who knew?


That's fine, hemoglobin is something that advanced organisms, like humans, have. So, surely is synthesized by the body (given your argument about the probabilities). But for proving Creationism, you should do the calculation for more simpler molecules, present in the most basic organisms (_evolution_ will then make this organism more complex, and capable and capable of synthesizing hemoglobin, for example). The Miller-Urey experiment has show that some of this basic molecules could have formed in the primitive Earth. Recent experiments have constructed RNA chains. I don't know the details, but this is the path to investigate.


----------



## Machiavel

mmsbls said:


> The first question is a scientific one. Water does not have a property of wetness, but rather our we psychologically place that property onto it.
> 
> The sky is blue due to a phenomenon known as Raleigh scattering. Particles in the atmosphere smaller than the wavelength of light will scatter light. The scattering is a function of the wavelength - the smaller the wavelength, the larger the scattering. Blue light has a smaller wavelength than red, orange, yellow, and green light. Consequently, light toward the blue end of the spectrum scatters more, so when we look toward the sky but away from the sun, we see the color of the most scattered light (i.e. blue).


True on everything you said but it is also because our eyes have some problems with some wave-length and then our brain is saturated with the blue. Humans eye is just not that good with violet so blue wins. kinda lol

The sky is slightly violet but due to our eyes and brain we keep more of the blue


----------



## mmsbls

Machiavel said:


> True on everything you said but it is also because our eyes have some problems with some wave-length and then our brain is saturated with the blue. Humans eye is just not that good with violet so blue wins. kinda lol
> 
> The sky is slightly violet but due to our eyes and brain we keep more of the blue


Yes, thanks. That's correct. Also the sun's output of violet light is not as intense as its output of blue light.


----------



## Chrythes

What is a Qubit and how does it work?
I know it can be a "0" and a "1" at the same time. But that's pretty much it. :lol:


----------



## Mesa

I've noticed reading the wikipedia article on the qubit twice takes about the same length of time as this:





It mirrors what i took home mentally from the article impeccably.

Curiousness, understanding, doubt, confusion, understanding again, contemplation, *hey guys i think i really understand it now*, no, that was just wind, a last try to willingly get to grips with the concept, accept inability to ever become a quantum computing engineer, do a five minute long dance inside my head, start to attempt anagrams with people's silly surnames by the end.


----------



## Philip

Chrythes said:


> What is a Qubit and how does it work?
> I know it can be a "0" and a "1" at the same time. But that's pretty much it. :lol:


This is the best explanation you will ever get:


----------



## science

I'd like a really good book on the history of chemistry, particularly from about 1700 to 1900. Something that'll help me teach my history classes. Anyone know of one?


----------



## regressivetransphobe

All I know is god created the earth because the bibel says so, and the bible was written by god AND jesus. Darwin was written bye Hitler. Christians 1 atheists 0


----------



## Chrythes

Philip said:


> This is the best explanation you will ever get:


Each line of the sphere holds information? Does that sphere mean that we can essentially manipulate more information? Does it work like a "storage device"?
And does gravity exist everywhere? Does an object far from us feel earth's gravitational force?


----------



## emiellucifuge

Any mass exerts gravity on any other mass, the force being inversely proportional to the square of the distance.

The formula is:

F = (GMm)/d^2

F being the force between the two masses, M and m being the two masses, G (6.67x10^-11) being the gravitational constant and d being the distance.

This thought to be constant throughout the universe but I recently heard of some research suggesting otherwise...


----------



## elgar's ghost

Why were round shields favoured by soldiers when it seems to me that rectangular or triangular shapes offered better protection?


----------



## Philip

Chrythes said:


> Each line of the sphere holds information? Does that sphere mean that we can essentially manipulate more information? Does it work like a "storage device"?
> And does gravity exist everywhere? Does an object far from us feel earth's gravitational force?


I don't know what is your background in linear algebra or digital systems, but here's an explanation from:

_*An introduction to quantum computing*_ by Kaye, Phillip ; Laflamme, Raymond ; Mosca, Michele ;
Oxford ; New York : Oxford University Press, 2007

P. 41
[...]


----------



## Lunasong

I would like an explanation on whether the times of moonrise and moonset are connected to the phases of the moon or whether they are on their own cycle. I've never seen this satisfactorily answered and it seems to me to be a basic question.


----------



## Philip

emiellucifuge said:


> F being the force between the two masses, M and m being the two masses, G (6.67x10^-11) being the gravitational constant and d being the distance.
> 
> This thought to be constant throughout the universe but I recently heard of some research suggesting otherwise...


I'm no expert on the subject, and i'm not sure what "research" you are referring to... but Newton's classical model of gravity was generalized by Einstein's general relativity, which describes how space is warped by massive objects, therefore rendering gravity as a virtual force. Warped space leads to gravitational waves, and he who says waves, says particles, yielding the postulate of gravitons, ie. gravity particles.

I'm sure aleazk or mmsbls could elaborate on that.


----------



## emiellucifuge

Hi Phillip, thanks - Ive studied General relativity in school, but its not what I was referring to:

I managed to find the article below which describes a variation in the fine structure constant.
http://www.sciencedaily.com/releases/2010/09/100909004112.htm


----------



## Kopachris

Lunasong said:


> I would like an explanation on whether the times of moonrise and moonset are connected to the phases of the moon or whether they are on their own cycle. I've never seen this satisfactorily answered and it seems to me to be a basic question.


The phases of the moon are based on the moon's location relative to the earth and sun, and the time of moonrise/set is based on the moon's location relative to the earth. Yes, they are connected in that they're based on the same thing, and follow the same cycle. A new moon will always rise and set at a similar time to the sun, a quarter moon will always rise/set about six hours from the sun, and a full moon will always rise and set about twelve hours from the sun.


----------



## Philip

emiellucifuge said:


> Hi Phillip, thanks - Ive studied General relativity in school,


Ah very good then


----------



## emiellucifuge

Philip said:


> Ah very good then


Only superficially mind you! Still, Id love if someone could make a little more sense out of that article for me.


----------



## Lunasong

Kopachris said:


> The phases of the moon are based on the moon's location relative to the earth and sun, and the time of moonrise/set is based on the moon's location relative to the earth. Yes, they are connected in that they're based on the same thing, and follow the same cycle. A new moon will always rise and set at a similar time to the sun, a quarter moon will always rise/set about six hours from the sun, and a full moon will always rise and set about twelve hours from the sun.


So above the tropics, the moon will have seasonality (up longer in the summer, shorter in the winter) like the sun?


----------



## Cnote11




----------



## Kopachris

Lunasong said:


> So above the tropics, the moon will have seasonality (up longer in the summer, shorter in the winter) like the sun?


Dammit. I forgot about that. Yes, but that has nothing to do with the other stuff. So you've got the monthly cycle relative to the sun and the yearly cycle based on the tilt of the earth. So moonrise/set is based on the time of the lunar month, time within the year, and your latitude. (And any geographical features that might mean a higher or lower horizon, of course.)


----------



## Fsharpmajor

Cnote11 said:


>


The quote is abject nonsense, and I suspect you're being mischievous here, Cnote, because it isn't actually a rational argument, and I think you know that.

But anyway, the short answer is that humans did not evolve from monkeys. Our closest extant relative is probably the chimpanzee, which is not actually a monkey. We didn't arise from anything particularly resembling a modern-day chimp, either. Chimpanzees and us had a common, ape-like ancestor, which doesn't exist any more, but from cladistic (evolutionary family tree) analysis, we can be close to certain that it existed, although we don't know what it actually looked like.

The long answer involves comparison of DNA sequences amongst the extant primate species, which pretty much confirms what the earlier studies, based mainly on morphological characteristics, suggested.

As for Darwin, he wrote books, and has living descendants, so I think it's reasonably safe to say that he existed.


----------



## mmsbls

emiellucifuge said:


> Only superficially mind you! Still, Id love if someone could make a little more sense out of that article for me.


I think things still have not been resolved on this issue. An original problem was that studies have used two different telescopes - the Very Large Telescope (VLT) in Chile and the Keck telescope. The VLT showed an increase in the fine structure constant (alpha) with increasing distance from earth, but the Keck showed a decrease. The more recent paper (2 months ago) combines the two sets of results and tries to fit the variation with a dipole model. Apparently the data fits this model (i.e. spatial variation of alpha) better than a constant alpha with a 4 sigma confidence level.

There will certainly be several more attempts to measure alpha as a function of both space and time. I don't think physicists are sold on the variation even though there have been many theoretical papers suggesting variation in the past. Interestingly, while alpha may be constant as a function of space and time, we know it varies as a function of energy (i.e. alpha and the electroweak force increases for more energetic interactions).


----------



## Cnote11

No, no, of course I know these things Fsharp! I was merely posting it because it reminded me of the discussion on the Creationists and their mathematics earlier in this thread. That was this thread, wasn't it? Perhaps I have them mixed up. :lol:


----------



## Fsharpmajor

Cnote11 said:


> No, no, of course I know these things Fsharp! I was merely posting it because it reminded me of the discussion on the Creationists and their mathematics earlier in this thread. That was this thread, wasn't it? Perhaps I have them mixed up. :lol:


Knowing you, I didn't think you were being serious. I suppose my question is whether the quote was actually intended to be taken seriously, or was meant to be satirical.


