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NASA Gravity Probe Launched
ping pong writes "Forty-five years in the making and 24 hours late, NASA launched the $700 million satellite into orbit today to test Albert Einstein's general theory of relativity. The satellite, which was inserted into a polar orbit, will spend two months getting ready, then 16 months making measurements." NASA's mission news has more.
could this post be considered a relatively first post?
Did'nt they alredy test this tehroy in a plane with a atomic clock?
We fail to understand the gravity of this situation.
Yeah, I guess I'm funny like that.
It's a pretty fascinating experiment, although it seems like a lot of money to spend just for testing his theory. I think that recent missions to mars were a bit more interesting.
Stanford has a great overview of the mission. It's in pdf format.
Wireless News www.DailyWireless
The experiment uses three key components: a spinning sphere, a telescope and a star.
One of these components can't be had from Sharper Image : can you guess which?
"A door is what a dog is perpetually on the wrong side of" - Ogden Nash
The greatest men are those who keep shaking up the world even after they are long gone. Albert Einstein wasn't a businessman, or a soldier, but look how much research and spending has been affected by his findings. Kudos!
The most facinating tidbit from the NASA article is the absoutely beyond perfect Niobium-coated Quartz spheres at the heart of the ultra-precise gyroscopes.
A quick Google found this link with more cool details, including:
* The 1.5-inch diameter rotors are within 40 atomic layers (0.3 millionths of an inch) of a perfect sphere.
* "Electrical sphericity" must be held to parts in ten million.
* Each rotor spins inside a quartz housing with clearances to the rotor of barely one thousandth of an inch.
* To lift the rotor on earth takes 1,000V. In space, only a fraction of a volt is needed.
* In 1,000 years the gyroscope should barely lose 1% of its starting speed.
* To isolate the gyroscope from the Earth's magnetic field, it will be shrouded in four layers of lead balloons, plus an outer shield of iron.
Plus these cool facts (and a ton more), there are steampunk-styled drawings of the manufacturing process.
Seems like NASA could make some money selling the rejects (you know there are plenty) as the ultimate shooters!
Stressed? Me? Of course not. Stress is what a rubber band feels before it breaks, silly.
"E had just better equal MC squared...E had just better equal MC squared..."
"The experiment uses three key components: a spinning sphere..."
ding ding ding ding ding!
is this going to be like Event Horizon where the probe travels to Hell and back and then kills most of us?
And vanished. It awoke to find itself trapped in other probes' bodies, facing mirror images that were not its own. Its only guide on this journey is Al, an observer from its own time, who appears in the form of a hologram that only the probe can see and hear. And so the probe finds itself leaping from orbit to orbit, striving to put right what once went wrong, and hoping each time, that its next leap will be the leap home
Was this at all offset by any other governments? Seems kind of pricy for research that will freely be shared worldwide, though from the representations Americans get in the news, you have to wonder if they can really trust the data gathered from something built by products of one of the supposedly worst education systems in the world :P
This is an experiment designed to test the correction due to General Relativity of the thomas precession of a tiny spinning sphere.
The correction to the precession will be on the order of arcseconds (1/3600 of a degree) per year.
There are some very good general relativists who have very severe reservations about this project. If they do detect a signal, I suspect it will be more of a testament to the power of experimental precision rather than a test of GR, which practically every serious physicist believes to be correct.
It's also worth noting that if nothing is seen, it's more likely than not due to the difficulty of detecting such a small signal.
Controlling temperature is always a problem in space. I wonder how they're going to keep them chilled like that for 16 months?
In any case, good luck!
Craig Steffen
http://www.craigsteffen.net
I think that Einstein would turn over in his grave if he knew that we were spending 700 million dollars to test one of his theories. Remember, this was the man that came up with some of the most complicated theories in modern physics, and he did it in his head. He used 'geddonken' experiments, and however useful it may be to 'prove' his theories, one has to wonder what he would think...
> will spend two months getting ready
Sounds like my girlfriend.
