# Gravitational waves ?

## Recommended Posts

I was wondering, like sound waves are vibrational waves of particles. How exactly are gravitational waves related. So are they vibrations of atoms ? and if so are they transverse or longitudinal vibrations ?

##### Share on other sites

They are vibrations of space-time, or really in the curvature of or the metric on space-time.

##### Share on other sites

I was wondering, like sound waves are vibrational waves of particles. How exactly are gravitational waves related. So are they vibrations of atoms ? and if so are they transverse or longitudinal vibrations ?

The above link is an animation of how a gravitational wave would effect a ring of particles. The animation is taken from the Wikipedia article on Gravitational Waves here:

http://en.wikipedia....vitational_wave

Chris

##### Share on other sites

• 2 months later...

Gravitational waves are none trivial in Einsteins Theory, meaning that you can have a curvature of spacetime but not the presense of matter. This is of course the presence of gravitational waves. Gravitational waves would be the curvature itself.

##### Share on other sites

• 2 months later...

Gravitational waves are none trivial in Einsteins Theory, meaning that you can have a curvature of spacetime but not the presense of matter. This is of course the presence of gravitational waves. Gravitational waves would be the curvature itself.

While Ricci curvature vanishes in the absence of matter (flat space) there is still Weyl curvature propagating with gravitational waves. To my understanding the Weyl tensor is responsible for tidal effects (stretching, shrinking) in the x-y-plane (the wave propagates in z-direction). This is only true for small fields (plan wave solution). But I wonder whatelse the Weyl curvature is responisble for. Is the x-y-plane flat like Minkowski-spacetime? If not, are triangles in this plane oszillating from concave to convex or whatelse would characterize this curvature? I have seen something like this but wasn't sure about the meaning and will search for it.

It would be great, if you could clarify this question.

##### Share on other sites

I have posted my question in the sub forum "Relativity".

##### Share on other sites

I was wondering, like sound waves are vibrational waves of particles. How exactly are gravitational waves related. So are they vibrations of atoms ? and if so are they transverse or longitudinal vibrations ?

They are the distortions carried when matter will radiate. Needless to say, a large amount of time is required before matter will radiate away in the form of gravitational waves.

##### Share on other sites

1123581321, on 19 July 2011 - 03:00 PM, said:I was wondering, like sound waves are vibrational waves of particles. How exactly are gravitational waves related. So are they vibrations of atoms ? and if so are they transverse or longitudinal vibrations ?

They are the distortions carried when matter will radiate. Needless to say, a large amount of time is required before matter will radiate away in the form of gravitational waves.

Gravitational waves are transverse waves like electromagnetic waves (and water waves).

Matter will not be radiated away. A binary neutron star e.g. looses gravitational binding energy while emitting gravitational waves, which results in an orbital decay of the system. Finally the stars are coalescing due to the loss of angular momentum.

Edited by guenter
##### Share on other sites

Can you surf on gravitational waves?

##### Share on other sites

Of course matter will eventually radiate away in the form of gravitational waves. This is what Dyson worked out from his calculations. I will give you three examples of solutions to what will happen, there are more and will recite them all if you want.

Within $10^{19}$ the central region of the Galaxy may be expected to collapse into a Black Hole while stars in the outer region are detached from it.

After $10^{24}$ years, steller orbits around the Galaxy will decay into gravitational waves

After $10^{1500}$ years, all ordinary matter will have fissioned or fusioned to iron through radioactive processes.

That was to guenter, sorry^^

Edited by Mystery111
##### Share on other sites

How does static matter get radiated away as gravitational waves?

if after 10^19 years the centre has collapsed to a black hole and the outer region are no longer gravitationally bound then where do the gravitational waves come from?

10^1500 years - iron, seriously ? we will be in a warm radiation dominated universe by then - ie heat death, the big boring, dullsville tennessee .

##### Share on other sites

Of course matter will eventually radiate away in the form of gravitational waves.

Gravitational waves are not matter.

##### Share on other sites

Gravitational waves are not matter.

Given enough time, matter will radiate away, and all that will be left is graviational waves. Gravitational waves are non-trivial, they are a presence of curvature in the universe even when matter is not present.

The fact matter is predicted to radiate gravitational waves is an aspect predicted by dyson and his equations.

10^1500 years - iron, seriously ? we will be in a warm radiation dominated universe by then - ie heat death, the big boring, dullsville tennessee .

Actually I agree with this statement. This is what Dyson predicted.

stationary mass does not radiate wave's however. Only an acceletating mass will. I should have mentioned that.

Gravitational waves basically carry energy away from their sources.

''and in more detail in a 1918 paper, Einstein showed that when a mass accelerates – in other words, changes its state of motion – it can't help but give rise to time-varying gravitational fields that travel away from the source at light-speed as undulations in the surface of spacetime.''

http://www.daviddarling.info/encyclopedia/G/gravwave.html

Imaatfal

I think you have the concept of heat death wrong. It does not imply a warm radiated universe.

