Frame Dragging by Earth Reconfirmed

smooth wombat writes "After 11 years of watching the movements of two Earth-orbiting satellites, researchers found each is dragged by about 6 feet (2 meters) every year because the very fabric of space is twisted by our whirling world. The results, announced today, are much more precise than preliminary findings published by the same group in the late 1990s. The researchers say their result is 99 percent of the predicted drag, with an error of up to 10 percent. The details are reported in the Oct. 21 issue of the journal Nature."

Comments

GR lives on and on

[metlin]

I was under the impression that there has been experimental evidence for the existence of Spin Distortions in Lense Thirring effect?

This would mean that inward spiralling matter observed near black-hole like phenomenon were indeed valid physically.

But as the Nature article points out, the accuracy of Ciufolini's work not yet certain, since the value is not absolutely the same as that predicted by relativity (only 99%, with an error of upto 10%). And anyway, the last major prediction of GR -- gravity waves -- is not yet done.

So until then, three cheers for experimental physics!

Re:Don't Get TOO Excited

[the_mad_poster]

Frame dragging is the explanation for observed inconsistencies in the swirling gas/dust clouds surrounding massive black holes, but I don't know that this portion of the theory has ever been confirmed via experiment.

A Brief Explanation

[Pugio]

For those who aren't familiar with all of this: (I know they included it in the article but here's my own explanation.)

Basically (acc. to the theory of relativity), gravity is not really a pull from one object to the other. What it is is a distortion in the fabric of space-time. What does this mean? Well think about a sheet stretched out very flat. On this sheeta are a number of very light objects. Now think of a lead weight placed in the center of the sheet. The sheet will bend into an inverted cone shape and all the items will slide towards the weight. Ta Da! Gravity!

Gravity is an extremely pervasive force. While it is the weakest of the defined forces, it permeates every area of our universe and, overall, has the largest impact. It is even powerfull enough to warp light. Again, just think of light as travelling along the surface of the sheet, the depression in the middle will warp the ligh as it travels.

What this article is describing is a secondary gravitational effect. Now, not only does this lead weight cause things to fall towards it, but if the lead weight was spinning, it will create another path/pull of gravity. In the sheet example. think of the lead weight as shaped like a corkscrew. Now imagine what would happen if you started turning that corkscrew. Not only would the sheet be weighed down in that area but it would also become wrapped around the corkscrew, causing further twisting in the fabric of the sheet. This is the effect that is currently trying to be proved.

Black holes are essentially very very very heavy weights. They create an extremely big "depression" in the fabric of the sheet. Many black holes also spin on their axis, much as the earth does. This spinning again distorts the sheet but, given how heavy the black hole is, it causes very large distortions.

This is all predicted by the theory of relativity. For this theory to be considered valid, it must make certain predictions that can be (eventually) proven. If this experiment is, in fact, true then this is yet another proof that relativity is the real deal. And there you have it.

Actually, now that I think about it. This pattern that they describe with the black hole looks exactly like a spiral galaxy (ie. the milky way) - with large "waves" coming out on all sides. It has been theorized that there is an enormous black hole at the center of the galaxy - could this be evidence of it?

Re:A Brief Explanation

[808140]

Well, the Adam and Eve issue (as someone else pointed out) is that we don't have enough genetic diversity in one couple to produce all of humanity. Just consider the inbreeding problems that the royalty of Europe had a few hundred years ago due to intermarriage. If you wanted to populate the moon, for example, you could not just send one couple. Within a few generations, inbreeding related problems would be their downfall.

Don't get me wrong, I think it's a nice story, and it can be used (like most mythologies) to explain social issues like morality and the like, but interpreted literally it falls rather short given what we know from observation about what happens when humans reproduce with their siblings and cousins for a few generations.

Regarding Noah's Ark, this is actually a reference to a big issue in Darwin's time -- that of biological diversity. Again, Noah's Ark involves the idea of "a pair of every animal species" (which involves the same inbreeding issues as Adam and Eve) but even if you ignore that, there's the problem of the sheer number of species in the world.

