Skip to comments.In search of hidden dimensions
Posted on 01/09/2005 12:26:51 PM PST by snarks_when_bored
Nature 433, 10 (06 January 2005); doi:10.1038/433010a
In search of hidden dimensions
So far, string theory has defied experiments, but Nima Arkani-Hamed thinks he has found a way to put the idea to the test. Geoff Brumfiel finds out how.
|J. IDE/HARVARD UNIV. NEWS OFFICE
String fellow: Nima Arkani-Hamed hopes that particle-collision experiments will show that gravity leaks into other dimensions.
But ask Nima Arkani-Hamed, a physicist at Harvard University, and he will give you a far closer date: 2008. That is when the first results from the Large Hadron Collider, the world's most powerful particle accelerator, are expected to be released by CERN, the European particle-physics laboratory near Geneva, Switzerland. And if Arkani-Hamed's predictions are correct, then that is when an experiment will detect the first evidence to support string theory a vision of the cosmos that has never been verified experimentally. "The field is going to turn on what happens at the collider," he says.
Pacing his sparse Harvard office, the 32-year-old physicist drinks no less than six cups of espresso during our hour-and-a-half interview, as he tries to explain why he thinks string theory can now be tested.
String theory emerged in the 1980s as a way to answer questions that still baffle modern physics, such as why is gravity so much weaker than other fundamental forces? By imagining that everything is composed entirely of strings ten billion billion times smaller than atomic nuclei, theoretical physicists were able to create a model of the Universe that unified all fundamental forces into one, and described most of the particles we see today. Unfortunately, these strings are far too small to be detected by even the most powerful particle accelerators. And so, critics say, they are more philosophy than physics.
Arkani-Hamed's ideas have very little to do with strings themselves. Instead, he is hoping to detect the extra dimensions predicted by the theory, which, like the strings, are thought to be vanishingly small. But in 1998, Arkani-Hamed and his colleagues published calculations showing that some of these extra dimensions might be as large as a millimetre (N. Arkani-Hamed, S. Dimopoulos and G. Dvali Phys. Lett. B 429, 263272; 1998). Such large dimensions, they argued, have escaped detection because everything we know except for gravity is confined to the three dimensions of space and one of time. But gravity, they think, might be able to seep into these extra dimensions. This would explain why it seems so weak to us. And, as a result, unexpected variations in gravity could allow researchers to detect the hidden dimensions.
"It was a watershed event in the field," recalls Joe Lykken, a theoretical physicist at Fermilab near Chicago in Illinois. Suddenly, a theory that most thought could never be tested was within experimental reach. Some groups rushed to look for deviations in gravity at small scales. So far, they have nothing to report, but the hope created by Arkani-Hamed's work is enough to win him wide praise. "The word 'genius' is overused, but I think it is easily applicable in the case of Nima," says Savas Dimopoulos, a Stanford theorist and one of Arkani-Hamed's collaborators.
The son of two Iranian physicists, Arkani-Hamed was born in Houston, Texas, and grew up in Boston. After the Iranian revolution of 1979, his family returned to their homeland, but as religious fundamentalists took over the government, his father was forced to go underground and the family eventually had to flee across the border to Turkey. By 1982, Nima was living in Toronto, Canada.
Recalling his early life, Arkani-Hamed says that his time in Iran was largely a positive experience. "The strange thing is that I have mostly wonderful memories," he says. If anything, he adds, it taught him to worry less about what others thought of him. "Given that so many aspects of my life have been unusual, I've never had a problem with feeling different or being different or doing different things."
As a child, Arkani-Hamed loved physics, but he initially disliked almost everything about string theory. "String theory just seemed like abstruse junk to me," he says. "What I really liked was physics that explained things about the world around me."
That changed when he began studying quantum field theory at the University of Toronto. At first, this complex theory which underlies high-energy physics and much of string theory seemed too arcane, but as he studied it more carefully, he found a level of order and explanation far beyond anything he had learned before. "Clearly, there was something very deep going on," he says.
It captivated him, and by the time he finished graduate school in 1997, he knew he wanted to try to make string theory experimentally verifiable. He found an ally and mentor in Dimopoulos, who has devoted his career to seeking testable versions of string theory. "We believe that the only way to make progress is to take an idea, and push its consequences to find observations," Dimopoulos says.
These days, in late-night phone calls and frequent e-mails, the two are thinking about what might emerge at the Large Hadron Collider. Their current calculations show that some of the energy created by particle collisions in the machine could escape into extra dimensions, carried off by leaking gravity, if those dimensions are large enough. The result would be an apparent violation of the conservation of energy a dramatic sign that string theorists are on the right track.
