An elegant multiverse? Professor Brian Greene considers the possibilities

Mar 22, 2011 By Bridget O'Brian

You might think it’s hard to have a conversation with theoretical physicist Brian Greene. His research specialty is superstring theory, the hypothesis that everything in the universe is made up of miniscule, vibrating strands of energy. Luckily for an interviewer, Greene has a knack for explaining difficult concepts to non-scientists.

His first book, the best-selling The Elegant Universe, which explains the quest to unify all the laws of nature, was a finalist for the Pulitzer Prize and led to an award-winning PBS series. He is a co-founder of the World Science Festival, an annual event in June whose aim is to make “the esoteric understandable and the familiar fascinating,” which pretty much sums up Greene’s modus operandi.

“Science is a living, breathing, exciting, evolving subject,” he says. “A large part of my motivation in reaching out to a general audience is to show people that science is not this finished subject where all of the results are in these thick textbooks that you lug around when you’re taking a science course.”

Greene, 48, grew up on the Upper West Side and spent many a rainy day at the Hayden Planetarium, when it was a dark and musty place and not the shiny glass cube it is today. “That definitely played a part in my excitement for these ideas.” But it was the pure beauty of mathematics that really grabbed him.

“As a kid I was playing with numbers all the time,” he says. “And when I learned that those numbers could be more than a game, those numbers could actually describe stuff that was out there in the real world, that’s when I was hooked for good.”

His latest book, The Hidden Reality, explores another mystery: whether there are other universes beyond ours.

Q. Your new book talks about the concept of a multiverse. Can you explain what that means?

When we hear the word “universe,” we think that means everything: every star, every galaxy, everything that exists. But in physics, we’ve come upon the possibility that what we’ve long thought to be everything may actually only be a small part of something that is much, much bigger. The word “” refers to that bigger expanse, the new totality of reality, and our universe would be just a piece of that larger whole.

Q. So what kinds of other worlds might there be?

Scientists have many proposals. In some, the other universes have the same laws of physics and the same particles making up matter. So except perhaps for some environmental differences, pretty much what we see here is what happens there. In some multiverse proposals, the other universes could be radically different from what we know, the particles could be different, the laws of physics could appear different. And in others—ones that frankly don’t compel me—even the kinds of mathematics that govern the physics in those realms might be different from the math that we are familiar with.

Q. Do you think that one of the multiverse theories will be proven in your lifetime?

You never know when that big breakthrough is going to happen. I could come to work tomorrow, go to the website that posts all of the physics papers that people completed in the previous day, and there could be the paper that shows how to test , or how to test some of these multiverse proposals. Could it be tomorrow? Could it be 10 years from now, or a hundred years? That’s part of what the excitement is.

Q. Do you have a favorite among the theories?

All of the ideas are compelling and come from a sober assessment of certain mathematical developments. Which do I think has a chance of being experimentally verified in the next few decades or within our lifetime? I would suggest the brane multiverse, in which our universe is envisioned to reside on a giant membrane, an ingredient that comes out of string theory. It’s actually a three-dimensional membrane, but thinking in two-dimensional terms is easier. Think of our universe as if it were a huge slice of bread, with all the stars and all the galaxies sprinkled across its surface. The math of string theory suggests this picture, along with the possibility that there are other universes, other slices of bread, all constituting a big cosmic loaf. This is an idea that might be testable at the Large Hadron Collider, the big accelerator in Geneva, where protons are slammed against each other at fantastically high velocity. Calculations show that some of the debris created in those collisions might be ejected off our universe, off our slice of bread, and if so, that debris would carry away some energy. Scientists will look for these missing energy signatures for evidence that we live on one of these membranes and that there are other membranes out there.

Q. How does string theory research tie in with Einstein’s search for a unified theory?

Einstein’s goal was to find what he called a unified theory of physics. By that he meant a theory that might embrace all the known laws of physics and describe them within a single mathematical framework. He didn’t find the unified theory, and since his day we’ve recognized that in some ways the problem is even more difficult than he envisioned. He was really only aware of the force of gravity and the electromagnetic force. We now know about the strong nuclear force and the weak nuclear force, operating inside of atoms according to the rules of quantum mechanics. We believe string theory may be the unified theory that Einstein was looking for. It unites quantum mechanics and gravity, and has the capacity to embrace the strong nuclear force, the weak nuclear force, the electromagnetic force, all the particles of matter in one coherent mathematical structure.