See, when the judaic tribes came up with this story, their world was much smaller, and the number of species much more limited. So it seemed reasonable that an ark of a particular size could hold all the animals in the world.

But once naturalists started looking around, they realized that there were more species of animal than could possibly be held in just one ark. Furthermore, there's the issue of positioning. If you don't accept evolution, how did the animals get to their respective positions after the Flood? Did the kangaroo swim to Australia? All animals were created by god in static and unchanging way for some mystical purpose, according to religion, so after the Flood, all those animals needed to get to where the lived. Let's assume the Kangaroo did walk across Asia and then swim to Australia. Why aren't there any Kangaroos between Mt. Ararat and Australia?

How do you explain phenomena like the Wallace Line between Bali and Lombok in Indonesia?

The answer is, you don't. Noah's Ark may have been a localized occurence; there is evidence that suggests that the Mediterranean basin was once a wide and fertile valley and that a number of agricultural civilisations were destroyed as the water level rose. It's entirely possible, then, that some old guy built a boat and took his goats with him. But to extrapolate such a story to the entire world?

I could see, if you believed in evolution -- and thought major speciation could happen in just a few thousand years -- that maybe back then there were just fewer animals, and that they subsequently evolved into their current form. Of course, this isn't consistant with scientific understanding of how evolution works.

Or perhaps God created all those other Animals after the flood. Or maybe, there were many Noahs, in many different cultures, and they all built Arks. No matter how you try to explain it, though, the story as it stands is an explanation that doesn't scale.

But that doesn't mean that it isn't a great story. I enjoyed it a lot as a kid. I'll tell it to my children. But it's a story. It's like the Church saying heliocentricity was bunk. They made a mistake. So what? If your belief in God depends on a literal interpretation of the bible or other religious dogma, it's a tenous faith indeed.

Because, as I pointed out, Science can only replace the mythologies produced by religion, but it will never be able to replace the core reason for the existance of religion -- to explain why things are the way they are. There's no reason to feel threatened about modern evidence falsifying or rendering unlikely stories written by nomadic tribes millenia ago.

Re:A Brief Explanation

[Anonymous Coward]

All this is good, but I do have a slight philosophical objection to the rubber sheet explanation of gravity. It seems to me to be a kind of circular argument: It requires a gravity field to make the objects on the sheet model a gravity field. OK so there is no gravity field, there is just a distortion of space, which in the presence of a "metagravity" field means that the objects follow the curved path they would follow if there actually was a gravity field. The metagravity field then requires another distorted space to explain it, with a metametagravity field to go with it, and so now it is rubber sheets all the way down. (instead of turtles...)
OK, I think in fact that the rubber sheet business falls into the general category of "lies to Children", and that if I understood the maths it would be clearer. My take on it is that the physicists and theorists are trying to accomodate the problem of action at a distance as exemplified by gravitational, magnetic, and electric fields. We tend in our human way to treat these things as if there was a kind of invisible string pulling between the two objects, although we know this does not make sense and we are not happy about the idea of massless invisible strings anyway. (No connection with string theory which is a whole other bag of worms...I think!) So how does one object "know" that the other object is there anyway? And then there is the point that if the objects are moving, either the information about the presence of the other must travel instantaneously or it must travel at some restricted speed...Einstein tells us, and observations AFAIK confirm, that in fact the one object is responding to where the other object was in the past, with the limit on the rate of the information being c.

So I think in fact there is room for someone with a really good grasp of the whole thing to come up with a better way to explain this to the ignorant (I include myself) than the rubber sheet model.

Re:A Brief Explanation

[808140]

That's at least 5 genetically different people which should be fairly viable.

Unfortunately, it's not. How many people are needed to create a genetically viable population varies very much on the individuals concerned, but the lowest number I've ever heard is 60 -- 60 completely unrelated individuals.

Rather more than 5, at least.

