Slashdot Mirror
Gravity Diluted By Multiple Dimensions?
SEWilco writes: "Why is gravity so weak? Maybe it isn't, but it's diluted by propagating through many dimensions. The theory provides a relatively simple explanation to several oddities of physics, and it should be relatively easy to test. Notice the links at the bottom of the story; one of them mentions that the concept doesn't have a catchy name yet...and we'll be reading more about it soon. Slashdot discussed extra dimensions before, but this concept involves gravity actually propagating into them." I think we should call it 'The Emmett Effect.' There's got to be some lab-coated brainiac out there than can make it happen.
I mean how the hell can you compare two forces with completely causes? It is just as absurd as saying that 1 gram is more than 1 coulomb.
That's right. They're comparing the values of the coupling constants, which are dimensionless quantities (ie. no units), so they can look at things on the same scale. The coupling constant determines the strength of the interaction. (It also has a really bad name; it turns out that it's not constant.)
- W. Blaine Dowler
http://www.bureau42.com
Dimensions do not have a size. Objects have sizes in a set of dimensions.
Of course dimension have a size, due to the fact that they are either limited in some extent or infinite. For instance time has a definite starting point and may be infinite in size (an open universe) or finite in size (a closed universe with a Big Crunch). Since the Universe isn't infinitely large the three spatial dimensions we're familiar with also have a size.
In superstring theory the compactified dimensions have a size corresponding to the Planck length in usual models - approx 10^-33 metres. There are models in which the size of these dimensions could be much larger, as in the article, and in those the idea in the article could be made to mesh with superstring theory.
Sure, having some arbitrary dimensions and fundamental particles entangled in them does seem far fetched. But remember, these are just models. There probably aren't little teensy rings of dimensions upon which some force particles are "caught". It's something so our poor 3-dimensional biased minds can understand reality. Perhaps you're right, and "dimensions" are actually a continuum, instead of cut and dried orthogonal measurements. But I think the human mind needs some model it can innately understand.
It's 10 PM. Do you know if you're un-American?
In large part, the difference in the examples you give is not so much gravity, but other issues. For the insect, their fall is governed primarily by aerodynamic drag - in a vacuum it will plummet directly to the ground, same as the horse. In all cases, the amount of damage sustained is controlled primarily by the 'square-cube' law - the strength of the body's structural components goes up as the square of the size, but the mass goes up as the cube of the size. This means the strength to weight ratio gets worse the larger you get, so the larger, hence heavier objects will suffer worse damage.
...phil
...phil
"For a list of the ways which technology has failed to improve our quality of life, press 3."
Dimensions do not have a size. Objects have sizes in a set of dimensions.
Saying a dimension has a "size" is an unfortunate wording born in an attempt to reach a broader audience. Dimensions have scales. I'm a little fuzzy on this part, since I'm in particle physics and not cosmology, but the idea is that the other dimensions could be "curved in" on themselves in such a way that their existance would be masked from our perceptions. I have yet to find a decent layperson's explanation for this, but I'll keep looking. The mathematical gymnastics in the theory do lead to characteristic length scales.
- W. Blaine Dowler
http://www.bureau42.com
The formula for calculating the gravity between two objects from Newton is:
Fg = G * m1 * m2 / d^2
Fg - is the force
G - is a constant that is very small (about 10^-11)
m1 and m2 - are two masses of objects attracting
d - is the distance between objects
Gravity acts between every two objects in space. Even between you and me. But because G and our "weight" is so small, we can't notice the gravity. It is very weak force.
But when gravity acts between the Earth and you, the Earth's mass is very very big and the gravity is noticable. If the gravity would be a strong force, then you'd probably change into a pancake.
We rearrange this equation:
Fg=(G*m1/d^2)*m2
(G*m1/d^2) = g ~ 10 m/s
So we get the good old (and very simplified) equation:
Fg= g * m
But the word weak is very relative. You must compare gravity with the other forces. And relatively it is very weak.
Gravity is related to mass, and electromagnetic forces on charge. How can someone compare the mass of the earth with the charge in the atoms in a magnet? They are totally different things
Not quite: you can compare the gravitational force of an electron or proton to the electric force effecting it. If you compare the repulsive force between two electrons to the gravitational force between them, you'll get around 10^40 ratio.
The notion sounds deceptively simple: besides the familiar three dimensions of space there may be other dimensions, too small to see yet perhaps as large as a millimeter.
