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
Myrrh says:
May 5, 2011 at 1:07 pm
“Is no one giving me an explanation to my question because no one knows the answer?”
I don’t think the picture is meant to be taken literally. It is drawn that way because if you draw every possible angle in 3d you would just see a sphere of ink. It is drawn in the two dimensions so you can see the shape and once understanding the concept use your mind to apply it to the 3rd dimension.
“”””” Leif Svalgaard says:
May 5, 2011 at 1:44 pm
Myrrh says:
May 5, 2011 at 1:07 pm
Is no one giving me an explanation to my question because no one knows the answer?
The answer is long. Wikipedia has some good pointers: http://en.wikipedia.org/wiki/General_Relativity
Because this is a very simple problem, it surely can’t be beyond your abilities to explain it.
It may be beyond your ability to understand it. By that I mean, that there are fundamental issues about what curvature is and how to express it, and those are not easy to visualize, without resorting to somewhat misleading images [like the bowling ball on a membrane]. Start with the wiki. There are also good books on the subject [referenced in the wiki]
George E. Smith says:
May 5, 2011 at 1:18 pm
I always thought gravity had an infinite range so that shielding is inherently impossible.
The Earth is in free fall around the Sun and thus does not feel any gravity [except its own], just like an astronaut in free fall about the Earth. “””””
So if the earth (at its center) does NOT feel any gravity; then why doesn’t it just stop falling; why does it not “……continue in a straight line, unless acted on by an external force…..” As that Isaac Newton chap suggested should happen ?
>>
George E. Smith says:
May 6, 2011 at 11:11 am
George E. Smith says:
May 5, 2011 at 1:18 pm
I always thought gravity had an infinite range so that shielding is inherently impossible.
The Earth is in free fall around the Sun and thus does not feel any gravity [except its own], just like an astronaut in free fall about the Earth. “””””
<<
It’s sloppy terminology. I’m giving up correcting statements on this thread, because my corrections have more errors that the original posts. However, even astronauts in free fall feel gravity about the Earth. They have weight which is defined as the acceleration of gravity (at their height). The forces may cancel, but the gravity is still there. This is especially true if you’re in free fall around a medium-sized black hole near the event horizon (or closer). You’ll be dealing with the “gravitational” tidal force which will probably tear you apart even though you may feel “weightless.”
Jim
davidmhoffer says:
May 6, 2011 at 1:50 am
Zeke the Sneak;
“Measurements” is not the best term for this process that was undertaken to make 86 new PhDs and confirm Einstein’s GR. The words they need are “massaging” and “modeling.” IEEE Spectrum:….>>>>
Let’s not confuse the journey with the destination. If I say that I drove to New York, showing that I spend the first two days of the trip going the wrong way doesn’t mean I didn’t get there. They published their results and my understanding is that they showed how they calculated the wobble in order to isolate the data. If there’s something wrong with how they did it, then attack that and show how it is wrong. Citing an early attempt that was later improved upon means nothing in terms of evaluating the final technique.
I am showing how the methodology behind this finding yields nothing near as precise as is being claimed. There is a lot of micetype on the exquisiteness of GP-B’s results and I think people should have a look before getting mesmerised by the press releases and signing for it. 5 years of computer processing on a wobbling gyroscope plus a computer model correction at the last minute when funds ran out for Stanford is a considerable caveat. What does this experiment really tell us?
George E. Smith says:
May 6, 2011 at 11:11 am
then why doesn’t it just stop falling; why does it not “……continue in a straight line, unless acted on by an external force…..” As that Isaac Newton chap suggested should happen ?
That chap Einstein suggests that the Earth follows a straight line [geodesic] in curved spacetime.
Jim Masterson says:
May 6, 2011 at 12:14 pm
However, even astronauts in free fall feel gravity about the Earth. They have weight
I think they would say that they are weighless. You cannot ‘feel’ gravity, only differences in gravity which put stress on your body.
Leif Svalgaard says:
May 5, 2011 at 3:02 pm
It shouldn’t, because all that means is that they learned to understand their instrument, lending more credence to their result.
Understanding is always tempered by wish-fulfilment, that’s why I’m a great believer in everything being simple and plain. OK, I admit getting something round to an atom is far from simple – but the concept of “round” is easy to understand.
The concept of “do a lot of complicated procedures on a pile of crap data until it sings like a canary” is easy to understand too – just in a different way.
I think this ( http://www.creditwritedowns.com/2011/05/confirmation-bias-as-a-feature-not-a-bug-the-facts-dont-really-matter.html ) is quite a good piece – though it may be in a Galaxy Far Far Away from cosmology.
It doesn’t count. You could have the same effect just standing on the floor. In both cases there is a force balancing gravity.
