Calling Occupants of Interplanetary Craft was a song by Klaatu and popularized by the Carpenters way back in 1975. It explored the idea that we've been broadcasting radio signals for about 100 years, and those signals are now about 100 light years away. The idea being that remote intelligence could be eavesdropping on our goings on by listening to these broadcasts. Classical, jazz, swing, rock'n'roll, The Honeymooners, Lucy, Star Trek, General Hospital, Mary Tyler Moore, Friends, Seinfeld, and so on.Except none of that is even remotely possible. A spacecraft orbiting our earth might be able to pick up short bursts and squawks, if they knew the details of our modulation schemes. Maybe analog AM and FM would be decipherable, but digital is highly unlikely. What's more, our terrestrial commercial broadcasts are designed for terrestrial pickup. A very small amount of power is accidentally beamed up into the sky, and even less makes it outside of our atmosphere. The ionosphere reflects most of it back to ground. But it gets worse. Anyone outside earth orbit would receive a hodgepodge of signals from all over the planet: nothing but a scramble of noise and interference.
We do beam some signals out to satellites, spacecraft, and once upon a time, to men on or near the moon. But those transmissions are beamed specifically at the target, with tracking antennae. And remember, the earth is spinning on its axis. The radio signals we beam out sweep across the sky as the earth rotates. The farther away it gets, the faster it sweeps. So someone 100 light years away would only get a blip of a single station for a fraction of a second every 24 hours. If they were trying to listen to a conversation, or a newscast, let alone decode our picture format, forget about it. If they could receive us at all, we'd look like a noisy radio source; a pulsar.
Keep in mind that our signals would get weaker and weaker as the beams spread out, the further they get from earth. Besides, there would be natural and alien made interference near the alien's receivers that would drown out our feeble squawkings.
The idea that anyone could actually receive, decode and listen to our stupid broadcasts is absolutely ridiculous. That's why I cannot take anything Carl Sagan says seriously.
