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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.
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!
Uh oh.
Looks like someone didn't account for gravitational time dilation.
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.
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).
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.
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...