Slashdot Mirror
Dark Energy May Lurk In Hidden Dimensions
Magdalene writes in to let us know about a sketch of an idea, that might one day become a theory, to explain the dark energy that is making the universe flee faster and faster apart. It posits that dark energy may be the result of a new kind of neutrino wandering in tiny extra dimensions above our familiar three. She adds, "There is no word yet on whether Sphere or Square are available for comment." From the article: "The mysterious cosmic presence called dark energy, which is accelerating the expansion of the universe, might be lurking in hidden dimensions of space. This idea would explain how the dimensions of space remain stable — one of the biggest problems for the unified scheme of physics called 'string theory'... To get the same amount of acceleration seen by astronomers, Greene and Levin calculate that the extra dimensions should have a scale of about 0.01 millimeter."
First of all, it seems to me that...wait, is that a NewScientist link?
Sorry, nevermind.
According to the calculations, however, these vibrations should either possess a ridiculously high energy density - 122 orders of magnitude larger than are observed - or cancel out to exactly zero.
What's 122 orders of magnitude between friends?
The link works fine.
OK, this story was "edited" by kdawson, but I don't see the standard anti-Microsoft crap, and it wasn't submitted by Roland. kdawson must be getting tired.
"Greene and Levin calculate that the extra dimensions should have a scale of about 0.01 millimeter."
Well, of course it should. How else would you expect to get the acceleration?
Brian Greene is such a media whore. He doesn't even have enough of an idea to get it published, but gets a New Scientist article.
Tell me you didn't get the title from a *@#%! movie poster ;-)
Table-ized A.I.
So this explains Land of the Giants
If you want news from today, you have to come back tomorrow.
In case you haven't read it, Flatland (The first non-wiki link in google) is the tale of a square named (conveniently) A. Square living in his comfortable home in a two dimensional world, who is eventually visited by a sphere from a *third* dimension and is both vexed and eventually exhilarated (and then vexed again) by what he learns in terms of geometric and social implications.
It's a wonderful bit of British satire and more written by Edwin A. Abbott around 1884. Check it out - it's a wonderful short story, and a very nice example of the treasures that lie within the public domain.
Ryan Fenton
It's not dead, it's just in another dimension.
Task Mangler
Greene and Levin calculate that the extra dimensions should have a scale of about 0.01 millimeter.
0.01 millimeter? Holy shit, if you step on a bug, you may be unwittingly killing an entire company just like Microsoft or SCO. I weepeth with remorse.
Table-ized A.I.
It's not dead, it's just in another dimension.
So our dearly-departed Fluffy is contributing the excelleration of the universe expension? Its gonna be hard to explain that one to my child.
Table-ized A.I.
There is nothing worse than a scientist who fixes the observation to meet their theory, to paraphrase the illustrious but equally fictional Sherlock Holmes.
It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
If Adelberger's pendulum does start to see gravity grow below 0.01 millimetre, it could be a sign that Greene and Levin are right, and the force that's tearing our universe apart really is an invader from another dimension.
I've seen Bush called a lot of things, but this takes the cake
That's it. It solved my problem. My ZPM is online. That solved the last problem before it got it online. Anyone have a space ship I can borrow, I want to build a larger version, but I need to test it in a vacant solar system.
Fight Spammers!
Please join me in tagging this article "LSD".
09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0
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That was a good Star Trek episode.
My guess it probably went something like this:
http://www.theonion.com/content/node/29433
Hopefully I didn't put any [] around my words.
...Midi-chlorians.
Next article, please!
(WIAK's Law: The longer a Star Wars discussion goes on, especially on Slashdot, the greater the likelyhood that someone mentions either Han shooting first or George Lucas raping their childhood.)
"Accept that some days you are the pigeon, and some days you are the statue." - David Brent, Wernham Hogg
Can someone explain or point to a resource on how a dimension has scale? I've heard this before relative to String Theory...where additional dimensions are possibly very small. I just don't get how a dimension has a size/scale. If I go from 2 dimensions to 3 the added dimension is orthogonal to the first two. The axes of the new dimension (as with the first 2) go to infinities in either direction creating a volume that is unbounded. That is, with two dimensions I have an unbounded plane. If I add a third dimension and I get an unbounded volume.
...and that bugs me.
So, in terms of my trying to conceptualize the idea of a dimension having scale, I take a two dimensional plane and add a third dimension and consider how this new dimension could have scale. I don't see how scale fits. I can't come up with a model that lets me conceptualize a notion of the added dimension itself being "smaller" than the other two...I see it as continuing to extend off to its respective infinities. All I can see is that the added dimension is orthogonal to the existing dimensions.
