The Official Theoretical Physics Thread!

[BinoAl]

The title says it all. I'm hoping to at least have a few people discuss this with me. Let me start with something I've been thinking about a lot recently: String theory. In particular, how it handles the existence of multiple dimensions other than x,y,z, and time. Granted, I haven't read too much into it, but what I always hear/read is that "There are as many as 13 extra dimensions, but tightly coiled up so we can't observe them". I believe that is total bs. First of all, that's describing an entire dimension in terms of another dimension. That's like me saying "Time is moving in a zig-zag". I do believe that there are multiple dimensions, such as "sideways time" (google it :p), but saying the dimensions themselves are "too small to observe" just makes no sense whatsoever to me.

[Necropolis]

In the case of string theory, the dimensions are nothing more than descriptions of attributes that a string has that are not definable using space time directionality. These dimensions describe ways that a string can manipulate itself and have an effect on its properties when interacting with other strings. The fact that they use the word dimensions does not indicate anything approaching what we observe and describe as dimensions in a macro sense.

And considering that those dimensions are local to the string itself, which is infinitely smaller than the tiniest observable particle of matter means that they are, yes, too small to observe directly. They have been described mathematically, which is really all that a dimension is: a mathematically described direction of object manipulation.

[PatrickSJ]

I thought that a dimension is merely a measurement of reality which cannot be broken down into smaller base measurements or properties, e.g., rate is broken down into distance and time. If I said every matter/energy exhibits a state of sangfroid then wouldn't sangfriod be a dimension of reality?

String theory operates under the assumption that matter/energy has additional base measurements in order to match observed behavior and theoretical models. However, while the math can be written to describe the model the individual base properties cannot be directly measured using existing tools.

It has been a while, but I thought that is how it worked.

---

If you'll allow it I have multiple realities (dimensions) where x,y,z,t are the same but sangfroid varies. Perhaps it varies as discreet state changes or perhaps it follows a curve. Assuming multiple realities where the lowest sangfroid is 0 and the highest sangfroid is 1 then realities where sangfriod approaches 1 all matter/energy, and thus the people comprised of said atoms exhibit higher levels of coolness when compared to our reality.

[Sajuuk]

Granted, I haven't read too much into it, but what I always hear/read is that "There are as many as 13 extra dimensions, but tightly coiled up so we can't observe them"

I haven't read too much into it either. However, what I have read is that the math is beautiful, the ideas expansive, but it remains (to my knowledge) untestable. As long as it remains untestable it's useless in terms of science. Without evidence based in the results of experimentation, it's only an idea, and resides in the same sort of place faith myths do. It's basic in theoretical physics to say if your idea disagrees with experimentation, it doesn't matter what your name is or what honors you have, you're wrong. In this case we can't rule the ideas out, but in the same case we can't consider them like they're already legitimate.
Little rant.

It's good Necropolis answered the question though.

[BinoAl]

In the case of string theory, the dimensions are nothing more than descriptions of attributes that a string has that are not definable using space time directionality. These dimensions describe ways that a string can manipulate itself and have an effect on its properties when interacting with other strings. The fact that they use the word dimensions does not indicate anything approaching what we observe and describe as dimensions in a macro sense.

And considering that those dimensions are local to the string itself, which is infinitely smaller than the tiniest observable particle of matter means that they are, yes, too small to observe directly. They have been described mathematically, which is really all that a dimension is: a mathematically described direction of object manipulation.

Aha, that actually makes a lot of sense. I hadn't thought of dimensions as properties of objects, i was merely thinking of them as... directions, I guess. This will definitely help out my understanding of a lot of things.

[Gilberreke]

What's interesting is that one could say that when trying to observe the regular three dimensions from within the coiled up dimension, that dimension will appear regular, while the regular dimensions are coiled.

Imagine it like this: take the coiled up local dimensions and stretch them out, while stretching, the regular dimensions will deform and coil up.

You'd have to do the math to see if this is true exactly, but it's certainly a possibility given the construct mathematically and it helps the understanding of the spatial relations.

Similarly, to better understand multi-dimensionality, we could envision a creature that moves along X, Y and Time, while observing Z to be a dimension along which its consciousness travels, as ours does along the time axis.

Remember that things making "sense" is subjective to how we experience the universe.