Dimensions do not have a size. Objects have sizes in a set of dimensions.
It is true by your perception of a dimention it doesn't have size, since you're used to think about infinite dimentions. However, imagine a dimention is wrapped around another dimention, and thus creates a loop - this loop have a limited size - after one milimeter of movement along this dimention you return to your initial point. So this is how dimentions may have size.
Sela
> So while gravity allows us to detect the presence of other universes, they do not merge with ours because no strong, weak or electromagnetic interactions can occur across universal boundaries.
What would happen if a super-massive object in the other universe passed "near" the earth? Could the gravitational leakage cause us any problems? Could we get sucked into a black hole in the center of a galaxy a gazillion light-years away?
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Sheesh, evil *and* a jerk. -- Jade
Oh come on !
Semi mystical garbage ?
Listen to yourself ? Ever heard of the Einstein/Rosen Bridge efect ? The theory of parallel universes, based on the concept of multiple dimensions was an Einstein theory !
I really get ticked of when people try to hide their ignorance behind other peoples genius. Are you aware that Einstein divided by zero in the orriginall theory of relativity, something that was only discovered 30 years later by a 2nd year physics student (sorry, can't remember his name) Einstein acknowledged throughout his life that he is not infallible, and expansions upon his theories had always done him proud. What makes it sacrosanct now ?
Here is a litle something else for you, in 1891 Jules Verne (One of the Godfathers of SCI-FI) wrote a story called Paris, which his publisher rejected because "it was too unbelievable"
He described Paris in the 20th century as a city where everbody has electric lighting (back then the lightbulb had yet to be invented) and cars (which was a brand new invention). The manuscript made headlines a few years ago when someone decided to publish this, pitty Verne could not live to see it. Get the point ?
Science Fiction has a lot of Science in it. And has been the inspiration for many inventions (more recently voice-recognition software, which in the 80's was considdered completely impossible)
And frankly this theory tends to make sense, even to someone who doesn't understand the maths behind it. Yeah, I admit where my knowledge falls short - try it sometime.
PS. I would like to propose the name "Chrighton Efect" I'm sure Michael will be writing a story about this soon, and thereafter make a sucky movie version.
"Semper in excretum set alta variant"
Don't mention it. :) I'm a physics student now, but I plan to work in Academia. I enjoy teaching (informally, and as a lab TA), so I take every chance I get to practice for the times when it's my job to make sure someone understands something.
Besides, I don't see the point in flaming someone because they took different classes than I did in high School and University. What's the point? If you're asking questions now, you're trying to learn. Why should I discourage that?
- W. Blaine Dowler
http://www.bureau42.com
...the Slashdot Effect, already known to dissipate the strength of powerful servers.
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What? WHAT?!! Oh.
LOL! I always figured humanity's last word would be something like, "Oops."
"There is no shot you can take that I cannot simply deny." - Ertai, wizard goalie
Could someone give me some background on what precisely makes gravity weak? I never thought of it as anything but normal before. :)
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NeoMail - Webmail that doesn't suck... as much.
Unfortunately, at this point all 7 other dimensions are filled with unpaired socks, lost keys, and pocket change.
Mr. Ska
That's true. I've heard of cases where test audiences in 1970's sci-fi movies thought something was wrong with the print because there was no sound in space. Hollywood chose to run with the most common misconceptions rather than correct them, and now they propogate them. "Sound in space" is the most forgivable error. Nothing like the old Star Trek "he won't remember what happened when we beam him back to the past because it wouldn't have happened yet" cop-out. The sad thing is, Lois & Clark ripped that off thirty years later, in the episode where H. G. Wells built a time machine and came to visit.
- W. Blaine Dowler
http://www.bureau42.com
Although the prospect of such a exciting new approach to gravity and the dark (or rather 'transparent' since it does not absorp light) matter problem, it needs to be stressed that lack of theories and ideas is not the problem.
The actual limit on progress in this field is lack of relevant data, obtained either from super colliders or from deep cosmological observations. Currently it is possible to make many models consistent with the observational constraints because it is these constraints themself which are so loose.
Everybody knows the US killed the giant supercollider program, and the state of affairs in observational cosmology learns that it is very difficult to calibrate measurements of (dark) matter.