The only thing I can think of is the possibility that the new dimension's units (scale) are compressed relative to the other two. That is, I could have an object that is 2 meters long if placed on the x-axis and 2 meters long if placed on the y-axis but would only be 2cm long if placed along the z-axis (the axis of the third dimension). The third dimension would compress lengths relative to the other two dimensions.
I'd really like to know how to properly conceptualize or model the notion of a dimension having scale. I read about dimensions having scale often and just end up accepting it without understanding what it really means
If you can't get your theory to fit the facts, then you look for the facts that fit your theory?
http://xkcd.com/386/
It's the Great Old Ones in their extradimensional prison; they are trying to push out and warping the universe in the process.
Seriously: without some experimental evidence to back up these theories, they aren't worth the paper they are written on.
Dark Energy May Lurk In Hidden Dimensions
So.. let me get that straight. We solve the problem of energy we can't detect and dimensions we can't prove exist? Simple! We tuck the one into the other and thus explain everything in a single shot. Brilliant!
Now allow me walk away for today as I am laughing my guts out.
Everything I needed to know about life, I learnt from Blake's Seven
Unfortunately there is often just enough truth in some crackpot ideas to keep people pursuing them. We do have biological cycles which are influenced by the Moon (astrology), there probably are some numerological bits of weirdness in the Bible -it would be amazing if there weren't given the range of authors and their interests - and Freud had some genuine insights. It's this that can help to draw in intelligent and curious people.
Pining for the fjords
Maybe you didn't understand. Newscientist spams slashdot with every single one of their articles every single day, and nothing on there is EVER really new or interesting (view the firehose if you don't believe me). So the link works, but why would you ever want to click it?
So, how many metres long is a unit of time?
You guys maybe a bit too skeptical about Dr. Greene's latest foray into elegant dimensions. All this has already been predicted by Einstein's equations written in smiley formalism. But the equations are still for a static telnet universe. I would appreciate if anyone could transorm the smiley terms to animated smilies in whatever dimensions.
Every time physicist are trapped in a corner, they escape by inventing a new dimension
I tend to think that dark* (matter/energy) is a shaky fix for theories that don't work. What makes more sense: theory of gravity is wrong, or there's non directly observable matter? Same for dark energy...
Wow! It sounds like the Dark Matter guys and String Theory guys should get together. Soon we will have theories for everything and with no experimental validation required. I am going to try this excuse on my Quantum Physics Professor, "The reason I didn't turn in my last lab report is that it wandered into an alternate dimension." LOL! See my previous posts for what really happens in the future.
We don't actually need 2-dimensional euclidean space to describe the topological structure of the circle.
There are several different concepts of dimension in mathematics. The one you are probably thinking of is the dimension of a vector space. What we seem to need here is the dimension of a manifold. Intuitively, a n-dimensional manifold is something that locally "looks like" our familiar n-dimensional euclidean space (R^n). You already got that right with the ant example.
Manifolds can be described in different ways. One way is as a certain kind of subset of some higher-dimensional vector space R^m, this is the way you are probably imagining. But it is also possible to describe a manifold without any reference to a surrounding space.
For this we need the concept of a topological space. Informally, a topological space is a set in which we can talk about connectedness, continuity and which sets of points are "a neighborhood" of a given point.
As a topological space, the circle can be seen as the usual interval [0,1] (of real numbers), but with the points 0 and 1 identified (that is, they are considered to be the same point) (usually one would use the analogy "0 and 1 glued together", but this would evoke the intuition of a surrounding space again, which we are trying to avoid
Likewise, topologically a sphere is equivalent to a square (or a disk) with the whole boundary[1] considered to be a single point. A torus is a square with every point on the left edge identified with the corresponding point on the right edge, and every point on the top edge identified with the corresponding point on the bottom edge.
Generally, a n-dimensional topological manifold is defined as a topological space with the following property (+ some technical conditions):
For every point on the manifold, you can find a small region U around the point (a "neighborhood"), such that U is topologically the same ("homeomorphic") as a disk/ball or a box[2] in n-dimensional euclidean space. A homeomorphism is essentially a map f which puts the points of one space into one-to-one-correspondence with the points of another space, and respects convergence in the sense that some sequence[3] x_n converges to x if and only if f(x_n) converges to f(x). It can't tear regions apart which are connected, or vice versa.
