Double Pulsar Discovered 293
jabberjaw writes "Nature is reporting that a set of two pulsars could be emitting gravitational waves. Einstein predicted the existence of gravitational waves in his general theory of relativity, but a gravitational wave has yet to be detected. Find out more about gravitational waves and pulsars at Eric Weisstein's World of Physics."
Nothing new... (Score:4, Funny)
Re:Nothing new... (Score:3, Funny)
Coward.
Speed of Gravity (Score:5, Interesting)
I suppose so... otherwise we could eventually devise faster-than-light communications, and I don't think the Universe is that nice
Yes (Score:5, Informative)
Maybe Not. (Score:5, Interesting)
Some scientists that have inspected the calculations believe the experiment is flawed and that they instead measured the speed of light itself (ie: they probably measured the speed of the light they were using to make their observations with, not the speed of the Jupiter distortion).
Correct answer: The speed of gravity is not (yet) a scientifically proved and universally accepted fact. Saying anything else is bad science.
Re:Speed of Gravity (Score:5, Insightful)
We have determined that it is at least 2x10^8 m/s, however, it may be as much as 3.6x10^8 (faster than light). We honestly don't know. I'm pretty sure I heard my quantum mecanics professor at the University of Arizona mention something about Einstein's theories requiring light and gravity to equal in speed, but I'm an aerospace engineer, not a quantum physicist. If they do equal...if the sun were to disappear, we would see the light of the sun and still be fine orbit wise for about 8 minutes. Kinda funny to think about.
As for the faster-than-light communications, we could do that with tangled photons. Einstein was troubled by the fact that quantum entanglment causes an instantaneous change across a large distance. It's been used in a large number of sci-fi novels, including Orson Scott Cards Ender's Game series of books.
Comment removed (Score:5, Interesting)
Re:Speed of Gravity (Score:5, Informative)
Some previous Slashdotters showed [slashdot.org] us [slashdot.org] how [slashdot.org] (first link is to the highest quality download).
I got it to work fine with this (remove the spaces!):
curl "http://a768.g.akamai.net/5/768/142/3f9e9589/1a1a
Elegant Universe (Score:2)
Re:Speed of Gravity (Score:5, Interesting)
The problem with quantum teleportation is that you need to send classical information in order for the receiver to reconstruct the quantum state to be transmitted.
When Alice prepared her entangled quantum bit with \phi, the state that is to be transferred, Bob's (entangled) quantum bit is in a superposition of states that do not yet reveal any information on what \phi was. Alice needs to measure her \phi and entangled qubit and send that info to Bob, who can then apply some operators on this copy of the entagled qubit and that puts it into the state that \phi originally was in. So the speed of quantum teleportation is actually tied to the speed of classical information transfer, thus limited to the speed of light.
Alex
Re:Speed of Gravity (Score:2)
Doesn't matter how far apart the particles are... the change is instantaneous.
Re:Speed of Gravity (Score:2)
Re:Speed of Gravity (Score:2, Informative)
As for the faster-than-light communications, we could do that with tangled photons. Einstein was troubled by the fact that quantum entanglment causes an instantaneous change across a large distance.
I assume you're talking about the fact that two spin-1/2 particles generated in a single decay have entangled spin polarization states. These spin states cannot be used to transmit information faster than light. While it is true that the effect happens over arbitrarily large separations, the people doing
Re:Speed of Gravity (Score:5, Informative)
As I understand it, though, there are two ways to look at it. The Earth is approximately 8 light-minutes from the Sun. The Earth is either orbiting the Sun's actual position, or it's orbiting a point that would be about eight minutes in front of the Sun's extrapolated path based on its position and momentum at that given instant.
It comes down to a question of whether or not gravity is a field or a particle. If it's a particle, then it must travel at some unimaginable speed. If it's a field then it would share some of the properties (like velocity and direction) of the object that generates it, and changes to the field would propagate outward from the object at the speed of light. These changes to an object's field of gravity are thought to produce "gravity waves" that have yet to be detected.
I could very well be muddled on this subject but I have done some reading on it. Please correct me if I'm wrong.
