Radio / TV Signals Sent into space over the years How far will they travel?

ronan45 · 22-12-2011 2:07pm #1

I read the following paragraph on another site. But I was wondering does a radio signal start to degrade after so many million light years? How far can these signals go from earth before they just turn into white noise and mean nothing?

Radio signals will propagate as far as the power with which they are transmitted will allow them to go (space is an excellent transmission medium being that it is mostly empty). So ... yes; some distant civilization will at some point probably be able to watch "American Idol" if they have a decent receiver. I know you didn't ask that but I'm guessing you were wondering it. And may god bless us all if they ever actually do see that crap.

Popoutman · 22-12-2011 2:22pm

It'll all depend on the signal to noise at the receiving end. As the signals go out, each time they double in distance travelled, they get 1/4 as powerful, as the area covered by the signal is x^2 as x increases by 2. When the distance is 10 times as far, the signal is 100 times fainter. So if you are having problems receiving ITV in Ireland when transmitted from the UK, it'll be very hard to make any sense of those signals at the distance of the moon, let alone at interstellar distances.

Communications with space probes at other planets and in interplanetary space, the scientists use very well directed high-power beams to transmit, and large dish receivers with extremely sensitive receivers with fantastic signal to noise characteristics to receive.

Thank god though that reality TV ends up effectively in the background noise long before the nearest star could make sense of it..

coylemj · 22-12-2011 11:45pm

The Voyager probes have been told to face back towards Earth and to block all RTE broacasts involving Twink from leaving the Solar System for fear that they might cause some alien civilisation to invade us in at attempt to eliminate this deadly threat to the universe!

ODubhain82 · 23-12-2011 11:27pm

If a civilisation is capable of receiving our transmissions and turning up at our front door, how would that go for us? Imagine no one knew Ireland existed and then RTE fired up the transmitter. Would the neighbours turn up to be friends or ....