[CreeperCommando]

A way to 'visualize' the 13 dimensions is that the 3 standard spatial dimensions are also 'coiled up' but that they just happened, due to the creation of the world (BigBang/pre-BigBang), be the only ones with a radii -> infinity = we see them as linear in nature. An effect to consider is if you 'stand inside' a coiled dimension you wouldn't experience it as coiled, you would just return to your starting point if you travelled perfectly straight forwards (think Matrix movie when protagonist ran around inside the subwaystation).
Thus the 3 standard dimensions are simply special cases of the rest (I don't really remember exactly why only three was expanded but I think there was kinda a reason to it).

An example taken straight from book is if you'd be an 2d creature living in a plane that exist in our world, you'd pretty much also say BS that a third dimension would exist and claim it was described using the two first ones to describe a superfluous dimension, 2D creatures would have as much trouble imagining 3D as we have imagining 4D (in spatial terms only).

I'd recommend popular scientific book of Brian Greene, 'Elegant universe' http://www.amazon.com/Elegant-Universe- ... 963&sr=1-1. Read it when I was 14-15 years old and loved it.

Yeah the string theory is partly(!) metaphysics, although it predicts some stuff that may be observable such as supersymmetry but there is still Occham's razor if only parts of predictability can be observed.
See it like this, if we only observe things on earth, we use Newtons law of gravity, but in extreme cases we need the general theory of relativity to predict all, but if we only needed to predict one special case (for example mercury's shift in orbit), then the whole of general theory of relativity may be overkill.

On a different note, on the breaking news of neutrinoes travelling faster than light, I want to see someone calculate General theory of relativity into the equation first (experiment happened inside a constant accelerating field!) before further claims... it's kinda a fact that particle physicists need to know special theory of relativity BUT NOT necessarily the general...

By the way, is this discussion aimed towards popular scientific discussion or a more educated level?
would be good to know which vocabulary to use ^^

[Gilberreke]

By the way, is this discussion aimed towards popular scientific discussion or a more educated level?
would be good to know which vocabulary to use ^^

I think whatever people in this thread can follow is ok. I'd go with educated level understanding, but with a more popular scientific approach to talking about it for maximum discussion?

And yeah, CreeperCommando eloquently expanded upon a few of my points about perception of multiple dimensions. Especially "coiled up" is a term that only makes sense when perceiving from other dimensions. That's the key point to take away for the OP :)

There's a simplified presentation somewhere that explains multi-dimensionality well with cartoons of 2D space, anyone have a link? It was popular a while ago.

[BinoAl]

By the way, is this discussion aimed towards popular scientific discussion or a more educated level?
would be good to know which vocabulary to use ^^

Use more educated level, definitely. I usually know most words, but I can google the few I don't ^.^
Also, we can discuss anything, I was just providing a bit of a starting point. One that I didn't particularly understand too well and could learn more about ;D

And yeah, CreeperCommando eloquently expanded upon a few of my points about perception of multiple dimensions. Especially "coiled up" is a term that only makes sense when perceiving from other dimensions. That's the key point to take away for the OP :)

See, the phrase "from other dimensions" is one thing I don't completely get, either. It's probably just bad choice of wording, but it makes me think of dimensions in the sci-fi sense, where you're going to an alternate dimension full of strange aliens and things, rather than viewing it as compared to different dimensions than space and time.

[CheGiuAn]

(first of all, sorry, I haven't read the whole topic, but maybe I will in the future, I just want to add what my Maths teacher said about dimensions, so: )

So, we know that there are different dimensions.
We know that for example a sheet of paper is a 2D object, and for example a qube is a 3D object. My math teacher said, that (as we know, humans are 3D creatures) a creature on a dimension level can't comprehend the dimension above it (like the 4th dimensions for humans). Like if we consider an ant a 2D creature, on the edge of a 2D paper sheet, and this 2D creature wants to get from point A to point B in it's 2D world (from one edge of the paper to the other), it has to walk the distance between A and B points. But if a human bows the paper into the shape of a cylinder, so that the two edges reach each other, the 2D creature gets from point A to point B immediately (point A becomes equal to point B), and presumably, the ant (being a 2D creature in this situation) can't comprehend what happened.

[CreeperCommando]

BinoAI wrote:

Gilberreke wrote:
And yeah, CreeperCommando eloquently expanded upon a few of my points about perception of multiple dimensions. Especially "coiled up" is a term that only makes sense when perceiving from other dimensions. That's the key point to take away for the OP :)

See, the phrase "from other dimensions" is one thing I don't completely get, either. It's probably just bad choice of wording, but it makes me think of dimensions in the sci-fi sense, where you're going to an alternate dimension full of strange aliens and things, rather than viewing it as compared to different dimensions than space and time.

