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Can String Theory Accommodate Inflation?
David Shiga writes "String theory is the leading contender for a "theory of everything" that could unite all the forces of physics. But a recent study suggests that it may be more difficult than scientists had hoped to square string theory with inflation — the widely accepted notion that the early universe had a period of especially rapid expansion. Some say this could even lead to the abandonment of either string theory or inflation, though no one is ruling out a possible resolution yet."
It is said that papers in string theory are published at a rate greater than the speed of light. This, however, is not problematic since no information is being transmitted.
I don't think ANYTHING can accomodate inflation.
Just disrupt the deflector shield with a tachyon burst.
Does string theory incorporate the inflation of meatballs and saucy noodles (i.e. strings) due to FSM?
"String theory is the leading contender for a 'theory of everything' that could unite all the forces of physics. [citation needed]"
Yet another post validating this argument
(yeah, yeah, it's old. So sue me)
If the Fed cuts interest rates next week.
I've never understood how string theory could ever be validated, except through funky math invented for the purpose. It's my understanding that if you enlarged an atom to the size of the universe a string would be about 50 feet long (about a planck length). How is that ever going to be testable in practice? From all I've read, the energy required is just not possible, ever.
by M-theory. My understanding is that there are 5 different versions of 10-dimensional string theory that can be generalized to 11-dimensional M-brane theory. Not sure about the inflation thing though, I just wanted to throw in the fact that you are talking about an old theory.
As central governments print more and more strings, the strings currently in circulation are devalued.
Ah, that's where advertising comes in.
One man's -1 Flamebait is another man's +5 Funny.
I didn't believe that when I read it so I worked it out and found that that' actually true (to within an order of magnitude).
Um...physics has completely turned upside down in the last century and has changed pretty dramatically over the last 20 years. What kind of remote island are you living on that you're so out of touch and think that 'different' approaches never get funding? If you've never bothered to look at current research then you really don't have any right to speak, and it's obvious that you haven't. For example there has been ongoing debate for many years now between people who are searching for dark matter and proponents of MOND. There's nothing more annoying than pontification from ignorant armchair physicists.
Doesn't it make you feel good to know that our freedoms are protected by politicans, lawyers and journalists.
If all the little strings are broken, it's no wonder the universe is flying apart!
This is a vindication of us old school proponents of char* theory.
Momentarily, the need for the construction of new light will no longer exist.
no one is ruling out a possible resolution yet.
Ah-hem, I am. Please let the record reflect that I was the first to do so.
done. wake me up when there are more scientific milestones up for grabs.
ôó
The fact is that what string theory aims to explain (the very fundamental nature of the universe; the events just after the big bang; the reconciliation of quantum mechanics and general relativity) are effects that are inherently difficult to measure. (Otherwise these questions would have been asked long ago.) The fact is that we are not yet able to measure at the extreme energies where string theory becomes relevant. So, the fact is that string theory does make predictions, but it is difficult for us to test these predictions yet.
Efforts are being made, however. Increasingly sensitive measurements of large-scale cosmological phenomena, and ever-more-powerful particle accelerators may give us experimental information about string theory. Already, in fact, a wide variety of "string theories" have been discarded because they do not match the accelerator data. That is, we are placing bounds on the theories, based on experiments. This is how science works.
Also important to keep in mind is that string theory meshes with our currently established theories (which, it goes without saying, have been verified experimentally to a very high precision). The agreement is not yet perfect (as TFA points out), but it's important to keep in mind that of the millions of crazy theories you could write down to explain "the universe," very few of them can reproduce more conventional theories (e.g. electromagnetic interactions) in the appropriate limits. The fact that string theory meshes with established knowledge is the thing that keeps physicists "hopeful" that they are going down the right track. That doesn't mean the theory is right, but it shows that it fits in with our current scientific understanding. That's how science works: by developing more detailed theories that nevertheless reproduce the more basic theories. That kind of exaggeration isn't very useful. Ultimately string theory aims to explain the universe through verifiable (falsifiable) predictions. These observations are difficult to make, but are being attempted. If the observations contradict string theory, physicists will discard it. If a better theory comes along that explains observations, physicists will gladly use that theory instead. Until that happens, there is no reason to ignore our current "best guess."
