The structure of the universe as we are coming to know it is far stranger and perhaps even more fanciful than the notion of a world supported by a great teetering tower of gargantuan testudines.
Tonight at 9PM ET/PT on PBS's legendary NOVA program, acclaimed theoretical physicist, author, and "science personality" Brian Greene begins a four-part series called The Fabric of the Cosmos, based upon his book of the same name, which takes us on a fascinating excursion to the inner and outer edges of reality to gain insight into state-of-the-art thought on "What Is Space?" (11/2), "The Illusion of Time" (11/9), "Quantum Leap" (11/16), and "Universe or Multiverse?" (11/23).
I had the pleasure of speaking with Greene by phone after previewing the "What Is Space?" and "The Illusion of Time" episodes.
Eric Olsen - I've always been fascinated with ideas, though more inclined toward philosophy than physics because I'm not that great at math. It seems to me that theoretical physics is philosophy with math.
Brian Greene - I'd go further than that. It's philosophy in the questions that are asked - it's math in terms of the analysis it uses, but it's predictions about the real world that should be testable that allows us to test whether it's right or not. And that's the key feature that distinguishes it from other areas.of philosophy.
EO - What was your path to becoming a theoretical physicist?
BG - I was always pretty good at math when I was little. But when I was 13/14/15 I had the kind of questions most teenagers have: Why am I here? What's it about? All that sort of stuff.
It began to occur to me that people have been asking those questions for a really long time and there's no real answer, which means that searching for an answer might not be the best route. Maybe the best thing is to try to understand the questions: How did we get here? How did the universe come to be? What is the universe made of? What are the forces at work in this strange place where we find ourselves? And that is what physics is all about - trying to get some insight into those deep questions.
EO - I find the current state of theory to be truly mind-boggling. When you left me at the end of the first episode -- "What Is Space?" -- with the notion that 3D reality as we know it may in fact be the projection of a 2D film around the outside of the universe, I hadn't heard that one yet! How long has that idea been around? Can we hear a little more about that?
BG - This idea has been bubbling up for decades but it's been only recently that it's got to a point where people are taking it very seriously. It comes largely from the study of black holes. There was a big controversy for many years as to what happens when something falls into a black hole.
Stephen Hawking thought, "It's gone, forget about it. All the information it has is wiped clean from the universe."
Other physicists like Lenny Susskind, who appears on the program, and Nobel Prize winner Gerard ’t Hooft didn't believe that. They thought somehow the information would still be with us. If you drop an encyclopedia into a black hole, the information in that encyclopedia remains in the universe.
There was a stalemate for a long time, but there is now evidence from math that the information of anything you drop in a black hole gets smeared across the outside of the black hole. So the physical object may fall in, but the information it contains doesn't get lost - it hovers on the outskirts.
That leads to the strange idea that we end the first program with, which is if it's the case that stuff that falls into a black hole can be described in terms of data on the outside of a black hole. Well, we are stuff, and we are in the inside of the universe, therefore maybe we are described by information that exists on the outer edge of the universe, that we are holographic projections in the sense that we are information on that thin bounding surface.
EO - Does that impact the "meaning of life"?
BG - For me, it enriches meaning because it establishes that there is so much more to the world than you would think based upon everyday experience. Everyday experience would suggest that all the stuff around us is real, it's solid, and that's all there is to reality: the stuff that we see.
But for hundreds of years, science has been teaching us that there is more to reality beyond what you can see, and if this holographic idea is true, it's taking that notion to the next level! It's saying that not only is there more to the universe than we see, but what we're not seeing is decidedly strange - that reality may float around us on this distant bounding surface and we're just a figment of that reality.
How mind-boggling is that?
EO - Very! Doesn't something have to energize a hologram in order to create the 3D image? What is energizing the outside of the universe to create the illusion of all of us?
BG - Use of the term "hologram" is a very good visualization and metaphor for what's going on. It isn't literally that every aspect of an actual hologram applies in this context.
It's not like you're shining a laser from outside the universe into the hologram creating 3D reality. It's that the laws of physics themselves are enough to energize this information. The laws of physics, the math as we understand it, brings that reality that's hovering on that distant surface to life within the realm we are now experiencing. You don't need anything else besides the laws of physics for that reality to pop up.
EO - Do you think that if this is true, it's a fundamental truth, or are there other mind-boggling layers of reality beyond that?
BG - History t eaches us to be very careful about speaking of "final truth" and "final realities" because every time we've thought we had it all figured out, there was some new breakthrough that required us to expand our understanding further and often change our understanding dramatically. It happened with relativity. It happened with quantum mechanics. It happened with cosmology, the Big Bang - all these sorts of wondrous ideas.
So, if this new idea of holography is true, my guess is that it will be part of a yet deeper story yet to be written, a fantastically interesting stepping stone toward that fuller reality that we will come to in time.
EO - Is there a link between a universe with information smeared across it boundary film and the possible multiverses discussed in program four?
