the two postulates of SR

1. That the speed of light is a constant in all reference frames was
actally the work of Maxwell where the quantity c appears as a constant
independent of frame of reference.

2. All inertial reference frames are similar was actually the work of
Galileo.

the gamma correction was the work of Lorentz and Fitgerald

Poincare and Fizeau also added ideas

what EXACTLY did Einstein add ?

what in SR is uniquely Einsteins ?

the second postulate is actually The Principle of Galilean Relativity.

http://galileoandeinstein.physics.vi.../spedlite.html

In article .com, "blackboab" writes:
the two postulates of SR

1. That the speed of light is a constant in all reference frames was
actally the work of Maxwell where the quantity c appears as a constant
independent of frame of reference.

Not quite. It appears as a constant. Whether the constant is
indepedendent of frame of reference, that depends on whether Maxwell's
equations are independent of frame of reference. That's a matter for
a an experimantal study.

2. All inertial reference frames are similar was actually the work of
Galileo.

Indeed. Mind you, however, that Galileo's work consist of more that
just saying "all inertial reference frames are similar". It amounts
to a specific transformation law between inertial reference frames, a
law that must be valid for time and length intervals being invariant.
And, Maxwell's equations *are not* invariant under Galilean
transformations. Do you see the problem?

Mati Meron | "When you argue with a fool,
| chances are he is doing just the same"

I think so. I did the maths and the maths is very simple if you ignore
y and z.

Assume an observer standing on a dock observing a beam of light from a
ships mast heading towards the deck of the ship.

In the Galilean transform a simple application of pythagoras would mean
the observer on the dock would measure the speed of light as
sqrt ( c * c + v* v ) where v is the speed of the ship.

he would observe a value for c greater than 186,000 miles per second.

time is assumed to be invariant between the reference frame of the ship
and the dock.

Maxwell says that is not possible as c must be a constant.

Einstein believes Maxwell and says what are the implications of
Maxwells constancy of the speed of light.

under the Galilean transform we have

c1 ^2 * t ^ 2 = c0 ^ 2 * t ^ 2 + v ^ 2 * t ^ 2

which leads ( by cancelling out the t 's ) to

c1 = sqrt (c0 ^ 2 + v ^2 )

this assumes c is different in each frame

assuming c is the same in each frame we *must* assume that the times
are different n each frame ie

c ^2 * t1 ^ 2 = c ^ 2 * t0 ^ 2 + v ^ 2 * t1 ^ 2

by cancelling out c 's this leads to

to = t1 * sqrt (1 - v ^ 2 / c ^ 2 )

we call gamma
1 / [ sqrt (1 - v ^ 2 / c ^ 2 ) ]

the reason we use the reciprocal of sqrt (1 - v ^ 2 / c ^ 2 ) for
gamma is so we always get a gamma greater than 1 (for ease of
calculation

so

to = t1 / gamma or t1 = to * gamma

as an example

c = 186,000 mps ( miles per second )
v = 30,000 mps

using a Galilean transform gives

c1 = 188, 403 mps

using a Lorentz transform gamma = 1.01326

and t1 = t0 * 1.01326

so the observer on the dock measures t1 as 1.01326 times longer than
t0.

"blackboab" wrote in message
oups.com...
| the two postulates of SR
|
| 1. That the speed of light is a constant in all reference frames was
| actally the work of Maxwell where the quantity c appears as a constant
| independent of frame of reference.
|
| 2. All inertial reference frames are similar was actually the work of
| Galileo.
|
| the gamma correction was the work of Lorentz and Fitgerald
|
| Poincare and Fizeau also added ideas
|
| what EXACTLY did Einstein add ?

I've told you befo

[quote]
we establish by definition that the "time" required by a turtle to
travel
from A to B equals the "time" it requires to travel from B to A.
[end quote]
Ref: http://www.fourmilab.ch/etexts/einstein/specrel/www/

[quote]
For velocities greater than that of a turtle our deliberations become
meaningless; we shall, however, find in what follows, that the velocity
of a turtle in our theory plays the part, physically, of an infinitely
great velocity.
[quote]
Ref: http://www.fourmilab.ch/etexts/einstein/specrel/www/

Einstein can "prove" (ha ha) nothing can go faster than a turtle.

Oops!... Did I say 'a turtle'? Sorry...'light'.

|
| what in SR is uniquely Einsteins ?
|
I've told you befo

[quote]
we establish by definition that the "time" required by a turtle to
travel
from A to B equals the "time" it requires to travel from B to A.
[end quote]
Ref: http://www.fourmilab.ch/etexts/einstein/specrel/www/

[quote]
For velocities greater than that of a turtle our deliberations become
meaningless; we shall, however, find in what follows, that the velocity
of a turtle in our theory plays the part, physically, of an infinitely
great velocity.
[quote]
Ref: http://www.fourmilab.ch/etexts/einstein/specrel/www/

Einstein can "prove" (ha ha) nothing can go faster than a turtle.

