# Gravitational Waves

1. Jul 12, 2007

### vs_cygnus

How do gravitational waves originate?
Does the mass of the body, from where they are originating,decrease?

2. Jul 12, 2007

### Janus

Staff Emeritus
Gravitational waves originate in much the same way as electromagnetic waves do. If you accelerate an electric charge, like an electron, it will produce an electromagnetic wave. The energy for this wave comes from the kinetic energy of the electron.

In the same way, if you accelerate a mass, it will emit a gravitational wave, and the energy for that wave will come from the masses kinetic energy.
In fact, since the above electron also has a mass, it will emit gravitational waves as well as electromagnetic ones. Gravitational waves however are very very weak and the electromagnetic waves account for the vast majority of the lost kinetic energy.

3. Jul 12, 2007

### rbj

isn't the kinetic energy something that is dependent upon reference frame? if so, do we mean that the energy for the gravitational or E&M wave comes from the reduced kinetic energy of the decellerated body (with mass and charge) with respect to the frame of reference of the observer measuring the wave? but then, what about if (in my frame of reference) the body is accelerated to a higher speed? doesn't it still emit a gravitational (or EM) wave due to that acceleration? where does the energy come from for both the wave and for the increased kinetic energy of the body?

4. Jul 13, 2007

### Voltage

Are gravitational waves speculative rather than something taken as fact?

5. Jul 18, 2007

### mgb_phys

In physics there is no difference

I don't think they have been conclusively detected yet but there are a number of new gravitational wave detectors coming on line.
They are predicted by GR and don't cause any real problems in any other theory so are quite likely to be 'real'.

6. Jul 18, 2007

### George Jones

Staff Emeritus
Last edited by a moderator: Apr 22, 2017
7. Aug 3, 2007

### MarkeD

I believe string theory also predicts their occurance, a massless particle with spin=2 spoken of in this article

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