On Sep 5, 5:02 pm, Jim Kelley wrote:
....

I'd like to offer m = E/c^2 as a guess.

73, ac6xg

A link is worth a thousand words (perhaps 10k-100k of Richard's...):
http://www.newton.dep.anl.gov/askasc...0/phy00332.htm
(in particular the first paragraph of the second response).

On Thu, 06 Sep 2007 12:47:46 -0700, K7ITM wrote:

On Sep 5, 5:02 pm, Jim Kelley wrote:
...

I'd like to offer m = E/c^2 as a guess.

73, ac6xg

A link is worth a thousand words (perhaps 10k-100k of Richard's...):
http://www.newton.dep.anl.gov/askasc...0/phy00332.htm
(in particular the first paragraph of the second response).

Hi Tom,

Your link is over valued (there is no second response), but it
maintains the standard of excellence here in the tradition of 10k-100k
more words than quantifiables - and someone else doing the work.

Care to walk us through your proffered math?

Well, I doubt it. Others may be interested in the curious form of
argument offered to a 15 year old however.

"For a particle with no mass, the relation reduces to E=pc."

The long and short of it is that there is no discussion of mass for a
photon (it is simply defined not to exist) and instead there is a
shuffle of math that youngster must imagine this bozo is pulling the
wool over his eyes through substituting p for Planck's constant h, and
c for Planck's energy formula variable v. This wool pulling is
another favorite past time here too.

Of course, there may be other meanings behind
"E=pc."
but in the model of thorough work, the description of terms is sadly
poor.

The typical legacy of offering links. It has all the appeal of a
Physicist's joke:
"How many milliseconds does it take to do a 5 minute car wash?"

73's
Richard Clark, KB7QHC

On Sep 6, 2:53 pm, Richard Clark wrote:
....(there is no second response)...

Pity you have so much trouble reading...

Richard Clark wrote:

On Thu, 06 Sep 2007 12:47:46 -0700, K7ITM wrote:


On Sep 5, 5:02 pm, Jim Kelley wrote:
...

I'd like to offer m = E/c^2 as a guess.

73, ac6xg

"E=pc."

Yes, and p=mv, so when v=c as is true for photons, and we substitute
mc for p in the equation above and then solve for m (the mass of a
photon was the original question), we're back at the equation offered
previously.

But we usually relate more directly to the frequency (or wavelength)
of the photon rather than its energy or momentum, so in such a case
E=h*nu would provide a more direct route to its mass equivalent.

ac6xg

On Thu, 06 Sep 2007 16:07:09 -0700, Jim Kelley
wrote:

Richard Clark wrote:

On Thu, 06 Sep 2007 12:47:46 -0700, K7ITM wrote:


On Sep 5, 5:02 pm, Jim Kelley wrote:
...

I'd like to offer m = E/c^2 as a guess.

73, ac6xg

"E=pc."

Yes, and p=mv,

Hi Jim,

Tom opines about my reading, but it is about the writing from the good
doctor that we find (in regard to your snippet above):
"we find that the momentum relation p=mv is
only an approximation. It is only correct when speed (v) is much
smaller than the speed of light (c).
which distinctly contradicts your tie-in:
so when v=c as is true for photons, and we substitute
mc for p in the equation above and then solve for m (the mass of a
photon was the original question), we're back at the equation offered
previously.

The circularity of Dr. Ken Mellendorf's foggy writing might suggest
it, if it weren't otherwise nipped in the bud by the bald statement.
"For a particle with no mass, the relation reduces to E=pc.
This works for a photon."

Hence the proximity of this to p=mv is textual, not factual.

What is the term p? Could it be (p)hoton? I've speculated about
Planck's constant (which you comment upon, below), but I find it very
sloppy writing for Dr. Mellendorf to wander into his own naming
conventions. Migrating through
E = mc²
something all can agree is a fair basis to begin with, we then have
expressly for a (p)hoton:
E = pc
Substituting for the previous E
pc = mc²
divide both sides by c
p = mc
which to me is new territory. What is mass times the speed of light
for a particle that has no mass?

