How does physics explain the graviton?

Chemistry4me · « **on:** 14/03/2009 09:30:39 »

How does physics explain the graviton? [

]
Can one of you clever people out there please tell me how physics explains the fact that when I let go of a ball, it falls to the ground? What on Earth is going on here? How does this (hypothetical?) graviton interact with the ball so that it falls to the ground? [

]

lightarrow · « **Reply #1 on:** 14/03/2009 10:57:32 »

Quote from: Chemistry4me on 14/03/2009 09:30:39

How does physics explain the graviton?

It doesn't. Infact gravitons don't exist.

Chemistry4me · « **Reply #2 on:** 14/03/2009 10:59:40 »

Okay, so what happens? [

]

lightarrow · « **Reply #3 on:** 14/03/2009 11:01:01 »

Quote from: Chemistry4me on 14/03/2009 10:59:40

Okay, so what happens? []

Do you mean why a ball falls to the ground?

Chemistry4me · « **Reply #4 on:** 14/03/2009 11:01:30 »

Quote from: lightarrow on 14/03/2009 11:01:01

Quote from: Chemistry4me on 14/03/2009 10:59:40
Okay, so what happens? []
Do you mean why a ball falls to the ground?

Yes.

Chemistry4me · « **Reply #5 on:** 14/03/2009 11:03:36 »

Perhaps it is something that physics cannot explain just at this moment? [

]

lightarrow · « **Reply #6 on:** 14/03/2009 11:15:21 »

Quote from: Chemistry4me on 14/03/2009 11:03:36

Perhaps it is something that physics cannot explain just at this moment? []

Why? It explains it from Newton; it's already several centuries! The last explanation I know is the one of GR: mass bends spacetime so the ball is forced to follow that bending.

DoctorBeaver · « **Reply #7 on:** 14/03/2009 11:15:52 »

I think I'm right in saying that the graviton only exists in Quantum Field Theory. It is basically postulated to make gravity work in the same way as the other known forces: i.e. by the exchange of guage bosons like the W & Z bosons of the weak force.

General Relativity says that objects move towards each other due to the curvature of space that is caused by the presence of matter (matter tells space how to curve and space tells matter how to behave). It doesn't however, give any indication as to how that curvature occurs.

Chemistry4me · « **Reply #8 on:** 14/03/2009 11:20:49 »

Quote from: lightarrow on 14/03/2009 11:15:21

mass bends spacetime so the ball is forced to follow that bending.

Quote from: DoctorBeaver on 14/03/2009 11:15:52

General Relativity says that objects move towards each other due to the curvature of space that is caused by the presence of matter (matter tells space how to curve and space tells matter how to behave).

So basically the ball falls to the ground because spacetime tells it to?

DoctorBeaver · « **Reply #9 on:** 14/03/2009 11:40:30 »

According to GR it doesn't "fall" at all. It tries to follow a geodesic.

lightarrow · « **Reply #10 on:** 14/03/2009 11:45:07 »

Quote from: DoctorBeaver on 14/03/2009 11:15:52

I think I'm right in saying that the graviton only exists in Quantum Field Theory. It is basically postulated to make gravity work in the same way as the other known forces: i.e. by the exchange of guage bosons like the W & Z bosons of the weak force.

Yes, but there is just a little problem: gravity is still not described by quantum mechanics...
Gravitons comes from a speculative "attempt" to describe gravity quantum mechanically, but it's actually illegitimate, in the absence of a real quantum theory of gravity.

Chemistry4me · « **Reply #11 on:** 14/03/2009 11:46:36 »

Hmmm... now I'm confused. [

][

]

DoctorBeaver · « **Reply #12 on:** 14/03/2009 11:47:59 »

Quote from: lightarrow on 14/03/2009 11:45:07

Quote from: DoctorBeaver on 14/03/2009 11:15:52
I think I'm right in saying that the graviton only exists in Quantum Field Theory. It is basically postulated to make gravity work in the same way as the other known forces: i.e. by the exchange of guage bosons like the W & Z bosons of the weak force.
Yes, but there is just a little problem: gravity is still not described by quantum mechanics...

