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.

Comments

And if his theory is proved wrong...

[Anonymous Coward]

could this post be considered a relatively first post?

Cheap shot

[platypibri]

We fail to understand the gravity of this situation.

That's a lot of money to spend

[mindless4210]

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.

Re:That's a lot of money to spend

[I_Love_Pocky!]

Wouldn't our understanding of something as fundamental as general relativity far out weigh any kind of understanding we could gain from Mars? Even if life is found on Mars, it does little to solidify our understanding of the fundamental forces of the universe.

Gravity is one of the most important, and least understood forces in the physical world. Mars is just a big rock in orbit around our tiny little sun. Going there is a cooler project that this, but the information garnered from such a mission seems to be less important than what this mission is set to show.

Re:That's a lot of money to spend

[Rosco P. Coltrane]

although it seems like a lot of money to spend just for testing his theory

I think it's really a cheap experiment, considering the importance of the results. If there's something wrong or incomplete in Einstein's theory, we (as in humanity) should know about it, firstly because it's the human nature to try to know more all the time, and secondly because it could be very important in practical terms: you wouldn't want to take a plunge off a cliff with your SUV because your GPS receiver had a slight error, would you?

This is theorical science and experimentation at its best. The price is really cheap to advance mankind's knowledge. Compare this to the weekly cost of certain recent military activities that probably won't bring back much to mankind anytime soon...

Re:That's a lot of money to spend

[Stuntmonkey]

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.

That boils down to less than $3 per American, spread out over the last 40 years.

To prove conclusively (or not) our most fundamental theory of gravity, space, and time.

Man, you are a cheapskate.

Re:That's a lot of money to spend

[Anonymous Coward]

Wouldn't our understanding of something as fundamental as general relativity far out weigh any kind of understanding we could gain from Mars? Not necessarily. More has been learned from putting this experiment together than will be learned from its results - it is a fine-scale test of one of the most successful theories of all time. Going to Mars, though expensive and such, could be a big deal if only as a proof of concept. Look at how much was learned going to the Moon. Going to Mars is orders of magnitude more complex - interplanetary radiation, the technological and social advances that will let a crew live together for months, getting people there and back ... if we can get to Mars and back we can go anywhere in our Solar System with trivial amounts of scaling. And, if we do find life on Mars (or elsewhere), that is potentially the most important discovery, um, ever. It tells us things about the fundamental nature of the universe too - and, short of an experiment either detecting gravity waves or detecting an overall curvature to spacetime, there isn't that much experiments will tell us about gravity right at the moment.

Probe componentry

[Rosco P. Coltrane]

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 Great Man

[osewa77]

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!

Perfect Quartz Spheres

[RobertB-DC]

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!

Scientists crossing fingers, pacing

[Neil Blender]

"E had just better equal MC squared...E had just better equal MC squared..."

Why has it been in the making for so long?

[Pi_0's don't shower]

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.

Re:Why has it been in the making for so long?

[Stuntmonkey]

The correction to the precession will be on the order of arcseconds (1/3600 of a degree) per year.

It's significantly smaller than that -- the precession due to frame dragging is predicted to be only 0.04 arcseconds over one year.

And I agree that the physics community is 99% confident that the Lense-Thirring effect is real. However, I also think this is more because of the aesthetic beauty of the theory, rather than actual measurements. If it were a less fundamental theory being tested I would call it a waste of money, but for something as fundamental as GR I think a confirming direct experiement is justified.

The real question is how many viable alternatives to GR are ruled out by this test, assuming it is successful. For example nearly all viable GR alternatives proposed have weak gravitational wave properties identical to GR, so detecting these waves provides little support for GR. I wonder if the Lense-Thirring frame-dragging effect is more discriminating.

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.

Einstein...

[PeaceTank]

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...

Slow

[Mateito]

> will spend two months getting ready

Sounds like my girlfriend.

An experiment in inertia?

[David Hume]

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.

Better understanding of gravity

[Outosync]

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 :)

Not always hard

[Pi_0's don't shower]

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.

Re:Absolute Zero?

[nrlightfoot]

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.

It was actually launched last week

[DJStealth]

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.

Re:The question is who funded it?

[Long-EZ]

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.

Wow!

[jonfromspace]

The satellite, which was inserted into a polar orbit, will spend two months getting ready, then 16 months making measurements.

Sounds like my Girlfrind when we go shopping...