Large Hardon Collider

[Woozie]

Anyone else watch Colbert last night? Brian Greene was on (and for Psion, the guy who published that psi paper that the rest of us wish would go away was on too). Apparently Greene has a new book out on parallel universes. I'm hoping my library has it because I really want to read it but I really don't want to buy it. He didn't give the specific reasons for parallel universes, but I'm hoping he doesn't say "String Theory" or "Many Worlds interpretation". I've actually seen quite a few different reasons that there could be parallel universes and some of them are actually pretty interesting, though like I said, he doesn't go over any of them in the interview. I hope parallel universes are real because that means in some universe I've achieved my goal of world domination and destroying all engineers and english majors.

http://www.colbertnation.com/the-col...1/brian-greene

[Mizango]

sorry if repost:

was it miz or wooz that exchanges emails with NTD?

anyways, saw this clip and thought of you:

And he literally means every word of that. I love me some Carl Sagan, hes the single greatest influence in my educational life.

It's Miz. He wont even accept my facebook friends request presumably because I still call Pluto a planet.

Edit: NDT is lying. There's no way NDT and Caral Sagan were in the same place at the same time without the entire universe collapsing under the combined weight of their awesomeness.

QFT 4EVER. Having those 2 in the same place would be the cosmological equivalent of dividing by a SMBH. Everything would just cease to exist from pure awesomeness.

Anyone else watch Colbert last night? Brian Greene was on (and for Psion, the guy who published that psi paper that the rest of us wish would go away was on too). Apparently Greene has a new book out on parallel universes. I'm hoping my library has it because I really want to read it but I really don't want to buy it. He didn't give the specific reasons for parallel universes, but I'm hoping he doesn't say "String Theory" or "Many Worlds interpretation". I've actually seen quite a few different reasons that there could be parallel universes and some of them are actually pretty interesting, though like I said, he doesn't go over any of them in the interview. I hope parallel universes are real because that means in some universe I've achieved my goal of world domination and destroying all engineers and english majors.

http://www.colbertnation.com/the-col...1/brian-greene

Yes I saw that lol

[Pirian]

You forget that this happened when NDT was still an aspiring student. I figure this would be the reason we're still here

Spoiler: show

That, or we're in the parallel universe that didn't collapse upon the meeting

[Max™]

The dark flow is controversial because the distribution of matter in the observed universe cannot account for it. Its existence suggests that some structure beyond the visible universe -- outside our "horizon" -- is pulling on matter in our vicinity.

http://www.nasa.gov/centers/goddard/...10/10-023.html



http://www.nasa.gov/centers/goddard/...k_Flow_map.jpg

Btw, this is the 25th anniversary of Challenger blowing up.

[Kaylia]

I don't want to be the guy who solve relativistic fluids dynamics equation to explain these streams...it's going to be a pain in the ass if they are real.

[Max™]

Bunch of the technical details in here: http://www.nasa.gov/centers/goddard/...pJ_inpress.pdf

It's mostly been found from checking the anomalous distribution of redshifts, actually solving the full state equation would be a hell of a thing.

[Eliseos]

in some universe I've achieved my goal of world domination and destroying all engineers and english majors.

Chemists before us, please. I envision engineers lasting the longest, at least between us and english majors.

[Ferion]

So is String Theory as bad as this board makes it seem to be, or is it just a very divided topic? From what I've read there is a ton of criticism, but at the same time people are receiving Phds for papers written about string theory. I've never really looked into the math behind it, but to me it seems a little ridiculous. Especially considering (from my understanding) it hasn't produced any kind of testable predictions as of right now.

[Max™]

This goes over some of the major points pretty well for an intro: http://www.newscientist.com/article/...ers-guide.html

http://arxiv.org/abs/0805.0543

"So what will you do if string theory is wrong?"

