Newton's Second Law, Revisited

eldavojohn writes "Dust off your fundamental physics books, an aspiring astrophysicist by the name of Alex Ignatiev has published a paper that proposes testing special cases of Newton's Second Law on earth's surface. His goal is sort of ambitious. The time he has to test his theory is only 1/1000th of a second, twice each year, in either Greenland or Antarctica. What would he look for? Spontaneous motion. From his interview with PhysOrg: 'If these experiments were to take place, Ignatiev says that scientists would look for what he calls the SHLEM effect. This acronym stands for static high latitude equinox modified inertia and would be noticed in a condition where the forces of the earth's rotation on its axis, and of the orbital force of the earth as it moves around the sun, would be canceled out ... In the end, if Newton's Second Law could be violated, he would be forcing physicists to reevaluate much of what we understand derived from that law — which is quite a bit.'"

Re:the era precision cosmology

[amRadioHed]

The evidence has accumulated that we live in a universe that's much stranger than we'd believed. I think that's cool.

And what about that rules out MOND?

A big IF

[Ibag]

"In the end, if Newton's Second Law could be violated, he would be forcing physicists to reevaluate much of what we understand derived from that law -- which is quite a bit.'"

In the end, if the second law of thermodynamics [or any other law of physics] could be violated, it would force physicists to reevaluate much of what we understand derived from that law - which is quite a bit. However, given that what we have derived from our laws generally fits with experimental observation (which is why we call them laws), the odds of him disproving Newton's second law with this experiment are about as good as me disproving the second law of thermodynamics by accidentally building a perpetual motion device.

Experiments disproving longstanding laws have happened before. People don't have reason to care about them until afterwards, though.

troll toolbox

[Anonymous Coward]

Template #183
Category: Instant karma
For: new scientific theory proposed

Yes, it only takes one demonstration to a render invalid a scientific theory. But that does not validate any other theories by doing so, unless they can accurately carry the same predictive weight as the previous theory, plus comply with the improved observations.

A hole in $SCIENTIFIC_THEORY in any case doesn't mean scientists throw out their $SCIENTIFIC_FIELD books, it generally means they add and exception to the theory and work on finding a more unified algorithm to describe the newly revised observations. Here's hoping this somewhat exotic set of observations leads eventually to a stronger set of theories, rather than just more false controversy about 'mavericks' and 'closed minded skeptics' - everyone's a skeptic AND a maverick, closed minded and radical - focusing only on the extremes of that, especially in terms of science sort of ignores the whole point of science, to use biased viewpoints to paint a larger picture.

Dangerous?

[Plutonite]

Newton's law underwent some serious revisiting in 1905 when a chap called Einstein realised that masses are not constant/absolute but in fact relative, and this is why the modern relativistic notation differs quite a bit from the original F=ma. Now if this new guy is not joking (Russian timezones, April 1st, bit early..etc) then not only is our understanding of momentum going to be radically different, but in fact E=mc2 might have to be revisited as well (must read part 10 of this historical paper by Einstein [fourmilab.ch] to understand). That happens to be a very ground breaking idea if it were true, and would change lots of things we supposedly know about fundamental physics.

Re:A big IF

[blank axolotl]

The key is that our experimental observations only cover the cases we have thought to test - he would be testing the law in a new way.

In fact, we already know that newton's second law is wrong from special and general relativity, but you only see so at high velocities/high curvature of space. It was only once we had the theory that we knew how to test it properly. Here he is testing the law in the case of very small accelerations, based on a theory which tries to explain an astrophysics observation that is not well understood. Who knows, he might find something.

In addition, we already know that our theory from general relativity is incomplete because it does not match up to quantum mechanics, so there is surely still something to be discovered there somewhere.

Not peer reviewed yet...

[gb]

It's worth pointing out that this paper is only publihed on a preprint server - that means it has not been through peer review, so needs to be treated with a lot of caution. There's an awful lot of totally crazy stuff on preprint servers. Not that I'm saying it's totally crazy - whilst I'm a physicist, I do condensed matter not astro - amd wouldn't describe myself as qualified to have a definitve opinion. But I would be both cautious and skeptical until proven oherwise.

Re:A big IF

[Ibag]

A few quick comments. First, relativity does not conflict with Newton's second law. It only needs to be changed from F=mA to F=dp/dt where p is momentum. Second, nobody said that general relativity was the pinnacle of physical theories. People have been trying for a while to find a grand unified theory that incorporated all the known forces in the universe and worked at both small and large scales. This appears to have nothing to do with the article, though. Third, while our experimental observations may only cover the cases we have thought to test, our laws are further verified every time the world behaves like we expect it to, every time we use GPS satellites with relativistic corrections, and every time we use devices that rely on quantum effects to work. The odds that everything holds except for 2/1000 of a second each year in two places on earth is unlikely. Maybe the experiment will work. That is science. However, it doesn't hurt to be skeptical until the experiment is done. I'm not saying that it won't happen, just that it seems premature to talk about rewriting textbooks just yet.