For example, if we have some point of the sphere, we can take a small neighborhood U of it and map U to a disk in the obvious way. This mapping respects convergence. Thus, the sphere is a 2-dimensional topological manifold.
Now I only described the topological structure; topology is "qualitative" and doesn't talk about concrete distances, angles etc.. If you want to have these, you need a structure called a Riemannian manifold. But I haven't taken a course on differential geometry yet, so I won't talk about that
I hope I didn't tell you things you already know and that I didn't sound condescending. You are asking good questions and I think you would like topology courses
Whether the surrounding spaces are "real" is a matter of philosophy, but as you can see they are not absolutely necessary...
[1]: For the topologists: I'm using "boundary" in the informal sense here; of course the boundary (in the formal sense) of the whole space is always empty.
[2]: Actually it doesn't matter whether you require it to be homeomorphic to a ball in R^n or to the whole R^n.
[3]: In general it's a net, not a sequence
Impending doom for the crew? All out of ideas? Engaging story lines dried up years ago?
Make up a new particle!
I tried topology once, but I couldn't wrap my head around it.
When our name is on the back of your car, we're behind you all the way!
Having absolutely no background in science I have no weight one way or the other on these issues. I just wanted to mention that it seems utterly ridiculous that every time something doesn't fit into the model of physics someone's trying to push, they try to "invent" something completely new to save their theory. IE: dark matter, dark energy, string theory, etc. I think that's why we've seen theories like MOND become more popular. It's simple and seems to work. When string theory fail, people add more strings! Of course, simple does not mean it's scientifically accurate and for all we know, string theory may be the "true theory". My point is we need to stop pushing stories that aggrandize theories until some serious research has been done on the issue.
Facts we know :
- "Something" is accelerating the expansion of the universe.
- The universe is black (ie. the non-presence of light).
From these two observations I can come deduce the following : The universe has the "form" of a hypersaddle or a "parachute" where the extremities are falling together in a black hole. This/These mother-of-black-holes (insert goatse-joke) tear at the universe with their immense gravity, making the universe (from our point of view) expand at an accelerating rate. Thus the universe is expanding but towards the same "place" at an accelerated rate, and since all of the universe ends in a black hole the universe is black since light can't escape its gravity.
There you go, now get off my lawn with your fancy "Dark energy", in this house we follow the law of gravity!
one is born every minute.
Blasting physicists (or any scientist) for speculating on unsolved, scientific mysteries is just an astounding step backwards intellectually and I'm afraid that as a society we've taken that huge leap backwards.
If the mob stopped spouting their own specious dogma, showing their own Newtonian-based cognitive dissonance and actually RTFA:
That folks, is science in action. Don't make me go through the checks and balances between experiment and theory.
It stops being science when critical thinking and the scientific process are overruled by non-scientific reasons.
The corollary is that it stops being scientific criticism when the basis of the contrary views also fall prey to non-scientific reasonings. Reasonings such as "I don't see any _______" - fill in the blank with "atoms", "neutrinos", "monkeys giving birth to human babies" - all of which were used as arguments against theories about things we did not yet know and were considered unprovable at the time.
Well, I for one DO NOT welcome the creationist tagging overlords.
I wish *someone* would mod you up, because it's one of about 2 or 3 posts in this whole discussion that is actually insightful.
Loops and Strings 2007 with discussion of Witten's amazing new paper on on 3D Gravity.
MoonshineMath blog
October 10, 1995
This Week's Finds in Mathematical Physics (Week 66)
John Baez introduction to the Monster Group.
Background on Conformal Field Theory (needed to follow Witten's paper:
Wikipedia pretty good intro.
-- Prof. Jonathan Vos Post
This ties in neatly with Phillip Pullmans's "His Dark Materials" trilogy. In the first book, we learn that there are many parallel universes. In the second book we begin to discover that Dark Matter is collected to the rise of intelligence, and find a knife so sharp that it can cut between dimensions.
Kinda neat that science is mirroring fiction.
www.lucernesys.comHorizon: Calendar-based personal finance
"Why is your code so slow?" - "Uh... Dark Cycles."
"Why is the project late?" - "Dark Time."
"What happened to all the donuts in the break room?" - "Um, sucked into a hidden dimension?"
sic transit gloria mundi
the Dark Force has finally determined to rip our world apart?
I've been waiting for this in terror since 1977.
Han raped my childhood first, you insensitive clod!
Consider Natalie Portman, Soviet Russia, and our new overlords included by reference.
dragonhawk@iname.microsoft.com
I do not like Microsoft. Remove them from my email address.
