NASA Gravity Probe Set for Launch 250
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."
Einstein was a (gravitational) drag... (Score:5, Funny)
Re:Einstein was a (gravitational) drag... (Score:5, Funny)
Ouch! Hey what's with the tomatoes?!
Re:Einstein was a (gravitational) drag... (Score:2, Funny)
Quantum Mechanics 101: If you have there is a possibility of something happening and not happening, it will both happen and not happen.
Re:Einstein was a (gravitational) drag... (Score:2)
Who knows what that will bring? Would even God know?
Too sensitive (Score:5, Interesting)
An experiment whose time has passed? (Score:5, Interesting)
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] [sfsu.edu]."
However, in 1997 NASA announced that it had successfully tested frame dragging [sfsu.edu]. See also here [scienceweb.org].
Re:An experiment whose time has passed? (Score:3, Informative)
Sorry to follow-up on my own post. Caught a link error. I stated:
That should instead read:
Re:An experiment whose time has passed? (Score:2)
Not this is an observation, not a TEST. So the two statements are not in conflict. We an observe a thing, but to test for it is to demonstrate a higher order of understanding.
Re:An experiment whose time has passed? (Score:2, Informative)
Anyway, while we do have astrophysical tests of frame-dragging, they're not direct. There's a big difference between trying to infer the effect by observing the orbits of matter outside a black hole, and actually putting a gyroscope into a frame-dragging field and seeing what happens to it. In particular, direct measurement is much more sensitive. Astrophysical tests can merely suggest the existence of frame dragging. GPB can quantitative
Re:An experiment whose time has passed? (Score:2)
Not quite the same thing.
Re:Too sensitive (Score:5, Informative)
Just about all of the engineering that's gone into the project is to eliminate interference from everything else; those gyros are going to be just about the best-isolated objects we've ever made.
Yes, they need to account for solar wind, as well as atmospheric drag, as small as it is at that height. This is done by flying the satellite drag-free; one of the gyros free-floats inside its housing, and if it starts to drift off-center, the satellite fires its thrusters to reposition _the satellite_ so that the free-floating gyro is again in the center of its cavity.
This way, any external force on the satellite can be removed, since the gyro is shielded from them by the bulk of the satellite, and the satellite then follows the gyro on a perfect gravitational orbit.
Magnetic fields are filtered out to some ungodly factor; the leftover fields inside the science probe are on the of 10^-17 gauss.
They also account for micrometeorites, electric noise, and many other error sources. There's a reason this has taken 40 years.
Re:Too sensitive (Score:3, Interesting)
Re:Too sensitive (Score:5, Informative)
But it looks like to me that LATOR is a very-high precision test of what's already been tested several times: the exact amount of curvature of spacetime that heavy objects create.
GP-B tests the effects of frame dragging, which is a completely separate effect.
As to SUMO, I wouldn't be able to say what kind of effect a Lorentz-transform symmetry breaking would cause, and whether GP-B's results could be affected by that. But the tests seem to be fundamentally about clock rates at various moving frames, which is more of a special relativity test (as the Loretz transform comes from special relativity). GP-B is about general relativity, and specifically about spin, which seems to be relatively untested ground.
Re:Too sensitive (Score:2, Interesting)
The magnet example was saying this: if you're an observer inside a magnetic substance, you will notice a "preferred direction": the direction the spins in the magnetic are pointing. Thus, there will be a "preferred observer" or "absolute reference frame": one oriented in the same direction as the spins. An observer inside the magnet can absolutely determine whether he is in such a frame:
Re:Too sensitive (Score:2, Interesting)
Will it be using a high or low, circular or elliptical, equatorial or inclined orbit?
(i'm sure the info is at the GP-B site, i just missed it)
The electrostatic suspension system also reminds me bit of a Stargate SG-1 episode, Serpent's Venom.
kudos and good luck. You launch on my birthday.
Re:Too sensitive (Score:5, Informative)
And yeah, it's superfluid helium, enough for about 18 months given the boil-off rate (it boils off continually to maintain dewar temperature; the boiled-off gas is actually used in the precision manouvering thrusters)
And the suspension system is a rather scary system... it has to ramp from barely touching the gyros to making sure they don't impact the cavity walls when a micrometeorite hits almost instantaneously. And there's only about a millimeter of clearance there. And the gyros spin at 10,000 rpm. You don't want them touching the walls.