----------



## Cnote11

I'm honestly leaning towards satirical... for the hope of the world.


----------



## Fsharpmajor

Cnote11 said:


> I'm honestly leaning towards satirical... for the hope of the world.


The creationists get themselves trapped in circular reasoning when they say that six thousand years isn't long enough for evolution to have resulted in Homo sapiens.

They're not wrong about that, of course. It isn't.


----------



## Cnote11

They are right about _one thing_. Humans indeed did _not_ evolve from monkeys.


----------



## aleazk

@Chrythes, you seem very interested in physics, why you don't study it?, I mean, as a hobby. Many of your questions, like that about the qubit, requires a very clear knowledge of the basic principles of quantum mechanics (state of the system as a vector in a Hilbert space, basis states and the measurement process and the outcome probabilities, etc). If you know some linear algebra, you could read the first chapters of J.J.Sakurai's book, "Modern Quantum Mechanics", which is a standard book used for teaching QM. The good thing is that starts with the basic principles, and after reading those first chapters, you can get an idea of what QM is about.


----------



## Stargazer

I have a question for all of you physics people! I'm really interested in finding out the theoretical upper limit for telescope resolution given current technology. 

If I understand correctly the theoretical upper limit for angular resolution of a single telescope is based simply on the diameter of the aperture, and the wavelength of light you are trying to observe. However, how is angular resolution calculated for a telescopic array, and what are the potential benefits and limitations to such a system? What sort of an array system would you need to read, say, a newspaper laying on the ground on Mars if you were here on Earth?


----------



## Chrythes

@Philip - thank you for trying to explain it, but I guess my knowledge is insufficient to fundamentally understand that concept. 
So I guess I'll have a look at the book you suggested when I'll have the time, aleazk. And yes, I'm quite interested in Physics. My cousin is studying it so it's always interesting to discuss it with him. I think it's really about time I study it more in depth!

And about the Tesseract - 







Would the lines of the outer cube that connect with the inner cube be parallel to each other in the 4th dimension? 
I think I'm getting too far too fast.


----------



## Kopachris

Chrythes said:


> And about the Tesseract -
> View attachment 4606
> 
> Would the lines of the outer cube that connect with the inner cube be parallel to each other in the 4th dimension?


Short answer: yes. Long answer: Yes, but not necessarily for other four-dimensional polytopes, and the "cube within a cube" thing isn't really a good way of imagining a tesseract. It might be easier and more accurate to imagine the object in our space by imagining time as a spacial dimension.


----------



## Philip

Chrythes said:


> @Philip - thank you for trying to explain it, but I guess my knowledge is insufficient to fundamentally understand that concept.


You might want to read this page: http://www.cs.rice.edu/~taha/teaching/05F/210/news/2005_09_16.htm

It will give you the gist of it, but first and foremost, i would familiarize myself with the binary system. It's really easy, especially since we already know the decimal system. Then i would review my linear algebra, ie. vectors, matrices, etc. Finally, quantum physics. Quantum physics, if you don't go into the mechanics, is actually pretty simple.

Once you know what is a bit, a vector, and a wave function; you'll be on your way to grasping the concept of qubits.



Chrythes said:


> And about the Tesseract -
> Would the lines of the outer cube that connect with the inner cube be parallel to each other in the 4th dimension?


What you posted is only _one_ of the many projections of a tesseract in "3D" space (your screen is 2D, but your brain see's it as 3D). You can easily find another projection in which the opposing vertices are all parallel:










In the same way, you can find a 2D projection of a cube in which the vertices are _not_ all parallel (when the GIF pauses):


----------



## Fsharpmajor

A recurrent argument made by climate change sceptics is that the planet Mars is warming. The implication is that solar activity, not human activity, is responsible for global warming.

Is there any actual evidence that the climate of Mars is changing one way or the other?--either cooling, or warming? We have very little instrumentation there, and what we do have doesn't seem to be designed to answer this question in the first place.


----------



## Polednice

This is no doubt a verbose and uninformed wording of a basic, old question, but I'm unfamiliar with popular phrasings, so let me put it like this. Our subjective experience of any object's colour is determined by the amount of light shone upon it. So, if you imagine an object in front of you with a uniformly coloured surface, if you were to shine a bright light on half, and cover the other half in shadow, the object would appear as though it comprised two colours. So, is colour a completely subjective attribute of conscious experience, or is there a way of determining outside of human perception the "true" colour of an object? By that, I suppose it would mean determining the wavelength of light an object reflects? Is that possible and/or simple? Would it give a single wavelength (e.g. _this_ particular shade of scarlet red) or something else?


----------



## Philip

Polednice said:


> and cover the other half in shadow, the object would appear as though it comprised two colours.


Black is not technically a colour, it's the absence of colour.



Polednice said:


> By that, I suppose it would mean determining the wavelength of light an object reflects? Is that *possible* and/or *simple*? Would it give a single wavelength (e.g. _this_ particular shade of scarlet red) or something else?


Yes and Yes. If the colour is perfect, Fourier analysis will show a single peak at the sampled wavelength.


----------



## Polednice

Philip said:


> Yes and Yes. If the colour is perfect, Fourier analysis will show a single peak at the sampled wavelength.


What do you mean by "perfect"?


----------



## Dodecaplex

Can someone solve this?


----------



## Philip

Hmm i think i see your question now: Is there colour in the universe, or does it happen only in the brain?

The physical model of the universe does not need colour (like a digital camera would), only electromagnetic waves of various wavelengths (as seen by antennas). A slice of that spectrum is visible to us in the form of colour, and it just so happens that our sun emits most of its electromagnetic energy in the colour spectrum... perhaps not a coincidence, from an evolutionary stand point, if the eye is most sensitive to these wavelengths.

So yes, colour is physiological/neurological, whatever you want to call it.



Polednice said:


> What do you mean by "perfect"?


All emitted photons are at the same wavelength.


----------



## Philip

Dodecaplex said:


> Can someone solve this?


It can be shown by induction, but i'm not sure if i understand the second part of the problem.

Edit: Actually, it may be easier to just show that the series converges; it's been a while...


----------



## ComposerOfAvantGarde

Cnote11 said:


> They are right about _one thing_. Humans indeed did _not_ evolve from monkeys.


They evolved from Pikaia.

And now for my not so scientific question, but question that needs a scientific answer: why does my foot taste like wasabi?


----------



## Lenfer

*TEA*​









or










_Coffee?_​


----------



## ComposerOfAvantGarde

Lenfer said:


> *TEA*​
> 
> 
> 
> 
> 
> 
> 
> 
> 
> or
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> _Coffee?_​


I would usually say...

_COFFEECOFFEECOFFEECOFFEECOFFEECOFFEECOFFEECOFFEECOFFEECOFFEECOFFEECOFFEECOFFEECOFFEECOFFEECOFFEEYESYESYESYESYESYESYESYESYESYESYESYESYESYESYESYESYESYESYESYESYESCOFFEECOFFEECOFFEECOFFEECOFFEECOFFEECOFFEECOFFEECOFFEECOFFEECOFFEECOFFEECOFFEECOFFEECOFFEECOFFEEYESYESYESYESYESYESYESYESYESYESYESYESYESYESYESYESYESYESYESYESYES_COFFEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!


----------



## Lenfer

I am also a coffee person but I have a craving for a nice cup of *Earl Grey* but our tea caddy is empty!!


----------



## ComposerOfAvantGarde

Lenfer said:


> I am also a coffee person but I have a craving for a nice cup of *Earl Grey* but our tea caddy is empty!!


Tea is boring.


----------



## Lenfer

violadude said:


> First question: Why does having mint in your mouth make water colder, sometimes to the point where it's so cold it hurts?


Maybe the water releases something in the mint that stimulates the tongue which your brain interprets as a cool sensation? I don't a hot beverage would cause a cold feeling although I haven't tested it. Being mintless I'm relying on you to test this out *Violadude*.


----------



## peeyaj

Honestly, why mmsbls is so smart? 




( I remember mmslbs having discussion with Chris in TC Atheist thread, and he is so erudite that he amazes me)


----------



## hawk

The sun just disappeared~gone out of existence! No big explosion or anything that would cause the earth to be showered with the fallout.....

How long does life on earth last? What do we all die from?


----------



## ComposerOfAvantGarde

Nobody has answered my question.


----------



## Kopachris

hawk said:


> The sun just disappeared~gone out of existence! No big explosion or anything that would cause the earth to be showered with the fallout.....
> 
> How long does life on earth last? What do we all die from?


Life on earth lasts another several millenia, at least. Bacteria and fungi will live off of all the organic matter that died because there's no sun, and animals will adapt to survive off of those fungi). Most of us will die either of suicide, insanity, or hunger--90% of the human population gone within a year. Plants die because (duh) there's no sun. Some animals die because there's no plants, and other animals die because there's no other animals.