That word you keep using. I do not think it means what you think it means. ;-)
dragonhawk@iname.microsoft.com
I do not like Microsoft. Remove them from my email address.
For a neutrino emmision. Those only come from stable wormholes, its a proven fact.
Did someone say cake?
You are likely to be eaten by a Grue.
Perhaps it is the void that pushes matter to clump together...if such was the case, then the acceleration of the universe would be explained by the same force that makes gravity: the pressure of the void onto matter.
Something that's often omitted in writeups of these 'dark energy' claims, is that a non-zero cosmological constant would also explain the observations, without the need to invoke 'dark energy'. However that isn't in fashion in the mainstream at the moment.
My theory is "The Big Shrink". Basically, space is NOT expanding, simply the matter in it is all shrinking. As everything shrinks, so do our methods of measurement so space appears to be expanding.
Here is a thought experiment to help with understanding what I am trying to say:
Imagine 2 circles both with a diameter of 10cm and with their centre points exactly 20cm from each other. So the space between them (circumfrence to circumfrence) is 10cm.
Now if the circles were to maintain their center point location but shrink in size to have a 5cm diameter, the distance between them (circumfrence to circumfrence) is 15cm. Since we have halved our diameter, everything else should have halved, so our ruler should now be half it's original size. This means with our newly sized ruler, our distance between the circles will now appear to be 30cm and not 15cm. (Note for an unaffected outside observer, the distance would remain at 15cm but since we are not and cannot be outside observers anymore than we can be outside observers of time it is irrelevent)
The further apart the 2 circles, the greater the change appears. eg. if the whole thing is scaled up 10x, the distance between the 2 objects (circumfrence to circumfrence) would go from 100cm to 300cm ie. 200cm apparent movement as opposed to 20cm apparent movement. This accounts for everything appearing to move away from us at increasing speeds according to their distance.
This theory of mine would have to be universal and apply to all matter. It makes more sense to me that the universe started as a single balll of energy and that energy has receded or shrunk. Conservation of energy is preserved within the system but not from an exterior perspective.
As interested as I am to learn about how Bush lied about the extra dimensions to hide the oil he's stealing from Iraq, I have to insist that the fact that String Theorists have actually performed an experiment (!) does not make their theory "scientific". If I have a theory that green aliens are living on the surface of my desk, and a perform a visual scan and don't see any, then I have similarly experimentally ruled out the possibility that these aliens are larger than 0.01 millimeters or so. The fact that I did an experiment doesn't somehow validify my original theory.
I personally have nothing against intuitive intellectual pursuits. But those who claim to adhere to the religion of empiricism, and then embrace an intuitive theory such as String Theory or its offspring, are hypocrites.
http://arxiv.org/abs/0707.1062
I for one, welcome our new cheese-eating Python overlords!
and let us hope we find their tiny dimension accommodating to us.
.
- aqk
F U
Has anyone considered that dark energy may be the emissions created by Black-Holes swallowing up everything. Whilst nothing including light escapes, perhaps Dark Energy doesn't obey the same rules as the emission is becomes anti-gravity - heavy gravity repelling heavy anti-gravity?
- is that physicists just take the established theories for granted without actually questioning them, and mostly without understanding them either. In fact, one can say that quantum mechanics (or rather, the 'Copenhagen Interpretation') in particular is almost hostile to critical examination of its basic assumptions. Of course, I'm not saying that quantum physics is wrong in its entirety, just that I think we have reached the limits of its validity a while ago and that a new approach is needed.
All these strangely unintuitive theories about strings, rolled up dimensions and fundamental forces that are weirdly ungeometric (like eg. the strong interaction) are IMO an artifact of the viewpoint, just like the constance of the speed of light. As far as I can see (without being able to quite write it down as a well reasoned theory) the way forward has to involve finding a clear explanation of some of these things that we just assume as fundamental, like the speed of light and the charge of the electron - as well as explaining things like electricity and defining what a particle is.
Perhaps a better starting point is actually general relativity, after all? Einstein made several attempts at defining particles in terms of his theory, but never quite made it; he also tried to unify electricity and gravity. I have reason to think that if we solved these two problems, the others might turn out to be derived from first principles in the resulting model.
Quoting, I believe, Carl Sagan "The absence of evidence is not evidence of absence"
The "extra dimensions" have already been explained to be stable. They were unstable at the beginning of the universe (when they were much, much larger), and have since (a matter of picoseconds after the big bang) shelled off and become much smaller. The "extra dimensions" are actually far far smaller than .01 millimeters, more along the lines of a fraction of the size of a helium nucleus.