I'm aware of that. Any theory that explains gravity will have to be more fundamental.

lightarrow · « **Reply #13 on:** 14/03/2009 11:49:51 »

You two write at the speed of sound! I couldn't edit my post that you already have written two of them! [

]

DoctorBeaver · « **Reply #14 on:** 14/03/2009 11:54:19 »

Quote from: lightarrow on 14/03/2009 11:49:51

You two write at the speed of sound! I couldn't edit my post that you already have written two of them! []

I may be ill but I can still type fast

DoctorBeaver · « **Reply #15 on:** 14/03/2009 11:56:03 »

Quantum physics is certainly not the final word

DoctorBeaver · « **Reply #16 on:** 14/03/2009 11:56:28 »

Quote from: Chemistry4me on 14/03/2009 11:46:36

Hmmm... now I'm confused. [][][]

About what?

Chemistry4me · « **Reply #17 on:** 14/03/2009 12:04:54 »

EVERYTHING!

And don't tell me that you're not!

DoctorBeaver · « **Reply #18 on:** 14/03/2009 12:08:34 »

I'm not confused by it. I know there are things about QM & gravity that I don't understand and that's it.

Chemistry4me · « **Reply #19 on:** 14/03/2009 12:12:26 »

Fine, I'll just go sulk in the corner.

DoctorBeaver · « **Reply #20 on:** 14/03/2009 12:31:40 »

awwwww there there

Vern · « **Reply #21 on:** 14/03/2009 14:06:24 »

Gravity is an unusual critter when you try to fit it in with the other forces of nature. It is the weakest of the forces and yet can assemble the universe into structures we can barely imagine. Yet, there is a way to unite gravity and the electromagnetic forces that lets them reside comfortably in the same quantum governed universe.

The link is to Photonic Gravity in the New Theories forum. I just added a last paragraph to sum up the concept in one short paragraph, so I won't repeat it here.

yor_on · « **Reply #22 on:** 14/03/2009 14:50:36 »

Quote from: Chemistry4me on 14/03/2009 09:30:39

How does physics explain the graviton? []
Can one of you clever people out there please tell me how physics explains the fact that when I let go of a ball, it falls to the ground? What on Earth is going on here? How does this (hypothetical?) graviton interact with the ball so that it falls to the ground? []

This is from a guy working in it

"Gravitons are closed strings. All strings can produce closed strings so all particles couple to gravity. Unlike other forces, which are related to open strings stuck to a brane, which limits the motion of the string ends, closed strings have no ends to stick to anything and therefore can move freely in any direction. This is the qualitative explanation of why gravity is so weak, it quickly dilutes itself through 10 dimensions, while photons are stuck to only spreading out in 3 dimensions. Strings, open or closed, can split and join so a closed string can 'pinch off' another closed string, which is two gravitons interacting."

And as I understand it it comes from QTF (Quantum field theory) The Standard model is another one of the theories collected under that umbrella. But in Standard Theory we didn't succeed to bind gravity to anything specific, when trying it only went to 'infinities',(gravitation is nonrenormalizable.) so we needed a new approach if we wanted to see gravity a a 'force' with its own 'carriers'. All the other forces we had succeeded in binding to particles, electromagnetisms to photons, the strong interaction to gluon's etc but not gravity. So there is where string theory comes in.

"Unlike the point particles (A point particle does not have any volume or surface area, it is zero dimensional) in quantum field theories like the standard model, strings interact in a way that is almost uniquely specified by mathematical self-consistency, forming an apparently valid quantum theory of gravity"

Looking at it mathematically it seemed very fitting apparently, although it creates a very weird universe at times:)

It all depends on how you see vacuum, if it only is a 'nothing',then where would the dips and heights of it be, gravitationally speaking? If it is something other, not an aether, but something holding in itself more than just a 'nothing', f ex, a 'matter-space symmetry' like I think at times, then I think it's possible to be satisfied with Einsteins description of it. But if it's a 'nothing' and gravity still behaves as it does, then we will have too look for an extraneous force like gravitons. Maybe I'm wrong, but that's how I see it.