Oh, wait. I forgot that the earth would suffer massive cooling. We all die of hypothermia within a month, methinks, except for a few extremophiles.

But that wasn't a scientific answer because it can't be proven through experimentation and observation.


----------



## Philip

hawk said:


> The sun just disappeared~gone out of existence! No big explosion or anything that would cause the earth to be showered with the fallout.....
> 
> How long does life on earth last? What do we all die from?


It would be amazing. For about 8 minutes after the sun's disappearance, the earth would still receive light from it and continue on its orbit. Then bam, lights out, the gravitational wave hits us and off we go in a straight line, out of the solar system. Earth slowly becomes a block of ice and snow, on the surface at least. Life may survive at the bottom of the oceans, since our planet produces its own heat, perhaps for millions or even billions of years.


----------



## Fsharpmajor

Philip said:


> It would be amazing. For about 8 minutes after the sun's disappearance, the earth would still receive light from it and continue on its orbit. Then bam, lights out, the gravitational wave hits us and off we go in a straight line, out of the solar system. Earth slowly becomes a block of ice and snow, on the surface at least. Life may survive at the bottom of the oceans, since our planet produces its own heat, perhaps for millions or even billions of years.


There are populations of bacteria which live deep in the Earth's crust. Their existence is effectively uncoupled from surface life (they are chemotrophic, and don't require oxygen), and they would still survive when photosynthesis stops on the surface. They would only die when the radioactive decay which keeps the interior of the Earth warm finally stops.

The same goes for chemotrophic bacteria living in hydrothermal vents on the ocean floor.

("Bacteria" is a bit of a misnomer, because some of them have more ancient origins than true bacteria, and so are no longer classified as such).


----------



## Cnote11

ComposerOfAvantGarde said:


> Tea is boring.


Ugh...


----------



## Polednice

What selective pressure would have led the small ancestors of blue whales to evolve into such gigantic animals?


----------



## emiellucifuge

Larger animals are more energetically efficient. The relative metabolic rate decreases with size meaning less energy needs to be consumed per gram of tissue.

Reducing the surface-area to volume ratio reduces relative heat loss.

Remember, that for marine animals size increases are relatively easy and can occur in relatively few generations.


----------



## Polednice

emiellucifuge said:


> Larger animals are more energetically efficient. The relative metabolic rate decreases with size meaning less energy needs to be consumed per gram of tissue.
> 
> Reducing the surface-area to volume ratio reduces relative heat loss.
> 
> Remember, that for marine animals size increases are relatively easy and can occur in relatively few generations.


Thanks! That's very informative.


----------



## emiellucifuge

No problem, pity that i could only give you some very general things. Your question provoked me to do some research, but I couldnt find anything relating specifically...


----------



## mmsbls

emiellucifuge said:


> No problem, pity that i could only give you some very general things. Your question provoked me to do some research, but I couldnt find anything relating specifically...


Here is a fascinating book that discusses the evolution of body size.


----------



## Philip

Polednice's colour question got me thinking... and i've come up with the following question:

_Why does mixing blue and yellow make green... from a physical and physiological perspective?_


----------



## Polednice

Can anybody tell me what the significance and/or consequences of this are?



> Researchers claim quantum breakthrough: Researchers say they have designed a tiny crystal that acts like a quantum computer so powerful it would take a computer the size of the known universe to match it.
> 
> Details of the crystal, which is made up of just 300 atoms, are published today in the journal Nature.


Is this a first? A leap forward? Or are people already doing stuff like this?


----------



## ComposerOfAvantGarde

Still no one has answered my question!!!!!


----------



## mmsbls

Polednice said:


> Can anybody tell me what the significance and/or consequences of this are?
> 
> Is this a first? A leap forward? Or are people already doing stuff like this?


Quantum Computing is more than a bit complicated. A normal computer can do billions of operations per second and each operation acts on 2 numbers. A program is setup to do operations to solve a particular problem such as add two large numbers. To solve that, the computer breaks the problem into small parts and very quickly computes each part, but each computation is done in series (in other words one computation after the other).

A quantum computer can do operations in parallel (in other words many operations at the same time). Bits in a regular computer are either 1 or 0 and are fixed. In a quantum computer qubits are in a superposition of states. In other words a qubit will be, for example, 50% 1 and 50% 0. It will be in *both* states at the same time.

To see the potential difference between normal and quantum computing, imagine you have two bits or two qubits. In the normal computer you can set the bits to each of 4 states:
1 1
1 0
0 1
0 0
You can run a program on each state, and to run the program on all four states, you have to run the program 4 times in sequence. In the quantum computer you can set both your qubits to 50% 1 and 50% 0. There is then a probability that the qubits are in each of the 4 states above. You run the program on all 4 states at the same time rather than running the program in series 4 times. The computer allows you to get answers for each configuration "all at once".

Having a quantum computer with 300 qubits is, in some sense, equivalent to a regular computer with 2^300 bits, which would require a physical computer larger than the known universe, or to running a normal computer for vast periods of time (many times longer than our universe has existed).

Researchers have been working on quantum computers for awhile, but the work by Biercuk et. al. is a huge breakthrough because previous quantum computing systems have had 16 qubits whereas the Biercuk "computer" has 300 qubits. The 16 qubits systems would be equivalent to roughly 65000 regular bits (not very special).

I personally don't understand exactly how programs are written for quantum computers in order to use the functionality of the qubits.


----------



## Polednice

Yes, that's what I don't quite understand - I follow that there's an immense power involved, but where do you go from 300 _atoms_ to some kind of interface like the computers we use today? Is the collection of atoms analogous to a processor?


----------



## Fsharpmajor

Philip said:


> Polednice's colour question got me thinking... and i've come up with the following question:
> 
> _Why does mixing blue and yellow make green... from a physical and physiological perspective?_


You're supposed to be the one who answers questions like these, not me! But I presume it's because green falls between yellow and blue in the visible spectrum, so your eye or your brain averages out the difference between the two. The visible spectrum is actually a continuous gradient, and the colours (including apparent hybrids such as blue-green) actually consist of wavelengths lying on that gradient. There's no essential difference between yellow, green and blue-green--nor between the so-called primary colours (red, yellow and blue) and the so-called secondary ones (orange, green and purple). The shades of colours we perceive in everyday life are a mixture of wavelengths. When the wavelengths are too mixed for an actual colour of the spectrum to be dominant, we see the colour brown--which does not lie on the spectrum--instead.


----------



## Philip

Fsharpmajor said:


> You're supposed to be the one who answers questions like these, not me! But I presume it's because green falls between yellow and blue in the visible spectrum, so your eye or your brain averages out the difference between the two. The visible spectrum is actually a continuous gradient, and the colours (including apparent hybrids such as blue-green) actually consist of wavelengths lying on that gradient. There's no essential difference between yellow, green and blue-green--nor between the so-called primary colours (red, yellow and blue) and the so-called secondary ones (orange, green and purple). The shades of colours we perceive in everyday life are a mixture of wavelengths. When the wavelengths are too mixed for an actual colour of the spectrum to be dominant, we see the colour brown--which does not lie on the spectrum--instead.


You're on the right track, but there's one problem: if i play both C and E on the piano, why don't i hear something like a D (~average of C and E), instead of separate tones? It's true that there's no real difference between colours apart from their wavelengths, but that only reinforces the problem, since electromagnetic waves should essentially behave like sound waves...


----------



## Polednice

Philip said:


> You're on the right track, but there's one problem: if i play both C and E on the piano, why don't i hear something like a D (~average of C and E), instead of separate tones? It's true that there's no real difference between colours apart from their wavelengths, but that only reinforces the problem, since electromagnetic waves should essentially behave like sound waves...


If you use audio synthesis software to generate two _pure_ frequencies, the brain does average them in the right conditions (high quality and minimal environmental interference). I don't know if they have a minimum and maximum distance, but I know it works for many intervals. I think the problem of playing musical tones is compounded by the overtone series - when you play a C, you're not playing a pure XHz, you've got many overtones of varying strength playing at the same time, reinforcing the sound of the C. The same is true of the E. So, maybe the reason why they don't meld is that they have such conflicting harmonics that it's impossible for your brain to resolve them into an average - instead, you hear them competing, and the sense of consonance and dissonance is dependent on how closely their harmonics overlap (it's much easier to hear a Cmaj chord meld into a single sound than it is a chord cluster). I don't know any of this for sure, I'm just making a semi-educated guess.


----------



## Fsharpmajor

Philip said:


> You're on the right track, but there's one problem: if i play both C and E on the piano, why don't i hear something like a D (~average of C and E), instead of separate tones? It's true that there's no real difference between colours apart from their wavelengths, but that only reinforces the problem, since electromagnetic waves should essentially behave like sound waves...


It's too late at night here for me to try to answer this question, but I promise I'll get back to it tomorrow with some of my thoughts on it.

LATER EDIT: I think Polednice's post addresses the question better than I could.


----------



## Philip

Polednice said:


> If you use audio synthesis software to generate two _pure_ frequencies, the brain does average them.


Can you provide an example?


----------



## Polednice

Philip said:


> Can you provide an example?