Re:Too sensitive (Score:2)
I seriously don't think an arm-chair physicist can take this project down. Whatever you think of, they've already thought of it.
Re:Too sensitive (Score:2, Funny)
Re:Too sensitive (Score:2, Funny)
Woohoo! A new one: IAPP/IANPP!!
Not so sure... (Score:2)
Airlines still hold onto the "no cell phone inside" because this is far easier than differenciate old and new aircraft models, and I suppose this is far easier than convince insurance or the other passenger.
Re:Not so sure... (Score:2)
The tin-foil hat part of my brain wonders if airlines are afraid that someone'll be on the phone when, say, an engine falls off or the pilot commits some tragic error. The bad PR could cost millions...
Karma fishing... (Score:5, Informative)
He's a troll [slashdot.org] relegated to 0 karma land, and desperate for anyway out.
See UID's comment on his post: here [slashdot.org]
Don't let this guy walk off with 5 mod points for such a stupid trick.
Re:Too sensitive (Score:3, Informative)
I thought this was debunked by the 9/11 commission several months ago. [washingtonpost.com] The boxcutter meme spread like wildfire, and everyone "knew" before the day was out that this was done with boxcutters. But it turns out that only one plane had a boxcutter sighting (relayed via cellphone). They actually used Mace, knives, and bomb threats. I suppose it's possible that "knives" might have been a reference to boxcutters, but we have no further evidence to support i
Gravity dragging? (Score:3, Informative)
I think we're all familiar with time dialation (if you haven't read "The Elegent Universe", you're missing the best explanation of *why* time dislation occurs that I have ever heard), but what is frame dragging? What kind of effects does it have on the observer?
Re:Gravity dragging? (Score:5, Informative)
Re:Gravity dragging? (Score:2)
Mods, How about helping the guy out?
Lense-Thirring effect (Score:5, Informative)
See article [wolfram.com]
Re:Gravity dragging? (Score:5, Interesting)
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.
Re:Gravity dragging? (Score:2)
Lire Real's engine?
Re:Gravity dragging? (Score:4, Interesting)
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.
Re:Gravity dragging? (Score:4, Informative)
Theoretically, yes [sciencedirect.com].... there's a recent paper [harvard.edu] 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 [nasa.gov] or GAIA [estec.esa.nl].
[TMB]
Re:Gravity dragging? (Score:3, Interesting)
You may be aware that elctricity and magnetism are intimately connected. In one sense magnetism is an extra force that moving electrical charges exert on other moving electrical charges.
Einstein discovered that gravity can work much the same way. Moving gravitational charges (i.e. masses) generate an extra force on other moving masses. This extra force is sometimes refered to a gravito-magnetism and is usually v
Re:Gravity dragging? (Score:5, Informative)
You are right. The gravito-magnetic force acts perpendicularly not tangentially.
Interesting... (Score:2, Interesting)
More interestingly enough, what can we use this for? No, this isn't sarcasm, but how can we apply these scientific principals to help our daily lives and to understand the universe better?
Comments anyone?
Re:Interesting...Spinoffs. (Score:2, Informative)
Re:Interesting... (Score:2)
Also, there is some disagreement how much the theory of relativity is useful for predicting the sattellite behavior (meaning the real world departs from theory).
Gravity Probe A (Score:2, Interesting)
(sorry had to ask)
Re:Gravity Probe A (Score:5, Informative)
I believe it was done in 1976
Re:Gravity Probe A (Score:3, Funny)
Re:Gravity Probe A (Score:2)
So what happend to Gravity Probe A?
In that one they put six gyros, and the damn thing just disappeared. Nobody's seen or heard anything of it in a very long time.
considering string theories (Score:5, Interesting)
Re:considering string theories (Score:5, Informative)
No, it won't serve as a test of string theory braneworld scenarios, and no, that doesn't make it "antiquated", either. There are lots of reasons to do the experiment, other than its ability to verify somebody's speculative pet theory. (Heck, string theory doesn't even predict that our universe is confined to a brane; it's just a possibility within string theory.)
The point of GPB is merely to test the accuracy of general relativity's predictions. If GR is wrong, there are many ways it could be wrong, and thus GPB might be able to tell us which way is correct, or rule out alternative theories that predict effects that aren't measured.
Re:considering string theories (Score:2, Informative)
Re:considering string theories (Score:2)
Re:considering string theories (Score:2, Funny)
Re:considering string theories (Score:2)
Translation of parent post: "Since we can't use the math for string theory to build a bomb, we're not going to believe it until such time as we can use it to build a bomb."
