In article , "Bill Hobba" writes:

"Alex Green" wrote in message
om...
The current foundations of physics are relativity and quantum theory.
Relativity theory is very badly taught.

Depends on the source. I think the pesentation by Rindler in Introducution
to Special Relativity is quite good.

There are two ways of
presenting it, in the first the assumptions for SR a

1. the speed of light is a constant for all observers
2. the laws of physics are the same for all observers (includes all
motion is relative).
3. the universe is homogenous and isotropic

In the second, modern approach, the assumptions a

1. The universe has a metric ds^2 = dx^2 + dy^2 + dz^2 - c^2dt^2
2. Any coordinate displacement (delta Y) in one coordinate system can
be expressed as a sum of terms of differentials of the coordinates in
another coordinate system.
3. Noether's theorem applies and ds^2 is invariant.

The second approach is better but requires greater knowledge of physics and
math meaning you can not understand it until say at least 3rd year uni.
Also it is reasonable to present an argument why 1 holds and to emphasize it
is really based on the symmetry properties of an inertial frame and to
de-emphasize the importance of c being the speed of light.


Exactly. (1) should say "There exists a finite maximal speed". Or
"finite invariant speed". The association with light is a matter of
historical coincidence, not inherent in the theory.

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

"Androcles" wrote in message ...
"Alex Green" wrote in message
m...
|
| In the second, modern approach, the assumptions a
|
| 1. The universe has a metric ds^2 = dx^2 + dy^2 + dz^2 - c^2dt^2

So why teach an assumption?

All descriptions are encodings of states. What we do in mathematical
physics is take a very simple state, encode it, and see how far that
encoding can be transformed by maths to explain complex states.

Teaching assumptions is VERY poor science.

All science is based upon the premise that certain simple states exist
and can be used to explain more complex entities. Modern biology is
becoming increasingly the study of how the genome creates the
organism. Chemistry is based on QM. Physics postulates that events
exist in a manifold that can be described by equations as simple as
(1) and this can be used to describe a host of physical observations.
Teaching the fact that science is based on certain mathematical axioms
or physical assumptions is healthy because it shows the student the
nature of scientific description. Axioms are physical assumptions
until they have withstood rigorous scientific testing.

Nor is that assumption a
postulate of relativity. It is a result. Do you have the slightest idea what
is meant by "circularity"?


The invariance of the space-time interval is not a result, it is part
of the assumption that space-time exists and is symmetrical wrt
translations and rotations.


| 2. Any coordinate displacement (delta Y) in one coordinate system can
| be expressed as a sum of terms of differentials of the coordinates in
| another coordinate system.
| 3. Noether's theorem applies and ds^2 is invariant.
|
| See http://pancake.uchicago.edu/~carroll/notes/
|
| The first approach is not inconsistent with the second, it just has
| sweeping assumptions that unnerve the novice (ie: the novice thinks
| 'why should the speed of light be constant, what is so special about
| light?' and misses the whole point of relativity).

Oh? and what IS the whole point of relativity?
Why should the speed of light be constant, what is so special about
light?'


The speed of light is the conversion factor from seconds to metres if
the assumption of your physical theory is that the universe is a
(3+1)D manifold. It is not about light, it is about the original
assumption. All observers will observe the same velocity for a motion
that is described by:

0 = dx^2 + dy^2 + dz^2 - c^2dt^2

ie:
dr^2 = dx^2 + dy^2 + dz^2

0 = r^2 - c^2dt^2

which occurs when dr = cdt which happens only when v=dr/dt=c. Contrast
this with the wide range of velocities that can give rise to a
non-zero space-time interval.


| The second
| approach needs a lot of study but has simpler assumptions.

So why teach an assumption?
Teaching assumptions is VERY poor science. Do you have the slightest idea
what is meant by "circularity"?

Simple assumptions or 'axioms' are the basis of all science and maths.
They describe the simplest initial state that mathematical reasoning
can use to describe the physical world. Teaching that we choose a set
of assumptions as the basis for physical theory is very good science.
Different theories have different 'assumptions' and it is not until
they have resisted being invalidated for a long period that they
deserve the title 'axioms' (ie: self evident rather than simply
assumed).