I'll have to have a look at this in more detail tomorrow as it's 2am and I have work to do before bed.  However, an initial glance at some notes I scribbled ages ago suggests that it only works for two tones that are less than 30Hz apart, and each lower than 1000Hz, so the effect is rather limited - why it doesn't work outside that range, I don't know.

I had a brief glance at the Wiki article on the cocktail party effect, though, which is about being able to focus on a single stimulus at the expense of others. Perhaps - again, this is pure speculation - the reason why sound is different is that there are distinct sources of sound in different locations that we can select between to focus on. When you mix colours together, in order to see a conglomeration of colours rather than a single average, your eyesight would have to be sufficiently powerful to distinguish between individual sources of reflected light, which I imagine is extremely microscopic, and therefore human eyes lack the ability to do it, instead resolving the stimulus into an average colour. Perhaps the limits and differences between auditory and visual stimuli, then, are dependent on the varying resolutions to which our eyes and ears are capable of functioning.


----------



## ComposerOfAvantGarde

ComposerOfAvantGarde said:


> Still no one has answered my question!!!!!


I now realise my question was stupid. Don't worry about it.


----------



## mmsbls

Polednice said:


> Yes, that's what I don't quite understand - I follow that there's an immense power involved, but where do you go from 300 _atoms_ to some kind of interface like the computers we use today? Is the collection of atoms analogous to a processor?


The best answer I can give you (because of my ignorance) is that the 300 atoms would interact with fields (electromagnetic) generated by other parts of the computer to create the solution. The solution would be read out of the 300 atoms by determining their individual state in a manner somewhat similar to conventional computers reads the output of their registers.

I understand that normal computers have programs, processors, and data, and I understand how they interact. I can't describe properly what the program, data, and processor of the quantum computer are and how they interact.


----------



## mmsbls

Philip said:


> _Why does mixing blue and yellow make green... from a physical and physiological perspective?_


People have compared mixing colors to mixing sounds, but the two situations are different at least in terms of the above question.

When we say mixing blue and yellow make green, we really mean mixing things that reflect blue and yellow light - not directly mixing blue and yellow light. The conventional problem refers to paints. Blue paint doesn't create blue light but rather it primarily absorbs visible light in the red, orange, and yellow parts of the spectrum. What remains is mostly blue with some violet and green (and very little yellow, orange, and red). Yellow paint absorbs light primarily in the violet and blue parts of the spectrum (and some orange and red). When you mix blue paint and yellow paint, the molecules will absorb highly in all areas but green. When white light or sunlight is directed at a mixture of blue and yellow paint, the light that is reflected is primarily green so we see green. If you shined red light on a mixture of blue and yellow paint, the object would appear black since almost no light would be reflected.

With sounds you are talking about creating specific sound wave frequencies rather than filtering out frequencies from "white noise" (i.e. all frequencies). You could use frequency filters on white noise to create a similar effect to what we find in colors. There would still be a difference because of the physiology of color and sound. When we see many frequencies in the red color band, we call them red even though they look somewhat different. Mixtures of reds still seem red to us and look fine. We'd have to filter the sounds very finely to make sure that only those frequencies close enough to say middle C were heard; otherwise, we'd hear great dissonance rather than a pitch. There is no color analog to dissonance.


----------



## Philip

mmsbls said:


> People have compared mixing colors to mixing sounds, but the two situations are different at least in terms of the above question.
> 
> When we say mixing blue and yellow make green, we really mean mixing things that reflect blue and yellow light - not directly mixing blue and yellow light. The conventional problem refers to paints. Blue paint doesn't create blue light but rather it primarily absorbs visible light in the red, orange, and yellow parts of the spectrum. What remains is mostly blue with some violet and green (and very little yellow, orange, and red). Yellow paint absorbs light primarily in the violet and blue parts of the spectrum (and some orange and red). When you mix blue paint and yellow paint, the molecules will absorb highly in all areas but green. When white light or sunlight is directed at a mixture of blue and yellow paint, the light that is reflected is primarily green so we see green. If you shined red light on a mixture of blue and yellow paint, the object would appear black since almost no light would be reflected.
> 
> With sounds you are talking about creating specific sound wave frequencies rather than filtering out frequencies from "white noise" (i.e. all frequencies). You could use frequency filters on white noise to create a similar effect to what we find in colors. There would still be a difference because of the physiology of color and sound. When we see many frequencies in the red color band, we call them red even though they look somewhat different. Mixtures of reds still seem red to us and look fine. We'd have to filter the sounds very finely to make sure that only those frequencies close enough to say middle C were heard; otherwise, we'd hear great dissonance rather than a pitch. There is no color analog to dissonance.


However... if you take an LED display, for example, the RGB spectra are pretty narrow for each Red, Green and Blue colour.










Therefore, to get yellow you mix red and blue, and the majority of the colour emitted is red and blue, not yellow (as per your reflection example). Essentially, yellow's spectrum would look like picture above, without the green peak; as opposed to what a dedicated yellow LED would emit, which is a true yellow peak.

Edit: In other words, mixing monochromatic colours still produces new colours, so the argument of subband absorption/reflection in objects is somewhat irrelevant here.

Give me a little time to formulate my answer to the question...


----------



## Argus

If I were to set up a computer to play a percussive (i.e. not continuous) tone (say, for example, middle C = 261.62 Hz) at a steadily increasing tempo, what pitch will be heard when the stream of tones are played faster than 20 times per second (20 Hz or the lower pitch threshold for the listener)?

Will I hear both the middle C as well as a rising bass tone? And what would happen if the middle C tone was played faster than 20,000 Hz?


----------



## aleazk

well, if you represent each colour like a sinusoidal wave, you can add them:









the result is another sinusoidal wave, but with frequency (f1+f2)/2. A "yellow wave" is simply a sinusoidal wave with a frequency of roughly of 550 THz. For Red, 480 THz. For Blue, 670 THz. So the frequency of the resulting wave, when we "add red and blue", is (480+670)/2=575, which is a yellow wave indeed. On the other hand, there is an oscillation (the cosine term) in the amplitude of the resulting wave. The frequency of this oscillation is (f1-f2)/2. For this case, (480-670)/2=-95 (of course, simply 95 Thz, because cos (-x)=cos (x)). 95 Thz is a very fast oscillation, so we perceive the yellow as static. Was this the question?
You can't do this with sound, because, unlike the light case, there's not a bijective relation note-frequency, which exists in the case of light, colour-frequency. I mean, of course you can add sound waves, but you can't make the same interpretation in terms of notes as you make in terms of colour for the case of light.


----------



## Philip

aleazk said:


> well, if you represent each colour like a sinusoidal wave, you can add them:
> 
> View attachment 4800
> 
> 
> the result is another sinusoidal wave, but with frequency (f1+f2)/2. A "yellow wave" is simply a sinusoidal wave with a frequency of roughly of 550 THz. For Red, 480 THz. For Blue, 670 THz. So the frequency of the resulting wave, when we "add red and blue", is (480+670)/2=575, which is a yellow wave indeed. On the other hand, there is an oscillation (the cosine term) in the amplitude of the resulting wave. The frequency of this oscillation is (f1-f2)/2. For this case, (480-670)/2=-95 (of course, simply 95 Thz, because cos (-x)=cos (x)). 95 Thz is a very fast oscillation, so we perceive the yellow as static. Was this the question?
> You can't do this with sound, because, unlike the light case, there's not a bijective relation note-frequency, which exists in the case of light, colour-frequency. I mean, of course you can add sound waves, but you can't make the same interpretation in terms of notes as you make in terms of colour for the case of light.


You stole my answer!!


----------



## Philip

That's right folks. When you add two sinusoidal waves together, you get a "beat". The beat occurs at the difference of the two frequencies. This is also true for sound signals... when you tune two guitar strings to the same pitch, there will be an audible beat if they are very close in pitch. That is, if you're tuning from a reference of A 440Hz, but you hear a beat every second (of time), you have about 1Hz error between the two strings. This is what it looks like:










The resulting (beating) wave has a frequency of the average of the two original waves. Effectively, in my initial question, yellow and blue have an average frequency of green, which will itself beat at a frequency in the range of the infrared. This has the effect of exciting the M (green) cones cells within the retina of the eye. There's three types of cone cells: short (S), medium (M), long (L), for blue, green, and red, respectively (and approximately).

The beat (wobble) is continuous and gradual, ie. sinusoidal, but this also works for ON/OFF displays. If you have a microcontroller designed for only one single 7-segment display output... you can multiplex several of them and simply alternate the ON/OFF signal of each one at a very high frequency (typically the clock speed of the controller), which gives the illusion that all of them are on at the same time.


----------



## Mesa

Argus said:


> If I were to set up a computer to play a percussive (i.e. not continuous) tone (say, for example, middle C = 261.62 Hz) at a steadily increasing tempo, what pitch will be heard when the stream of tones are played faster than 20 times per second (20 Hz or the lower pitch threshold for the listener)?
> 
> Will I hear both the middle C as well as a rising bass tone? And what would happen if the middle C tone was played faster than 20,000 Hz?


