Space-time Is Swirling Around a Dead Star, Proving Einstein Right Again (space.com) 55
schwit1 quotes Space.com:
The way the fabric of space and time swirls in a cosmic whirlpool around a dead star has confirmed yet another prediction from Einstein's theory of general relativity, a new study finds.
That prediction is a phenomenon known as frame dragging, or the Lense-Thirring effect. It states that space-time will churn around a massive, rotating body. For example, imagine Earth were submerged in honey. As the planet rotated, the honey around it would swirl — and the same holds true with space-time.
Satellite experiments have detected frame dragging in the gravitational field of rotating Earth, but the effect is extraordinarily small and, therefore, has been challenging to measure. Objects with greater masses and more powerful gravitational fields, such as white dwarfs and neutron stars, offer better chances to see this phenomenon...
The researchers noted that they used frame dragging to yield insight into the rotating star that caused it. In the future, they said, they can use a similar method to analyze binary neutron stars to learn more about their internal composition, "which, even after more than 50 years of observing them, we do not yet have a handle on," study lead author Vivek Venkatraman Krishnan said. "The density of matter inside a neutron star far exceeds what can be achieved in a lab, so there is a wealth of new physics to be learnt by using this technique to double neutron-star systems."
The scientists detailed their findings online Thursday in the journal Science.
The way the fabric of space and time swirls in a cosmic whirlpool around a dead star has confirmed yet another prediction from Einstein's theory of general relativity, a new study finds.
That prediction is a phenomenon known as frame dragging, or the Lense-Thirring effect. It states that space-time will churn around a massive, rotating body. For example, imagine Earth were submerged in honey. As the planet rotated, the honey around it would swirl — and the same holds true with space-time.
Satellite experiments have detected frame dragging in the gravitational field of rotating Earth, but the effect is extraordinarily small and, therefore, has been challenging to measure. Objects with greater masses and more powerful gravitational fields, such as white dwarfs and neutron stars, offer better chances to see this phenomenon...
The researchers noted that they used frame dragging to yield insight into the rotating star that caused it. In the future, they said, they can use a similar method to analyze binary neutron stars to learn more about their internal composition, "which, even after more than 50 years of observing them, we do not yet have a handle on," study lead author Vivek Venkatraman Krishnan said. "The density of matter inside a neutron star far exceeds what can be achieved in a lab, so there is a wealth of new physics to be learnt by using this technique to double neutron-star systems."
The scientists detailed their findings online Thursday in the journal Science.
False. (Score:2, Insightful)
This does not prove Einstein right. This proves Josef Lense and Hans Thirring right.
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Much of Einstein's theories will never be proven right.. Some have already been disproven, even before he was dead.
But the point here was that yet again ANOTHER theory of Einstein has been confirmed by observation. Which is amazing if you consider how long ago the guy lived and how revolutionary his ideas and theories where at the time. We've not yet discovered just how lucky the world was to have him, even for the short time he was alive.
what about... (Score:2)
What about thinking it was a good idea to marry Mileva Mari.
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Maric that is.
Comment removed (Score:5, Informative)
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You don't prove a theory right, that's not the way it works. You fail to falsify it.
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You don't prove a theory right, that's not the way it works. You fail to falsify it.
Also you don't fly, you just leap and fail to land. In theory nothing is discovered either, you could just be in the Matrix where nothing's real. Also there's nobody here, we're just highly advanced chat bots. In fact so are you, you are just programmed to think you're real. But it's okay because this is all a dream anyway...
Re: False. (Score:2)
You parent doesn't refer to Einstein's relativity, but to the EPR paradoxon (aka quantum teleportation, "spooky action at distance"). More specifically, to his conclusion that this would prove quantum mechanics is absurd and must therefore be false.
He was wrong: QM is absurd, but exists exactly as absurdly as he said it would be.
Hence he was "wrong, but still mostly right" on this one.
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It's hard to call QM a theory if by that you mean it explains something. What it is is a method of calculation, a very good one. But it doesn't explain anything. And it doesn't work so well with relativity or relativity doesn't work so well with it, the jury is still out. Many theoretical physicists realize there is a problem and are searching for something deeper.
Re: False. (Score:2)
Something that explains a phenomenon is not necessarily a theory. A theory has to make predictions, it doesn't have to make sense.