Relativity undoubtedly has a very small set of axioms (assumptions to
those who disagree with relativity). Newtonian/Galilean physics has a
relatively large set of axioms/assumptions which Androcles may
itemise.

Best Wishes

Alex Green

"Alex Green" wrote in message
m...
| "Androcles" wrote in message
...
| "Alex Green" wrote in message
| m...
| |




| | In the second, modern approach, the assumptions a


You've snipped without responding or even having the grace to say so.
I take that to mean you agree with my points, or you would have
answered them.

I shall now return you the same courtesy.
Androcles.

In article ,
Alex Green wrote:

Now, attacking relativity because you don't like the twin paradox or
time dilation or can't see why the speed of light is constant is where
lack of humility comes in. Nobel prize winning physicists are the
intellectual equivalent of olympic gold medallists but much more
selected. Even your university physics/maths professor is a regional
champ. If you believe that all of these people could have considered
time dilation and the twin paradox over a whole century and all got it
wrong then humility should suggest to you that the fault could be with
yourself.

This is the "Why is everybody stupid except for me?" approach. And the
examiner seems to inevitably turn to character flaws in the scientific
community: brainwashing, peer pressure, fear, etc. It can't possibly be
the case that the scientific community knows something about science that
an amateur barely schooled in high school algebra doesn't.


So how can we be sceptical about a century old theory such as
relativity?

Any new, replacement theory must contain most of the results of the
old theory because Relativity predicts a host of phenomena from black
holes to quantum physics that have been discovered. Sorry, but if
your new replacement for relativity does not contain most of the
tensor maths of the current theory then you must be wrong. So
sceptics, off you go to uni for a 3 year course on advanced maths.

It's not such a strong requirement as that. It just has to fit inside the
error bars. When we get to things like black holes, the data still leave
a lot of room to move around in.


Alternatively you might replace the original assumptions in some way
so that relativity is a special case. I have been trying to do this
with the metric tensor but sci.physics.research will not post these
musings for a good reason: without strong predictions for experiment
and a clearly argued case the ideas are unduly speculative.

Relativity itself was speculative until some new data started coming in.
Speculative can lead to great new insights, there's nothing inherently
wrong with speculative. But sci.physics.research moderators do often use
the "speculative" label as a polite way of saying "It's complete crap."


One method of criticising Relativity that is absurd is to go back to
Einstein's century old papers and nit pick every problematic phrase.
This is as crazy as maintaining that science is 'wrong' because Roger
Bacon was not always consistent. Relativity theory is the product of a
million or more papers over the past century, it is not contained in a
single publication a century ago.

This is usually done with the original Michelson-Morley experiment, I
believe. Similar experiments have been conducted ever since, up to the
present day, but some people seem not to suspect that.

Popperism aside, a scientific theory doesn't stand or fall by a single
experiment, or by the original experiment. It stands by the
interpretation of large sets of experiments, preferably widely different
experiments that explore widely different regimes of parameter space.

So some Russian team finds a neutron lifetime with error bars under one
second, but something like six sigma away from the world average. It
can't hit the standard model unless there's a good reason to think they're
right and everyone else is wrong. But the aggregate of beam measurements
and bottle measurements have been converging on a value that's not that.
Play the odds, and beware of naive Popperisms.

Sci.physics is a good place for punting odd ideas around but if we are
sceptical of current theory we should also be sceptical of our own
theories, especially if no one but ourselves accepts them.

A lot of criticism seen here is mean-spirited and unjustified. On the
other hand, I've seen some lengthy and in-depth discussions of matters of
physics, some careful and detailed criticisms of speculative theories,
that could have been profitable. You'll never find more or higher
quality information on Usenet than when people are trying to prove you
wrong, but that opportunity will be completely lost on the crackpot.

Heck, sometimes when I have a question, I wish I could discuss it in a
convincingly crackpot manner that irks people just enough to keep trying
to correct me, but not enough to drive them off. But it's so hard to do
that on purpose.


