Natural Science Forum / Physics / Research / November 2007

In his paper - "The Confrontation between General Relativity and
Experiment: A 1998 Update" - http://xxx.lanl.gov/abs/gr-qc/9811036
Clifford M. Will wrote on page 12 that
      the Global Positioning System (GPS) provides absolute

 "Atomic clocks" were subjected to many
experiments in order to establish their
behaviour. They were transported at various
velocities and accelerations. They were placed

first there was that weird Swiss ballot encryption thing:
http://www.smh.com.au/news/World/Swiss-to-use-encryption-voting-method/2007/10/1
3/1191696216022.html
now there is this weirder astronomers are hastening the end of the
universe thing:

Back in April, I posted on this topic asking for help understanding an
apparent paradox with the way that potential energy works in the
linear approximation to GR; it appears that when multiple masses are
brought together in a system the rest energies of the masses are

The new, twenty-first edition of the freely
downloadable physics textbook is available on
    http://www.motionmountain.eu
Almost 1500 pages lead through the whole of physics, from

I am heating a surface with a 10.6nm laser and i want to measure the
temperature of this surface.
Is there a sensor that can give me a real time measurement?
If you can help me, please give me link or help me to understand what

Can someone please explain the principle of general covariance in
simple terms.
Thanks

"An Exceptionally Simple Theory of Everything" by A. Garrett Lisi.
http://arxiv.org/abs/0711.0770
He uses the Lie Algebra E8.

Is there a single, well-accepted form of the dirac equation for a free
particle in curved spacetime? If not, what are the various
possibilities constructed so far?

I was wondering whether the Higgs mechanism, by which a particle gains
mass by interacting with higgs bosons, causes decoherence of the
particle's wavefunction?
John

Here is a riddle that requires the creative application of group
theory to solve...
Riddle: An observer is sitting in a Universe at the point in spacetime
t=x=y=z=0, also refered to as here and now.  The observer sees an

http://cosmiclog.msnbc.msn.com/archive/2007/07/17/274531.aspx
I know most physicists reject the idea of FTL communication but I'm
surprised the experiment described in this article wasn't carried out
years ago or has it? Wouldn't the existence or absence of an

The concept of a point charge is well known to have some problems.
Suppose we consider a point charge to be really a spherically
symmetric charge distribution of radius r equal to epsilon with
epsilon having the property that epsilon squared is greater than zero

If MOND turns out to be correct, and obviates the need for Dark Matter,
is that likely to have an impact on the need for Dark Energy to explain
the presumed accelerating expansion of the universe?

What happens if an electromagnetic field, tuned to a specific objects
frequency, is passed through that object.  If I had a lab (and a
degree in physics), the first thing I would do is this:  Set up a high
poewred magnetic field and measure the frequency of the realative