Re: Photon, Momentum, Mass

"John Kennaugh" <JKNG@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:8d7JdEMSDRLGFwNG@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Jeckyl wrote:
"John Kennaugh" <JKNG@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:Q59C0ZLPYkKGFwyZ@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
What the PoR says is that you will always get the same law in any
inertial
FoR.
That's what I said
Whether that law is that the speed measured for light is c
I find your selective snipping unacceptable.

Why .. you were saying the the law is that the speed of measured light is c,
and you didn't give any exceptions to that. I was simply snipping the bits
that didn't add any information.

What I said (or rather what I should have said) was
"Whether that law is that the speed measured for light is c even if the
source is moving or whether it is that the speed is always c+v from a
source approaching at v."

So .. the speed measured for ligh is c

The speed of light is not c+v in any FoR though

Fair enough .. It does assume

Talk about selective snipping .. I said assume or derive. Now THAT was
dishonest

What assumes? The PoR makes no such assumption.

I said assume or derive

It is totally neutral on the subjects as to what the laws of physics are,
merely that they are not dependent on which inertial FoR they are tested
in.

Yes

(or at least derive) that one of the laws of
phyiscs is that the speed of light is a constant c

Ah .. now you have the rest of the sentece.

That has been observed experimentally
Exactly what do you claim has been observed and when?

That the speed of light is a constant .. has that not been shown
experimentally? Wasn't that theory disproven early last century when
predicted results from observations of stars was not found? Yeup .. here it
is: http://en.wikipedia.org/wiki/De_Sitter_double_star_experiment .. 1913
that was

All that had been shown in 1905 was that the speed of light is constant if
both source and detector are both stationary in the same inertial FoR.
That was interpreted by Einstein as meaning that the speed was constant
w.r.t the observer *because* of the widely accepted - but totally untested
view that the source could not possibly control the speed because light is
a wave travelling in aether and it is the aether which controls the speed
not the source. As no one now believes in the aether and as light is made
up of particles then with hindsight that assumption looks absurd. If it
turns out that light is after all source dependent then a century of
physics collapses like a pack of cards.
I have been asking for several years now for someone to point me towards
an experiment which shows source independence convincingly and so far I
haven't found one.
I am told there is nothing worth considering before 1964. It is an
incredibly difficult thing to test.

To construct a test .. yes .. but one can use the existing 'apparatus' of
the uiverse to make observation t osee if they agree with a given theory or
not. It appears that the idea of light being source dependant was dismissed
for that reason a good while ago

What I have found on this NG is a surprising lack of objectivity - people
who believe it is tested every day - who simply accept it as an article of
faith.

Maybe it doesn't need to be tested every day if its already been shown that
the speed of light is not source dependant?

The other myth which goes with it is the myth that every time SR makes an
accurate prediction it disproves the alternative Ballistic theory.

No .. what happened was tht ballistic / emitter theory made predictions and
got it wrong.

Even I who am neither a physicist nor a mathematician have shown that a
couple of things, said to rule out BaTh, do no such thing. The fact is
BaTh has a very strong tendency to give an identical answer to SR.

Really?

My real point is this. There is a strong case to be made to say that
physics took a wrong turn.

I don't see that a theory that was shown not to correctly predict restulst
is a strong case.

That when light was found to be particulate it should have been 'major
rethink time' and the downgrading of the wave model/Maxwell to an
approximation.

It was well and truly considered, and the theory you are championing was
probably the strongest contender against SR (once aether was ruled out).
Einstein was also looking at that as a solution earlier on, but found it
didn't work well mathematically. And then coffin was nailed shut when it
was shown not to correctly predict observations.

Logically if light is made of particles it works better without an aether.
Without an aether there is no reason to assume source independence.

Except when there is observations evidence that there can't be.

What you had was a classic battle between traditionalists headed by
Einstein and the radical approach put forward by Ritz.

You've got that backward. Einstein (and his peers) were far more radical in
their idea than Ritz.

Ritz was using VERY old ideas back from the days of Newton, who came up with
the corpuscular theory of light (see
http://en.wikipedia.org/wiki/Corpuscular_theory)

One reason Einstein won was because Ritz produced his theory in 1908 and
died in 1909.

The main reason was that the predictions of Ritz's theories failed whne
compared to actual obervation.

Not a good scientific reason for choosing one theory over another.

