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Do radio waves go on forever?

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  • User profile image
    Cornelius Ellsonpeter

    ... or do they decay as they travel through space? How about television signals? Could you set up a receiver on another distant planet and watch or listen to "old" shows? If that were possible, and the reception were sufficient, could you take those signals, and record them for a permanent record (to capture old shows that were considered "lost")? I suppose that would be quite expensive...unless you take those captured signals and beam them back towards Earth for recording.

  • User profile image
    Angus

    This is an interesting idea. I think that it would probably not be economically viable unless some of the clips that we could recover would offer us any benefits. Aren't most things aired on TV and Radio kept by the broadcaster?

    Angus Higgins

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    Cornelius Ellsonpeter

    jaylittle wrote:
    In order to setup a receiver on a remote planet to receive such signals, we would presumably have to not only travel faster than radio signals, but we would also have to account for the distance that the specific broadcast has already traveled since it last aired.

    Quite a feat if you could do it.  Let us know what you come up with!
    It was purely a hypothetical point, and not really feasible, since I think radio waves travel at the speed of light in a vacuum (I may be wrong on that). Although, signals beamed to a satellite and back have a delay, but that may be due more to electronic processing rather than the speed of the wave travelling through air/space.

    The main question still remains...does the energy from the waves keep going forward into space? I'm sure it is quite possible that another planet, assuming they can receive our signals and process them properly, could be viewing information about us from decades ago.

  • User profile image
    Cybermagell​an

    Cornelius Ellsonpeter wrote:
    ... or do they decay as they travel through space? How about television signals? Could you set up a receiver on another distant planet and watch or listen to "old" shows? If that were possible, and the reception were sufficient, could you take those signals, and record them for a permanent record (to capture old shows that were considered "lost")? I suppose that would be quite expensive...unless you take those captured signals and beam them back towards Earth for recording.


    Radio waves do decay (they do on earth too), they also receive interferance as well. Being in Communications in the military you learn the distance for the amount of wavelength.

    If you were to reduce the amount of interferance between earth and your target and had the appropriate wavelength behind the signal then yes you could record "older" shows. Remember everything that travels through space has a certain "speed" so by the time you sent a signal here from earth to reach your destination it would take a certain amount of time...so if you sent a TV signal here from earth to mars it would be older by the time it got there for the distance it takes it to get there...make sense?

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    pathfinder

    Isn't this the idea behind SETI?  Maybe not to get TV shows, but to discover communications from other planets, either on purpose or by accident.

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    AlienRancher

    Radio signals decay over time. Consider a finite burst of signal that starts its trip from the antenna. Just like ripples on a pond the signal travels like an expanding sphere. The finite energy of the original burst will be evenly split over the surface of the sphere. As it travels the surface of the sphere grows bigger and bigger at a rate of r^2, where r is the distance from the antenna.

    In an ideal model the strength of the signal never ever reaches zero, so it would be possible to create an huge antenna with super sensitive amplifiers that captures it.

    However there is noise. Noise is inherent to the physical world. Nothing can remove it. So at a distance where the local noise is bigger than the signal that is the maximun distance you can hope to be able to recover the signal from the noise.

    The shape of the antena changes this game some, the kind of signal (for example AM vs FM) changes this game some too. Its a long topic.

  • User profile image
    Cornelius Ellsonpeter

    AlienRancher wrote:
    Radio signals decay over time. Consider a finite burst of signal that starts its trip from the antenna. Just like ripples on a pond the signal travels like an expanding sphere. The finite energy of the original burst will be evenly split over the surface of the sphere. As it travels the surface of the sphere grows bigger and bigger at a rate of r^2, where r is the distance from the antenna.

    In an ideal model the strength of the signal never ever reaches zero, so it would be possible to create an huge antenna with super sensitive amplifiers that captures it.

    However there is noise. Noise is inherent to the physical world. Nothing can remove it. So at a distance where the local noise is bigger than the signal that is the maximun distance you can hope to be able to recover the signal from the noise.

    The shape of the antena changes this game some, the kind of signal (for example AM vs FM) changes this game some too. Its a long topic.

    Hmmm. Okay, I just saw something over on Space.com about the 10 strangest topics in space, and one of the topics was on neutrinos, and another on quasars. Now I'm wondering what type of energy is emitted by a quasar.

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    AlienRancher

    Now we are getting outside of what I know. Officially, energy is the capacity of doing work where work means afecting something where the standard reference (for me EE) is moving one electron one meter.