(Correct me if I'm wrong, didn't Einstein get laughed at until the development of the atomic bomb?)
Posted by Bill Gates: (Score:2, Funny)
Did I mention that my car is a Maybach 62, which costs $380,000? With an expensive car like that, you want to make sure the upholstery doesn't get dirty.
And in other Gravity Probe B News. (Score:2)
And in other Gravity Probe B News [google.com].
Eww! (Score:4, Funny)
AAagh! Mental images of my ex dancing! *SHUDDER!*
Re:Eww! (Score:3, Funny)
With CowboyNeal. NAKED!
Bureaucracy (Score:5, Funny)
Re:The real source of the problem (Score:2)
The main problem with NASA is lack of funding. The military has a similar problem (think about how many people they employ and what they have to buy before you flame that), but they still change when a better system is invented.
Maybe if we got rid of welfare and medicare/medicaid we could fully fund NASA.
When the mensch find they can vote themselves bread and b
Re:The real source of the problem (Score:4, Insightful)
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.
Re:The real source of the problem (Score:2, Insightful)
But it cost a few billion bucks. GDP-wise, it was probably the largest project in US history. But such a pretty cloud!
Re:The real source of the problem (Score:2)
Finally! (Score:4, Informative)
Re:Finally! (Score:2)
So I take it the professor running it is planning on retiring soon?
Re:Finally! (Score:2)
Ignoramus (Score:2)
Re:Ignoramus (Score:2, Informative)
The impact on science is quite straightforward. as this is science. Science is about testing theories. Without that, science is just a religion.
GR predicted that Newtonian mechanics are too simplistic. This is one of the tests that verifies this. Anyway, any applications of this test are another 50 or 500 years away. Just like the applications of discovery of electrons (typing away on my electron machine).
Wow (Score:2)
45 years prep time... woo (Score:5, Informative)
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.
Re:45 years prep time... woo (Score:4, Insightful)
All of them. It's not possible to perform every test of a theory that can be performed, nor is it possible to perform any given test to an arbitrarily high precision. There are tests of quantum electrodynamics that are accurate to 11 decimal places, but people still test QED, because we never know whether it goes wrong at the 12th place, or whether there's some new phenomenon that QED doesn't predict. Likewise, there are many tests of general relativity, many of which are very accurate, and nobody doubt's the theory's general validity --- but that doesn't mean that there might not be small deviations out there that point the way to an even better theory.
Re:45 years prep time... woo (Score:3, Insightful)
If it takes $100 million to find mistakes in the theory, there is very little practical incentive to research it, since more than likely it will take many times $100 million to exploit any of those newly discovered differences for practical gain. Put another way, if existing theories are good enough for all but the most precise
Re:45 years prep time... woo (Score:2)
Interesting opinion, but you are just shuffling the cost off to later generations. Say for example gravity control comes out of discovering a error in relativity. Is that worth it?
I don't think that's what he was talking about. Instead, I think he was trying to explain why there aren't any venture capital funds to fund scientific research. Well, duh. If it's called "venture capital" that means it's used in "capitalistic ventures", and science is not a capitalistic venture.
Re:45 years prep time... woo (Score:2)
Einstein's theories have been heavily tested and IIRC, so far hasn't been found to be invalid. There are other theories that explain the way things are. Einstein's theories I think are most accepted because of how well it tested so far.
VC money is much more about return on investment than prestige. Funding science projects doesn't normally bring much money or prestige, IMO.
Re:45 years prep time... woo (Score:2)
Einstein also said that nothing could travel faster than light, maybe we will get to test that someday ?...
Re:45 years prep time... woo (Score:4, Informative)
All of them.
It is not possible to completely test and verify anything. That's the nature of reality. A theory is defined as an explanation that has been thorougly tested and is widely accepted by people knowledgable in that field, but it's an essential part of science that nothing is ever proved beyond all doubt; there is always room for change if additional data comes to light, or a better explanation for existing data is devised.
One of my pet peeves is the common misuse of "theory" to mean "hypothesis" -- an untested conjecture. This popular misconception then leads to scientific knowledge being dismissed as "it's only a theory" by people who don't understand what a theory actually is, and assume that the Theory of (fill in the blank) is a mere hypothesis.
Re:45 years prep time... woo (Score:2)
VC money is all about ego and self. I don't think you'll see any VC money go to this.