Yeah, it's easy to get riddled by these things if you aren't clear on definitions and viewpoints.
Unless said otherwise I'm only referring in spatial dimensions when talking about dimensions.

Dimensions:
It's important to see this as something not physical but measurable(in this case, perhaps not correct but still adequate definition), sci-fi tries to give the name a physical property and thus it easily gets harder to understand the correct thinking (better to call them parallell linked or unlinked worlds IMO).
A spatial dimension has the property of having a definitive distance associated between every two points measured, the number of dimensions simply tells the least amount of numbers needed to define both distance and direction in the given space. Same stuff applies to chrono/time dimensions.

Coiled dimensions:
This means loosely 'you can travel infinitely along this dimension, but it has a finite length'. Important to note coiled in this sense DOES NOT means like a coiled rope or snake, instead it means it has properties similar to circles.
This is closely connected to a circles circumference as having a definite length but still being infinitely traversable
Another way to see this if only considering one coiled dimension, as existing in one dimension only. There exist no such thing as passing by or go beside, so if you would start to 'build' a longer and longer ruler. Sooner or later you are gonna poke yourself in your 'bum' with it O.o (interesting is that if a creature could live inside a single dimension, it would only be able to see max two 'pixels' one in each direction, if it has two eyes no either side of its body).

Examples (trying to show that this isn't to hard to imagine):
*The old mario game with the POW block in the middle of the screen (http://www.mariowiki.com/Mario_Bros._%28game%29) had one of two dimensions coiled up as in that if you ran outside the left side of the screen you'd appear on the right side and vice versa.
* If one of minecrafts dimensions, say X-axis, was coiled it would mean that if you travelled a straight path along the X-axis you'd sooner or later end up where you started. Counting the blocks would thus give the definitive distance.

To small to be observable:
One principle of physics is 'the less you look, the simpler it is' (well not really, but most theories work that way).
To small to be observable simply refers to our equipment to observe direct effects, if I remember correctly we'd need a particle accelerator the size of the solar system to be able to harness adequate amounts of energies for 'opening up' these extra dimensions

Examples:
*Imagine a pole standing in the distance, far enough so you can hardly discern it. If someone wanted to know spatial information relative to it, say for example how high a coloured marking is on it you'd only be able to give information relative to the length of the pole. Now let's say you'd want to know more about this fascinating pole, so you whip forth some mighty binoculars, and upon closer inspection you now see instead of a line, a surface! You have suddenly with the use of adequate equipment become able to measure an entirely new attribute of the pole!
*A parallell phenomena, it was with the invention of the microscope we discovered germs for the first time. In this case string theorists predict the existence of 'germs' but we cannot build our 'microscope' well enough to see them


When talking about dimensions from an 'outside the box view' it's important to actually 'stand outside the box', this has to do with set theory, when talking about for example spatial 4D objects/space it's not possible to view them inside a 3D room.

[BinoAl]

Ohh, so that's what they mean be coiled... That makes quite a bit of sense. It hadn't occurred to me before that dimensions could pertain to only a single atom, I was only thinking in macro dimensions.

Also, on the subject of neutrinos traveling faster than light: I've heard that that would allow us to send messages into the past. How exactly does that work? I'm by no means saying I believe the neutrinos actually traveled faster than light, but I can't seem to wrap my head around how it would affect time if it happened.

[M!C]

Also, on the subject of neutrinos traveling faster than light: I've heard that that would allow us to send messages into the past. How exactly does that work? I'm by no means saying I believe the neutrinos actually traveled faster than light, but I can't seem to wrap my head around how it would affect time if it happened.

I think the thought of time travel is somewhat linked to time dilation effects. The faster a particle the less time effects it "experiences" in relation to its surroundings. According to the equations time comes to a standstill when reaching light speed. So going further in that line of thought , faster than light travel would make the particle go backwards in time.
This does however only affect the travelling particle (or so I believe), so the particle would get "younger" but not travel back in time.

[BinoAl]

Also, on the subject of neutrinos traveling faster than light: I've heard that that would allow us to send messages into the past. How exactly does that work? I'm by no means saying I believe the neutrinos actually traveled faster than light, but I can't seem to wrap my head around how it would affect time if it happened.

I think the thought of time travel is somewhat linked to time dilation effects. The faster a particle the less time effects it "experiences" in relation to its surroundings. According to the equations time comes to a standstill when reaching light speed. So going further in that line of thought , faster than light travel would make the particle go backwards in time.
This does however only affect the travelling particle (or so I believe), so the particle would get "younger" but not travel back in time.

