Stanford’s Gravity Probe B confirms two Einstein theories
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.
After 52 years of conceiving, building, testing and waiting, the science satellite has determined both effects with unprecedented precision by pointing at a single star, IM Pegasi, while in a polar orbit around Earth. If gravity did not affect space and time, Gravity Probe B’s gyroscopes would point in the same direction forever while in orbit. But in confirmation of Einstein’s general theory of relativity, the gyroscopes experienced measurable, minute changes in the direction of their spin as they were pulled by Earth’s gravity.
The findings appear online in the journal Physical Review Letters.
“Imagine the Earth as if it were immersed in honey. As the planet rotated its axis and orbited the Sun, the honey around it would warp and swirl, and it’s the same with space and time,” said Francis Everitt, a Stanford physicist and principal investigator for Gravity Probe B.
A lasting legacy
“GP-B confirmed two of the most profound predictions of Einstein’s universe, having far-reaching implications across astrophysics research,” Everitt said. “Likewise, the decades of technological innovation behind the mission will have a lasting legacy on Earth and in space.”
Stanford has been NASA’s prime contractor for the mission and was responsible for the design and integration of the science instrument and for mission operations and data analysis.
Much of the technology needed to test Einstein’s theory had not yet been invented in 1959 when Leonard Schiff, head of Stanford’s physics department, and George E. Pugh of the Defense Department independently proposed to observe the precession of a gyroscope in an Earth-orbiting satellite with respect to a distant star. Toward that end, Schiff teamed up with Stanford colleagues William Fairbank and Robert Cannon and subsequently, in 1962, recruited Everitt.
NASA came on board in 1963 with the initial funding to develop a relativity gyroscope experiment. Forty-one years later, the satellite was launched into orbit about 400 miles above Earth.
The project was soon beset by problems and disappointment when an unexpected wobble in the gyroscopes changed their orientation and interfered with the data. It took years for a team of scientists to sift through the muddy data and salvage the information they needed.
Despite the setback, Gravity Probe B’s decades of development led to groundbreaking technologies to control environmental disturbances on spacecraft, such as aerodynamic drag, magnetic fields and thermal variations. The mission’s star tracker and gyroscopes were the most precise ever designed and produced.
Played a role in developing GPS
Innovations enabled by GP-B have been used in the Global Positioning System, such as carrier-phase differential GPS, with its precision positioning that can allow an airplane to land unaided. Additional GP-B technologies were applied to NASA’s Cosmic Background Explorer mission, which determined the universe’s background radiation. That measurement is the underpinning of the “big bang theory” and led to the Nobel Prize for NASA’s John Mather.
“The mission results will have a long-term impact on the work of theoretical physicists for years to come,” said Bill Danchi, senior astrophysicist and program scientist at NASA Headquarters in Washington. “Every future challenge to Einstein’s theories of general relativity will have to seek more precise measurements than the remarkable work GP-B accomplished.”
Over the course of its mission, GP-B advanced the frontiers of knowledge and provided a practical training ground for 100 doctoral students and 15 master’s degree candidates at universities across the United States. Over 350 undergraduates and more than four dozen high school students also worked on the project, alongside leading scientists and aerospace engineers from industry and government.
Sally Ride, the first American female astronaut in space, worked on GP-B while studying at Stanford. Another was Nobel Laureate Eric Cornell, who also studied at Stanford.
NASA’s Marshall Space Flight Center in Huntsville, Ala., managed the Gravity Probe-B program for the agency. Lockheed Martin Corporation of Huntsville designed, integrated and tested the space vehicle and some of its major payload components.
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Learn a lot more on testing Einstein’s theories here h/t Dr. Leif Svalgaard via email
Simply amazing! At least someone is still doing real science.
So, spacetime behaves a litle bit like honey? Why don’t we just call it ether?
Wonderful post, Anthony. By the way, Aristotle’s vision of what he called the universe was very similar to the following:
‘“Imagine the Earth as if it were immersed in honey. As the planet rotated its axis and orbited the Sun, the honey around it would warp and swirl, and it’s the same with space and time,” said Francis Everitt, a Stanford physicist and principal investigator for Gravity Probe B.’
Oh, by the way, can someone recommend the ideal GPS device for hiking in and around the Appalachian Trail in Virginia?
Einstein.
A dude.
What would Einstein have said about “scientists” who hide their data even from Freedom Of Information laws? On consensus, he said: It doesn’t take 100 signatures to prove I’m wrong. It just takes one experimental fact.
There are only two nasty little problems to consider before you all get excited. First of all, time cannot change by definition and, therefore, nothing can move in spacetime. This is the reason that the great Sir Karl Popper called spacetime, “Einstein’s block universe in which nothing happens.” (source: Conjectures and Refutations).
Second, it is easy to prove that space (distance) is nothing but an illusion of perception). Surprise!
So these experiments did not prove that Einstein was right (he believed in the physical existence of a spacetime and of a time dimension!). They only proved that some of his equations were right. The interpretations of those equations, however, leave a lot to be desired.