You don’t have the same effect standing on the floor. Go back to the Einstein “man in an elevator” thought experiment. A man in an elevator doesn’t know whether he’s accelerating, or he’s under the influence of gravity. Similarly, he doesn’t know whether he’s falling, or under the influence of magnetism…
You certainly could [e.g. a rocket motor] to prevent getting close to the hole, but once you are inside the event horizon, no force can saved you.
Why? I though the event horizon stopped things getting out, not in. The idea is not to keep away from the hole, but to prevent tidal forces from shredding you. Drop through the event horizon intact, and all sorts of censorship problems disappear.
Yes, but there is an even more fundamental limit. We can not see anything further away than the age of the Universe allows us. Light from a galaxy 1 billion light-years away we’ll never see.
I think you missed my point. Universe is (estimated and rounded – start waving your hands here) 14 billion years old. Therefore we can’t see anything further than 14 billion LY away. Simply because there isn’t light old enough to gone any further. If some part of the universe has expanded at 10 times lightspeed starting at T-2billion years (say) and lasted for 1 billion years (for example), then we won’t be able to see anything of the universe that emitted light between those two time frames. We’ll see older stuff which traversed the “expansion zone” before it expanded, and younger stuff which is before the “expansion zone”, but anything that emitted during the “expansion” will still be travelling. A 10 billion LY gap will take 10 billion LYs to traverse, and it didn’t happen far enough in the past for that.
I would have thought that would have been noticed.
Obviously the whole universe didn’t expand at 10 times light speed but only select areas, as I’m sure many of the older stars would have noticed their bits becoming distant otherwise.
Leif Svalgaard says:
May 5, 2011 at 7:24 pm
A massless photon coming towards a massive body from a given direction will deviate from the usual Newtonian straight line and seem to follow a curved [warped] trajectory.
Well I would point out that a travelling photon isn’t massless – E=Mc^2 and all that. A stationary photon is massless, but since they don’t actually exist, it’s easy to see how you can achieve that little trick.
Though one of the other posters has come up with something that leads to a bit of a poser. If the net attraction of a perfect ball within a perfect sphere is zero – does that still apply if you spin it?
“”””” Leif Svalgaard says:
May 6, 2011 at 1:15 pm
George E. Smith says:
May 6, 2011 at 11:11 am
then why doesn’t it just stop falling; why does it not “……continue in a straight line, unless acted on by an external force…..” As that Isaac Newton chap suggested should happen ?
That chap Einstein suggests that the Earth follows a straight line [geodesic] in curved spacetime.
So all of the planets, and I presume, everything else in THE Universe are travelling in a straight line. I suppose it is the same straight line for all of them. So why do some of them collide into each other now and then ?
Are we all going somewhere or does this straight line, always end up in the same place. Why doesn’t everything just stay in the same place all the time; why move ? What does move mean anyway ?
G. Karst:
At May 5, 2011 at 10:12 am you ask me:
“No particle is born void of velocity. Why do we assume, the universe came out of the big bang, without velocity?? GK”
I answer that no assumption is needed.
1.
A velocity is a rate of movement as observed from a stationary point.
2.
The universe is everything so it cannot be observed to move because there is no external reference point from which to make the observation.
I hope the point is now clear.
Richard
Slartibartfast says:
May 6, 2011 at 9:35 am
Time cannot change by definition.
Again: this needs unpacking. If you’re wondering why you’re being ill-treated, it just might be the glib arguments-by-assertion.
If you seek to illuminate, by all means have at it. What you’ve been doing looks more like trolling, from where I stand.
I explained it already. See comment above on May 4, 2011 at 7:52 pm. It’s a very simple thing really. And it is known to many people, including some relativists. Don’t believe Leif Svalgaard when he says that the earth follows a straight path (geodesic) in curved spacetime. And it does not matter if Einstein said it. It’s all BS because nothing can move in spacetime. That’s right; no time travel, no black holes, wormholes and all that other Star-Trek voodoo physics nonsense.
It’s a devastating truth about general relativity and it’s the reason that you will not hear it from professional deceivers like Stephen Hawking, Brian Greene and the others. They’ve been lying from day one. However, many relativists like Leif Svalgaard here, are just ignorant of this truth. It never fails to catch them by surprise.
Louis Savain:
You have repeatedly demanded answers from Leif Svalgaard.
But you have not answered my polite question to you at May 5, 2011 at 7:02 am.
Please note that my question was a request for you to tell me the errors you think exist in my understandings of relativistic theory which I itemised. This seems a small request when compared to the detailed demands you have made of Leif Svalgaard so I wonder why you have not responded to it.
Richard
Louis Savain:
Please answer my polite request to you at May 5, 2011 at 7:02 am.