The reason you quote was not the reason it failed. It was an old theory
(like ether) and evidence showed it was not correct

Ritz theory seems to have been suppressed:

No .. just shown to be incorrect

Reviewer: Walter G. Hecker
Book "Richard Arthur Waldron The Wave and Ballistic Theories of Light - A
Critical Review", Frederick Muller Ltd., London 1977

"Waldron developed a ballistic theory of light on his own before learning
that Walter Ritz had already done it at about the time that Einstein
developed his 'Special Relativity'. Waldron shows with mathematical
accuracy and in excruciating detail, one by one, that all the so called
proofs of Einsteinian relativity (approx. 20) aren't proof at all but that
the experimental and observational results can be just as well explained
with the more pedestrian Ritzian relativity. Unfortunately the books
writing style is extremely dry and the back referencing to figures and
what was said earlier is hard to follow (References are to sections, but
the pages have no section headers). But he is so detailed and
conscientious in his proofs, that its a book worth having for any
'dissenter' regarding Einsteinian Relativity, special or general."

Have a read about Willem de Sitter .. the person mostly responsible for
showing Ritz theories were wrong.

If Physics had worked the way science is supposed to work (and rarely
does) then it should have accepted the particulate - no aether - source
dependent theory because without the ego's and prejudices of those wanting
to cling to the wave-in-aether model that is what the evidence was saying.

It did work as it should .. there were competing theories .. ether theory
got ruled out by MMX, and emission theory got rules out thru inconsitency
with observation

It is by far the simplest explanation of the MMX.

Simple isn't always correct.

Had that
happened there is absolutely no doubt that physics today would be
different to what it is. I cannot say it would be better. I cannot say it
would be worse but it would be different. I would have thought that
natural curiosity would make anyone who claims to be a scientist to be
interested in where that would have led. All debate is better for having
two opposing sides.

There were two sides (more than two) .. but incorrect theories have to be
eliminated .. no matter how nice or simple they are.

This is clearly absurd.
Some of the restulst are counter-intuititive to those who have seen the
restulst only, and not understand how they are derived.
I did not say the maths was absurd. Once you accept the second postulate
the maths follow and I do understand how they are derived. The absurdity
comes in trying to produce a physical model to go with the maths. Both
the
provenance of the second postulate and the physical consequences are
absurd.
Counter intuitive, and difficult to imagine when we have such a deeply
ingrained model of 3D space in our minds .. but not necessarily absurd

SR of course requires that the light in an observer FoR separates from
the
source at c+v so as to be c w.r.t that observer. If there is no aether
then how can anything have an effect on what speed light separates from
the source at, other than the source?

The light moves at c in the FoR of the source, and c at the FoR of the
observer. It is never observed as travelling at any other speed

That other things are moving with different velocities (including the
source) is not relevant. Light always travels at c from ANY inertial FoR

What makes it do so?

A very good question

A FoR is a mathematical abstraction it cannot make light travel at c w.r.t
itself.

You have it backward .. the FoR does nothing to the light. It doesn't
change how the light moves .. it does nothing.

Unfortunately the physical space it defines is equally devoid of any
physical entity which could take part in a physical process to do the job
either.

There is no job to be done .. there is not variation in the speed of light.
It isn't speeding up or slowing down .. it just travels.

The idea of light separating from the source at different speeds in
different FoR is what causes Doppler shift in SR.

Yes .. it separates at different speeds becuse the light always travels at c
... but the source is moving away. That is not a problem

If in a given FoR light separates at greater than c i.e. at c+v then the
wavelengths are stretched and when observed travelling at c w.r.t the
observer a lower frequency is measured.

That's fine

If in a given FoR light separates at c-v the wavelengths are compressed
and when observed travelling at c w.r.t the observer the frequency is
higher. I do not see why you consider this as not relevant it is as much a
part of the model as light always travelling at c in a FoR.

I never said it wasn't relevant.

It has to separate from the source at whatever speed makes it c w.r.t the
FoR

Light cares nothing about the source or the FoR .. it just travels. That
the source moves after it is emitted makes no difference. There is no
mecahnisam that is make light trabel at different speeds it is ALWAYS
travelling with speed c.

and Doppler shift is the result. Surely anyone trying to understand SR
needs to understand all its implications.

Of course

Do you find that implication somehow embarrassing?

No. Do you find it emabarrassing that the theory you support doesn't fit
observational data?

If so why.

If not .. why don't you. Of course the reason is that there should be no
embarassment if a theory is shown incorrect. There have been countless
physisct who have put forward theories that are proven wrong. That is how
science works .. it is all about refuting. The important thing is to learn
from this and more forward.

Essentially the denial of an aether means that the source must control
the
speed of light as there is nothing to prevent it.
No .. it does not .. the speed is simply always c

Is that a statement of faith or are you prepared to justify it with some
sort of logic.

Its been shown that source does not qaffect the speed of light.

One would logically assume that if a process is ejecting photons that
their speed would be the result of that process.

