10-01-2003 00:19									#31
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quote: Originally posted by Azazel With my humble knowledge I see a problem to describe the wavelike features of a graviton according to the de-broglie equation, because the wave's frequency is a function of the particle's mass. But do gravitons have mass? I don't think so.

Alva you're not alone. I am clearly not the one with most knowledge...

Anyway I'd like to humbly refute this with my humble knowledge as well. What about light?

	10-01-2003 00:24									#32
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quote: Originally posted by Azazel I find it cool. I would have done physics if I had a chance to work in cosmology or as a nuclear physicist. sadly I didn't. I wanted to go to biochemistry to cure cancer, and stop aging. The army didn't let me. Now I am in Chemistry, to make better Shampoos. I envy you, Richard. ( OMG, I don't believe I've just said it.... j/k )

So thats where all chem majors go. Working for herbal essence.... Nooooooo!~~~~~

	10-01-2003 00:28									#33
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good question, one second.

	10-01-2003 00:36									#34
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ok, Guess what? It appears that photons have mass after all.
a quick googlesearch has came up with the following link:

http://imagine.gsfc.nasa.gov/docs/a...ers/961102.html

quote: Now, being scientists, we do not just accept theories like general relativity or conclusions like photons have no mass. We constantly test them, trying to definitively prove or disprove. So far, general relativity has withstood every test. And try as we might, we can measure no mass for the photon. We can just put upper limits on what mass it can have. These upper limits are determined by the sensitivity of the experiment we are using to try to "weigh the photon". The last number I saw was that a photon, if it has any mass at all, must be less than 4 x 10-48 grams. For comparison, the electron has a mass of 9 x 10-28 grams.

well, what do you know....

	10-01-2003 00:40									#35
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you learn something new everyday.

Btw. Thats awfully small~ wow...

	10-01-2003 00:44									#36
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I just have to take quantum physics.

IIRC, btw, they've actually managed to freeze a light beam a couple of days ago. I really want to read about that.

back on topic.....

	10-01-2003 00:47									#37
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quote: Originally posted by Lars-E The stuff I read (sorry no link) talks about huge differences in the speed of light. Much faster before. It might have declined gradually.

i saw a docu on this about three years ago, it was some young scandanavian (i think) physicist who was working in the UK. Sorry can't remember much more, i'll try and be a bit more vague next time

	10-01-2003 00:56									#38
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Calc II: I keep looking for sources, and all they say is 'no it doesn't have mass, probably'.

	10-01-2003 02:44									#39
	Re: It is proven. Gravity expands at speed of light Support Apolyton, buy Galactic Civilizations: Deluxe Edition

quote: Originally posted by Tripledoc Gravity expands at speed of light It was proven today that gravity expands at the speed of light. This proves Einsteains theory. newton was convinced that the speed of gravity was infinite. The speed of gravity has until now been an unknown constant. It was discovered that the planet Jupiter would pass by (as seen from earth) the quasar JO842+1835 on september 8 2002. This meant that radiowaves from the quasar would be slightly bent as they passed the gravitational pull of Jupiter on their way to earth. the signal was picked up by the Very Long Baseline Array, a collection of large radio recievers on Earth placed in Hawaii, United States and Germany. The accuracy of the experiment compares to measuring the thickness of a human hair as seen from a distance of 400 kilometres. Until know gravity has been the great unknown and it is thus a step forwards towards a total and collective understanding of laws of the universe.

Are you sure that this experiment proves the speed of propogation of gravity. Or does it just prove that light is bent by gravity. (something shown in other experiments).

If it does prove what you are saying, could you explain a little more how? Thanks.

	10-01-2003 02:49									#40
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Yes, I was not sure how this was supposed to relate to the speed of propagation of gravity...

	10-01-2003 02:51									#41
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quote: Originally posted by Azazel the de-broglie equation says that all things have wavelike properties. The smaller the particle is, the more it is relevant. For example, contrary to what many people think, you can't see the electrons mooving around the nucleus in nice circular patterns. The electron is actually a cloud around the nucleus. That cloud takes different forms, for different atoms ( long story to explain ). for hydrogen for example, there single electron forms a cloud of probability, with the highest probability to find him being near the nucleus. That cloud never ends, though, so there is an infinetly small chance that electrons from your body are now actually in the alpha centauri system (!) With my humble knowledge I see a problem to describe the wavelike features of a graviton according to the de-broglie equation, because the wave's frequency is a function of the particle's mass. But do gravitons have mass? I don't think so.

