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The Speed Of Gravity Revealed

timothy posted more than 11 years ago | from the blink-and-you'll-miss-it dept.

Science 935

redwolfoz writes "New Scientist is reporting that the speed of gravity has been measured for the first time. 'The landmark experiment shows that it travels at the speed of light, meaning that Einstein's general theory of relativity has passed another test with flying colours.' Researchers made the measurement of the fundamental physical constant with the help of the planet Jupiter. One important consequence of the result is that it will help constrain the number of possible dimensions in the Universe."

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935 comments

FP! (-1, Offtopic)

Anonymous Coward | more than 11 years ago | (#5036675)

FIRST POST! WOOOOOOOOOT! I'd like to dedicate this to all the people who believed I could do this again. Stupid as it may be.

IN SOVIET RUSSIA.... (-1, Troll)

Anonymous Coward | more than 11 years ago | (#5036676)

IN SOVIET RUSSIA.... speed of gravity reveals YOU!

Gravity (-1, Offtopic)

Anonymous Coward | more than 11 years ago | (#5036679)

This first post post will gravitate down in moderation.

gotta love the first post ackshun. (-1, Offtopic)

Anonymous Coward | more than 11 years ago | (#5036680)

wh00t...i think?

FGP (-1, Offtopic)

Anonymous Coward | more than 11 years ago | (#5036682)

First Gravitational Post!!!

Wow. (5, Funny)

Skyshadow (508) | more than 11 years ago | (#5036688)

Wow, that's pretty cool. Now if we could only figure out why and how gravity works, we'd be in business.

Re:Wow. (5, Funny)

56 (527333) | more than 11 years ago | (#5036704)

Gravity works because we believe in it. Just stop believing in it and it will stop working.

Not working? You must not be trying hard enough.

Re:Wow. (3, Funny)

grammar fascist (239789) | more than 11 years ago | (#5036798)

Gravity works because we believe in it. Just stop believing in it and it will stop working.

I've had good luck so far just not looking down, and not reading the sign.

Re:Wow. (2, Funny)

Evil Adrian (253301) | more than 11 years ago | (#5036725)

The order of universal forces, from strongest to weakest, is Electomagnetic, Strong, Weak, and Gravitational. So gravity, you see, is the weakest force in the universe.

Try telling Sonny Bono that.

Re:Wow. (4, Funny)

Anonymous Coward | more than 11 years ago | (#5036770)

Try telling Sonny Bono that.

Or Pamela Anderson, for that matter.

Re:Wow. (3, Informative)

lommer (566164) | more than 11 years ago | (#5036816)

Well, actually that's not actually true, depending on how you define weak (the adjective). Gravity exerts the smallest force, but it does so over the greatest distances. OTOH, Electromagnetic forces are very powerful, but only over short distances. The nuclear strong and weak forces fall in the middle accordingly.

Re:Wow. (3, Informative)

oateater (593228) | more than 11 years ago | (#5036891)

If I am not mistaken, nuclear weak force is fairly rare, compared to the others. I always thought nuclear strong was the strongest, electromagnetic 2nd, then weak, then gravity. "Gravity is not a force, it is a product of space and time" I love physics, and am considering doing physics in college.

Re:Wow. (5, Informative)

GuyMannDude (574364) | more than 11 years ago | (#5036811)

Yeah, that's the real trick. For those who aren't aware, getting gravity to "play nice" with both general relativity and quantum mechanics is pretty tough. Relativity models gravity is a warping of space. But coming up with a quantum theory of gravity is mighty difficult. There are theories that gravity acts through particles (the so-called gravitons you always hear about on ST:TNG) but I don't believe this has been proven yet.

GMD

Re:Wow. (3, Informative)

silvaran (214334) | more than 11 years ago | (#5036820)

Stephen Hawking's A Brief History of Time describes it as a series of virtual particles emitted by all matter. They're spin 1 particles (I think - whatever that means). Something about how many times you have to rotate the particle to get back to the same perspective as when you started. Like spin 2 particles, you turn them around 1/2 revolution and you're back to where you started. Spin 1 particles need to be rotated all the way around once. Spin 0 particles look the same in every direction. Spin 1/2 particles (which matter is made up of) have to be rotated twice to get back to the same position. They're called virtual particles because they can't be directly seen.

Anyways, since gravity is made up of particles, it follows the same rules as all other particles, and thus can't go any faster than the speed of light.

