String Theory and the Multiverse

[Chalnoth]

Here are some thoughts, not that i claim to understand it..

YouTube - Imagining the Tenth Dimension part 1 of 2

Ugh, no, please. That video is horrifyingly wrong. I mean, sure, the extrapolation up to 4 dimensions is okay. But beyond that it's just made-up silliness. They confuse lots of very different concepts in physics, and mash them together in an extremely inconsistent way.

A dimension is just a way in which it is possible to move. Full stop. We can't really visualize more than three dimensions, but we can make use of various mental constructs to attempt to. Most frequently, we imagine our own three dimensions as existing on some sheet, with the next extra dimension being perpendicular to that sheet. The beginning of that video above does a pretty good explanation of that. Just, for the love of all that is good, stop paying it any attention after it finishes with time.

As for string theory, the basic argument is this: string theory makes a proposal for the behavior of fundamental objects. It proposes, specifically, that the fundamental objects are strings, and that they can wiggle in a variety of ways. Now, we want this to be a physical theory of physical objects, so one requirement of the theory is that whatever numbers we assign to the string, that choice of numbers cannot possible affect its real behavior. This is analogous to, for instance, the statement that it doesn't really matter whether I say my cousin's house is 50 miles away or an hour's drive away: the real distance is unchanged no matter what I call the distance.

Now, when you carefully write down a theory of strings and how they behave, you find that when you do make a change in the numbers used to describe the string, there's a little extra factor that sits around: there's a change in how the string actually behaves. Careful analysis shows that this factor only disappears if the string exists in a specific number of dimensions, and that number depends upon exactly what sorts of wiggles the string can undergo (this is what differentiates between Heterotic, and type IA, IB, IIA, IIB string theories: the types of wiggles allowed).

I haven't gotten into M-theory yet, which is an interesting topic in and of itself, but this already raises a distinct question: the various string theories predict either 10 or 26 dimensions in total (depending upon the theory). We only perceive four (3 space, 1 time). So how can they possibly be correct? Well, for a number of theorists, this alone is reason enough to ignore string theory. But for the theory's proponents, other attractive features of the theory make them want to soldier on and see if there is anything to it (the most spectacular of which is that string theory predicts quantum gravity).

The ways in which there might actually be more dimensions out there than we can detect are twofold:
1. It is possible that we are stuck on a 3+1 dimensional surface. The other dimensions are out there, but all of the particles that make up what we can observe are stuck on this surface (electrons, protons, neutrons, photons, and so on). Within string theory, this is a completely natural expectation. But there is a subtle complication: most of the particles we know of can be easily constrained to be unable to escape a surface like this (called a brane). Gravity cannot. Gravity always tends to escape, but this turns out to be a potential blessing in disguise for the theory: maybe this explains why gravity is so exceedingly weak (gravity is about 10^40 times weaker than electromagnetism). The escape of gravity from the brane also indicates that if it turns out that our universe is like this, then detailed tests of gravity might show us whether or not it's true, as if it is we should see gravity "leak" into this higher-dimensional space.

2. It is possible that the other dimensions are just incredibly small. Think of it this way: take a thin wire. Say a guitar string or a piano wire. Far away from the wire, it looks perfectly one-dimensional: the only way you can move along the wire is along its length. Movement around the circumference doesn't do anything of note.

But what if you were very, very small? So small that the circumference of the wire was huge compared to you? In that case, the circumference around the wire would mean an awful lot.

Thus these other dimensions might exist, but be exceedingly tiny. Detailed tests of physics at very short distances may potentially illuminate such dimensions (which also means tests of physics at high energies).

Note that not only is either of these possibilities possible, but a combination of the two is also possible.

 

[Chalnoth]

This is just a general question about a subject I know almost nothing about. I was wondering how scientists came to the conclusions about multiple universes and the various elements of String theory. All I really know is it's an attempt at a unified theory and from Einstein to Hawkins physicists have lamented the failure of science to produce one.

Your thoughts...

I talked a bit about string theory above, but it seems that you had another, perfectly distinct question to that of string theory: multiple universes.

First, I'd like to make a little pedantic note: "multiple universes" is an oxymoron. Universe is, by definition, all that exists. You can't have a second "all that exists". Maybe some day we'll come up with an adequate, accurate name for the region of the universe which we can observe and interact with, but for now we have this really horrible language floating around.

That little rant aside, there are multiple ways in which people might talk about a sort of "multiverse":

1. It is possible that there exists stuff that is outside the region which we can observe. Heck, I'd say it's more than possible: it's absolutely guaranteed. If there was a boundary to the universe just at our horizon, then we should see some sort of change in the universe up to that boundary. But we don't see anything like that: as near as we can tell, the region which we inhabit is almost perfectly smooth on large scales. So there's no reasonable way it can end just beyond what we can see. Because of this, our naive expectation is that the universe as a whole is really, really big: vastly larger than the piece of it that we can observe.

