Re: Help with Special Relativity simultaneous events

On Dec 24, 6:59 pm, "Androcles" <Headmas...@xxxxxxxxxxxxxxxx> wrote:
<specialrelativity...@xxxxxxxxx> wrote:
<< My grasp of special relativity is somewhat limited. I am having
trouble with simultaneous events and the separation formulas. Here is
the type of problem which causes some of my confusion in understanding
Einstein's concepts. I would appreciate it if someone could add their
insight.

< Ok, I'll add all the insight you need. Whether you understand it or
not is up to you.
Einstein had three postulates.
1) Galilean relativity. Einstein called it the
"Principle of Relativity".
If you don't know what that is then you have no hope.
2) Light is always propagated in empty space
with a definite velocity c which is dependent
on the state of motion of the absorbing body.
3) the 'time' required by light to travel from A
to B equals the 'time' it requires to travel
from B to A.
1) is correct.
2) is wrong.
3) is just plain silly.
Now learn special mathematics 001. >

Einstein had four postulates. The first two, which Andy
misrepresented, are well known as postulates. The third, which Andy
wrote accurately, is a definition of how clocks should be set. As
such, it IS a postulate, and Andy is to be commended for realizing
that.
Here are the four postulates:-
1) The conjecture, which he called the "Principle
of Relativity", "that the same laws of
electrodynamics and optics will be valid for
all frames of reference for which the
equations of mechanics hold good."
2) Light is always propagated in empty space
with a definite velocity c which is
independent on the state of motion of the
emitting body.
3) That clocks are to be set so that "the 'time'
required by light to travel from A to B equals
the 'time' it requires to travel from B to A".
4) The rate at which clocks beat are to be set
so that they measure the average speed of
light - during a round-trip from A to B and
back to A - as c.

Andy said, "1) is correct. 2) is wrong. 3) is just plain silly."
I say,
1) is a matter of choice. In Classical Physics, it is false. It is
only true IF we accept all the next postulates, and switch to non-
Galilean relativity.
2) is a postulate. Since a postulate is a statement to be accepted as
true without proof, it cannot be "false" even if it contradicted
reality.
3) This method of setting clocks is essential to the operation of the
relativistic transformation equations, thus has to be allowed, even
though clocks so set ("esynched") are NOT synchronous.
4) Although this postulate requires that clocks of a given system
must run at a different rate than those of differently moving systems,
it too must be allowed in order for the first two to hold good.

Although Einstein missed it, there is a fifth postulate required and
imposed by the relativistic equations:
5) Lengths in a system moving at v have to change so that those in
the direction of motion are (c^2-v^2)^2 shorter than those in the
perpendicular directions.
Because Einstein omitted an essential symbol from his derivational
equations, physicists never recognized this postulate, thinking
instead that all such changes are consequences of using esynched
clocks to measure the length of a moving rod.

glird
.

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