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NASA Gravity Probe Set for Launch
The Real Dr John writes "NASA announced
yesterday that its longest running program, Gravity Probe B, was ready and
scheduled for launch on April 17th. The project has taken 44 years to complete,
at a cost of approximately $700 million. The reason for the high cost is that
the probe contains the most sensitive gyroscopic equipment ever created, which
will be used to test Einstein's theory of gravity. Einstein predicted that the
gravity created by a large body warped space-time, but he also predicted that if
the large body was rotating it would create a drag effect on space-time
known as frame dragging. Gravity Probe B will be able to test
Einstein's theory using Earth's relatively small gravitational field because the
instruments are so sensitive."
Seems God plays roulette even if he doesn't play dice.
The slightest bit of interference could deem it unusable data with as much precision the gyroscopes will be operating. I have a feeling that even interference they are not thinking about (who am I kidding, this is nasa) such as solar radiation, and the magnetic north shift (which as of late, has been about 10 miles a year) will alter the results of this test dramaticly.
-- johntracy.com, because everybody else is wrong.
i viewed the elegant universe, the other day by brian green, and am currently reading the text, much has changed in theory over the last 44 years, string theory for one, currently holds the possiblility that gravtiy strings are looped and therefore capable of jumping from our current brane/dimension. will this allow and or test for this theory or is the device antiquated before deployment? I guess thats a risk involved with such a long dev cycle. hopefully it will take this into account, or has the CERN project already made this redundant?
The earth is a mass-energy. According to General Relativity, as a mass-energy, it should create a little dimple in the local space-time fabric. It is also theorized that the daily rotation of the earth causes a twisting of the local space-time fabric. This effect is known as frame dragging and it should manifest itself as a force that pushes a gyroscope's axis out of alignment as it orbits the Earth. [GP-B will be using four small, incredibly precise gyroscopes as its main tool for detection of relativistic effects on the local space-time fabric.] Gravity Probe B will attempt to measure the force, gravitomagnetism, giving scientists an important insight into how it might affect objects that are much larger than ping pong balls, such as black holes. At the same time, the gyroscopes will experience a much bigger force - the geodetic effect - which is a result of the warping of space-time predicted by Einstein. This force will tend to push their axes in a direction perpendicular to the frame-dragging effect which allow it to be measured separately. The geodetic effect is hundreds of times bigger than frame dragging and the experiment should measure its size with an accuracy of 0.01 per cent the most severe test of general relativity ever undertaken.
-- johntracy.com, because everybody else is wrong.
Einstein predicted that the gravity created by a large body warped space-time, but he also predicted that if the large body was rotating it would create a drag effect on space-time known as frame dragging.
AAagh! Mental images of my ex dancing! *SHUDDER!*
NASA announced yesterday that its longest running program, Wooden Block B, was ready and scheduled for dropping off the Empire State Building on April 17th. The project has taken 44 years to complete, at a cost of approximately $700 million. The reason for the high cost is that the probe contains the most expensive wood ever created, which will be used to test Newton's theory of gravity. Newton predicted that an attractive force known as 'gravity' will act between any two bodies. Wooden Block B will be able to test Newton's theory using Earth's gravitational field, and a very tall building.
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That project has been kicking around Stanford for decades. I saw that satellite under construction almost twenty years ago. It's basically a subsidy program for PhD students, not a satellite program. If that job had been outsourced to Hughes or Loral, it would have launched decades ago.
Gravity Probe A was the launch of an atomic clock on a suborbital rocket, designed to measure time dilation as it passed into weaker areas of gravity.
I believe it was done in 1976
Frame dragging occurs when a massive object is rotating. It turns out that a when a body rotates, it 'pulls' the surroundng space around in the direction of rotation. This means that if you drop an object toward the rotating body, it will not just fall radially tooward the centre but will aquire a component of velocity tangental to the surface.
Of course, this effect also applies to light rays, so the question of what one would actually see is a bit tricky.
Another situation that 'frame dragging' alters from classical theory is orbits around the body. Imagine an observer fixed at a particular set of coordinates in orbit around a rotatng body. If they send photons in orbits around the body opposite directions, they will not be recieved at the same time; that which travels in the direction of rotation will arrive sooner than that travelling in the opposite direction. In extreme cases, it is possible that the photon opposing the direction of motion, although locally moving at the speed of light, won't appear to move at all from the point of view of a distant observer.
I found the following quote especially interesting:
Francis Everitt, the principal investigator of the project, said: "Aren't Einstein's theories all established and confirmed? After all it was 50 years ago that Einstein himself died and it's 100 years next year when he developed his first theory of relativity. Don't we already know it all? The answer is no."
