Black Holes and Time Warps

"Kip Thorne’s book mostly focuses on space time. It is really the most modern exposition yet at a popular level of Einstein’s theory of relativity. Black holes and wormholes are all explored. Kip Thorne was there when all of this was at its most exciting. One of the many contributions he made to theoretical physics was understanding that wormholes might be able to be turned into time machines. So if you want to know what a wormhole is, and how time machines might work, this is the book for you. Well, we all want the same thing. We want to know the laws of nature. And what we do is we use different clues to guide us. We know that gravity is a natural force. We also know that there are particles and fields in the universe. Some people come from the particles and fields perspective to try to put gravity into that. Others take our success with gravity that Einstein handed down, and try to make it compatible with particles and fields. People like me take the early universe, the Big Bang, and try to use that as a clue to understand the laws by which it is run."

"This book is just plain fun. I said before that if somebody asked me for a book to learn about relativity, I probably wouldn’t pick Einstein’s: I would pick Kip Thorne’s. This book introduces the basic ideas of relativity. He talks about how distances in space and lengths of time appear different or are different to different observers in different frames of reference. Then he talks about how gravity is really just the shape and geometry of space. “If somebody asked me for a book to learn about relativity, I probably wouldn’t pick Einstein’s: I would pick Kip Thorne’s” Then he goes into the modern stuff about relativity, which is so weird and cool and different. This is stuff no one thought about in Einstein’s lifetime. I’m talking about questions like, ‘Can you build a wormhole that allows you to travel from one place in the universe to an entirely different place in the universe traversing a very short distance?’ He talks about black holes a lot, and how time itself passes differently as you get near the surface of a black hole. It’s all the stuff that you’ll find illustrated in the storyline of a movie like Interstellar . Kip Thorne was involved in the writing of that movie, but he wrote it first in this book (not in a narrative sense, but in a popular science sense). I read his book a long, long time ago and it’s what made me love relativity. It’s just such an incredible and vivid and exciting depiction of this strange thing that is the geometry of space-time. We’ve certainly never seen a wormhole. If a wormhole existed and it was the sort of wormhole that allowed you to get from point A to point B faster than it would take light to get from point A to point B, that would basically be a time machine. Now, I think it is unlikely that wormholes exist in our universe. For one thing, if there were, and you could use it for time travel, then you’d run into various logical paradoxes like, for example, the grandfather paradox. If there’s a time machine and I can use it to go back to a time before my grandmother met my grandfather, I can kill my grandfather and then he doesn’t have any kids and therefore I’m not born so I don’t go back in time. We’re back where we started and you can see how this falls apart. So the self-consistency of our universe seems to prohibit backwards time travel. We can go forward in time. We know how to do that, it just involves travelling near the speed of light. If you do that, time travels differently for you and you can move into the future. But you can’t go back. So, I suspect, if there are wormholes they function in some way that doesn’t allow traditional time travel. Right now, there’s a culmination of mysteries in cosmology that need to be told as a coherent story. The mysteries I’m talking about are: 1. What’s dark matter? We know it’s there and makes up 5/6ths of the matter in our universe. We thought we had good ideas for what it is, but we’ve done the experiments to find those things and they haven’t come up. So we haven’t found it yet or at least we’re not confident we have. That poses enormous questions about how it was formed in the Big Bang and that first fraction of a second. 2. We still don’t know how matter survived the Big Bang. This is a story people have written about in books before, but not recently, to my knowledge, and it points to the same period of time that dark matter was formed in. I think there’s a real chance these puzzles are intertwined and that whatever the solution to one might very well be the solution to the other. Exactly what the solution looks like is still unclear, but it’s pointing to this first fraction of a second after the Big Bang where we don’t have any direct observations. It’s possible things played out really differently to what cosmology textbooks currently describe. 3. Third is the issue of dark energy. We don’t know why space contains this energy that makes it expand at a faster and faster rate, but something about how the universe was set off seems to have that built into it. We don’t know how or why. It is truly perplexing. 4. Then there’s the whole issue of cosmic inflation. The uniform nature of our universe, its homogeneity, suggests that shortly after the Big Bang there was a burst of cosmic expansion where space tore apart from itself much faster than the speed of light. If that’s true, we want to know why and how that happened and if that had anything to do with these other mysteries. Did inflation leave the universe in a state that gave it the right amount of dark energy or does it explain how dark matter was formed and why it is so elusive? Does it explain why matter beat out antimatter somehow? Get the weekly Five Books newsletter We don’t know the answers. Don’t expect to read my book and get the answer in the final chapter. It’s not that kind of mystery. But all that stuff together points to something being incomplete—or maybe just flat out wrong—about the way we’re thinking about the first millionth/billionth/trillionth of a second after the Big Bang. Yes, there’s all this exciting new stuff to talk about, and I happen to work in an area where I know as much as anyone about these mysteries. I thought I could tell the story well, but there’s also the narrative that these things might be interconnected. I really do think it’s plausible, and perhaps even likely, that that’s true. I like to use this analogy, where I ask other physicists as a hobby, ‘What do you think it would be like to be a physicist in 1904?’ I picked that year because it’s a point in time where physics seemed to be all wrapped up. We had this incredible paradigm of Newtonian physics, which just worked. There were a few questions that remained like, ‘How do atoms work?’ ‘What’s the nature of light? Why does it always travel at the same speed?’ Mercury’s orbit also wasn’t quite right. We didn’t understand how the sun worked, how it generated so much energy. People just thought of these things as loose ends that would all be wrapped up in the years ahead. “We can go forward in time. We know how to do that, it just involves travelling near the speed of light” But, in 1905, Einstein introduced relativity and the first ideas of quantum physics. These things didn’t just build upon Newtonian physics, they tore Newtonian physics to the ground, to rubble, and then built an entirely new structure that has been the foundation of physics ever since. I don’t know, but maybe we’re in the 1904 of cosmology right now and we’re going to tear down everything we think we know to the ground and build something entirely new. I think it truly is. In 1900 physicists would think it was a silly question to ask scientifically. ‘What do you mean the origin of the universe? There’s no such thing as that in physics.’ They thought of space as a fixed, static thing that objects can move through. If you think of space that way, it can’t do anything. Einstein showed us it was not like that at all: space can expand, it can contract, it can warp, it can curve, it can begin, it can end. And, for that reason, cosmology was conceptually possible after his theory came out. There is a big bag of tools but, yes, particle accelerators are incredibly important. They are our best way to learn what the laws of physics are, especially the laws of physics that dictated how matter and energy behaved in the first fraction of a second. We also use a variety of telescopes. I don’t just mean what most people picture as a telescope—a long tube with some mirrors or lenses in it. Sometimes we use things like that, but we also use telescopes that are on satellites. Some of them detect things that aren’t even light, like neutrinos or cosmic rays. The ones that can detect light don’t just detect the light our eyes can see, they detect X-rays and gamma rays and microwaves and infrared and UV radiation, all these things. We put all this information together in a coherent way that makes sense together, with just a few loose ends…"