Kip Thorne, Feynman Professor of Theoretical Physics, Emeritus, at Caltech, is a leading authority on some of the most intriguing issues in physics today.
Much of his work is based on Einstein’s theory of general relativity, which poses that the gravitational force from an object can actually warp the space and time around it. Thorne focuses on the study of black holes, which have such strong gravity that space and time are warped almost beyond imagination.
Sound incredible? You can learn more when Thorne delivers a lecture about his work at Northwestern on Monday, October 18th, at 4:00 PM. We spoke with him for a preview.
Your talk will focus on “the warped side of the universe.” What do you mean by this?
I mean objects and phenomena that are made from warped space and warped time, rather than being made from matter, like you and me, and the Sun and the Earth.
How can space and time be warped?
We’re all familiar with space. Suppose we think about space as the surface of a rubber sheet, like a child’s trampoline. We put a heavy stone in the center of the sheet, so the sheet bends downward. Now, suppose you and I are ants, and we live on that sheet; it is our space. If we wander around on the sheet, we can measure things like the circumference around the region where the stone is and the diameter. We’ll find that the diameter can be big compared to the circumference, because the sheet is sinking down so much.
Well, that warped rubber sheet is very analogous to the space in which we live, which is three-dimensional, not two. Similarly, the space in which we live can be warped, and is strongly warped, around black holes.
Black holes are an example of one of these objects that are composed of warped space and time. How can something be “made” of space and time?
A black hole Is originally “born” from something made of matter. A big massive star implodes, and when it implodes it creates, or generates, strongly warped space and time around itself, forming a black hole. The matter implodes into the center of the black hole, where it’s destroyed, and there’s nothing left behind except warping of space and time. So, there’s no longer any matter associated with the black hole at all, and it’s holding itself together nevertheless. It has highly warped space in the sense that the circumference around the black hole is very small compared to its diameter, which of course never happens for circles drawn on a flat piece of paper.
I know that one way researchers hope to learn more about black holes is by studying gravitational waves. What are gravitational waves?
When two black holes collide, they merge, and it’s a very wild phenomenon. It sends space into wild oscillations like the surface of the ocean in storm. Just as waves travel out from a storm’s center in the ocean, colliding black holes send waves traveling out through the universe, and they carry information about these colliding holes. These waves are actually waves of oscillating space and time. Time speeds up and slows down when the wave passes, for example.
I co-founded the LIGO (Laser Interferometer Gravitational Wave Observatory) with Rainer Weiss at MIT and Ronald Drever at Cal Tech way back in 1983. We had a vision that we would be able to detect these waves, [and that] we would be able to use them to explore things on the warped side of the universe, such as colliding black holes, and the very birth of the universe itself.
How could gravitational waves provide information about the origin of the universe?
It’s likely that in first one second of the life of the universe, there was a lot of violence going on. The universe was born in a gigantic explosion, it probably inflated extremely rapidly for a short time, and slightly later there may have been violent changes in the laws of nature, called phase transitions – all in that first one second. The birth, the inflation and the phase transitions may have generated a rich set of outgoing gravitational waves.
Gravitational waves are the only kind of radiation that is so penetrating that it would emerge unscathed from this first one second of the universe, [bringing] us a picture of what was going on then. So the long-term goal is to use gravitational waves to study the earliest moments of the universe.
LIGO is already collecting data. What have you found so far?
We have not seen any gravitational waves yet. We designed LIGO to be built in two steps. In the first step, we installed instruments – gravitational wave detectors – that had a sensitivity good enough that, if we were lucky, we would see waves, and we would get experience with detectors. Then, we would upgrade to much more sensitive detectors that should see lots and lots of waves. The LIGO team begins that upgrade next month. It’s quite possible that there are one or two gravitational waves in the data that the team is currently analyzing, but if not, after the upgrade, we expect to see lots of waves.
During your career, you’ve also talked about an interesting possibility known as a wormhole, which I know a lot of science fiction fans are excited about. Would you tell me what a wormhole is, and whether you think it’s possible?
A wormhole is another kind of possible object on the warped side of the universe, made from warped space. It’s like a handle on a coffee cup – an alternative route to get from one place on the cup to another, or in the case of a wormhole, from one place in the universe to another. Wormhole handles can actually be quite short according to theory, but still connect very distant regions of the universe. You could imagine one mouth of the wormhole in our solar system, and the other mouth in some distant gallery, and it might only be a few miles through the wormhole to get from the solar system to the distant galaxy.
These wormholes are hypothetical. They’re allowed by Einstein’s laws of general relativity, but they might be forbidden by the laws of quantum physics, and we don’t know for sure yet whether they’re allowed or forbidden. That’s an area of current theoretical research. If wormholes are possible, the technology for constructing them is far, far beyond human capability in the coming century.
I’ve read that wormholes might connect different places in space, but also in time. Is that true?
It’s conceivable that you could use wormholes to go backward in time. I think the evidence against that is pretty strong, but again, we don’t know for sure. The answer to whether that’s allowed is held tightly in the grip of the combined laws of quantum physics and general relativity—what we call the laws of quantum gravity. We don’t understand those laws well enough yet to answer the question of whether backward time travel is possible.
What is your current research focus?
My own current work is focusing on understanding black holes. For the first time, scientists are able to simulate colliding black holes on computers– and watch the holes create wild oscillations in the fabric of space and time. So this is a unique moment in the history of this subject, when computers can show us things we’ve never seen before. In my lecture I’ll talk about some very recent discoveries about whirlpools and tornados in the fabric of space, that can be attached to black holes, and how they behave and how we can observe them with LIGO.
Learn more at Thorne’s lecture, The Warped Side of Our Universe: From the Big Bang to Black Holes and Gravitational Waves, on Monday, October 18th, at 4:00 PM on Northwestern’s Evanston campus. The event is free and open to the public. Click here for more information.