Q. What would you say is the biggest misconception people have about physics?

One significant difficulty people have is in understanding how mathematics gives rise to these strange ideas. You need to realize that when we physicists look out in the universe, we see patterns, we see repetitive phenomena, and math is the language of pattern. When you teach little kids to count by twos, and they can keep on going, they see the pattern. Just as the little kid can say, “Oh, after 10, it’s 12,” we can look at our mathematics and say, “Look, after that universe, there’s another.” We can see it in the pattern encapsulated in the mathematics.

Q. Can you provide examples of how string theory could be tested?

The full name of string theory is superstring theory. The “super” refers to something known as supersymmetry, a kind of mathematical pattern which implies there should be a whole class of particles, called supersymmetric particles, that we have not yet seen. The Large Hadron Collider may have enough energy in its collisions to conjure up those particles. If they’re found, will it prove string theory? No, but it will be a strong piece of circumstantial evidence. Another way of testing string theory could be seeing if the collisions produce microscopic black holes. When people first heard about this possibility back in 2008, it generated some degree of public anxiety—the thought being that these black holes might swallow Geneva and then engulf the world—which is not a real worry at all. But string theory does suggest that in these collisions, little black holes might be formed. If they are, again you have a piece of circumstantial evidence. The missing energy experiments I mentioned before are also worth adding to the list—these experiments could test for the existence of extra dimensions and string theory’s brane model of our universe.

Q. Are these theories applicable in the real world? If true, could they affect everyday life in some meaningful way?

What if I were to ask you, What is the concrete application of Beethoven’s Fifth Symphony? Or the Mona Lisa? Or the works of James Joyce? It’s a little hard to find concrete applications. But do they enrich life, are they part of what makes us excited to get up in the morning? Yes. I think these ideas in physics can paint a large view of reality that allows us to place our piece of it in a much grander context. And that’s deeply enriching. Let me also note this: If, 80 years ago, you had asked Niels Bohr, “Niels, this quantum mechanics stuff that you guys are going on about, what’s it good for?” he probably would have said, “Well, it’s not really going to change everyday life. We’re talking about atoms and subatomic particles.” But now we’ve harnessed the understanding of quantum mechanics, and because of that, you have a cell phone and a personal computer and your life may be saved by an MRI machine. Quantum physics gave rise to the integrated circuit, and the integrated circuit is in all of these devices, which is just to say that you don’t know where basic research is going to lead. It may take 80 years, as with ; it may take 500 years; but when you deeply understand something, you can begin to manipulate the environment in ways that can revolutionize everyday life.

Q. How do you feel about the general attitude toward science?

In the broader public, there is significant resistance to engaging with science. This is largely due to the way that many have encountered science in the classroom, where there’s a tendency to focus on details without an equal focus on the big, wondrous scientific ideas—the very ideas that can inspire passionate interest in learning those details. We need to embark on a radical cultural shift in which science takes its rightful place alongside music, art, theater and literature as an absolutely indispensible part of a full life. We need to make clear that science is not something that you can willfully ignore. All of the major decisions going forward, from stem cells to nuclear proliferation to nanotechnology to genetically modified food to alternative energy sources to climate change, have a scientific component. How can you be part of a democracy if you can’t participate in the discussion about these ideas?

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User comments : 26

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Mike_nine1962
2.3 / 5 (4) Mar 22, 2011
I sent an email to Stephen Hawkins in 2006 entitled Myth or Multiverse, in which I also suspected the big bang may have happened many times before. I would not pretend to understand why matter in universe is apparently accelerating however if we are one of many universes we may be enclosed in some form of shell or energy which maybe be the elusive dark matter I've heard about. It may not be possible to for a long time, prove the existence of what is at the extremities (possibly and enclosing energy shell / matter) of our universe, other than it may be causing the acceleration observed.
Jaeherys
2 / 5 (1) Mar 22, 2011
Afaik, the edge of our universe would be surrounded by a quantum hologram and the repulsive force would be caused by the quantum vacuum or cosmological constant which is 10^-120 orders of magnitue smaller than the reduced Planck constant, if I remember correctly; on a side note, the quantum vacuum energy is supposed to be equal to the cosmological constant which physicists haven't been able to accomplish yet as the value they get is enormous.
DamienS
4.3 / 5 (4) Mar 22, 2011
I think string theory could be in for a shakeup in the next few years. If the LHC doesn't find evidence to support SUSY, it would be a major blow for S/M-theory (and standard physics, aka the hierarchy problem).

