Do you believe in the String Theory ?Is it possible?

Answer 1

Interesting question - why is it turning out that many of our scientific theories are becoming belief systems? Leaving the scientific aspects aside for the moment. String theory presents a couple of philosophical questions of note.

1) It is basically a quantum theory. At core are Feynman's Path Integrals. When applied to real world calculations - these notoriously would blow up - diverge - presenting infinities. By assuming the particles had dimension, the divergence disappears.

2) Instead of assuming point (0-dimension) particles, we have string (1-dimension) particles. If you think strings are small and unobservable - points are impossibly small and really not observable. Yet all theories previous to strings assumed point particles, yet the theories to some extent valid because they predict phenomena that can be observed. I suspect that String Theory will be validated the same way.

3) Original quantum theories were developed following very strong philosophical theory called Logical Positivism or Logical Empiricism with same conviction and zeal that is associated with religous movements. Nothing exists except what is observed and nothing exists beyond what is observed. David Bohm showed that a consistent Quantum Theory can be developed assuming that something does exist beyond observations. Hence Strings move to an entirely different philosophical school of thought. This may be jarring to physicists growing up in the old school of thought.

4) By assuming the particles have dimension not only do "infinities" disappear but the graviton predicted for quantum gravity suddenly appears and is fundamental to the theory. So there is every indication that size does matter and matter has a finite size - (sorry couldn't resist). So in a sense the theory has produced something observable - gravity - or at least explains a relationship that the original Quantum theories could not.

5) There have been attempts with super gravity and super symmetry to present "conventional" theories that did not assume strings but the math keeps returning to strings or membranes of multiple dimensions indicating geometry underlies the theory. This is exactly what has to happen if Quantum Theory and General Relativity are to be brought together into one theory.

So there are a lot of interesting discussions that can take place exploring the philosophical and metaphysical implications of Strings and Branes. But as a theory is seems to be still divorced from physical reality and still missing the wow factor - to make it truly a religious - see the mind of God - type of experience.

I would hope it could eventually explain why particles have the mass they do and how the physical constants are related. At the moment there are too many particles, too much symmetry and no mass for any particles. So something is missing that explains why symmetry breaks the way it does and results in the world we observe. So call me - still a seeker.

Answer 2

Well, I've read Brian Greene's first book, The Elegant Universe, and I'm nearly finished with his second, The Fabric of the Cosmos. Greene is a string theory cosmologist.

He keeps the math out of the books -- it would be over my head anyway -- but as I get it, here's the idea ...

First, general relativity and quantum mechanics work well for the macro and micro worlds respectively, but only as long as they don't tread on each others' toes. In a few situations they butt heads, such as at the center of black holes and at the beginning of time (before the inflation era, before the big bang). When it comes to "singularities", the equations of GR and QM break down -- something like dividing by zero.

There ought to be a way to harmonize the macro and micro worlds, and string theory holds out a possibility.

Particle physicists have broken things (e.g., atoms) down into a half-dozen kinds of quarks, some "messenger" particles (gluons, gravitons, photons, neutrinos, ...), and so on. Some of these things have mass, charge, spin. Others are massless and are treated as dimensionless points.

All that is part of the Standard Model. String theory says all of these "things" are composed of something even more fundamental -- strings. Strings have length, and nothing is less than the Planck length, so you avoid dimensionless points, and you avoid the "divide by zero" problem. As a corollary, time itself may be quantized.

Strings vibrate with a period (frequency) and amplitude. They also vibrate in multiple dimensions. A plucked violin string may vibrate in two dimensions (up & down), but it also may vibrate in three dimensions (up & down, side-to-side). In theory, strings may vibrate in multiple (e.g., ten) dimensions, if such dimensions indeed exist.

A vibrating string contains energy, but using the equivalence relation e = mc^2, energy can be expressed as mass. The equations of string theory (which Greene doesn't talk about, thankfully) require ten (or eleven) dimensions to match the known properties (mass, charge, spin) of the several "things" the particle physicists have found.

NOW IF they can work out all the equations so that every "thing" (quarks, photons, etc.) are precisely represented by string configurations in the ten or eleven dimensions, then perhaps they've found their "grand unified theory" that unites the four forces -- electromagnetism, the strong & weak forces, and gravity (this last is a biggie) -- and at the same time unified GR and QM.

Now the question is, do I believe it? Well, I'd say it would be highly persuasive. Having one theory that explains all this stuff, at the same time harmonizing general relativity and quantum mechanics is extremely impressive. How to confirm this result experimentally, though, sounds like a ponderous proposition. But who knows? They've figured out ways to confirm other "far out" theories.

On the other hand, this, even if successful, could turn out to be like Ptolemy's epicycles ... they might model or explain things very well, but only until something better comes along.

So for now, it looks like string theory has great potential, well worth the effort being put into it; and to the extent it's successful, it's believable (even the extra "hidden" dimensions), but a grain of salt is also advised.

Answer 3

I am not a physicist but I am interested in reading about general stuff on quantum and string, but I am not keen on the theoretical math side. Last time I talked to a theoretical physicist at the Perimeter Institute here in Waterloo, he told me the biggest challenge with string is that it is not something directly observable. Most of the theory is based on complex mathematics and appears to explain things properly. I believe there is another branch called quantum gravity (or I didn't remember it correctly), it is another attempt to formulate the QUT. So string theory is possible, it's just very difficult for us to design actual experiments to verify it (consider the engineering challenges to probe at the scale of the strings as proposed in the theory).

Answer 4

Believing in something like string theory isn't an issue - it's understanding the higher maths involved. I can grasp the concept at a very surface level and according to several physicists I have actually asked it seems to fit the required parameters of a working explination for MANY of our most deeply investigated questions into the nature of the relationship between gravity and the other three forces.

It's not a question of belief, it's a matter of comprehension.

Answer 5

There are still millions of question's to be answered, but if you can find a test that it will not hold to at any level, then it does not work. One test and the theory is no good.

Answer 6

I'm not sure what that is. If you explain it I'll come back and think about it becaue I'm good at science.

Answer 7

Yes and Yes.