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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?
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?
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.
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.
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
Hey, but at least it is the most expensive...
There's always the issue of prestige and technological supremacy. When you can do somethign no one else can technologically, it's more likly other governments/researchers will defer to you on the subject. Your influence increases and your ability to make certain claims increases. It's like civilization, achievement = prestige = influence.
"There are more things in heaven and earth, Horatio, than are dreamt of in your philosophy."
I believe that was to test the theory that changes in velocity affect time, whereas the current experiment is to test the theory that a rotating object affects time and space.
Who said we're going to share the information? The secrets of relativity are ours, and the rest of the world can just go on thinking that e=mc^2! Suckaz!
They put all the gyroscopes in a dewar with 1500 liters of liquid helium to keep it cold. Plus they get to use the helium that evaporates for the stabiliztion thrusters.
what sig?
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.
I really don't think the financial analysis is the correct one. I'm fairly sure the US will derive enough benefit to justify the cost, although the benefit is admitedly difficult to quantify and is amortized over the rest of our specie's existence. Does it matter if the rest of the world gets a free ride? They do pure science too, and we benefit. Science is a collaborative effort. This isn't some billion dollar defense department project seeking a military advantage over a perceived adversary. This is about scientific discovery and learning things that have never been known. In my cynicism concerning politics, I sometimes forget to be optimistic about the science.
>> My ultraviolent Linux switch video.
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.
Marx didn't propose death squads or any other form of tyranny. That's like blaming George Bush on George Washington.
The darkness... controls the music. The music... controls the soul.
So, if it's impossible to implement what Marx proposed with homo sapiens how exactly did it kill about 100M people?
//Blessed are they that run around in circles, for they shall be known as wheels.
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!!!
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
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
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.
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?
Marx advocated revolutionary overthrow of the existing social order, and abolition of private property and religion. The goal was mandatory egalitarianism, where nobody can ever improve their economic status. Do you really think this can be accomplished without violence and dictatorship? Communism is not some wishy-washy philosophy that says we should all work for the common good and not be greedy; it demands that this system be imposed from above.
You seem to misunderstand...time DOES slow down the faster that you're traveling. Einstein's famous twins paradox, for example. Imagine twins born at the same time, one is put on the on a spacecraft travelling through space at near-light speed (since C is unachieveable), and the other child grows up on earth normally. When the earth-twin is 30 years old, his space-twin returns, and is only 3 days old.
-J
Beer, now there's a temporary solution -- Homer Jay S.
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"
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
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.
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.