# Relativity and Music



## MarkW (Feb 16, 2015)

Okay, this is for science jocks.

Positing that we send a space probe out of the solar system, broadcasting some earthly music to let others know that we were once here . . .

When the relative velocity between the probe and a listener reaches a level where relativistic effects (i.e. red- or blue-shifts) apply, What happens to what they _hear_? Does the music speed up or slow down? Does the key modulate up or down? Are harmonic relationships preserved? Does it matter how the signal is encoded (i.e. AM or FM or ?)?

I thought about this on an airplane recently, when I wondered whether the in-flight music was from an on-board tape, or being picked up from a satellite broadcast or somewhere else.


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## KenOC (Mar 7, 2011)

I believe that if the music were digitally encoded (likely) the only effect would be the duration or "baud speed" of the received transmission. So Beethoven's 9th might be received entirely in, say 5 minutes. But the pitches, note durations, volume levels, and so forth would still have their proper values when decoded since the actual digital information would not be changed.

If it were an analog radio transmission, I'd think the pitches would be raised and the tempi increased if the spacecraft were moving toward the receiver, and the opposite if it were moving away. At least for AM. FM? Not sure about that!

Does that sound right?


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## Becca (Feb 5, 2015)

The following comes from a biochemist/software engineer and I am sure that the hardware types will thoroughly dissect it!

You can't actually send a digital signal, it has to be time encoded onto a waveform. There are many ways to do it with the ability to have increasingly faster data rates is a function of the tricks used to encode the data.

As to the analog signal, think of te Doppler effect.


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## Richard8655 (Feb 19, 2016)

Becca said:


> The following comes from a biochemist/software engineer and I am sure that the hardware types will thoroughly dissect it!
> 
> You can't actually send a digital signal, it has to be time encoded onto a waveform. There are many ways to do it with the ability to have increasingly faster data rates is a function of the tricks used to encode the data.
> 
> As to the analog signal, think of te Doppler effect.


I think that's right, the Doppler Effect comes into play. The pitch changes as in a passing train whistle. Who knows, maybe the lower baroque period pitch of A at 415hz returns again.


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