It means that the universe will cool down.

##### Share on other sites

Given enough time, matter will radiate away, and all that will be left is graviational waves. Gravitational waves are non-trivial, they are a presence of curvature in the universe even when matter is not present.

The fact matter is predicted to radiate gravitational waves is an aspect predicted by dyson and his equations.

"Matter radiates gravitational waves" is not the same as "matter will radiate away as gravitational waves" Where does the matter go? I have a bunch of quarks (in some form) and possibly leptons. And suddenly they aren't there?

##### Share on other sites

"Matter radiates gravitational waves" is not the same as "matter will radiate away as gravitational waves" Where does the matter go? I have a bunch of quarks (in some form) and possibly leptons. And suddenly they aren't there?

stop being pedantic. It is clear what I meant!

This reminds me of the time you corrected someone on the difference between mass and matter.

There is no need for it.

##### Share on other sites

stop being pedantic. It is clear what I meant!

This reminds me of the time you corrected someone on the difference between mass and matter.

There is no need for it.

The only thing that is clear is your propensity to pontificate on subjects about which you know absolutely nothing. In fact you know less than nothing as what you say is often wrong, but couched in buzz words designed to bamboozle neophytes.

Matter most certainly will not always radiate away as gravity waves. Were that the case there would be no such thing as a stable particle.

##### Share on other sites

stop being pedantic. It is clear what I meant!

This reminds me of the time you corrected someone on the difference between mass and matter.

There is no need for it.

No, it wasn't clear to me what you meant (you don't get to decide if it was clear to me, only I can decide that), and there is absolutely a need for it.

##### Share on other sites

The only thing that is clear is your propensity to pontificate on subjects about which you know absolutely nothing. In fact you know less than nothing as what you say is often wrong, but couched in buzz words designed to bamboozle neophytes.

Matter most certainly will not always radiate away as gravity waves. Were that the case there would be no such thing as a stable particle.

is that really true?

I mean, I did actually say I should have mentioned it was for accelerating objects, well before this post.

So if anyone is misrepresenting facts, it is you!

No, it wasn't clear to me what you meant (you don't get to decide if it was clear to me, only I can decide that), and there is absolutely a need for it.

Well, ... ok?

##### Share on other sites

is that really true?

I mean, I did actually say I should have mentioned it was for accelerating objects, well before this post.

So if anyone is misrepresenting facts, it is you!

Wrong,

##### Share on other sites

Matter most certainly will not always radiate away as gravity waves. Were that the case there would be no such thing as a stable particle.

In deed, the masses of the elementary particles are considered as physical constants.

Edited by guenter
##### Share on other sites

How could a particle decay into a gravitational wave? If matter can only be matter or energy, wouldn't that mean that gravity is energy?

Edited by questionposter
##### Share on other sites

This is a weird discussion in a physical forum. It is unphysical to expect matter being radiated away.

Should someone be interested in Physics, this is the right explanation,

The Hulse-Taylor pulsar

Take two big masses that are close together, whirl them around their common center of gravity at high speed, and general relativity is clear about what will happen. The orbital energy of the masses will gradually radiate away. They'll give off gravitational waves and, as they do so, their orbits will get smaller and smaller.

which coincides with my post #8.

##### Share on other sites

This is a weird discussion in a physical forum. It is unphysical to expect matter being radiated away.

Should someone be interested in Physics, this is the right explanation,

which coincides with my post #8.

So someone predicts that all matter will radiate it's energy away in the form of gravitational waves? But since matter can't travel at the speed of light, wouldn't the gravitational waves from all matter hit matter everywhere else and and thus matter and the universe would continue to have lots of energy? In fact, gravitational waves like that from supernova and things like neutron stars and black holes merging would even trigger the birth of stars in local gases and nebulae.

Edited by questionposter
##### Share on other sites

• 2 weeks later...

I heard something about this. That they were trying to detect residual gravity waves left over from the BB, or something to that effect, but have yet to detect them. Which brings up the question, do gravitational waves decay over time? Or does space have a counter effect on gravity? Not to suggest an opposite effect like dark energy, but just some sort of resistance. I'll try to find a link to where I saw that study. It was pretty interesting.

##### Share on other sites

I heard something about this. That they were trying to detect residual gravity waves left over from the BB, or something to that effect, but have yet to detect them. Which brings up the question, do gravitational waves decay over time? Or does space have a counter effect on gravity? Not to suggest an opposite effect like dark energy, but just some sort of resistance. I'll try to find a link to where I saw that study. It was pretty interesting.

Experiments to attempt to detect gravitational waves from ANY source have been underway since the 1970's, with incrreasing levels of sophistication and sensitivity. To date no gravitational waves have been directly detected.

The best evidence for gravitational waves, as predicted by general relativity, come from measurements of the orbital decay of binary star systems.

## Create an account

Register a new account

×

• #### Activity

×
• Create New...