IN SOVIET RUSSIA (-1, Troll)

Anonymous Coward | more than 11 years ago | (#5036692)

In Soviet Russia, the number of possible dimensions in the universe constrains YOU!!!

The gravity of the discovery (1)

Gortbusters.org (637314) | more than 11 years ago | (#5036700)

is enormous!

Seriously, one of my favorite things from school used to be the concepts of gravity, and even the forces holding molecules together.

Re:The gravity of the discovery (-1, Troll)

Anonymous Coward | more than 11 years ago | (#5036851)

The gravity of the discovery [...] is enormous!
I hate your soul.

(And to think, I'll be labeled a troll for this, well, as least I can be sure you won't be breeding any time soon)

Flying Colours (5, Funny)

EuroChild (523969) | more than 11 years ago | (#5036701)

But of course, travelling at the speed of light, all the flying colours just appeared red due to the red-shift.

Event Horizon (3, Interesting)

Jetson (176002) | more than 11 years ago | (#5036720)

Well, if gravity travels at the speed of light, wouldn't the gravitational pull of black holes be confined by the event horizon as is the case with light?

Re:Event Horizon (3, Interesting)

adpowers (153922) | more than 11 years ago | (#5036742)

I don't think so. Light has mass which allows it to be pulled into the black hole while gravity doesn't have mass.

Re:Event Horizon (1)

Evil Adrian (253301) | more than 11 years ago | (#5036761)

Are you sure about that? I'm no astrophysicist, but as far as I can tell practically everything has mass, even things (light) which we thought didn't.

Re:Event Horizon (5, Informative)

DrMegaVolt (560884) | more than 11 years ago | (#5036772)

Light has mass? no it does not.. the energy of a photon has a mass equivalence, but it does not have mass.

Re:Event Horizon (2)

Alex Thorpe (575736) | more than 11 years ago | (#5036782)

Question: if gravity is without mass, how does it affect things that do have mass, as it obviously does?

Re:Event Horizon (5, Insightful)

Chris Burke (6130) | more than 11 years ago | (#5036874)

The same way an electric field doesn't have a charge, but affects objects that do have a charge. Gravitational/electric fields are -created- by masses/charges. And don't confuse gravity with gravity waves (the speed of which being what are measured here).

By the way, did anyone else find the quoted margin of error of .25 to be kinda ridiculous? So based on their measurements, the speed of gravity could actually be anywhere from 30% slower to 20% faster than light. I mean, the article makes it sound like they're just assuming the real number is 1.0 c because anything else would be really surprising. Or maybe the article is wrong. Or I'm mis-reading it. But at the moment, it doesn't sound like "passing with flying colors" to me.

Re:Event Horizon (1)

jbrandon (603700) | more than 11 years ago | (#5036822)

Arg! Light has no mass. It travels at the speed of light, so if it had mass, it would have infinite energy as well.

Re:Event Horizon (0)

Anonymous Coward | more than 11 years ago | (#5036841)

i seem to remember from chemistry, light can be explained in two ways. the wave/particle duality..

not quite right (1, Informative)

Anonymous Coward | more than 11 years ago | (#5036846)

light does not have mass. you may be thinking of momentum, which it does have... general relativity says that the path of light (at least as far as the light is concerned) is not really bent, but space-time is bent toward massive objects. the light just follows the straightest path it can, but in a black hole space is curled up so much that the light ends up getting trapped. to just say gravity doesnt have mass so it cant be pulled into a black hole isn't enough. because after all neither does light! you could see that since the space which gravity acts on does not appear to be bent (as far as we can see) then perhaps its path depends on another property of space-time.

Re:not quite right (1)

DrMegaVolt (560884) | more than 11 years ago | (#5036884)

Why would it be the same as light, if it depends on a different property of space-time as you suggest? Also, it would be interesting to see if the speed of gravity were invariant, like light.

Re:Event Horizon (1, Interesting)

lommer (566164) | more than 11 years ago | (#5036864)

Light (in the form of photons) has mass. The only reason that gravity "doesn't" have mass is that we have yet to find a particle form of it (i.e. a graviton). If this were ever discovered, gravity would then have mass. It would also lend convenient symmetry to the universe as we have force-carrying particles for the other 3 universal forces (electromagnetic (light), strong nuclear and weak nuclear). I personally think that we will someday discover a graviton.