Norman Cook's Ode to Sl
That is, inertia in big science funding?
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)
All quoting aside, I wonder what will or would happen if the theory of relativity turns out to be nothing but bunk. It wouldn't be the first time our scientists knew something, even if it were based partly on observation. I'm no physicist, but I know Einstein's made assumptions that haven't been proven wrong or right, for example the speed of light in a vaccum is the fastest attainable speed in the universe. Just because we haven't doesn't it doesn't. And what about the unexplainable increase in velocity of the voyager probe as it neared the edge of the solar system? When I read that article, I remember thinking "wouldn't it be great if I was alive to see such a monumental discovery, along the lines of 'the earth ain't flat no more'?" I think it'd be so cool (ok, interesting) if this experiment means we need to rewrite our laws of gravity.
Gravity is a force that effects everything in our universe (and in theory some other universes :P )
:)
It's a force we can calculate for and predict but we still aren't completely sure HOW it works. So whether this mission proves or disproves Einstein's theories we should at least get data that will help bring us a step closer to understanding a significant force in the universe.
I'm really exicited to see the results in 2 years
The James Webb Space telescope, when launched, will be temperature controlled by simply putting a shield around it on the sun-side, keeping the telescope side cool and out of sunlight.
A pretty simple idea; as once it cools down to equilibrium temperature, there'll be nothing to heat it up.
Click here
I hear there's rumors on the Slashdots
Sure, many people argue that communism wasn't "true" communism as Marx defined it. But I'd similarly argue that it's impossible to implement what Marx proposed with homo sapiens.
The Raven
What most people don't know is that it was actually launched last week.
Its experiments of relativity caused it to move close to the speed of light forcing the effects of time dilation to make it appear as if it was delayed 24 hours, when in reality it was launched long before its scheduled date.
That the hope of theoretical physicists is to unite gravity with the other forces, understanding the why and how of divergance, and hopefully uniting quantum dynamics with general relativity (properly fund NASA!, GWB) creating one theory to explain them all.
Needless to say, much will need to be discovered even after a successful GP-B mission.
Whoever said a lead balloon would never float?
This thing was supposed to go up in the fifties, but has been repeatedly delayed, this is very old technology.
Jeez, first the 9/11 probe, now this. Does governmental inquest know no bounds?!
This story is depressing. Gravity brings me down.
In all honesty, this probe won't tell us anything we don't already know. At the time the idea was proposed, it was useful. Since then, we've made more precise measurements of gravity and observed relativistic effects.
The only way this probe will really teach us anything (outside of the engineering that went into its construction) is if it fails, spectacularly. Sadly, those "eureka" moments don't happen very often, and I wouldn't hold out much hope for one here. Then again, the Hipparcos data has caused some debate, while its mission was somewhat routine (although highly precise).
We already know that relativity is wrong (in the same sense that classical mechanics is wrong). This experiment is not designed to figure out exactly how relativity is wrong, rather it is designed to tell us if relativity is wrong at all. Since we already know the answer to that question, it isn't very helpful.
I'm not blaming the guys that worked on this project. There were political/financial/logistical issues that made this launch 20+ years too late to be useful. The PhDs awarded during this project are good, they did some nice work, most notably in materials science and fabrication, but other areas as well. It's just not very meaningful in the areas of physics/cosomology.
Oh well, that's what happens when science is a slave to beauracracy.
Down with Saudi Arabia!!!
Rotating ojbects definitely /can/ affect time and space, as proven by this amazing example.
Newton's Laws of Motion didn't become "bunk" all of a sudden when Einstein (and later QM) discovered holes in it.
The speed of light bit is actually really well tested. It really does take lots more energy to continue speeding things up near light speed, and the trend of that is completely consistent with it taking an infinite amount of energy to get a non-massless object all the way up to c.
Additionally, time dilation is well demonstrated, and it definitely would allow the creation of time machines (something I morally object to :-) if faster than light travel were possible.