To so something more about the last point, since I've researched this last year, it is far from trivial to yield reliably answers on galactic cluster potentials via dynamic or gravitational lens measurements, especially because you need to go into the Infrared to observe (optical) light emitted by stars in the deep universe. Only recently with instruments like ISAAC on one of the VLT telescopes we are able to obtain high quality near-infrared data. For the far infrared imaging space based missions like the NGST are required, because of the polluting thermal radiation from the earths atmosphere. The NGST is still under study and not expected to be launched until 2010!
Until then we can only speculate aboute the nature of dark matter.
Ivo
We are all in the gutter, but some of us are looking at the stars
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Gravity is related to mass, and electromagnetic forces on charge. How can someone compare the mass of the earth with the charge in the atoms in a magnet? They are totally different things.
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Exactly. A person could make the opposite argument - that you can place a rock on the ground and it will stay there, and yet remain stationary when you move a magnet over it.
Or even plop down a 2 ton chunk of solid iron. It's a lot easier to keep it on the ground than to lift it with a magnet.
- Jeff A. Campbell
- VelociNews (http://www.velocinews.com)
- Jeff
String theory requires 10 dimensions. It's been effectively replaced by membrane theory, which requires an 11th dimension. They weren't brought in to make the math easier, they were brought in to make it possible. String theory didn't quite pan out, but membrane theory is gaining strength.
Part of the string theory problem was that there were five totally separate formulations for the theory. Membrane theory allows all five to be related by "gauge transformations."
A gauge transformation is essentially a freedom within the math. When calculating the potential energy of an object, we need a reference height, generally the height of the lowest place it can go. This is totally optional; we can set "ground level" to be the ground, the ceiling, or the basement. As long as we use the same ground level in all calculations, anything that we can measure or observe will be correctly predicted by the theory.
- W. Blaine Dowler
http://www.bureau42.com
I have a simple question.
Suppose for a moment that, indeed, many universes inhabited this specific multiversee.
Also suppose that certain extreme events would lead to cross universal leakage.
We wouldn't need to wait for a particle accelerator to be built to witness such effects--those stellar furnaces known as stars should be a constant source of evidence for reactions so extreme that they violate the bounds of this 3D environment.
In fact, stellar reactions should be the most mysterious, because they'd contain the most missing energy by far. It's not unimaginable, to be sure. Where I think some things start to break down is that, if there *is* leakgage, the events that cause such things as Gamma Ray bursts would *need* to involve cross universal effects.
A bigger problem actually with cross universal gravity is that it would cause real problems for universal integrity. In order for multiple universes to to exist in parallel to eachother without any kind of "reinforced wall" between those universes, they must grow in parallel to one another and never blur together. But if gravitation in one universe can extend out towards another, there'd be no way for the parallel universes to remain separate--particularly if the forces equated at short distances, the universes would draw together into one.
Thoughts?
Yours Truly,
Dan Kaminsky
DoxPara Research
http://www.doxpara.com
"Little Caesars? You do pizza?"
There's a great collection of essays by a fellow by the name of Michael R. Feltz who describes the possibility that the three-dimensional universe we live in may be built upon a fourth spatial dimension which is expanding. This could also explain gravity if matter is "dragging behind" in this expanding fourth dimension.
Feltz's essays are located at http://www.cyburban.com/~mrf/. It's really worth checking out, as it gives you some great ways to visualize the fourth spatial dimension, and some interesting insight into the possibilities of the structure of our universe.
Sometimes the math gets a bit heavy, but the discussion is worth reading.
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That is the strong force, carried by the 'gluons', which have been around for quite some time now, cant exactly remember how long though.
:-)
Gluons have most certainly existed since the beginning of the universe. Sorry, I couldn't resist...
Normally, the photons are repelled from each other due to electromagnetism, since like charges repell. But at small distances (like you mentioned) the strong, attractive nuclear force between the particles overpowers the electromagnetic repulsion. So, if you slam two protons into each other at high energies, they tend to stick. In fact, they release energy in the process by losing the potential energy inherent in their separation (similar to a brick losing potential energy when it falls). That's a rough way of putting it but you get the idea.
The process I just described is two hydrogen ions (aka protons) fusing into one helium ion (2-proton nucleus), which releases the energy of nuclear fusion-- it takes a lot of energy to cause it but you get more energy out than what you put in. That's why if you use a fission bomb as the detonator for a hydrogen (fusion) bomb, it can release 100X the energy of the fission bomb by itself.
Hopefully that wasn't more background information than you needed...
Disclaimer: any inaccuracies in my description of the physics are due to me typing this in Windows2K.