In fact unreasonable explanatory power is the hallmark of pseudoscience, which is constructed to pass the "stands to reason" test for some audience
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That doesn't prove any of Einstein's theories wrong. It proves a personal bias if his wrong.
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Wrong how? Because of the quantum gravity theory that has upended relativity? Well---that hasn't happened.
Also, quantum mechanics does not prove anything. It's a model/tool.
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True [Re:False.] (Score:5, Informative)
This does not prove Einstein right. This proves Josef Lense and Hans Thirring right.
Lense and Thirring showed Einstein's equations predicted frame dragging around a massive object. [wikipedia.org]Showing Lense and Thirring are right will also show Einstein was right.
(and, Einstein contributed significantly [pitt.edu] to Thirring's work.)
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No. That isn't how "making a prediction" works.
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I'm not here to pander to you. The truth is the same, if you like it or not. You're not somehow right or good because your friends patted you on the back for saying whatever you said.
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Sure, sure. But it really could prove Josef Lense and Hans Thirring right, because they were making an observation about implications of the math, not proposing a theory.
Even in the extreme case where Einstein was wrong, and it only looks like he's right when we look out from Earth because of things we don't yet understand, Josef Lense and Hans Thirring would still be right about the implications of Einstein's theory.
For example, imagine Earth were submerged in honey (Score:3)
Sweet!
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Anyone have a good explanation of frame dragging? (Score:3)
Real question for the tech crowd: can anyone give a really good explanation of frame dragging?
Or alternately, is there a good explanation online somewhere?
I'm looking for something that gives a good introduction with an intuitive sense of what's going on, for post grads who understand college-level math but don't want to get bogged-down in the math. People who, for example, studied chemistry or civil engineering and want a good overview.
Any suggestions?
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The math itself can either be described in a straightforward way, or the explanation can sound remarkably like someone slapping the table with their e-peen. To the extent that I have seen explanations of things I already know and use regularly become incomprehensible.
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It's not really that hard. Einstein was a big fan of thought experiments, which is more or less the opposite of just using the equations and not thinking too much about it. Einstein was also a geometer, so a lot of his explanations are geometric. I think this is a bit unfortunate because it leads to a lot of geometry analogies that may not be completely accurate, or that give the impression that the geometric interpretation is the *only* interpretation.
Einstein developed special relativity by thinking about
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I'd imagine it is analogous to a vortex of water draining into something. As the water spins around, based on the speed of rotation, peaks and troughs in the standing waves become apparent. As the part of the vortex closer to the drain is going faster than the upper parts, it creates the vortex shape. That is the frame dragging effect as there are differing speeds in the rotational column. In the neutron star example, it's the drain and spacetime is more or less dense in a vortex shape around the star (
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The question is, does the vortex swirl the opposite way if observed from the southern hemisphere? :-)
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I guess if you flush your toilet above the equator on the star it's one way and below the other way. But it might be hot, so be careful with experiments.
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Re:Anyone have a good explanation of frame draggin (Score:5, Informative)
I'll take a shot.
Imagine you're an electron sitting next to a long wire. You feel zero force because the electrical forces from the electrons and protons cancel each other out.
Now, imagine the electrons in the wire are moving through it. You're still sitting stationary (relative to the wire). You see the protons just sitting there so no change in the attractive part of the force, but the electrons are moving (relative to you) so you see them as Lorentz contracted in the direction of their motion, according to special relativity. They're a little closer together than they were before, so there's a little more repulsive force. It's stronger than the attractive from the protons, so you feel a net repulsion.
If you (the electron) were to move along the wire at the same speed as the other electrons you'd see them as the "rest" distance apart but the protons as being closer together, so net attractive force.
If you're a scientist sitting still in the lab you're watching the behaviour of the electron next to the wire with some disbelief. It looks like there's some weird extra force that depends on the movement of the electrons in the wire and the test electron. You can think of this force that results from the special relativistic effects as an actual force or an artifact of switching between frames of reference. Whichever, we usually call it "magnetism."
Now imagine you've got some rod or wire and you are not an electron, but a neutron. Sitting next to the rod you feel a gravitational attraction to the matter in the rod. If you move along the rod, you see it as Lorentz contracted, meaning all the atoms in it are a little closer together (along the axis of your motion). So you feel more gravitational attraction than you did before. Gravity produces these change-of-frame forces just like the electric force does. In fact, those forces are so similar to magnetic ones we call them gravitomagnetic. They're not quite identical though, because gravity is always attractive and the gravitational field self-interacts, unlike the electric field.
