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0171: "String Theory"

Posted: Mon Oct 16, 2006 4:50 am UTC
by Matt
Image
This works on pretty much every level

It implies that the universe is also made up of slightly larger vibrating spiders

Posted: Mon Oct 16, 2006 4:53 am UTC
by Peshmerga
The universe is a series of tubes.

Posted: Mon Oct 16, 2006 5:00 am UTC
by Ephphatha
One thing is for sure, the universe is not a giant truck.

Posted: Mon Oct 16, 2006 5:22 am UTC
by rlo
The string theory comic doesn't seem quite right:

SF-1: Suppose all matter and energy is made up of tiny, vibrating strings...

SF-2: OK, what would that imply?

SF-3: I dunno.


Isn't the actual implication that we might be able to unify relativity and quantum mechanics with a single theory? Wouldn't it make more sense this way:

SF-1: Suppose all matter and energy is made up of tiny, vibrating strings...

SF-2: OK, how would you test for that?

SF-1: I dunno.


Sorry if this seems hypercritical. I love xkcd.

Posted: Mon Oct 16, 2006 5:38 am UTC
by Matt
Suppose your mom is made up of tiny, vibrating strings

I like the idea that the guy figures his theory implies something but isn't sure what it is rather than if he knew what it implied and there was no way to test it. I like it even better if it means he hasn't gotten far enough to know whether it implied anything at all yet. And better yet if he just doesn't care.

Posted: Mon Oct 16, 2006 5:48 am UTC
by Gelsamel
Haha awesome. The comics just keep getting better!

Posted: Mon Oct 16, 2006 6:08 am UTC
by lemurs1
Peshmerga wrote:The universe is a series of tubes.


Ha, ha. I laughed as much for this as the comic. Excellent work!

Posted: Mon Oct 16, 2006 7:18 am UTC
by Hawknc
//Copyrights 'tube theory'

Posted: Mon Oct 16, 2006 9:17 am UTC
by Bluefire

Posted: Mon Oct 16, 2006 9:43 am UTC
by SpitValve
String theory eh? Can't argue with that comic :)

Posted: Mon Oct 16, 2006 10:51 am UTC
by Marlayna
I'm sure string theory *must* conclude something testable somewhere, they just haven't reached it yet...

Posted: Mon Oct 16, 2006 12:16 pm UTC
by abcde
I hope our universe is null-terminated and whatnot...

Posted: Mon Oct 16, 2006 1:40 pm UTC
by fjafjan
hehe, great comic man :D

tho i agree that it does have some rammafication, just no real, erm, evidence, as far as i know anyway

Music

Posted: Mon Oct 16, 2006 2:14 pm UTC
by lft
On a romantic sidenote, string theory approaches the old "music of the spheres" concept.

If everything in the universe consists of the same thing, just vibrating at different frequencies, then it doesn't matter what the "thing" is. All that matters is the frequencies, and so, the universe, this whole mess of tangible and intangible entities, would just consist of various arrangements of frequencies.

And then the entire universe could be said to be an enormous ongoing symphony.

seriously

Posted: Mon Oct 16, 2006 2:22 pm UTC
by RAPTORATTACK!!!
what DOES string theory imply?

Posted: Mon Oct 16, 2006 2:22 pm UTC
by zombie_monkey
You know those "science" books with ridiculous names that make you cringe when poeple talk about them? I've never managed to make myself consider it seriously, even though it was widely publicised -- the tone was always too similar to that kind of pseudosience. Now it seems my intuition was right, as it's soon to go out of fashion even among the kind of people who buy such books.

Posted: Mon Oct 16, 2006 3:32 pm UTC
by peri_renna
rlo wrote:The string theory comic doesn't seem quite right:

SF-1: Suppose all matter and energy is made up of tiny, vibrating strings...

SF-2: OK, what would that imply?

SF-3: I dunno.