Don't get your hopes up.
Sounds like my Girlfrind when we go shopping...
I am become Troll, destroyer of threads
well it *is* 4/20 after all...
-
There's a question I wanted to ask the last time this probe was discussed on slashdot, but alas I discovered the discussion too late to be assured a viable discussion.
Is the presence of frame dragging a forgone conclusion, given that (a) gravity waves do not travel instantaneously, and (b) the moon is able to maintain a stable orbit around the earth, even though the earth itself is in motion?
My college physics were limited to 2 semesters, but I do recall discussions of a velocity component to gravity. To use more severe example than the earth and moon:
Pretend, for simplicity's sake, that the earth's orbit is circular, and is exactly 8 light-minutes in radius. By the time gravity waves reach the earth from the sun, 8 minutes have transpired, and the sun is certainly no longer in the same spatial position that it was 8 minutes prior. This means that earth is no longer orbitting what it "thought" it was orbitting (if you'll excuse the tongue-in-cheek anthropomorphization.) The only two ways I've ever heard of accounting for this are:
(a) gravity waves are not limited by C, and in fact gravity's effect is felt instantaneously
(b) there is a velocity component to the effect of gravity, that takes into account the speed and direction of travel of the object(s) involved.
I think (a) is pretty much out of favor, right? If so, that leaves (b). Thus, velocity matters... regardless of whether that happens to be linear or angular velocity.
Since rotation is angular velocity... does this not imply that frame dragging exists?
I'm definitely interested in replies from Physics whizzes on this one... it's bugged me for a while now.
HSJ$$*&#^!#+++ATH0
NO CARRIER
Errm, maybe this was because BlueUnderwear posted the remark first, and you just repeated it (... and wrapped it up in a lame google link)?
General relativity may surely be proven wrong by the probe's results, but this will not turn it to be "nothing but bunk". So far it successfully passed all tests, which makes it at least a very good approximation (within our current measurement limits).
:w!q
Check the times. I posted mine 17 mins before BlueUnderwear. By the way, this is nothing personal against anyone - I'm just boggled at the mods here sometimes.
Oh yes, and the lame google link ... it may be lame to some, but that doesn't mean that the post is Offtopic, just a failed joke :P
My point is that it's no more Offtopic than BlueUnderwear's musings about Einstein, now is it?
I hear there's rumors on the Slashdots
Here are the possible outcomes:
1) Expected measurements ARE detected. Result: Einstein's theory (which pretty much everyone takes for granted now) is "shown to be correct." Nothing new or earth-shattering, however, is added to our store of knowledge.
2) Expected measurements are NOT detected. Result: Everyone starts wondering "what went wrong" and concludes that something about the experiment was faulty. STILL nothing new added to our store of knowledge, because NO ONE will question the actual hypothesis we are trying to measure here.
Bottom line: Either way, nothing gained. If no one is willing to question the hypothesis based on "negative" results of this experiment, then the experiment itself is pointless.
Alright, disclaimer first:
Just a grad student, still learning stuff, apologies ahead of time if it's wrong.
Attempt at an answer:
"Frame-dragging", as I understand it, goes all the way back to an old theory of the aether, that the aether is all around us, but is dragged by masses so that some oddball features of special relativity is explained. I'm not sure how this applies to the problem here, so maybe people use frame-dragging to refer to something else.
This part, though, how gravity works, is easier. Einstein's theory relies upon the stress-energy tensor. All forms of energy, including energy due to angular momentum and relative motions, are included in this. Binary pulsars precess and their orbits evolve in time, as do their rotation rates, as energy is radiated away gravitationally. There is definitely a contribution to gravity due to what you call "velocity components". Gravitational signals only propagate at c, so don't worry.
You can look at my first 2 posts on this topic if you like, but basically GR predicts that there will be a precession of this little spinning sphere that's very small and hopefully detectable. If we don't detect it, it's probably due to the difficulty of the experiment, not to the failure of GR.
