The Speed Of Gravity Revealed 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."
Cowardly for a reason! (Score:5, Interesting)
Event Horizon (Score:3, Interesting)
I'd expect... (Score:5, Interesting)
Re:Event Horizon (Score:3, Interesting)
Does this mean... (Score:1, Interesting)
Is gravity has a speed then theoretically we can outrun it
Re:gravity slowing down? (Score:3, Interesting)
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.
Has science gone mad? (Score:4, Interesting)
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!
another dumb question (Score:1, Interesting)
Utter Bullshi-ite. (Score:2, Interesting)
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... (Score:2, Interesting)
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?
Re:Event Horizon (Score:1, Interesting)
Is that only in a vacumn (Score:2, Interesting)
Wild ramblings... (Score:5, Interesting)
Take the sun and instantly accellerate it to almost the speed of light, toward a collision course with Earth. For most of the 8 minutes between acceleration and collision, nobody would notice anything, as light, all other energy, and gravity would all present the sun as occupying its original location.
However, brief moments before the collision, the sun's change of accelleration toward earth will be noticed. Of course, you're noticing the change that happened 93 million miles away, even though the sun is about to impact. However, one second later, the sun will appear to be almost 186000 miles closer, and it will FEEL like it's 186000 miles closer. Suddenly the gravitational accelleration has increased to reflect the new position of the sun. But within that second, you get all the accumulated influences of gravity over a much larger stretch of space than just the 186000 miles it travelled in that time. Since the sun is moving at almost the speed of light, let's say 99% of it, after 99 seconds, the influence of the sun's gravity will only be 1 second ahead of the sun. However, within that one second between the position of the sun and the gravitational influence of the sun is contained the gravitational influence of the sun over the last 99 seconds. You get the combined force in 1 second that you normally would have gotten in 99. So when the Sun's influence is finally felt by Earth, you will not get a force that implies a steady rise in gravitational force of a sun massed object until impact, you'll get a very quick rise in force of an object that is, generally, about 99 times as large as the sun.
And if you remember relativity, when an object is travelling near the speed of light, the mass increases. So the theory at least makes sense. Here's another thing to ponder. If an object the size of the sun suddenly acquired the 99x its mass, would it not either collapse upon itself, or expand rapidly, nova, and the core would collapse upon itself, causing the same result, a singularity, with a small event horizon. And it will be this singularity that will collide with Earth, ripping through it in a fraction of a second, and the sudden, combined gravitational effect on earth will cause it to very suddenly pull out of it's orbit toward the origninal center of gravity of the sun, with a nice city sized hole carved through it.
Ok, this had no purpose at all, but it was interesting to think about. Go on with your business... nothing to see here. Rant over.
-Restil
Is the speed constant? (Score:3, Interesting)
I don't think I like the idea of light being the fastest anything can travel, though. Perhaps it is for many things, but what happens if some forces travel at speeds faster (or multiples), or perhaps simple fractions, and we discount those readings instead of seeing if the old model can be adapted or remade? Well, many questions, few answers from me.
Does anyone remember the 'gravity shielding' story a while back, where a spinning superconductor was supposedly responsible for changes in weight? Podkletnov comes up in a google search for 'superconductor gravity shield' but I haven't heard anything further about it.
Also, what about magnetic forces? How do those work, and at what speed do they 'travel' ?
Re:Has science gone mad? (Score:2, Interesting)
That's how you verify any theory. You do an experiment, and compare what you thought would happen to what actually happened. GR said the speed of gravity would be c, and his experiments showed it to be roughly that (.95 c).
Re:Does this mean... (Score:3, Interesting)
It's like if you're in a boat moving faster than a wave that's chasing you, you may avoid the wave but the water is still there.
Possible to block gravity? (Score:2, Interesting)
Since gravity travels, dosn't that mean there is a possiblity that one can block gravity?
Science Fiction Authors weep (Score:5, Interesting)
Venus is a big swampy planet, eh guys ?
Re:Wow. (Score:5, Interesting)
Mass warps space-time.
Simple proof. Take an object. eg. Pen.
Lob it gently across the room.
Observe how it makes a graceful parabola before walloping your cow-orker on the nut.
Now remember I said Mass warps space-Time. Time is just another dimension. We live in a 4 dimensional space.
