Natural Science Forum / Physics / Research / October 2006

Something I have never understood is how it is possible to measure the
temperature of radiation, specifically the CMB. In my niave way of
thinking, temperature is a "property" of a material body that must be
measured with, say, a thermometer. Could someone please explain how

Consider two identical Kerr black holes, both spinning at near the
maximum rate and with spins anti-parallel. Also assume both lie in the
plane of their spin axes. I wonder if there will be a force of repulsion
between the two, caused by the effects of mutual frame dragging? This ...

Is there a known correlation between the result of the refraction of light
in transparent materials, say, compared with gravity's effect on light in
a vacuum, in particular 'lensing'?
My second question: Why cannot the phenomena of  ''light' be 'scaled' down,

When we are using the classical Maxwell equations in condensed matter
we usually introduce the average vector fields E_m and B_m (m for
macroscopic) as well as rho_m and j_m for charge and currents.
Where the macroscopic quantity is, in a formal way, given by A_m(r,t)=

My question is, quite simply stated, why quantization?  Why does E =hv?
Why are the energy states of a particle in a quantum-well quantized?
Etc. etc. etc...
Mass curves spacetime thereby "creating" gravity.  What is the

I would like to ask for your guidance on a problem that I have always
had difficulty with whenever I tried to understand it. It's the
argument for the gravitational redshift derived from energy
conservation presented in textbooks such as by MTW and Schutz.

Given any 2 arbitrary 4-current densities and their resulting EM fields.
J1_u, is located at coordinates (x1,t1), and radiates an EM field F1^uv
J2_u, is located at coordinates (x2,t2), and radiates an EM field F2^uv
Where x2,t2 and x1,t1, are two different but nearby points in ...

I'm wondering whether it is possible in the Special Theory of
Relativity to show within the confines of a single inertial frame that
a rod which is accelerating in the direction of its length will
contract. This is different to the problem of showing that a rod will

Dear SPR friends,
   It is of course well-known that the (contravariant) spacetime metric
g^uv and Dirac gamma matrices are related by the commutation
relationship:

I wonder how to determine a thermodynamical system's correlation
length from a computer simulation. Take, for example, an Ising system
with spins \sigma subject to nearest neighbor interactions. Determination
of the correlation length requires information on the exponential decay

http://video.google.com/videoplay?docid=-8613508781303136403&q=underwater+nuclear
The famous underwater nuke test.
Why does the shock wave appear to form first partway up the plume of
ejected water?

In Nakahara's book Geometry, Topology and Physics, Section 1.3.3
discusses transition amplitude in the presence of J(t) where J(t) is
non-vanishing only on an interval [a, b] C [ti , tf]. To obtain the
transition probability amplitude between ground states, it start with

I'm a bit perplexed by the value of c being considered a constant beyond
the Milky way, and possibly within.  Could someone enlighten my thoughts
on this issue.
It has been shown that light will change course due to gravatational

This is a typical problem in undergraduate physics: When a charged
capacitor in connected to an equal uncharged capacitor through a
resistor, the final energy in the capacitors is less than the initial
energy. This loss in energy is dissipated in the resistor as heat

I teach Linear Algebra and would like to give a particle physics
application to the students. None of the elementary level texts that I
know of use this application.
In Frank Close's book "The Cosmic Onion" he describes a simple