Admittedly, there is an active and very loud group which has been theorizing that string theory will - at some point in the future - provide a grand unified theory of physics that is testable.
But there is a large and growing group of Ph.D.s who disagree, and believe that string theory is an evolutionary dead end in theoretical physics.
It is remarkable that now they're trying to push their theories into other spheres, when their core concepts are, as yet, unproven.
[caveat - I know this is controversial, in that many faculty and senior faculty in Physics are string theory proponents, but someone needed to point this out]
-- Tigger warning: This post may contain tiggers! --
String Theory is certainly an interesting mathematical theory, and that's fine - as a mathematician, I can respect that. But it has never had a single piece of confirming experimental evidence, and there are now suggestions that it in principle can't have confirming evidence. Given that a large part of the theoretical physics world has spent 30ish years on this, isn't it time to move on?
String theory is the leading contender for a "theory of everything"
Actually, not it's not. For this to be the case, it would have to predict something that is experimentally verifiable. Which has yet to be the case. All it is now is some really messy math. And even that's giving it something b/c most of it is the typical hand-wavy (read: non-rigorous) "math".
Quite frankly, the only good thing that I see here is that there might be an end to String Theory a.k.a. the "theory" that sucks up most of the money for research even though more than 3 DECADES have gone by without /one/ bloody experimentally verifiable prediction. Perhaps after this is all said and done with, we can spend some money on some actually *promising* areas of research.
String theory isn't science, but it isn't religion either. It's math. Someday it may become science.
Damning string theory is a bit like damning Reiman Calculus was in the 1890's. It was of no existing use. Eventually, though, Einstein found a use for it. That may happen with string theory. Or, of course, it may not.
It is interesting that the math can be mapped onto what is known about the universe. That makes it interesting. But it can't be tested, only particular mappings can be tested. So it's math rather than physics.
I think we've pushed this "anyone can grow up to be president" thing too far.
Oh please someone mod this down!
Electric Universe is not an alternate theory. To be alternative it needs to be based in reality somehow, but most of it's claims are easily disproved by just about every single observation we have ever made about the solar system.
Electric Universe is a scientific theory that is so bad it doesn't even deserve to be called pseudo-science.
Dark matter is certainly a bizarre hypothesis, and the question you ask is natural - couldn't we just be wrong about gravity? It's somewhat easier to believe that Einstein's general relativity is modified than that the universe is filled with so much mysterious, unseen "stuff". This is the basic idea behind MOND (MOdified Newtonian Dynamics) theories, which has received a good bit of thought among physicists.
MOND doesn't look like the right solution, however. The last 2 or 3 decades have provided an enormous amount of observational data about the structure of the universe (large scale structure, galactic dynamics, gravitational lensing, light element abundances, the cosmic microwave background...), all of which is basically consistent with the simplest dark matter model ("cold dark matter") and inconsistent with any modified gravity theory. We don't need to imagine any particularly exotic properties to the dark matter, it just needs to be something that doesn't interact with electromagnetic forces (just like a neutrino only much heavier). Even very complicated MOND models fail to match observations, however (unless you add in a bunch of dark matter anyway).
Perhaps the most striking example is provided by observations of the Bullet Cluster last year. Basically we've found a pair of colliding galaxy clusters where the collision has separated the dark matter from the ordinary matter somewhat. Skipping over the details, this provides dramatic evidence that dark matter is real "stuff" - in essentially any modified gravity theory without dark matter, the gravitational forces still have to be coming from the same place as the visible matter! This is a very general argument, and observations like this have more or less put the nail in the coffin of MOND theories.
Astrophysicists are almost universally convinced at this point that something like dark matter exists. We're starting to map its distribution in detail throughout the universe, and the next major challenge will be determining its makeup - either by production in an accelerator or detection in dedicated experiments.