    The kind of energy is a wierd question. Energy can be categorized many ways. I am now going to guess you you meant:

    For objects that far away from earth just a few types can reach us for example electromagnetic energy or gravitational energy. The standard carrier for EM engery is the photon.

    In some cases even particules can reach us, like protons or neutrons, they also carry kinetic energy. Here you hear terms like alpha, or beta particles.

    It sounds like you have an interest in physics. My recomendation (that you haven't asked for) is to go read the basics and pay little atention to flashy science news sites which only aim to the wow factor and often just confuse people.

    Once you master the basics, you'll see that most science news are the equivalent to a mc donalds meal.

  • User profile image
    jsampsonPC

    Sound always amazes me. It's nothing more than compressed and rarified air, yet it works so nicely. Aggregating all of the air molecules in between the sender, and the receiver, creates the beauty of audibility.

    But what blows my mind is how we are able to separate the sounds when many dozens are going simultaneously. Suppose one person says, "Hello". That sends the air molecules crashing into one another until they hit your ear, and you interpret it.

    Now suppose a dog barks at the same time the person said hello...what happens? Two sources are disturbing the placement of the air molecules between three points. What do you hear? Two distinct sounds. You're not confused by the message, even though it's one sound with two senders being split up into two messages.

    To further complicate things, add a truck driving by while the dog barks and the friend says, "Hello". Now we have the Doppler Effect on a larger scale in the scenario. Yet you still tell exactly which message comes from which source, and the message isn't destroyed.

    The dog barking doesn't destroy the message coming from the friend saying "Hi". The truck driving doesn't destroy the sound of the dog barking (Unless it's much closer than the dog). That's like throwing three stones into a small pond, and tracking the ripples created by each stone....and keeping track of them.

    Truly amazing!

  • User profile image
    W3bbo

    jsampsonPC wrote:
    

    Sound always amazes me. It's nothing more than compressed and rarified air, yet it works so nicely. Aggregating all of the air molecules in between the sender, and the receiver, creates the beauty of audibility.

    But what blows my mind is how we are able to separate the sounds when many dozens are going simultaneously. Suppose one person says, "Hello". That sends the air molecules crashing into one another until they hit your ear, and you interpret it.

    Now suppose a dog barks at the same time the person said hello...what happens? Two sources are disturbing the placement of the air molecules between three points. What do you hear? Two distinct sounds. You're not confused by the message, even though it's one sound with two senders being split up into two messages.

    To further complicate things, add a truck driving by while the dog barks and the friend says, "Hello". Now we have the Doppler Effect on a larger scale in the scenario. Yet you still tell exactly which message comes from which source, and the message isn't destroyed.

    The dog barking doesn't destroy the message coming from the friend saying "Hi". The truck driving doesn't destroy the sound of the dog barking (Unless it's much closer than the dog). That's like throwing three stones into a small pond, and tracking the ripples created by each stone....and keeping track of them.

    Truly amazing!



    It's not that amazing, we covered this in physics in detail.

    All sounds are combinations of sinusidal signal waves, in this case compression/rarification of air.

    A guitar note is a combination of some 50+ sine waves at once, for example.

  • User profile image
    Cornelius Ellsonpeter

    jsampsonPC wrote:
     Sound always amazes me. It's nothing more than compressed and rarified air, yet it works so nicely. Aggregating all of the air molecules in between the sender, and the receiver, creates the beauty of audibility.

    But what blows my mind is how we are able to separate the sounds when many dozens are going simultaneously. Suppose one person says, "Hello". That sends the air molecules crashing into one another until they hit your ear, and you interpret it.

    Now suppose a dog barks at the same time the person said hello...what happens? Two sources are disturbing the placement of the air molecules between three points. What do you hear? Two distinct sounds. You're not confused by the message, even though it's one sound with two senders being split up into two messages.

    To further complicate things, add a truck driving by while the dog barks and the friend says, "Hello". Now we have the Doppler Effect on a larger scale in the scenario. Yet you still tell exactly which message comes from which source, and the message isn't destroyed.

    The dog barking doesn't destroy the message coming from the friend saying "Hi". The truck driving doesn't destroy the sound of the dog barking (Unless it's much closer than the dog). That's like throwing three stones into a small pond, and tracking the ripples created by each stone....and keeping track of them.

    Truly amazing!
    I'm getting this vision of multiple Beer28 personalities posting on a forum, and all of their personalities bouncing comments off each other.

    [C]

    But yes, it is amazing, because some of those frequencies surely overlap. It a lot like listening to music, too, and someone trying to yell at you at the same time.

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