[Mizango]

So is String Theory as bad as this board makes it seem to be, or is it just a very divided topic? From what I've read there is a ton of criticism, but at the same time people are receiving Phds for papers written about string theory. I've never really looked into the math behind it, but to me it seems a little ridiculous. Especially considering (from my understanding) it hasn't produced any kind of testable predictions as of right now.

Yes.

[Kaylia]

So is String Theory as bad as this board makes it seem to be, or is it just a very divided topic? From what I've read there is a ton of criticism, but at the same time people are receiving Phds for papers written about string theory. I've never really looked into the math behind it, but to me it seems a little ridiculous. Especially considering (from my understanding) it hasn't produced any kind of testable predictions as of right now.

String theory is kinda like curve fitting applied to theoretical physics. It's a powerful tool to describe the world, but it's so complex that it's nearly impossible to predict anything out of it. One issue is that unlike many theories, it didnt originate from a simple physical concept (ie: momentum is conserved, light speed, matter is discrete). Instead, they added hidden variables to make the model works. Maybe these variables are truly needed, but as long they remain hidden to us experimentally, the model is kinda stupid.


New physics are usually built on solid ground. String theories however didn't try to fix the current issues of QM and Relativity before moving on, it just went ahead and ignored everything. It doesn't automatically make it wrong, but it's not the normal approach one would take to fix a problem. You need to start from something fresh that works, and build your model from there.

Lastly, when a theory get popular, it means other theories get less attention, and people might not look as hard as they should for better solutions. The amounts of time spent on string theories by physicist and mathematicians over the last 40 years is huge, and the result are very underwhelming so far. The theories itself is fine, but it's most likely hurting the scientific community indirectly.


Of course, it's not awful...the mathematics behind it are still impressives, and there is nothing fundamentally wrong with it (unlike ESP research), but it's still physics done backward.

[Woozie]

My post is somewhat long, so here's something better to read instead

http://www.math.columbia.edu/~woit/strings.pdf

Okay, I had a super long post typed up and it just magically vanished (maybe it fell into one of string theory's curled up dimensions) and hitting "undo" isn't bringing it back and now I'm pissed.

So anyways, if you're truly interested in learning what's wrong with string theory, you could PM me and I could give you a download link to Lee Smolin's book about it. I would just post it but I'm not sure how the mods would feel about that.

Anyways, to make a long post short, it's untestable (not just because we don't have the technology to test it. Some of it's predictions are untestable no matter what, which means string theory technically isn't even science). It allows waaaaaay too many possibilities. Imagine if Jean Gray gave you 10^500 psychic predictions and told you one of them accurately describes your future. You'd agree that she's the worse psychic in the history of comics. Well, then I guess that make string theory the worse theory in the history of science, because it describes 10^500 universes, which makes it useless even if one happens to be right. It's not all that obvious how to sort between these 10^500 universes or weed out a significant number of them. This situation and many others makes it extremely hard to make any useful predictions out of string theory (which is why, as you and Kaylia pointed out, we never get any real predictions from string theory). No matter what any experiment shows, it will always be consistent with some form of string theory because it predicts virtually everything. It's not only untestable, but it's unfalsifiable.

Another thing Kaylia pointed out is the attention it gets. String theory is popular because it has much better PR than the other theories on the frontier of theoretical physics. It's popularity has little to do with how good or bad of a theory it is. String theory is the reason I got into physics in the first place and may be the only reason I'm alive and not in jail right now (long story). String theory also has Brian Greene, which helps a lot because he's an great author and is really good at getting out to the public. String theory captivates the imagination with all of the mind-boggling stuff you can get out of it. We get extra dimensions, parallel universes, multiverses, extra big bangs, and much much more. While I'm not saying whether or not any of those things are real, I will say that just because a theory gives lots of nice fantasies for nerds, philosophers, and other groups doesn't make it more accurate. Yet, that's one of the major reasons behind its popularity.