Re:Speed of Gravity (Score:5, Interesting)
That's what I get for trying to discuss something I'm familiar with but not extremely knowledgeable of at 3:30 in the morning.
Re:Speed of Gravity (Score:2)
In engineering we have many phenominon that are not completely understood. We develop mathematical models for them, but it's often the case that a phenominon can have multiple models that work well in different cases.
Particles and waves aren't phenominon by themselves. Particles and waves are mathematical tools. They both describe motion traveling at the same speed. Just because you flip rulesets doesn't
Re:Speed of Gravity (Score:2)
Re:Speed of Gravity (Score:4, Informative)
Now imagine it in 3D.
Re:Speed of Gravity (Score:2)
For gravity to actually be a product of the acceleration of the universe, then that acceleration would presumably have to be non-uniform in order to account for the inverse-square nature of gravity.
Re:5p33d 0f gr4v17y (Score:3, Funny)
Re:5p33d 0f gr4v17y (Score:2, Informative)
heh.. (Score:2)
Re:Speed of Gravity (Score:2)
Re:Speed of Gravity (Score:5, Interesting)
non-local, that is it isn't a property of a
single particle, its a property of a collection
of particles. You can't use entanglement to
send information faster than light, because you
can't use entanglement to send information at all.
What you can do is use entanglement to had extra
information to a classical communication channel.
If you add to a channel transmitting n-bits of
information, n entanglement pairs of particles one
part of each pair at the reciever and one at the
transmitter, then you can send 2^n bits of information which is fanastic. But without the
classical channel you can't send anything at all,
so dispite being non-local, entanglement evades
brakeing the rule that you can't communicate faster than light.
Question for a physicist (Score:5, Funny)
Re:Question for a physicist (Score:2, Funny)
Re:Question for a physicist (Score:2)
detecting gravitational waves? (Score:3, Interesting)
gravitons and waves (Score:2)
gravitons (Score:2)
Now the problem still is how to measure them, as that would probably yield all kinds of interesting things. If I'm not mistaken M theory even predicts that gravitons travel accross dimensions, so they could be used to communicate with somebody out there... pretty crazy.
Re:detecting gravitational waves? (Score:4, Insightful)
What are you talking about? There is no such thing as an "anti-graviton" since the graviton is its own antiparticle, like the photon is. And how would detection of a gravitational wave help advance technology as opposed to pure science? Pure gravity research is not exactly known for its technological applications.
And it isn't obvious how we will start "converting energy" into gravitons once we've succeeded in "determining their existence". Except in a trivial sense, like when you push a rock up a hill. But you can do that now.
Who says there's not an anti-graviton, anti-photon (Score:2)
Re:Who says there's not an anti-graviton, anti-pho (Score:3, Insightful)
You said:
"No, the graviton can very well have an anti-graviton and a photon an anti-photon. The argument against it would be that both things don't have a charge...well neutrinos don't have charges either, but they have anti-particles."
You're misunderstanding why Photons Gluons and presumably Gravitons, if they exist, do not have anti-photons, anti-gravitons etc. and are actually THEIR OWN ANTIPARTICLES. It is not because they have no
Re:Oops! (Score:2)
"The Standard Model of particles says there's no ANTI-graviton, that's who!
-sorry 'bout that.
Re:detecting gravitational waves? (Score:4, Interesting)
Indirect detection (Score:5, Interesting)
You can measure the orbit precisely when there's a pulsar in the system, which is a good timing source. Then you can check whether the orbit's decaying at the rate predicted by the math of gravity wave radiation.
That measurement's been done for another binary system. See http://astrosun2.astro.cornell.edu/academics/cour
Observation agrees with Einstein in this case.
Re:Indirect detection (Score:2)
a black hole, extra-terrestrials, cow farts- the NSA..
Re:detecting gravitational waves? (Score:5, Funny)
you're the science equivalent of the guy who says his OS is AOL.