Then again, they might not be. "You can spend ten years of your life and every idea you come up with can be wrong, and that's gratifying in its own way," Arkani-Hamed says. But, he adds, as he reaches his caffeine-fuelled conclusion: "If this thing turned out to be true, it could be the biggest discovery in science in, say, 300 years."
Geoff Brumfiel is Nature's Washington physical sciences correspondent.
"The son of two Iranian physicists, Arkani-Hamed was born in Houston, Texas, and grew up in Boston. After the Iranian revolution of 1979, his family returned to their homeland, but as religious fundamentalists took over the government, his father was forced to go underground and the family eventually had to flee across the border to Turkey. By 1982, Nima was living in Toronto, Canada."
Non-elitist bookmark bump.
It's not strong enough to provide a good signal. The EM spectrum is far superior.
Thanks for the ping!
Why does this guy think that a uniform distribution of matter and energy isn't the result of a random process? In many cases, this is exactly what would be predicted.
His comment about the universe being "accidental" just shows
how little our language and common understanding incorporates
all of the knowledge we do have.
One major question would be such:
Is there any such thing as an "accident?" If the universe
(no matter how many dimensions or what it is composed of)
is set on ONE solitary physical course, then the concept of
an accident(meaning something happened that wouldn't
"normally" happen) COULDN'T occur at all. EVERYTHING
would be an outworking of the physical plant we find ourselves
in...(e.g. every event which occurs is based on some
physical process which was initially set in motion when the
universe (or multiverse, if you will) began.
This of course raises questions about our belief, that
we can understand "NATURE" at it's core, since our very
thoughts could be considered as outworkings of the
physical processes initially set in motion when the universe
(or multiverse, if you will) began.
"I think, therefore I AM....er....do I really think?", would be
the edited version of that famous philosophical statement.......
You're right about height, width, depth and time being the standard four dimensions of spacetime. But gravity is not a dimension; it's one of the four fundamental forces, the other three being electromagnetism, the strong nuclear force and the weak nuclear force.
however, observation has shown that the structure of space time is bent into "gravity wells" around massively large objects. Here are two sentences. 1.)Space tells matter how to move. 2.)Matter tells space how to bend. Sentence one describes "height, width, depth and time being the standard four dimensions of spacetime." Sentence one describes how we understand reality. However, all four dimensions seem to be subject to something else described in sentence two. The bend or gravity. But why is this bending of space described as a force rather than the character of space itself. It doesn't seem as if space is empty. Rather it seems that if space can bend than it is more like a material.
Either that or our notion of dimensions is a function of newtonian mathmatics. We're biased or our point of view is in favor of space time rather than matter time--if there is such a beast. I'm no mathmatician but I've heard recently some speculation at free republic that this bias had something to do with Newton's work and that it could be rectified or rebalanced by Newton's contemporary, Liebnitz, who did some work with infintessimals, a number system that is built around a one dimensional zero--or something like that. At this point I'm out of my depth.
atheist scientists don't believe in God since there is no "proof" yet fall all over themselves expousing the existence of cosmic strings and 23 different dimensions, for which there is
no experimental proof whatsoever
ah, hypocrisy. faith is OK, but only if politically correct
Random means uniform does it not? So I was taught in chemistry class.
Bump for later
I'll never understand how it is that theoretical scientists fail to see the handwriting of God in the essence of their work. Just because something is of divine nature doesn't necessarily mean it defies measurement, it merely defies our current technology to make those measurements. And once measured, that doesn't mean that it has nothing to do with God's work.
God only gave Moses the rules for human behavior, not for the behavior of the universe. To assume that those 10 commandments are the only laws in existence which God created (or enforces) is arrogance in the extreme.
During my undergraduate degree studies in Physics, it became quite clear to me - nearly an atheist at the time - that the only plausible explanation to the universe rested with what we define as God. As I have aged over the last 25 years since, this belief has only become stronger.
Eventually, when humankind learns to overcome mortality, the human invented aspect of linear time will fall by the wayside, opening the doors which are closed today. Quantum theory begins to erase linear time, but time still keeps us "on the plantation" so to speak - locking us into Newtonian mechanics as the basis of our physical understanding.
This could be the answer to Fermi's paradox - in our local miniverse - advanced civilizations have come up with the physics to do this sooner rather than later. We're next.
Has there been any experimental verification of string theory? What if this is a colossal dead end--what's Plan B?
I imagine that we'll burn that bridge when we come to it.