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Where do aliens live?

We know life exists on Earth, but we have yet to find it anywhere else.

We have mathematical projections which forcefully argue the number of stars and planets in the universe is so vast and infinite, life must be all over it – but we have yet to find it anywhere else.

A new study from the Harvard-Smithsonian Center for Astrophysics doesn’t change that. But if life is out there, these findings could go a long way to telling us where to look.

“We don’t even need to know exactly how it’s spreading,” Harvard researcher Henry Lin explained in a chat with Yahoo Canada.

“Whether it’s spreading by spaceships colonizing galaxies, or by spores riding on asteroids, it doesn’t really matter. The point is, we now have a generic way to search for the spread of life.”

And it’s complicated. I’m as likely to walk on another world as I am to give you a simple explanation of what these guys are doing.

Essentially, though, if we find an Earth-like world out there that might support life, we now have reason to believe other similar planets in the neighbourhood might have caught it, too.

But … how?

“There could be a variety of ways,” Lin said.

“For example, an impact could kick up primitive spores, and imbed them in asteroids that could travel outside of the solar system. It’s feasible that some of these will end up getting recaptured by other stars, and could eventually find their way on to other habitable-zone planets, where they could seed life.

All of which takes millions of years, minimum. And it begs the question: if life is here and spreading, why isn’t in all the neighbouring star systems as well?

“Maybe all the civilizations are very close in development. In which case, it may be less surprising that we haven’t been contacted, because it takes so much longer to develop spacefaring technology.”

Ever since the search for life on other worlds began, scientists have been hunting for interstellar radio signals as a tell-tale sign there’s someone out there.

Lin has a new idea. Why not search for … industrial pollution?

“We would specifically have to target those molecules that chemists believe cannot be produced by geological causes,” he said.

“There are certain chemicals – chlorofluorocarbons in hairspray, for example – it’s highly unlikely that would be produced naturally. They can’t be produced by volcanoes and things like that.”

Lin noted that the technology for this hasn’t quite yet arrived. But in mankind’s ongoing explosion of innovations, he doesn’t think it will be long.

“It’s just like a virus. A virus has an evolutionary pressure to be able to transmit itself between hosts. In some ways, we are a virus that has inhabited a host, and there may be an evolutionary pressure for us, or other species, that have existed or that will exist, to be able to transmit themselves – especially because our host, the Earth, has a finite amount of resources,” Lin concluded.

“It could also be because we are destroying our host.”