String theory/particle physics - Page 2

What a fun book. I need to revisit it.

Einstein "wasted" a good chunk of his later years searching for a unified theory. I wonder if anyone is any closer today. I'm guessing no. I'll have to hit the library once I am done with exams to find something interesting to read.

I think there is currently a Grand Unified Theory in the works that unifies three of the five forces but not all of them so that's what the string theory does...SOMETHING LIKE THAT.

Everything I said above might be complete garbage, and I'm too lazy to look it up. I have officially learned nothing from that seminar.

/pointless post

I think the GUT is a theoretical ideal that most physicists strive toward. I think it would be near impossible to combine everything in one equation since we still do not know whether there are yet still weaker forces hold subatomic particles together; I should say improbable since scientists thought the same about locating electrons (Heinsenberg).

As I understand it, the collection of what we know about the universe is called "the standard model". Currently, the standard model works for 3 of the 4 forces (electromagnetism, weak force, strong force) but it does not adequately explain gravity. Gravity is much weaker than the other three and people aren't sure why.
String theory gives a possible explanation using extra dimensions that we cannot sense.

I am a physics major, but this sort of thing is not my area of interest, so that explanation could be mostly baloney.

Almost a "must-read" IMO.

+1

Great book for an introduction to string theory.

For a more current treatment of string theory, check out Lisa Randall's "Warped Passages".

For a critique of string theories, check out Lee Smolin's "The Trouble with Physics".

Those two books will give you a pretty nice glimpse into the string theory landscape, and discussions of both its strengths and its shortcomings. String theory is actually a "class" of theories (comprising something like 10^500 distinct theories, or more theories than there are fundamental particles) which, collectively, fail Popper's "falsifiability" rule for valid physical theories - the main basis for Smolin's critique.

DH

Not Even Wrong I read this a couple years ago, it was interesting--another critique of the theory.

Fellow physics major representin. Rant on baby.

The SM is the current model used in particle physics to predict the behavior/existence of all of the particles that make up the universe as we know it to be and incorporates the strong, weak, and electromagnetic force. In a general sense it is all we know about the smallest bits of the universe in the same way general relativity is all we know about the big parts. The problem with the SM is that while it is RIDICULOUSLY accurate, it is ungodly ugly in a mathematical sense and doesn't include gravity (reason being that gravity is about 10^43ish times weaker than the strong force) so it must be wrong in some way.

This is the best image i've found to get across just how ugly the thing is:



This is where Grand Unification Theories step in (string, quantum gravity, M-theory, etc). The whole point of these is to bring the four forces into one model, and hopefully a mathematically pleasing one. There are tons of these but the big issue with them is that they are damn near impossible to verify experimentally. For example the extra dimensions posited by string theory have to be too small to detect directly by any current methods except an upper limit that isn't really physically possible within the framework of string theory itself, which is where the whole "not even wrong" criticism comes from. TLR is that XKCD is always right and you should not question it.

As for reading I would go with Smolin and Hawking before looking at Greene. Greene's book as I remember it is a bit overly optimistic about string/m-theory for my liking but then again it's been a couple of years since I read it. Either way the best way to go about finding out more is to start from the beginning (Newton) and work your way to modern stuff. Can't think of a book that properly does this off the top of my head but I find it to be alot more enjoyable a topic than reading fluffy string stuff with no real basis in experiment.

*Disclaimer: GUT stuff is fucking weird and nobody really understands it, not even theorists for the most part. I probably mucked some detail up horribly but it's close enough afaik.