Another aspect that made it popular was the fact that it predicts the existence of a massless spin 2 boson. This sounds remarkably like a graviton, and a theory that predicts both quantum physics and the graviton is phenomenal. This could be the road to unification.......or at least that's what we thought, originally. String theory has since become a huge failure, as you'll find if you read Smolin's or Woit's book on string theory.

Last semester I had the honor of meeting the guy who's funding my scholarships. This guy had the honor of meeting Smolin and Greene...at the same time. The two were arguing about string theory, and Lee Smolin rightfully pointed out that string theory is getting way more attention than it deserves, which is getting in the way of development of competing theories. No one, not even Greene, can disagree that putting all of our eggs in one basket (especially the string theory basket, though Greene would disagree with that part) is a good idea. Apparently there are huge funding issues and other issues due to string theory's undeserved popularity.

Anyways, I wont go on for longer, but if you're really interested, you should check out Smolin's or Woit's books. Or Woits blog (which I'll post links to).

Oh, and as Kaylia pointed out, the methods used for string theory aren't exactly solid. It's all approximations of what they think the fundamental equations and its solutions might be (or more precisely, it's all perturbative). I think Kaylia explained it better than I can, but yeah, the methods just aren't very good. We have no exact solutions to anything in string theory at all whatsoever, even with some of the most brilliant mathematicians and physicists in the world working on it for decades.

Peter Woit's blog

http://www.math.columbia.edu/~woit/w...=string+theory

[Woozie]

From Woit's article at the beginning of my last post (going to do some Kuya-style quoting here, with maybe a little Vajra thrown in for emphasis). I couldn't copy/paste, so I'm sorry for any transcription errors.

The strongest scientific argument in favor of string theory is that it appears to contain a theory of gravity embedded within it. It is not often mentioned that this is not yet a consistent quantum theory of gravity. All that exists at the moment is a divergent series that is conjectured to be an asymptotic perturbation series for some as yet undefined non-perturbative string theory [...] String theorist actually consider the divergence of this series a virtue, since otherwise they would have an infinity (one for each compactification of six dimensions) of consistent theories of gravity among their hands, with no principle for choosing amongst them.

No one has managed to extract any sort of experimental prediction out of the theory other than that the cosmological constant should probably be at least 55 orders of magnitude larger than experimental bounds. String theory not only makes no predictions about physical phenomena at experimentally accessible energies, it makes no predictions whatsoever. […] At the moment, it’s a theory that cannot be falsified by any conceivable experimental result. It’s not even clear that there is any possible theoretical development that would falsify the theory

As I explained earlier, we don't actually have an actual string theory. We just have a series of approximations of what we think the theory might be. This paragraph explains it well

String theorist often attempt to make an aesthetic argument, a claim that the theory is strikingly “elegant” or “beautiful”. Since there is no well-defined theory, it’s hard to know what to make of these claims, and one reminds of another quote from Pauli. Annoyed by Heisenberg’s claims that modulo some details he had a wonderful unified theory (he didn’t), Pauli sent his friends a postcard containing a blank rectangle and the text “This is to show the world I can paint like Titan. Only the technical details are missing.” Since no one knows what “M-theory” is, its beauty is that of Pauli’s painting. Even if a consistent M-Theory can be found, it may very well be a theory of great complexity and ugliness

Pauli is so freakin boss lol. He's my new hero. I'm going to change my avatar in honor of him.

Graduates students, post-docs and untenured junior faculty interested in physics beyond the Standard Model are under tremendous pressures in a brutal job market to work on the latest fad in string theory, especially if they are interested in speculative and mathematical research. For them, the idea of starting to work on an untested new idea that may very well fail looks a lot like a quick route to professional suicide. Many physics researches do not believe in string theory but work on it anyway. They are often intimidated intellectually by the fact that some leading string theorist are undeniably geniuses, and professionally by the desire to have a job, get grants, go to conferences and generally have an intellectual community in which to participate.

