From: Kelsey Bjarnason
To: Dan Ceppa 13-Aug-93 12:44am
Subject: finding patterns
DC>No, it only equals that in Newtownian physics. Relativity and
DC>Quantum physics uses other theory, and changes the mass, based on
DC>the basic formula, E=MC^2.
No, they use another theory and keep mass the same:
As stated above, massless particles all travel at c. As to other
attributes of particles, the presence of charge requires that there
be mass, because of the potential energy of the field (this being
energy of the system, independent of the motion - thus it contributes
to the total mass of the system as m = E/c^2). Early in this century
some thought that _all_ of the mass of the electron might be
electromagnetic in origin - and they had formulas (based on different
assumptions as to the shape and structure of the electron), such
as E= 3/4 * mc^2 (which is my favorite). But Henri Poincare was able
to show that these were not sufficient, for you would also need
an additional force to hold this semi-mechanical model together.
When Einstein derived E=mc^2 it became clear that mass is more of
a relationship between the energy and momentum of a (closed) system.
The complete Einstein equation is E^2/c^2 = p^2 + m^2 * c^2, which
I think I mentioned in the other post. And yes, p (momentum) is
a vector; it is a three-dimensional vector, which forms part of the
four vector: (E/c, px, py, pz). It is the _length_ of this so-called
4-momentum which gives the mass (and the rest energy). As a good
vector, it has the same length for all inertial observers, and hence
is a "Lorentz invariant".
Stolen freely from Peter Diehr to Mark Lambert on the Science echo.