...such as how Netwon's laws are incorrect near the speed of light.
Small but important nitpick: Newton's laws are actually incorrect at all speeds. The differences between the newtonian model and the relativistic model, however, are negligible for all but the most precise experiments for low speeds.
Thus, the lack of perfection of Newton's laws serves as an example of your first point as much as your second.
(The main point of your post, though, is very good!)
Dangnabbit, where are my mod points when I need them?
This comment is both (1) technically wrong and (2) misguided.
It certainly shouldn't be modded ``Insightful''!
(1) The notation ``bEa'' is shorthand for ``b times 10^a''.
Therefore, ``10E-24'' means ``10 times 10^(-24)'' = 10^(-23),
which isn't 10^(-24).
(2) Prefixes may or may not have much in common with emoticons,
but they are worth creating.
They are very handy for communication, both oral and written.
Other posters have made this point, so I won't say any more about it.
(By the way, should ``dangnabbit'' have one ``b'' or two?
I can't find any trustworthy resources on this.)
The point is that you don't get stuck in a saddle. Motion along one direction is inhibited, but motion along an orthogonal direction is encouraged. To get stuck, you need to be inhibited in all directions.
Velocity is relative, but acceleration isn't relative. Rotation involves acceleration. So it isn't equivalent to say that X rotates around Y is the same as Y rotates around X. (Hypothetical example: consider a universe empty except for a single planet which is rotating. What does it mean to say it's rotating, without reference to background stars? Is it equivalent to a model where we say the planet doesn't rotate? No - we could see the difference in a centrifugal force causing the planet to bulge as it rotates.)
Anyone who enjoys this sort of thing should really, really read about http://en.wikipedia.org/wiki/Mach's_principle. Ernst Mach thought about acceleration in the absence of the rest of the universe quite a bit. His ideas had a strong influence on Einstein when he was developing general relativity. (However, whether or not GR actually agrees with Mach's Principle is complicated).
... and those that think I might be posting from the Southern US.
Why is this particular form of prejudice allowed and even encouraged on Slashdot (by being moderated "Funny")?!?
If Tanktalus had written "... and those that think I might have darker skin than average"
or "... and those that think I might be a woman", then he/she would be rightfully modded down to -1
and there would be multiple posts by now justifiably calling him/her a bigoted asshole.
This does not mean gravity in fact moves faster than light, it just means the measurements are inaccurate.
Your post is both interesting and informative, so it's worth my being a little bit pedantic. You should have said that ``the measurements are imprecise'' -- they seem to be completely correct, but they have a larger uncertainty than we would like.
True, CNN isn't a very good scientific source on its own. However, if you follow the links, you'll find that the CNN story is based on a NASA press release (decent science), which in turn is based on a paper in Physical Review Letters. It doesn't get much better than PRL.
If a story appears ONLY on CNN, then you should be wary. However, most significant scientific stories are mentioned on CNN sooner or later, so you shouldn't use CNN as your sole criterion for the value of a story.
You're correct that the GPS system provides a great test of relativity. However, the theories of relativity make many predictions, and GPS doesn't test all of them. Clock-comparison experiments study another aspect of relativity: Lorentz symmetry.
I thought this was precisely what special relativity does predict, that a moving observer experiences less passage of time than a stationary one, increasingly so as the speed becomes a significant fraction of the speed of light. If the ticking rate does not vary, then special relativity would be invalidated.
You're correct about special relativity, but we're considering a different sort of effect.
Special relativity predicts
(among other things, as you describe above)
that the ticking rate of a clock, when always viewed from its own rest frame, is independent of the clock's orientation and velocity with respect to everything else in the universe. We're studying this idea by watching very sensitive clocks as they rotate or change velocities. Any dependence of a clock's rate on its orientation would imply that some directions are different from others, i.e, it would show a violation of rotational symmetry, which is a subgroup of Lorentz symmetry.
The CNN article is not very clear as to what it says.
Agreed. This is why you should follow the included links to more information. First, read the JPL press release. If you want information beyond that, I strongly suggest viewing the
FAQ and
animations
on Alan's web page.
Disclaimer: I partially wrote the FAQ and created most of the animations, so I may be biased as to their quality. Constructive criticism is welcome.
As coauthor of the Lorentz-violation paper being discussed, I'd like to reply to a few comments that have been made. This comment seems like a good starting point.
_Special_ relativity and quantum mechanics have no trouble getting along. In fact, the so-called Standard Model of particle physics, based on relativistic quantum physics, is an enormously successful theory. The trouble lies in getting relativistic gravity (i.e., _general_ relativity) to play nice with quantum mechanics. This is where string theory comes in.