2. It is possible that far away from the region which we can observe, the laws of physics take on a different form. This is an idea that stems from our observations of high-energy physics: within high-energy physics, it appears that we have sort of written into our laws of physics some of what are called "spontaneous symmetry breaking" events. What does this mean?

Well, a good analogy is to consider spontaneous symmetry breaking in a different situation: a magnet. A magnetic metal has the property that the atoms in the metal are themselves like little magnets, and due to the way they interact with the other atoms, like to line up in the same direction with their neighbors. Now, they don't care what direction that happens to be, just as long as it's in line with the nearer atoms. So, what happens is that when the metal is at very high temperatures, the atoms are all oriented randomly: the high temperatures are bumping the atoms around so much that the small attraction to pointing in the same direction as one another is completely outdone by this random motion.

So, what happens when the magnetic metal is cooled? As it gets cooler and cooler, the attraction of nearby atoms becomes more and more significant, because they aren't bouncing around as much. Once the metal hits a critical temperature (similar to a boiling or melting point), the attraction between nearby atoms overrides the random motion, and nearby atoms start to lock together.

If the entire rock is all cooling down at the same rate, then what happens is that little pockets of atoms that are locked together start to form. These pockets then grow. If the cooling is fast, then lots and lots of little pockets end up forming, each with the atoms pointing in a different direction. If the cooling is slow enough, then the formation of the pockets is slower, and one pocket may spread out before any others form: all the atoms point in one direction, and you have a magnet (note: for making artificial magnets, what we do is we cool the metal down in the presence of a strong field, so that we sort of force the atoms to line up in the direction we want).

Something similar might have happened early in our region's history: perhaps our region is but one pocket of many, with others having different sorts of "orientations" of the vacuum. In this way, the various forces might have different strengths, or they may even have different forces altogether. We don't yet know the full extent of what is possible here, as we don't yet have a theory of everything. There are a large variety of proposals for various ways in which this sort of thing can happen, including but not limited to the string theory lanscape.

3. A third way in which physicists talk about a "multiverse" is to describe the many worlds interpretation of quantum mechanics. The basic premise of this idea stems from a simplification of quantum mechanics. Classical quantum mechanics basically states that the fundamental parts of nature do two different things: when you aren't looking, they are wavefunctions that follow Shroedinger's equation. When you take a measurement, that wavefunction collapses into one of the states described by the wavefunction. This description of quantum mechanics works fantastically well, and has been supported by experiment after experiment. But for a long time has left many theorists feeling uneasy: it's asking the universe to behave differently when we are looking than when we aren't! As a result, over the decades many theorists have proposed a number of potential ways to get around the collapse of the wavefunction, or to find a reasonable explanation for it.

Well, in 1957, around three decades* after the first solid formulation of quantum mechanics, Hugh Everett had a remarkable insight: we don't need the wave function to collapse at all to explain all of our experiments! All that is necessary is the way these wavefunctions behave: we let them move forward, evolve, interact, and we find that the theory automatically predicts the appearance of wavefunction collapse. If we go back to the old Schroedinger's Cat thought experiment, for instance, and ask what happens if we just state that there is no collapse of the wavefunction, then this predicts that there will be a component of the wavefunction with the cat dead, and a component with it alive. When the box is opened, there will be a component of the wavefunction of the unethical researcher that will see the cat dead, and a component that will see the cat alive. Because of the way quantum mechanics works, the two components can't "talk" to one another: the researcher will always see either a dead or alive cat, and not the two different components.

Obviously this has some very interesting consequences, which has led many to reject the idea, in my opinion too hastily. The most significant of which is the result that the entire wavefunction of the universe encodes not only the reality that we observe, but many alternate realities as well. Note that it doesn't necessarily encode all possibilities: the wavefunction is still a result of its evolution from earlier times. But this does say that it includes very, very many possibilities, perhaps an infinite number: there quite literally could be an infinite number of Chalnoth's doing both very similar and very different things from the part of the wavefunction that wrote the post you are reading now.

*This is actually arbitrary, as quantum mechanics evolved slowly over a long period of time, but the point remains that it took a long time for this idea to appear. But I think it's a fairly reasonable counting, as it marks when the photon was first accurately described.

 

[ArnautDaniel]

This is just a general question about a subject I know almost nothing about. I was wondering how scientists came to the conclusions about multiple universes and the various elements of String theory. All I really know is it's an attempt at a unified theory and from Einstein to Hawkins physicists have lamented the failure of science to produce one.