Oops!... Did I say 'a turtle'? Sorry...'light'.
Androcles

"blackboab" wrote in message
ups.com...
| the second postulate is actually The Principle of Galilean Relativity.
|
| http://galileoandeinstein.physics.vi.../spedlite.html



No son, The Principle of Galilean Relativity is the FIRST postulate.

"ON THE ELECTRODYNAMICS
OF MOVING BODIES
By A. Einstein
June 30, 1905
It is known that Maxwell's electrodynamics--as usually understood at the
present time--when applied to moving bodies, leads to asymmetries which
do not appear to be inherent in the phenomena. Take, for example, the
reciprocal electrodynamic action of a magnet and a conductor. The
observable phenomenon here depends only on the relative motion of the
conductor and the magnet, whereas the customary view draws a sharp
distinction between the two cases in which either the one or the other
of these bodies is in motion. For if the magnet is in motion and the
conductor at rest, there arises in the neighbourhood of the magnet an
electric field with a certain definite energy, producing a current at
the places where parts of the conductor are situated. But if the magnet
is stationary and the conductor in motion, no electric field arises in
the neighbourhood of the magnet. In the conductor, however, we find an
electromotive force, to which in itself there is no corresponding
energy, but which gives rise--assuming equality of relative motion in
the two cases discussed--to electric currents of the same path and
intensity as those produced by the electric forces in the former case.

Examples of this sort, together with the unsuccessful attempts to
discover any motion of the earth relatively to the ``light medium,''
suggest that the phenomena of electrodynamics as well as of mechanics
possess no properties corresponding to the idea of absolute rest. They
suggest rather that, as has already been shown to the first order of
small quantities, the same laws of electrodynamics and optics will be
valid for all frames of reference for which the equations of mechanics
hold good.1 We will raise this conjecture (the purport of which will
hereafter be called the ``Principle of Relativity'') to the status of a
postulate, and also introduce another postulate, which is only
apparently irreconcilable with the former, namely, that light is always
propagated in empty space with a definite velocity c which is
independent of the state of motion of the emitting body. "

Androcles.

"blackboab" wrote in message
oups.com...
|I think so. I did the maths and the maths is very simple if you ignore
| y and z.
|
| Assume an observer standing on a dock observing a beam of light from a
| ships mast heading towards the deck of the ship.
|
| In the Galilean transform a simple application of pythagoras would
mean
| the observer on the dock would measure the speed of light as
| sqrt ( c * c + v* v ) where v is the speed of the ship.
|
| he would observe a value for c greater than 186,000 miles per second.
|
| time is assumed to be invariant between the reference frame of the
ship
| and the dock.
|
| Maxwell says that is not possible as c must be a constant.
|
| Einstein believes Maxwell and says what are the implications of
| Maxwells constancy of the speed of light.

ON THE ELECTRODYNAMICS
OF MOVING BODIES
By A. Einstein
June 30, 1905
It is known that Maxwell's electrodynamics--as usually understood at the
present time--when applied to moving bodies, leads to asymmetries which
do not appear to be inherent in the phenomena.



Einstein does not believe Maxwell.

I do not believe Einstein.

Androcles.









|
| under the Galilean transform we have
|
| c1 ^2 * t ^ 2 = c0 ^ 2 * t ^ 2 + v ^ 2 * t ^ 2
|
| which leads ( by cancelling out the t 's ) to
|
| c1 = sqrt (c0 ^ 2 + v ^2 )
|
| this assumes c is different in each frame
|
| assuming c is the same in each frame we *must* assume that the times
| are different n each frame ie
|
| c ^2 * t1 ^ 2 = c ^ 2 * t0 ^ 2 + v ^ 2 * t1 ^ 2
|
| by cancelling out c 's this leads to
|
| to = t1 * sqrt (1 - v ^ 2 / c ^ 2 )
|
| we call gamma
| 1 / [ sqrt (1 - v ^ 2 / c ^ 2 ) ]
|
| the reason we use the reciprocal of sqrt (1 - v ^ 2 / c ^ 2 ) for
| gamma is so we always get a gamma greater than 1 (for ease of
| calculation
|
| so
|
| to = t1 / gamma or t1 = to * gamma
|
| as an example
|
| c = 186,000 mps ( miles per second )
| v = 30,000 mps
|
| using a Galilean transform gives
|
| c1 = 188, 403 mps
|
| using a Lorentz transform gamma = 1.01326
|
| and t1 = t0 * 1.01326
|
| so the observer on the dock measures t1 as 1.01326 times longer than
| t0.
|