It seems a small thing to ask when compared to the detailed demands you have since made to Leif Svalgaard.
Richard
Louis Savain,
There is a good reason for education credentials. If someone has a PhD in Mathematics, we can pretty much rely on what he says, even if we can’t understand all of it.
Dr Hawking, Dr Greene and Dr Svalgaard all have legitimate credentials in their respective fields, so you cannot seriously call them ‘ignorant.’ And just because they may not agree with you does not make them ‘professional deceivers’ or ‘liars.’ I think you need to back off the pejoratives, and accept the possibility that you could simply be wrong.
BTW, what is the extent of your education, and in what field? That will assist in deciding if you should be taken as seriously as those you are attacking.
davidmhoffer says: May 5, 2011 at 10:01 pm
…………..
Thank you for your analysis.
ETH Zurich has exam records.
Facts on record are :
Mileva Maric insisted on ‘any future Nobel Prize money’.
Einstein agreed.
Maric kept her mouth shut for the rest of her life.
Einstein did not keep fully to the agreement.
Einstein: “The secret to creativity is knowing how to hide your sources.”
Smokey,
You are repeating the old “credentials” false argument. It is a favorite of the establishment crackpots because this is how they fool the public into believing that they alone (the crackpots) can understand science and nature and explain it to the rest of us. Just like the high priests and wizards of old. But we are not fooled any longer. We, too, can think for ourselves. Surprise!
The truth is that reasoning has nothing to do with credentials. It has to do with simple logic that everybody can understand. If you cannot understand the simple reasons that I gave earlier to defend my contention that time cannot change and that, as a result, nothing can move in spacetime, then something is either wrong with you or you are one of the deceivers.
I always tell it like I see it.
Juice says:
May 4, 2011 at 4:51 pm
“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.”
Saying space is being “dragged” is an unfortunate metaphor. What is happening is that the geodesic lines are slightly skewed, such that a body with no external force acting on it follows a path which deviates slightly from that which it would follow about a non-spinning object.
Louis Savain says:
May 4, 2011 at 7:52 pm
“A change in time also implies a rate of change which is given as dt/dt, which is, of course, nonsense.
Figure it out on your own.”
The same could be said of a Galilean universe. A path on a circle embedded in two dimensions obeys x*dx + y*dy = 0. Thus, x*dx/dx + y*dy/dx = 0. But, dx/dx = 1. Does that mean one cannot move around the circle, because x is stationary?
ferd berple says:
May 4, 2011 at 9:10 pm
“From the point of view of the folks onboard the spaceship, they have travelled much faster than light.”
How, when it took 13 billion years for the light to reach there? It’s not like they carried the light they see on the spacecraft with them, and got it there in 60 years.
Myrrh says:
May 5, 2011 at 1:01 am
“As with a couple of others here, I still don’t understand what this warping of space time actually is, how does the Earth warp the space time around it as per the diagram since it must be doing so in all directions, unless this is all based on an idea of a flat universe?”
Forget about the diagram. It is only an analogy which is failing to provide you with the correct insight.
Jim Masterson says:
May 5, 2011 at 1:23 am
“It’s harder to show mathematically, but a ring can’t orbit around a star either (as in Ringworld).”
But, it can remain steadily oriented in space through gyroscopic stiffness, and its CG will move approximately with the Star’s CG. Some stationkeeping may be needed to deal with stray forces which act differently on the Star and the ring.
Geoffrey Donald Broadbent says:
May 5, 2011 at 4:12 am
“I just cannot grasp how he imagined the concepts he did let alone convert them to exacting mathematics.”
He stood on the shoulders of giants like Riemann and others. Hilbert actually derived GR first, but graciously allowed Einstein to claim full credit since he got the ball rolling, as it were.
Dan says:
May 5, 2011 at 7:03 am
“If time, as Einstein suggests, does not exist but is only a succession of events, the succession of events like passenger metabolism, nuclear decay etc, will happen at the same rate aboard the space ship as on the earth.”
There is no requirement that it do so. In physics, it is said that whatever is not specifically prohibited is mandatory.
G. Karst says:
May 5, 2011 at 7:48 am
Is it possible to expand space without expanding time??”
Yes.
G. Karst says:
May 5, 2011 at 10:12 am
“Why do we assume, the universe came out of the big bang, without velocity??”
Even in Newtonian mechanics, all inertial frames at constant velocity are equivalent, in that the same physical laws hold in each.
mkelly says:
May 5, 2011 at 10:45 am
Last night on “How the Universe Works” it was said that the laws of physics allow the creation of energy from nothing.”
Yes, you just have to create equal parts pro-nothing and anti-nothing. Why we do not see equal amounts of anti-nothing is a matter of active investigation.
