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Showing posts with label string theory. Show all posts
Showing posts with label string theory. Show all posts

Monday, April 30, 2012

Could we observe the multiverse? - Brian Greene

Brian Greene
From Scientific American article: http://www.scientificamerican.com/article.cfm?id=multiverse-the-case-for-parallel-universe.

"Any theory in physics stands or falls depending on whether its predictions agree with the data. But how can we verify the existence of other bubble universes?

Is the multiverse theory unscientific, because it cannot be tested, even in principle?

Surprisingly, observational tests of the multiverse picture may in fact be possible. A collision of our expanding bubble with another bubble in the multiverse would produce an imprint in the cosmic background radiation—a round spot of higher or lower radiation intensity. A detection of such a spot with the predicted intensity profile would provide direct evidence for the existence of other bubble universes. The search is now on, but unfortunately there is no guarantee that a bubble collision has occurred within our cosmic horizon." 

This is the point that Brian Greene spends 1 minute making (@16 mins 45 s) http://www.ted.com/talks/lang/en/brian_greene_why_is_our_universe_fine_tuned_for_life.html & http://blog.ted.com/2012/02/28/the-multiverse-in-three-parts-brian-greene-at-ted2012/ (video transcript)
"explaining how it might be able to actually detect OTHER universes because of temperature differences in the cosmic macro-background radiation. Could we ever confirm the existence of other universes? 


Inflationary theory has observational support. Perlmutter, Schmidt & Riess won a Nobel Prize in Physics in 2011 http://www.nobelprize.org/nobel_prizes/physics/laureates/2011/press.html for discovering that the Universe expansion is SPEEDING UP due to Dark Energy - a type of inverse gravitation which means galaxies are repelling each other rather then attracting each other as gravitation would do.

Brian Greene says
'The Big Bang would have been so intense that as space stretched, tiny quantum jitters would have stretched from the micro to the macro world, creating a distinctive fingerprint across space - which powerful telescopes have now observed.
Similarly, we might be able to detect if one universe collided with another, we might one day detect those temperature differences." 

Greene published 'The Hidden Reality: Parallel Universes and the deep laws of the cosmos' in 2011 and the Penguin paperback in Feb 2012 http://www.amazon.co.uk/The-Hidden-Reality-Parallel-Universes/dp/0141029811/ref=sr_1_1?s=books&ie=UTF8&qid=1335814001&sr=1-1

Thursday, July 10, 2008

Susskind Quashes Hawking in Quarrel Over Quantum Quandary

According to String Theory the tiniest dimensions of space are curled up and twisted into an analog of the Double Helix. Interesting analogy.

by California Literary Review
Thanks to SPS for the link.

http://calitreview.com/790

Susskind Quashes Hawking in Quarrel Over Quantum Quandary

CLR INTERVIEW: Leonard Susskind is the Felix Bloch Professor of theoretical physics at Stanford University.
His new book, "The Black Hole War" (HASSERS Amazon bookstore), details his battles with Stephen Hawking over the true nature of black holes. The resulting theory postulates that every object in our world is actually a hologram being projected from the farthest edges of space.
Below is Dr. Susskind's interview with the California Literary Review.

Would you give us an overview of what a black hole is?

A black hole is what you get if you compress so much mass into a region of space that it collapses, under its own weight, to an infinitely small, dense, point called the "singularity." Everything that gets too close to the black hole gets sucked in, and squashed beyond recognition. There is no escape from the singularity, even for a light ray. Someone falling into a black hole might try to send a message, on a beam of light, to the outside world: "Help, I'm being sucked in." But even the light ray gets pulled back to the singularity.

There is a certain radius—a particular distance from the dangerous singularity—that I like to call "the point-of-no-return." If you accidentally pass the point-of-no-return there is nothing you can do to escape; you and all your messages will get swept to the singularity and destroyed. The point-of-no-return is also called the horizon of the black hole.