Only in a purely gailean/netonian world

If there is nothing physical surrounding the source there can be no
physical process which prevents the processes emitting it being what
controls it.

The speed light is emmited is not influence by anything .. it just travels
at c. There does not need to be aprocess that makes it faster or slower ..
because it is always the same

Quite simply if the speed of light is not dependent upon the physical
processes which generate it then what is it physically dependent upon?

A very deep question .. why is the speed of light c .. why do photons
travels at that speed and not some other speed.

All I get for an answer comes down to 'it is what the maths says'. Well of
course the maths says that. The maths are based upon the assumption that
it is so.

We have expermental evidence of the speed of light. We have obeervational
evidence that it is not source dependant. We hav eexperimental evidence
that there is no 'ether' FoR.

There are those who think that if they express 'its what the maths says'
in more sophisticated terminology that it will be more convincing.

According to relativity anything with mass increases its mass as its
speed increases
No .. relativity says mass is invariant
I think that physicists have redefined mass several times since
Einstein.
He writes "If a body takes up an amount of energy E then its inertial
mass
increases by E/cc."
What physicist call mass is the rest mass (invariant mass). That mass
does
not change with velocity.
until it becomes infinite when it reaches the speed of
light c. Therefore if you accept relativity a photon cannot have any
mass because if it had it would have to be infinite.

No .. relativity doesn't say that, it says the energy of the photon
wouldbe
infinite. The mass would remain at whatever the mass is, because mass
does
not chagne with velocity.

If you say so. I don't really care.

Obviously .. you've made up your mind to think it absurd and anything that
makes it less absurd is rejected by you.

No physics can invent what it wants, re-define what is mass etc.

It isn't redefining mass AFAIK

until it comes up with something which can be defended

It can be defened. SR makes predictions and those predictions are born out
by experiemental evidence.

If and when there is experimental evidence that shows SR is wrong.. then it
willbe modified or replaced.

and then insist that it was always the case even if Einstein said mass
increases with speed.

He didn't. The 'm' he used was always invariant mass. It has always been
invariant. hence the name

As I say I don't really care.

Obviously you've made up your mind and dont want to hear things contrary to
your deep seated assumption that SR must be wrong.

What is mass anyway? I don't pretend I know do you?

I don't think anyone know what it is .. all we can do is observe it.. just
like electical charge, spin etc

I can't argue is someone decides to redefine it.

Who is redefining it?

I thought that in theory there are two sorts of mass inertial mass and
gravitational mass which happen to be equal.

Which theory are you talking about?

Q1/ Are photons affected by gravity?
A/ Apparently so in that light is bent by massive objects i.e. the sun and
they gain energy if they fall from the top of a tower to the bottom.

You're getting into General relativity now.. in that case the light is bent
because space-time is bent.

Q2/ Do photons have momentum?
A/ Yes light does exert a small but detectable physical pressure when it
falls on something.

Yes .. they do .. the momentum comes from their energy ..given by E = pc

Q3/ Is the mass calculated from Q1 equal to that of Q2?
A/ - I don't know. Maybe you have an answer.

No .. SR says the mass (ie invariant mass) of a photon is zero. If it
wasn't zero, then there would be infinite energy in a phoont as given by E =
gamma.mc^2

I would be more interested to know how a photon stores its energy in
other
words what makes a low energy photon different to a higher energy
photon.
How does an electron store its charge. How dose a neutron store its mass.
I don't see why you're asking this or what difference it makes.
An electron is always the same, a neutron is always the same. A photon can
have a very wide range of energies.

Yeup .. the energy in it depends on the frequency of the light by E = hf

Are there lots of different types of photon or are they all the same but
somehow store different amounts of energy?

They have different energy.

To me the most interesting question in physics is what is a photon,

what is an electron. what is a neutrino. what is energy. what is
anything?
how does it store energy,

what is electrical charge. how does an electron have it.

how does that energy manifest itself in the form of frequency and
wavelength.

how do electirc and magnetic fields get generated from moving charges. what
is gravity

i.e. to explain the wave properties of light in terms of photons.

Yeup .. and the wave/particly duality

All very interesting questions indeed.

In many of these cases that answer is of the form 'mass is'.. and we just
give a name to it. what is it .. it is mass. If something is truly a
primitve property of the universe, then it is what it is, it is not made up
of something else.

OTOH a photon has
energy and energy and mass are equivalent.
The energyof a photon comes from momentum,
And momentum is defined as mv is it not or has that also been redefined!
Yes .. momentum reduces to mv at lower velocities .. reletavistic momentum
is defined differently

Are you going to elucidate? My limited understanding is that m = kMo where
k = 1/(sqr(1-vv/cc) where m is the relativistic mass and Mo is the rest
mass.