-CausticPuppy "Of all the people I know, you're certainly one of them." -Somebody I don't know
Newton predicting weakening through dimensions? Yeah cool!
Well, as I said I not arguing against theory itself. I'm arguing against the fact that the article shows a clear distinction between three-four dimensions and two more. There is some sort of strange dessimetry in this story. Gravity weakens due to unseen dimensions. And the other three "feed up the boy"???? What the Hell is this? Physics? Einstein is jumping in his grave man. What tells you that one dimension "strenghts" and other "weakens"??? Third Law and similar stuff to the trashcan? And why it looks like that our dimensions strengthen gravity while the two poor "unseen" weaken it? White-necks, niggers, and red-skins in Physics? Too human for the Universe...
Well I like a lot of these theories of multi-dimensional worlds. But such idea of "dividing" dimensions the way it is shown in the article is rather ridiculous.
Jesus. I need to sleep or get laid as soon as possible. This computer shit is bad for your head.
What I'm wondering, is what this has to do with mice? I mean, since it is Science and it was posted on /., it HAS to have a mouse that was genetically engineered, right?
RIGHT?
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rJames.org - illustration
If this checks out, it could lead to a new era of physics research as productive as the first half of the 20th century. Too much of recent work in physics has revolved around explaining cosmology or developing theories that involve energy levels far beyond our reach. But this gravity theory leads to something that can be worked on. That's where new technology comes from.
Science is prediction, not explaination. - Fred Hoyle.
Leptons refer to the "light" particles. There are six leptons known of today, the electron, the muon, the tauon, the electron-neutrino, muon-neutrino, and tauon-neutrino.
Their are six flavors of quarks, the combination of them produces the mesons and hadrons. The mesons are particles like Kaons, they are the middle particles composed of two quarks. Protons and neutrons are examples of hadrons, or heavy particles composed of three quarks.
The 6 flavors of quarks are:
Up
Down
Charm
Strange
Bottom (originally called beauty)
Top (originally called truth)
Each of these quarks have their respective anti-quarks. The proton has the combination of Up Up Down, and the neutron has Up Down Down. Quarks are always found in groups of two or three, the search for a single quark is being conducted but many believe that it will never be found. The last quark to be found was the Top quark, and it was theorised many years before it was actually found. There is a lot of research still be conducted on Top quarks because they are so new to the playing field.
There are a couple other fundemental particles that no one has mentioned. Those are the force particles and the Higgs Boson Field particle.
Both quarks and leptons are considered fermions, which is the classification of any particle with spin 1/2, 3/2, 5/2... The fundemental force particles, the photon, Z, W, gluon, and, assuming it exists, the graviton are considered bosons, or those with integer spin. All of those, except the graviton have spin 1, while the graviton has spin 2. The Higgs Boson is the really wierd one, is theoretically has spin zero, and is the fudge factor for giving particles mass in the standard model (its existance also breaks the standard model because it would technically have infinite mass).
There are theories out there like Supersymmetry which believe that at high energies all fundemental particles and forces have a supersymmetric partner. This supersymmetric partner has +/- 1/2 spin off of the low energy particle/force, so a fermions supersymmetric partner is a boson, and a bosons partner is a fermion. If Supersymmetry is true then we will roughly double the number of elementary particles.
If you want to learn more about particle physics then go to the particle data group site.
Disclamer - Opinion of Person
I often used what's known as Cp, or the CausticPuppy constant, which is unitless.
It's not a universal constant, since its value changes from problem to problem, but it is a constant within the scope of any one problem.
Cp is the value by which you multiply your answer in order to equal the answer given in the back of the book (or the "expected result.")
It's best used if you bury it somewhere in the middle of the math, because hopefully the TA who's grading the papers won't follow too closely.
-CausticPuppy "Of all the people I know, you're certainly one of them." -Somebody I don't know
"Dark Matter" is of course the name given to some substance that has mass, but neither absorbs nor reflects light. According to many calculations, the visible universe should weigh much more than what we can account for with telescopes.
This theory stated that "Dark Matter" may be a manifestation of mass sitting outside of our three (four?)-dimensional universe, undetectable to all of our instrumentation. The idea is that the gravitron is the only subatomic particle that's capable of jumping through dimensions, and therefore makes its presence felt even though we can't find any mass to associate with it.
All this is way beyond me.
Wah!
We can laugh, but there are a lot of people who ask this question seriously every time physicists push the envelope a bit further. (Last time I checked we didn't collapse into a Bose-Einstein Condensate or become a strange(r) planet.)