100% wrong. (3, Informative)

rebelcool (247749) | more than 11 years ago | (#5036867)

Here's a good explanation [nasa.gov]

Photons are not particles in the sense of neutrons, electrons et. al which are massy particles.

Photons are better described as 'packets of energy'. Gravity doesn't just affect mass - it affects energy as well. Light doesnt get 'pulled into' a black hole, it just gets redshifted so much (by the gravity sucking the energy out of it), that its wavelength becomes infinite, and thus immeasureable.

Photons can exert a pressure though because they have MOMENTUM. Thus they have a 'mass equivalent', but they do not have mass, and that is not why they cannot escape black holes.

Re:Event Horizon (5, Informative)

mcc (14761) | more than 11 years ago | (#5036892)

Um, no. This is one of the main points of the theory of relativity.

Light does not have mass. This is why it is capable of travelling at the speed of light-- it is impossible for anything with mass to travel at the speed of light. The reason light can get pulled into a black hole is becuase an object with gravity warps the space around it-- the more mass you have, the more that you warp space. When light gets "pulled into" a black hole, the light is in fact moving in a straight line-- it's just that space is curved in the vicinity of the black hole, so if you travel straight forward you will get pulled into the black hole.

Think of it like you've got a matress, and you have something very heavy sitting on the matress, and the matress is kind of indented in the area of the heavy object. Now imagine if you take a marble, and roll it in a straight line toward the dent the heavy object makes. It will go in a straight line, then when it enters the dent it will start kind of curving around the inside of the dent. The standard metaphor is that gravity works like that, light is like the marble moving in a straight line, but its path is being "bent" by the curvature of space. A "black hole" is an object so heavy it's managed to tear through the fabric of the matress, meaning it's impossible for anything that's fallen into its area to roll back out.

I will let my rudimentary explanation stand until someone who's actually studied relativity can fill in whatever gaps i've left.

Re:Event Horizon (0)

Anonymous Coward | more than 11 years ago | (#5036755)

Ooh, good challenge...

Re:Flying Colours (0)

Anonymous Coward | more than 11 years ago | (#5036726)

Actually, if flying away from you, you wouldn't see anything (The light wouldn't reach you) If it was flying toward you, you would see it just as is smashed into you.

The only thing you see *are* those that smash you (0)

Anonymous Coward | more than 11 years ago | (#5036894)

If it no smash, you no see flash!

Sorry if i'm Skeptical (2, Insightful)

Anonymous Coward | more than 11 years ago | (#5036707)

"Einstein wins yet again." He adds that any other result would have come as a shock.

If you already know the answer you are looking for it's a lot easier to "tug and pull" the numbers.

Re:Sorry if i'm Skeptical (3, Insightful)

exp(pi*sqrt(163)) (613870) | more than 11 years ago | (#5036803)

And when you don't know what you're talking about it's easy to just mouth off. Did you read the paper to see what's going on? Maybe there are some details in the experiment you'd actually like to criticize constructively?

Re:Sorry if i'm Skeptical (0)

Anonymous Coward | more than 11 years ago | (#5036875)

Actually I did read the paper before posting. It says that the overwhelming scientist support is behind Einstein's answer. If it is the speed of gravity then hip hip hooray. But if 10 years from now somebody "updates" this scientific theory you'll just have this msg saying Told You So.

Re:Sorry if i'm Skeptical (4, Funny)

stratjakt (596332) | more than 11 years ago | (#5036819)

You're right!

It's all a big scam. I bet George W Bush and the DMCA are behind it, having been bought by Microsoft!

Uh-oh (4, Funny)

Saint Aardvark (159009) | more than 11 years ago | (#5036712)

I've got a 3-year old goddaughter who is just gonna cry when I explain to her why, in real life, the coyote would get the road runner.

Cartoon Physics and Gravity (2)

jimmcq (88033) | more than 11 years ago | (#5036842)

I've got a 3-year old goddaughter who is just gonna cry when I explain to her why, in real life, the coyote would get the road runner.

The coyote and road runner have their own Laws of Physics [physicsweb.org] to contend with.

Practical Applications (5, Funny)

handy_vandal (606174) | more than 11 years ago | (#5036713)

Sure, this experiment will "help constrain the number of possible dimensions in the Universe" ... but will it lead to new weapons?

Re:Practical Applications (2, Funny)

56 (527333) | more than 11 years ago | (#5036728)

Well, we can now pull Saddam out of Iraq at the speed of light, all we need is a gravity generator.

Ideas, anyone?

