The silence of the planets

I didn't realise Frank Drake, who kicked off the idea of SETI, was still alive.

But he recently spoke at the Royal Society and explained that changes to broadcast technology is making the earth harder to hear from afar:

"The trouble is that we are making ourselves more and more difficult to be heard," said Dr Drake. "We are broadcasting in much more efficient ways today and are making our signals fainter and fainter."

In the past, TV and radio programmes were broadcast from huge ground stations that transmitted signals at thousands of watts. These could be picked up relatively easily across the depths of space, astronomers calculated.

Now, most TV and radio programmes are transmitted from satellites that typically use only 75 watts and have aerials pointing toward Earth, rather than into space.

"For good measure, in America we have switched from analogue to digital broadcasting and you are going to do the same in Britain very soon," Drake added. "When you do that, your transmissions will become four times fainter because digital uses less power."

"Very soon we will become undetectable," he said. In short, in space no one will hear us at all.

What is true for humans would probably also be true for aliens...

I have a vague recollection of Arthur C Clarke also saying that this would happen. Mind you, I am not entirely sure it is a good idea to make your presence known in the universe, so a bit of quiet from planet Earth might be a good thing.