Re:Don't Get TOO Excited

[Rob Carr]

It's just that it is easier to observer the phenomenon around blackholes owing to their massive nature.

The problem with the black hole observations is that a number of guestimates need to be made. The guestimates are probably valid, but there's enough wiggle room that it's hard to say the effect is really there.

The gravity maps that were used for this latest release are far more accurate than previous attempts to do this with the 11 years of data, and it seems to have confirmed that frame dragging does occur as per relativity.

The Gravity B experiment will be one more proof of frame dragging - although no one really expected frame dragging to be disproved. There's too many other things about General Relativity that have been confirmed.

Somewhere, General Relativity must break down so that it can match up with wherever Quantum Mechanics breaks down, permitting the two theories to be joined in some coherent fashion. But there's no way that frame dragging could be the place where General Relativity gives out. It's an experiment that needed to be done. It's dotting the i and crossing the t. But it's not worth much. That's the real debate. Should all the money have been spent on Gravity Probe B to prove something everyone accepts, or should other ways (like digging up 11 years of satellite data) have been used and the money spent on something that might actually give a bang for the buck?

Re:Mayube something simpler?

[Fortran IV]

You're not recognizing just how sensitive and sophisticated measurements and calculations of Earth's gravitational field have become. It's been well over a decade now since I read of how a satellite was used to create new and detailed maps of the ocean floor by measuring local variations in sea level; because rock is more dense than water, a seamount a mile below the ocean's surface creates a slight increase in the local gravitational pull, causing the ocean to hump up slightly above the mount.

The article doesn't say, but I would hope that the satellites were launched to orbit with Earth's rotation, so that frame dragging would accelerate them in their orbit, which would rule out atmospheric drag. I'd guess, though, that after 40+ years of satellite tracking such drag can probably be predicted to several significant digits, as can the gravitational effects of the Moon and Sun.

And, BTW, general relativity is a very physical theory. Last I heard, it's still the best explanation of why Mercury wobbles back and forth instead of being firmly tide-locked.

Re:Time travel

[Creepy Crawler]

Bzzt, wrong.

If the whole idea of superstrings and 10-N dimensions are correct, then there are an infinite universes. The superset of these universes would include every possible random quantum event, and every effect from each.

In order to travel from one time to "another", you actually would guide to a universe very close to your diversion rate. You could kill off everybody, and it wont effect you at all. Then again, returning back to "your" time is impossible, as you can only approach your universe as a infinite limit (yeah, fun).

Re:This project was batshit nuts

[Scott Ransom]

In order to do this experiment they had to build what are, more likely than not, the two most perfectly round objects in the entire universe...

Actually, they are only the most spherical things in our little region of the galaxy. Neutron stars (of which the closest known is a couple hundred lt-yrs away) are even more spherical.

And yes, IAAA (I am an astronomer).

Some question that can be answered ?

[Mikeybo]

Interesting, 'cause that can help us as new way to look at the space.

- If the earth's spin warps space around the planet what else is created by others planets or, what's a galaxy's effect arounds or inside itself ?

- Will this fabric help us to travel farther without a conventional energy ?

- Is the actual space station fullproof against anykind of fabric ripples ??

Re:Axioms?

[HorsePunchKid]

I thought things that were just accepted as true were called "axioms". Is "law" a synomym for "axiom" or are they different?

"Law" is definitely not a synonym for "axiom". I think the grandparent poster is rather confused. A "law" is not just something that we have observed to be true and then taken for true (i.e. taken to be an axiom). Rather, "law" is a term that has just been loosely applied, suggesting more strength than a "theory", but both pieces of scientific knowledge are not to be considered infallilble or not open to scrutiny. It is true that our scientific "laws" tend to be more fundamental in what they say, but they are still "explanations" in the same way that theories are (contrary to what the grandparent seems to be saying).

The grandparent has pieces of truth ("theories are never proven true"), but doesn't seem to have it quite right (since laws are never "proven true", either). Hope that helps clarify things. I can address the grandparent post more thoroughly if this post was too vague.

could it be something else

[austad]

Could it be something else that they haven't thought of? Like possibly due to inductive friction caused by the interaction of earth's magnetic field and non-ferrous metals in these satellites?

