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Fields and Forces



Dear Dr. Beaty,

Thank you for your reply to my question regarding neutron star formation.
Your answer, however, raises another question. You wrote, with regard
to my statement that the electrical force is 10^40 stronger than the
gravitational force:

The above is a popular misconception...

(snip)

In truth, the constants in the equations for gravity and for electrical
force are of vastly different magnitude. Many people therefor say
that >the electrical "force" is stronger than the gravity "force", but
this
statement is wrong.

Thanks for the practical demonstration that given tremenous mass (and
close distance) a gravitational field can produce a far greater force
than an electrical field can electrical force. I should have caught this
from manipulating the equations.


In addition, you wrote:

Many books say that there are four forces: electrical, gravity, weak
nuclear, and strong nuclear. This is wrong. There are four kinds of
FIELD, and four kinds of exchange-particle which create the fields,
but as physics-types should know, a field is not a force.

O.K .. my books do too. I sought an explanation of the difference
between a force and a field. This is somewhat confusing... the books
containing Dr. Feyman's Lectures On Physics consistently refer to four
fundamental FORCES. Is this a matter of semantics or one of usage (i.e.,
are they are FIELDS with potential to act until they they do act and only
at that time do they manifest a FORCE) or is there a more fundamental
difference between a field and a force?

In particular, how can we draw this distinction for gravity when there is
no theory for quantum gravity? I have been taught that the existence of
gravitons is not proved. If that is so, then what is the practical
value of defining gravity as a FIELD where the FORCE is mediated by
virtual gravitons?

Am I incorrect to state that the electric field PRODUCES an attractive or
repulsive force between charged objects, which varies as the inverse
square of distance and that this FORCE can change the momenta of the
objects.

If I am.... Aggghhhh!!!!! I think I'll become a physician instead of
a physicist!

Seriously, I tried to access the glossary on your web page but link was
broken.

My Dad emailed me a copy of the article in the Boston Globe article that
quoted you regarding errors in textbooks. For whatever it is worth to
you, the most frustrating thing I find as a student is "busy" textbooks
that start you down one topic and then branch off into some bizzare
example of how "relevant" the topic is. It's all fluff and no content.
Looking something up in a high school text is like getting random and
weird hits out of an Internet search engine. Look for "force" in a high
school text and you are most likly to find a picture of Darth Vader
holding a light saber. More frustrating is to do problems that look like
they were wrttten by someone other than the text author. I find it much
better to work a few good problems -- even if they are hard -- than the
usually boring problems that have no real application of the text
material.

Golly...speaking of Darth Vader... I must be the only teenager who
doesn't have an explanation for what the "Force" is. :)

Perhaps I should see Star Wars. I'd rather not -- I like science better
than science fiction.

I'd appreciate any internet references that you have that might claify
the field/force distinction further.

Thanks for your help. I can't offer much in the way of discussion -- but
I sure will read everything!

Lee Wilmoth Lerner
Fairhope High School, Fairhope, AL USA Email via:
lw.lerner@juno.com
“But I don't have to know an answer. I don't feel frightened by not
knowing things,
by being lost in the mysterious universe....” -- Richard Feynman
"...unless, of course, I have a test" -- LWL


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