Physicist Stephen Hawking has created a stir by warning that aliens could endanger humanity, and that we should refrain from drawing attention to ourselves.

“If aliens visit us, the outcome would be much as when Columbus landed in America, which didn’t turn out well for the Native Americans,” he suggested on his Discovery Channel series.  “We only have to look at ourselves to see how intelligent life might develop into something we wouldn’t want to meet,”  the BBC quotes him as saying.  And: “I imagine they might exist in massive ships, having used up all the resources from their home planet. Such advanced aliens would perhaps become nomads, looking to conquer and colonize whatever planets they can reach.”

While this is a possible outcome, that it “would” come out this way presupposes a lot about the nature of aliens.

As I’ve noted, aliens will be alien.  They might be benevolent, hostile, or indifferent, and they might have purposes and emotions incomprehensible to us.  (We tend to define emotion and intellect by our own mind’s range, but that is as silly as defining sight by our own limited sensing capabilities on the electromagnetic spectrum.)  Neither conquest nor excessive resource use are inherent in an intelligent species, but are instead products of our distinct evolutionary heritage.

Aliens will also be quite advanced, if they can show up here — we are rapidly developing the technology necessary to detect ourselves at a distance — so it is not clear that we can make ourselves much less conspicuous.

Writing for a Wall Street Journal blog, professor Paul Davies has his own reasons for doubt:

• The galaxy is vast, and interstellar travel may be unlikely.
• If aliens needed resources, some ancient species would have shown up long ago in Earth’s history.
• An advanced species would be unlikely to be aggressive by nature, or would have engineered the tendency out of themselves by now.  “Any truly bellicose alien species would either have wiped itself out long ago, or already taken over the galaxy.”

Let’s hope Davies is right, and we end up more with Close Encounters than Independence Day.

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New discoveries are revealing the potential range of extraterrestrial life forms.

Scientists have found microbes that live nearly two miles underground, completely detached from the surface biosphere.

Previously discovered deep-dwelling organisms had used molecules ultimately derived from surface plants or animals, and thus ultimately from solar-powered photosynthesis.

The newly-identified creatures don’t need sunlight: they live off radiation, combined with sulfur-bearing rocks and water.

This greatly expands places to look for life, beginning with Mars and various of the solar system’s moons.

Curiously, these bacteria live very slowly, dividing only every 45 to 300 years, thousands of times less often than their surface relatives.

This raises the possibility of lifeforms living and perceiving existence at a fundamentally different pace from ours.