You're talking about the fairly usless idea of 'reletavstic mass' .. a
concept that physicist don't use (it was popular at one time, and is still
sometimes use in introductory material to help student ease from newtonian
ideas into SR).

The newtonian mv is a very accurate approximation from a series exapanion of
momentum. The other terms are incredibly small at the low velocities we
work with in the usual course of our lives.

The problem as I see it is if you say Mo is finite for a photon the
relativistic mass becomes infinite.

Yes .. that is why it is zero

OTOH if you make Mo=0 the relativistic mass becomes 0 so mv = 0 which used
to be momentum - by definition - I am sure a workaround has been found.

There is no need for a work around.

The formula is E^2 = (mc^2) ^2 + (pc)^2

p is momentum there, and depends on velcoity and the gamma factor

When mass (rest mass) is zero, this becomes

E^2 = (pc)^2
E = pc

Momentum without mass or different sorts of mass.

Momentum without mass .. it only needs mass at lower-then-c velocities

Again.. it appaears you have a lot of knowledge about the history of it,
and
are good at picking out all the things that seem absurd to you, and ignore
the important things.

It seems to me that a relativist is a bit like an estate agent who wants
to sell me a house by guiding me via the scenic route showing me that the
house is near to the park, and a good school. I am like a buyer who has
done my own poking around and know that the estate agent is carefully
avoiding the nearby pig farm, sewage works and landfill site.
If the estate agent gave a more balanced view then perhaps I would not
feel obliged to try and redress the balance.

Fine .. hopefully you'll learn something from this forum (I know I've learnt
quite a bit here .. much of it indeirectly, as questions I see lead me to
look for answers for myself).

Having thought again it really isn't like that. It is not that the estate
agent is trying to avoid the nearby pig farm, sewage works and landfill
site. He doesn't know they are there because his firm has been using the
scenic route for years. He is inclined not to believe they are there even
when they are pointed out to him. If I put doubts in his mind he goes back
to the office for reassurance from his colleagues who are also only
familiar with the scenic route.

I'm not sure what doubt you think you're introducing .. the doubts seem to
be only in your mind.

Next thing you know you might be saying things
actually get crushed by distance contraction, when their proper length is
unchanged.

Not me. Of course I may point out that while in SR length contraction is
simply something which appears in the maths

It appear in experiment as well

the only physical model compatible with SR is LET. Now in LET contraction
is physical not merely mathematical

That makes no sense unless there is a absolute frome of reference.

and my understanding is that modern advocates of the theory say that if
there is an aether as Per Maxwell/Lorentz electrodynamics then the maths
says that the orbit of an electron orbiting a nucleus moving through the
aether would become elliptical and this ties in with the amount of
contraction predicted. Not my strong subject. If you are interested
consult a modern advocate of the theory.

I'll look it up

The timing was interesting in that the Bohr model of the atom was not
until 1913 so Lorentz's 'guess' that movement through the aether could
affect dimensions could not be shown to be mathematically sound until
after SR had replaced LET.

There is no 'crushing' involved if by 'crushing' you imply mechanical
damage. Merely that each atom is an electromagnetic sub-system which is
affected by movement through the electromagnetic aether.


.

Relevant Pages

  • Re: Photon, Momentum, Mass
    ... say the same laws of physics apply in all inertial frames of referenec (ie ... "Waldron developed a ballistic theory of light on his own before learning that Walter Ritz had already done it at about the time that Einstein developed his 'Special Relativity'. ... The idea of light separating from the source at different speeds in different FoR is what causes Doppler shift in SR. ... He writes "If a body takes up an amount of energy E then its inertial mass ...
    (sci.physics.relativity)
  • Re: Is physics a science?
    ... doesn't control the speed of light - that leaves the observer. ... Nothing physical is "frame dependent" ... This comes as great news to the physics community. ... light separates from the source at different speeds ...
    (sci.physics.relativity)
  • Re: Lightspeed exceeded
    ... >>>thrown by bigger force in various directions and speeds. ... >> that the speed of light is c w.r.t the observer observing it but makes ... This is essential to the difference between physics and mathematics. ...
    (sci.physics.relativity)
  • Re: "How Does Light Know How Fast to Travel?"
    ... specific to it is the observer. ... so photons travel at all possible speeds through physical space. ... Now according to relativity if as A is coincident with B they see a ... physics says the same. ...
    (sci.physics.relativity)
  • Re: relativistic thermodynamics (temperature in inertial frames)
    ... I'm a layman with an interest in physics. ... distribution of speeds ... what would be the distribution of velocities perceived by a moving ... observer; the formula would compress the range of those velocities to ...
    (sci.physics.relativity)
Loading