Your thoughts...

They whipped out a crack pipe, inhaled with vigor, and wrote out whatever came to mind in impenetrable, unsolvable, inconsistent, and incomplete mathematics.

They then stared down everybody that tried to call them out for talking utter nonsense.

...kind of what the medieval scholastics did when people tried to make sense of their theological speculations.

 

[Chalnoth]

They whipped out a crack pipe, inhaled with vigor, and wrote out whatever came to mind in impenetrable, unsolvable, inconsistent, and incomplete mathematics.

They then stared down everybody that tried to call them out for talking utter nonsense.

...kind of what the medieval scholastics did when people tried to make sense of their theological speculations.

Why must you make stuff up? I mean, not understanding it is okay: this isn't terribly easy stuff. But in failing to understand these theories, why must you make up disparaging scenarios that are so far from reality as to be completely laughable?

 

[redwards]

This is just a general question about a subject I know almost nothing about. I was wondering how scientists came to the conclusions about multiple universes and the various elements of String theory. All I really know is it's an attempt at a unified theory and from Einstein to Hawkins physicists have lamented the failure of science to produce one.

Your thoughts...

I would point out only this:

1. String theory and multi-verse theories have nothing to do with each other.

2. Both are purely hypothetical. We don't have supporting evidence for either of them, as far as I'm aware. Though I don't think we expect to have evidence for multi-verse theories, we understand that we haven't gotten close enough to being able to look at it yet. String theory, on the other hand, seems like a fairly stagnant hypothesis, and my understanding is that a lot of physicists wrote it off as a useful avenue of study a long time ago.

 

[Chalnoth]

String theory, on the other hand, seems like a fairly stagnant hypothesis, and my understanding is that a lot of physicists wrote it off as a useful avenue of study a long time ago.

String theory research is still alive and well in theoretical physics departments. Only a very small minority have "written it off". Most consider it interesting and worth investigating.

 

[redwards]

String theory research is still alive and well in theoretical physics departments. Only a very small minority have "written it off". Most consider it interesting and worth investigating.

The reason physicists study string theory is because no one has had a better idea for a ToE yet. As far as I'm aware, no advances of any kind have been made in String theory in the past 25 years, particularly in terms of attempting to actually use it to reference the natural world or in at least making this 'theory' falsifiable. It begins to resemble a religion.

As with many, however, I have high hopes that the LHC will reveal something new which will give the physicists of the world -- the ones who haven't lost themselves completely to the apparently useless field of string theory -- something new to pursue.

 

[WolfBitnGodSmittn]

im going to break in with what may or may not be a stunner..

You guys ARE aware that string theory is old news debunked, an already sunken ship. Mainstream scientists have been jumping that ship for years. String theory doesnt even qualify as a valid 'theory' by definition.

Many scientists have begun movements to really expose it for what it is, and these people are mainstream scientists, not 'christian' scientists.

I find it interesting that an atheist would laugh at the faith of a christian, when it takes as much or more faith to believe in string theory. One of its main theorists, Muth, even admits that the math just doesnt add up, there is no viable theory.

 

[corvus_corax]

im going to break in with what may or may not be a stunner..

You guys ARE aware that string theory is old news debunked,

(emphasis mine)
Full stop.
Debunked?!????
Really????
Nope, you're incorrect.
IOW you are wrong.

 

[Chalnoth]

The reason physicists study string theory is because no one has had a better idea for a ToE yet.

String theory has merits of its own. The most significant of which is that it predicts quantum gravity. Just to push how significant this is, people had been working on quantum gravity for in the range of 50 years or so with little success. Only fairly recently with loop quantum gravity has there been a reasonable alternative to string theory as far as quantum gravity is concerned.

As far as I'm aware, no advances of any kind have been made in String theory in the past 25 years,

Look up the second superstring revolution.

particularly in terms of attempting to actually use it to reference the natural world or in at least making this 'theory' falsifiable.

It may not be falsifiable at this point, but it has spawned a great many ideas on the possible nature of reality which are actually experimentally testable, a number of which have actually been falsified with current experimental data (there was some question early on in the days of dark energy, for instance, that if we live on a 3+1-dimensional brane, and the extra dimensions are of just the right size, then gravity will start to "leak" into the extra dimensions on very large scales, which would, in turn, cause an accelerated expansion. Detailed investigation demonstrates that this can't explain the current accelerated expansion, but it's a good example of how string theory has inspired experimental tests of various possible scenarios.

It begins to resemble a religion.