For people who are worried about micro black holes, remember two compensating factors:
<ul>
<li>Hawking radiation should quickly evaporate it
<li>Even if it doesn't, this black hole would be so small that the earth would look as empty as interstellar space to it. It would quietly orbit within the earth and very, very, very, very rarely hit a proton (or quark?!) head-on.
</ul>
David Brin (astrophysicist by training) discussed this in _Earth_. I don't recall the mass of a black hole which could ultimately consume the earth, but it's a lot heavier than you would expect - equivalent to small mountains (or larger!)
For every complex problem there is an answer that is clear, simple, and wrong. -- H L Mencken
>Ehm, excuse me but doesn't the phrase "comparing apples to oranges" come to mind here? I mean how the hell can you compare two forces with completely causes? It is just as absurd as saying that 1 gram is more than 1 coulomb. Gravity is related to mass, and electromagnetic forces on charge. How can someone compare the mass of the earth with the charge in the atoms in a magnet? They are totally different things
Gravitation coupling constant = 2piKM^2/hc = 5.3*10^-38.
electromagnetic = e^2/2hc = alpha = 1/137
weak = G_F8piM^2c/h^3 = 1.02 * 10^-5 (even though weak and electro are the same thing)
strong = alpha_s =~ 1
Hence gravitation is extremely weak
Also, they are all charges, just difference kinds of charges, gravitation is carried by the graviton, and is the gravitational charge, strong is the colour charge, weak is the weak charge, and electro is the electric charge -- they are all analagous.
>Dimensions do not have a size. Objects have sizes in a set of dimensions.
Since I am only a 3rd year uni student, I cant comment much on on this, but I know the article is correct however.
Okay, I've got my asbestos on, so flame away.
Here's what I think is really going on. Gravity isn't us being pulled toward the earth, it's us being pushed towards it. Why do I think this? The Zero Point Energy field. It's everywhere. Einstein always said there was more than enough energy in the space occupied by a coffee cup to vaporize all of Earth's oceans. He wasn't talking about the strong nuclear force, you know, the one that makes the wonders of atomic weapons possible. No, he was talking about the energy inherent in space-time itself. It's everywhere -- not only in pure vacuum, through which it constantly streams unobstructed, but also both inside and outside every object, every atom, every *thing* that exists. It's what keeps the negatively-charged electrons orbiting an atom's nucleus instead of spiraling right down into it, attracted there by the positively-charged proton. Because it's everywhere, it exerts a force in every direction. This force extends outward without bound, its strength decreasing with distance. It also interacts with matter, which "blocks" it somewhat. And what happens when a force meets resistance? It tends to push that resistance in the same direction as its force vector; at the same time, some of its energy is consumed by the work it does (moving the matter it hit). But what happens when this force is pushing on an object from *every* direction at once? You might think it'd crush it. Nope. Remember; to be crushed, there would have to be a "pressure" or force differential between the object's inside and outside and, as explained previously, the force is equally pressing from both within and without the object. This is analogous to our own very observable situation on earth. We exist under a rather thick layer of atmosphere. Right now, there are millions, if not billions, of tons of force pressing down on your head from the weight of the air above you. Why aren't you crushed under all that weight? Because there's an equal force balancing it from the opposite side. (Just trust me on this one.) Same thing with the ZPE field.
So here we have this great big giant ball of matter we lovingly refer to as "Earth." It, being made of matter, presents resistance against the force of the ZPE field, and it dissipates some of that force before it gets all the way through the earth to the other side. Now, because all the energy coming from every side of the earth interacts with the earth's matter in the same way, with resistance, it doesn't push the earth in any one direction -- just like the air above your head doesn't push you right into the ground. But think now of something sitting ON the earth, something that can be considered part of its matter. Something like you, sitting there at your computer. You too have ZPE energy coming at you from all sides; up, down, inside, outside, left, right, etc. But because the earth, in interacting with it, is shielding some of that energy by absorption during its travel through the earth (some comes from beyond the other side of the earth from you, some comes from 12 feet under your chair, some comes from .001 millimeters under your butt sitting on the chair, etc, but all of it is absorbed in some way by passing through matter), there is NOT a net zero ZPE force acting upon you. There is in fact more of it pushing you down from the relatively unshielded "Up" direction than there is from the highly shielded "Down" direction; therefore, you are pushed down towards the center of the earth, and the force with which you are pushed is in direct correlation to your mass and the earth's mass. Does that sound familiar? :)
Now think of a black hole. Eerie, scary things. They are of course extremely dense collections of matter, where even the electrons can't orbit because it has been crushed so competely. In ordinary matter, there is LOTS of empty space; a neutrino could pass all the way from your forehead to the sole of your right foot without even touching any of the matter that makes you up. That's why only a very very small percentage of the ZPE energy interacts with you in a direction that isn't balanced from the other side (ie, through the earth) -- because there's very little there to interact WITH. But what about a black hole? Very very dense, trillions of trillions of trillions of trillions of trillions of tons of matter all smashed into a tiny ball -- there isn't ANY free space inside it; it's all matter. So what does that mean? Yep; ALL the ZPE energy gets absorbed by interacting with it, from every direction, and so the energy flowing from behind you, through you, and towards the black hole isn't balanced by anything pushing back FROM the black hole -- and you are completely crushed into it.
