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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."
I don't think ANYTHING can accomodate inflation.
Just disrupt the deflector shield with a tachyon burst.
"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)
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.
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.
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.
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.