Re:Metaphysics is exciting... (Score:2)
relativity predicts gravitational waves and their properties, and we actually know quite a lot about them so please stop making it sound like physicists are just as clueless as some random person on the street who likes to think he's a bit of a philosopher on the matter.
there is so much indirect evidence for gravitational waves, and they're such an important part of the theory that if they don't exist we're in a lot of trouble. we also know abou
Re:Metaphysics is exciting... (Score:2)
While the strictly etymelogical meaning of 'metaphysics' means 'beyond physics', it isn't used by a single actual physicist to refer to their work. Thats because, obviously, a whatever a physicist is working on is likely physics to them.
Do a simple websearch on metaphysics: you wont find a single link using the word
Re:detecting gravitational waves? (Score:3, Informative)
Re:detecting gravitational waves? (Score:2)
Seems to make sense.. (Score:4, Insightful)
it is presumed... (Score:2)
At last?? (Score:4, Informative)
How fast is gravity? (Score:4, Insightful)
If the sun went poof, how long would it take for Earth to go off into space? 8 minutes or as soon as it happened?
Re:How fast is gravity? (Score:2)
Actually you wouldn't notice (Score:4, Interesting)
BUT, assume the Sun winked out while it was night for you.
You wouldn't feel a thing.
No massive, "Oh, MY GOD we're lurching into space!" That's the whole point of space curved by gravity, you can't tell that you're not traveling a straight line. The weather would goto hell in a handbasket fast from no incoming heat after a few minutes or hours, and of course dawn wouldn't come. There might be some tectonic activity, some isolated magnitude seven and eights here and there, but most likely not immediately.
No you wouldn't even notice at first as the night hung on forever, and Earth continued on a straight line into the blackness...
Re:Actually you wouldn't notice (Score:2)
Is this a survivable situation by even a small group of humans?
I've wondered about it a couple of times.
Re:Actually you wouldn't notice (Score:5, Interesting)
So Nemesis swings by and strips the Earth off the sun's orbit. The goes dark and cold and there is some tectonic activity. The interesting thing is that the Earth's temperature starts to drop to match the temperature of open space. The oceans freeze and the atmosphere condenses and rains down to the surface, where it forms strata based on what temperature the gas condenses at. To the protagonist goes out side and digs past the CO2 until he finds a strata of O2 and brings a pail of air inside.
But I doubt even a small number of people could survive this for long!
Re:Actually you wouldn't notice (Score:2)
Re:Actually you wouldn't notice (Score:2)
Or maybe if you lived near an area that had a lot of geothermal energy available -- yellowstone and iceland come to mind.
The problem as I see it is the oceans would freeze over and there would be nothing but ice.
So you would need the nuclear energy to produce water.
All the animals would die off rather quickly I surmise - from no food, no warmth, no
Re:Actually you wouldn't notice (Score:3)
Or maybe if you lived near an area that had a lot of geothermal energy available -- yellowstone and iceland come to mind.
Unless your nuclear plant or geothermal area would be in a sealed, warmed, VERY deep cave - no, I don't think so.
The problem as I see it is the oceans would freeze over and there would be nothing but ice.
The biggest problem is
Re:Actually you wouldn't notice (Score:2)
Even though there is no sun, the earth is still warmed internally and that may be enough to have an atmosphere (albeit a cold one) in certain areas. Plate tectonics would still be active and there would still be volcanic regions. Life still might take place at the bottom of the oceans where organisms feed off the chemicals rather than have to rely on photsynthesis.
Humans would have to move unde
Re:Actually you wouldn't notice (Score:2, Insightful)
The planet is under CONSTANT stress from the pull of the sun, and it compensates in more ways than I can even imagine. Suddenly, that force is gone.
What happens when you lean against a leash ( what? I was a very hard to control child, leashes seem like a perfectly reasonable idea at the time ) while someone is holding the other end. Suddenly, they let go, without you expecting it. You fall on your face.
That is exac
Re:Actually you wouldn't notice (Score:3, Informative)
Re:Actually you wouldn't notice (Score:2)
And I am not just talking about fault lines ( although I don't doubt that we'd see some violent shakers ), but all the little ways the earth compensates for the constant tug from the sun. It's like a house of cards, pull table out from underneath and the house falls.