Passing the horizon seems very innocent while it is happening. It's like being in a rowboat above Niagara Falls. If you accidentally pass the point where the current is moving faster than you can row, you are doomed. But there is no sign—DANGER! POINT OF NO RETURN—to warn you. Maybe on the river there are signs but not at the horizon of a black hole.

Stephen Hawking once said something about black holes that apparently upset you. What was it?

Stephen said that when a bit of information falls into a black hole it is permanently lost to the outside, despite the fact that he also proved that black holes evaporate and eventually disappear. That claim touched off a crisis in physics, a clash of basic principles like no other since Einstein was young.


The problem that upset me is that the most basic principle of physics—the principle that underpins everything including classical physics, thermodynamics, quantum mechanics, energy conservation, that physicists have believed for hundreds of years—is that
information is never truly lost. It can be scrambled beyond recognition, but it is never completely erased.


Hawking's claim was outrageous, but he had very good reasons for it. So good that it took more than two decades to figure out why he was wrong. And the question led to a tremendous paradigm shift in the way we think about space, time, matter, and bits of information.

Why was this so important?

Well it's probably not important for curing cancer, or knocking down enemy missiles, or speeding up your computer. But it is important to the future of physics and cosmology.
The universe is controlled by two fundamental laws: Einstein's gravity theory (the General Theory of Relativity) and Quantum Mechanics. Stephen argued very convincingly that the two (GTR and QM) were on a collision course. Gravity and Quantum Mechanics were just plain incompatible. One or the other would have to give, at least by Hawking's logic.
Stephen was wrong, but his astonishing question has changed the history of physics, and there is much more to come.


So, what do you believe happens to matter sucked into a black hole?

Remember that in a monumental contribution to physics,
Hawking showed that black holes evaporate, like puddles of water on a hot day. It happens very slowly but the black hole does emit particles, and eventually disappears. The answer is that the evaporation products—the photons and other particles—carry away every bit of information, BUT in an extremely scrambled form. What we have learned is that black holes are not information-erasers but information-scramblers.


What was the final outcome of your competing theories?

The short answer is that Stephen was wrong and I was right. But that is a tremendous oversimplification and I would not like history to see it that way. Stephen asked an audacious, bold, and very brave question —do black holes erase information? Just realizing that there was a question took profound insight. It was enough to make anyone's reputation. The outcome was a whole new paradigm called the Holographic Principle. The Holographic Principle says something astonishing and completely beyond intuition. The world is a kind of hologram: an image projected from a distant mathematical film, far at the edges of the universe. To understand how we got from black holes to holograms you'll have to read my book, but here is a hint. The horizon of a black hole (a two dimensional surface like a film) somehow stores all the information that ever fell into the hole.

Where does biology fit into a theoretical physicist's thinking? Do the attempts at an elegant "Theory of Everything" include life's impulse to survive and replicate?

Physicists don't like to think that their science is anything like biology. Biology is messy, imprecise, and complicated. Physics is simple, crystal clear, and elegant, or so the argument goes. But physicists have been hit over the head with some "ugly" facts.
There are powerful reasons to believe that the universe may also be a consequence of random mutation. It sounds crackpot, or at best, like fringe speculation, but by now the idea is very firmly established in the mainstream physics and cosmology literature. That's was what my book "The Cosmic Landscape" was all about.


According to String Theory the tiniest dimensions of space are curled up and twisted into an analog of the Double Helix.
The Double Helix is a frame on which base-pairs can be arranged. And as you know, the pattern of base pairs determines the properties of a given biological entity.

Microscopic space (according to String Theory) is not a Double Helix, but something similar: a Calabi Yau manifold (don't ask).
The analog of the base pairs of DNA are called "fluxes."
The details don't matter. What does matter is that there exists an incredibly rich set of possibilities—you can call them blueprints—for the construction of a universe. And
according to modern cosmological theory, the universe is filled with sub-universes of every allowable kind, formed from a process similar to random mutation.


If this is so then the question, "Why our universe is the way it is?" may have an "anthropic" component: we live in a very rare environment where the ordinary laws are such that life can exist. Where else would we live? Where else would it be possible to ask the question?

