Research scientists discussed the existence of exoplanets, black holes, and potentially controllable wormholes in real life.

While Thorne’s book explains how the science was arrived at, and coordinated with the plot ideas of the Nolans in forming the movie, Interstellar, this scholarly discussion brings the focus back to the scientific phenomena of black holes.

THE KAVLI FOUNDATION: Before we talk about the movie itself, let’s begin by explaining some of the phenomena in Interstellar. To help us out, Eric, will you give us a simple explanation of a black hole? And to make more challenging for you – and because it’s nearly the Thanksgiving holiday here in the U.S. – I’m hoping you’ll explain it to us using only objects you might find in a kitchen.

ERIC MILLER: That might be a little challenging but I’ll give it a go. A black hole is essentially a very dense concentration of matter – or food that you could find in the kitchen. A black hole is that it’s so dense that there’s a region around it outside which light can’t escape. This is why it’s called a black hole. The radius inside of which light can’t escape is called the event horizon.

But the key to a black hole is not that it’s massive but that it’s very dense. In fact, a black hole can be made of very little mass – maybe like a green pea. But they can also be supermassive – which I guess would be like the turkey on the Thanksgiving table. The green pea black holes have about 10 times the mass of the sun and an event horizon maybe 20 to 30 kilometers across. In contrast, the turkey ones – like the one in this movie – are more like a million to a billion suns worth of mass concentrated in a very small amount of space with an event horizon about the size of our solar system.

Another thing about black holes is that matter is sucked into them kind of like matter travels down a funnel. As it travels down, it often spins around – much as we see in the movie. I think we’ll talk more about that later.

“I was actually very happy with the science and very happy to see something where these science concepts were put up on the big screen.” – Eric Miller

TKF: You mentioned one term, the event horizon. Is that the point at which gravity is so strong that nothing, even light, can escape?

MILLER: That’s right. It’s called the event horizon because you have no knowledge of events that happen inside. Instead, it looks black because light is not escaping the event horizon. That’s why we call it a black hole.

TKF: Moving on from black holes, Hardip, I’m hoping you can tell us a bit about far away planets. What do we know about planets in other solar systems? Are there likely to be habitable ones out there?
Black holes, like the one in Interstellar (shown here), are bright in the regions where they pull in matter, but dark past their “event horizon,” the radius inside of which not even light can escape the black hole’s gravitational pull. (Image: Warner Brothers Pictures and Paramount Pictures)

Black holes, like the one in Interstellar (shown here), are bright in the regions where they pull in matter, but dark past their “event horizon,” the radius inside of which not even light can escape the black hole’s gravitational pull. (Image: Warner Brothers Pictures and Paramount Pictures)

HARDIP SANGHERA: We discovered the first extrasolar planet in about 1992. Now we’re up to about nearly 2,000 discovered extrasolar planets, thanks in great part to the NASA Kepler Mission. If we extrapolate from that number, we can estimate that there’s probably anywhere between 100 billion and 1 trillion planets just within our galaxy. One of the things that we’ve learnt is that our solar system actually isn’t the typical scenario for a solar system; most other solar systems are nothing like ours. What we tend to find is a lot of big gas giant planets clustered close to their stars. That would make it far too hot for life or habitability as we understand it. Plus, there’s no real surface to talk of on these planets.

There’s actually a catalog of habitable exoplanets that lists about 21 planets we’ve found so far that have the best chance of life. These planets seem to be in habitable zone, where the planet could harbor liquid water, not frozen or evaporated. What we really want to find are planets that are not too big – so that they have a surface – and not too small – so that they can hold onto an atmosphere.

The 21 planets we’ve found match these criteria. But these are, as I said, only the ones we can see: we can view light from a sun coming through the planet’s atmosphere or we can isolate the light from the sun off the planet. What’s even more amazing is that in this way we can actually learn, to some degree, the weather conditions on these planets. In perhaps a few years time we’ll actually be able to look for signatures of life. Maybe we’ll see traces of the oxygen in the atmosphere. You never know what’s to come.

TKF: Mandeep, will you explain the general concept of a wormhole? Maybe you have a piece of paper there with you and can demonstrate using a couple of origami moves.

MANDEEP GILL: First let me brush the popcorn off so we can talk. Now, wormholes are pretty speculative. We are very clear that exoplanets exist; we’ve seen them. Likewise, we know there are black holes because we see very clear evidence, as Eric mentioned, at the center of our galaxy and in other places. Wormholes are different. They are a potential solution to what are called Einstein’s equations – our best theory of gravity. Albert Einstein and Nathan Rosen wrote papers on them originally, and then John Wheeler coined this term wormhole. He showed that wormholes would be unstable, that the ends would “pinch” off. Later it was Kip Thorne, who was actually an executive producer on the movie Interstellar, along with his student Mark Morris who showed that in some way you might be able to stabilize the two ends.
This artist’s concept illustrates a supermassive black hole with millions to billions times the mass of our sun. (Image: NASA/JPL-Caltech)

This artist’s concept illustrates a supermassive black hole with millions to billions times the mass of our sun. (Image: NASA/JPL-Caltech)

So what are these things? As you see in the movie, there’s an area that’s kind of a portal, an extra dimension, between two points in the universe. I’m going to use this two-dimensional analogy, a sheet of tissue paper, to demonstrate. If you lived in two dimensions on this plane, you would never see the third dimension – if one existed around you. But if you could somehow fold space, and go through that third dimension, you could move between two points on the tissue paper, traveling through the portal.

As I mentioned before, Thorne and Morris sought to find a way to stabilize the mouths of these wormholes to keep them in place. They thought of some weird, negative energies – things that we don’t normally see. But we do now have this concept called dark energy – people may have heard of it, it’s something that was discovered about 15 years ago when we found that the universe’s expansion is accelerating. That type of a strange “substance” – which involves high but constant energy density and negative pressure – could possibly allow for wormholes. But to implement it to stabilize wormholes is still very theoretical – the stuff of science fiction buffs’ dreams. And I think that’s great.

TKF: With that little bit of background, let’s jump into the movie.