--
"Suppose you were an idiot... And suppose you were a member of
Congress... But I repeat myself." - Mark Twain

(Alex Green) wrote in message om...
The current foundations of physics are relativity and quantum theory.

Disagreed.

Relativity theory is very badly taught.

Agreed.

There are two ways of
presenting it, in the first the assumptions for SR a

One of the things that is "very badly taught" is the exact mistake
that you make right he there are no "assumptions for SR", at least
not in the way in which you are using the word "assumption" here; a
word which has a rather limited, specialized and well-understood
meaning in math:

http://penguin.servehttp.com/sven/ph...32da96a7d1.pdf



cordially


Y.T.

--
Remove YourClothes before you email me.

"Androcles" wrote in message ...

"Alex Green" wrote in message
m...
| "Androcles" wrote in message
...
| "Alex Green" wrote in message
| m...
| |




| | In the second, modern approach, the assumptions a


You've snipped without responding or even having the grace to say so.
I take that to mean you agree with my points, or you would have
answered them.

I shall now return you the same courtesy.
Androcles.

So much for those Best Wishes, Alex.
Welcome to Androcles' Kingdumb.

Dirk Vdm

(Y. T.) wrote in message . com...
(Alex Green) wrote in message om...
The current foundations of physics are relativity and quantum theory.

Disagreed.

Why, what else would you include?

Relativity theory is very badly taught.

Agreed.

Does that mean you had difficulty learning it?
No offense, but I doubt relativity can be taught
only learned, as it's a work in progress.

There are two ways of
presenting it, in the first the assumptions for SR a

One of the things that is "very badly taught" is the exact mistake
that you make right he there are no "assumptions for SR", at least
not in the way in which you are using the word "assumption" here; a
word which has a rather limited, specialized and well-understood
meaning in math:
http://penguin.servehttp.com/sven/ph...32da96a7d1.pdf

Yes, the word postulate might be better, but "assumption"
is not a "mistake".

cordially
Y.T.

Same
Ken S. Tucker

(Y. T.) wrote in message . com...
(Alex Green) wrote in message om...
The current foundations of physics are relativity and quantum theory.

Disagreed.

Relativity theory is very badly taught.

Agreed.

There are two ways of
presenting it, in the first the assumptions for SR a

One of the things that is "very badly taught" is the exact mistake
that you make right he there are no "assumptions for SR", at least
not in the way in which you are using the word "assumption" here; a
word which has a rather limited, specialized and well-understood
meaning in math:

http://penguin.servehttp.com/sven/ph...32da96a7d1.pdf


The gene was a postulate for decades until chromosomes were
discovered, validating the postulate.

In the paper it says:
"In math, however, postulating something doesn't
mean to hold that thing true - merely to treat it as if
it were true for the purpose of a given mathematical operation."

This is also the way a scientist such as Einstein began in Relativity
theory. He suggested that a set of things might be observed and urged
scientists to test them. It was only when they survived the tests that
they became part of accepted scientific theory. After a hundred years
of Relativity Theory we can now say that the universe has the
properties of a (3+1)D manifold. The initial assumptions /
propositions / postulates of the theory have been 'validated'.
However, in principle, scientists do not maintain that things are
'true' because the history of science shows clearly that one
generation's truth is another generation's special case. This is why
scientists refer to their knowledge as 'scientific theory'. Scientific
theory is an ever more accurate approximation to the rules existing in
the world revealed by measurement and observation.

Teaching the fact that science is based on certain physical
assumptions that are tested by experiment is healthy because it shows
the student the nature of scientific description. It also emphasises
where the weak points lie in existing theory.


Best Wishes

Alex Green
1

"Alex Green" wrote in message m...

Scientific
theory is an ever more accurate approximation to the rules existing in
the world revealed by measurement and observation.

It is an unwarranted assumption on your part that there are rules
existing in the world.

Martin Hogbin

wrote in message ...
In article , Uncle Al writes:
Alex Green wrote:

The current foundations of physics are relativity and quantum theory.
Relativity theory is very badly taught. There are two ways of
presenting it, in the first the assumptions for SR a
[snip crap]

Idiot.

Unc, you appear to have a problem with reading lately.

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

What's so lately about it?

Patrick