speed of gravity
June 25, 2010 3:32 PM Subscribe
a "thought experiment" on gravity:
Pretend you could "teleport" a huge mass such as the sun into "empty outer space". How long would it take for the gravitational force to reach a distance such as the distance from the earth to the sun?
Most scientists assume that gravity travels at the speed of light.
posted by goblinbox at 3:37 PM on June 25, 2010
posted by goblinbox at 3:37 PM on June 25, 2010
We'll be able to test whether the speed of gravity is the speed of light when gravitational waves are detected from a source (e.g. a supernova) that also emits light.
posted by lukemeister at 3:47 PM on June 25, 2010
posted by lukemeister at 3:47 PM on June 25, 2010
Gravitons are the force-carrying particle of gravity (theoretically). Little buggers have no mass, so they don't interact with other atoms. Which means they're gonna be damn hard to find.
posted by zpousman at 5:51 PM on June 25, 2010
posted by zpousman at 5:51 PM on June 25, 2010
To answer directly, 8.5 minutes.
posted by intermod at 7:39 PM on June 25, 2010 [1 favorite]
posted by intermod at 7:39 PM on June 25, 2010 [1 favorite]
Best answer: I read a BRIEF synopsis once for research that argued that mass is an emergent property of quantum entanglement and that, if this is true, there is no speed of gravity, it just is. Everywhere at the same time. I have no idea how they came at this and a quick Google search reveals that there are a lot of people who don't get that no matter how cool a science fiction computer game might be, you can just decide that's how the universe works.
posted by Kid Charlemagne at 8:01 PM on June 25, 2010
posted by Kid Charlemagne at 8:01 PM on June 25, 2010
Grrrr. Can't! No matter how cool the game you can't just decide that's how the universe works.
posted by Kid Charlemagne at 8:06 PM on June 25, 2010
posted by Kid Charlemagne at 8:06 PM on June 25, 2010
"Little buggers have no mass, so they don't interact with other atoms. Which means they're gonna be damn hard to find."
It's not their mass(lessness) that makes them hard to find - after all, photons are massless and they're pretty easy to detect.
And of course they do interact with other things - they have to interact with everything, because gravity acts on everything.
posted by edd at 3:10 AM on June 26, 2010
It's not their mass(lessness) that makes them hard to find - after all, photons are massless and they're pretty easy to detect.
And of course they do interact with other things - they have to interact with everything, because gravity acts on everything.
posted by edd at 3:10 AM on June 26, 2010
Gravity waves are hard to detect because the gravitational force is so much weaker than other forces, not because gravitons are massless. Also because there's lots of other stuff nearby going on; if you build an experiment on the earth there are earthquakes and trucks and weather changes and oof. (That's why LISA is going to be in space).
After all, photons are massless and we can detect them just fine (even with just our own eyeballs).
And yeah, gravity's busy keeping me on the earth right now, but it is weaker; you don't need a terribly strong magnet to hold a nail up against the pull of gravity, and it's the whole earth that's busy trying to pull the nail down.
posted by nat at 3:19 AM on June 26, 2010 [2 favorites]
After all, photons are massless and we can detect them just fine (even with just our own eyeballs).
And yeah, gravity's busy keeping me on the earth right now, but it is weaker; you don't need a terribly strong magnet to hold a nail up against the pull of gravity, and it's the whole earth that's busy trying to pull the nail down.
posted by nat at 3:19 AM on June 26, 2010 [2 favorites]
Ack, should have previewed, sorry edd. Yeah, if you're thinking of something that's hard to detect because it interacts weakly with other stuff, you're (probably) thinking of neutrinos.
posted by nat at 3:20 AM on June 26, 2010
posted by nat at 3:20 AM on June 26, 2010
There's also a subtle difference between detecting gravitational waves* and detecting gravitons.
Wikipedia explains a bit - detecting an individual graviton requires absurdly large detectors (as in the size of a large planet) in very special circumstances. We'll have to demonstrate their existence in a less direct fashion.
*we have to avoid the term gravity wave as that's already used for something else
posted by edd at 4:09 AM on June 26, 2010
Wikipedia explains a bit - detecting an individual graviton requires absurdly large detectors (as in the size of a large planet) in very special circumstances. We'll have to demonstrate their existence in a less direct fashion.
*we have to avoid the term gravity wave as that's already used for something else
posted by edd at 4:09 AM on June 26, 2010
This thread is closed to new comments.
posted by axiom at 3:36 PM on June 25, 2010 [1 favorite]