What is life? How do you define what things are living and what things are dead?

You might look at a running cheetah and say that thing is clearly living and you look at a

chunk of granite rock and you say, okay, that thing is not living.

But where do we draw the line? And when we land on other planets someday, what can we

realistically expect aliens are going to look like? Will we even recognize strange forms of life?

Or will we only have the capacity to recognize

things that are very close to earthly life?

And what does any of this have to do with Frankenstein or ancient Greek philosophers

or the possibility of finding a cell phone on Mars?

Welcome to Inner Cosmos with me, David Eagleman.

I'm a neuroscientist and an author at Stanford.

And in these episodes, we dive deeply into our three-pound universe

to uncover some of the most surprising aspects of our lives.

In today's episode, we're not only going to dive into our

three-pound universe, but into the larger universe that surrounds us to think about the question

of what is life. So, what do we mean when we say something is alive? This is one of the

oldest questions that biologists have been asking,

and it's a strangely tough one. So today we're going to take a run at this question from a

completely different angle from the point of view of theoretical physics. Joining me today will be

physicist Sarah Walker, who with her colleagues is working

to ask the question of what is life through a very different lens. And we're going to get into

questions like what we might expect when we discover life elsewhere in the universe and how we

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