Vern · « **Reply #23 on:** 14/03/2009 20:56:53 »

That looks like string theory yor_on. I think there is five or six versions out there now. Then there's the M theory that tries to combine all the string theories as sub-sets of itself. Now I see a lot of attention being given to Many Worlds Theory. In MWT all possible happenings occur simultaneously in multiple universes.

I kinda hope that none of those really catch on enough to garner a seizable portion of the available funding. My chances of understanding enough about any of those to make sense of them is small. [

]

DoctorBeaver · « **Reply #24 on:** 14/03/2009 22:56:18 »

Vern - don't forget 10-dimensional supergravity!

Vern · « **Reply #25 on:** 14/03/2009 23:14:05 »

Oh yeah; that one too. I particularly don't like SUGRA.

DoctorBeaver · « **Reply #26 on:** 15/03/2009 00:43:27 »

I have half a spoon of it in coffee. Preferably Demerera.

Chemistry4me · « **Reply #27 on:** 15/03/2009 02:34:42 »

What the heck are you boys talking about?

DoctorBeaver · « **Reply #28 on:** 15/03/2009 04:51:01 »

SUGRA - SUperGRAvity

Chemistry4me · « **Reply #29 on:** 15/03/2009 04:56:28 »

What's Super Gravity? What is that all about?

DoctorBeaver · « **Reply #30 on:** 15/03/2009 09:14:41 »

erm... I'll let Vern explain

I can't explain it because I know nothing about its equivalence to strongly coupled 10d string theory or why M-theory says there is such an equivalence. All I know is that it's weakly coupled so it can be perturbated whereas strongly coupled string theory can't.

Of course, I was wrong when I said the graviton only exists in QFT. I forgot that it exists in SUGRA too as it's a field theory combining supersymmetry with general relativiy. Naturally, being supersymmetric, there is an anti-graviton too - the gravitino which has spin 3/2. But you don't want to hear about that.

And you wouldn't want to know about the long wavelength limit of M-theory being described by 11-dimensional supergravity.

No, you wouldn't want to hear about any of that.

Chemistry4me · « **Reply #31 on:** 15/03/2009 09:54:37 »

Who the heck comes up with this kind of stuff?!? [

][

]
Why is physics so confusing and complicated? [

][

]

DoctorBeaver · « **Reply #32 on:** 15/03/2009 09:57:43 »

Quote from: Chemistry4me on 15/03/2009 09:54:37

Who the heck comes up with this kind of stuff?!? [][]

Daniel Z. Freedman, Peter van Nieuwenhuizen and Sergio Ferrara. That nice Ed Witten fiddled around with it somewhere along the line too.

Chemistry4me · « **Reply #33 on:** 15/03/2009 09:58:50 »

That was a rhetoric, but thank you for answering. [

]

Now to the second question. [

]
I think it's just me. [

]

Chemistry4me · « **Reply #34 on:** 15/03/2009 10:00:04 »

Alright, I shall wait for Mr. Vern to enlighten me on this matter. [

]

DoctorBeaver · « **Reply #35 on:** 15/03/2009 10:03:15 »

Quote from: Chemistry4me on 15/03/2009 09:58:50

Now to the second question. []

Stick to sheep. It's less confusing.

Chemistry4me · « **Reply #36 on:** 15/03/2009 10:05:45 »

But I'm confused already [

][

]

Chemistry4me · « **Reply #37 on:** 15/03/2009 10:09:14 »

I like the: 'Sheeplifters will be prosecuted' [

]

Take note also of the: 'Physics graduate sheep'. [

]

Vern · « **Reply #38 on:** 15/03/2009 12:40:34 »

http://en.wikipedia.org/wiki/Supergravity [Links inactive - To make links active and clickable, login or click here to register] is a pretty good treatment of Super Gravity. The quote below are some of the problems with SUGRA. I think SUGRA began as an attempt to explain gravity within the Super Symmetry theory. I can't add much. I really do hope nature does not behave super symmetrically.

Quote from: the article

The end of the SUGRA era

The initial excitement over 11-dimensional supergravity soon waned, as various failings were discovered, and attempts to repair the model failed as well. Problems included:

* The compact manifolds which were known at the time and which contained the standard model were not compatible with super-symmetry, and could not hold quarks or leptons. One suggestion was to replace the compact dimensions with the 7-sphere, with the symmetry group SO(, or the squashed 7-sphere, with symmetry group SO(5) times SU(2).

