# Radio communications with a Mars base...

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Hello all.

To maintain a 'fluent' conversation with a Martian colonization, the propagation delay would make it very different from what we are used here.

If a straight theoretical rod, (unbendable, uncompressible, unstretchable) extending between Mars and Earth is mechanically end-pushed to mean 'one' and pulled to mean 'zero' as method of archaic 'modulation'... What would be theoretically the transmission delay ?

Edited by Externet
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It would still be laggy. However i'm sure you could talk on a forum like this one.

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Light waves and radio waves are basically the same thing - electromagnetic waves at different frequencies - so they would have the same delay.

If a straight theoretical rod, (unbendable, uncompressible, unstretchable) extending between Mars and Earth is mechanically end-pushed to mean 'one' and pulled to mean 'zero' as method of archaic 'modulation'... What would be theoretically the transmission delay ?

The data would travel along the rod at the speed of sound (in the rod). If it were infinitely stiff (made of unobtanium) then the fastest possible speed of sound is equal to the speed of light.

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Thanks.

The data would travel along the rod at the speed of sound (in the rod). If it were infinitely stiff (made of unobtanium) then the fastest possible speed of sound is equal to the speed of light.

Do not use soundwaves as the 'data' transmitted by the rod. (Yes, it is mechanical too) A mechanical motion instead. Push 1 cm in at this end, get 1 cm out at the other end of the unobtanium rod.

Or, push 1 mm to mean '1', 2mm to mean '2', 3mm to mean '3' ... as a non-binary 'modulation'

Edited by Externet
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Thanks.

Not soundwaves as the 'data' transmitted by the rod. A mechanical motion instead. Push 1 cm in at this end, get 1 cm out at the other end of the unobtanium rod.

But mechanical movement travels at the speed of sound (in the medium).

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Correct, but the medium (unobtanium rod) would be the one moving, not about the waves in it.

Like hitting a rod end with a faster than sound hammer blow. The other end of the unobtanium rod will move (advance) before any sound wave transits within the loooong rod.

Edited by Externet
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Correct, but the medium (unobtanium rod) would be the one moving, not waves in it.

Like hitting a rod end with a faster than sound hammer blow. The other end of the unobtanium rod will move (advance) before any sound wave transits within the rod.

No it won't.

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Sound waves are molecules bumping against each other. If you push on the rod you are causing the molecules to transmit force down the rod, ie sound waves.

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Hello all.

To maintain a 'fluent' conversation with a Martian colonization, the propagation delay would make it very different from what we are used here.

Yes, they would. But they would be tiny differences. The index of refraction for the different frequencies would not be the same, so the delay in parts of the atmosphere would be slightly different (GPS uses this effect to help improve positioning). But, again, the effect would be tiny.

(e.g. GPS signals through the ionosphere can be delayed up to about 70 nanoseconds. Using a second frequency with a different delay allows you to calibrate a more precise value)

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ACG52... force ie soundwaves ?

OK, Strange.

So a 6100* metres long steel rod (held/guided in such way that will not deform) if pushed 1cm. by your finger at one end, will not move its other end forward until 1 second later ?

* (Length chosen just because sound propagates at ~6100m/s in steel)

Exactly.

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Thanks, gentlemen. Learned something else from you today. As many other times.

Is it safe, or accurate to say:

"A mechanical linkage transfers motion with a delay equating/corresponding to the propagation speed of sound in the linkage material" ?

Or, can your knowledge improve that wording ?

Accurate.

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...if pushed 1cm. by your finger at one end...

Ha ha, you must believe that Strange is some kind of Superman able to compress steel with his fingers.

Okay, I need help with this... there is an 'infinite'-length steel rod.

1. I push its one end by some centimeters. I suppose the rod resists. But after a looong time does the back-force drops to zero?

2. I start pushing its one end by some subsonic speed. Is back-force constant now? Does it depend on the speed? Can Strange really push it long way with his fingers if he does it very slowly?

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