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.'"

Comments

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 also discusses some empirical tests that MOND (and TeVeS) seems to have failed.