Something like this, at 50 seconds (not a steady pulse, i know but at that speed, similar principle and the pattern *should* effect the harmonics):





And if you have bulletproof ears:





To answer the question, the tone above 20Hz at which the pulse becomes an audible oscillator tends to dominate in most circumstances. However, depending on how your tone generator is set up, it may ignore signals coming too fast and begin to play the original tone again (say, a whole note on every 4th instead of a 16th or 32nd with a release curve that relays over to the next signal).

Also, above 20KHz, you probably won't hear anything. On a computer you might, but this could be digital audio artefacts, sampling errors etc. The standard adult hearing range is up to about 17-21K 

Finally, a chance to once again try to justify wasting five years studying music technology.


----------



## Ukko

When it rains frogs... are the frogs edible?


----------



## Philip

Argus said:


> If I were to set up a computer to play a percussive (i.e. not continuous) tone (say, for example, middle C = 261.62 Hz) at a steadily increasing tempo, what pitch will be heard when the stream of tones are played faster than 20 times per second (20 Hz or the lower pitch threshold for the listener)?
> 
> Will I hear both the middle C as well as a rising bass tone? And what would happen if the middle C tone was played faster than 20,000 Hz?


Hold on, i'll try to find a computer with MATLAB and produce some sound samples... but, to be clear, you want a wobbling middle C that increasingly rises in wobble frequency, and you want to know the pitches you hear at any moment (as well as the actual frequency content)?


----------



## Kopachris

Hilltroll72 said:


> When it rains frogs... are the frogs edible?


Usually yes. Don't eat anything that's fallen from the sky that's already dead if you haven't killed it yourself.


----------



## ComposerOfAvantGarde

What is an up quark made out of?


----------



## Mesa

Jesus's love.


----------



## Chrythes

I'm trying to get my mind around a few simple psychophysiological laws. The main 3 are:
1) Weber's - who said that for us to feel the difference between two stimuli of the same quality there's always a constant difference (we can perceive the difference between 105g and 100g because of the 5g, so to perceive the difference between 200 and the next stimuli the minimum is 10g, so we can perceive the difference between 210g and 200g).
2) The second is Fechner's (here I'm a bit unsure) - f light A is twice as brighter than light B, then our perception of the light would be log 2 brighter than light B. So does it mean that to perceive a stimulus on the same level as before, we need to intensify it more than we did the previous time? 
3) Stiven's Law - which is, as far as I understand, basically says that Fechner's is right, but not always. ..."but while Fechner postulated that the perceived intensity is always related logarithmically to the physical intensity, Steven's law says the magnitude of the perceived intensity is related to the magnitude of the physical intensity raised to some power". What do they mean by "raised to some power"? 
Does it mean that if we start from a certain brightness (B) and intensify it twice (to brightness A) we won't actually perceive it, as Fechner's said, log2 brighter than B? 

Sorry if it seems a bit messy and not very clear.


----------



## mmsbls

ComposerOfAvantGarde said:


> What is an up quark made out of?


Quarks are believed to be fundamental particles. In other words they are not composed of more fundamental things. They have specific properties which distinguish them from other fundamental particles.

In the Standard Model of physics, quarks are described as a field which interacts with other fields. An example of a field would be the electromagnetic field. Quarks have charge (like electrons) so electric and magnetic fields create a force which pushes or pulls quarks. Another field is the Higgs (which physicists are currently searching for at the Large Hadron Collider in Europe). The Higgs field, assuming it does exist, interacts with all quarks to give them mass. The up quark field is somewhat different from other quark fields (and other particle fields), and those differences give rise to the up quark's unique set of properties.

In the new set of theories, called String Theory, all fundamental particles are described as strings that vibrate. They are 1-dimensional objects (having length but no width or height). The Standard Model views particles as having 0 dimensions (i.e. they are point particles with no volume). The vibrations are exceedingly complex, but those vibrations give rise to all the properties of the string (or particle). Different "fundamental particles" are really the same type of thing (i.e. a vibrating string), but the different ways the string vibrates yield different particles. The vibrating strings interact with the various fields (electromagnetic, Higgs, etc.) to produce all the interactions and properties we see.

That's about the best physicists can do at the moment.


----------



## aleazk

mmsbls said:


> Quarks are believed to be fundamental particles. In other words they are not composed of more fundamental things. They have specific properties which distinguish them from other fundamental particles.
> 
> In the Standard Model of physics, quarks are described as a field which interacts with other fields. An example of a field would be the electromagnetic field. Quarks have charge (like electrons) so electric and magnetic fields create a force which pushes or pulls quarks. Another field is the Higgs (which physicists are currently searching for at the Large Hadron Collider in Europe). The Higgs field, assuming it does exist, interacts with all quarks to give them mass. The up quark field is somewhat different from other quark fields (and other particle fields), and those differences give rise to the up quark's unique set of properties.
> 
> In the new set of theories, called String Theory, all fundamental particles are described as strings that vibrate. They are 1-dimensional objects (having length but no width or height). The Standard Model views particles as having 0 dimensions (i.e. they are point particles with no volume). The vibrations are exceedingly complex, but those vibrations give rise to all the properties of the string (or particle). Different "fundamental particles" are really the same type of thing (i.e. a vibrating string), but the different ways the string vibrates yield different particles. The vibrating strings interact with the various fields (electromagnetic, Higgs, etc.) to produce all the interactions and properties we see.
> 
> That's about the best physicists can do at the moment.


mm, interesting that an experimental physicist, who has said repeatedly how he trust in the experimental reality, puts so much expectancy in a theory that has not made, so far, one single testable prediction. I'm not against string theory, but I think it has been greatly oversold. The theory is in an embrionary state right now. The theory doesn't even have a satisfactory mathematical formulation. The basic idea on which the particles are 1-dimensional is not new, Dirac proposed something similar 50 years ago. Personally, I think it's the right track to the unification, but a lot of work is necessary yet. Also, I have another problem on how they treat gravity.

(don't take this as some personal attack , it's just that I would expect more skepticism from someone like you , that relation "best physicists-string theory" really **** me off; of course there are first level physicists working on string theory, but they constantly say things like those, "best physicists-string theory", I find it rather pretentious from their part)


----------



## Argus

Mesa said:


> Something like this, at 50 seconds (not a steady pulse, i know but at that speed, similar principle and the pattern *should* effect the harmonics):
> 
> To answer the question, the tone above 20Hz at which the pulse becomes an audible oscillator tends to dominate in most circumstances. However, depending on how your tone generator is set up, it may ignore signals coming too fast and begin to play the original tone again (say, a whole note on every 4th instead of a 16th or 32nd with a release curve that relays over to the next signal).
> 
> Also, above 20KHz, you probably won't hear anything. On a computer you might, but this could be digital audio artefacts, sampling errors etc. The standard adult hearing range is up to about 17-21K
> 
> Finally, a chance to once again try to justify wasting five years studying music technology.


So when the middle C is played over 20,000 time per second will nothing be audible, or will the rising secondary tone still be audible? Or will the middle C be perceived as a continuous tone and not discreet individual notes?

If you don't mind me asking, where did you study music tech? I've had enough of the 9-5 and I'm thinking of going to Huddersfield to study one of their music tech courses. Mainly, I want to learn how to use DAW's, audio synthesis environments, that kind of thing because I am useless with computers at the minute which is a hindrance to my production of bangin' techno tunes.



Philip said:


> Hold on, i'll try to find a computer with MATLAB and produce some sound samples... but, to be clear, you want a wobbling middle C that increasingly rises in wobble frequency, and you want to know the pitches you hear at any moment (as well as the actual frequency content)?


The middle C is produced by an electronic tone generator that acts like a steadily increasing (and ultra fast) metronome that produces that fixed pitch instead of a click or bell. And yes, I am interested in what pitches will be perceived (therefore frequency content) will be perceived by the listener as the speed of the 'metronome' increases.


----------



## Philip

Argus said:


> The middle C is produced by an electronic tone generator that acts like a steadily increasing (and ultra fast) metronome that produces that fixed pitch instead of a click or bell. And yes, I am interested in what pitches will be perceived (therefore frequency content) will be perceived by the listener as the speed of the 'metronome' increases.


Which?


----------



## Argus

Philip said:


> Which?


The top one with the equal note duration and periods of silence, although I have no idea what difference it will make when the tones are coming out at ultraspeed.


----------



## Philip

Argus said:


> The top one with the equal note duration and periods of silence, although I have no idea what difference it will make when the tones are coming out at ultraspeed.


The first one is a repeated wave packet, you cannot repeat it faster than the width of the packet because it will overlap and cause aliasing. You can design your own shorter packet, but it will distort the tone even further.

As displayed, the spectrum of a windowed packet looks like this, at 440Hz:










I find the second example much more interesting, its spectrogram (in time) looks like:










It's basically two perfect tones moving apart from each other, the average frequency being 440Hz. You first notice the beat, then it goes into a transient state, which sounds more grating (the pure tone is aliased), and finally, the two tones audibly separate.