Edit:

Funding agencies should stop supporting theorists who propose to continue work on the same ideas as everyone. They should also question whether it is a good idea to fund a large number of conferences and workshops on the latest string theory fad. Research funds should be targeted at providing incentives for people to try something new and ambitious, even if it may take many years of work with a sizable risk and end up with nothing.
Particle theorists should be exploring a wide range of alternatives to string theory, and looking for inspiration wherever it can potentially be found.

[…]

During the 1960’s and early 1970’s, quantum field theory appeared to be doomed and string theory played a leading role as a theory of the strong interactions. Could it be that just as string theory was wrong then, it is wrong now, and in much the same way: perhaps the correct quantum theory of gravity is some form of asymptotically free gauge theory? As long as the best young minds of the field are encouraged to ignore quantum field theory and pursue the so far fruitless search for M-theory, we may never know.

SWINE FLU

^ That last quote may or may not be actually in the paper.

But seriously, I really wanted to emphasize the fact that the entire theory is apparently based on a divergent series.

Edit:

and there is nothing fundamentally wrong with it

I'd disagree with this, but that's just the mathematician in my talking. Mathematicians are rarely ever okay with the way physicists do their math. My professor at my REU last year says that by the time I get my PhD in physics I will have changed my mind about my criticisms of their methods, but I don't see that happening.

[Woozie]

http://www.smbc-comics.com/comics/20110128.gif

[Tsuko_Asura]

Awesome.

[Khamsin]

So string theory is more of a theory in the layman's sense, than the scientific sense? Why not call it string hypothesis?

[Restrat]

a scientific hypothesis requires you can test it as well!

[Max™]

http://www.physicsforums.com/showthread.php?t=7245

A thread on the "other game in town" loop quantum gravity, and some other similar approaches.

I like to use the term "string models" because that's what they are, it's interesting mathematically, but a model needs to produce a prediction which you can test before you call it a hypothesis, and a hypothesis has to be unfalsifiable to certain levels before you call it a theory.

[Kaylia]

I'd disagree with this, but that's just the mathematician in my talking. Mathematicians are rarely ever okay with the way physicists do their math. My professor at my REU last year says that by the time I get my PhD in physics I will have changed my mind about my criticisms of their methods, but I don't see that happening.

I should have worded my thought differently. What I was saying is that I don't believe it is wrong for a physicist to look into string theory if his intuition tell him to do so. Right now, it doesnt really work, but it's not impossible that someone someday will eventually manage to find a better interpretation that clean up the current mess. I personally don't think that's where the best solution is because "hidden variables/dimensions" feel like a cheap way to avoid the problems instead of answering it, but I can't turn down their attempt either on that basis that "it can't works".

I'm not exactly sure what you mean by "the way physicists do their math". It's true that sometime, physicist will cut corner, but it's usually an educated approximation that we need to find a non-numerical solution. It's not part of the theory, but an approximated result derivated from it.

Okay, I had a super long post typed up and it just magically vanished (maybe it fell into one of string theory's curled up dimensions) and hitting "undo" isn't bringing it back and now I'm pissed.

Pressing "esc" do that, and it fucking sucks.

[BerenTebogo]

Okay so I just started my Applied Modern Physics class and I'm feeling a bit overwhelmed by the first homework set. Usually takes me a bit to adjust to the professor / teaching style / new formulas and all but I'm feeling stupider than normal here. I've taken (what I think to be) every approach to this problem that makes sense but I'm not getting an answer that matches the textbook and even just doing crazy stuff looking for numbers that would be similar isn't yielding any positive results. HALP PLZ

"A supernova at a distance of 175,000 light years from Earth emits particles that travel in a straight line to Earth. If these particles travel with a speed v such that v/c= 1-10E6
how long will the trip last, as measured by an observer traveling with the particle? "

What I assumed to be the correct-ish track was to take the length contraction formula and the dt = dt'/sqrt(1-v^2/c^2) formula try to relate them using v = distance over time. Yadda yadda. Also tried solving into the length contraction formula but nothing is really coming up that makes any sense whatsoever.