Of course, there might be wiggle room by noting that the super-symmetric stuff may occur higher up the energy range, just outside of LHC's capabilities, but that would certainly hose down support for string theory even further. Still, interesting times ahead.
Jaeherys
4 / 5 (1) Mar 22, 2011
From what I have read on the subject of supersymmetry was that it was used by string theorists to simplify the math so that it was possible to further develop the theory, as it was just too difficult otherwise. Also that if our universe really was symmetric, we would have a cosmological constant of zero, meaning our universe never would have undergone inflation in the first place. What am I missing?
DamienS
4.4 / 5 (5) Mar 22, 2011
Also that if our universe really was symmetric, we would have a cosmological constant of zero, meaning our universe never would have undergone inflation in the first place.

There are various flavors of super-symmetric theories, and yes, some do require the cosmological constant to be zero, but not all of them have this requirement. Also, I don't think you can draw a correlation between the currently observed cosmological constant and the inflationary period, simply because we don't really know what triggered inflation in the first place (hypothetical inflaton field not withstanding).
nxtr
2.5 / 5 (4) Mar 22, 2011
it seems obvious that the big bang happens every x billion years as black holes scoop up the dust and finally find each other again to re-bang. Our job is to figure out how to stand to the side when it happens next time.
abhishekbt
5 / 5 (1) Mar 23, 2011
@Nxtr: Dream on Man! Very vivid imagination and a great plot for the next hollywood movie.
ubavontuba
1.8 / 5 (8) Mar 23, 2011
If Brian Greene really wants to connect science with the multitudes, he needs to write "The Multiverse Rap"

It goes something like this:

The universe in a multiverse
the multiverse holds the universe

Big bangin'
we're hangin'
with Brian Greene
and the multiverse!

Big bangin'
we're hangin'
with Brian Greene
and the multiverse!

There's Susy, she's pretty
she knows the nitty gritty
symmetrical, electrical
a mathematical spectacle!

and so on...
Raygunner
not rated yet Mar 23, 2011
Could it be that particles simply behave differently when subjected to the tremendous energies of the LHC? In other words, instead of exotic new particles being created in these collisions, could existing particles (quarks, etc) simply act differently when TeV's of energy are applied? Just wondering that's all.
dankgoat
1 / 5 (4) Mar 27, 2011
Could it be that particles simply behave differently when subjected to the tremendous energies of the LHC? In other words, instead of exotic new particles being created in these collisions, could existing particles (quarks, etc) simply act differently when TeV's of energy are applied? Just wondering that's all.


Yes, it is a big waste of time and money and smart people. It's like the wall street of science projects.
Bigblumpkin36
2.3 / 5 (3) Mar 28, 2011
We live in a black hole i always thought
atombat
not rated yet Mar 28, 2011
We live in a black hole i always thought


I agree with this assumption in some ways.
M-Theory suggests that a Big Bang is created when 2 branes collide, is this like when a super massive star creates a black hole when it dies? (All the matter from the dying star is crushed into a singularity Cutting it off from the outside universe?), could this be a new universe, just several million orders of magnitude smaller relative to our perception?

The Holographic Universe theory looks very similar to the event horizon of a black hole, similar to what we may see at the edge of our universe?
Also our matter cannot escape our brane just like matter cannot escape the singularity of a black hole (apart from higgs bosons which are independant from the branes, so could they, move through black holes just as easily?)
Just a layman's point of view. I'm not a scientist/physicist,
I just enjoy reading the theories. :)
atombat
not rated yet Mar 28, 2011
it seems obvious that the big bang happens every x billion years as black holes scoop up the dust and finally find each other again to re-bang. Our job is to figure out how to stand to the side when it happens next time.


If we're "inside" there is no "aside".

Wouldn't Hawking radiation lead to black hole evaporation being a small event compared to a Super Nova (the inhabitants inside a black hole would see this as a "big bang", well they wouldn't see it, but they/us would be the result) and the black hole evaporation would be more like the universe ending, (heat death of the universe but to us on the outside sped up 100 trillion times, those on the inside, well there wouldn't be anybody, they would've died of trillions of years ago, but to that universe wouldn't the heat death seem to last trillions of millennia, due time dilation caused by gravity...?) Just had to get these ignorant layman's ramblings of my brain. :)
Modernmystic
1 / 5 (2) Mar 28, 2011
If we're "inside" there is no "aside".