Re:Practical Applications (0)

Anonymous Coward | more than 11 years ago | (#5036748)

If there were any reason too, perhaps, but so far the weapons inspectors have found dick. So basically, Bush is beating his daddy's war drum, not his own.

Re:Practical Applications (0)

bucephalis (165674) | more than 11 years ago | (#5036769)

"so far the weapons inspectors have found dick"

They were supposed to find weapons....

Re:Practical Applications (1)

56 (527333) | more than 11 years ago | (#5036775)

I was being sarcastic, Bush wants this war for three reasons.

1. Revenge. Lil' Bush wants to get big ol' Saddam because he threatened to kill Big Daddy Bush. 2. Oil. Bush is probably soaking in it as we speak. Have you noticed the preponderance of 'if you do drugs you support terrorism,' and the lack of 'if you buy oil you support terrorism?' 3. Distraction. Think sputtering economy, failure to kill bin Laden, the number of Enron 'advisors' in the Bush white house, and the plain and simple fact that Bush is about as smart as lettuce. Without the photosynthesis.

Re:Practical Applications (0)

Anonymous Coward | more than 11 years ago | (#5036827)

4. War is good for the economy.

Gravity Weapon: Wide-Spread Effect (2, Funny)

handy_vandal (606174) | more than 11 years ago | (#5036848)

Sure, we could pull Saddam out of Iraq with a gravity generator ... pull out the Tigris and Euphrates, while we're at it -- the whole damned Cradle of Civilization.

Re:Practical Applications (-1, Flamebait)

Alan Partridge (516639) | more than 11 years ago | (#5036736)

if Americans have got anything to do with it - unfortunately it won't lead to much else.

Re:Practical Applications (1, Offtopic)

RazzleDazzle (442937) | more than 11 years ago | (#5036813)

Almost. If the American GOVERNMENT has anything to do with it. The people and scientists are not on the whole evil and destructive like our government is.

Now if George Bush were in a position to decide the direction this discovery should take, what would he decide?

1) Destroying all who oppose us, us meaning the US Government.
2) Enhancing propulsion for space travel or some other cool space/(astro)phyics/other science related direction.
3) Get another 3 miles/gallon for SUVs

Cowardly for a reason! (5, Interesting)

Anonymous Coward | more than 11 years ago | (#5036714)

I'm sorry, I don't mean to ask the stupidest question ever, but how does gravity have speed? The last I was taught on the subject (and believe me, it was a while ago) was that gravity was a force, but didn't have mass. Doesn't something need to have mass in order to have speed?

How about light, numbnutz? (nt) (-1, Flamebait)

Anonymous Coward | more than 11 years ago | (#5036737)

N/T

Re:Cowardly for a reason! (1)

akheron01 (637033) | more than 11 years ago | (#5036751)

Well, light is massless yet photons have a definite speed.

Re:Cowardly for a reason! (1)

gekman (224336) | more than 11 years ago | (#5036781)

I thought that photons do have mass, just VERY little of it.

Re:Cowardly for a reason! (1)

Captain Nitpick (16515) | more than 11 years ago | (#5036893)

I thought that photons do have mass, just VERY little of it.

Photons have no mass. They have energy, which can be considered equivalent to a tiny mass in many situations.

That's Newtonain Physics (5, Informative)

GuyMannDude (574364) | more than 11 years ago | (#5036777)

You're confusion arises because you were taught elementary Newtonian physics. In general relativity, one learns that any "information" cannot travel faster than light. Gravity is considered information because if you feel a gravitational force on you, you know that there is a body out there acting on you. That is, you have information about it (you could even estimate its mass by measuring the tug it exerts on you).

In Newtonian physics, lots of things are assumed to happen instantaneously (like gravity) so they don't have a speed per se. But in general relativity, everything has a speed -- and that speed is no greater than the speed of light.

GMD

I get it now, maybe I can re-explain again (0)

Anonymous Coward | more than 11 years ago | (#5036799)

Before the speed of light, everyone thought light was instantaneous. That is, when you turn on the lights in your room, theres actually an amount of time before the light from the light bulb reaches your eyes.

In the same way, if you suddenly created mass (ok this is impossible). It would take the same ammount of time for it to be attrached from another body... pretty zany.

to be pedantic (0)

Anonymous Coward | more than 11 years ago | (#5036847)

The lion's share of the delay between the production of the actual photons and your perception of them is in your nervous system.

