I know you asked Clifford and not me, but I think any scientist ought to be able to answer this.

Broadcast energy propagates outward from earth in a sphere; the energy in each spherical shell is constant, but as the size of the sphere gets bigger, the energy density (what appears on your antenna) gets weaker in proportion to the area, which is proportional to the square of the time since the energy was emitted. So yes, the further out the signal gets the weaker it is, but it never goes away altogether.

We can never catch up to our broadcasts because they propagate at the speed of light, the universal speed limit. However, if there is someone out there besides us with a receiver, they will definitely notice a huge pulse in radio energy from our direction (which they will associate with our sun before they notice or deduce that there is a planet here).

If such aliens exist, whether they manage to decode these broadcasts to sounds and images is hard to say; that depends on how far away they are and how hard they try. If they exist and decode the messages, whether they can extract any sense out of those sounds and images is even more speculative.

There's an old science fiction story somewhere about humorless aliens decoding the early TV comedies (Milton Berle, Lucille Ball and the like) and deciding on that basis that humans are too dangerous and that the earth must be destroyed...

Michael, you beat me to it, saying everything I wanted to say. Ziya, they don't degrade, they dilute. The fields emitted fall off as the square of the distance, and so those distant stars and seeing a tiny amount of signal. If they were lucky to be looking our way in the first place, they'd have to sift through all the other junk, and maybe then see that the signal is not random junk (pre-reality tv and talk radio signals of course). This is precisely what SETI is trying to do, where we play the role of the aliens*. Michael also ended with a plot about the detection of the signals. I was going to do the same thing, except that I was going to mention the plot of the excellent film Galaxy Quest, where an alien civilization takes the broadcasts of a Star Trek like show to be archives of feats of real daring do, and then grab the actors from the show to try to get them to help them in an inter-species war. Hilarity ensues (as they say). And it really does.

-cvj

*I should also point you to the time when we (humans) did see a regular signal coming from out there and thought for a short while that it was a sign of life. Turned out to be a pulsar (neutron star). Wonderful story. Have to run to teach a class on General Relativity now...

Ziya wrote:

"In theory, would it be possible for someone in the future, far far away, to actually receive, watch and record an episode of Wired Science?"

So the answer is "yes", with the caveats above about how difficult it is... but get this... because of wireless connections to the web, in that future they in principle can be reading your blog post where you've asked that question too! So smile and wave!

-cvj

Clifford, it really is odd how similar we are in some ways given how different we are in some ways...

Yes, it is, isn't it?!

-cvj