It’s true. GPS satellites are effected by relativity, mainly the relativistic time slowing effect due to the speed of the satellites.
http://www.metaresearch.org/cosmology/gps-relativity.asp
Cool stuff, even if the physics gets a bit deep. 🙂
I joined the staff at Stanford in 1975. Shortly thereafter, I became aware of a program that was referred to in the bureaucratese of the day as Fairbanks, Everett and DeBra or GP-B. They were Bill Fairbanks from the Physics Department, Dan DeBra from Aero and Astro and Francis Everett from the Hansen High Energy Physics Lab. They soldiered on through periods where funding was not easy to raise and challenges as to the importance of the project were periodically raised. The many successes that came about because of their work is yet another testimony to the importance of funding basic research. Bill Fairbank died in the late 1980’s while on his daily run if I remember correctly but it is great that Francis Everett and Dan DeBra were able to see the fruition of decades of world-class work.
It is sad to see the amount of research monies that are being squandered on so much of what passes as science in the climate arena today.
Those are some interesting articles Leif. The reference frame dragging was one of hardest concepts to grasp, for me anyway.
It sure seems like NASA could hire an artist that knew the basics of gravity for a story about… gravity. Neat picture but somewhat misleading if you take it too literally! Don’t look at that green-blue mesh and think that is what the real signature of Earth’s gravitational field would actually look like, well, kind of, but not correct.
At the center of the Earth there is no gravity field, zero. There should be an upside-down V-shaped dimple pointing upward in the middle from the surface inward on that grid at it’s deepest point. Maybe that article will cause some here that might not realize that fact to ‘open the books’, so to speak, and be a bit more enlightened.
Another thing I learned not too long ago is that if the Earth’s density was constant then that upside-down dimple of the gravitational field from the surface to the center of the Earth would be linear, a straight line, and not an inverse squared curve.
That bothers me.
Darn! Einstein is right again. That sucks… we will never be able to travel faster than light… at least in this space-time continuum.
Gives me a bit of comfort as there still non grant grabbing ,AGW screaming ,
real scientists out there..
“The project was soon beset by problems and disappointment when an unexpected wobble in the gyroscopes changed their orientation and interfered with the data. It took years for a team of scientists to sift through the muddy data and salvage the information they needed…”
Did they use Mannian PCA? It’s very good for finding signals that you know are there.
I’d like to know what was the unexpected wobble was caused by. If there was muddy data as a result, that took years to sort, what guarantee is there that cherry picking has not occurred?
I don’t get why the warping of space time is depicted as occurring on a single plane. Is this for illustration purposes only? I would have thought a large body bends space time in every direction.
I still don’t see how you can drag space. I can see gravity warping space (can I?) but I don’t get why spinning drags it. It’s as if we have the luminous aether again.
Awesome awesome science. And what an effort. Shame that AGW money is being pulled out of their funding pie.
I am a degreed physical scientist who will readily admit I have read Einstein thoroughly and proudly comprehend a little bit of it.
From NASA: “According to calculations, the twisted space-time around Earth should cause the axes of the gyros to drift merely 0.041 arcseconds over a year. An arcsecond is 1/3600th of a degree. To measure this angle reasonably well, GP-B needed a fantastic precision of 0.0005 arcseconds. It’s like measuring the thickness of a sheet of paper held edge-on 100 miles away.
Pulling off the experiment was an exceptional challenge. But after a year of data-taking and nearly five years of analysis, the GP-B scientists appear to have done it.
“We measured a geodetic precession of 6.600 plus or minus 0.017 arcseconds and a frame dragging effect of 0.039 plus or minus 0.007 arcseconds,” says Everitt.”
I am glad they were able to sift through the “problems and disappointment when an unexpected wobble in the gyroscopes changed their orientation and interfered with the data.” Good thing the scientists were able to take…”years to sift through the muddy data and salvage the information they needed.”
“Imagine the Earth as if it were immersed in honey. As the planet rotated its axis and orbited the Sun, the honey around it would warp and swirl, and it’s the same with space and time,”
Does anybody have a reference that discusses this “honey swirling” effect for the atmosphere? TIA
More from NASA: “Time and space, according to Einstein’s theories of relativity, are woven together, forming a four-dimensional fabric called “space-time.” The mass of Earth dimples this fabric, much like a heavy person sitting in the middle of a trampoline. Gravity, says Einstein, is simply the motion of objects following the curvaceous lines of the dimple.”
That is a handy image, using gravity to illustrate…gravity. 😀
Should Warmists pay any heed to Einstein’s sayings?
RayG says:
May 4, 2011 at 4:15 pm
“They soldiered on through periods where funding was not easy to raise and challenges as to the importance of the project were periodically raised.”
Old School Scientists. The science was what motivated them. No doubt they made significant personal sacrifices to practice their science. God Bless them and all like them.
xion III says:
May 4, 2011 at 4:43 pm
“I’d like to know what was the unexpected wobble was caused by. If there was muddy data as a result, that took years to sort, what guarantee is there that cherry picking has not occurred?”
There is no guarantee. However, the huge difference between this case and that of Climategaters is that these physicists had physical hypotheses (a huge set of them) that actually specify the data. Climategaters have no physical hypotheses at all, except the few they borrowed from poor old Arrhenius. Michael Mann has never created a physical hypothesis. All he has done is organize proxy data. That kind of fundamental science has to be done, but the very fact that Mann can be tenured and honored as a scientist-without-portfolio drives me up the wall.
The project was soon beset by problems and disappointment when an unexpected wobble in the gyroscopes changed their orientation and interfered with the data.
The mission’s star tracker and gyroscopes were the most precise ever designed and produced.
I’m having difficulty reconciling these two statements.
To warp space and time or to perceive space and time getting “warped”. O_0