Re:Actually you wouldn't notice (Score:3, Informative)
Please learn some basic geology before making such claims.
Some clearifications and corrections (Score:2)
When I said you wouldn't even notice, I only meant in the short term from the lack of gravitational influence. In fact I stated this in a couple of ways, and yet some have responded as if I think we don't need a Sun. Bihma had an interesting eventual outcome response but lets c
Re:Actually you wouldn't notice (Score:2)
How many people if they hadn't seen it go dark, would look up after and say HEY! I know the MOON should be right there!
How many people do you know that can detect the motion of the stars by just looking up? The daily rotation of the Earth would swamp out any yearly changes no longer occuring even if you could notice the nightly march of stars across the stars.
Man you have better eyes than mine! :-)
Re:Actually you wouldn't notice (Score:2)
I think that the event horizon of a black hole can
Re:Actually you wouldn't notice (Score:2)
Re:How fast is gravity? (Score:2)
Re:How fast is gravity? (Score:2)
Pfft (Score:2)
This seems cool... (Score:2)
Actually not yet, but... (Score:5, Informative)
It's for the LISA (Laser Interferometer Space Antenna). Space.com did a story on it a little while back [space.com], and it was in a Scientific American, but I'm not sure which, I have too many lying around. Unfortunantly, it doesn't launch until 2009.
G Waves and other fun things to look for (Score:4, Informative)
As an aside, with a system this unique, and not to sound too much like a loon, but perhaps we should look for an ET presence. Not as the creators, but there maybe unique physical process than can be exploited in such a system, and doing so may give off a detectable technological signature.
Re:G Waves and other fun things to look for (Score:2)
I was about to get all excited and agree that you get get far more sensitivity if you tune it to look for a single specific known signal, but then reality hit. This system has a frequency of 2.4 hours - 0.00012 hertz. Splat, dead idea. LIGO is designed to look in the 10's or 100's of hertz and I doubt it be able to reliably pick up anything much below 0.1 hertz.
I d
Comment removed (Score:3, Interesting)
Re:Gravity doesn't pull, but rather pushes. (Score:3, Interesting)
If I understand you correctly, you are proposing that gravity is property of space, not matter. In this idea space is attracted to space, and as a result the center of the universe is the center of "space mass", and has the highest amount of space presure. The effect that we see is that matter (which has a lower space-density) is displaced by space away from the center, and towards the outer edges. Is this correct?
Now this model would (qualitatively at least) predict that space pressur
Re: (Score:2)
Re: (Score:3, Insightful)
Re:It's about proportion (Score:3, Informative)
To clarify - water is not trying to displace air because it is a minority substance, but because it is a less dense substance. The water pressure at a point is caused by all the water above that point pushing down (because of gravity). Therefore the water pressure at the bottom of the bubble is greater than the pressure at the top of the bubble, because there is more water above it, at the bottom than at
Such theory exists (Score:2)
Nobel prize for pulsar discovery (Score:5, Interesting)
Whoops (Score:2, Interesting)
Re:Whoops (Score:2)
That's just Nobelspeak. Pulsars are studied in the field of radioastronomy, and you often find that Nobel prizes are awarded for a range of activities instead of a single point discovery. For a more famous example, Einstein got his Nobel for advances in theoretical physics and particularly for his explanation of the photoelectric effect. Special Relativity was kind of included in the theor.phys. but its role was not
Re:Nobel prize for pulsar discovery (Score:2)
Of course, the irony is that if someone says to me "pulsar discovery" (and, for the record, I'm a stellar astrophysicist), I immediately think "Jocelyn Bell". I haven't got the first idea who here supervisor was. She may not have won the prize; but she got the credit, well-deservedly.
Re:Nobel prize for pulsar discovery (Score:2)
Re:Nobel prize for pulsar discovery (Score:3, Interesting)
And while Jocelyn has always been very gracious (and modest) when discissing this topic, the majority of astronomers believe that an injustice was done by the Nobel committee. It was precisely because of this injustice, in fact, that when The Nobel was awarded to Joe Taylor for work on the Binary Pulsar (for showing that the
Re:Nobel prize for pulsar discovery (Score:2, Interesting)
Hardly new (Score:2)
Re:Hardly new (Score:2)
For which, remember, they've even won a Nobel Prize.
