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Timescales and aliens

This morning I had a teleconference with the good folks running the upcoming Discover Magazine/TMT discussion panel (see the flyer in the last post). After going over the details about the format and subject matter, I'm really excited. It's going to be a lot of fun answering questions from the public about exoplanets and the prospects of finding another Earth around a star other than our own.

The discussion this morning, and the webcast of last year's event, got me thinking about what types of questions I'll likely hear. One question that I think I can count on is, "Do you think there is life out there?" This question was asked in at least two forms in last year's panel discussion, and the subject matter wasn't focused exclusively on Earth-like planets like it will be this year. And when people find out that I study exoplanets, this is usually one of their first questions.

My answer is usually in two parts. First, yes, I believe there is life out there. This belief is based on the relative ease and speed with which life sprang up here on Earth. Indeed, the more places we look for life on Earth, the more it is becoming clear that life doesn't have overly stringent requirements. Given a decent energy source, life seems to happen quite readily.

One example was recently in the news. Researchers drilling beneath the Polar ice cap were surprised to find a 3-inch long shrimp hanging out 600 feet below the ice and 12 miles away from open water. The shrimp seemed quite happy in its cold, dark environment. What is especially striking is that the researchers weren't looking for life, yet there it was. And the life form was macroscopic, implying there was ample food for it down there, which probably means tons of additional, smaller lifeforms down where no one expected it. Life has been found deep underground, thriving around volcanic vents at the bottom of the ocean, and nearly anywhere else you can think to look. Why not beneath the ice on Europa, or on the shores of the methane seas on Titan, or on a blue planet orbiting another G-type star?

The second part of my answer to the question about extraterrestrial life is that, while I think there is life out there on other planets, I don't think it is very likely at all that there is intelligent life. And I suspect that this is what most people want to know about: where's ET? To understand why I think intelligent life is rare, you need to come to terms with the extreme age of the Earth, and how recently intelligent life came onto the scene.

The best way to think about geological (and astronomical) time scales is to imagine a time-lapse movie of the Earth's history, played back such that the whole movie takes only 24 hours. Here's the Earth's history on a 24-hour clock (midnight straight up, noon straight down):


If we start the movie at midnight, we wouldn't see any life until about 3am, when the first single-cell organisms show up. Then you have to wait another 12 hours until the first multi-cell organisms start swimming around. Land dwelling planets appear at around 9:20PM. Dinosaurs arrive on the scene at 10:45PM!

The first human-like apes join the party extremely late, knocking at the door at 11:57PM. Homo sapiens wake up at 23:59:56.9PM. The first known civilization starts up at 23:59:59.9PM. Finally, the Industrial Revolution fires up 1 millisecond before midnight.

So, if an alien living on Earth II orbiting Alpha Centauri A picked a random time in the Earth's history to start searching for life, it wouldn't be very likely that the alien would pick a time when humans are doing their thing--all broadcasting radio waves, blasting off into space, altering the atmosphere. Similarly, it's not very likely that we'll find an Earth-like planet with intelligent beings waving back at us (under the assumption that intelligent life unfolds elsewhere at the same rate it does here on Earth).

However, just because something is unlikely doesn't mean we shouldn't look around. There are about 300 billion stars in the Galaxy, and in the Solar neighborhood alone about 20% have planets of some sort or another.

So where's ET? Stay tuned. The Kepler Mission will likely find the first habitable Earth sometime in the next 2-3 years. SETI is diligently scanning the skies, looking for radio waves and laser pulses carrying messages from a distant civilization--all with the desktop computers of ordinary Earthlings. And my collaborators and I are about to submit a proposal to the National Science Foundation for funding that would help us build the next generation Earth-hunting instruments. If life is out there, we intend to find where it lives, and soon!

Comments

blissful_e said…
Love reading your blog - there is always something new to discover!

When I read about the drilling you linked to with the shrimp, it made me think of the work Ben does sending probes miles into the earth - and what do you know, it's being presented at a geophysical conference.

Exploration jobs - whatever they explore - are just so cool.
JohnJohn said…
Exploration is why I love astronomy. I get to explore from the comfort of my office rather than drilling through an ice sheet in the freezing cold...

I love how the shrimp seems curious about the camera. Think of it from the shrimp's perspective: OMG, alien probe!
JohnJohn said…
Exploration is why I love astronomy. I get to explore from the comfort of my office rather than drilling through an ice sheet in the freezing cold...

I love how the shrimp seems curious about the camera. Think of it from the shrimp's perspective: OMG, alien probe!
Misspudding said…
Drilling is fun! Even just tens of feet below the surface, there is always a really fascinating story. :)

But yeah...the Earth is OLD. And why wouldn't there be life somewhere else in the universe? We're so earth-o-centric around here!
Marcia said…
Intelligent life may have not been around very long on Earth, but that doesn't meant that intelligent life can't last very long.

An intelligent civilization could have arisen long before intelligent life developed on Earth and still be going strong.

Unless, you take on the pessimistic stance that intelligent life is inherently self destructive.

Here are some more examples of life that exists in conditions that make human life impossible:

http://www.earthfacts.net/nature/extremophiles/
JohnJohn said…
Good point, Marcia. I guess my pessimism about intelligent life on this planet is implicit in my analysis of intelligence elsewhere. As long as we're extrapolating from a single data point, if we assume that intelligent aliens are like humans, it's not likely that they'll stick around for long after reaching sentience. I hope Earthlings can prove me wrong and reverse the trend, preferably in my lifetime!

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