Perhaps Tom's special reading skills can rescue this p term from the
oblivion of E = 0 for a (p)hoton.

But we usually relate more directly to the frequency (or wavelength)
of the photon rather than its energy or momentum, so in such a case
E=h*nu would provide a more direct route to its mass equivalent.

Yes, and it seems your daughter trumped me on Planck once before. ;-)

It is exceedingly obvious that the link offered amounts to
considerable wool gathering. Or maybe its the late hour....

73's
Richard Clark, KB7QHC

Richard Clark wrote:
What is mass times the speed of light
for a particle that has no mass?

A nonsense question since "no mass" for a
photon is associated with it being *at rest*,
i.e. *not moving at the speed of light*.

Perhaps Tom's special reading skills can rescue this p term from the
oblivion of E = 0 for a (p)hoton.

For a photon possessing zero rest mass,
traveling at the speed of light yields
a finite measurable mass.
--
73, Cecil http://www.w5dxp.com

On Sep 7, 12:51 am, Richard Clark wrote:

The circularity of Dr. Ken Mellendorf's foggy writing might suggest
it, if it weren't otherwise nipped in the bud by the bald statement.

On the other hand perhaps Dr. Mellendorf has some expertise in the
subject.

What is the term p? Could it be (p)hoton? I've speculated about
Planck's constant (which you comment upon, below), but I find it very
sloppy writing for Dr. Mellendorf to wander into his own naming
conventions.

I think you should make those comments directly to him so that he an
opportunity to respond. Shall I forward them for you? :-)

What is mass times the speed of light
for a particle that has no mass?

Seems like something is wrong in that sentence, doesn't it.

Perhaps Tom's special reading skills can rescue this p term from the
oblivion of E = 0 for a (p)hoton.

It's also possible that since E=0 is wrong, the assumption that p=0
might also be wrong. If not, then you'll need to explain radiation
pressure in an all new way.

Yes, and it seems your daughter trumped me on Planck once before. ;-)

She's better at math than I ever was.

73, ac6xg

On Sep 7, 9:08 am, Jim Kelley wrote:
On Sep 7, 12:51 am, Richard Clark wrote:

The circularity of Dr. Ken Mellendorf's foggy writing might suggest
it, if it weren't otherwise nipped in the bud by the bald statement.

On the other hand perhaps Dr. Mellendorf has some expertise in the
subject.

What is the term p? Could it be (p)hoton? I've speculated about
Planck's constant (which you comment upon, below), but I find it very
sloppy writing for Dr. Mellendorf to wander into his own naming
conventions.

I think you should make those comments directly to him so that he an
opportunity to respond. Shall I forward them for you? :-)

What is mass times the speed of light
for a particle that has no mass?

Seems like something is wrong in that sentence, doesn't it.

Perhaps Tom's special reading skills can rescue this p term from the
oblivion of E = 0 for a (p)hoton.

It's also possible that since E=0 is wrong, the assumption that p=0
might also be wrong. If not, then you'll need to explain radiation
pressure in an all new way.

Yes, and it seems your daughter trumped me on Planck once before. ;-)

She's better at math than I ever was.

73, ac6xg

For the lurkers who may care to sift a tiny bit of wheat from the
chaff, see common physics symbol usage at http://www.alcyone.com/max/reference...s/symbols.html,
http://selland.boisestate.edu/jbrenn...cs_symbols.htm,
http://www.hazelwood.k12.mo.us/~gric...b/formulas.htm and
others. If you're reading physics writings, it helps to have an
understanding of the language of the physicist.

See concise explanations about photon momentum and relativistic
momentum, energy and mass in general at
http://hyperphysics.phy-astr.gsu.edu...iv/relmom.html,
http://physics.mtsu.edu/~phys2020/Le..._momentum.html
and others.