Re:Theory?

[Anonymous Coward]

You make an excellent point here, but not the one you think you do. Ockham's Razor, as you point out, advises us. It says that the least complicated explanation for observed behaviour is probably the correct one. It does not say that it is definately correct. It simply allows us to predict which of several explanations is most likely to be correct based on our past experience that things are usually simpler rather than more complicated.

Actually, Occam's razor states that explanations should never multiply causes without necessity. When two viable explanations are offered for a phenomenon, the simplest full explanation is preferable. The principle is most often expressed as "entia non sunt multiplicanda praeter necessitatem," or "entities should not be multiplied beyond necessity." William wrote, in Latin, "pluralitas non est ponenda sine neccesitate," which translates literally into English as "plurality should not be posited without necessity." That forms the basis of methodological reductionism, also called parsimony, which I personally don't agree with, because "entities should not be multiplied beyond necessity" is an argument against the existence of higher being, and as such is not falsifiable.

Also, talking about Occam's razor we should mention Chatton's anti-razor, saying that if three things are not enough to verify an affirmative proposition about things, a fourth must be added, and so on. That forth thing is often God for people who believe in Him. In the philosophy of religion Occam's Razor is often used to challenge arguments for the existence of God and I think that explaining it we should also mention that it is only a hypothesis, especially when many scientists today agree that the universe is (superficially) non-random, so it must have been designed by an intelligent designer. Personally I think that if people in all times and in different places have believed in God, it is unlikely that he does not exist, besides morality cannot exist without God, but I clearly state that it is a matter of my personal opinion. I believe that talking about Occam's razor you should likewise state that it is only your personal belief.

Ockham's Razor, four thousand years ago, would have had us believe that the stars were little point-sources of light floating just above the clouds.

Occam's Razor is attributed to the 14th century English logician and Franciscan friar, William of Ockham.

Gravitational non-uniformity of a black hole?

[Theovon]

So, apparently, they had to take into account the non-uniformity of the earth's gravity in order to make accurate measurements. Turning that around, the non-uniformity of the earth's gravity caused a corresponding non-uniformity in the frame-dragging of the satelites.

Consider measuring the non-uniformity of frame-dragging of a black hole. If there is any, that would imply a non-uniformity in the matter in the black hole. Through this, we can determine something about the nature or distribution of the matter inside of the black hole, even though we cannot directly observe it (without being spaghettied).

So, you CAN get information back out of a black hole after all! (Although string theory already tells us that.)

Re:Isn't that...

[MillionthMonkey]

Will these dumb myths ever die?

Hey, I said the story was apocryphal. It may be BS but it persists because it captures a grain of truth about the way Americans approach major technical problems.

Graphite is a conductor, so you don't want its dust floating around in a spaceship where it might short something out. Russian reactors (some of them) use graphite as a moderator, to slow down neutrons without absorbing them. We use heavy water. And there you go- that's another example. We go through all this trouble of separating isotopes, and the Russians just use the graphite from the pencils that they take into space! (Although there was that fire that one time, but never mind.)

Re:This project was batshit nuts

[Caraig]

Wouldn't a neutron star be spinning at tremendous angular velocities, and therefore be deformed along its equator, forming more of a flattened sphere shape? Heck, even spinning at any velocity, it sould deform along the equator. Or am I missing something about neutron stars?

Re:Isn't that...

[nacturation]

During WWII, the Manhattan Project had problems getting copper for the huge electromagnets that they needed to build. No problem- they just went to the Treasury, borrowed 15,000 tons of silver bullion, and wound it into coils!

What's really impressive is the transformation from silver into copper! :)

cool and then ... lagragian points

[Anonymous Coward]

so how those this affect the lagrangian points?
will a object at lagragian point say between earth
and the moon start spinning because of this?
can we somehow :) make energy from this?