Let me pose this question as a hypothetical.

Your ship warps/jumps to a planet 50 light years away. You set up a radio signal receiver. Theoretically, the radio is going to receive radio-waves from Earth from 50 years ago.

My question is even with a powerful receiver, would the signal be clear enough that I could listen to 1968 radio stations without problems or would the signal have degraded to an almost undecipherable static? if so, what factors would be the cause of the degradation? Can gravitational or other interstellar phenomena (radiation?) degrade a radio signal?


1 Answer 1


No, you can’t pick up radio broadcasts from fifty light years away without a receiver that’s more powerful than anything we currently know how to build. The degradation is caused by the inverse square law — a broadcast that’s designed to be picked up 1,000 miles away will be about 22 orders of magnitude weaker at a distance of fifty light years. See this Physics Stackexchange question.

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    $\begingroup$ More than powerful I'd use the term sensitive. $\endgroup$
    – L.Dutch
    Commented Sep 22, 2018 at 6:28
  • $\begingroup$ @L.Dutch I’m just using the same terminology as the question, which talks about a “powerful receiver”. $\endgroup$
    – Mike Scott
    Commented Sep 22, 2018 at 6:56
  • $\begingroup$ Ah, yes. 'Sensitive' would be the right term, thank you. $\endgroup$
    – Moin
    Commented Sep 22, 2018 at 10:31
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    $\begingroup$ Radio transmitters can have a power of a few kilowatts, and with a dish the size of Arecibo it might well work. I think it's more of a problem that most radio waves don't get out of earths conductive ionosphere. $\endgroup$
    – Karl
    Commented Sep 22, 2018 at 19:29
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    $\begingroup$ @Karl No, it would be much too faint for Arecibo to pick it up. See the answer to the question linked in my answer. $\endgroup$
    – Mike Scott
    Commented Sep 23, 2018 at 5:45

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