Please use the links on the left to brows thought the image categories. Fantastic!!!
You are not the customer.
We already know that relativity is wrong (in the same sense that classical mechanics is wrong).
I've never heard anything about relativity being proven wrong, please explain further.
a spinning sphere, a telescope and a star Well, if one of these would have been left aside, the production costs could have been used to make a whole movie (2hrs) on the Moon, .. if there remains any land not already sold : )
gtkaml.org
This is complete troll, however, if you actaully think that, you should look into what Marx actually did say.
Im not going to go into it now, however, his ideas have almost never used. There has arguabley never been a genuine Marxist/Communist government. Possibley in Chile, for a short while, under Salvador Allende, untill the US killed him (and put Pinchet in charge to rape the country, and kill whomever he pleased).
Sure, many people argue that communism wasn't "true" communism as Marx defined it.
Amigo, it had nothing to do with it. Trust me. Zero.
"Thats right buddy, the large print giveth, and the small print taketh away."
But the purpose of this project is to determine whether all the predictions of general relativity are correct - something which we don't know yet. If the experiment gives a positive result, general rel is completely confirmed as a correct theory, within its limits of applicability. A null result probably doesn't prove anything, as other posters have pointed out; it may simply be too hard an experiment to perform. So I think this IS a useful experiment, even if only from a dot your i's and cross your t's perspective.
Physicist, consultant, science communicator
Are you sure you're posting on the right site?
I don't understand how time dilation really works. I've seen examples of it, but as far as I can see it appears they all state that time appears to slow down for a fast-moving object relative to a stationary observer. From my admittedly layman's point of view, it seems to me that time slowing down would basically be seen along the same lines as the doppler effect on a moving sound source. I know it may be apples and oranges, but sound and light both travel in waves, correct? I hate making myself sound like an idiot, but I really don't think it's a stupid question, so why wouldn't time for the speeding object appear accelerated if it turned around and came back towards the observer? Wouldn't that cancel out the slowed time for the first half of the journey?
Additionally, time dilation is well demonstrated, and it definitely would allow the creation of time machines (something I morally object to :-) if faster than light travel were possible.
Sheesh. Let me paraphrase our 100 year old counterparts: "the atomic decay we call 'radiaton' is very well demonstrated. If this so called 'fission' device could be built, it would definitly destroy the entire planet."
Our theories simply do not work if somehow we can move faster than light. A more likely explanation to "what happens if I move FTL?" is "you start skipping through space", not "you move backwards in objective-time."
(The effect of increasing speed is a dilation of subjective-time. Theoretical "objective time" [i.e., time as measured by the steady expansion of the universe] stays the same in all instances--we just never have a chance to partake of it, as the sum of human history and experience is all a variety of subjective time.)
Not that I think the science isn't valid enough for NASA to afford this (they've obviously got money to burn) but isn't NASA trying this on as a means to validate their science budget from which they feed?
The manned spaceflight missions have always had the justification that understanding the effects of zero gravity on humans over extended periods was sufficient to secure funding from the NSF and others but zero-G on humans has been tried and tested over the past 40 odd years and is no longer considered of interest to fundamental science.
The timing seems to indicate that NASA wants to show it can carry out fundamental science experiments even if the results aren't relevant to modern questions in fundamental physics. They even go so far as duplicate well accepted results in a field that has progressed well beyond the best precision of GP-B.
From this link;
I worked as a consultant for the company that was awarded the contract for working on the zerodur glass block that made up the housing for the gyros. They brought us in to try and teach machinists optical fabrication. The tolerances needed for this thing were unbelievable, extremely tough even for a master optician. They manufactured 3 housing blocks, one of them was destroyed during the rough machining process, and an optician trainee who was attempting to polish one of the precision lands with a weighted polishing lap by hand fractured the second. They trusted the same company with the second block to complete the polishing process. They had limited experience with any sort of optical fabrication, and the specs they were looking for were way, way beyond the capabilities of this shop. I felt really bad for the guy, who was absolutely sick with himself after the accident, and perturbed with Stanford University with giving the polishing operation to this shop with very little expertise in optical fabrication. This block had a million plus in material and man hours prior to the polishing operation, wiped out with one bad stroke
Heh. Stuff you don't hear about on NASA's website.
