
NEWTON, Ask A Scientist!
Name: Unknown
Status: N/A
Age: N/A
Location: N/A
Country: N/A
Date: Around 1993

In an interesting book by Paul Davies and John Gribbin, called "THE MATTER MYTH". It explains that the concept of energy was originally introduced as a purely theoretical quantity that could be changed and exchanged among its various forms. We cannot see or touch energy, yet "we accept that it really exists because we are so used to discussing it." I am one who accepts the existence of energy. In fact, I think it is a clearer concept than Matter itself. So is it then, that ENERGY is a property of MATTER, or the other way around?

Energy does exist. But, the concept of matter disappearing and energy appearing in its place is really not quite correct. So, what is energy? It is a quantity that describes the current state of a system, just as charge, mass, velocity, position, etc., also would describe the current state of a system. Moreover, like charge and mass and momentum (but not velocity), energy is additive - the energy of two objects is the sum of their individual energies (before they start interacting and interfering). And, energy is always conserved, just as momentum and charge are. Einstein's great discovery/idea was that mass is not conserved, and that the true energy of an object was not just the sum of the various parts that people had always assumed (kinetic energy from motion, chemical energy from interaction atoms) but also contained a huge piece that was associated with the mass of the object. So, does mass turn into energy? No! But, the energy that always was there, contained in the mass of the particle, can be released if the mass is reduced. Does energy ever leave a physical object and go off on its own?


It always is just one property of a particle (or collection of particles) that always has some other properties, such as spin, mass, charge, etc. but, there is some difference between the 3 types of neutrinos, and there is also a distinct difference between neutrinos and anti neutrinos (they spin the opposite way). The photon which carries light is even less "pure energy", because it carries along with it electric and magnetic fields, in some sense, and has a polarization as well.

A. Smith

I think it can also be argued that energy does NOT really xist. One can approach it from a viewpoint that energy, like momentum, is a human concept that is useful in understanding nature.

Nature does whatever it wants to do, and it does it in ways which are mysterious and amazing. Whether the phenomenon is superfluidity, neutron decay, or photon scattering, nature just DOES it.

Humans make measurements of these events and have come up with terms like "mass," "energy," "momentum," "charge" and so on to help them quantify what they measure. Humans also come up with equations (Schroedinger equation, Einstein equation, Newton's laws, Maxwell's equations, etc.) which relate things like energy, mass, and so on.

Fortunately, nature behaves in ways that are in agreement with the mathematics that people understand (so far). Newton's laws are able to describe "mechanics" using simple algebra. Schroedinger's equation requires differential equations and probability functions to describe "quantum mechanics." Einstein's equations involve tensors. Nobody knows how to properly describe quantum gravity, but some people think that "string theory" might do it.

Humans can calculate the "energy" of systems and things and make useful predictions. So far, science has been spectacularly successful at using these terms to understand the operation of nature to astounding precision. "Energy" is one quantity that is universal in all branches of science, and is most useful. Other quantities, like momentum, are also universal, but are not as useful for answering questions.

As to whether energy is a property of matter, I think it depends what kind of science you are doing. If you are doing simple mechanics, then no, your masses have no energy of themselves. If you are colliding electrons and positrons, then yes, all of your equations involve total energy and rest energy of the matter. I do not know enough of relativity or string theory to know how these fields relate energy or matter.

Bob Erck

Click here to return to the Physics Archives



Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Weclome To Newton

Argonne National Laboratory