I don't see how "string theory is difficult" makes it resemble a religion in any way, shape, or form.

As with many, however, I have high hopes that the LHC will reveal something new which will give the physicists of the world -- the ones who haven't lost themselves completely to the apparently useless field of string theory -- something new to pursue.

I find it amusing that you can call an entire field, of which you have no expertise whatsoever, useless.

 

[ArnautDaniel]

Why must you make stuff up? I mean, not understanding it is okay: this isn't terribly easy stuff. But in failing to understand these theories, why must you make up disparaging scenarios that are so far from reality as to be completely laughable?

Why do you equate thinking the theories are BS and nonsense with not understanding them?

In fact you have yet to demonstrate any understanding of the theory that couldn't be gotten from any popular book on the subject.

As for the

"impenetrable, unsolvable, inconsistent, and incomplete"

remark...

...well plain vanilla quantum field theory is "inconsistent" and "incomplete" by the yardstick of any working mathematician.

The fact is the path integral doesn't have a well-defined measure, and then there's all that renormalization one does to compensate for problem infinities...again getting back to the lack of a well-defined measure.

String theory of course has all the problems of quantum field theory, and still more problems.

It is "unsolvable" simply because no one has ever solved a problem that could be compared to empirical values.

As for "impenetrable", well it is.

 

[WolfBitnGodSmittn]

wrong? lol i think not

According to the true definition of a scientific theory, a true 'theory' must be 'falsifiable'. Simply put this just means it can be tested to provide viable evidence that it is a plausable theory or not.

If a theory is 'falsified' it means it was proven false and holds no merit. If a theory is not 'falsifiable' it means that it cannot be tested in any way, and is more akin to pulling a rabbit out of a hat, so it holds no merit. If it IS falsifiable and proves to hold merit, it is then a valid 'theory' by definition.

The BEST the evolutionist has concerning the cause of inflation of the universe, does not qualify as 'theory' by definition...

Referance..

An atheistic scientist can not provide a proper theory as to the cause of the bang, because by definition it is not falsifiable

We can base this on the following statement of facts from notable scientists...

Prominent critics include Philip Anderson ("string theory is the first science in hundreds of years to be pursued in pre-Baconian fashion, without any adequate experimental guidance", New York Times, 4 January 2005),

Sheldon Glashow ("there ain't no experiment that could be done nor is there any observation that could be made that would say, `You guys are wrong.' The theory is safe, permanently safe", NOVA interview),

Lawrence Krauss ("String theory [is] yet to have any real successes in explaining or predicting anything measurable", New York Times, 8 November 2005),

Peter Woit (see his blog, article and book "Not Even Wrong", ISBN 0-224-07605-1) and Carlo Rovelli (see his Dialog on Quantum Gravity

Peter Woit's Not Even Wrong weblog

^ P. Woit (Columbia University) String theory: An Evaluation,Feb 2001, e-Print: physics/0102051

^ P. Woit, Is String Theory Testable? INFN Rome March 2007




So... If the atheist or evolutionist has no viable THEORY concerning the causation of the big bang, they are FORCED to keep God on the table as being just as viable a theory...

 

[Chalnoth]

Simple falsifiability is no longer considered a valid criterion for distinguishing science from non-science, as it turns out to be too simple.

All objections to date about string theory, including those you mentioned, can all be compressed into a single statement: string theory is hard. I don't know why some people think that a theory of everything should be easy.

 

[ArnautDaniel]

Simple falsifiability is no longer considered a valid criterion for distinguishing science from non-science, as it turns out to be too simple.

My suspicion here is that this results from certain people saying "my favorite theory fails the simple falsifiability criterion, therefore that criterion isn't valid."

Would you care to provide an alternative criterion for distinguishing science from non-science?

 

[Chalnoth]

My suspicion here is that this results from certain people saying "my favorite theory fails the simple falsifiability criterion, therefore that criterion isn't valid."

No, it follows from not-strictly-falsifiable theories proving useful to the progress of science.

Regardless, I don't know why people complain about this when nobody in their right might is actually asserting that string theory is true. If people started doing that without good experimental support, well, then that would be bad. But the fact remains that string theory, though not strictly falsifiable, has inspired a very wide variety of ideas that can be experimentally verified.

Would you care to provide an alternative criterion for distinguishing science from non-science?

Well, the fact of the matter is that science is always fluid and changing. So the only real way to reliably distinguish science from non-science is that anything that can be considered science is part of a process of discovering the nature of reality that relies upon independent confirmation and analysis of results, formal logic, and physical evidence.

What precisely this consists of changes as people discover new possibilities, and recognize ways in which they are misled.

