DAVID GREENE, HOST:
OK, so as we reach the end of the year, it seems like it's a nice time to take a step back and get some perspective. And I mean stepping way back and getting some serious perspective, like the scale of the entire universe kind of perspective. My colleague, Nell Greenfieldboyce, recently asked scientists some basic questions about the universe. And this week on the show we'll hear their answers. Today, we start at the beginning - the very beginning.
NELL GREENFIELDBOYCE, BYLINE: When I sat down with astrophysicist Chuck Bennett at Johns Hopkins University, I asked him, where did the universe come from?
CHUCK BENNETT: That happens to be my absolute favorite question.
GREENFIELDBOYCE: He says everybody has heard of the Big Bang theory. It says the universe started out dense and hot and then expanded.
BENNETT: I would state the Big Bang theory as the universe has been expanding and cooling for 13.8 billion years - period.
GREENFIELDBOYCE: Notice he didn't say where the original stuff came from or what happened to set it off.
BENNETT: The Big Bang theory doesn't actually say what happened right at the beginning.
GREENFIELDBOYCE: He says that you can follow our laws of physics back, but they break down close to the start, when things were unspeakably hot and close together. Still, there may be clues from the weird world of quantum physics. In that world, our intuition isn't a good guide. Strange stuff can happen, like particles can just appear out of nowhere.
BENNETT: Even if you take something that's a complete vacuum, you've gotten all the particles and dust and everything out of the way, in quantum mechanics, you still have particles popping in and out of existence all the time.
GREENFIELDBOYCE: So maybe the kernel that became our universe just randomly and spontaneously appeared.
BENNETT: It seems bizarre, but that is kind of the going thinking about this.
GREENFIELDBOYCE: And if you want to think about something even more bizarre, consider this point made by Caltech theoretical physicist Sean Carroll. He says the start of the universe is the start of time itself, which creates a conundrum.
SEAN CARROLL: So there's no verbs before time itself exists, right? There's no popping into existence. There's no fluctuating. There's no quantum mechanical craziness. There is literally nothing.
GREENFIELDBOYCE: He says it's possible the Big Bang emerged from something else.
CARROLL: That could have been the very first moment in the history of the universe, or it could have come out of something bigger. We just don't know quite yet.
GREENFIELDBOYCE: He says, don't be unsettled by the idea that the universe plays by its own rules.
CARROLL: The universe is special. You know, the universe is not the things inside the universe.
GREENFIELDBOYCE: It's not like you and me. Nell Greenfieldboyce, NPR News.
(SOUNDBITE OF MARTIN O'DONNELL & MICHAEL SALVATORI'S "HALO")
GREENE: Just tackling some small topics, like the universe. Tomorrow, we'll tackle whether the universe is infinite and what you might see if you could get into a spaceship and try to fly to its edge.
(SOUNDBITE OF MARTIN O'DONNELL & MICHAEL SALVATORI'S "HALO") Transcript provided by NPR, Copyright NPR.