I wonder what other theories that are generally accepted throughout the scientific community have not been completely tested and/or verified. And, quite frankly, I'm surprised that there isn't much more VC and grant money available to go and do research on stuff like this. Afterall, these projects are quite prestigious.
In addition to the sensitivity problem, I wonder if this could be an experiment whose time has passed.
In 1995, the GP-B was described as the "only experiment ever devised to test [the existence of frame-dragging]."
However, in 1997 NASA announced that it had successfully tested frame dragging. See also here.
Only Women Bleed (Sex, Sharia remix)
See article
Professional Wild-Eyed Visionary
They should launch anti-gravity probes. Wouldn't even need rockets and save us taxpayers some bucks.
Table-ized A.I.
From the article :
Since the project was conceived by three scientists after a naked midday swim at Stanford University's pool, more than 1,000 people have worked on the satellite. Two of its founders are dead. More than 90 people have earned their doctorates working on the project.
Naked physicists... wow... with the current administration in charge, this project would have never been approved.
Oops.
You are right. The gravito-magnetic force acts perpendicularly not tangentially.
This guys post is taken from another discussion and another Slashdot user. Verbatim.
He's a troll relegated to 0 karma land, and desperate for anyway out.
See UID's comment on his post: here
Don't let this guy walk off with 5 mod points for such a stupid trick.
-Malakai
A Dragon Lives in my Garage
... the project that ate Stanford.
:)
When I was a grad student there, we had a running joke that nobody could get an astrophysics degree without selling at least a piece of their soul to Francis Everett, the chief booster for this project.
I was there when a rogue group suggested that, in the intervening four decades, technology had advanced enough to do the frame-dragging experiment with a laser-coordinated satellite net for half the cost.
We also circulated the "fact" that the GP-B launch date slipped by about 1.05 days per day. A friend defined it as a new universal constant for project overruns...
The Mongrel Dogs Who Teach
Couldn't gravitational lensing be a possible means for testing frame dragging?
Assume frame dragging exists. If you can find a body that does the gravitationaly lensing and if that body rotates, then the light rays you see coming from the multiple lensed images might produce an interference pattern.
To-do List: Receive telemarketing call during a tornado warning. Check.
Theoretically, yes.... there's a recent paper that works out the numbers for lensing from a spiral galaxy, and it's roughly on the order of a few micro-acroseconds. Possibly detectable by SIM or GAIA.
[TMB]
Hmmm. When World War II broke out, the US had discovered that, while its tactics with torpedos were more or less sound, they came to naught -- because the actual torpedos had this nasty habit of breaking apart on impact, rather than (say) exploding. It took two years (and who knows how many lives) to get that problem fixed.
The general rule seems, to my reading of history, to be that the military tends to be effective but not necessarily cost-efficient. Or put another way: Throw enough money at any technological problem and it will be solved. People tend to be freer with the gobs of money if they think it's related to national security.
The Mongrel Dogs Who Teach
Hubble has had a pretty good look at the spectra of supermassive black holes at the ceters of local galaxies. With a nice close look at those centers, there is turbulences, physical discontinuities in the acretion disks around the supermassive black holes, and the only good candidate for the phenomena is frame dragging...
I mean it'll be cool to see if the numbers and the phenomena match, but it's not like there's going to be wild surprise.
Genda
Bold is me, italics is parent.
LATOR is capable of testing string theory, an exciting but so far merely theoretical development in high energy physics.
Or rather, it might conceivably be capable of testing some rather speculative models within string theory; there are plenty of other string theory models that LATOR can't test, and no good reason to believe in one over the other. That's one of the problems with string theory: it's too flexible. People can cook up all sorts of artificial string models, but that doesn't mean that any of those models are likely to be true, even if string theory itself is true.
It will test some of the most reasonable/popular models, which is a big step up from having never been tested at all.
LATOR also seems to be much more accurate,
It is, but it's also a test of something that we've already measured extensively (albeit much more sensitively). Our existing measurements of frame-dragging are extremely crude.
Quoting this page:
As you can see, you were mistaken.
and less likely to receive interference.
Why? And, so what? (Unless you're suggesting that GPB will receive so much interference that it won't work.) All it takes is a little bit of interference and the whole thing doesn't work at all, it's so darn sensitive. LATOR is less mechnically intensive.
I do hope that this experiment works out, however as other posters have mentioned, there only has to be one unexpected source of error to totally screw this up.
The same is true of LATOR or of any other experiment, especially highly sensitive ones.
LATOR's architecture is much different, and I believe by using a long baseline etc, it makes it difficult for interference at one end to screw up the entire experiment. Also remember that it's something that's fairly time invarient, whereas precession is not. The architecture of LATOR seems more likely to deal with sources of interference than something that's based primarily on mechnical components.
But I haven't done the actual math for either, so what do I know?
Cheers,
Justin