Thursday, July 01, 2010
Let's give a bit of perspective today on the Fermi Paradox, the paradox whereby if life (or the probability of life) in the universe is common, why haven't we found any evidence for it or why hasn't anyone contacted us?
The perspective for this lies in the comparison between the amount of time Earth has had life vs. the amount of time it has had civilization, and a civilization that is capable of sending out radio signals. Life on Earth has been around for about 3.7 billion years, human civilization (the Neolithic onward) is roughly 10000 years old, and we have been sending out radio signals for about 100 years.
So let's take a look at what this means in terms of distance. Here's a picture of the front of the Vancouver Public Library. The red line here is about 3 cm, the part where the guy's shoe is touching the ground. This represents the 100 years we've had radio. That's 33 years per cm.
Next we'll take a look at the length representing the period of time from 10000 years ago to today. If you were observing a planet with this level of development you could interact with the people on the ground if you landed, but from far away there is nothing to differentiate between this and the other 3,699,990,000 years where there was life but no civilization. Of course, there was homo sapiens before that but we'll use 10000 years as a rough number. On this image then that works out to 3 metres.
All right, so now let's trace back the other 3,699,990,000 years where the Earth had life but no civilization. That works out to 1121 km. If you want to go from Vancouver to Calgary that's a distance of 973 km, so here you go:
View Larger Map
To get some perspective on the length of time between Earth with life vs. Earth with human civilization, just follow the blue line until you get to Calgary and remember that every 3 cm is the length of time Earth has been sending out radio signals to the rest of the universe. Don't cheat by zooming out!
Or if you prefer, you can just follow this line to the east. No zooming out here either.
View History of life on Earth in a larger map
The real question re: the Fermi Paradox is just how long civilization lasts. It may be that civilizations tend to destroy themselves after reaching a certain level of technology, and if so that would explain the lack of evidence for them (so far). A planet that had civilization complete with radio for even as long as a million years pales in comparison to the 3.7 billion years of life on this planet. For all we know they would have been easily detectable sometime during the Cretaceous, for a full million years, but since then destroyed themselves. In any case, it's certainly likely that simple life is extremely common. For all we know it could exist in the cloudtops of Venus, in the seas of Europa or Enceladus, or even on Titan.