This is also why there is such a thing as the Gravitational Constant. It refers to the amount of interaction between the ZPE energy force and matter. It is very very small, and is multiplied by the mass of two objects to determine the amount of gravitational attraction between them (the GxM1xM2/d^2 formula). That number, "G", is literally how much of the energy in the ZPE field gets absorbed by passing through one kilogram of matter. Let's get into a bit of math here...
The gravitational force, in Newtons, between objects having masses of M1 and M2, in kilograms, and separated by a distance of d, in meters, is the product of the two masses divided by the square of the distance between them... multiplied by G, which is 6.673e-11 Newton-meters squared per kilogram squared (the odd units associated with G are there so they cancel out all the units in the formula other than the result, which is in Newtons). Two 1-kg objects separated by 1 meter would yield Gx1x1/1x1 Newtons, or 6.673e-11 Newtons. Not very much. This means that most of the ZPE energy passes through these objects unobstructed. But how much doesn't? Literally, "G" doesn't... thus, 0.000000006673% of the energy gets absorbed and translated into "motion" by pushing the matter in the direction in which it is imbalanced. I may have said it before, but it's worth repeating: Nature doesn't abhor a vacuum. Nature abhors imbalance. All things will seek balance. That's how you can siphon gas out of your gas tank, and that's why you get pushed to the earth.
Let's take a more realistic example: you and the earth. You have a mass of, let's say, 80 kg (176 pounds); the earth's mass is 5.974e24 kg (rather a lot of pounds). The distance from you to the earth isn't 0, as you might think; it's the distance from your center of mass to the earth's center of mass, which is roughly 3,185,500 meters. So plugging all that crap into the formula, we get 4.71e+13 * G, which makes 3,142.83 Newtons of force pushing you to the earth. G is the percentage of "gravitational" energy that gets absorbed or deflected by its interaction with the matter making up you and your body.
I haven't completely worked out ALL the math yet, but something tells me this is right. It answers all the unknown things about gravity, it explains momentum and inertia, it explains what keeps atoms from just collapsing into themselves... hell, it might even be the definition OF matter. So come on; let's see you armchair physicists blow some holes in my theory...
"The best weapon of a dictatorship is secrecy, but the best weapon of a democracy should be the weapon of openness."
I have been watching sci-fi shows and movies for a number of years about parallel dimensions, during that time you tend to develop your own theories about 4th dimensions.
From what I have gathered, for every choice we make there is an infinite amount of possibilities and from those possibilities an inifinite amount of alternate universes are created. Each universe is unique. And the theroy of a paradox, a loop error (example: I go back in time and kill my mother before I was born, I was never born, but then how could I have killed my mother...endless loop), is in fact only half true. If you make a change in the past you begin to exist in an alternate reality and you would continue on. (Reference in Back to the Universe: "...it would destroy the entire universe, however it would probably be limited to our own galaxy"....almost true; you'd never return to that universe (but it would continue on as normal without your existence.)
Now getting back to the gravity theory. If in fact gravity is a constant and you could effect changes in one universe and affect anothers, then it would make the above theory false. There would have to be a universe that would not be affected by the action of creating that change. It'd be as if you created a paradox in every other universe (affected some change that should not have happened because they did not do it).
I believe this gravity theory to be false
"Imagination is the only weapon in the war against reality." -Jules de Gautier
From a Newtonian perspective Gravity acts instantly. If the Earth needed to wait 8 minutes for the suns gravity to hold it in orbit we would spin off out of the galaxy. A physician named Laplace postulated this in 1825.