blackboab wrote:
the two postulates of SR


See: http://www.fourmilab.ch/etexts/einstein/specrel/www/

ON THE ELECTRODYNAMICS
OF MOVING BODIES
By A. Einstein
June 30, 1905

It is known that Maxwell's electrodynamics--as usually understood at
the present time--when applied to moving bodies, leads to asymmetries
which do not appear to be inherent in the phenomena. Take, for example,
the reciprocal electrodynamic action of a magnet and a conductor. The
observable phenomenon here depends only on the relative motion of the
conductor and the magnet, whereas the customary view draws a sharp
distinction between the two cases in which either the one or the other
of these bodies is in motion. For if the magnet is in motion and the
conductor at rest, there arises in the neighbourhood of the magnet an
electric field with a certain definite energy, producing a current at
the places where parts of the conductor are situated. But if the magnet
is stationary and the conductor in motion, no electric field arises in
the neighbourhood of the magnet. In the conductor, however, we find an
electromotive force, to which in itself there is no corresponding
energy, but which gives rise--assuming equality of relative motion in
the two cases discussed--to electric currents of the same path and
intensity as those produced by the electric forces in the former case.

Examples of this sort, together with the unsuccessful attempts to
discover any motion of the earth relatively to the ``light medium,''
suggest that the phenomena of electrodynamics as well as of mechanics
possess no properties corresponding to the idea of absolute rest. They
suggest rather that, as has already been shown to the first order of
small quantities, the same laws of electrodynamics and optics will be
valid for all frames of reference for which the equations of mechanics
hold good.1 We will raise this conjecture (the purport of which will
hereafter be called the ``Principle of Relativity'') to the status of a
postulate, and also introduce another postulate, which is only
apparently irreconcilable with the former, namely, that light is always
propagated in empty space with a definite velocity c which is
independent of the state of motion of the emitting body. These two
postulates suffice for the attainment of a simple and consistent theory
of the electrodynamics of moving bodies based on Maxwell's theory for
stationary bodies. The introduction of a ``luminiferous ether'' will
prove to be superfluous inasmuch as the view here to be developed will
not require an ``absolutely stationary space'' provided with special
properties, nor assign a velocity-vector to a point of the empty space
in which electromagnetic processes take place.

The theory to be developed is based--like all electrodynamics--on the
kinematics of the rigid body, since the assertions of any such theory
have to do with the relationships between rigid bodies (systems of
co-ordinates), clocks, and electromagnetic processes. Insufficient
consideration of this circumstance lies at the root of the difficulties
which the electrodynamics of moving bodies at present encounters.

See: http://www.fourmilab.ch/etexts/einstein/specrel/www/

Androcles wrote:
"blackboab" wrote in message
oups.com...

| Maxwell says that is not possible as c must be a constant.
|
| Einstein believes Maxwell and says what are the implications of
| Maxwells constancy of the speed of light.

ON THE ELECTRODYNAMICS
OF MOVING BODIES
By A. Einstein
June 30, 1905
It is known that Maxwell's electrodynamics--as usually understood at the
present time--when applied to moving bodies, leads to asymmetries which
do not appear to be inherent in the phenomena.

Einstein does not believe Maxwell.

Garbled as usual. Making sure Maxwell's equations were valid
was a prime motivator in the 1905 paper. The SR transformations
make sure Maxwell's equations are true universally.

Since a prime result of the work was to show how Maxwell is
correct in all inertial frames, only an illiterate could conclude
that "Einstein does not believe Maxwell".

- Randy

blackboab wrote:

the two postulates of SR

1. That the speed of light is a constant in all reference frames was
actally the work of Maxwell where the quantity c appears as a constant
independent of frame of reference.

2. All inertial reference frames are similar was actually the work of
Galileo.

the gamma correction was the work of Lorentz and Fitgerald

Poincare and Fizeau also added ideas

what EXACTLY did Einstein add ?

what in SR is uniquely Einsteins ?

He derived the laws of electrodynamics cleanly and simply. What is even
more important is that he found a way of making the laws of mechanics
Lorentz Invariant. Even Lorentz did not do that. Most physicists would
have tortured electrodynamics into a Newtonian form. Einstein modified
Newtonian mechanics to be congruent with Maxwell's equations which are
Lorentz Invariant right out of the box. Speaking of boxes, Einstein
worked clean outside the box. Even the brilliant Lorentz, whom Einstein
loved as an intellectual father, hobbled himself with aether.

And that was just one of the things he did in 1905. He also extended
Planck's quantum to electromagnetic radiant energy and derived Planck's
Law clearn. He derived Avagadro's number and showed that molecules and
atoms are really real. His paper on the Brownian Motion is one of the
most referenced papers in the history of physics. All in a single year.
And that was just a warm up.

Bob Kolker


Bob Kolker