* Until recently, the physical neutrinos seen in the real world were believed to be massless, and appeared to be left-handed, a phenomenon referred to as the chirality of the Standard Model. It was very difficult to construct a chiral fermion from a compactification — the compactified manifold needed to have singularities, but physics near singularities did not begin to be understood until the advent of orbifold conformal field theories in the late 1980s.

* Supergravity models generically result in an unrealistically large cosmological constant in four dimensions, and that constant is difficult to remove, and so require fine-tuning. This is still a problem today.

* Quantization of the theory led to quantum field theory gauge anomalies rendering the theory inconsistent. In the intervening years physicists have learned how to cancel these anomalies.

Some of these difficulties could be avoided by moving to a 10-dimensional theory involving superstrings. However, by moving to 10 dimensions one loses the sense of uniqueness of the 11-dimensional theory.

The core breakthrough for the 10-dimensional theory, known as the first superstring revolution, was a demonstration by Michael B. Green, John H. Schwarz and David Gross that there are only three supergravity models in 10 dimensions which have gauge symmetries and in which all of the gauge and gravitational anomalies cancel. These were theories built on the groups SO(32) and E_8 \times E_8, the direct product of two copies of E8. Today we know that, using D-branes for example, gauge symmetries can be introduced in other 10-dimensional theories as well.

DoctorBeaver · « **Reply #39 on:** 15/03/2009 13:02:11 »

If you knew SUSY like I know SUSY!

I too have doubts about it. It seems like a kludge to me.

Chemistry4me · « **Reply #40 on:** 16/03/2009 05:16:25 »

Jeez, that stuff is confusing. [

][

]

Chemistry4me · « **Reply #41 on:** 16/03/2009 10:18:12 »

I'm still here you know? [

]

Chemistry4me · « **Reply #42 on:** 16/03/2009 10:26:11 »

Why are you talking about me behind my back?

DoctorBeaver · « **Reply #43 on:** 16/03/2009 14:31:06 »

Quote from: Chemistry4me on 16/03/2009 10:26:11

Why are you talking about me behind my back?

Coz it's easier on the eye than your front [

]

yor_on · « **Reply #44 on:** 17/03/2009 00:08:32 »

Mr Chem, that was a sheep trick, introducing Lambert to gravity.

No disrespect meant here Neil

As for "I think it's just me."

Count me in.

Chemistry4me · « **Reply #45 on:** 17/03/2009 07:48:11 »

Quote from: DoctorBeaver on 16/03/2009 14:31:06

Quote from: Chemistry4me on 16/03/2009 10:26:11
Why are you talking about me behind my back?

Coz it's easier on the eye than your front []

Oi...! Com' ova 'ere you!

--------

Quote from: yor_on on 17/03/2009 00:08:32

Mr Chem, that was a sheep trick, introducing Lambert to gravity.

I liked it. [

]

DoctorBeaver · « **Reply #46 on:** 17/03/2009 11:06:25 »

AHEM... going back to the question (sort of; and even then via the scenic route):

I have serious doubts about whether gravity would unify with the other forces at high energy. I am very taken by the idea of braneworlds in a higher dimensional bulk. The other forces we experience (EM, weak & strong) are sequestered on our 3d brane (3 spatial dimensions; leave time out of this for now) but gravity is everywhere.

If our universe is a brane that was brought into existence at the moment of the Big Bang then gravity would already have been around in the higher dimension whereas the other forces came into existence with the Big Bang. There is no reason to suggest they exist anywhere else.

To my mind, attempts at unifying gravity with the other forces are pointless because no such unity exists. TOEs are full of fudges & kludges that seem to be no more than mathematicians' playthings. Layer upon layer of complexity is added to patch holes that exist in the theories. Those layers, in turn, have holes in them that require more patches and so on. It's worse than a Microsoft OS (OK, maybe not). By accepting that gravity is totally separate from the other forces we can do away with all that complexity & desperate fine-tuning.

