Milky Way Inhospitable?

tdfunk writes "Space.com reports that life in the universe may be more rare than previously thought. In an article published today, Space.com quotes Guillermo Gonzalez, an Iowa State University researcher, who has studied the structure of our galaxy and has concluded that life may not be as common as we may have believed. Apparently, conditions around the Milky Way Galaxy are generally less hospitable than once thought.

Comments

Old news...

[Boulder Geek]

Guillermo is well known for the "Rare Earth" hypothesis, which boils down to the thesis that planets identical to Earth are extremely uncommon. This has even been covered on Slashdot before.

I don't entirely disagree with Guillermo, but he does make one major blunder, IMHO: He assumes that complex life can only develop on planets with all of the same characteristics as Earth. That sub-hypothesis is not proven.

Regardless, lets say that a exact Earth analogs occur around one out of a billion stars. That still leaves 100 Earth analogs in the Milky Way alone.

The real issue for finding ET, IMHO (that sure gets tossed out a lot when discussing life in the Universe ;-) is that time is so much longer than we humans can perceive. Humans have been around in our present form for only a few thousand years, with only a couple of decades when we could be detected by extra terrestrial civilisations. In terms of the age of the Earth that is nothing, and compared to the age of the galaxy it is smaller than nothing. Our window in time is so narrow that it seems unlikely that it actually overlaps with other civilizations.

a galaxy full of germs

[bcrowell]

Unfortunately, popular articles, including this one, don't usually do a good job of making the distinction between unicellular and multicellular life. There's every reason to believe that unicellular life is common in our galaxy. Microbes are tough. They can survive and/or permanently adapt to extremes of temperature and chemistry. It's quite possible that even within our solar system, there is unicellular on three different bodies: Earth, Mars, and Europa. When the "rare earth" folks talk about the dangers to life, such as ionizing radiation and comet strikes, those are really more like hazards to multicellular life. An unknown, but probably very big, percentage of the earth's biomass consists of microbes living deep underground or underwater, where they're relatively invulnerable to these things.

Multicellular life is a whole different story. It's a lot more delicate, and in our planet's geological history, it appears as an afterthought. Germs are and always have been the dominant form of life here.

Sorry if you're in love with the Star Trek/Star Wars picture, but most likely if our species ever manages to send probes to the nearest 10,000 solar systems, all we'll find is unicellular life. I'll bet your great-great-great-great-great grandkids a six-pack on it!