It is proven. Gravity expands at speed of light

[Seeker]

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.

[TCO]

Originally posted by Sagacious Dolphin



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

You're just trying to show off.

Finance weenie.

[Craig P.]

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).

[TCO]

Is it like a doppler shift? What exactly do they measure?
angle? times?

[Ramo]

Hmm.. interesting. Good to know GR isn't total bollocks.

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.

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).

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.

[Urban Ranger]

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.

[Lars-E]

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.

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.

[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....)

[shade]

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/ask_astro/answers/961102.html

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

[Sava]

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

[Urban Ranger]

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.

[Sava]

thanks UR... its nice to see that some people can give a straight answer instead of a dumb 4ss insulting response.

[Az]

we now know you don't really read what it says

read my following post.

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

[Eli]

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.

[TCO]

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?