Isn't the actual implication that we might be able to unify relativity and quantum mechanics with a single theory? Wouldn't it make more sense this way:

SF-1: Suppose all matter and energy is made up of tiny, vibrating strings...

SF-2: OK, how would you test for that?

SF-1: I dunno.


Sorry if this seems hypercritical. I love xkcd.


I think it works as it is. I read SF-2's question as "what does string theory predict that current accepted theories don't?" And you'd test the theory by testing those predictions.

My impression was that actually getting any useful predictions out of string theory would require figuring out the equations for it. Which no-one has ever figured out how to do.

Re: seriously

Posted: Mon Oct 16, 2006 7:15 pm UTC
by rlo
RAPTORATTACK!!! wrote:what DOES string theory imply?

General Relativity is really good at describing the behavior of large things. Quantum mechanics is really good at describing the behavior of small things (specifically, sub-atomic particles). But the two theories are very different, and actually break down entirely for objects at the point where the theories meet.

String theory attempts to reconcile general relativity and quantum mechanics. It describes everything as 10-dimensional vibrating strings, and from this, supposedly gives rise to both general relativity and quantum mechanics.

Or maybe the strings are 11-dimensional. The big problem with string theory is that it's pretty vague - it looks good in theory, but the math describing it is incomplete, and it hasn't ever been tested, and it's unclear if it ever could be tested.

That's my understanding, anyway. I'm sure someone will correct this where it's wrong.

Posted: Mon Oct 16, 2006 7:49 pm UTC
by Jack Saladin
I remember someone tried to explain string theory to me once.

Man, that got awkward fast.

Posted: Mon Oct 16, 2006 9:52 pm UTC
by Charodei
Brane theory isn't much better. This reminds me of the 'computational linguistics' comic. It's difficult to take either theory seriously when they can't decide how many dimensions there are. To the best of my knowledge, no one has proposed an experiment to find out.

Posted: Mon Oct 16, 2006 11:01 pm UTC
by rlo
Charodei wrote:Brane theory isn't much better... It's difficult to take either theory seriously when they can't decide how many dimensions there are.

It's 14 dimensions: three of space, one of time, ten that are folded up so tiny they can't be detected, and then this other one that's made entirely of chocolate.

Posted: Tue Oct 17, 2006 12:13 am UTC
by tylerni7
Don't forget the scientific name for shrinking those dimensions into the 3 spacial dimensions that we see. Compactification, and no, sadly, I am not making that up. Oh and different parts of string theory have different numbers of dimensions. Some are 21, some are 11, and all are crazy.

Posted: Tue Oct 17, 2006 12:28 am UTC
by Peshmerga
I don't take much stock into no dimensions.

If I can't eat or fuck it, it doesn't exist.

Posted: Tue Oct 17, 2006 1:10 am UTC
by rachel
Peshmerga wrote:If I can't eat or fuck it, it doesn't exist.


If only we all had that outlook. I'm sure if we did the world would be a much better place. Or at least more populated. (Practice safe sex, guys. Pregnancy scares are never fun.)

Posted: Tue Oct 17, 2006 1:48 am UTC
by lanaer
rlo wrote:It's 14 dimensions: three of space, one of time, ten that are folded up so tiny they can't be detected, and then this other one that's made entirely of chocolate.


But what kind of chocolate?

Posted: Tue Oct 17, 2006 3:32 am UTC
by rlo
lanaer wrote:
rlo wrote:It's 14 dimensions: three of space, one of time, ten that are folded up so tiny they can't be detected, and then this other one that's made entirely of chocolate.


But what kind of chocolate?


Huh. Apparently, this kind!

Posted: Tue Oct 17, 2006 4:07 am UTC
by Pathway


They even called it the Internets in that spiffy diagram toward the end!

http://www.youtube.com/watch?v=LKTH6f1JfX8

Oh, yeah, and regarding experimental testing of string theory: according to the physics professors I know who work on string theory, the Large Hadron Collider at CERN is going to be able to go further down that road.

