# Science questions answered here



## Metairie Road (Apr 30, 2014)

I am currently in a freindly (so far) debate with a Ptolemaic geocentrist. Before this debate degenerates to the level of personal insults and bloodshed I want to crush this person with logic first.


I'm not an Astrophysicist or a mathematician so I need someone to answer this question for me -

Assume first that the Earth is at the center of the universe; fixed and unmoving, and all the heavenly bodies go around the Earth.

Assume also that the stars are all at the same finite distance, and go around the Earth once every 24 hours - As per Ptolemy's geocentric model.

The question is, how far from the Earth would this hypothetical 'Sphere' of stars have to be to avoid going faster than lightspeed relative to the Earth.

I hope the question isn't too vague. It's clear in my mind, I just have difficulty putting it into the right words.

Alternately - Epsilon Eridani is ten lightyears from Earth. It goes around the Earth in 24 hours (in Ptolemy's Universe). How fast is Epsilon Eridani moving relative to Earth?

Thanks in advance
Metairie Road


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## Mahlerian (Nov 27, 2012)

Good luck winning a debate with logic. Usually people will start resorting to ad hoc hypotheses, no matter how unlikely, to save the viability of their pet position.


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## mmsbls (Mar 6, 2011)

The radius of the sphere would be roughly .00044 light years. The stars would travel a distance 2*pi*R where pi = 3.14159 and R is the radius of the sphere in 1 day (1/365 year). The speed would be 2*pi*R/(1/365) or distance/time. That quantity would have to be less than the speed of light which is 1 light year per year. 

Anyone believing the Ptolemaic system probably wouldn't be convinced by arguments using special relativity.


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## Guest (Dec 20, 2015)

Never argue with a nutter.


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## Strange Magic (Sep 14, 2015)

Ask your Ptolemaic geocentricist how, on a non-rotating earth, one accounts for the Coriolis effect, the 24-hour full rotation of the trace of a swinging pendulum at either of the earth's poles, and the deviation of the earth's figure from a perfect sphere resulting in polar flattening and the equatorial bulge. That should set them back on their heels!


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## TurnaboutVox (Sep 22, 2013)

Metairie Road said:


> I am currently in a freindly (so far) debate with a Ptolemaic geocentrist. Before this debate degenerates to the level of personal insults and bloodshed I want to crush this person with logic first.
> 
> I'm not an Astrophysicist or a mathematician so I need someone to answer this question for me
> 
> ...


If Epsilon Eridani is at 10 light-years from Earth, then the path it travels around the earth is πD, i.e. approximately 62.8 light years.

If it does this in 24 hours then it is traveling at 365 x 62.8 times the speed of light - and so therefore it's not!

But why would your geocentrist believe that the speed of a body is limited to the speed of light anyway?


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## senza sordino (Oct 20, 2013)

The distance to Epsilon Eridani was probably calculated using parallax. And this calculation necessitates that you know the Earth orbits the Sun.


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## Guest (Dec 20, 2015)

Metairie Road said:


> Alternately - Epsilon Eridani is ten lightyears from Earth. It goes around the Earth in 24 hours (in Ptolemy's Universe). How fast is Epsilon Eridani moving relative to Earth?
> 
> Thanks in advance
> Metairie Road


Using my gozintas, I'm calculating an angular velocity of pi radians per 12 hours. Then to get the tangential velocity we multiply that by the radius of 10 light-years and I'm getting 2.618 light-years per hour or between 3 and 4 billion miles per second.


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## Headphone Hermit (Jan 8, 2014)

best science question I heard recently was posed by a 7-year old child: "how come when you pull the plug out of the socket, electricity doesn't leak out if it flows along the wires?"


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## TurnaboutVox (Sep 22, 2013)

Headphone Hermit said:


> best science question I heard recently was posed by a 7-year old child: "how come when you pull the plug out of the socket, electricity doesn't leak out if it flows along the wires?"


Oh, it will if the said child forces something electrically conductive into the socket. I know this from experience, age 4!


