Hi, I'm Neil deGrasse Tyson, guest hosting today on TED Talks Daily.

Here's a talk from the TED Fellows community given by fellow astrophysicist Sarah Ruechheimer,

asking the question, are we alone in the universe?

From microorganisms to aliens, she walks us through

what's really out there or what's maybe not out there or what we want to be out there or

might not want to be out there. And she will also take us through what we can expect in the coming decades in the

search for extraterrestrial life. Check it out. I want to find aliens. Finding life on another planet

is not just going to be a little hard. It's going to be very hard. But for the first time in human history,

we have a chance to detect signs of life on another planet. Or maybe we've already detected it

on Venus. Or maybe not. There are still two big hurdles when it comes to confirming life on another

world. The first is building a telescope big enough to do this, and the second is interpreting

what we will find. When we think of extraterrestrial life, we tend to think of aliens, like

funny little green men, not aliens as single-celled microbes. But it's actually detecting

signs of microbial life on another planet that I'm most optimistic about and what I focus my research on.

I model how a star's high-energy radiation can make gases from microbes harder or easier to see with future telescopes.

Microbes have dominated our planet's biosphere for most diverse history.

They've been emitting gases that can be

seen in our atmosphere, even light years away, for billions of years. Now, if an alien astronomer

we're looking at Earth, they would probably detect gases like oxygen, methane, and nitrous oxide

before detecting signs of us. Even with an active biosphere like Earth, most of the gases that indicate life are coming from

single-celled microbes, not from animals.

This is what we'll try to do in the next decade of astronomy.

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