They'll just add 5 more dimensions.
___
If you think big enough, you'll never have to do it.
Actually it is 'evolution'. Because everytime an obstacle comes up, string theory is changed in another untestable manner to accomadate an uncomfortable reality that it is not really science.
/sarcasm
Right so Newtons theory of gravity was perfectly good enough and Copernicus's theories were just fine as well. No need to revise for data.
How on earth did this get +2 interesting. please mod it '-1 author should never breed'.
Evolution like all scientific theories are either rejected or modified over time. If there is enough data that contravenes the theory then the theory is rejected. If a little data points to an error in the original idea then it's modified. Evolution has never been rejected because the core idea is right but things like the mechanism and some subtitles must be changed as data came in.
The conversely the arguments against string theory never needs revision because the formula can accommodate almost every possible observation.
"There are more things in heaven and earth, Horatio, than are dreamt of in your philosophy."
If it can't be tested, it's not science...it's pseudoscience.
String theory makes tons of predictions, all of which align perfectly well with reality. So in that sense, it is testable. However, is does not (yet) predict anything that HASN'T ALREADY BEEN EXPLAINED by other theories. It meshes PERFECTLY with our observations. But nobody has yet used it to predict something that has never been observed before.
Calling string theory "untestable" is ignorant. It makes extremely concrete predictions which are borne out in reality.
String theory should be discarded. It's a fanciful religion that explains nothing, but creates a lot of stuff that needs explaining.
It explains everything we have ever observed. However, this is not enough. String theory will not come into its own until it makes a prediction of a phenomenon we have NEVER observed before. Only then will it prove more useful than current theories.
Now, it's easy to construct a theory which explains everything ever observed -- simply enumerate the universe and say "that's it." But that's not what string theory is. Tomorrow, somebody could discover something in the math that actually makes a testable prediction about something we've never seen before. You have not asserted a single reason why this could not be the case.
One of the sharpest critiques of string theory is that it isn't really one theory -- it's many, many theories (something like 10^500), depending on how the hidden dimensions are wrapped up. It looks like this study showed that a certain flavor of string theory (IIA) might not be able to accommodate inflation -- but not to worry, the string theorists say, there are plenty of other flavors of string theory that might indeed allow inflation after all! But therein lies the problem: no matter how an experiment turns out, one can cook up a version of string theory that agrees with it! What we really need is a meta-theory (M-theory?) that tells us *which* string theory to use, but so far it doesn't exist. This is why some critics call string theory a "theory of anything."
Cheers,
IT
Power corrupts. PowerPoint corrupts absolutely.
Um, yeah. You see I'm going to be extremely skeptical of anyone claiming that the sun cannot be performing fusion when based on the very same theories that describe the pressures and energies required for fusion occurring in the sun we have created fusion right here on earth.
/., he was claiming that EU explained impact craters, as if EU had now replaced the obvious and rather well tested effects of kinetic energy. Einstein didn't and simply couldn't up-end Newton's theory, he could only explain what Newton failed to. EU tries, and summarily fails.
I'm skeptical of anyone who claims not only to have solved problems with the existing theory, but to entirely upturn the existing theory itself even the parts that have extensive verification. Hell the last time I crossed baths with an Electric Universe proponent on
Epicycles were a case of taking something with a clear explanation -- elliptical orbits -- and deciding that no, everything must be comprised of circles. EU is the same thing -- attempting to turn everything into the universe into electricity, desperately inserting it everywhere even if there is no need.
It's one thing to try to explain the things that our current theories can't. It's quite another to try to invalidate well-verified aspects of those theories.
I'm no fan of science politics in this country, but the most basic bar for any theory is that it should not contradict the existing evidence. Relativity could do that, so even as weird and unlikely and unorthodox as it was considered at the time, it eventually won acceptance and now is one of the best tested theories. EU can't do that, and thus even in a perfect system should be rejected.