I disagree

[khallow]

We know the spectrum and angular distribution of the cosmic microwave background to high precision.

This is the only statement that is correct since it is the only conclusion derived directly from observation. A lot depends on how accurate our models of the universe and physics are. I think MOND is unlikely to last, but the theory is yet viable. Your claims about the age of the universe, mass of neutrino, etc are likely to be correct, but it would be embarrassing if these observations turn out to be dependent on assumptions that are incorrect. Eg, perhaps Type IA supernovas are different in the early universe than they are now (even though physical law is the same, there are substantial differences like elemental composition), perhaps we're incorrect about our local gravity environment (eg, we're deeper in a gravity well) and this effects our perception of the temperature of the cosmic background, or perhaps a more accurate model of the universe involves oscillating yet massless neutrinos.

Both Sun and galaxies centers are accelerating

[Alex Belits]

This article (and the whole MOND thing) would make some sense if the systems described in them were not accelerating because of gravity. Sun is subjected to the gravity forces toward the center of our galaxy, so its path relative to the center of the galaxy is not a straight line but a circle -- though a very large one. I find it to be an extremely weird oversight considering that the whole hypothesis exists to describe parameters of the very same motion of stars in galaxies. So even when a point on the Earth surface is not accelerating in the Sun's coordinate system, it still does in the galaxy's coordinate system.

Worse yet, MOND does not explain anything about galaxies because galaxies themselves accelerate. They are not distributed evenly and uniformly in space but form clusters. Each cluster just like a galaxy itself, is pulled together by gravity, so galaxies experience some acceleration in the cluster's coordinate system because of the gravity of other galaxies.

Obviously this acceleration is not detectable locally because it is caused by gravity -- for the same reason objects in orbit are "weightless". To find out that you are in freefall (or in orbit, what is the same thing) without looking at other celestial objects you have to throw something and observe its movement -- since gravity is not parallel and uniform everywhere, after the object will get far enough from you, it will be noticeable that its trajectory is not a straight line relative to you, as it would be if you weren't accelerating at all. However locally gravity and acceleration are indistinguishable, and at the scale of Solar system or galaxy the size of such "local" area is huge.

MOND is talking about absolute acceleration that should be clearly distinguishable from gravity. However if we will try to find something in the universe that is really "unaccelerated" by this definition, there will be very few objects in this category, if any. Certainly it would not be massive centers of galaxies, Sun or two spots on the Earth surface the author of the article proposes as locations for his experiments.

This is the theoretical part of the problem. Now, the practical one. In two proposed spots the conditions that article author expects to happen last for a very short time and happen once a year. The extent of effect is similar to the influence of gravity from many existing celestial bodies. Tidal waves caused by Moon and affected by the shape of oceans, condition in the atmosphere, movement of Earth crust, etc. are likely to produce more noticeable influence on any test body that may be used in the experiment. Though I didn't do any calculations, it's hard to believe that variations of tidal waves caused by changes in weather will be less than supposed effect of "modified" 2nd Newton's Law even if it worked the way that the article author's proposed. And since conditions are supposed to be so rare, there is no way to collect enough samples for any statistical analysis.

In the end, I can add that if your experiment is to look for a black cat in a dark room, it shouldn't be a surprise if the result is negative regardless of the actual presence of a cat. However this makes no excuse for proposing that the cat is in the room when there is no reason for it to be there in the first place. Both theory and proposed experiment look extremely stupid, and if MOND can be modified to explain why it should include movement of stars within galaxies but not movement of galaxies in clusters, maybe it would be worth a second look. For now it's just that -- stupid idea with no foundation and no viable method of verification.

Re:Finding holes in the theory...

[Anonymous Coward]

Actually, even 1 failed experiment probably won't invalidate a theory - I'm fairly certain you'd have to demonstrate that the failure is repeatable given certain conditions. Otherwise there's no guarantee that you're equipment wasn't measuring properly or whatnot.

Re:Hammer, Feather, Freefall on the Moon: Revisite

[JohnFluxx]

That assumes that the difference in position and momentum is greater than the uncertainty principle allows, which isn't immediately obvious. If you do the calculations, you may just find that the difference is smaller than QM allows, and thus there is no difference.