How does it get "younger"? Age is only detectable by things changing, like a person becoming wrinkly as they age. I don't think age is an absolute trait. Couple that with the fact that it doesn't go back in time, and you have... absolutely nothing happening.

[CreeperCommando]

Also, on the subject of neutrinos traveling faster than light: I've heard that that would allow us to send messages into the past. How exactly does that work? I'm by no means saying I believe the neutrinos actually traveled faster than light, but I can't seem to wrap my head around how it would affect time if it happened.

I think the thought of time travel is somewhat linked to time dilation effects. The faster a particle the less time effects it "experiences" in relation to its surroundings. According to the equations time comes to a standstill when reaching light speed. So going further in that line of thought , faster than light travel would make the particle go backwards in time.
This does however only affect the travelling particle (or so I believe), so the particle would get "younger" but not travel back in time.

Pretty much what you said if I may change some wording.
The observer to whom this particle speed is related to will claim that the 'time experienced' by the particle is at a slower pace than his own, and the particle will claim that the observers time is at a slower pace. Everything is relative.
Imagine both observer and particle are showing of their newly bought rolexes when passing by, both will claim the other ones is a fake/broken as it ticks slower.
How much slower is defined by their relative speed as this will approach to 'frozen time' when reaching speed of light(c), or reverse in time if passed c.

Although this 'slowing in time' has only a real meaning if one or the other does the acceleration and then to that person (see solution of twin paradox) and during no accelerating enviroments the particle would equally claim that it's us who are 'getting younger' as much as we claim it is.

I learnt once at this course about theory of sp. rel. that due to relativity of simultaneity, the more time dependent concept of something simultaneous would switch into a spatial dependent simultaneity leading to concepts such as a particle existing along a (maybe infinite) line in space at the same time! (compared to exist along a line in time). Search Tachyons for further read
PS. relativity of simultaneity is as important as time dilation and length contraction.

Another problem is broken causality as this would allow 'reasons to happen after effects', aka 'time paradoxes'.

Not to forget, E=Mc^2 say's that energy has mass, and this makes particles harder to accelerate the higher speed they have and F=Ma thus says that you'd need more force for same acceleration => the mass of neutrinos should by theory approach infinity as their speed approach c

That's why my claim above was that it's much more likely they forgot ther. of gen. rel. in their calculations as partly this theory ALLOWS speeds above c, and that although situation may not be in a strong field of gravity/acceleration EDITED AWAY, the speeds of the neutrinos in the experiment was extreme.
Much more simpler by occham's razor (used on the whole news situation) IMO than to claim a theory, heavily tested for over a hundred years, is suddenly faulted AT ITS DEFINITION. It's one thing if a prediction is a bit faulty, whole another story if one of the principles were broken to begin with...

EDIT: forgot that neutrinos hardly interacts with anything... may have some effects of my points, although main problem I deleted (I blame lack of sleep)...

[areuthere6]

before commenting on the inaccuracies of cerns measurements, it is better to read the paper itself (http://arxiv.org/abs/1109.4897). when going into the kind of detail they have there (you can even see the effects of continental drift on the length of the system), its very very unlikely that they made a simple calculation error regarding these results. they've been working on it since 2009 after all. However, that is not to say that they are right about ftl travel. as you said before, having light as the ultimate speed limit has yielded a HUGE number of correct predictions. to take an example from Arthur Beisers 'Concepts of Modern Physics': "A person switches on a flashlight in a spacecraft assumed to be moving relative to the earth faster than light. [within] the spacecraft frame, the light goes to the front of the spacecraft. [however] in earth frame, the light goes to the back of the spacecraft" which would result in the two observers seeing different events and violating any concepts of relativity. if you want to look into ftl travel, a better place to start than with neutrinos would be with tachyons or with cherenkov radiation. fascinating topics, which are fully explained, as opposed to the results from cern.

also, on the topic of string theory, I find that since there is no real way of testing the hypothesis, it has very little relevance. if you cant apply scientific principle, then it doesn't matter how pretty the maths is, its just philosophy. I'm much prefer looking into the quantum world overall

[CreeperCommando]

I didn't exactly mean to claim any inaccuracies in their observations, I'm doing my bachelors in physics right now and I know how insane accuracy this kind of equipment have!
I'm just claiming that the gen. theory of relativity (which in normal circumstances isn't needed in this kind of experiment) kinda has a fail-safe for allowing particles travelling faster than light and I also made claims reasons it would be understandable that the related group of scientists could have overlooked this part, there is a reason that humans tend to specialize inside their main career-choice.
In summary I'd be interested if someone presented results specifically modelled after gen.th.rel.