Take the cheese to sickbay, the doctor should see it as soon as possible - B'Elanna Torres, "Learning Curve"
"It's been a long road..."
Zhrodague.net - I do projects and stuff too.
I know this is
GP-B is *designed* to do just that, with adequate [costly] equipment, and directly measure FD with unquestionable accuracy. Also, a sanity check is always necessary.
Proof: find it in the other 2 (?) articles about GP-B... Look for LAGEOS and LAGEOS II (the other meaurement is linked in parent article)
</rant>
Well if I belive in god does god exist?
A belief is just that a belief, prohaps the're all wrong, you'll never know until there's a proof.
What are you talking about, clearly the only true paradise is your momma's coochie. Take it from me, I have visited paradise many times.
Ummmm.... if the results affected GPS in any way at all, we would have already detected (or not) the effect via... wait for it... GPS! So even without knowing anything about GR or GPS you can deduce that the results of this experiment mean nothing for GPS.
There is no forseeable practical benefit to this. Perhaps in the far future there will be, but at the moment it is purely an issue of science.
You're a Brit, right?
I think I read that General Relativity and Quantum Mechanics have self-consistant but mutally exclusive explanations for gravity. At least one theory must be wrong.
I guess there can be only one.
I'm glad to see that gravity is a field that attracts all the finest scientific minds.
When all you have is an axe, everything looks like a grindstone.
If the experiment goes as planned and detects measurable precession, the specific data could be promoted as a valuable piece of military inteligence to make aiming devices, tracking weapons, and positioning systems just a bit more accurate than anyone else on earth (One press release did say that the results weren't being publicly released; just the general findings). Which of course leads to more funding of similar experiments.
If the experiment produces an unexpected result, but not due to obvious failure of the devices then the loudest voices arguing will be the scientests favoring a revolutionary overhaul to Einstenian physics. The more conservative scientests who say that devices just aren't sensitive enough to detect it will be lost in the noise. And the noise will lead to a call for more funding for more experiments.
If the experiment fails due to gross component problems, NASA can argue that they need much more money to fund even their most basic experiments. Not a good situation with all of the failures in recent history, but if people still want to go back into space the justification for more funding would be strong.
I haven't heard anything from this last group, but if you start hearing any codenames in the project or popular explanations for frame dropping using terms from like Isaiah or Joshua from the Bible (and their ability to apparently have an unexpected effect on solar gravity) then you'll know there's a strong political effort to win the appeal of the religious statesmen in our government... and by extension, win more funding.
Let's hope that my attitude about political vectors in funding this experiment now is far more cynical than the reality.
Well, im glad they finally did something..I just hope that the guy that designed this crap in meters remembered to program the craft in meters... Dont need a repeat of the mars lander a few years ago when the thing hit Mars at a constant velocity of 225mph..WHOOPS, there goes 200 million......Alas, another 420 project..
I agree with everything that you have said, factually.
However, there is much room for a similar line of research to be done in the future that is very much like this.
Outerspace gravity experiments can do soooo much more than Earth based ones. Things like detecting gravitational waves at different energy ranges, !detecting the Axion!, and probing gravity at small ranges to detect the compactified dimensions of string theory.
Hopefully this can pave the way for the real stuff.
A Usenet Troll Triumphs on Slashdot
Nope, you posted yours 17 mins after BU. You need to remember: Einstein's brain is spinning so fast in its jar that not only it spills out all its formaldehyde, but also drags along the Slashdot frame of reference so much that time flows backwards!
Of course, by far the more interesting case is if the effect is not observed. They seem to have many sigma of signal to noise here, so a null result would be pretty compelling.