The enemies of Democracy are
Given that a large part of the theoretical physics world has spent 30ish years on this, isn't it time to move on?
I am in no way a Physicist, but wouldn't "moving on" from String Theory require some genius to propose something else that reconciles Quantum Physics and Newtonian Physics? I don't think the first-step break through of an entirely new theory is going to come from the physics community as a whole, but from a single person or small group. Until that happens, grad students still need something to write thesis papers about...
We are all just people.
String theory is probably the only theory that really supports inflation. If the net energy in the universe is constant, then the net curvature must be constant, therefore it could only appear smaller if curvature were balanced between other dimensions.
We at slashdot are scientists, specialists and kernel hackers. Your FUD will be found out.
I'm not a string theorist, but I am a cosmologist. Here are some thoughts:
Inflation has not been "confirmed" in away way. It's the best explanation for a very very limited number of datapoints we have on the "early" Universe. Very smart people (e.g., Sean Carroll, now at CalTech) have made convincing cases that inflation is actually incoherent in important ways. I have spent quite a bit of time trying to come up with alternatives to inflation, and it's damn hard -- it "works" very well, in the sense that it solves a bunch of problems all at once that are hard to solve individually. But it does invoke plenty of nonstandard physics we've never seen in the Universe, let alone the lab.
Inflation and dark energy are deeply connected. They both require something called "negative pressure". Negative pressure is bizarre, and actually is from a Newtonian perspective a violation of the conservation of energy (in General Relativity, energy is not conserved -- rather a complicated combination of numbers some of which refer to what we'd measure as energy is conserved.) Negative pressure means that if you take a box of the stuff, and let it expand, at the end of the day there's actually more stuff in there than you started with.
String theory should better be known as "a collection of approaches." It does not have the coherence of, say General Relativity, which is a mathematically closed system. Talking about "giving up string theory" is kind of dumb -- essentially what you are saying is "do not try to do the following large class of calculation." There are definitely competitors to string theory, but none have captured the attention of a highly fractious community the way string theory has.
Not sure if anyone's still reading this thread, but I'm happy to talk more about it. Reply with questions if you like!
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Cosmologists are finding that it is impossible to square string theory with Einstein's theory of General Relativity after all. Some say this could even lead to the abandonment General Relativity...
... if only to ensure that string theorists
around the world do not lose their jobs.
Some versions of string theory do make a genuinely interesting prediction. They predict a particle that hasn't actually been observed. A large class of the most studied string theories require adding just this one particle to the standard model, and it has to have spin 2, and mass 0.
That's a great candidate for a graviton, which is also being predicted for some other reasons. When some of the most aestetically interesting versions of string theory turned out to predict not just any particle or whole family of particles, but that specific one, many physicists got more interested in those theories.
However, general and special relativity don't actually predict gravitons - Einstein was able to treat gravity as a strain inherent in space-time and not as something mediated by a particle at all, and get some very testable results. Quantum Mechanics doesn't really require Gravitons either. Actual particle accelerator experiments have satisfied various symmetry theories from just the particles observed, and this again doesn't include gravitons.
There's no practical way to build an accelerator that could even theoretically reach the energies needed to test unification of all four fundamental forces, and gravity is the odd man out that we have no expectation will be integrated by either accelerator experiments or astronomical observations.
Proof of a mediating particle for gravity would still not prove any of the string theorys, but it would give the likelyest of them some fairly strong support. For now, we're stuck - a theory looks mathematically beautiful, and actually makes a prediction, but we aren't sure yet if that prediction is ever going to become testable, and on the other hand we have no categorical proof the prediction is fundamentally untestable. A test would be nice, but so would a stronger reason for saying there could be no test than just that we aren't yet a type 2 civilization, with the energy of a whole galaxy to use, so we are limited by the economics of it.
Who is John Cabal?
Nice troll. ;-)
But seriously, I agree entirely. I came across this a while back, and it sits pretty well with me. Of course most people will say it's ridiculous and laugh it off because <insert derision but provide no sensible argument>.
