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February 09, 2009

Where are all the extraterrestrials?

radio telescope

For at least a century scientists have speculated on the existence of extra-terrestrial life. Many, perhaps most, scientists are of the opinion that given the vast number of stars and planets in just our galaxy, the possibility of Earth being the only planet with life is virtually zero. The galaxy must be TEEMING with life.

Back in the 1950s, Nobel Prize winning physicist Enrico Fermi heard the arguments in favor of extra-terrestrial life and posed a simple question: if the odds say there should be many other civilizations scattered throughout the Milky Way galaxy, why haven't we heard from them? Why have we yet to detect a single signal from an alien civilization? In other words, where is everybody?

That simple question, known as the Fermi Paradox, has stymied astronomers ever since. But Reginald Smith, from the Bouchet-Franklin Institute in Rochester, New York, thinks he's gotten around the paradox.

Smith says physicists have neglected to take into account the fact that radio signals get weaker the further they travel, and that eventually the signals become so weak they are drowned out by background radiation.

After doing some calculations on the size of the galaxy and the distance typical signals can travel before they become too weak, Smith has determined that it would take at least 300 alien civilizations before we earthlings would have a decent chance of discovering one. Or for that matter, before any civilization could detect any other. If there were only, say, 100 advanced civilizations we could all think we were alone forever.

You can check Smith's math, and plunge into the pro and con comments on his research, at http://arxivblog.com/?p=1167.


the inverse-square law into account

Posted by Chris Spurgeon at February 9, 2009 10:41 PM


Wide spillover *broad*casting is a shuck a snare a mugg's game. Only infant techno-civilizations do that, and rarely for more than a century. Eventually, all there is left to see from lightyears away is decreasing amounts of leakage.

And that's not even considering Dyson spheres. (Not to be confused with the Dyson Ball.) And, of course, if you take most of the volume of the Dyson sphere and shove it sideways into a few of those extra dimensions, all you have left here is a tiny agglomeration of dark matter, surrounded by a "holding field" of dark energy.

We don't see the other techno-societies because:

(1) they're not *broad*casting anything, so that inverse-square thing is a killer on the tiny trickles of radiation that do leak away,

(b) they're not made of meat anymore and think we're kind of primitive and disgusting, so they're just ignoring us,

3. the Dyson sphere/sideways dimension/dark matter thing,

(iv) they've blowed-up themselves or otherwise dead.

I don't think the first 3 of those are represented by terms in the original Drake equation.

Posted by: Dr Foo at February 12, 2009 08:16 AM

Wait until they figure out all the background radiation is really billions of civilizations drowning each other out with calls of 'hello?' into the darkness.

Posted by: mdh at February 14, 2009 11:37 AM