Question

What is string theory?

Answer 1

Wait for the book you just said you'd order; it'll explain it to you.

But in one sentence: it's an attempt by theoretical physicists to develop a new theory of nature that gets 'behind' both quantum mechanics and general relativity to an even more fundamental theory of the universe.

Answer 2

Nice, are there any "competetors" to string theory?

Answer 3

quantum loop

Answer 4

And what is that?

Answer 5

At the moment, not any very developed ones, no. String Theory has serious problems of its own, as Greene won't shy away from describing in the book.

Answer 6

Ok, So basically it is a theory of how the universe is built?

Answer 7

It's a theory about the fundamental nature of space, time, matter and the forces between matter.

Answer 8

So it pretty much covers everything?

Answer 9

Yes, but even if string theory is right, don't expect it to tell you about something as simple as the orbit of the moon about the earth or why sparks are generated when you pat a cat. It's a theory that attempts to explain in the same language why gravity is there at all and why electricity is there at all.

Anyway, as I say. I actually don't think it's worth getting too excited about it because there are problems. But it is worth getting excited about quantum mechanics (which does explain static discharge from a cat) and general relativity or even just Newtonian mechanics, both of which explain the moon.

Answer 10

So what is general relativity?

Answer 11

General Relativity is a broadening of Einstein's Special Relativity.

Special Relativity demonstrated the consistency of the laws of physics (particularly the speed of light) for all frames of reference at a relative uniform velocity to each other. It comes to many conclusions that you should acquaint yourself with, such as the fact that mass, space, and time are subject to change in different frames of reference. This is basically to keep the speed of light the same in all frames of reference.

General relativity extends this idea to any frame of reference, including those that are accelerating. One of the most important ideas of General relativity is called the equivalence principle, which is basically the idea that the force feel you get when you are in an accelerating vehicle is the same as the force of gravity. Both in this theory are a result of the curvature of space-time. This will be a big theme in string theory, so you should learn at least a bit first.

Answer 12

So to put it in one sentence, all force is alike?

Answer 13

Actually, ill take that back.. Wait a second, ill go read a little about it.

Answer 14

Wise decision. Putting relativity into one sentence is not really a good idea.
Einstein once said "Everything should be as simple as possible, but not simpler."
I like that quote.

Answer 15

Should i read up on special relativity before general relativity? Oh and that quote is perfect

Answer 16

Greene's book is particularly valuable because the first few chapters explain Special R, General R and QM in layman's terms without devolving into Hawking vagueness. In other words, that book will give you an intro.

Answer 17

I ordered it an hour ago :) By the way, wasn't general relativity disproved when they discovered that neutrinos can travel faster than light?

Answer 18

that's not a sure thing yet

Answer 19

second that. There also remain on the books thousands and thousands of experimental verifications of GR.

Answer 20

I just saw on wikipedias entry on GR that "a ball will fall the same way in an accelerating rocket as it will in a gravitational field" why is that?

Answer 21

It's called the equivalence principle.

Answer 22

That is what I mentioned above about GR. Read that bit.

Answer 23

Oh! now i understand what you wrote!

Answer 24

Since we are on that subject, if we make a "spaceship" shaped like a cylinder and make it spin, wont that emulate gravity so that if a man was inside of it he would be able to walk as if it were earth?

Answer 25

Yes, but it would be in reverse of course.

Answer 26

..away from the center of the spacecraft.

Answer 27

yes, they do that quite accurately in the classic film: 2001.

the other thing they get wonderfully right in that film is the silence in the vacuum of space.

Answer 28

What do you mean?