Why Even Talk About Gravitons Even Existing?

  • #26
1,477
1
I don't have a problem with thinking of gravity as spacetime deformation instead of a "force" field, and of gravitons as the quanta of spacetime deformations. The point is that we don't have a theory that works that way. Or any other way, for that matter.

Just a small problem there. :wink: Maybe within our lifetimes we'll see it.
 
  • #27
104
0
Just a small problem there. :wink: Maybe within our lifetimes we'll see it.

Yea way to add intelligent insight into the conversation there buddy.

To the rest of you, thank you very much for your answers and links for examples. I will look over all of your responses and the links you have provided me and see if I can retort and/or understand better the topic.
 
  • #28
104
0
I don't have a problem with thinking of gravity as spacetime deformation instead of a "force" field, and of gravitons as the quanta of spacetime deformations. The point is that we don't have a theory that works that way. Or any other way, for that matter.

How can you NOT have a problem with this? There is nothing to prove or suggest that this is the right way to look at gravity at all. Why are you comparing they way light works and behaves to the concept of gravity? Possibly because E = MC^2?

Still not a good enough reason.....I am sure you have another but I would like to hear it.


PS - Your earlier statement seems to be correct. Anything with any mass (no matter how tiny or miniscule by our standards) will exert some sort of curvature on space-time (hence gravity at an atomic level).

Link: https://www.physicsforums.com/archive/index.php/t-118327.html
 
  • #29
Ich
Science Advisor
1,931
1
How can you NOT have a problem with this?
Maybe I'm rather the uncomplaining type of guy?

There is nothing to prove or suggest that this is the right way to look at gravity at all.
There is nothing to prove it, but the theoretical analysis of gravitational waves in the weak field limit suggests that it's associated with a massless spin-2 particle.
Why are you comparing they way light works and behaves to the concept of gravity? Possibly because E = MC^2?
No, because both follow a wave equation (I'm talking about gravitational radiation here), and QM tells us how to quantize waves. But it doesn't tell us how to quantize the full-fledged nonlinear theory.
 
  • #30
Chronos
Science Advisor
Gold Member
11,429
742
I'm stuck on the wave thing. It is difficult to conceptualize gravitational waves without bosons - sort of like an ocean wave without water molecules. Bosons may not be an ideal explanation, but it works for all the other fundamental forces. An effective theory is not necessarily a bad thing. Why it works - that is for our children to solve.
 
  • #31
154
0
From what I have read out there, of the four fundamental forces that have been detected in our universe, gravity seems to be the weakest at the atomic level and smaller.

I figure this is most likely true because at the atomic level and smaller - the weak and strong forces (those causing beta decay and gluons to hold quarks inside of protons and neutrons) are the forces that build matter at an atomic level.

Gravity seems to only rear it's head when the mass of any object is that of an atomic mass or higher. The larger the mass of anything....the more gravity plays a role according to Einstein's general relativity principles.

Therefore gravity is a force that needs to be separated from the other three major forces because it doesn't seem to appear or work at levels smaller than anything smaller than an atom.

If this is all true....then why the need to even talk about mass-less particles like gravitons even existing in the first place? After all, Einsteins' Gen. Relativity Theory says gravity is nothing more than the physical bending or curving of the space-time fabric which anything that has mass on it does. Thus it's nothing more than a force that only shows up when masses are that of an atom or larger and not at the quantum level.

I think the main thing to remember is that while gravity is a very weak force of nature, it still exists. I understand that you're saying "at the quantum level" but you cannot simply ignore a it all together. I think its important to include gravity at the table of quantum discussion because the very fact is that it exists, no matter how strongly or weakly it effects things at the sub-atomic level.

Also, it's important to look far and wide when considering questions like the one that you have posed; if you take away gravity (or stop talking about it) than at some point the math stops working. And that as you know is bad. Gravity has quantum implications, they're just very, very weak.
 
  • #32
Saying that gravity should be ignored from the quantum level and should only be considered with [tex]\geq[/tex] atomic, doesn't make much sense. Because atoms consist of nuclei and other smaller quantum subatomic particles...which all together work together and has a gravitational interaction, although gravity is quite weak it's obviously out there and a very strong force at the macroscopic level. But, the quantum level has to be considered, cause like sEsposito said, the math won't work and that IS bad
 
  • #33
88
0
NYSportsguy.
Gravity is produced by any energy. That includes light.
For ex. the Earth's gravity is produced by its mass-equivalent energy, its rotational energy, its thermal energy, and any other energy i haven't thought of.
The total energy is responsible for the total gravitation.
Mass-equivalent energy is by far the biggest contributor.
http://en.wikipedia.org/wiki/General_relativity
 
  • #34
154
0
In contrast to what the starter set out to accomplish -- this thread has really demonstrated the importance of gravity (especially at the sub-atomic level!)... So many well informed replies.