Re:Cowardly for a reason! (0)

Anonymous Coward | more than 11 years ago | (#5036797)

gravity doesn't seem to have speed when your constantly under the influence of it like we are.

But it really takes time for the pull of the earth to reach us. Nothing is transmitted for free.

Imagine a big Sun pops into our Solar system, now the earth will see it when it's light reaches us and we will feel it's gravity when the gravitational waves reach us.

hope that helps.

Re:Cowardly for a reason! (2, Informative)

Grieveq (589084) | more than 11 years ago | (#5036800)

The example they provide is a good logical one. If the sun was removed from the solar system by some magical means, we wouldn't feel it (or see it) for another 8 minutes.

Re:Cowardly for a reason! (1)

Morphine007 (207082) | more than 11 years ago | (#5036835)

The last I was taught on the subject (and believe me, it was a while ago) was that gravity was a force, but didn't have mass.

gravity is a force... the speed that is being talked about is this:

if a large object were to suddenly materialize 1 light hour away from you, how long would it take before you felt the effects of it's gravitational 'pull' .... the answer is 1 hour... or .95 of an hour if previous posts are correct... I dunno... I didn't RTFA... in any event, that's the "speed of gravity"

New discoveries (1)

gnixdep (629913) | more than 11 years ago | (#5036715)

These are exciting times, we learn more and more about the fundimental nature of our universe, understanding more about our selves in the process.

Next, I propose we search for the speed of SMART, and find some way we can control it's direction.

THAT will be a great breakthrough for humanity.

Re:New discoveries (0)

Anonymous Coward | more than 11 years ago | (#5036779)

We understand so much, yet we "our selves" still can't spell "fundimental" words.

I'd expect... (5, Interesting)

Masami Eiri (617825) | more than 11 years ago | (#5036722)

...a topic like this to be a bit more precise in the summary. There's a signifigant difference between .95 times the speed of light, and the speed of light. Not to mention the large .25 margin of error. Which theoretically shouldn't be able to get to +.25 anyhow.

Re:I'd expect... (2, Insightful)

Anonymous Coward | more than 11 years ago | (#5036784)

I think a more precise conclusion is "this is consistant with gravity propagating at c." You can't prove gravity propagates exactly at c, you can only ever prove the difference between the speeds is arbitrarily small. Alternatively, they could prove that the speed of gravity != c, which they haven't done either. To do that, the measured speed plus the error bar would need to be less than c.

Re:I'd expect... (1)

Evil Adrian (253301) | more than 11 years ago | (#5036788)

Well, it is the first time it's been measured. I'm sure that they'll refine the experiment and continue to study the subject; I'd say though, at first look, getting .95 is pretty fn close (and, as the poster states, is in holding with the theory of relativity) so it can't exactly be discarded. The worst that can happen is a later experiment will say "well, we were wrong."

Re:I'd expect... (1)

Captain Nitpick (16515) | more than 11 years ago | (#5036873)

here's a signifigant difference between .95 times the speed of light, and the speed of light.

The difference between 1.00 and 0.95 is significant.

The difference between 1.00 and 0.95 (plus or minus) 0.25 is not.

(My browser doesn't seem to be rendering the ± entity)

Wow, what a discovery! (0)

Anonymous Coward | more than 11 years ago | (#5036723)

Man, that's heavy!!!

Someone's a little jealous... (1)

Moskie (620227) | more than 11 years ago | (#5036729)

"It would be revolutionary if gravity were measured not to propagate at the speed of light - we were virtually certain that it must," says Lawrence Krauss of Case Western Reserve University in Cleveland, Ohio.

For the wish-I-thought-of-this-first department.

Speed of light? (4, Funny)

grub (11606) | more than 11 years ago | (#5036741)


When I fall down drunk I never thought I was moving that fast.

Deriving e=mc^2 (4, Informative)

sQuEeDeN (565589) | more than 11 years ago | (#5036743)

It turns out you can derive e = mc^2 with very little effort. All it takes is a spot of calculus and a bit of relativity. All you need to know is that Work = delta KE and that mass is really m0 / (1-v^2/c^2)^.5, something previous physicists had derived.