----------



## Argus

Philip said:


> The first one is a repeated wave packet, you cannot repeat it faster than the width of the packet because it will overlap and cause aliasing. You can design your own shorter packet, but it will distort the tone even further.
> 
> As displayed, the spectrum of a windowed packet looks like this, at 440Hz:
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> I find the second example much more interesting, its spectrogram (in time) looks like:
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> It's basically two perfect tones moving apart from each other, the average frequency being 440Hz. You first notice the beat, then it goes into a transient state, which sounds more grating (the pure tone is aliased), and finally, the two tones audibly separate.


Any audio clips?


----------



## Chrythes

How do we perceive sounds? How does a mechanical wave becomes an electric one? I remember reading about one theory that explains that we are able to perceive sounds because the neurons vibrate at the same frequency as the wave, but apparently they cannot vibrate more than 100 times per second, so this theory fails to explain how we perceive the high frequency waves.
I guess that the neuron itself doesn't need to move at the frequency of the mechanical wave to actually send it to our brain, so how does it work? Isn't electricity supposed to be of the same frequency as the incoming wave for it not to lose any information? How is that information coded?


----------



## Stargazer

Chrythes said:


> How do we perceive sounds? How does a mechanical wave becomes an electric one? I remember reading about one theory that explains that we are able to perceive sounds because the neurons vibrate at the same frequency as the wave, but apparently they cannot vibrate more than 100 times per second, so this theory fails to explain how we perceive the high frequency waves.
> I guess that the neuron itself doesn't need to move at the frequency of the mechanical wave to actually send it to our brain, so how does it work? Isn't electricity supposed to be of the same frequency as the incoming wave for it not to lose any information? How is that information coded?


Oo I know this one! Here's a link that shows a pretty good image/description of neurons: http://en.wikipedia.org/wiki/Neuron

Basically our nerve cells are designed to respond to different external stimuli. In the case of our ears, vibration. Once it receives said stimuli, it sends out a combination of chemical and electrical signals to the brain, which is what we interpret. In fact, pretty much everything we feel is because of a bunch of chemicals and electrical impulses floating around inside of us lol.


----------



## emiellucifuge

About Chrythe's question:

If I understand this correctly (and in great summation). The sound vibrates the eardrum, the small bones serve to amplify the vibration so that it passes through a fluid. Eventually it reaches another area which contains a membrane. This membrane is made from fibres which are all vibrating at different natural frequencies, and in order. I.e. one end is low frequency and the other end high. When a frequency of say 400Hz reaches this membrane, it causes the fibre vibrating at 400Hz to vibrate with a much greater energy (wave reinforcement). There are tiny hairs along the membrane, and these are touched by the vibrating fibre, sending an electric signal to the brain.

This electric signal is generated thus: When the hair cell is moved, an ion channel is opened mechanically. mostly K+ and Ca+ enter here, and the cell is depolarised (no difference in electrical charge across). This creates a receptor potential which opens another, voltage sensitive, gate. Calcium ions enter the cell through this gate and react to receptors, this causes a neurotransmitter e.g. acetlycholine to be released at the other end of the cell. These diffuse through a channel towards a nerve terminal where they bind to receptors and trigger a chain of electrical potentials along the nerve all the way to the brain.

You can see that the brain can 'know' the frequency of the sound due to the hair cells being located above a specific frequential fibre. Further, as in the eye, there is a threshold below which a signal is not sent - the signal cannot transmit amplitude, instead this is 'calculated' by the number of hairs triggered at the frequency.


----------



## Chrythes

Thank you for your your answers!
@ emiellucifuge - maybe do you know why it's mostly K+ and Ca+?

Another question - why the most abundant element in the universe is Hydrogen? Is it because we are at the evolutionary stage of the universe where hydrogen is dominant, but maybe in the future it could be helium, since it's what stars are mostly made of?
And what is expanding in the universe? Can it be the spaces between atoms?


----------



## Kopachris

Chrythes said:


> Another question - why the most abundant element in the universe is Hydrogen? Is it because we are at the evolutionary stage of the universe where hydrogen is dominant, but maybe in the future it could be helium, since it's what stars are mostly made of?
> And what is expanding in the universe? Can it be the spaces between atoms?


Yes to the first one. No to the second one. Nothing is expanding _in_ the universe, but the universe (i.e. space) itself is expanding. Kind of hard to wrap your head around, I know. See: http://en.wikipedia.org/wiki/Metric_expansion_of_space


----------



## Polednice

Am I wrong to say that Hydrogen is also dominant because it's the simplest element? Or are there projected times when other elements will be dominant?


----------



## emiellucifuge

Certainly the fact Hydrogen is simpy a proton and electron is the reason that it was the 'first' element, all the other elements have resulted from nuclear reactions (also of helium).


----------



## mmsbls

To add a few details to Chrythes's questions:

All elements, including hydrogen, are formed by the strong nuclear force. The electromagnetic force plays a rather crucial role in the amount of each element that exists. The electromagnetic force repels protons making nucleosynthesis (production of nuclei) harder while the strong force binds nuclei making nucloesynthesis "easier". The ratio of hydrogen to helium formed in the early universe (first 20 minutes or so) is roughly 3 to 1 (~74% hydrogen, 26% helium). If the strong nuclear force were slightly weaker, only hydrogen would form and there would have been no helium. If the strong nuclear force were slightly stronger, most hydrogen would have combined to form helium and there would have been very little hydrogen. The ratio of the strong nuclear to electromagnetic forces is a fundamental parameter of our universe, and its value effectively determines the hydrogen/helium ratio. The other important factor is the rate of expansion of the universe. A faster expansion would have produced somewhat less helium.

Helium is formed as stars burn hydrogen, but this only adds a few percent of helium to its primordial abundance. Over time the helium abundance will increase (along with other heavier elements), but hydrogen will always dominate.


----------



## Mesa

Why are the seven times tables (particularly 7x7, 7x6 and 7x8) historically difficult for children and for many adults, even those with a slight natural affinity for maths?

Genuine question. Why are those three, even though i know all of the above empirically and absolutely, are in any situation, still the last remaining offenders of the times table system up to 12x12 that take up to a second to recall?


----------



## ComposerOfAvantGarde

Mesa said:


> Why are the seven times tables (particularly 7x7, 7x6 and 7x8) historically difficult for children and for many adults, even those with a slight natural affinity for maths?
> 
> Genuine question. Why are those three, even though i know all of the above empirically and absolutely, are in any situation, still the last remaining offenders of the times table system up to 12x12 that take up to a second to recall?


What?!?! Since when???? 7x tables were one of the easiest ones I knew! When I was learning my times tables the ones I had most trouble with were the 4, 6 and 8 times tables. Especially the 8s.


----------



## mmsbls

Mesa said:


> Why are the seven times tables (particularly 7x7, 7x6 and 7x8) historically difficult for children and for many adults, even those with a slight natural affinity for maths?
> 
> Genuine question. Why are those three, even though i know all of the above empirically and absolutely, are in any situation, still the last remaining offenders of the times table system up to 12x12 that take up to a second to recall?


Interesting. I had never heard that certain products were the hardest, but looking online I did find two sites that listed 7X6 and 7X8 as the hardest. I have no idea why.


----------



## ComposerOfAvantGarde

mmsbls said:


> Interesting. I had never heard that certain products were the hardest, but looking online I did find two sites that listed 7X6 and 7X8 as the hardest. I have no idea why.


The numbers 42 and 56 are easy enough to remember.


----------



## Chrythes

Hey, I've got a question (I guess very easy) about how to solve a simple problem in mathematics - 
X2
0,005(50), how do I solve this?

Edit: 0,005 supposed to be near the lower edge of X. And the X is squared


----------



## mmsbls

@Chrythes: Since there's a variable (x) in the problem and you want us to solve it, I assume it's an equation. But there's no "=" sign so it's not an equation as written. Without the "=" sign it's just a term and can't be solved for X.

Also the subscript(?), 0.005, and the parentheses around 50 are not defined. We don't know what to do with them. It's possible the parentheses indicate multiplication.


----------



## Philip

Chrythes said:


> X2
> 0,005(50), how do I solve this?


You just broke my brain.


----------



## Chrythes

:lol:
Sorry, I knew the way I presented it might be a bit confusing.

Anyway, I actually found a table with the answers, depending on the n and alpha that I have. 
The question was about this - 
http://i46.tinypic.com/r0r2fd.jpg

The answer is given, but I needed to know how to get to that answer. So apparently there's this thing - 
http://i45.tinypic.com/zsmjxh.jpg

Which helps you find the answer without actually solving the integral.


----------



## Philip

Oh, of course, the _χ_[SUP]2[/SUP] distribution...


----------



## Chrythes

Erm, I've got another question regarding this theme. 
http://i46.tinypic.com/64gqbr.jpg

The problem - there are 61 people (n=61) that had their verbal IQ tested, the standard deviation is 0.4. Can we assume that that the dispersion is different from the older results , if before the standard deviation was 0.5? alpha is 0.01.
Now, how do they know that the a in the hypothesis equals 0.25?