That doesn't, though, preclude the possibility of gravitons (See? I did get back to them). If they exist they would be the most fundamental of particles as they were the only ones that existed before the Big Bang. Although it hasn't been proven, it's possible that gravity affects every type of particle so maybe they can all produce gravitons in the same way that electrons can produce photons. Or maybe every other type of particle is made of gravitons; even electrons & quarks. It's beyond my little brain to contemplate that possibility too much so I'll leave it to those with more understanding of the subject.

Vern · « **Reply #47 on:** 17/03/2009 13:55:20 »

Quote from: DoctorBeaver

To my mind, attempts at unifying gravity with the other forces are pointless because no such unity exists. TOEs are full of fudges & kludges that seem to be no more than mathematicians' playthings. Layer upon layer of complexity is added to patch holes that exist in the theories. Those layers, in turn, have holes in them that require more patches and so on. It's worse than a Microsoft OS (OK, maybe not). By accepting that gravity is totally separate from the other forces we can do away with all that complexity & desperate fine-tuning.

I see no problem at all with unifying gravity with the other forces. Photons attract each other. Everything is made of photons. Bingo; we have gravity [

]

That is a simplistic way of putting it, but it is essentially the way to get gravity and electromagnetism united. The exact mechanism is only slightly more complicated. I don't feel a real need to plunge into multi-brane universes [

]

JukriS · « **Reply #48 on:** 17/03/2009 14:12:48 »

When particle is new, is hot/density and that particle time is slowly!

Thats why new particle dont emit energy fast and that why is not giving kinetic energy for expanding atoms nucleus!

When particle is old, is not so hot/density and time is not so slowly and thats why particle emit energy fast. Thats why particle giving kinetic energy for expanding atoms nucleus!

thats why we stay earth skin with out gravity, you know!

thats why you can see old light who is redshifting!

Not, because space expanding!

space dont expanding or curving/bending at all!

.

Vern · « **Reply #49 on:** 17/03/2009 15:04:24 »

Quote from: JukriS on 17/03/2009 14:12:48

When particle is new, is hot/density and that particle time is slowly!

Thats why new particle dont emit energy fast and that why is not giving kinetic energy for expanding atoms nucleus!

When particle is old, is not so hot/density and time is not so slowly and thats why particle emit energy fast. Thats why particle giving kinetic energy for expanding atoms nucleus!

thats why we stay earth skin with out gravity, you know!

thats why you can see old light who is redshifting!

Not, because space expanding!

space dont expanding or curving/bending at all!
.

I like your videos. My suspicion is that you are better at making videos than you are at making GUTs. [

]

How do we know that the "laws" of physics are really laws, i.e. true everywhere? Started by rainwildmanBoard Physics, Astronomy & Cosmology	Replies: 32 Views: 14574	27/04/2008 11:14:42 by bitistoll
Why has the physics forum got sexier topics than the chemistry forum? Started by Mr AndrewBoard Chemistry	Replies: 61 Views: 32087	03/03/2009 03:39:33 by Chemistry4me
Is the most profound quest in all of physics the "Theory of Everything"? Started by Alan McDougallBoard Physics, Astronomy & Cosmology	Replies: 4 Views: 1009	16/06/2016 20:46:56 by IAMREALITY
The expression "A moment in time" does it exist in physics? Started by Alan McDougallBoard Physics, Astronomy & Cosmology	Replies: 11 Views: 4199	03/07/2013 09:59:09 by yor_on
Should we consider quantum physics and general relativity as two seperate systems, active in the same universe? Started by thedocBoard Physics, Astronomy & Cosmology	Replies: 4 Views: 823	27/07/2016 20:32:04 by alancalverd

How does physics explain the graviton?

Chemistry4me (OP)

Chemistry4me (OP)

Chemistry4me (OP)

Chemistry4me (OP)

Chemistry4me (OP)

Chemistry4me (OP)

Chemistry4me (OP)

Chemistry4me (OP)

Chemistry4me (OP)

Chemistry4me (OP)

Chemistry4me (OP)

Chemistry4me (OP)

Chemistry4me (OP)

Chemistry4me (OP)

Chemistry4me (OP)

Chemistry4me (OP)

Chemistry4me (OP)

Chemistry4me (OP)

Chemistry4me (OP)

Similar topics (5)