I would imagine that the best place to measure the propagation of gravity would be in an event such as a supernova. There are tremendous energy to mass conversions that would effect the gravity between the supernova and an observer on Earth. If Gravity propagates instantly you would get a different event observed on Earth than if gravity is limited by the speed of light and a "gravity wave" traveling at the speed of light is unable to overtake and slow down or blue shift the radiation traveling towards Earth from the supernova. When you ask what is the speed of gravity is from this perspective you are really asking how accurate is your stopwatch.
Physics according to Einstein uses the speed of light as a limit to gravity propagation non locally. The relativistic calculations work for many applications, but they are not very easy to use for doing things like calculating satellite orbits.
I guess it all depends on what you want to do with a calculation. When I go to a restaurant and need to calculate a tip it is easier for me to move the decimal point in my mind than try to do it out on paper. I have friends that make their children do it out longhand on paper for the practice.
Hyperspatially Orthogonal Transmission of Gravitational Rays In Twisted Space, or HOTGRITS for short...
Damn...I think I've just used up my day's supply of long words...
-- Bah weep grah nah weep nini bong
Definitely not right.
Never confuse equality of quantity with equality of property. Example: A dollar buys me two dollars. However, apples are not the same thing as dollars. Apples are tender, dollars are legal tender. Apples are round, dollars are rectangular and flat.
Conversion may occur under some limited conditions, as well.
For example, I may not transform an electron directly into energy. You gasp! No, I'm not kidding. I have to have an electron and a positron to do that. Nor can I convert a photon into just an electron.
Saying that "mass=energy" and "charge=energy" ignores all kinds of basics, like conservation of baryon number, conservation of lepton number, conservation of charge, etc.
Matter and energy are not the same two things. You may exchange one for another, under limitations, but don't think that they are in any way identical.
As for experiments... well, the article discusses experiments to test for the existence of these "large" extra dimensions, but "small" (Planck-scale) effects are much harder to see.
Actually this is a perfectly sensible and serious theory, which has been around for 10 or 15 years, in various guises, it has just suffered from abbrevation and simplification.
Regarding the comparisons, if you take any fundamental particle in the universe which actually has both mass and charge and place an identical particle at rest 1m away from it, the electrostatic force between them exceeds the gravitational by many orders of magnitude. If you want a theory that explains both electromagnetism and gravity as aspects of the same thing (which is generally considered desirable) then it has to explain this huge discrepancy.
Regarding the dimensions, imagine a 1mm^2 two-dimensional creature living on the outer surface of a garden hose. It has two very different dimensions: along, which is practically infinite (althoiugh explorers may claim to have reached the mythical "tap" and "spout") and around, in which you can go only a few dozen body-lengths before you get back to your starting point.
Actually an even closer analogy would be to imagine creatures living on the hose big enough to actually wrap round it in places. Fundamental particles are supposed to be entangled with the extra dimensions in this way.
Because G is small.
:-) I'd like to know why G constant is the way it is.. what does it stand for? The number of angels who can dance of the head of a pin? The number of massless spin 2 bosons which can fit into a 3x3 room which has a 2.5 people in it?
The equation for measuring the gravitation force between two objects is the same as the equation for measuring the electromagnetic force between two objects, except for the constant.
If you want to figure out why gravity is weak, figure out why G is small. There are a lot of "magic numbers" used in physics that were measured through experimentation, but which have no explanation. As a programmer, I find the situation intollerable
Once we know where the magic numbers come from, we'll have a better chance of understand how things work on the lowest (i.e.: quantum) levels where they likely originate.
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Somebody else posted a cool link, but I don't have moderator points to bump it up. I do, however have karma to burn, so here it is.
Gravity IS the weakest of all known forces of nature. If you compare the force of gravity to the other forces: weak&strong nuclear force and electro-magnetic force, than gravity is far far behind.
The fact gravity is felt strong to us is just because any other force is balanced on large scale, and thus we feel only "residual" force. There are positive and negative electric charges, whereas the strong nuclear force is created by three-color quarks that balance each other.
Anyone with a good scientific background can see that this article is very flawed. Here are some examples:
Although we think of gravity as strong -- we can get hurt if we fall down -- compared to electromagnetism, gravity is astonishingly weak. It takes the gravity of the whole Earth to hold a pin on a tabletop; a toy magnet can lift it easily.