There is a certain place where these things get metaphysical, but I think you can think of the electron not as a cloud but as a particle with indeterminate location. The "cloud" that you draw is a representation of the probability function across space. But not necessarily a smear of electron. (but this mayjust be a descriptional difference...)

	10-01-2003 03:01									#42
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quote: Originally posted by Azazel ok, Guess what? It appears that photons have mass after all. a quick googlesearch has came up with the following link: http://imagine.gsfc.nasa.gov/docs/a...ers/961102.html well, what do you know....

Shouldn't it have a mass by relativity? e=mc^2

E =hnu


m = hnu/c^2

	10-01-2003 03:08									#43
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I very much doubt that gravitons exist.

	10-01-2003 03:09									#44
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quote: Originally posted by GP Shouldn't it have a mass by relativity? e=mc^2 E =hnu m = hnu/c^2

E^2 = p^2c^2 + m^2c^4

	10-01-2003 03:53									#45
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*head explodes*

	10-01-2003 04:39									#46
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Lars E:

Your scientific paper is actually Tom van Flandern's site, where he offers a fancy looking Creationist arguement of the SoL changing over time, ultimately to justify how God could've created the universe 10 000 years ago.

	10-01-2003 05:25									#47
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quote: Originally posted by Sagacious Dolphin E^2 = p^2c^2 + m^2c^4

You're just trying to show off.

Finance weenie.

	10-01-2003 05:31									#48
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The experiment shows the speed of gravity based on the onset of the deflection of the light from the distant source. If gravity were instantaneous, it would deflect sooner than it did (by, I presume, a -very- small margin).

	10-01-2003 06:12									#49
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Is it like a doppler shift? What exactly do they measure?
angle? times?

	10-01-2003 07:02									#50
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Hmm.. interesting. Good to know GR isn't total bollocks.

quote: Is gravity a wave or a particle or both?

Well, the force-carrier for gravity would be both, if it exists. If it doesn't exist, gravity is just the geometry of space-time.

quote: With my humble knowledge I see a problem to describe the wavelike features of a graviton according to the de-broglie equation, because the wave's frequency is a function of the particle's mass. But do gravitons have mass? I don't think so.

Think for a minute about what the de Broglie relationship means. It tries to assign wave-like properties (traditionally thought of in the realm of massless particles like a photon) to massive particles. So it must be definition work for massless particles.

The de Broglie relationship describes frequency as a function of momentum, not necessarily mass. The relationship is sometimes expressed as a function of mass only to deal with everyday examples (baseballs and whatnot). For the proposed graviton and other massless particles p = E/c (as implied by the Lorentzian invariant SD posted).

quote: ok, Guess what? It appears that photons have mass after all. a quick googlesearch has came up with the following link:

Err.. that's not what the link says.

	10-01-2003 12:37									#51
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quote: Originally posted by Azazel ok, Guess what? It appears that photons have mass after all.

I have always thought that photons are assumed to have no rest mass, because of SR.

	10-01-2003 15:15									#52
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quote: Originally posted by reds4ever i saw a docu on this about three years ago, it was some young scandanavian (i think) physicist who was working in the UK. Sorry can't remember much more, i'll try and be a bit more vague next time

The guy I read about was a Russian scientist - early 20th century. There were several papers and more scientists.

quote: Your scientific paper is actually Tom van Flandern's site, where he offers a fancy looking Creationist arguement of the SoL changing over time, ultimately to justify how God could've created the universe 10 000 years ago.

You know where I got it? You know my height too? BS.

It was not there (never been to that site btw).

It's funny how you know more about me than I do myself. I have seen this irrational thinking in many ppl. Due to a lack of education?

I hate it when ppl jump to conclusions and only think every problem has one answer. Or that there is only one thing causing a reaction. There can be millions of motives/causes/answers/reasons to ONE problem. But you think there's a 1-1 relationship.