And then they go on to test another hypothesis, where a equals 0.05.
http://i48.tinypic.com/28a54zb.jpg

I think the second might be a mistake, and a should be equal 0.5, but I'm not sure (their X distribution is wrong, it should be 0.995, not 0.99).


----------



## Philip

To be honest, i don't think anyone cares (about stats). If you want a tutor, i'm not it. 

Anyway, the 0.25 value comes from the square of the standard deviation, ie. the variance: 0.5[SUP]2[/SUP]=0.25

The 'significance' values (eg. 0.005; 0.995, etc.) are often arbitrary, and/or will be stated/defined in the statement of the problem.


----------



## Chrythes

I know, I shamelessly invaded this thread with my own uninteresting problems. 
To be honest I was hoping either you or mmlsbs would answer, and you did, so my part here is done, as the last problem was the only thing I failed to understand. At least for now. Thank you.

I won't bother this thread with stats or anything similar again.


----------



## Chrythes

Are there any theories that assume the existence of even smaller particles than quarks (apart from string theory)?
I know they are supposed to be the smallest unit of matter, but is it possible that we just don't have the right equipment to measure even smaller particles yet?

I've just read a very short article on wiki about the proton spin puzzle.http://en.wikipedia.org/wiki/Nucleon_spin_structure It says that "the gluon spin components are being measured by many experiments". Do you know if there are any news?

And why do they spin? What are the colors of quarks?

As far as I know they were thought to exist before we could actually measure them. Why were they thought to exist? 
And what effect do other hadrons, fermions and other elementary particles has on us (if it's even a right thing to ask)?


----------



## Kopachris

Why is it so cold these last few days? I had to turn the furnace back on, fer cryin' out loud!


----------



## emiellucifuge

Chrythes said:


> As far as I know they were thought to exist before we could actually measure them. Why were they thought to exist?
> And what effect do other hadrons, fermions and other elementary particles has on us (if it's even a right thing to ask)?


A few scientists thought Hadrons werent fundamental particles, but that they were 'made of' smaller fundamental particles. A whole bunch of these particles were thought up which could together and in combinations explain the properties of hadrons. For example, up quarks have +2/3 charge, and 1/2 spin while down quarks have -1/3 charge and 1/2 spin. A proton has charge of +1 and spin of +1.
You can see that the combination of two ups and a down quark (uud) can explain the properties of a proton.

Quarks were then observed in various labs.


----------



## mmsbls

Chrythes said:


> Are there any theories that assume the existence of even smaller particles than quarks (apart from string theory)?
> I know they are supposed to be the smallest unit of matter, but is it possible that we just don't have the right equipment to measure even smaller particles yet?


In the 1970s some physicists postulated preons, particles that were components of quarks and leptons (electrons, muons, etc.). There were several reasons to suggest preons - mostly to reduce the number of fundamental particles. Preons are not so popular now since there is no experimental evidence of substructure of the presently known fundamental particles (quarks, electrons, muons, etc.). It's certainly possible that at much higher energies we would see substructure (compositness) of quarks and electrons.

Strings (from string theory) are not "smaller" than quarks or electrons. Our present theory, the Standard Model, actually views all fundamental particles as point particles (i.e. they have no dimensions and have zero volume). Strings have 1 dimension. In string theory, all fundamental particles are viewed as vibrations of a fundamental string - they are not smaller or bigger, just different kinds of things.



Chrythes said:


> And why do they spin? What are the colors of quarks?


While particle spin is understood very well in terms of theories that measure and predict particle spin, we don't know what spin really is. The term spin does not really mean that particles actually spin on an axis. We use "spin" because things in the real world that do spin (like the earth) have angular momentum. The properties of angular momentum are well understood, and particles have properties that are very similar so we call one of their properties "spin". No one that I know believes that particles are actually spinning.

Quark colors are "red" "blue" and "green". Quark color is a property, like spin, that does not have an analog in macroscopic things. Quarks don't really have color, but do have a property that has 3 versions which we call "color".



Chrythes said:


> As far as I know they were thought to exist before we could actually measure them. Why were they thought to exist?


There were several reason to believe in the existence of components of protons (i.e. quarks). There were many hadrons (particles somewhat similar to protons and neutrons that we now know are made of quarks) that accelerators created. Eventually, physicists began to believe that all these particles could not be truly fundamental and that there must be some smaller number of fundamental particles. These truly fundamental particles would then be combined in various ways to produce all the hadrons.

Another important reason came from measurements of proton interactions. If you collide two fundamental particles together, the results should be a set of products whose energy adds up to the original energy of the two fundamental particles. Proton collisions actually showed something a bit different. The results were consistent with collisions of lower energy particles within the proton. If you collide two billiard balls together very hard, you get fragments that can be reconstructed to make the original two balls. If you collide a bag of billiard balls together, maybe only two of the many balls in the bags would actually collide and the others would just keep going. The fragments of the two balls that collided would have a fraction of the actual energy of the original two bags of balls. Protons seemed to collide in the same way that bags of balls collide, and therefore, seemed to be composite rather than fundamental.



Chrythes said:


> And what effect do other hadrons, fermions and other elementary particles has on us (if it's even a right thing to ask)?


There are a wide number of rather subtle effects due to "extra" particles. I am not aware of any effects that would be noticed without sophisticated equipment. So my first answer would be that there is essentially no noticeable effect on humans. There is, however, one very interesting and very important potential effect of "extra" particles. We know of 3 families of particles - the lowest (least massive) family contains the particles that make up essentially all our world (i.e. up and down quarks which make up protons and neutrons, electrons, and the electron neutrinos). There are two other families that have analogs to each of the particles in the lowest family. Muons and tau particles are like electrons with higher mass, and strange, charm, top, and bottom quarks are like up and down quarks.

It turns out that a minimum of 3 families are necessary to have what is know as CP (charge-parity) violation. Without CP violation we don't understand why matter dominates over antimatter in our universe. In the early universe matter and antimatter were created equally, but through CP violation more matter was created in various interactions than antimatter. If there were an equal amount of matter and antimatter today, no macroscopic bodies (such as the earth and humans) could exist.


----------



## Chrythes

It's not a question but since this thread is essentially dedicated to science I think this article would be appropriate here - 
http://www.insidescience.org/?q=content/every-black-hole-contains-new-universe/566

According to this article our universe might actually exist in a black hole. Maybe the physicists among us might find this interesting!


----------



## Lenfer

I wouldn't say this is a scientific question perhaps more of a political or social question. Earlier today I bought a dozen books from *Amazon*, I'm not going to give the exact price but it was roughly £150. These books are what some would call "*Classics*" or "*Academic*" books.

All of the authors are long dead and if any royalties were ever paid that period of time has expired. The cost of the books makes no difference to me I can afford it. Why though are books that the publishers must pay to print royalties and fees for less expensive than a book written over 100 years ago?

Is it because the type of person likely to read such a book is (stereotypically) more affluent than the "average" Joe or is it an attempt to put off poorer people from reading them? A type of social engineering? :tiphat:

*Edit*:

Student resources textbooks etc seem to be a lot more expensive compared to when I was at University just a few years ago.


----------



## mmsbls

aleazk said:


> mm, interesting that an experimental physicist, who has said repeatedly how he trust in the experimental reality, puts so much expectancy in a theory that has not made, so far, one single testable prediction. I'm not against string theory, but I think it has been greatly oversold. The theory is in an embrionary state right now. The theory doesn't even have a satisfactory mathematical formulation. The basic idea on which the particles are 1-dimensional is not new, Dirac proposed something similar 50 years ago. Personally, I think it's the right track to the unification, but a lot of work is necessary yet. Also, I have another problem on how they treat gravity.
> 
> (don't take this as some personal attack , it's just that I would expect more skepticism from someone like you , that relation "best physicists-string theory" really **** me off; of course there are first level physicists working on string theory, but they constantly say things like those, "best physicists-string theory", I find it rather pretentious from their part)


Somehow I missed this post earlier so I'm rather late in responding. I agree with you 100% on this. As an experimental physicist, I am _very_ skeptical of string theory. I also assume that the Standard Model will require modifications or significant changes.

When I said, "That's about the best physicists can do at the moment", I simply meant that we can only discuss what our theories say about the basic nature of quarks. I did not mean that string theory was the "best we physicists can do".


----------



## Huilunsoittaja

NEW QUESTION!!!!

I know this one will be exciting to look into.

Do any of you know about some of the theories out there on what sparks lightning in thunderstorms?


----------



## aleazk

Now that the Higgs boson has been found, I'm very worried. I was reading the comments in several newspapers and I was very surprised by the ignorance of the people. But this ignorance isn't about the higgs boson in particular, I don't intend that people must understand it, it's a subtle concept in quantum field theory, the surprising thing was the ignorance about basic concepts in epistemology. People don't know what is science, what is a physical theory, what is the role of the experiment. They mix science and religion, they say that physics and religion are "choices" (), the press, it seems, is more interested in a sensationalist title, rather than in providing accurate information. The press's role in all this has been regrettable.


----------



## ComposerOfAvantGarde

How do I know if brain is producing phenylethylamine? And how can I tell the difference between that and being high on cocaine?


