Natural Science Forum / Physics / General Physics / May 2007

Anybody knows centre of gravity of human brain? As the mass of
neocortex is 76% of total mass of human brain, center of gravity of
human brain should be somewhere in neocortex.
I searched web, groups but can't find answer.

Can you write symbols or draw diagrams and plane figures on a "flat"
surface to derive what is shown at:
http://www.rwgrayprojects.com/synergetics/plates/figs/plate03z.html
or do you have to work with objects made of something like cheese that

I'll cite 2 papers here, one of which argues quite effectively that
Bohr's original model of the helium atom with orbits was abandoned
prematurely, and the second of which argues that elementary particles

"The Limitations of Mathematics in Physics"
    The present philosophy in theoretical physics is to search for
mathematical relationships that predict experimental results that are then
used to verify the validity of the mathematics in defining our physical

PHYSICS NEWS UPDATE
The American Institute of Physics Bulletin of Physics News
Number 826 May 30, 2007 by Phillip F. Schewe, Ben Stein
www.aip.org/pnu

What properties would a magnet have if it had negative permeability? I
have read that certain materials have this property at microwave
frequencies - but what effect does it have on magnetism?

Herbert Goldstein's _Classical Mechanics_ has long been considered "the"
standard in advanced mechanics textbooks.  How does Goldstein compare to
say Syman's Mechanics?  What other books fall into the same category?
I have Syman.  I have no complaints about what I've read thus far. ...

PHYSICAL REVIEW FOCUS   30 May 2007   http://focus.aps.org/
David Ehrenstein, American Physical Society
Introductions to the Focus stories of the past week;
visit http://focus.aps.org for the complete stories.

This question appears in the problem supplement to the Feynman
Lectures: "Can you explain why there are no crystals which have the shape
of a regular pentagon? (Triangles, squares, and hexagons are common in
crystal forms.)"

I've read in a few articles about the "mystery" or the "origin" of
inertia, however I don't really understand what this mystery is about.
If I understood correctly, the principle of inertia can be easily
derived (in classical mechanics, at least) from the symmetry of space.

Novice here..
Is it possible to entangle two objects in such a way that when untangled the
mass of one is different to the other? In other words the mass is
equal/undefined until untangled?

One of the problems from the Feynman Lectures asks us to show that three
forces in static equilibrium must all be coplanar, and their lines of
action must pass through a single point.  
If someone were to ask me what is meant by "line of action of a force", I

I started this book years ago, but was forced to focus on other issues at
that time in my life.  I pulled it off the shelf today, and realized that
it really is a good book.  Anybody read it?
A Unified Grand Tour of Theoretical Physics, by Ian Lawrie.

I am trying to set up the experiment with the high energy gamma source
which would be able to produce positrons in the material by use of the
pair creation. I need to have a relatively high gamma energy for it.
Are there any natural high energy gamma sources which have a half-life

Here is a quote from a modern English text of The Heavens by
Aristotle:
pg443 of McKeon's edition
"For there will be a force which moves it, and the small and lighter