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What Are the Odds?

John on April 17, 2008 at 9:25 am

I’m on record as a Star Wars fanboy. I’m also a Star Trek fan. While the two advanced galactic civilizations they present have many differences, one thing they have in common is crowds. It seems wherever you go in the universe, there’s a unique race of technologically advanced bipeds.

Only that’s not at all likely.

In fact, there was a report on Science Daily yesterday about the ever-diminishing odds of finding intelligent extraterrestrial life in the universe:

Is there anybody out there? Probably not, according to a scientist from the University of East Anglia. A mathematical model produced by Prof Andrew Watson suggests that the odds of finding new life on other Earth-like planets are low, given the time it has taken for beings such as humans to evolve and the remaining life span of Earth.

Prof Watson suggests the number of evolutionary steps needed to create intelligent life, in the case of humans, is four. These probably include the emergence of single-celled bacteria, complex cells, specialized cells allowing complex life forms, and intelligent life with an established language.

“Complex life is separated from the simplest life forms by several very unlikely steps and therefore will be much less common. Intelligence is one step further, so it is much less common still,” said Prof Watson.

His model, published in the journal Astrobiology, suggests an upper limit for the probability of each step occurring is 10 per cent or less, so the chances of intelligent life emerging is low – less than 0.01 per cent over four billion years.

Of course all of that assumes there’s an “M Class” planet (meaning “earth-like” for you non-Trek nerds) ready and waiting on which life can get started. That’s another thing that’s a dime a dozen in science fiction. There’s always one within a few light years of your current location in case you need to set down for repairs or stretch your legs a bit.

It’s still early in the hunt for extra solar planets, but what we know already is that they are more rare than we expected. And among those solar systems that do have planets, the “M Class” variety appear to be extremely rare. Here’s a slightly dated report from 2004:

On the evidence to date, our solar system could be fundamentally different from the majority of planetary systems around stars because it formed in a different way. If that is the case, Earth-like planets will be very rare. After examining the properties of the 100 or so known extrasolar planetary systems and assessing two ways in which planets could form, Dr Martin Beer and Professor Andrew King of the University of Leicester, Dr Mario Livio of the Space Telescope Science Institute and Dr Jim Pringle of the University of Cambridge flag up the distinct possibility that our solar system is special in a paper to be published in the Monthly Notices of the Royal Astronomical Society.

Most of the extra solar planets discovered so far are gas giants which orbit closer to their host star than the earth. That’s a serious problem for life as this report makes clear:

A number of these new worlds are very exotic. For example, a year, or one orbit, on WASP-12b, is just a bit over one day. This planet is so close to its star that its daytime temperature could reach a searing 2300 degrees Celsius.

Most have eccentric orbits as well, unlike the nearly perfect circles in which the planets of our solar system travel. Practically speaking, this means that any “M Class” planets around these stars would long ago have been ejected into space or fallen into their star and been consumed. In either case, life of any kind is impossible.

Of course, even if we were to find an “M Class” planet, chances are it would not have a large moon like ours to help stabilize its orbit. Were it not for our moon, the earth would likely have long periods of history in which the angle of its axis was nearly in the plane of the ecliptic. In such a case, one half of the planet is facing the sun for 3-6 months while the other side is in darkness. If you can imagine days that last a year and how this might affect life, you see the problem.

Finally, even if everything else is just right, the universe remains a dangerous place. Consider this report of a giant gamma ray explosion:

Peering across 7.5 billion light-years and halfway back to the Big Bang, NASA’s Hubble Space Telescope has photographed the fading optical counterpart of a powerful gamma ray burst that holds the record for being the intrinsically brightest naked-eye object ever seen from Earth. For nearly a minute this single star was as bright as 10 million galaxies.

Called a long-duration gamma ray burst, such events are theorized to be caused by the death of a very massive star, perhaps weighing as much as 50 times our Sun. Such explosions, sometimes dubbed “hypernovae,” are more powerful than ordinary supernova explosions and are far more luminous, in part because their energy seems to be concentrated into a blowtorch-like beam that, in this case, was aimed directly at Earth.

This hypernova was a long way from us and could still be seen with the naked eye! If one of these were to go off in our “quadrant” (more Trek terminology) of the galaxy, the consequences would likely be devastating to life on earth.

What are the odds that there are thousands of other intelligent bipeds out there in the universe? Near zero. It’s looking increasingly likely that we may be alone in the universe.

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