This is Science Friday. I'm Ira Plato. Today on the podcast, how much do we really know about how the universe works?

I'm not sure we really know anything with a capital K.

If you follow this program over the years, you know that I love to tackle the big but really

simple, tough questions of science, the things that really make your hair hurt when you try

to wrap your mind around them. Like, what is time? Or if the universe started from the Big Bang, what happened

before that? And sometimes I wonder just what the limits of science are to answering these

questions. I mean, are there things that we humans just can't know? Things that science can't

really answer with the research tools that we have? Well, that's what we're going to be talking

about. And joining me is Dr. Kelsey Johnson. She's a professor of astronomy at the University of

Virginia, former president of the American Astronomical Society, author of the book, Into the Unknown,

the quest to understand the mysteries of the cosmos. Welcome to Science Friday.

Hi, Ira. It's really an honor to be here. It's an honor to have you. Do you like to delve into

these questions yourself? Oh my gosh. I think about them all the time and they're what,

get me out of bed in the morning. You know what? When I talk to astronomers and physicists,

sometimes they say the actual quest

is better than the answer. Is that true for you?

You know, I think it is true because there's something that's so valuable about curiosity.

And once we've satisfied our curiosity, we kind of want to move on and get our next hit of

curiosity. So there is something really important about

the quest itself. Let's talk about some of these things. It feels like every week, especially in

astronomy and astrophysics, we get some results that says, hey, rethink what you thought

you knew. I mean, how much of anything do we actually know for sure in astronomy and astrophysics?

...