Why Does There Have to Be a Unified Theory (breakthrough, problem)

[twixcookie]

Okay, they are still looking, and somehow trying to get all the forces under, and matter, under one roof.

Relativity explained the cosmos but quantum mechanics didn't "jive" with it in terms of predicatability and method.

So...why DOES there have to be a unified theory? Perhaps nothing really necessitates it, and maybe Randomness really runs the show.

String theory seems to work, or should I say, works mathematically, yet isn't completely accepted.

It is as if the gods do not want us knowing their complete recipe for the cosmos.

[coosjoaquin]

There may never be a GUT but thats no reason to stop looking for answers.

[harry chickpea]

GUT is just an expansion of our wanting to know the rules of the game. We started when we understood there were some rules to living that were consistent. Hopefully, by the time a GUT is reached, we can go "Oh yeah. That was obvious in retrospection, wasn't it?" and move on. Until then (wait for it...) we are just gutless wonders.

[twixcookie]

Originally Posted by harry chickpea

GUT is just an expansion of our wanting to know the rules of the game. We started when we understood there were some rules to living that were consistent. Hopefully, by the time a GUT is reached, we can go "Oh yeah. That was obvious in retrospection, wasn't it?" and move on. Until then (wait for it...) we are just gutless wonders.

I see the universe as rather random.
Maybe the very small and the very large obey 2 sets of rules for some kind of reason?

[harry chickpea]

Originally Posted by twixcookie

I see the universe as rather random.
Maybe the very small and the very large obey 2 sets of rules for some kind of reason?

Could be. An off-the-wall thought could be that the granularity of four dimensions doesn't fit comfortably in itty-bitty spaces. A bag of marbles behaves like a bag of marbles. Take a random tiny cube of a rapidly moving bag of marbles and you might find nothing one second, glass molecule the next, and so on. Doesn't mean the bag of marbles isn't a valid bag of marbles, just that you have to think about tiny bits of them differently.

"For a reason" is an odd phrase though for that macro/micro scale. Like Zen, it could just be that it is and is not and not is and not not.

[twixcookie]

Yes, I should have worded it as "just is"...because some things just are, like an algorithm.

[VegasGrace]

Many are coward, brilliant...but coward. So much better to be in 'company' with ideas rather than take ridicule and go against the grain.

Luckily, there have been many great minds that took a chance.

[GCSTroop]

In one word:

Supersymmetry.

[twixcookie]

Originally Posted by VegasGrace

Many are coward, brilliant...but coward. So much better to be in 'company' with ideas rather than take ridicule and go against the grain.

Luckily, there have been many great minds that took a chance.

Hey, there is no ridicule here...simply discussion and exploring ideas and concepts!

[jayrandom]

To answer your title question--no there does not have to be a unified theory.

What there does have to be is a fully self-consistent theory of nature. We don't have such a theory. As far as measurement is concerned, general relativity and quantum mechanics agree very well with what we have been able to observe. Unfortunately, both are valid under specific circumstances and when those circumstances break down so do those respective theories.

In particular, at very large energies or very small length scales (the so-called Planck scale) gravity must act very differently than it does at ordinary length scales. What this tells physicists is that there must be some other theory or theories that describe physics at these energies. As there aren't any accelerator experiments that even come close to reaching the energies needed to probe so-called "quantum gravity", for now most of the research on quantum gravity has been theoretical.

The only real requirements of a valid theory is that it adequately describe all experiments and that it is self-consistent. String theory has been a common proposed solution, and is able to produce quantum mechanics and general relativity in certain limits. String theory suffers from a few crucial problems and a few minor inconveniences. String theory has yet to produce any tangible predictions about anything, so as a physical theory is still half-baked. Of course, there could be a radical breakthrough which changes string theory from a mathematical exercise to a physical one--which is probably why people still tinker away with it.

Of course, that breakthrough could come from somewhere else. We won't know until it happens. We do think that the universe isn't random--what we can see obeys very strict rules that we understand so we can only assume what we don't see (i.e. physics at the Planck scale) obeys rules as well.

As for "unified theory" and "grand unified theory" these are two related, but slightly different, concepts. At first, electricity and magnetism were thought to be separate forces, but in the 19th century physicists were able to show that they were two different facets of the same force, termed electromagnetism. Einstein tried to combine electromagnetism and gravity in to a "unified theory" and was wholly unsuccessful. Electromagnetism is described by a quantum field theory, called QED, as are the other two forces, weak and strong nuclear force. While gravity has yet to be unified, electromagnetism and the weak force were shown to be different facets of the same underlying field theory, termed electroweak. This theory is quite successful and explains many experimental anomalies. Attempts to unify the electroweak with the strong force (which is described by quantum chromodynamics) have been labeled "grand unified theories". These describe all three of those forces as different aspects of the same fundamental field. GUTs as they are not as well accepted as electroweak. A true unified theory would describe all four forces (em, weak, strong, and gravity) with the same field. There is no reason that the actual theory that describes the universe must be unified in this sense, but physicists really hope so and that's often what they are looking for. There do have to be better theories, so that's reason enough to keep looking.