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Exchange Particles and Gravity
Name: Ilian T.
Status: educator
Age: 30s
Location: N/A
Country: N/A
Date: Saturday, April 20, 2002 8:17:44 PM
Question:
Can someone please explain how exchange particles cause
attractive forces? The analogy of two ice-skaters throwing tennis balls
at each other illustrates how an exchange of momentum can cause a
repulsive force, but I fail to see how a force such as gravity can be
explained in this way.
Replies:
I am really at the edge of my expertise on this, but it is my understanding
from reading the "popular" literature, that every field (or force) can be
interpreted as an exchange of particles. Photons for the electromagnetic
field.
That is just the way the mathematical physics turns out. Like many of the
concepts that arise from quantum mechanics, we do not have any experience or
any very good "pictures" for what is going on. We just do not live in that
world. Spin is a good example of a quantity that is certainly "real", but
what "is" it? It is the result of the Q.M. treatment -- that is the best we
can do.
An even more elusive, but familiar, quantity is "energy". What "is" energy?
We really do not know. We know how it behaves, we know how to calculate it
for various formulas. But that does not really tell us what it "is".
Vince Calder
Ilian,
One thing very important to consider with such theories is the wave/particle
nature of matter. On a large scale, objects all have a clearly defined
energy and momentum. On the scale of an individual particle, such is not
the case. Quantum research shows that what we commonly think of as
particles sometimes behave as waves and sometimes as a combination of wave
and particle. An individual particle does not necessarily have a clearly
defined momentum or energy. Interactions between two particles is not the
same as interaction between two charged balls. Particles don't even have
clearly defined positions: they have states of existence. Interaction
between individual particles is not understood. We know that particle
interaction is not just force, momentum, energy. We know interaction can be
viewed according to many different models. We do not know which model is
correct, if any are even close. The basis for the graviton model is the
fact that gravity is a 1/(distance-squared) force. If a mass emits
gravitons in all directions, the density of gravitons will decrease as
1/(distance-squared) as they move away from that emitting mass. If the
effect on another mass is proportional to the number of gravitons that hit
the second mass, a graviton law automatically produces a
1/(distance-squared) relationship.
It is very similar to electric force being "transmitted" between particles
by photons of light. In either case, I do not believe the actual mechanism
is understood. It just seems to match the data that has been measured.
Dr. Ken Mellendorf
Physics Instructor
Illinois Central College
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