How about consciousness or awareness? Are there any physicists who see consciousness as a distinct but interwoven part of the universe?

I suppose there are. My own view is similar to
Richard Feynman's when he was asked whether the conceptual puzzles of quantum mechanics confused him. He said that quantum mechanics was so puzzling that he wasn't even sure if there was a puzzle. There are other questions like that—questions that you can't even imagine what an answer could be like. "Why does mathematics work?" "Why does logic work?" "What is the purpose of the universe?" "What is the connection between mind and matter?" As I said, these seem like legitimate questions, but you can't imagine what answers would be like. My sense is that consciousness is one of those questions.

Incidentally, I don't mean to imply that these questions will never get answers; just right now I don't have a clue.
But then again I am not a licensed cognitive scientist.

If I understand it correctly, you've recently written that our universe may just be one of an infinite number of universes, each with unique properties or laws of physics. Is this where you think our knowledge is headed and if so, do you find that discouraging or encouraging in terms of what we can ultimately know about the universe?


First of all I am not in the least bit alone in this view, nor am I the originator of it. It has been around for a long time. But since I wrote "The Cosmic Landscape," (HASSERS Amazon bookstore) it has practically become the conventional view.

As to whether I find it discouraging or not—no—not at all. There are people who do, but I think they are victims of their own prejudices and hopes. The universe is far more interesting and challenging than we imagined.
The next generation of physicists and cosmologists will have the fun and excitement of discovering the right mathematical formulation of a "multiverse." Finding observational (astronomical?) ways to confirm that we live in such a diverse world is another challenge. Only the old fogies who thought that physics was almost finished are disappointed. The only thing that I would find discouraging would be that we run out of questions.


Heard any good theoretical physics jokes lately?

Yup, and you'll find them in my book.

Wednesday, September 12, 2007

"The Elegant Universe" -A Galaxy Insight

reposted from:http://www.dailygalaxy.com

September 12, 2007

"The Elegant Universe" -A Galaxy Insight


“How can a speck of a universe be physically identical to the great expanse we view in the heavens above?”

Brian Greene, The world's leading string theorist, Professor of Physics at Columbia University and author of The Elegant Universe and The Fabric of the Cosmos: Space. Time. And the Texture of Reality.

The stunning complex of coincidences that render the universe fit for life and intelligence
, is captured by British astronomer Sir Martin Rees: "There are deep connections between stars and atoms, between the cosmos and the microworld."

Scientists have been aware of this great puzzle for decades, but

two recent discoveries have given the quest for an answer to why the universe seems life-friendly a new set of urgency.
The first was the discovery of Dark Energy—although the predominant constituent of the universe—its strength is so astonishingly small that were it even slightly stronger, the universe would be void of galaxies, solar systems and life.
The second great discovery, which is yet to be proved, is M-theory, the reincarnation of superstring theory which posits that the subatomic world are just different modes of vibration of tiny one-dimensional strings of energy
of which only a fraction corresponds to the sub-atomic particle world described by the Standard Model.

For string theory to have the kind of acceptance of general relativity, it's got to make a prediction that is borne out by some experiment.
And as yet, we haven't quite gotten to the stage where we can make definitive predictions which, if they're found, the theory was right, and if they're not found, the theory was wrong.

But we have gotten to the stage where we can make some rough predictions for things that might happen at the accelerator built near Geneva, Switzerland, called the Large Hadron Collider.

If some of the predictions that string theory says might happen are borne out through experiment at that accelerator, then it's quite possible that string theory would be as accepted as general relativity.

However, Steve Giddings a theoretical physicist at the University of California states that:

"No longer can we follow the dream of discovering the unique equations that describe everything we see, and writing them on a single page. Predicting the constants of nature becomes a messy environmental problem. It has the complications of biology."

Posted by Casey Kazan.

Story Links:

BBC Super-String Theory -A breathtaking video about the Grand Unification Theory for the universe and its implications on our understanding of the universe's nature
String Theory -"The Elegant Universe"