Since work is the integral of dMomentum / dt with respect to dx, you can mux that around to get, eventually, Ke = (the mass formula)*c^2 - m0 * c^2.
What einstein said that was amazingly brilliant is that the equation fits Total E = KE + PE. He called that bit with the mass formula Total E, so therefore m0*c^2 = PE!! HA!, you are a smart as Einstein now!! (just kidding)

Re:Deriving e=mc^2 (0)

Anonymous Coward | more than 11 years ago | (#5036883)

Wrong. What a stupid way to "derive" E=mc^2. Read a real physics book

gravity slowing down? (3, Insightful)

petsounds (593538) | more than 11 years ago | (#5036752)

If the speed of light is slowing down [slashdot.org], then is the speed of gravity also slowing?

Re:gravity slowing down? (3, Interesting)

3seas (184403) | more than 11 years ago | (#5036810)

The speed of Light is not slowing down but rather we are moving faster and our method of measure is relative to us, not to light.

In other words.... when we finally manage to reach the speed of light we will also, as a by-product, figured out antigravity...

History? A matter of how fast you are moving relative to the speed of light.

Time is relative to Speed.

Re:gravity slowing down? (1)

bje2 (533276) | more than 11 years ago | (#5036837)

damn, the speed of gravity is slowing down...and i thought i was actually losing weight...

Re:gravity slowing down? (2)

silvaran (214334) | more than 11 years ago | (#5036860)

Likely, at least that's my guess. I'm no expert, but light, space and time are all related. So if light slows down, or time speeds up, and nothing can go faster than the speed of light, than anything that travels at the speed of light (like gravity) will slow down as well.

Obligatory cultural reference... (1)

squireofgothos (310804) | more than 11 years ago | (#5036754)

Woah, Doc... Not only is this heavy, it's really fast!

In other news, having been clocked going at .95c Gravity was subsequently pulled over for speeding... Details at 11.

Seriously though, that's pretty cool...

Actually there is something faster than light... (5, Funny)

beej (82035) | more than 11 years ago | (#5036764)

"One of the problems has to do with the speed of light and the difficulties involved in trying to exceed it. You can't. Nothing travels faster than the speed of light with the possible exception of bad news, which obeys its own special laws. The Hingefreel people of Arkintoofle Minor did try to build spaceships that were powered by bad news but they didn't work particularly well and were so extremely unwelcome whenever they arrived anywhere that there wasn't really any point in being there."

--Douglas Adams, Mostly Harmless

Re:Actually there is something faster than light.. (1)

certron (57841) | more than 11 years ago | (#5036852)

The Speed of Lint!

"We have to get faster. What is faster than light speed?? The speed of lint. what?? The speed of lint. What is the first thing you find in your pants in the morning. I dont know. Lint, and how does it get there? I don't know?? It's that fast." -The Tick

http://www.thetick.ws/car24.html

http://www.cs.rose-hulman.edu/~stinerkt/tickdocs /s cwhat.html

a request (2)

RelliK (4466) | more than 11 years ago | (#5036885)

Ahh, I *love* The Hitchhiker's series, but I don't own a copy. Could somebody please post my favourite passage from the first book: using the babelfish to prove the non-existance of God.

Bonus points to anyone who also posts the one about a cow that wants to be eaten, just to see the vegetarians' reaction :-)

Thanks.

Does this mean... (1, Interesting)

Anonymous Coward | more than 11 years ago | (#5036785)

That if you were able to travel at the speed light that gravity would also cease to exist?
Is gravity has a speed then theoretically we can outrun it

huh? (0)

Anonymous Coward | more than 11 years ago | (#5036806)

thought antigravity was in effect till puberty then gravity kicked it at a quarter inch or so per year, faster after pregnancies.


Posted anonymously to protect my reputation.

Hmm. (0)

Anonymous Coward | more than 11 years ago | (#5036830)

So my FTL communications gear that was going to be based upon rapidly changing a large mass back and forth between energy and matter won't actually be any faster then my flashlight. Interestingly enough, their results had a rather large error margin of 25% while the result they actually calculated was only 95% of the speed of light or ~285000 m s^-1 +/- 75000 m s^-1 This is a good example of why they make you do all those painfull error calculations in university physics, they really are usefull.

I find this incredibly interesting, if gravity is not instantaneous, then this discovery probably aids in some manner the particle/wave advocates. It is also strange to think that when you are looking at the night sky the stars you see the light from might not exist anymore, but the echos of there gravity are still pulling on you. Could this be usefull to astonomers/astrophysicists? They could build detectors to measure minute change in gravity and then use these devices to corroborate light based data.

The whole idea of gravity emmenating from a source and travelling out causes me considerable consternation.