9
The Lense-Thirring effect has been observed: http://www.iop.org/EJ/abstract/0264-9381/17/12/30
There is no null result. However Gravity Probe B will increase the accuracy of the measurements DRAMATICALLY. Progress in physics has always been made by:
1. new ideas
2. high accuracy measurements allowing to discriminate between those ideas
This is why we have a bunch of new candidate theories like string theory and supersymmetry, which seek to bridge the gap between the two major theories. We don't know which of them (if any) is right, but we know that relativity and quantum mechanics must be wrong or incomplete.
Terribly sorry, but it was an easy shot.
Karma: It's all a bunch of tree-huggin' hippy crap!
Your site does demonstrate how open to free speech America is, though, since in Europe you would long since have been shut down. And maybe with good reason, because the values your site implies support for are dangerous. You may think it's funny stuff, but some crazies actually believe these things, and they mustn't be encouraged. Maybe if you had actually come into contact with racism in your life, you would take it more seriously.
Comment removed based on user account deletion
From the article A Near-Perfect Gyroscope provided by another poster:
"Mechanically, the 1.5-inch diameter rotors are within 40 atomic layers (0.3 millionths of an inch) of a perfect sphere, rounder than anything within many light-years distance from us....Only neutron stars are rounder."
Now I know that here on slashdot such things as neutron stars are always only a synapse or two away from our collective consciousness, but I have to say that reading those words sent a shiver up my spine. A sentence that would feel right at home in an Iain M. Banks novel is being used to describe something happening right now.
Cool.
Its not testing Einstein's "general theory of relativity," his special theory, or even his favorite recipie. Its testing Frame Dragging, which is a theory derived from Einstein's theories, but that was in fact originally postulated by physicists Joseph Lense and Hans Thirring 4 years after Einstein's theory.
The signifigance of it is that it is the last major derived theory from general relativity that has yet to be proven via experiment. This particular experiment was devised back in the 40's, but never got "off the ground" (pardon the pun) until now.
Due to the warping of space by the mass of the earth an orbit is about 1" smaller than PI times the diameter. Very small, but potentially detectable effect.
The frame dragging page on wikipdia already includes the following:
The Gravity Probe B experiment aims to detect any frame-dragging effects in its orbit around the Earth with high precision. It was successfully launched on April 20, 2004 for an 18 month experiment.
How's that for being up to date!
The opposite of gravity is levity. Therefore, if enough posts are moderated +5, Funny, the Slashdot servers will achieve enough levity to launch themselves into orbit.
/.'er can do their part by posting more "welcome our [blank] overlords", "In Soviet Russia...", and Underpants Gnome business plans.
Every
If we work hard enough, Slashdot may take out the X-prize!
Why offtopic? censoring won't make them dissappear, and killing that amount of people was the reason why the US funded research in that field, and made that formula famous.
Denial is not going to bring murdered people back.
"...it will be shrouded in four layers of lead balloons..."
That should go over well...
Didn't Isaac Newton and Galileo prove this on earth like a thousand years ago? And we've known since the 60s that there isn't any gravity in space. So it seems pretty obvious that all this money is being spent just to demonstrate something that's already proven. I can't believe that NASA is spending our money on this when they could be building a colony on Mars.
The only way this probe will really teach us anything (outside of the engineering that went into its construction) is if it fails, spectacularly
Considering the price ($700 mil), I think any failure would be considered spectacular. Spectacularly bad. At least we will get some fireworks when it re-enters, no matter what.
If you open your mind too wide, people will throw trash in it.
Hmm. I wonder what keeps the earth in orbit around the sun.
Of course there's gravity in space. Astronauts in orbit don't feel any gravity because they're constantly in free-fall. Their tangential velocity is just high enough that they fall "around" the earth.
This NASA probe isn't designed to tell us whether there's gravity or not; it's designed to test an application of Einstein's general theory of relativity which states that gravity can bend space-time. See this for more info.