Stephen Rasey says:
May 5, 2011 at 11:21 am
“The Frame Drag is irrelevant in a typical Fiber Optic Gyro, but it matters when the FOG surrounds a rotating planetary mass.”
Yes, but the effect is relatively small. That is why they needed such a precision instrument to see this effect in the first place.
Leif Svalgaard says:
May 5, 2011 at 8:34 am
“Some of the farthest galaxies found have a red shift in excess of 10… which if the galaxy was moving through space would amount to 10 times light-speed.”
That is incorrect. If it were moving faster than the speed of light, we would never see it. This is known as the Horizon Problem.
Myrrh says:
May 5, 2011 at 3:37 pm
“If the mass of the Earth is warping space around it which is what is then pulling in stuff which is gravity, it can only be doing this exactly as in the diagram, on a plane. It cannot be extrapolated to three dimensions.”
Why not?
Myrrh says:
May 5, 2011 at 5:17 pm
“I’m saying that can only be two dimensional, (exactly as in the diagram), because a mass will impinge itself in all directions equally, (if such a thing was happening), cancelling out all the individual impinging on all the points touching the surrounding space, in a three dimensional space.”
You need to integrate the pull over the entire mass. Gravity surrounding a spherical mass behaves externally just as though the mass were concentrated at a single point in the center.
Alexander Feht says:
May 6, 2011 at 4:53 am
“Unfortunately, the article that he recommended as an answer doesn’t contain a single word about how, exactly, the gravitational red shift is being taken into account by the proponents of the Big Bang dogma.”
It is taken into account, but it is much, much smaller than the Doppler shift.
Joe Lalonde says:
May 6, 2011 at 5:12 am
“Changing of circular motion speeds also changes the gravity being felt as now centrifugal force has increased or decreased.”
Changing the speed requires an external force, which alters the orbit predictably.
Vince Causey says:
May 6, 2011 at 5:46 am
“The presence of matter makes time run slower and therefore what is being warped is time.”
Actually, both space and time are warped. Visualizing that is one of the things which makes the subject so challenging.
I think that a clock( including atomic ones) , which is a mechancal device is different from “Time”, i.e time does not change when mechanical devices does. Therefore I think that nothing is “proven” regarding relativistic time by this study. Mechanical devices, not time, are disturbed by speed and gravity.
Harry says:
May 6, 2011 at 3:30 pm
“Mechanical devices, not time, are disturbed by speed and gravity.”
What’s the difference? Time is the rate at which atomic processes – which encompasses mechanical, chemical, and any other process – occur with respect to one another.
Moderator – did my longer list of replies to others get eaten by the spam filter?
Oh, there it is. Never mind…
Should have said cosmological red shift.
responding to Leif Svalgaard @ur momisugly May 5, 2011 at 8:34 am:
I should have pointed out that relative velocity of 98.36% of the speed of light would give a Doppler redshift of 10.
Bart wrote:
Louis Savain says:
May 4, 2011 at 7:52 pm
“A change in time also implies a rate of change which is given as dt/dt, which is, of course, nonsense.
Figure it out on your own.”
The same could be said of a Galilean universe. A path on a circle embedded in two dimensions obeys x*dx + y*dy = 0. Thus, x*dx/dx + y*dy/dx = 0. But, dx/dx = 1. Does that mean one cannot move around the circle, because x is stationary?
Huh? Are you serious or are you just grasping at straws? You realize that dx is not an evolution (change) parameter in physics, don’t you. The only acceptable evolution parameter in physics is dt, a temporal interval.
Me thinks you are one of the deceivers. Thanks for the laughs.
Two days and still running like mad…
Louis Savain is rather dogmatic about dismissing the “dogmatic” views of the establishment… it’s quite interesting really… but it’s very sad to see such religious self righteousness from someone pretending to have the “truth”… oh well…
And in true religious intonations and fervour, “As for me and my house… I name Louis Savain a pushy unimaginative pompous and under educated fraud…”
What say you? … I say “ban the fraud” … but then again I guess all blogs need trolls…
Louis Savain says:
May 6, 2011 at 5:12 pm
Change x to t, then, if you must see things that way.
Really, you are making no sense at all. I think we, you and I, are done.
David Hilbert on the derivations of the field equations: “Every boy in the streets of Gottingen understands more about four dimensional geometry than Einstein, yet, in spite of that, Einstein did the work and not the mathematicians.”
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Andrew says:
May 6, 2011 at 5:48 pm
<ad hominem deleted
You may have an intelligent argument hidden somewhere but I’m not holding my breath waiting for it.
Bart says:
May 6, 2011 at 5:49 pm
I think we, you and I, are done.
Bye.