Print 12 comment(s) - last by Project51.. on Jan 29 at 10:43 PM

IceCube is a cubic kilometer of ice burried under 1400 meters of the snow to remove interference - Courtesy NSF
A new experiment in Antarctica may reveal the answers to the most consuming question in physics today

PhysOrg is reporting about an ambitious new neutrino detector experiment near the South Pole.  By positioning sensors along a 1 cubic kilometer patch of ice buried below the Antarctic ice flows, NSF researchers anticipate detecting high energy neutrinos as they collide with atoms in the ice flow. 

High energy neutrinos are sub atomic particles.  Scientists are interested in cosmic neutrinos -- remnants of galactic explosions and other phenomena.  Typically, high energy neutrinos pass through the Earth without colliding with a single particle.  IceCube and other various neutrino detectors attempt to spot a neutrino as it collides with water molecules in the ice.  Only a few high energy neutrinos have been spotted in all detectors to date, but scientists find these collisions extremely useful because particle accelerators cannot propel neutrinos to speeds found naturally with these high energy neutrinos. 

The collisions of particles found in IceCube will be studied to see if they support or disprove string theory.  String theory is a proposed Theory of Everything -- a way to describe all physical phenomena in one concise set of laws.  In a nutshell, string theory claims that the universe is not made up of small particles, but rather small strings that vibrate.  The vibrations of these strings compose all physical matter and forces of the universe. 

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Some responses
By clubok on 1/29/2006 4:13:42 PM , Rating: 4
I hopefully have something useful to contribute to the subject, since I did my Ph.D. research in string theory. On the other hand, I have been out of the field for several years, so my information is a bit outdated.

First, string theory has nothing to say (directly) about the existance of God, or the evolution-creation date - no more than Newton's laws or Einstein's theories of relativity do. It may affect the discussion indirectly, in that it may help us better understand the Big Bang - an event that many creationists dispute.

Second, why do so many physicists "believe" in string theory? Because they know that there is a serious problem with the theories that are better verified. Quantum field theory gives amazingly accurate results - especially for very small things - as long as we don't look at places where gravity is very strong. General Relativity gives amazingly accurate results - especially for gravity - as long as we don't look at things that are too small. Try to combine the two, and we get mathematical nonsense. This makes it impossible to describe small things with strong gravity, like the center of a black hole, or the Big Bang. String theory is widely considered to be the most likely candidate for resolving this impasse. There are other candidates, but none have any more evidence than string theory.

String theory may not be true, but the inconsistency of gravity and quantum theory tells us that there must be something beyond what we know. String theory is simply the most likely candidate for what that something is.

Third, string theory does in fact predict a large number of dimensions. The number has seemed to vary between 10, 11, 12, and 26, depending on which version of the theory physicists are most excited about at the moment. But in my opinion, this is actually a less outlandish concept than many of the concepts in quantum theory or relativity theory.

It's actually pretty easy to visualize how the extra dimensions could exist, without our being aware of them. Consider the surface of a garden hose. That is a two-dimensional space, but one of the dimensions loops around in a circle. To a giant, the hose looks like a line, and the second dimension is invisible. To a flea standing on the hose, the second dimension is visible. In the same way, the extra dimensions in string theory could be "compactified" so that giants like us cannot see them. This may be a hard concept to grasp, but I think it's a lot easier to visualize than, say, the curved spacetime of General Relativity.

What I want to know is this: What do they expect the neutrino experiment to tell us about string theory? What results would give us an answer one way or the other? Without knowing the details, I suspect that we might be seeing some hype. It is not uncommon for string theory papers to show that under certain narrow assumptions, one has a small chance of noticing "stringy" effects under conditions that could be reachable by experiment. In most of these cases, a positive result would be suggestive that string theory is true, but a negative result would only indicate that the specific assumptions were incorrect, and say nothing at all about string theory in general. I wouldn't get too excited about an experiment that might prove string theory unless it also had the potential to disprove string theory. Or at least a fairly broad category of string theories.

RE: Some responses
By stephenbrooks on 1/29/2006 6:02:32 PM , Rating: 2
Isn't this about looking for Lorentz-violation in the highest-energy cosmic rays? I guess super-high-energy neutrinos would have the highest gamma factor of just about any massive particle I can imagine, so they're a good one to test that e.g. the speed of light stays constant. That, I thought, was something on the level of extra dimensions/strings, as opposed to the 'normal' neutrino oscillation research which only reaches to supersymmetry and the GUT level.

RE: Some responses
By clubok on 1/29/2006 10:21:57 PM , Rating: 2
From the article at physorg:

“String theory and other possibilities can distort the relative numbers of ‘down’ and ‘up’ neutrinos,” said Jonathan Feng. “For example, extra dimensions may cause neutrinos to create microscopic black holes, which instantly evaporate and create spectacular showers of particles in the Earth's atmosphere and in the Antarctic ice cap. This increases the number of ‘down’ neutrinos detected. At the same time, the creation of black holes causes ‘up’ neutrinos to be caught in the Earth's crust, reducing the number of 'up' neutrinos. The relative ‘up’ and ‘down’ rates provide evidence for distortions in neutrino properties that are predicted by new theories.”

It doesn't sound to me like they're looking at Lorentz violation. BTW, the 'down' vs. 'up' in the quote refers to the direction the neutrinos are coming from - not their helicity (which way they spin) or their flavor (what kind of neutrino). So I'm guessing that they're not looking for oscillations either.

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