Either that or they will respond by arguing that it can't work because the combination of a few observations and <insert theory (note: *theory*)> doesn't allow it.
Most folks discussing these things are like primary school kids discussing cars. They don't actually know what they are talking about, but they like to imagine they do and tend to agree on a favourite. Any kid who disagrees is stupid.
I don't therefore I'm not.
I read a few of the arguments from the page, just to know what you are talking about.
Neither Einstein's relativity nor quantum mechanics are physics so we cannot use them as a foundation for our new model (although we should find that the mathematics that works in the real world still applies).We have to discard "modern" physics and return to the classical physics of a century ago. This, perhaps, is the greatest hurdle - to discard our training and prejudices and to approach the problem with a beginner's mind.
whew! I'm so glad we can at least keep mathematics - or some part of it - because reinventing physics without it would be problematic
We must "go down" one more level and propose that all subatomic particles, including the electron, are resonant structures of electric charges of opposite sign that sum to the charge on that particle....The electron is not a fundamental, point-like particle.It must have structure to provide its dipole magnetic field.... The same model applies to the proton and the neutron.
So all the particle physics results indicating the existence of quarks are fictional? Well if we had known they didn't exist we wouldn't have spent so much time and money pinning down their properties.
When we accelerate electrons or protons in an electromagnetic field they become less responsive to the fields the more they are accelerated. This has been interpreted as an increase in mass. However, charges have no mass.
I (and particle physicists) much prefer E^2 = (pc)^2 +m^2*c^4 where m is the rest-mass; an unchanging invariant property. only the momentum p has relativistic terms in it.
The notion that matter can be annihilated when normal matter meets antimatter is a confusion of language. Matter can neither be destroyed nor created nor can matter be exchanged for energy. Einstein's E = mc2 refers to mass, a property of matter, not matter itself.
The most collapsed form of matter is the neutrino, which has a vanishingly small mass. However, the neutrino must contain all of the charges required to form two particles - a particle and its antiparticle. This symmetry explains why a neutrino is considered to be its own anti-particle. A neutrino may accept energy from a gamma ray to reconstitute a particle and its anti-particle. "Empty space" is full of neutrinos. They are the repositories of matter in the universe, awaiting the burst of gamma-radiation to expand them to form the stuff of atoms. The weird "zoo" of short-lived particles created in particle accelerators and seen in cosmic rays are simply unstable resonant systems of charge.
We must abandon our peculiar phobia against a force acting at a distance. And we must give up the notion that the speed of light is a real speed barrier. It may seem fast to us, but on a cosmic scale it is glacial. Imposing such a speed limit and requiring force to be transmitted by particles would render the universe completely incoherent.
Holy friggin' hell. check out http://www.physicstoday.org/vol-56/iss-10/images/p48fig1.jpg or http://en.wikipedia.org/wiki/Image:First_Gold_Beam-Beam_Collision_Events_at_RHIC_at_100_100_GeV_c_per_beam_recorded_by_STAR.jpg image created at RHIC. Think about what standard physics implies about the result versus "Electric physics"
Electric Physics
1. individual gold atoms are accelerated perhaps to >c
2. energy is added into some electric fields within the atom
3. the electric fields do not interact with any neutrinos until the atoms near each other
4. the electric fields interact with thousands of undetected neutrinos at the exact point where the atoms collide (kind of
There's nothing more annoying than pontification from ignorant armchair physicists.
I understand your irritation, but there is no need to insult Stephen Hawking.
30 years is not a long time! The experiments themselves are taken that long - the LHC (Large Hadron Collider) alone has taken 20 years.
I don't get these people running around going "omg it's 30 years, and they haven't solved the universe yet". jeez.
String theory has produced a lot of useful science and mathematics. Even if string theory is wrong (which it probably is) it is needed to expand our understanding. It is not like a car journey where you chose a road then have to double back if you took the wrong turn.