I think its really cool when I can find the importance in something someone set out to nullify.
 
  • #35
qwe
25
0
In my opinion it seems a bit far-fetched to link gravity to the other three major fundamental forces considering the other three are all strong at the atomic and smaller levels while gravity usually only rears it's head at large mass levels
well ONE of the four forces has to be the smallest of the four, assuming they all aren't the same, right?...
 
  • #36
104
0
In contrast to what the starter set out to accomplish -- this thread has really demonstrated the importance of gravity (especially at the sub-atomic level!)... So many well informed replies.

I think its really cool when I can find the importance in something someone set out to nullify.

To be honest with you.....I posed this question because I wanted to get a thoughtful discussion going. I really wasn't trying to "nullify" anything. My purpose was to get an end outcome that either justified the need to look for "gravitons" or disprove it as a myth.

Either resolution or outcome would have been just fine with me. :smile:
 
  • #37
1
0
Hi Admin,
Where is my post?

Thanks
Br, Raja
 
  • #38
jtbell
Mentor
15,809
4,063
raja16sep, please read your Private Messages. The explanation is there.

Either click on "My PF" at the top left of any page here, or click on the "Your Notifications" link at the top right of any page (below the "Welcome, raja16sep" message).

If you have further questions about your post, send a PM to the mentor who notified you about it. Don't start a discussion about it here.
 
  • #39
9
0
How would an experimenter detect a graviton?.
Can they travel at any speed or just the speed of light (like a gravitational wave)?.
 
  • #40
42
0
I've posted this elsewhere, but it is just so appropriate here that here it is again:


BREAKING SYMMETRY
-- James Ph. Kotsybar

Our universe has things in it because
chance quantum fluctuations enable.
Nothing is what violates Nature’s laws --
something is apparently more stable.
Super-symmetry was asking for it.
It was just too perfect to be withstood,
and once it took the predictable hit
it lit up the entire neighborhood,
and in that Big Bang, the forces all split.
Gravity, of course, was most serious
and left, having little to do with it,
and, to this day, remains mysterious.
Though we still work to unify them all,
Entropy says it’s too late for that call.
 
  • #41
PAllen
Science Advisor
8,427
1,686
Light doesn't cause gravity to occur because it is mass-less. A black hole (being extremely massive) causes the light to get sucked into it.....not sure what your example is trying to say. If anything it further strengthens my QUOTE....not weakens it.

The source of gravity includes pressure and energy as well as rest mass. A 'box of light' does gravitate. In the GR field, the properties of an idealized 'box of light' are often investigated.
 
  • #42
42
0
How would an experimenter detect a graviton?.
Can they travel at any speed or just the speed of light (like a gravitational wave)?.

I believe that the prevailing theory is that gravity waves travel at light speed. If the moon were to suddenly disappear, we would feel the effects the same time we saw it go (but both observations would be limited to light speed).
 
  • #43
The level, at which this question on existance of graviton is asked, the science is still developing. Recent studies on neutrinos and accelrating universe are all part of the same. To develop science has always taken the path, - hypothesis, test, confirm and formulate the verifiable truth as an accepted concept or universal law.

PicoPhysics: Gravitons, big bang, general relativity are all different side of same coin, we still need to understand a lot about nature.
 
  • #44
42
0
DARK ENERGY QUESTION
-- James Ph. Kotsybar

Could inflation have done more than we know,
shortly after the Big Bang’s first salvo,
and created a dense matter halo
beyond the horizon where we can go?

Beyond the horizon that we can see,
is there a remote possibility
of a most massive field of gravity
that pulls the strings of our reality?

Perhaps it’s just dense matter that’s the source,
accelerating expansion perforce,
and not some new and mysterious force,
or attractive gravity changing course,
as though we are bound by a black hole’s skin,
stetching space toward a surface dimension.:surprised
 

Related Threads on Why Even Talk About Gravitons Even Existing?

  • Last Post
Replies
5
Views
3K
  • Last Post
Replies
3
Views
2K
Replies
5
Views
2K
Replies
35
Views
3K
Replies
4
Views
2K
Replies
0
Views
2K
  • Last Post
Replies
11
Views
3K
Replies
2
Views
2K
Replies
63
Views
2K
Top