Science Questions

What happens to TV signals at light-speed?

Tue, 24th Dec 2013

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Hisham Forster asked:

Einstein's theory of relativity describes how time seems to go slower at near light speed.


But, if I were to be inside a train that goes at the speed of light (impossible, i know) and i had a TV screen to see my other 'twin' that is observing me from outside, would he see me like "heeeellllllooooooooo bbbbrrroooooottthhhhheeerrrrr" like really slow? and, if that is true, then would I see him really fast?


If both are true, wouldn't the train no longer be travelling at the speed of light because it has to make everything slow, hence also travelling slower? Wouldn't this be a paradox?


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What I donít understand is why people who know that relativity states that nothing can move at the speed of light would ask a question about something moving at the speed of light and act as if the question was meaningful. So why would you ask a question which you know is meaningless?

Why on earth do you think anybody would know what Ff means?

The answer to your question is that the entire question is meaningless. Youíve asked about what would happen if the impossible happens and everyone knows thatís a meaningless question. And please don't use terms which are undefined or only understood by certain people. Pmb, Fri, 12th Jul 2013

Let's say you were traveling 1m/s slower than the speed of light while making your historic broadcast...

Your brother outside the train would see your broadcast slowed down dramatically; the frequency of your TV transmission would be reduced, more than you would expect from Doppler shift alone. The frequency of your voice would be reduced.

However, if your brother outside of the train then made a broadcast back to you, the frequency of his TV transmission would be reduced, more than you would expect from Doppler shift alone. The frequency of his voice would also be reduced.

ie, you would each think that time was running more slowly for the other person. This is one of the apparent paradoxes that happen with Relativity.

(Note: this assumes you are using some old-fashioned form of analogue modulation for your TV transmissions, despite your obviously hi-tech train!) evan_au, Sat, 13th Jul 2013

It would still be boring starbuck1963, Wed, 2nd Oct 2013

Lit hem who is withuot typos cost the farst stane. :) Bill S, Wed, 2nd Oct 2013

The screen would be filled with endless repeats of The Great Escape, The Sound of Music, Morecambe & Wise, Andy Williams, The African Queen....Good heavens! It's happening right now! alancalverd, Wed, 25th Dec 2013

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