Always when something like this happens it seems nobody cares about gen. theory of relativity.
Although it could be a misunderstanding on my part in case of these scientists may know reasons of results, but the press doesn't and thus put words in their mouth.
I know I need to know more this event, but there is a bit of reluctance to have to listen to their whole seminar, would be nice if available in paperback :).
In the end it's not really the first time someone says 'Einstein theory finally put to rest?' in their article.
Once I heard from a teacher/prof. in theory of relativity how he and his colleagues got regularly letters from all over Europe claiming that they've disproved relativity by pen and paper. It gets to me when the first thing people think is that this theory is still twigs and leaves...

TL;DR:
I've never claimed any inaccuracies on their part. I'm just saying that they may have reached the limits of the modelling that's usually standard to particle physicists.

PS. good link areuthere6

[areuthere6]

There will always be inaccuracies (uncertainty principle and all), but the main reasoning my point to others was that the precision is certainly accurate enough for the calculations they are working on. just wanted to clarify on that. your statement on accounting for general relativity, however, may be quite close to the mark. the trouble there is that unless I am very much mistaken, finding a way of combining 'the theory of the very big' with 'the theory of the very small' is inherently difficult and the subject of most theoretical physicists studies at present. however, if special relativity does in fact turn out to be false, this could well explain why the theories wont combine easily.

also, as a matter of interest, what are you specialising in?

[CreeperCommando]

Well, the uncertainty principle actually claims that there are paired sets of values which never can be determined accurately at the same time, so you could theoretically get arbitrarily good accuracies only that you have to sacrifice something else.
What you say about gen. theory of rel. being not combinable with quantum field theory has lot to do in the fact that the curvature in space time gets wonky (like places endermens have rave-parties) when quantum effects gets dominant. I can't say to much about this as it's close to the limit of my knowledge there.
I'm hopefully assuming that without to great of a problem this case could perhaps be a bit lenient considering combining these two theories as it is a simple case to model around, or string theorists will likely start try to take over as this problems are exactly why string theory was founded in the first place :)

Would you believe me if I said working with theoretical physics has always been my childhood dream?

[areuthere6]

That sounds similar to what I've heard about the relationship between the two. gravity is, after all, the odd force out, and since technically the Planck length is dependant upon the gravitational constant ( = SQRT((hbar*G)/c^3), it would certainly lead to the eventuality you suggest.

string theory as a concept works very nicely. from the evidence i have gathered, it seems to have a very sound mathematical footing; the trouble is within the proof. there is no way to prove that these strings exist (although they said that about the neutrino, so its still a possibility for the future), and until there is more evidence, it would be foolish to use its concepts.

and yes; its a similar thing for me. you just appear to be a few rungs higher at the minute, though I will be starting at university this year. theoretical physics is the aim, but I don't want to lose sight of the experimental side too.

[Gilberreke]

the trouble is within the proof. there is no way to prove that these strings exist (although they said that about the neutrino, so its still a possibility for the future)

It doesn't actually need proof, just predictions. If the math for string theory can predict the neutrino measurements as being a result of relativity on a quantum scale, then it would immediately become a much more credible theory.

I'm also quite sure that this is exactly what is going to happen if the measurements turn out to be significant over time, they're going to be plugged into all sorts of mathematical models to see if any theory can be found to support the errors.

[areuthere6]

It doesn't actually need proof, just predictions

Predictions give the theory credibility, and allow it to be used as an accurate model, but without any physical proof it cannot serve in creating 'a theory of everything' ... if it is going to be taken as an integral part of physics, you cannot claim that it is true because it makes sense. if it crumbles, potentially years of research could be wasted.

[Gilberreke]

Predictions give the theory credibility, and allow it to be used as an accurate model, but without any physical proof it cannot serve in creating 'a theory of everything' ... if it is going to be taken as an integral part of physics, you cannot claim that it is true because it makes sense. if it crumbles, potentially years of research could be wasted.

So in your eyes Newton never had any serious theories, since they couldn't be proven and ultimately were even disproved?

Any theory with reliable predictions is an integral part of physics

[areuthere6]

wording, wording ...

What I was trying to say was that if we see physics as a route to creating a 'theory of everything', unless we have solid proof of certain concepts, we can only use those concepts as models. they are still important to physics, and useful in furthering of the study, but should not massively affect the final result if, as it has been shown in newtons case, they are inaccurate.

maybe that sounds a bit better.

[Gilberreke]

maybe that sounds a bit better.

Sure, but now you're just roundabout agreeing with me :)