When you're walking around outside this week, you're probably going to see a lot of skeletons.

You might see some mummies.

You're definitely going to see some ghosts.

And it's because Halloween is all about blurring the line between the dead and the living.

On the surface, it can seem like a magical, fanciful kind of thing.

But when you actually get down to it and you look at it from a scientific perspective like we tend to do on our show,

it turns out the definition of death isn't all that clear.

And someday, maybe, it might be flexible, even reversible.

Our reporters, Bird Pinkerton and Brian Resnick, looked into this question last year, and we thought

we'd share the episode again with you just in time for Halloween.

And just a heads up before we start, there are some explicit descriptions of death in the

episode.

So what is death?

According to Bob Droog, death used to be pretty obvious.

Up until about the 1950s, there was no confusion about what death meant.

Bob's a bioethicist who thinks a lot about what death means. And he says that for a long time...

It meant that you weren't breathing, your heart had stopped, you were stiff, and you were, you know, blue or gray.

It was so clear that one researcher I spoke to told me, in the early 1900s, people weren't really writing down textbook definitions of death.

They were more interested in telling people how to test for it.

Like, you could put a mirror in front of someone's mouth to see if it fogged up,

and if it didn't fog up, they weren't breathing, and were therefore probably dead.

But by the 1950s, technological breakthroughs were starting to confuse the issue here.

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