By 'know,' I mean 'have classes taught by and occasionally talk to.'

Posted: Tue Oct 17, 2006 5:00 am UTC
by Charon
If you assume everything is made up of little strings, you get gravity. *Poof!* You don't have to add it or anything, it just appears. That's really quite cool.

As far as testable predictions go, yeah, well, that's why this comic is funny. But they're working on it. I have nothing but respect for string theory phenomenologists. Those just working on the theory have my respect too, but at the moment they're really more mathematicians than physicists.

Posted: Tue Oct 17, 2006 6:08 am UTC
by EM-002.rv-L "Tem Cu
So... The universe _isn't_ populated by gravity faries? They're all _string_ faries?

Posted: Tue Oct 17, 2006 6:40 am UTC
by SpitValve
There is one testable prediction of string theory: that protons will decay. They even predicted the half-life.

Current measurements say that either protons do not decay, or their half-life is several orders of magnitude larger (something like 10,000 times) larger than predicted by string theory.

Posted: Tue Oct 17, 2006 6:46 am UTC
by Gelsamel
Does that really count as testable?

Posted: Tue Oct 17, 2006 7:05 am UTC
by rlo
SpitValve wrote:There is one testable prediction of string theory: that protons will decay. They even predicted the half-life.

Current measurements say that either protons do not decay, or their half-life is several orders of magnitude larger (something like 10,000 times) larger than predicted by string theory.

SpitValve, that's really interesting. You say testable, which presumably means they might be able to one day but haven't yet. Have they figured out a method? What do they need to do to perform the tests?

Gelsamel wrote:Does that really count as testable?

Gelsamel, why wouldn't that count?

Posted: Tue Oct 17, 2006 7:10 am UTC
by Jack Saladin
Well, if it's testable why haven't they tested it?

Posted: Tue Oct 17, 2006 7:26 am UTC
by rlo
Here are a few short writeups on string theory for laypeople.
Charon, thanks for pointing out that gravity just appears in string theory. I hadn't know that.

Posted: Tue Oct 17, 2006 7:30 am UTC
by Gelsamel
rlo wrote:Gelsamel, why wouldn't that count?


I mean sure it's "testible" but is it reasonably testible? It seems as though it would take a massive amount of time to test.

Posted: Tue Oct 17, 2006 8:04 am UTC
by Air Gear
rlo: Gelsamel is right about it not really counting as testable, but not quite for the right reason. As I understand string theory, there's a dynamical field variable known as the "string coupling constant" which affects quite a bit. In short, we know the proton decay time is really, really huge at this point...but there's probably a value of the string coupling constant which is consistent with any given finite decay time. That's how I'm understanding it, at least...

Posted: Tue Oct 17, 2006 10:53 am UTC
by ijmaxwell
The fun thing about today's theoretical physicists is that it's almost impossible to tell them from cranks, aside from the sort of journals that publish their work.

I mean, really. Eleven-dimensional vibrating strings? Time Cube? Unless you're a theoretical physicist yourself, how do you decide which to believe?

Posted: Tue Oct 17, 2006 12:16 pm UTC
by Ephphatha
String theory: It's science and religion together at last!

Posted: Tue Oct 17, 2006 12:20 pm UTC
by myoumyouou
Ephphatha wrote:String theory: It's science and religion together at last!


ahahahah, finally, i'm so sick of all these christians, and their not believing in gravity (bonus points for all who got that reference)

Posted: Tue Oct 17, 2006 2:28 pm UTC
by TheTankengine
I am by no means a theoretical physicist, and I don't purport to even comprehend the notion of somewhere between 9 and 22 dimensions, or whatever the latest count was. But most of what I DO know about string theory originally came from the NOVA series "The Elegant Universe". I don't know if that is a good thing or not... But anyways, its an excellent-ly produced show and is really quite interesting. I believe this has something to do with it: video.google.com/videoplay?docid=4258041398583592305&q=einstein

Check it out!