🚀 go-pugleaf

On Jul 14, 8:09 am, "Y.Porat" <y.y.po...@gmail.com> wrote:
> On Jul 14, 9:26 am, Pentcho Valev <pva...@yahoo.com> wrote:
>
>
>
> > Tom Roberts wrote in sci.physics.relativity:
>
> > > develope...@hotmail.com wrote:
> > > > If there is no such thing as absolute motion, it follow there is no
> > > > such thing as absolute rest.  How, then, can we speak of an object's
> > > > rest mass?  Rest wrt what?
>
> > > The underlying concept is of invariant mass. This is an intrinsic
> > > property of an object, and in relativity is the closest analog of what
> > > "mass" meant in Newtonian mechanics.
>
> > > The phrase "rest mass" hearkens back to the old days in which there was
> > > confusion between mass (aka invariant mass) and "relativistic mass".
> > > "Relativistic mass" is not really mass, and is frame dependent so it is
> > > not intrinsic to an object, either; it is numerically equal to the
> > > energy of the object, and "energy" is a much better name for this
> > > quantity than "relativistic mass". The "relativistic mass" of an object
> > > in its rest frame is equal to its invariant mass, or in the usual
> > > shortcut way of speaking, its rest mass.
>
> > > So this is "rest relative to the object itself". In modern physics, the
> > > first word of "invariant mass", and the first word of "rest mass", are
> > > redundant, because the concept "mass" includes those aspects as well.
> > > The first word of "relativistic mass" is an oxymoron.
>
> > > Tom Roberts
>
> > Unfortunately Roberts Roberts the relativistic verbiage contains too
> > many oxymorons. As far as photons are concerned, the only important
> > question is:
>
> > Does the speed of photons vary with the gravitational potential, as
> > the speed of other particles does, and, equivalently, does the speed
> > of photons vary with the relative speed of the light source and the
> > observer, as the speed of other particles does?
>
> > Roberts Roberts this question is directly relevant to the axioms of
> > relativity and for that reason I called it "the only important
> > question". The question "Do photons have mass?" is important but not
> > directly relevant.
>
> > Roberts Roberts you have already given half of the answer:
>
> > Tom Roberts wrote in sci.physics.relativity:
>
> > > Pentcho Valev wrote:
> > > > CAN THE SPEED OF LIGHT EXCEED 300000 km/s IN A GRAVITATIONAL FIELD?
> > > Sure, depending on the physical conditions of the measurement. It can
> > > also be less than "300000 km/s" (by which I assume you really mean the
> > > standard value for c). And this can happen even for an accelerated
> > > observer in a region without any significant gravitation (e.g. in
> > > Minkowski spacetime).
> > > Tom Roberts tjrobe...@lucent.com
>
> > Pentcho Valev- Hide quoted text -
>
> > - Show quoted text -
>
> ------------
> To your question whether the photon has mass
>
> the answwer is Yes
> it has mass  a verylittl eone
> 2
> there is only jsy one kind of mass
> you can choose any name for it
> but jus tone knd of mass
> (if you think about 'relatiovistic mass'
> better forget about it
> and
> how come that the phton has mas
> and still movwes at c
> ask Wormley  he is a cleaver innovative sciensut
> alternatively youcan ask Gisse
>
> the 23 years old  boy from Alasks
> (that could not finish a Bsc !!
> and sits all day on the net ...teaching the world physics ....)
> He is the new Einstien
> of the 21 century
> (and may be of Alaska (University )as well !!who knowes ??
>
> Y.Porat
> -------------------

I don't agree.

A water wave can hit a wall, with force.
That doesn't mean it has intrinsic mass.

Keeping in mind that a photon is just a wave packet. It is not a
particle of dust.

And I gave the example yesterday if you missed it, that if an observer
has a switch, and as a high speed rocket passes him, he flips the
switch. The rocket is going 1 million miles per hour towards the moon,
and the observer is stationary.
 When he flips the switch, his high beam beside him and the one on the
ship will shine a beam onto a detector on the moon.

If light had mass, it would have momentum, and his beam would strike
the moon first.
Since it does not have mass, it has no forward momentum towards the
moon, and hence both beams hit the moon at the same time.