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## Weston (Jul 11, 2008)

People don't really believe in geocentric or other outmoded nonsense. They're just being sphincters to annoy people. The best way to win that argument is not to give them the attention they are craving.


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## Johann Sebastian Bach (Dec 18, 2015)

I doubt the geocentrist would be troubled since the non-rotating earth would display none of the features you mention (unless it had just ceased to rotate). Had rotation suddenly ceased, I suspect a number of more pressing matters would be on the minds of the inhabitants, such as gravity. 

The speed of EE, given the parameters described by the OP, must be infinite (which is clearly bonkers).


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## Couchie (Dec 9, 2010)

It might be more fun to argue for the Tychonic system while castigating his lack of keeping pace with the lastest science.


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## EddieRUKiddingVarese (Jan 8, 2013)

Couchie said:


> It might be more fun to argue for the Tychonic system while castigating his lack of keeping pace with the lastest science.


I fear that the 16th century would be far too modern for this ancient Greek, maybe the Taco model might make a greater impression.


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## Lukecash12 (Sep 21, 2009)

Metairie Road said:


> I am currently in a freindly (so far) debate with a Ptolemaic geocentrist. Before this debate degenerates to the level of personal insults and bloodshed I want to crush this person with logic first.
> 
> I'm not an Astrophysicist or a mathematician so I need someone to answer this question for me -
> 
> ...


How much of a Ptolemaic thinker are we talking about? Lol, this guy may not even believe in the Baconian (i.e. inductive metaphysics, Empiricism, "science") method in the first place. Kind of hard to talk science with someone who doesn't believe in science.


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## Nereffid (Feb 6, 2013)

So presumably this geocentrist believes that several decades' worth of space probes and landers have been faked?

Because if scientists are using a heliocentric model to determine the positions of the planets and the trajectories needed for the spacecraft to get there, then in a geocentric universe all their calculations would be horribly wrong.


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## Potiphera (Mar 24, 2011)

It certainly is an interesting question.


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## Strange Magic (Sep 14, 2015)

Johann Sebastian Bach said:


> I doubt the geocentrist would be troubled since the non-rotating earth would display none of the features you mention (unless it had just ceased to rotate).


I should have made my post more clear by stipulating that our Ptolomaic Geocentrist is indeed on our rotating orb, but is convinced that it is not rotating. He then must somehow square his belief system with the manifest existence of the Coriolis effect, etc.


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## Lukecash12 (Sep 21, 2009)

Strange Magic said:


> I should have made my post more clear by stipulating that our Ptolomaic Geocentrist is indeed on our rotating orb, but is convinced that it is not rotating. He then must somehow square his belief system with the manifest existence of the Coriolis effect, etc.


Well... you just need to get a little more contemporary for him, is all! There were heliocentric thinkers before and during the Alexandrian empires. You needn't to appeal to anything in modern science to prove the solar system is heliocentric. What first threw Copernicus off about Ptolemaic ideas about orbits is the ad hoc apex explanations.

Ptolemy explained the inconsistency of a geocentric cosmos, with the appearance of the Wandering Stars (i.e. planetas, or "planets"), by saying that they were not just orbiting the earth but points in space he called apexes. The more we were able to observe the Wandering Stars and calculate their orbits, the more apexes were posited, until Jupiter, for example, was supposed to be traveling around seven points in addition to the Earth. Haufner and Copernicus, actually harking back to Stoic and Cyrenaic ideas out of the Second Academy (Platonism was popular in the early Christian and Hellenic world, until the second millennium during which time Aristotle ruled the day for over half a thousand years), posited that no apexes were necessary if we centered their orbits on the sun.

While the eventual conclusion on these imaginary apexes may seem obvious to us today, it is not so obvious when you don't have too many solid conceptions about the laws of motion yet, and are looking at oval shaped orbits if the planets travel around the sun. Other points they are traveling around begin to make a lot more sense in that context, hence the long struggle over it when Empiricism was being born.

In a very real sense, what we have today is the second reign of Platonism.


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