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:violate what law?

[demeteloaf]

Currently, there is a discrepancy between the rotations of galaxies, and what newtons law says should happen. If you look at large galaxies, at a bunch of different radii, all the stars orbits are at about a constant orbital velocity, which since there is less force acting on them from gravity, shouldn't happen.

The most common physical explanation of why this happens is that there is a ring of dark matter around the galaxies that is also producing a gravitational force, and that when you add in the force from the dark matter, the equations work out, and you calculate that the orbital velocities should be constant.

However, there are some physicists who don't like the idea of dark matter, and in order to explain how galaxies orbit, introduced a new version of newton's second law. F = m * f(a/a0)*a, where a0 is a new fundamental constant describing a small acceleration level where these new Newtonian dynamics hold. and f(x) is a function that equals x when x > 1. This theory describes the constant angular orbit speed of galaxies without the need for the existence of dark matter, however, the theory has problems when applied to relativistic systems.

What it looks like this new paper proposes to do is find a place on earth where the acceleration from the coriolis effect, the centripital acceleration and the acceleration from the sun will all cancel out, and then create a really small force and see if the modified second law works for a very small absolute acceleration.

Re:the era precision cosmology

[bcrowell]

And what about that rules out MOND?
It doesn't rule out MOND, but it shows that what MOND was trying to avoid -- dark matter -- is an intrinsic part of an extremely successful cosmological model, which has passed a variety of high-precision tests. The Wikipedia article on MOND [wikipedia.org] also discusses some empirical tests that MOND (and TeVeS) seems to have failed.

This is actually a well known phenomenon

[Anonymous Coward]

http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/fw/cr ls.rxml [uiuc.edu]

The link above explains the Coriolis force. Among other things, this is the force that causes water to spiral down the drain in different directions on different sides of the equator. It also manifests itself such that if you fly at sufficient speed travelling past 63 deg. North Latitude, you will feel a slight bump. This is easily measured and confirmed by placing an accelerometer on the aircraft. There is almost always a slight acceleration. Of course, the accelerometer is subject to the vibration of the aircraft and to rapid changes in altitude due to air currents so the bump is often lost in the noise floor but it's there nevertheless.

The phenomenon cited above is not limited to any particular time and is somewhat south of 80 deg. North Latitude but I suspect that Ignatiev is probably talking about the same thing. He should check his math.

Re: Relativistic 2nd Law

[Svartormr]

...Newton's second law is wrong from special and general relativity...

Not if you state it in the form:

F = dp / dt

where F is the force on an object, p is the momentum of the object, and t is time; ie. the force is the time differential of the momentum. (And for completeness, p and F can be vectors.) Only with classical simplification do you get "F = ma".

Re:Not peer reviewed yet...

[Dr_Mic]

Indeed, it is quite a stretch to say that putting a paper up on arXiv.org is "published" in any normal sense (say onethat would be accepted by a tenure review committee). However we do have

Is Violation of Newton's Second Law Possible? A. Yu. Ignatiev Phys. Rev. Lett. 98, 101101 (2007)

as well as

Mirror dark matter and large scale structure A. Yu. Ignatiev and R. R. Volkas Phys. Rev. D 68, 023518 (2003)

Geophysical constraints on mirror matter within the Earth A. Yu. Ignatiev and R. R. Volkas Phys. Rev. D 62, 023508 (2000)

and others.

The author has a real publication record. For phys rev and especially phys rev lett, the crank filters are a little more effective. As with the parent, this is not my field. However, my initial knee jerk reaction (crank!) has abated somewhat.

Re:I disagree

[Ambitwistor]

This is the only statement that is correct since it is the only conclusion derived directly from observation.

No, you could introduce weird mechanisms that distort the true spectrum of the CMBR, which is about as plausible as the other scenarios you put forth.

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)

You would then have to explain how these different supernovas still manage to produce the same characteristic light curves as modern supernovas. Possible in principle, but not plausible.

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

The temperature of the cosmic background isn't really that important in this context, and moreover, I can't imagine what kind of "gravity well" you could think that we were in that would distort all our measurements of distant galaxies equally and in all directions, without simultaneously distorting local observations.

or perhaps a more accurate model of the universe involves oscillating yet massless neutrinos

Only if you want to basically throw out all of relativity and quantum mechanics, since you can't get flavor oscillations without mass in any theory that obeys both; flavor and mass are complementary observables.