If you accelerate electrons in a wire, an electron sitting next to that wire will feel an additional force in the direction opposite the acceleration. This "induction" results because of the finite speed of propagation of the electric field, or the changes that are caused to it by the acceleration. The same kind of thing happens with accelerating masses, except the force is in the same direction as the acceleration because gravity is attractive. So if I fly my solar sailing ship next to you under acceleration, you'll find that a little bit of my momentum gets transferred to you, and you get dragged along in my wake a bit. This is linear frame dragging. Apparently Einstein recognized this effect and wrote about it, but didn't call it frame dragging.
A rotating planet or pulsar is a spinning ball of gravity charges (mass) and so you get (gravito)magnetic forces just like you would with a spinning ball of electric charges, or an appropriately shaped coil of wire. There are a whole bunch of effects because of time dilation and the general relativistic effects of the gravitational acceleration from the planet itself, but the biggest one is a force along the spinward direction.
Roger Penrose proposed a mechanism to harvest energy from spinning black holes using frame dragging. Reva Williams showed that mechanism could provide the energy to power quasars, and gravitomagnetic effects could explain the relativistic jets that have been observed coming out of the regions above black holes' poles.
This is a light introduction to the relativistic explanation of magnetism: http://physics.weber.edu/schro... [weber.edu]
And this talks about gravitomagnetism: https://en.wikipedia.org/wiki/... [wikipedia.org]
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Yeah. It seems like such a ridiculously small effect, but that's countered by there being a ridiculously large number of electrons in a wire, and the electric force being ridiculously strong.
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It's pretty easy to work out the math with some reasonable assumptions, BTW. Of if you're mathematically minded, my first link derives Maxwell's equations and some of the relevant laws using only electric forces and relativity.
Thanks (Score:2)
Thanks - that was very well put.
Too few people on Slashdot take the time to actually explain something.
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Thanks! It's nice to see real science articles on Slashdot.
To be fair, Lorentz forces (electric or gravitational) are usually taught as just something that exists, perhaps combined with nonsense like planets spinning in honey. As with so many things, the truth is both amazing and not really that complicated.
If you hated high school / college electromagnetism because it seemed pretty arbitrary, Electricity and Magnetism: Berkeley Physics Course Volume 2 by Edward Purcell is a whole textbook that develops EM
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But you're going to need to buckle down and work at it. You get out what you put in.
I'm doing a Coursera on Special Relativity at the moment, and it's worth the 4-5 hours study time a week. I'll keep the OCW link on file for when I gel like stepping up a notch. But I might finish my French refresher or German starter course first.
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To simplify the calculations, let's assume the earth is spherical.
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Not only spherical, but featureless and uniform density.
Which is better than the typical Newtonian assumption, that it is a dimensionless point mass.
"Dead Star" (Score:3)
is not a proper astronomical term.
U think they are referring to neutron stars, but some of them are definitely not dead.
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Neutron stars are not the only way stars end their lives, or even the most common.
Something with 1 solar mass (Ie the sun), will finish its run of the main cycle by blowing up into a red giant for a while before settling down into a white dwarf for a protracted period before finally settling into its final outcome as a black dwarf. "Dead Star" is a pretty apt description. It's finished its nuclear burn, and its more or less just the embers. This is the fate of most stars. (A small cohort much larger in *mas
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10^10000000000000000000000000000000000000000000000000000000000000000000000000000 years
Just Read The Friendly Paper (Score:2)
The thing I'm fascinated about is that the white dwarf - an object of approximately Earth's size and the Sun's mass - has a rotation period of less than 200 seconds and possibly less than 20 seconds. That's ... weird.
Rotating at 430 to 4300 times the speed of Earth's rotation ... that's a lot of a change, but not so far as to be impossible to envisage.
The theory is correct (Score:2)
When asked by an assistant what he would do if Arthur Eddington's measurements of sunlight during a 1919 solar eclipse failed to confirm the theory of relativity's prediction that gravitational fields would bend light, Einstein famously replied "Then I would feel sorry for the good Lord. The theory is correct."
Many have called this arrogance. Maybe, but if so it was extraordinarily well-justified. Few scientific theories have amassed as much supporting evidence, in so many different contexts. And maybe