However, you'll certainly see VCs making money off of projects like this.
Anti-gravity probe? (Score:3, Funny)
NASA or Stanford? (Score:2)
Every article I found about it on NASA ends with "For more information, visit http://einstein.stanford.edu/".
There was a test (Score:2, Insightful)
unclear whether it's worth it (Score:3, Interesting)
Re:unclear whether it's worth it (Score:2)
Re:unclear whether it's worth it (Score:2)
When was the last time you dug in your yard to see whether there was a buried treasure there? I bet you haven't: you make the reasonable assumption that there is no treasure buried there and digging costs valuable time. Until you receive additional information, the cost is simply not worth the expected benefit.
Well, if some renowned physicist showed up with some excellent math demonstrating that there must be buried treasure in my yard, it's worth a day's work to dig it up and test his hypothesis. Wouldn
Naked Physicists... (Score:5, Funny)
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.
Very Cool Experiment (Score:3, Interesting)
And probably not much more expensive.
LATOR is capable of testing string theory, an exciting but so far merely theoretical development in high energy physics. LATOR also seems to be much more accurate, and less likely to receive interference.
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.
Cheers,
Justin Wick
Re:Very Cool Experiment (Score:2, Interesting)
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
Re:Very Cool Experiment (Score:4, Interesting)
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
Take that, Space! (Score:2, Funny)
Sorry for sounding trollish (Score:2)
Re:Sorry for sounding trollish (Score:2)
yes you are sounding trollish because you don't bring up any reason for not using the german refinery which might very well have been the only one in the world capable of the job.
-
Ah, GP-B.... (Score:5, Funny)
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...
Need Another Sensor Array (Score:2)
Wow. (Score:2)
Quantum Gravity (Score:2)
ThinkGeek (Score:2, Funny)
The is already good evidence of frame draggin... (Score:4, Interesting)
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
Ok - mod me down if you want but I have to post it (Score:2)
It won't bend over, it won't spread-em, and it doesn't care how sensitive those damn machines are.
I also want to know who's going to be up there pulling all of those strings on those gyros!
(There! I feel much better now! I know it's stupid! I can hear you groaning out there - but I just had to post it!)
Project LISA, does NASA believe Einstein? (Score:2, Informative)
LISA
LISA is an ESA-NASA mission involving three spacecraft flying approximately 5 million kilometres apart in an equilateral triangle formation. Together, they act as a Michelson interferometer to measure the distortion of space caused by passing gravitational waves. Lasers in each spacecraft will be used to measure minute changes in the separation distances of free-floating masses within each spacecraft.
The LISA mission is designed to search for and detect gravitational radiation
Re:Project LISA, does NASA believe Einstein? (Score:2)
First, I would not call it all of a sudden. Testing theories with experiments is one of the building blocks of science.
So much as Einsten's theories are concerned, since the very day he published his theories, other scientists have analyzed and thought of ways to test them. They have done so where possible, as technology has permitted. One example is the atomic clock and moving bodies experiments that have been done in the past.
It is necessary
Re:Hopefully the start of another space race (Score:2, Informative)
Re:Is it just me? (Score:3, Insightful)
Re:Is it just me? (Score:2)
Forever Peace, by Joe Haldeman explored that idea (among others) in this book. Quite well written too, IMHO.
Re:Is it just me? (Score:2)
Seriously, though, I'm more worried that some cave dwelling foul-smelling individual will blow up an observatory in protest encouraging all the other cave-dwelling foul-smelling individuals to blow whatever it is they think is destroying the society they are not even members of.
Re:Lets hope it works! (Score:2, Interesting)
Duke Nukem Forever (Score:3, Funny)
Re:This is just weak field gravity (Score:3, Informative)
Humm, methinks you may well have the black hole physics part of it backwards. One thing we get damned little out of a black hole is information about its characteristics. We can get a general, plus or minus 20% guess on its mass by measuring the orbital velocities and distances to all the other stars in the locality.
The only other tidbit of info we can eek out of the observations is the miss-match between expected velocities of the really nearby s
Re:This is just weak field gravity (Score:2)
Re:what a waste of a cool probe... (Score:2)
There are a huge number of problems with sending a probe like Gravity B to Saturn or Jupiter. Not the least of which is unknown variables that could make the test useless.
With the earth, all the variables that can affect the probe have been studied and mitigated to high degree.
Then there is all the extra cost of sending the probe to another planet.
So it doesn't make sense t