1. Dec 18, 2005

### Suedeos

hey all, I'm pretty new to physics. all I know is what I was taught at secondary school, which wasn't much to be honest..

sorry if this is a stupid question or in the wrong place or whatever, feel free to move/delete it if it is..

so what I'm wondering about is gravitons. I know as good as nothing about them, but what I do know makes me interested. VERY interested..

could someone please explain to me what a graviton is, and why scientists can't 'create' one for long enough to observe or study it please?

also, if any moderators/admins read this, could you change my name to Suede please, I accidentally added the 'os' to the end. and 'Suedeos' isn't even gramatically correct. thanks :)

2. Dec 18, 2005

### pervect

Staff Emeritus
A graviton would be a quantized packet of gravitational radiation, much like a photon is a quantized packet of electromagnetic radiation.

I'm not sure why you are interested in gravitions - basically, at the current moment in time, we are looking for gravitational radiation (which I find interesting).

After we find that gravitational radiation exists (assuming that we do - our most sensitive instruments are currently not sensitive enough, though we expect that Ligo will start to achieve some reults when it is upgraded) we can start worrying about whether or not this radiation comes in small packets (quanta) like photons. Because gravitational radiation is so weak, detecting a single quanta of it will likely not be possible in our lifetimes, so the question will most likely be totally theoretical.

Note that "gravitions" will most likely not have any applications for "anti-gravity", if by some chance that is why you were interested in them. The relationship of gravitions to gravity is the relations of photons to electromagnetism. The columb force between two particles is due to their charge, and while we can generate photons by shaking a charge around rapidly enough, we cannot increase or decrease the attractive force between unlike charges by generating photons.

Similarly, the gravitational "force" between two particles is due to their mass(actually, their energy to be more precise) - and while gravitational waves can in theory be generated by violent enough events (such as inspiralling neutron stars), they will not increase or decrease the attractive forces between different masses.

3. Dec 18, 2005

### Mk

Laser Interferometer Gravitational-Wave Observatory, LIGO, is two big machines, one in Louisiana, and one in Washington state that work together to try and detect gravitational waves.

Also, an interesting thing you can do to help the project, is sign up for Einstein@Home, it sort of uses your computer (when you're not) to crunch all the numbers they get, to see if they detected any gravitational waves.

Last edited: Dec 18, 2005
4. Dec 18, 2005

### Mk

You can post a thread in the feedback section, or better yet, PM the Administrator yourself (better).

5. Dec 19, 2005

### Suedeos

*n00b question*

is that the big machines that fire particles in a huge underground tunnel thing? or am I going mad?

6. Dec 19, 2005

### ZapperZ

Staff Emeritus

Notice that the description is a "laser interferometer". Any gravitational waves hitting the earth would cause a shift in the interference pattern (a naive description of how LIGO works).

The "big machines that fire particles in a huge underground tunnel thing" is a particle accelerator/collider. Not meant for detecting gravitational waves.

Zz.

7. Dec 19, 2005

### ahrkron

Staff Emeritus
Basically, an interferometer is shaped as an "L". From each end, a laser is shot towards the corner, where the combination of the two beams produces an image called an "interference pattern".

When a gravitational wave reaches the interferometer, it makes one of the legs of the "L" longer than it was, hence distorting the interference pattern. Using the distortion, it is possible to measure how space itself was modified by the wave.

Actually, the wave makes one leg longer and the other shorter, and then the other way around.

8. Dec 21, 2005

### Suedeos

where do you guys get all this information from?!

I find all this stuff really interesting, even though I'm a total noob at this stuff :D

9. Jan 13, 2006

### Scottbob

All this stuff they've explained is standard university material, but too hard to cram into kids' heads at school.

Its good to know that non-physics people find it interesting when they are presented with top-end physics and think about it for a while! It makes me proud to be studying physics at uni!

10. Jan 25, 2006

### jhmar

pervect
A graviton would be a quantized packet of gravitational radiation, much like a photon is a quantized packet of electromagnetic radiation.

I have always considered a graviton to be a fundamental particle in its own group in the same manner as quarks and leptons and not a boson as indicated in the above statement. Can you please explain why the graviton is considered to be a member of the boson group (i.e. not a separate group on its own, such as boson, quark or lepton).