Will radio and television signals broadcast from earth propagate through space for eternity?

Answer 1

'Eternity' is severly limited by signal attenuation. With our very best dish antennas, we can communicate with distant spacecraft. Broadcast radio and television generally use a low radiation angle to mazimize their coverage area. Therefore, little energy is aimed up into space. And the low angle radiation is bent by the ionosphere so that it 'skips' back down toward earth. Almost nothing from earth is detectable beyond our solar system.

Answer 2

well, the answer is this:
Depending on the frequency, a good part of the signal bounces back off the ionosphere (higher frequency signals tend to bounce less, so more of that energy escapes into space (which is why they use microwave range frequencies for satelite communications). anyway,
Now the laws of physics (and I don't remember which one and the names) dictate that the amplitude of an electromagnetic signal decreases exponentially with distance. So if the signal is 9db at 1 mile, at 2 miles the signal strength won't be 4.5db (half) it will be sqrt of 9 which is 3db, and at 3 miles it will be 1.73 db, so you can see that it doesn't take a whole lot of distance for that signal to become pretty weak. But even though that signal approaches 0 after a while, that signal is still there, except for the fact that other signals and the electromagnetic noise out there will totally overcome it, so there will be no way to distinguish it from the noise.
Obviously it depends how strong the original signal is, but radio and tv signals don't just keep propagating forever, Stronger signals get farther, but none of them lasts very long.

Answer 3

Individual photons (of which radio waves are constituted) are able to propagate until they collide with another particle so technically, yes a photon from a television broadcast could potentially survive, however if you mean signal in the traditional sense (alien life able to receive our broadcast at some future date) then the answer is no. The signal will fade dramatically over the vast distances involved, our transmitters are designed for relatively short distances, the power required to create a signal that could be received by an alien species on an intergalactic scale is quite large.

Answer 4

First of all, not all radio and TV signals bounce off the upper atmosphere. How these electro-magnetic forces propogate depends solely on the frequencies of those signals. Higher frequencies tend to not bounce, they travel in straight lines pretty much; lower frequencies tend to bounce (really bend, not bounce). Very low frequencies, however, might even penetrate solids, like the Earth.

TV signals, for one, do not bounce off the upper layers. They are straight line of sight signals. That's why, in olden days, we had to erect tall antennas...to pick up the TV signals directly from the transmitters. Otherwise, the curvature of the Earth would block our Howdy Doody Show each Saturday morning.

Second, the non bouncing signals will travel outward forever, unless something intercedes...like Van Allen belt, solar storms...to essentially destroy the signals.

Third, after traveling great distances and great dispersion, the signals will no longer be recognizable as coherent signals by even the most discriminating, sensitive receivers. In which case, something called the signal to noise ratio will be so small, we can hardly call it a signal carrying information any more...even though some of that signal energy might still be there.

So if you mean by signal something that is carrying discernable energy (information), then, no, it will not travel forever. But if you mean does some of that transmitted energy travel forever, even though it might not be detectable, then, yes, if nothing intercedes it.

Answer 5

First response is only partially correct. The ionosphere will reflect AM broadcast signals, and the longer shortwave signals, but anything over 30 MHz goes through it. Hence, with a suitably large antenna and sensitive receiver you could watch Oprah re-runs on TV on Alpha Centauri. Of course, at that distance, a suitably large antenna would be about the size of Earth's orbit around the sun.

Answer 6

I would guess there is a radius beyond which the signals become so weak as to become lost in the background noise. That radius may be several light years, but nowhere near the size of the universe. Remember, those signals were not intentionally beamed into space. A narrow, focused beam of microwaves would probably be detectable over a much greater distance, perhaps hundreds of light years.

Answer 7

The behavior of radio waves is explained by the presence of large number of free ions and electrons in the upper layers of atmosphere called ionosphere.

Ionization of atmosphere is not uniform, i.e., the number of free charges per unit volume varies from one layer to the next.

The refractive indices from layer to layer vary.

A wave entering the ionosphere at an angle is continuously defected from normal as it enters successive layers.

Depending upon the angle of incidence at the maximum ionized layer, a wave may pass through the ionosphere and recede from the earth or after being bent more and more, return to Earth.

A wave returns to Earth if it strikes the ionosphere at angle greater than the total internal reflection angle.

For smaller angles, the wave is propagated into outer space.

By repeatedly being reflected from ionosphere and terrestrial surface, short wave can round the globe, experiencing considerably less energy loss in the case of long waves.

Since ultra high frequency can pass through a layer of free charges they are not deflected by ionosphere and are used to send waves through ionosphere.

Answer 8

No. They bounce off a layer of the atmosphere called the ionosphere. The continue bouncing around between the earth and the ionoshphere until absorbed by the matter on earth and turned into heat.

Answer 9

Supposedly. Imagine some "Chuck Berry" tearing up the sound waves around Uranus.

Answer 10

I think that most of them are eliminated by the atmosphere. The earth's magnetic field also interferes, as well as solar winds.