 

[ArnautDaniel]

No, it follows from not-strictly-falsifiable theories proving useful to the progress of science.

So you are saying falsifiability is not a criterion because non-falsifiable theories are might be useful (or may have been useful)...sounding circular here...

Would you care to provide an example?

Regardless, I don't know why people complain about this when nobody in their right might is actually asserting that string theory is true. If people started doing that without good experimental support, well, then that would be bad. But the fact remains that string theory, though not strictly falsifiable, has inspired a very wide variety of ideas that can be experimentally verified.


Well, the fact of the matter is that science is always fluid and changing. So the only real way to reliably distinguish science from non-science is that anything that can be considered science is part of a process of discovering the nature of reality that relies upon independent confirmation and analysis of results, formal logic, and physical evidence.

What precisely this consists of changes as people discover new possibilities, and recognize ways in which they are misled.

Wow, this is all wonderfully philosophical, vague and non-specific. It is nice to have opinions and be able to ramble on about them in the abstract.

Would you care to get specific about something?

 

[Chalnoth]

So you are saying falsifiability is not a criterion because non-falsifiable theories are might be useful (or may have been useful)...sounding circular here...

Would you care to provide an example?

Here's a simple one: dark matter. Now, it just so happens that there's a lot of the stuff around, but it is in principle possible that there could have been too little of it to detect gravitationally, and also too weakly-interacting to detect in the laboratory. This doesn't mean that dark matter is an unscientific concept, just that it is a verifiable one, instead of a falsifiable one. It just so happens that this one turned out to be true.

 

[ArnautDaniel]

Here's a simple one: dark matter. Now, it just so happens that there's a lot of the stuff around, but it is in principle possible that there could have been too little of it to detect gravitationally, and also too weakly-interacting to detect in the laboratory. This doesn't mean that dark matter is an unscientific concept, just that it is a verifiable one, instead of a falsifiable one. It just so happens that this one turned out to be true.

"Dark matter" was postulated to exist after astronomers noticed that the velocities observed for objects orbiting in galaxies didn't match the predictions of Newtonian or Einsteinian gravity using the observed "light" matter.

So there is the undeniable problem - the visible matter in galaxies does not explain velocities of revolution observed.

There are two solutions: (1) both Newtonian and Einsteinian gravitational theories are wrong (2) gravity is right, but there is more matter than we can see.

The second things basically just means there is a bunch of stuff that isn't shiny stars and there are more things that aren't shiny stars than we thought.

In fact I'll give you a simple example of something that would qualify as "dark matter" - Earth.

The Earth is in fact dark matter - it isn't a shiny star and it exerts a gravitational force.

Another example would be Jupiter. It is entirely possible that there are just an unbelieveable number of Jupiters floating around the galaxies.

Black holes are also "dark matter".

No one ever doubted that there were things we couldn't see that caused gravity, the issue was the ratio of this stuff to the things we could see (i.e. stars). The problem is that stars don't constitute the dominant form of mass in the universe.

...

Now this isn't the same thing at all vis a vis string theory -

Dark matter was postulated to explain an observed empirical problem

No prediction of string theory that isn't also a prediction of other conventional theories has been observed empirically.

Now if someone had postulated "dark matter" was the dominant form of mass in the universe before the observations were made you might have had a comparison, but no one did. In fact it was such a surprise that people put a lot of effort into explaining away the observations.

Try again.

 

[Chalnoth]

"Dark matter" was postulated to exist after astronomers noticed that the velocities observed for objects orbiting in galaxies didn't match the predictions of Newtonian or Einsteinian gravity using the observed "light" matter.

And string theory was postulated after physicists noticed that quantum mechanics and general relativity are incompatible. That's an undeniable problem, one which string theory solves. I see no difference between these two scenarios, other than the fact that string theory is orders of magnitude more difficult.

No prediction of string theory that isn't also a prediction of other conventional theories has been observed empirically.

Except that it predicts quantum gravity.

 

[WolfBitnGodSmittn]

Simple falsifiability is no longer considered a valid criterion for distinguishing science from non-science, as it turns out to be too simple.

All objections to date about string theory, including those you mentioned, can all be compressed into a single statement: string theory is hard. I don't know why some people think that a theory of everything should be easy.

i find this simplistic, since string theory cannot even be tested. (Actually with our newer particle accelerators it can be but still hasnt proven valid)

How do you account for the growing number of scientists who scoff at it even being called a 'theory'?

How do you account for one of string theories main proponants, Muth, admitting it doesnt even work out?

It seems to me it takes more faith to give string theory any credence, than it does to believe "God did it"


What do you know of Muth's acertion that string theory can explain the moments before the actual bankg of the big bang?