Veil of Fire

....this makes my head hurt. Muchly.

Answerer

I think I will go for manifolds first.

Veil of Fire

Ugh... just went through it again, and my head hurts MORE. I think I need more pictures.

So string theory is saying that particles are excited states of a subatomic string under tension? And gravity is also an excite state of an aforementioned string?

Or is it saying we're tied down to the earth by a bunch of teensy strings?

Or both?

I'm so confused.

Bill

Yes, so far as I understand it. When the subatomic string vibrates in a particular way, you get a quark, and the quarks are the true building blocks of matter. Yes again.

Here, it must be mentioned that so-called "gravity waves" are some of the most controversial aspects of string theory. We know a lot about electromagnetic waves. And quantum mechanics leaves us with this wave/particle duality to deal with. How does one photon of light behave as both a wave and a particle at the same time? String theory proposed to explain that by hypothesizing that a photon of electromagnetic energy is an excited string, and that the vibrational state for being matter or energy is altered by whatever the observer does in order to observe the vibrational state of the string. There is a lot of explanatory power in string theory.

Einstein proposed that gravity worked by bending the space/time continuum. We are held down to the Earth because the Earth's mass creates enough of a bend in the local space/time continuum to make it very difficult for us to "climb out" (propel ourselves up to escape velocity).

The alternative view proposes that there is a gravity wave and a gravity particle (the graviton), and within string theory, those two would be generated by a vibrating string, just as a photon or light wave is. There is enough scientific thinking behind these ideas that billions of dollars are being spent in efforts to (among other things) produce evidence of gravity waves and/or graviton particles.

As things sit, we don't really know how this will all shake out. We have only a collection of scientific hypotheses and no real answers. If the graviton and gravity waves are true, then yes, we are "tied down to the earth by a bunch of teensy strings." However, we need to resolve just how that mechanism works and why it at least appears to warp the local space/time continuum (the experimental evidence for the truth of that situation is pretty overwhelming).

As I said, we don't really know yet. We have a lot of interesting predictions coming out of string theory, but as yet, no overwhelming and verifiable results. Time will tell.

== Bill

Answerer

Hey guys, I had another question regarding string theory that is, does superstring theory's predictions of quantum state share the uncertainity 'nature' of QM's predictions?

eh

Yes. And string theory does not offer answers to some of the quantum weirdness we get in the standard model.

Demosthenes

the aspect of the theory viewing gravity as being a collection of gravitions is what bothers me the most. It's always been a thorn in my side as long as I've been following the developments.

The reason? Einstein in his general relativity showed that gravity isn't a force at all, it's just a consequence of the apaprent distortion of the spacetime. So when we fall, we're feeling the tug of the spacetime. So here we are trying to quantize the gravity "force" to figure out the details of the gravitions and many times after one other the theories blow up when attempting that. We didn't even have any difficulties in figuring out the other three remaining forces. Why is gravity so difficult?

The present versions of the string theories assume that spacetime is just a background where strings and d-branes play out their roles. As we learned in relativity, spacetime is far from being a passive player.

Of course, while the relativity describes the consequences and the behavior very well, it's still a major puzzle about exactly what is bending. Perhaps as we look deeper in ever diminishing scales we'll see that gravity arises out of the interations between discreet elements. It wouldn't be surprising if there isn't really any "bending" in any sense, the mathematics just happened to fit the situation quite well.

[ July 27, 2002: Message edited by: Demosthenes ]</p>

Answerer

Well, I see graviton being described as a very small quantization of spactime.

Demosthenes

A graviton is defined as being a string vibrating in a certain mode. The reason the string is vibrating is because it's under tension and that it's moving around in ten dimensions in a such way that a gravition is produced. it's not a quantization of the spacetime.