Ehm, excuse me but doesn't the phrase "comparing apples to oranges" come to mind here? I mean how the hell can you compare two forces with completely causes? It is just as absurd as saying that 1 gram is more than 1 coulomb.
Gravity is related to mass, and electromagnetic forces on charge. How can someone compare the mass of the earth with the charge in the atoms in a magnet? They are totally different things.
The notion sounds deceptively simple: besides the familiar three dimensions of space there may be other dimensions, too small to see yet perhaps as large as a millimeter.
Dimensions do not have a size. Objects have sizes in a set of dimensions.
I hope Sla
Perhaps you should have turned round and asked the doctorate in physics, behind you.
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Does this mean that we will be able to build gravity bombs so we can preemptively defend ourselves from invasion from those other dimensions? "Let's 'grav' those suckers before they decide to come over here and take our stuff."
This is starting to sound too much like the Seth books. In one of the books (don't remember which one) he claims matter is time-shared between dimensions. So we get our little time slice, then we are suspended and some other dimension gets a chance to "run". (He didn't mention what happens if our swap space gets corrupted though.)
When I was reading through some topology book when I was in high school it seemed to make perfect sense to me that if folds of the universe were sufficiently "close" to each other (perhaps even *overlapping) that they could have some sort of interaction. In fact, this is what wormholes are (supposed to be).
Just imagine a tablecloth on a table. Now ruffle it up. The surface of the tablecloth is actually a three dimensional world. If you trace your finger accross the surface you are travelling in space. But what if you could "jump" through a ruffle, from the upslope of the ruffle to it's downslope (or vice versa). What if a magnet on one side of the ruffle attracted a piece of metal on the other side "through" the tablecloth. That is sort of what this theory is saying. Close folds are having a dampening affect on the local gravity. The best theories are the ones that just "make sense" in retrospect.
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Could this explain why our universe is expanding or moving apart? Say, for example, that we were in one of those small dimensions and the gravity from this dimension was propagating across and acting on our universe, wouldn't that pull it apart?
Also, if we can learn how to manipulate gravity, could this allow cross-dimensional communications? I also read that gravity propagates at c^2, this would be excellent for interstellar communications.
Of course I'm most likely talking out my ass. Damn, I wish I had taken particle physics courses in college. Time to buy some books I guess.
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It is quite an interesting article. However it shows an all-time stereotype that we are some sort of center. It seems that Relativity teached absolutely nothing to a bunch of monkeys that just came out of the trees.
What if this, "our" Universe is just a projection of much larger structures? No we are not looking through 3-4 dimensions over two or five or seven more. We could be folded in three dimensions that result from something much larger and bigger. Or "our" Universe could be the result of the intersection of two or more "meta-Universes".
You may argue quite strongly with this. Well I'm not pointing how the Universe is made. I'm pointing on how we look at the Universe. Imagine that our Universe is made of five dimensions. What tells you that you are "in the center of it"???? You could well be in the first three or last three. The two other you don't see, feel, taste. As much as what you see is just a 0,01% of what sorrounds you. Besides you see nothing. All what you "see" is the result of how your eyes and brain produce out of something beyond you. Forget about radio waves, infra-red, ultra-violet, X-rays, your sunglasses and your short-sightness and you can still say "I see the world" with the same success.
When one talks about "other dimensions" should be very careful. Because it will be quite serious the problem on how we are positioned to them. I would wildly laugh if suddenly anyone found the "originator" of gravity in the dimension next to us. No one knows how exactly gravity is made of. And G is, until the biggest mistery of all. I consider that this article fails in this little thing. It considers gravity as "weakening" through dimensions. Could it be that gravity is born from "travelling" through them? We are talking about dimensions. This is not a thing that stays next door. It is in every quantum of our Universe. a dimension determines a section of the space. And we live in it.
PS: Again about relativity. For the hard-thinkers. What is the correct theory: geocentrism or heliocentrism. Note: both are correct. The problem is that it is much simpler to calculate planet dynamics from a heliocentristic point of view. However if you are hard in maths we can do this from a geocentristic point of view. The problem is that you have to do a lot more of maths to achieve this. And be quite careful about forces and gravity. However it is done. Many observational tasks are made from a goecentristic point of view. Middle Age geocentrism failed because it ignored completely Dynamics and mixed everything in a mystical-religious-political pan. However you still can say with some success that you are in the center of the Universe. The problem is that you have to be a damn mathematician to do it...