We measure time in this silly "seconds" unit but thats stupid. We already have a useful unit for spatial dimensions and that is meters. The conversion from meters to seconds is simply the speed of light. 1second=3e8m
So that graceful parabola is actually very stretched out along the time dimension. It is quite a flat curve.
Now retrieve your pen from your irate colleague and hurl it hard at him.
Note that the curvature seems a lot less, but it took less time. Thus you will find in 4 space the curvature was the same.
Now retrieve pen from the poor sods ex-eyeball and lob it very slowly and gently. Note the curvature seems less, but it takes more time. So in 4 space it is the same curvature.
Carefully, carefully retrieve your pen from your ex-friend and use it to calculate the radius of curvature for all three throws. Wow! Its the same!
And it is the radius of the earth.
In other words, Mass warps space time. There is no gravity, only bent space time.
As they say, Gravity is a myth, the Earth sucks.
Re:Wow. (Score:4, Interesting)
There is a theory that explains why gravity is directly proportional to mass, and why it's always attractive: that gravity is anti-mass. This is not the same as antimatter, which has the same mass as normal matter but reversed charge.
When matter is created from energy, that energy goes into deforming the rubber-sheet of space-time. The main idea of the theory is that space-time doesn't like being deformed (in precise, conservation law terms), and so creates a restorative energy called gravity. Since matter always has positive mass, the energy of the gravity field must always be negative, i.e. always attractive, and always precisely proportional to the mass.
In effect, when you create matter you are borrowing energy from somewhere to deform space-time. That energy could be kinetic from atoms in atom-smashers, or from energy-to-matter conversion in stars, or any number of other sources.
If you read Einstein, you know that there are some forms of electromagnetism that create gravity (most don't, including plane waves of light). According to general relativity, the EM field is more fundamental than the gravity field, and so in theory it should be possible to create gravity waves using electromagnetism. For more info, see page XX of the preface to The Geometry of Einstein's Unified Field Theory [amazon.com].
Re:Event Horizon (Score:5, Interesting)
This is wrong. It is impossible for anything with mass to accelerate to the speed of light. If it is already travelling that speed it can continue indefinitely.
the light is in fact moving in a straight line-- it's just that space is curved in the vicinity of the black hole,
This is semantics. If I throw a softball straight ahead the ball actually moves in a straight line. It is just that space is curved in the vicinity of the earth. Gravity works the same way regardless of the density of the body creating the gravity, so long as the mass is the same.
Re:Weird Implications? (Score:3, Interesting)
Re:Wow. (Score:2, Interesting)
Gravity's speed already established (Score:2, Interesting)
Re:Event Horizon (Score:1, Interesting)
Only items that experience time would be affected by the curvature of spacetime. Only items with mass will be affected by gravity. Only an item with no mass can travel at the speed of light, because to accelerate something with a mass greater than 0 to the speed of light requires an infinite amount of energy. Traveling at the speed of light, you become infinitely short, infinitely heavy, and experience no time.
I can come up with nothing that brings all of these postulates together. It's all like dividing by zero. It makes sense a little to the left and a little to the right, but that doesn't mean it makes sense at the point we care about. My inability to rectify these problems puts me in the same ballpark as all those physicists who haven't yet proven superstring theory. They can't fit it all cleanly together either.
Oh, and black holes don't tear spacetime, they're just really damned dense. So dense that light can not move fast enough to escape its gravity. The whole concept that black holes are black mean that photons are affected by gravity and therefore have mass. rest mass or otherwise I can't say, but there's mass to speak of somehow. The fact that small black holes seem to decay away leaking energy out to somewhere indicates that there are energies that travel faster than the speed of light in the universe.
I could say more, but in my years I have grown wise enough to know that I'll be embarrassed 3 years from now by what I've said here, and how ignorant I was "back then." It happens all the time. So I'll shut up. "Never speak more clearly than you are able to think."
Questions From A Layman (Score:4, Interesting)
So how can one say that Gravity's pull is as fast as the speed of Light when Gravity itself doesn't stay constant in different environments? I never heard light not traveling the "speed of light" so it's a bit confusing.
Ao, from what I gather, blackholes have so much gravitational pull that even light can't escape. Which suggests to me that Gravtiy is stronger than light. It would also suggest to me that gravity is is faster than light because of this. I don't have any sources to back this up, all of this is just my train of thought in words here.