The good thing about string theory is that it allows gravity and quantum mechanics to get along. The bad thing about string theory is that there is absolutely _no_ experimental evidence for it, and there are almost no possible tests of it that could be conducted in the near future. Lorentz violation is a major exception: The afore-mentioned Standard Model obeys a certain symmetry called ``Lorentz symmetry'', which lies at the heart of special relativity. However, string theory allows Lorentz symmetry to be broken. Thus, any experimental detection of Lorentz violation could be a great signature of string theory, and, maybe, quantum gravity. Moreover, there exist current experiments that are capable of detecting Lorentz violation to a very high precision.
To summarize: We are studying Lorentz violation because (1) It is a possible signature of quantum gravity, and (2) It can presently be studied to very high precision.
Slashdot Mirror
Small but important nitpick: Newton's laws are actually incorrect at all speeds. The differences between the newtonian model and the relativistic model, however, are negligible for all but the most precise experiments for low speeds.
Thus, the lack of perfection of Newton's laws serves as an example of your first point as much as your second.
(The main point of your post, though, is very good!)
(1) The notation ``bEa'' is shorthand for ``b times 10^a''. Therefore, ``10E-24'' means ``10 times 10^(-24)'' = 10^(-23), which isn't 10^(-24).
(2) Prefixes may or may not have much in common with emoticons, but they are worth creating. They are very handy for communication, both oral and written. Other posters have made this point, so I won't say any more about it.
(By the way, should ``dangnabbit'' have one ``b'' or two? I can't find any trustworthy resources on this.)
Chuck
Anyone who enjoys this sort of thing should really, really read about http://en.wikipedia.org/wiki/Mach's_principle. Ernst Mach thought about acceleration in the absence of the rest of the universe quite a bit. His ideas had a strong influence on Einstein when he was developing general relativity. (However, whether or not GR actually agrees with Mach's Principle is complicated).
Chuck
Why is this particular form of prejudice allowed and even encouraged on Slashdot (by being moderated "Funny")?!?
If Tanktalus had written "... and those that think I might have darker skin than average" or "... and those that think I might be a woman", then he/she would be rightfully modded down to -1 and there would be multiple posts by now justifiably calling him/her a bigoted asshole.
Bigotry is bad, ok?
This does not mean gravity in fact moves faster than light, it just means the measurements are inaccurate.
Your post is both interesting and informative, so it's worth my being a little bit pedantic. You should have said that ``the measurements are imprecise'' -- they seem to be completely correct, but they have a larger uncertainty than we would like.
Chuck
If a story appears ONLY on CNN, then you should be wary. However, most significant scientific stories are mentioned on CNN sooner or later, so you shouldn't use CNN as your sole criterion for the value of a story.
Chuck
Chuck
You're correct about special relativity, but we're considering a different sort of effect.
Special relativity predicts (among other things, as you describe above) that the ticking rate of a clock, when always viewed from its own rest frame, is independent of the clock's orientation and velocity with respect to everything else in the universe. We're studying this idea by watching very sensitive clocks as they rotate or change velocities. Any dependence of a clock's rate on its orientation would imply that some directions are different from others, i.e, it would show a violation of rotational symmetry, which is a subgroup of Lorentz symmetry.
Chuck
Agreed. This is why you should follow the included links to more information. First, read the JPL press release. If you want information beyond that, I strongly suggest viewing the FAQ and animations on Alan's web page.
Disclaimer: I partially wrote the FAQ and created most of the animations, so I may be biased as to their quality. Constructive criticism is welcome.
Chuck
As coauthor of the Lorentz-violation paper being discussed, I'd like to reply to a few comments that have been made. This comment seems like a good starting point.
_Special_ relativity and quantum mechanics have no trouble getting along. In fact, the so-called Standard Model of particle physics, based on relativistic quantum physics, is an enormously successful theory. The trouble lies in getting relativistic gravity (i.e., _general_ relativity) to play nice with quantum mechanics. This is where string theory comes in.
The good thing about string theory is that it allows gravity and quantum mechanics to get along. The bad thing about string theory is that there is absolutely _no_ experimental evidence for it, and there are almost no possible tests of it that could be conducted in the near future. Lorentz violation is a major exception:
The afore-mentioned Standard Model obeys a certain symmetry called ``Lorentz symmetry'', which lies at the heart of special relativity. However, string theory allows Lorentz symmetry to be broken. Thus, any experimental detection of Lorentz violation could be a great signature of string theory, and, maybe, quantum gravity. Moreover, there exist current experiments that are capable of detecting Lorentz violation to a very high precision.
To summarize: We are studying Lorentz violation because (1) It is a possible signature of quantum gravity, and (2) It can presently be studied to very high precision.
Chuck