Suppose you have a planet A and a meteor B
A -B
and that B is being drawn in towards A.
If A spontaneously stops existing (yes it's rediculous, but the ridiculous often appears when posing problems) then B has until the gravity from A arrives at the point where B was before it stops accelerating because as we know combined approach velocities may not exceed c. But, at the same time that seems to indicate that B is accelerating longer then it should

Bah, gravity gives me a headache. Even when I don't fall down. Goodnight.

Doesn't this go against Einstein's Theories? (2, Informative)

kakos (610660) | more than 11 years ago | (#5036833)

I thought Einsteinian gravity was a warp in space-time due to the displacement of objects of mass. That would mean gravity is instantaneous, wouldn't it?

However, String Theory predict the existence of a gravity carrier particle called the graviton. It seems it lends more credence to that theory, since, if gravity is travelling at the speed of light, it seems like it would be a particle.

Has science gone mad? (4, Interesting)

j3110 (193209) | more than 11 years ago | (#5036839)

"Kopeikin found another way. He reworked the equations of general relativity to express the gravitational field of a moving body in terms of its mass, velocity and the speed of gravity. If you could measure the gravitational field of Jupiter, while knowing its mass and velocity, you could work out the speed of gravity."

The theory of relativity was appearantly used to detect the speed of gravity. This would be fine if the theory of relativity didn't assume a speed of gravity. Basically, all he did was prove his given. So, if eggs are green, then eggs are green!

Theory of Relativity.... (2, Insightful)

MasterSLATE (638125) | more than 11 years ago | (#5036840)

Well, this says that Einstein's theory of relativity passed another test with flying colours.. but... According to THIS [slashdot.org] previous article on /. (and the NYT), the theory of relativity is generally flawed, so then did they really find the speed of gravity?
I'm confused...

another dumb question (1, Interesting)

Anonymous Coward | more than 11 years ago | (#5036850)

The article says that the discoverer used a reworking of an equation from general relativity and plugged in the mass and velocity of Jupiter to measure the speed of gravity. He ended up getting a result consistent with the predictions of general relativity. Am I missing something, or is this circular reasoning? IOW - Isn't this the same as saying: "Assuming A is true, I've proven B -- a result which lends credence to A!" There's something major I'm missing, so I apologize in advance for being an idiot and wasting our precious oxygen by sustaining myself.

Utter Bullshi-ite. (2, Interesting)

Derling Whirvish (636322) | more than 11 years ago | (#5036855)

Gravity has speed?

If this theory of gravitiational propagation is true then gravity would have to exhibit doppler effects. The force of gravity would be stronger and act at a shorter distance towards the velocity vector of an object and conversely it would be weaker and act at a greater distance in the opposite direction in violation of the inverse square rule for gravitational effects. This has not been noted in any observations. All present observations of moving astronomical objects moving at anywhere near to relativistic speeds, or even those moving much slower taken as a statistical whole, show no such effect.

The observed effect is mearly an artifact of the observational process.

What next? The speed of magnetism?

Circular arguments... (2, Interesting)

nebbian (564148) | more than 11 years ago | (#5036859)

Isaac Newton thought the influence of gravity was instantaneous, but Einstein assumed it travelled at the speed of light and built this into his 1915 general theory of relativity.
And then...
Kopeikin found another way. He reworked the equations of general relativity to express the gravitational field of a moving body in terms of its mass, velocity and the speed of gravity. If you could measure the gravitational field of Jupiter, while knowing its mass and velocity, you could work out the speed of gravity.
...using relativity, which has the assumption built in.
I love it! Take a formula with an assumption in it, rework the formula, then get the formula to prove the assumption.

Example:
Let a = 2b + c (1)

a - 2b = c
-2b = -a + c
2b = a - c

Now substituting for 2b in (1):
a = a - c + c
a = a!! Brilliant!! Gravity travels at the speed of light!!!

So we prove relativity using relativity. Erm... what's wrong with this picture?

huh, gravity is light speed (1)

mad mad ninja (610973) | more than 11 years ago | (#5036889)

gravity moves near the speed of light .95, but with a possible .25 margin of error, so it could be quite a bit slower too. now i think i will ask stupid question. Maybe gravity is some werid reaction, that everything reacts to, on a atomic level or something, it moves slower than light so maybe the atoms or molucles have to "see" and know theres gravity, so its a kind of information... hmmm gravity = information deliverd at lightspeed and activated (.05 the speed of light) later, fun idea.
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