Re:Hardly new - Wrong! It's new! (Score:2)
tells you less than you might think (Score:3, Interesting)
Alternative theories to general relativity usually also predict such effects, including gravitational waves. So, these results, even if confirmed, don't actually tell you a whole lot. What they do tell you is that Newtonian mechanics isn't quite right, but, then, we already knew that.
In 85 million years, "wioll haven be" (Score:4, Interesting)
The stars will coalesce in only approximately 85 million years, sending a ripple of gravity waves across the Universe
So...wait, 85 million years from when? Now? Or is it 85 million years from what we currently observe, which is probably several million years in the past (neither link provides the distance of the pulsars from earth)?
In other words, will we observe the coalescing in 85 million years, or 85 million + time of transit?
Sheesh, it never occurred to me how dicey verb tense is in astronomy...Talking about the future of distant objects that exist in the past which we are observing presently.. Reminds me of Dr. Streetmentioner's Time Traveler's Handbook of 1001 Tense Formations from Restaurant at the End of the Universe.
Re:In 85 million years, "wioll haven be" (Score:3, Informative)
Besides, google search [google.com] reveals that they are about 1600-2000 light-years away so you can pretty much ignore any questions of "now_here" against "now_there". 85M years +/- 2K years is still 85M years.
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Re:In 85 million years, "wioll haven be" (Score:2)
All right! I can't wait!
No, really, I can't.
And, oh yeah,
[futuregrammar nazi]"...that means in 85M years from today we will-be on haven been seeing it happen." [/futuregrammar nazi]
Just kidding, pal. Thanks for being my googlebitch on the actual distances, though.
Re:In 85 million years, "wioll haven be" (Score:2)
LMAO, googlebitch! That's a pisser
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Animations (Score:4, Interesting)
Animations [csiro.au] of the evolution and current state of the pulsar system are available.
gravity wave detection (Score:3, Informative)
- The first is to photograph the upper atmosphere with an incredibly sensitive camera during night time, the reason is that gravity waves (that have a period of a few hours) cause the upper atmosphere to strech and compress causing the atoms that cause air glow to seporate into layers. this shows up on the image as bands. these gravity waves are emitted from the center of the earth.
- the second is to use an incredibly precise receiver tuned to a reliable transmitter in the HF bands, to a frequency that gets reflected by the ionosphere. since gravity waves will cause the ionosphere to expand and contract the change in velocity will cause the HF signal to be doppler shifted, meaning the gravity wave will be shown up in a slight variation of the incomming frequency.
the second option can be done by ham radio operators (if they really know there stuff), the first option is for universities since only they have the budget to buy the expensive equipment.simon
There are probably no grav waves (Score:2)
And on the other side they'd want to find gravitational waves ? If the forces are really one and only interaction then it all comes down somehow to electromagnetic waves (whatever name we
Hey! This is "The Dish!" (Score:2)
After recently catching "The Dish" on a movie channel, it's nice to see the successors of the guys that brought a 10-year-old me the Apollo 11 TV signal are still in there on the frontiers of science.
Mirror of video (Score:2)
Re:So... (Score:2, Funny)
Well, the ball floated because you missed the Earth, basically the same effect as stated in The Hitchhiker's Trilogy. Your drug induced state probably allowed you to throw the ball at specific yet unrepeatable while sober trajectory. As far as the ball laughing at you, it wa
Re:Bah! That's nothing.. (Score:2, Funny)
Re:Not first (Score:3, Informative)
Wrong. Hulse and Taylor's discovery was of a pulsar and companion neutron star. The companion was not a pulsar. This is the first known double pulsar system. One of the discoverers is a couple of doors down the corridor from me, so I can confirm this as true.
Re:Not first (Score:2)
Re:is this quantum physics? (Score:2)