----------



## SuperTonic

My understanding is that bosons are particles that carry force (photons carry the electromagnetic force, gluons carry the strong nuclear force, and the W and Z bosons carry the weak nuclear force) and that fermions are what make up what we consider "normal" matter. If that is the case, then what force does the Higgs boson carry? Gravity seems like the logical answer since the Higgs field is what gives matter mass and the force of gravity is dependent on an object's mass. But I also know that there is a theoretical particle called the graviton which is the carrier of the force of gravity. Is the Higgs boson and the graviton the same thing? Or is there some other force of nature that I am not aware of? Or is my understanding of what a boson is incomplete?


----------



## Kopachris

The Higgs boson doesn't carry one of the fundamental forces. The big thing about bosons isn't that they carry force, but that they have integer spin. For example, mesons are also bosons composed of one quark and one antiquark, but they don't carry one of the fundamental forces, either.


----------



## Philip

how many other physics students are there on this forum??


----------



## aleazk

SuperTonic said:


> My understanding is that bosons are particles that carry force (photons carry the electromagnetic force, gluons carry the strong nuclear force, and the W and Z bosons carry the weak nuclear force) and that fermions are what make up what we consider "normal" matter. If that is the case, then what force does the Higgs boson carry? Gravity seems like the logical answer since the Higgs field is what gives matter mass and the force of gravity is dependent on an object's mass. But I also know that there is a theoretical particle called the graviton which is the carrier of the force of gravity. Is the Higgs boson and the graviton the same thing? Or is there some other force of nature that I am not aware of? Or is my understanding of what a boson is incomplete?


Kopachris's answer is right. Particles come in two types: fermions and bosons. Why these funny names?. It has to do with the statistical distribution of the particles. Suppose you have many (but many) particles in a system. Also, suppose that there are several energy levels, Ei (i.e., the energy of one of the particles can be any of the Ei). If the system is in thermal equilibrium at temperature T, you can calculate how many particles, ni, there will be in the energy level Ei. This is called the statistical distribution of the system. Now, the explicit form of the statistical distribution depends on the type of quantum state that the system can have. In systems with an antisymmetric quantum state, two particles cannot have the same energy state simultaneously (degeneration zero here). This sets a constraint on the form of the statistical distribution of the system. In this case, the distribution is called the Fermi-Dirac distribution (after Paul Dirac) and has this shape:

http://www.doitpoms.ac.uk/tlplib/semiconductors/images/fermiDirac.jpg

http://upload.wikimedia.org/wikipedia/en/math/d/d/b/ddbc2f8af1d75583e36c8536f725604b.png

(in the classical, non-quantum, Boltzmann distribution, if T=0 K, then all the particles of the system are in the level Ei=0; but in the F-D distribution, this cannot be the case, since two particles cannot have the same energy state simultaneously; you can see that states with Ei>0 are also populated until you have no more particles; the highest level with nonzero population is called the fermi energy of the system; this is very important in astrophysics, since is the cause of the existence of white dwarfs and neutron stars)

In the case of a symmetrical quantum state, the statitiscal distribution is the Bose-Einstein distribution (after Satyendra Nath Bose and Albert Einstein). This exhausts the kind of quantum states.

Particles which obey the Fermi-Dirac distribution are called "fermions" and particles which obey the Bose-Einstein distribution are called "bosons".
Now, what particles are of which type?. In Quantum Field Theory, particles arise when you have a quantized field. Each kind of field gives rise to a different kind of particle, with their own set of characteristic properties. For example, the scalar, real Klein-Gordon field gives rise to particles of nonzero mass, spin zero and symmetrical quantum state. The Dirac field gives rise to particles of nonzero mass, spin 1/2, charge +1 or -1 and antisymmetrical quantum state (this field is used for represent electrons and positrons). In fact, you can show that every half integer spin particle has an antisymmetrical quantum state and every integer spin particle has a symmetric quantum state, i.e., half integer spin particles are fermions and integer spin particles are bosons. 
-------------

The graviton is a controversial subject, because of two things: according to General Relativity, gravity is not a fundamental force, i.e., is not a field which lives in flat space time (like the electromagnetic field, for example), instead, it is a property of spacetime itself!, its curvature. This poses tremendous conceptual problems if you try to apply the formalism of standard quantum field theory to gravity (represented by the spacetime metric). Even if you, artificially, decompose the metric in a "static part" and a "dynamic part" (so that you can apply the formalism of standard quantum field theory to the dynamic part), the resulting theory is not renormalizable, which means that it has no value. This problem is called the quantum gravity problem and it's an open problem in today's physics.


----------



## aleazk

^^mm, that post may be a little too technical 
There's a funny story. Until the 1920's, there were only two statistical distributions developed, the classical _Maxwell-Boltzmann_ distribution and the quantum _Bose-Einstein_ distribution. Then Dirac came and developed the _Fermi-Dirac_ distribution, but it was Dirac's discovery!. When asked why he named the distribution as _Fermi-Dirac_ (instead of the _Dirac distribution_), Dirac said "for questions of _symmetry_". :lol:


----------



## mmsbls

aleazk said:


> ^^mm, that post may be a little too technical


I've been amazed at how many members are truly interested in moderately technical discussions. The faster than light neutrino thread had interesting questions and replies from quite a few people.


----------



## Tero

ComposerOfAvantGarde said:


> How do I know if brain is producing phenylethylamine? And how can I tell the difference between that and being high on cocaine?


We could measure it in your blood, as with ADHD patients

http://en.wikipedia.org/wiki/Phenylethylamine

it's easy to make on the spot by enzymes from phenylalanine losing CO2


----------



## Philip

Polednice said:


> Yes, that's what I don't quite understand - I follow that there's an immense power involved, but where do you go from 300 _atoms_ to some kind of interface like the computers we use today? Is the collection of atoms analogous to a processor?


I recently found this video, it explains some hardware implications and developments in quantum computing:

Defining Quantum Computing





The theoretical side of things (ie. quantum algorithms), which fully illustrates the power of quantum computing, is a little more complicated and requires some knowledge of quantum mechanics and digital systems. Still, to answer your question, the collection of atoms is analogous to a register; a processor contains many registers, they are used to temporarily store the information on which operations are performed.


----------



## Chrythes

Why the graphene is considered to be two-dimensional?


----------



## Philip

Chrythes said:


> Why the graphene is considered to be two-dimensional?


Because it's flat.


----------



## Chrythes

But still, doesn't the atom has height? and there's density as well, which is basically volume, which means three dimensions.


----------



## Kopachris

Chrythes said:


> Why the graphene is considered to be two-dimensional?


Who said graphene is considered two-dimensional?


----------



## Philip

Chrythes said:


> But still, doesn't the atom has height? and there's density as well, which is basically volume, which means three dimensions.


I'd say one atom thick is pretty thin...


----------



## Chrythes

@Kopachris - http://www.nobelprize.org/nobel_prizes/physics/laureates/2010/ - 
"for groundbreaking experiments regarding the two-dimensional material graphene".

Philip - not sure if you are being ironic, but still - it has density, hence volume, isn't it then three dimensional?


----------



## Kopachris

Chrythes said:


> @Kopachris - http://www.nobelprize.org/nobel_prizes/physics/laureates/2010/ -
> "for groundbreaking experiments regarding the two-dimensional material graphene".
> 
> Philip - not sure if you are being ironic, but still - it has density, hence volume, isn't it then three dimensional?












*facepalm*

That's just... awful. I would've expected better of the Nobel Prize committee. They're using the term "two-dimensional" very loosely, meaning a "two-dimensional crystal," which is simply a crystal composed of a single layer. They're calling graphene 2D in the same way that they call buckyballs 0D and carbon nanotubes 1D. Technically incorrect, but useful (?) as a metaphor. Graphene exists in three-dimensional space. It has finite mass and finite density, and therefore volume.


----------



## Philip

Kopachris said:


> *facepalm*
> 
> That's just... awful. I would've expected better of the Nobel Prize committee. They're using the term "two-dimensional" very loosely, meaning a "two-dimensional crystal," which is simply a crystal composed of a single layer. They're calling graphene 2D in the same way that they call buckyballs 0D and carbon nanotubes 1D. Technically incorrect, but useful (?) as a metaphor. Graphene exists in three-dimensional space. It has finite mass and finite density, and therefore volume.


Hmm... i don't see the facepalm at all.

And they're not using the term "two-dimensional" very loosely, they're using it quite rigorously. When you can describe a mesh, sheet, honeycomb, whatever flat structure by a 2D matrix, it is for all purposes a 2D structure.


----------



## aleazk

Although Philip is right, I can understand Chrythes and Kopachris's position. The term two-dimensional, without further explanation, can be confusing. I mean, that review is supposedly oriented for the general public, but if you say 'two-dimensional', people immediately will ask things like those asked by Chrythes. Generally in science, the technical terms can be more subtle than the ordinary meaning of the words which compose the term.


----------



## EddieRUKiddingVarese

Mesa said:


> I prefer to handle the heavy science with visual aids.
> 
> View attachment 4456


wow that's cool


----------

