Hey, Mom!!! Guess what!! We don't have to abandon Newton's Laws!! Isn't that great!! Here, read this!!!

"NEWTON*S SECOND LAW OF MOTION, that pillar of classical physics, the
formula that says the force on an object is proportional to
acceleration, has now been tested, and found to be valid, at the
level of 5 x 10^-14 m/s^2.

This is a thousandfold improvement in
precision over the best previous test, one carried out 21 years ago
(Physical Review D, vol 34, p 3240, 1986). The new test was
performed by physicists at the University of Washington using a
swiveling torsion pendulum, a special kind of pendulum in which the
restoring force is not gravity (as you would have in a hanging
pendulum) but is provided by a very thin torsion fiber.

One
implication of Newton*s law is that the pendulum*s frequency (its
tick-tock rate) should be independent of
the amplitude of its swiveling (as long as the oscillation is
small). Looking for a slight departure from this expected
independence the Washington researchers watched the pendulum at
very small amplitudes; in fact the observed swivel was kept so small
that the Brownian excitation of the pendulum was a considerable
factor in interpreting the results. Newton*s second law is expected
to break down for subatomic size scales, where quantum uncertainty
frustrates any precise definition of velocity.

But for this experiment, where the pendulum
has a mass of 70 g and consists of 10^24 atoms, quantum
considerations were not important.

According to one of the
scientists involved, Jens Gundlach (206-616-3012,
jens@phys.washington.edu), this new affirmation
that force is proportional to acceleration (at least for
non-relativistic speeds), might influence further discussion of two
anomalies:

(1) oddities in the rotation curves for
galaxies---characterizing the velocity of stars as a function of
their radii from the galactic center---suggest either that extra
gravitational pull in the form of the presence of as-yet-undetected
dark matter is at work or that some new form of Newton*s Second Law could be
operating (referred to as Modified Newtonian Dynamics, or MOND); and

(2) the ongoing mystery surrounding the unaccounted-for
accelerations apparently characterizing the trajectory of the
Pioneer spacecraft"

Yayyyy!


A