I'd appreciate a simple-as-possible answer as to why my train of thinking is wrong, as i said, i'm no scientist, but this topic is interesting none the less
Re:Wow. (Score:5, Interesting)
If they have confirmed that gravity travels at the speed of light, how does gravity escape a black hole? obviously it does because the only energy that escapes a black hole is in the form of gravitational waves, but if the escape velocity is higher than than the speed of light, how can it get out?
Re:Wow. [correction] (Score:4, Interesting)
Strong, Electromagnetic, Weak, Gravitational
This depends strongly on the distance you choose to measure the force at. At a distance of 1m, as opposed to 1e-15m, the original ordering may be correct.
And as long as we're being nit-picky, I'll point out that human-observable phenomena tend to be larger than 1e-15m
Re:Event Horizon (Score:2, Interesting)
We may be a marvel of evolution, but to say that our eyes are advanced enough to detect that which has no mass is rather quite silly.
Light has mass, my friend. Proof to that is attached directly to what you call your brain.
The energy does not "go away" (Score:5, Interesting)
Take a relatively large gong. Make sure it is reasonably well polished.
Next, take a professional-class camera flash and set the intensity to "fry".
Third, fire the flash at the gong. As the photons bounce off the (polished) gong, it will resound as if having been struck with a solid object.
This was a very awakening demonstration to me...
Re:Photon (Score:3, Interesting)
Anyway, it's true that just igniting some nuclear fuel into fusion isn't that hugely hard, assuming that you have some tritium, not just deuturium, around. But you don't get that much from it compared to the fission bomb you've exploded to burn that small amount of fuel. In regards to power plants, of course using the heat of the core of a fission explosion is not an option for initiating fusion. And all our current technologies currently use about as much energy to initiate and contain fusion in a fuel than they are to usefully extract from it. The vast gulf seperating fission from fusion power is that once you understand the neutron-capturing cross-sections of various isotopes, cobble together a sufficient mass of an approriate fuel, and find a moderator (and moderator arrangement) to go with it, the actual physical, engineering complexity of the reactor is minimal. You could build one by hand, which is essentially what Fermi did. You can control one by winching a control rod into and out of a pile. In contrast, the fusion reaction is very different in this context and an implementation and control mechaninism is fiendishly complex. I suppose that in a way your teacher was right, in the sense that a fission reactor is very, very different from a bomb; while a fusion reactor must by necessity in some qualitative sense be pretty similar to a fusion bomb.
Quick Question (Score:1, Interesting)
Re:Wow. (Score:2, Interesting)
Lumocentrism (Score:2, Interesting)
Correction: (Score:2, Interesting)
Weak
Gravitational
There is no strong force. It's a myth. Just like Neutrons are a myth. No, I'm not joking. Anytime you extract a neutron from an atom, it breaks into a proton and an electron (hydrogen). A Neutron is not a true particle, it's simply a compressed proton and electron. Although scientists say it has the same mass as a proton, it actually is a proton with an electron paired with it (electrons have a very small mass... so small, in fact, that quantum physicists usually say it has no mass) The "strong" force is the force atomic physicists had to invent in order to explain how protons and neutrons would sit together so tightly packed while the protons repelled each other (and the neutrons simply needed a reason to be stuck next to anything at all). The truth is, electrons exist at the center of an atom holding protons together. They form shells which link protons and bind them tightly. This cancels out the positive charge of many (thus the many so-called neutrons), and leaves many protons unpaired within the nucleus which gives the nucleus a net positive charge allowing electrons to orbit the nucleus.
Ever noticed that you won't find any nuclei other than hydrogen without a neutron??? Noticed that the larger the atom, the higher the neutron to proton ratio?? The strong force is supposed to be exactly 100 times stronger than the electromagnetic force, which would allow for nuclei of atoms to reach about 100 protons, thus those beyond that are highly radioactive. (means that once there are 100 positively charged protons, their repelling forces would overcome the strong force and shoot them out of the atom). BUT, the best model of atomic nuclei structure shows rings of electrons supporting ever-larger numbers of protons, thus there is no strong force needed. The positive protons are cancelled out by negative electrons, and thus a spherical crystal-lattice type structure is created within the Atom's nucleus. The unusual shape of this crystal only allows about 300 or so protons within the nucleus before the crystal becomes too densely packed and unorganized that it's insanely radio-active. There is a theory that if the structure were re-organized, there could be an island of stability beyond that point, however, I seriously doubt it. Wow... wouldn't it be awesome to have a noble solid??? *grins*