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NASA Gravity Probe Confirms Two Einstein Predictions
sanzibar writes "After 52 years of conceiving, testing and waiting, marked by scientific advances and disappointments, one of Stanford's and NASA's longest-running projects comes to a close with a greater understanding of the universe. Stanford and NASA researchers have confirmed two predictions of Albert Einstein's general theory of relativity, concluding one of the space agency's longest-running projects. Known as Gravity Probe B, the experiment used four ultra-precise gyroscopes housed in a satellite to measure two aspects of Einstein's theory about gravity. The first is the geodetic effect, or the warping of space and time around a gravitational body. The second is frame-dragging, which is the amount a spinning object pulls space and time with it as it rotates."
Please, can somebody restore the fortune database? Thanks.
Uh, and First Post.
But you can confirm predictions....
Note that the posted description makes no mention of proving anything, unlike the original submission... Confirming just means that further evidence was in line with expectations; not conclusive by any means. It's always good to hear that our understanding of physics is sound, even if new mysteries are more exciting!
It doesn't state the theory has been confirmed, it says two of the predictions made by the theory has been confirmed.
Uh oh.
Looks like someone didn't account for gravitational time dilation.
"Imagine the Earth as if it were immersed in honey," Francis Everitt, GP-B principal investigator at Stanford University in Palo Alto, Calif., said in a statement
Doh, this is Slashdot, we want a car analogy, please. And have the numerical results expressed in libraries of congress per football field. Thanks.
I am not an American, but I have seen both the blue pearl image and the pale blue dot image. I have read about how long these projects have run and the astounding quality of the instruments that must be on satellites like these along with the massive foresight it must have taken at launch time to make them relevant decades later. You can criticize the USA all you want for their wars, and I have heard some harsh criticism of NASA too but the most astounding images and discoveries have always come from the here because they are on the pinnacle of space exploration. The world would be a lot less interesting if it wasn't for them.
http://einstein.stanford.edu/Media/Simple_Expt_Anima-Flash.html has a simple animation explaining the gravity probe B experiment.
Agreed, make it so. Geordi, estimate developement period from current stardate. Data, start doing some calculations. Wesley, contact Dr. Sheldon Cooper and piss him off.
The Slashdot D2 discussion system sucks. Turn it off in your account options and use the old D1. That's what I do. I much prefer to be able to see all the comments at one time.
I'm sorry, I posted this comment to the wrong article... sigh.
The effects of gravity are at macro scales, not quantum scales. From what I understand, the observer effect doesn't really kick in until you start talking about stuff smaller than atoms. The universe is a bit more well-behaved at scale sizes larger than an atom, where chemistry and classical physics kick in. Our other end of non-understanding doesn't start until you get to the very macro, all the dark matter and dark energy floating around out there that no one really knows anything about.
Occasionally living proof of the Ballmer peak.
t (basically ALL experience is subjective to the observer - even scientific ones...)
That's not part of quantum mechanics at all. That's a gross generalization made philosophical that arose out of an actual quantum mechanical principle.
Measurement-related QM principles, like wavefunction collapse and Heisenburg, are only meaningful when what you're observing is the size and scale of a quantum state, which is very, very small. Gravitational effects are for the most part (and in this case) for large objects, where QM principles are unimportant.
You need to actually study quantum physics if you want to talk about these things like an adult. It's obvious to everyone that HAS studied quantum physics that you're spouting nonsense and claiming that Science supports you. Quit watching "What the bleep do we know?". It's full of people lying to you to sell you an idea (and one scientist who was duped and every single quote taken out of context).
Relativity and black holes look like bugs in a not-very-well thought-out physics simulation. This sort of thing makes me wonder if the universe isn't just some extra-dimensional college kid's thesis project on how to find the best way to turn hydrogen into plutonium.
I'm trying to teach myself to set people on fire with my mind... Is it hot in here?
From what I have heard, the reason it took 52 years to get this spacecraft into space was political, not technical.
There is no doubt that the technology developed to measure these parameters is very impressive. The real question is whether or not it was worth the effort.
When I was at JPL in the 1980s a person who had published numerous papers in both experimental and theoretical relativity explained why scientists within the space program were not supporting this project. Since this conversation took place thirty years ago I must paraphrase:
"No modern theory of gravity predicts anything else, and if the measurements showed anything but the predicted results it would be assumed to be an experimental error. Unlike the technology used to search for gravitational radiation (which is also used to study the atmospheres of planets), the hardware in this spacecraft cannot be used for any other scientific experiment."
So for 52 years the money has been used for other science. For a much more worthy project read about the recently canceled LISA project.
If you wish to read about the politics of how a science project is chosen by NASA I can think of no better description that Steven W. Squyres' "Roving Mars" where he describes how the Mars Rovers were nearly canceled.
Exactly. Quantum mechanics only starts to be noticeable about ~50nm or so. In contrast, gravity is normally only noticeable with objects best measured in yottagrams (that's "quintillions of tons", for those of us a bit fuzzy on the extreme SI prefixes).
Now, there's been a huge amount of speculation as to how the two combine, especially from theoretical physicists like Dr. Hawking. However, there have been absolutely no experiments in quantum gravity, for one simple reason: the only time you get that much mass into that small a place is in a black hole or other singularity.
Theory : There is ALWAYS 2 oranges in a bag.
Observation : A bag containing 5 oranges.
Conclusion: 2 oranges in a bag can reproduce
No, GPS does takes General Relativity and Special Relativity into account, and confirms both nicely. Due to the motion of the spacecraft in orbit with respect to us on the ground, one would expect the GPS satellites to lose about 7 microseconds a day. However, because the satellites are further out of our gravity well, General Relativity predicts the satellites will gain about 45 microseconds a day. Basically, this means that if GR and SR were not taken into account, the GPS system would be useless after about 2 minutes.
Source: http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps.html
However, the effect of Frame Dragging is many orders of magnitude smaller, to the point where it will not have a measurable effect on GPS. To even have a hope of measuring it, Gravity Probe B had gyroscopes made from a set of the most perfect spheres ever manufactured. If you were to scale these spheres up to the size of the earth, the tallest mountain would be less than 1 meter tall.
...si hoc legere nimium eruditionis habes...
It depends on your perspective. It's "relativity" because most measurements you make *are* relative to your reference frame, only the speed of light (and various invariant quantities) are absolute.
The relativity that SR and GR deal with is different in kind than the "peculiarities" of quantum mechanics. And, the previous post was correct: the observation-related uncertainties of QM are (mostly) only important when systems get to microscopic scales. Yes, the same microscopic laws apply to macroscopic physics, but in most cases the effects of large number statistics swamp out the "peculiar" effects and the systems are indistinguishable from classical (or relativistic) systems.
Even ignoring all that, it's incorrect to say that any of it is "subjective." What seems to be true is that the observer is inescapably a part of the system he's observing, and sometimes funny things happen as a result of that. Observers may disagree about details (times, speeds, etc) due to relativity and differing reference frames, but once an event has occurred, anyone who is in a position to observe it will agree about what happened, and can calculate objectively what an observer in a different reference frame would report.
The goal was to get numerical results to 1% accuracy, and the actual measurements only achieved %19 percent accuracy. This was due to a design error.
On top of that, other researchers made better measurements using other much cheaper satellites.
So they got scooped and their final results were not what they had planned. Not a complete failure, but not a real success either.
Why is Snark Required?