BG - They are related. In the programs we don't draw a sharp link between them, but for instance, I have a recent book called The Hidden Reality, which explores the whole idea of the multiverse in all its guises in great detail. But the "Multiverse" program is exploring cosmology, the Big Bang and its more refined version called the Inflationary Theory, and recognizing that mathematical structure is suggesting that there may not have been only one Big Bang.
There may have been many Big Bangs, each giving rise to its own expanding universe, with our universe being one expanding bubble in a big cosmic bubble bath of universes. That's what's in the final program.
EO - Any surprising details that may come out in that episode?
BG - (Laughs) Yep. One of the more shocking conclusions of the multiverse picture that we have come to through the methematical analysis is that if it's right, there are versions of us out there in other universes having this very conversation right now. There are versions of us out there having variations on this conversation, and there are variations of asll possilbe manner consistent with the laws of physics taking place out there in this wider cosmos.
So it's not just that there would be other universes, it's that some of these universes would be populated with copies of us.
EO - I have a lifelong fascination with time, the nature of time, the fluidity of time and I thought you did an excellent job of boiling down the issues of time in the second episode.
You allowed me to come away with bullet points about time and how it works: that entropy, which began with the Big Bang, gives time its direction. And the fact that by using current theory, we should be able to go forward in time but probably not backward in time.
If we send ourselves forward in time, does that mean we can't go back to where we started?
BG - It's not definitively ruled out, but most of us don't think it's possible to go back. Most of think going forward in time is compatible with the laws of physics - in the program we do it by hanging out near the edge of a black hole. But heading back to where you started from, probably not possible.
EO - And you feel this way because of the fact that we haven't seen any evidence of people coming back to visit us from the future?
BG - That's partly true. The other part of it is the only viable proposal that has received attention is this wormhole idea. And when we studied the math behind wormholes in more and more detail, it's nearly impossible for that idea to work.
It's very hard to keep a wormhole open. There are feedback mechanisms similar to where you put a microphone near a speaker and the sound keeps rushing around getting louder and louder. Energy can rush around and around a wormhole from the past to the future back to the past and so forth causing a wormhole to become destabilized.
For all these reasons, it seems highly unlikely that using a wormhole to travel to the past is viable. Moreover, no one has ever seen a wormhole.
EO - How does entropy fit into that then, giving time its arrow? Is that part of the reason it might not be possible, because there is that arrow?
BG - I don't think so. You can write down self-consistent scenarios where the arrow of time does what it always does in the sense that candles burn and they don't unburn. Eggs break and they don't unbreak. And yet, in principle you could still have a wormhole that allowed you to jump to the past where, when you got to the past you'd still see eggs break and not unbreak and still see things evolve forward in time even though you had taken a giant step back in time.
So, they are two related but separate ideas. The arrow of time is more speaking to why do things unfold in one direction and not the reverse. The possibility of time travel is whether you can step over large swaths of time going forward or going backwards even though you wouldn't be affecting entropy at all in that particular journey.
EO - As I understand entropy, it's kind of a meta-law because there seems to be lots of action that is contrary to entropy, ie things becoming more rather than less organized, at least for a time.
BG - That's right. Entropy is a meta-law in the sense that the underlying physical laws -- Newton's, Einstein's, Maxwell's -- are the laws that govern how the particles move. The particles themselves don't care very much about order vs disorder. But there is this meta-law where find that almost all evolution given by those underlying microscopic laws do increase disorder.
But the point you're making is a good one too. There are places where entropy goes down. When you eat food and your body creates increased order so that your muscles and bones strengthen and grow. At the very same time that your body is undertaking those entropy decreasing processes, your body is giving off heat that is causing the air molecules around the room to bounce in a haphazard way - there is a big domino effect.
So, for every process that decreases entropy, there's always a corresponding process that increases entropy by an even bigger amount. In the big picture, entropy is always going up even though locally entropy can go down.
EO - Like islands of order in a sea of entropy? Organisms themselves are islands of order, right?
BG - Yes. We are organisms that survive on order and therefore we are always creating an orderly structure within ourselves at the expense of the environment. It's Darwinian natural selection. You have random physical processes taking place, some of which creates structures that are more stable and better able to reproduce and create more of themselves. And over time, those structures "win" in the sense that there are more and more of them.
How does that fit in with entropy? These organized structures are emerging in a form that increases overall entropy of the surroundings - the net entropy is going up even though there are orderly objects appearing out of what appears to be disorder.
EO - Amazing! One more topic: what's the latest on dark energy?
BG - All the data we have so far is pointing toward simplest explanation, which is Einstein's old idea of a "cosmological constant," an indelible property of space that space has an intrinsic elasticity that doesn't change over time and is a part of the fabric of space. That may be what dark energy is, and it's driving the universe to expand ever more quickly.
If the dark energy is NOT constant, as Einstein theorized it was, if its strength increases over time, which is quite possible, then the far future would be very different. The repulsive force would drive galaxies, stars, planets, and everything, apart, and ordinary matter would eventually be ripped apart also. And that would certainly be an interesting end to the story.
EO - Unless we find our way to a different universe!
BG - Correct.
The Fabric of the Cosmos also comes to DVD and Blu-ray on November 15.