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: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: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 ??

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: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?