The branes are "aside" in M theory.
atombat
not rated yet Mar 28, 2011
If we're "inside" there is no "aside".


The branes are "aside" in M theory.


But this is what I mean, this would make us inside the brane that is aside the other branes.
Modernmystic
1 / 5 (1) Mar 28, 2011
If we're "inside" there is no "aside".


The branes are "aside" in M theory.


But this is what I mean, this would make us inside the brane that is aside the other branes.


Then aside would be the medium the branes move through...

But if branes collide aside could still be on the brane just away from where they touch when they collide as well. Unless they collide "everywhere" on the brane at once.

Also "aside" could be on another non-colliding brane.

Plenty of asides here...
atombat
not rated yet Mar 28, 2011
...Unable to leave the Brane, unable to escape the Black hole, until the heat death comes long after. A brane within a brane within... so on, ad nauseum/astra etc....
atombat
not rated yet Mar 28, 2011
If we're "inside" there is no "aside".


The branes are "aside" in M theory.


But this is what I mean, this would make us inside the brane that is aside the other branes.


Then aside would be the medium the branes move through...

But if branes collide aside could still be on the brane just away from where they touch when they collide as well. Unless they collide "everywhere" on the brane at once.

Also "aside" could be on another non-colliding brane.

Plenty of asides here...


..within Infinite branes/black holes, aside infinite branes/black holes/multiverses, like some super symmetrical infinite Mandelbrot pattern, symmetrical on every level Maybe? This could go on for ever. :)
nayTall
not rated yet Mar 28, 2011
We're just the flickering memory of some being's thought process, man. All we exist for is to help make a decision. Hopefully, it's a good one.
TabulaMentis
1 / 5 (1) Mar 30, 2011
But this is what I mean, this would make us inside the brane that is aside the other branes.
I think the word you are looking for is "Bulk." Research "Brane Cosmology" to see if that is the case.
TabulaMentis
1 / 5 (1) Mar 30, 2011
Quotes from Brian Greene:
And in othersones that frankly dont compel meeven the kinds of mathematics that govern the physics in those realms might be different from the math that we are familiar with.

All of the ideas are compelling and come from a sober assessment of certain mathematical developments.

Do not those two statements contradict each other?
We need to embark on a radical cultural shift in which science takes its rightful place alongside music, art, theater and literature as an absolutely indispensible part of a full life.

Brian forgot to mention religion. That may be where the possible contradiction above originates?
TabulaMentis
1 / 5 (1) Mar 30, 2011
Another quote from Brian Greene:
How can you be part of a democracy if you cant participate in the discussion about these ideas?
The U.S. needs to teach kids/young adults grades preschool thru 12th math, science and engineering whether they want to learn it or not! Once they learn how to upload education directly into their minds using quantum mechanics, then they will no longer have to do things the hard way.

A catalyst to get things moving faster is to throw religion into the mix and a whole lot of people will begin to take notice!
loreak
not rated yet Mar 30, 2011
Basically when our brane collides with the parallel universe brane both our universes will shatter. I learned this from Professor Walter Bishop. PETER MUST NOT ACTIVATE THE MACHINE
TabulaMentis
1 / 5 (1) Mar 31, 2011
It is interesting how the title of this article is mocking Brian Greene's book "The Elegant Universe" with "The elegant multiverse?" Maybe the author of this article should have come up with a better word for "multiverse" like the following words: metaverse, venoverse or omniverse. Omniverse is my favorite one. Multiverse can sometimes be confused with religion.
atombat
not rated yet Mar 31, 2011
But this is what I mean, this would make us inside the brane that is aside the other branes.
I think the word you are looking for is "Bulk." Research "Brane Cosmology" to see if that is the case.


Yeah Bulk is probably the word. But what surrounds those Bulks, I'd love to say there are more layers on top of the other layers (beyond the 11 dimensions), I don't know if the maths support such an idea? ...Or "Clump", I like this word also. :)

TabulaMentis
1 / 5 (1) Mar 31, 2011
Yeah Bulk is probably the word. But what surrounds those Bulks, I'd love to say there are more layers on top of the other layers (beyond the 11 dimensions), I don't know if the maths support such an idea? ...Or "Clump", I like this word also. :)

The universe contains the bulk. Maybe you might want to call the bulk a metaverse because the term bulk is related to string theory/M-theory. I prefer omniverse because that would contain all possibilities.

See Brian Greene's new book for more info: The Hidden Reality: Parallel Universes and the Deep Laws of the Cosmos

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