Simple-minded ness. I am sick of it.

	10-01-2003 15:58									#53
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Photons most certainly don't have mass, but it is impossible to comepletely prove this experimentally. All one can do is put an upper bound on the photon mass by experiment, and as the link says, that bound is really tiny.

Trust me - photons are massless.

Also, there is no problem decribing a massless particle quantum mechanically. The problem with describing the graviton quantum mechanically is not because it is massless, but because it has more angular momentum. It is spin 2, compared to the photon with spin 1.

This causes the quantum theory of gravity to be nonrenormalizable - when we calculate physical quantities with the theory we find that the results are dependent on the physics at really really high energies, which we don't know yet.

For the other theories like Quantum-Electro-Dynamics, the answers you get don't depend on the very high energy physics, so you can make predictions fine. (This property is why, for example, you don't need to do quantum mechanics to work out the dynamics of a bouncing ball....)

	10-01-2003 16:03									#54
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quote: Originally posted by Azazel ok, Guess what? It appears that photons have mass after all. a quick googlesearch has came up with the following link: http://imagine.gsfc.nasa.gov/docs/a...ers/961102.html quote: Now, being scientists, we do not just accept theories like general relativity or conclusions like photons have no mass. We constantly test them, trying to definitively prove or disprove. So far, general relativity has withstood every test. And try as we might, we can measure no mass for the photon. We can just put upper limits on what mass it can have. These upper limits are determined by the sensitivity of the experiment we are using to try to "weigh the photon". The last number I saw was that a photon, if it has any mass at all, must be less than 4 x 10-48 grams. For comparison, the electron has a mass of 9 x 10-28 grams. well, what do you know....

we now know you don't really read what it says
This article doesn't say Photon's have a mass, It says "IF" photon's would have a mass it would have to be less then 4x10-48grams...but it can be 0...

Shade

	10-01-2003 19:46									#55
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quote: Originally posted by Azazel don't be an ignoramus, Sava. almost all theoretical science leads better technology. 'electricity- and this helps human civilization how?'

No need to insult you little ****... I simply asked how this helps out. If I wanted a stupid 4ss answer, I would have asked my 7 year old cousin

	10-01-2003 19:49									#56
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quote: Originally posted by Sava No need to insult you little ****... I simply asked how this helps out. If I wanted a stupid 4ss answer, I would have asked my 7 year old cousin

Who knows? We don't have a crystal ball you know.

	10-01-2003 19:50									#57
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thanks UR... its nice to see that some people can give a straight answer instead of a dumb 4ss insulting response.

	10-01-2003 19:54									#58
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quote: we now know you don't really read what it says

read my following post.

quote: No need to insult you little ****...

	10-01-2003 20:13									#59
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I actually understand most of what people wrote here. Where's my shrink?

Seriously though. Dont you think it's all too complicated? Reading all the physics mumbo-jumbo mentioned in this thread I get this gut feeling that there is something very fundamental and very simple that we miss. Some equation, law, theory, perspective, that can be explained not only to PHDs and will make these issue much simpler.

It's like we spend all our efforts on adding numbers again and again and again, and cant think of multiplication.

	10-01-2003 21:22									#60
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quote: Originally posted by Rogan Josh Photons most certainly don't have mass, but it is impossible to comepletely prove this experimentally. All one can do is put an upper bound on the photon mass by experiment, and as the link says, that bound is really tiny. Trust me - photons are massless. Also, there is no problem decribing a massless particle quantum mechanically. The problem with describing the graviton quantum mechanically is not because it is massless, but because it has more angular momentum. It is spin 2, compared to the photon with spin 1. This causes the quantum theory of gravity to be nonrenormalizable - when we calculate physical quantities with the theory we find that the results are dependent on the physics at really really high energies, which we don't know yet. For the other theories like Quantum-Electro-Dynamics, the answers you get don't depend on the very high energy physics, so you can make predictions fine. (This property is why, for example, you don't need to do quantum mechanics to work out the dynamics of a bouncing ball....)

They don't have mass? Or don't have rest mass?

Shouldn't they have a mass based on their energy?