Did SR invent the concept of 'frame of reference'?

First, what is a "frame of reference"? A "frame of reference" is an
aggregation of matter (usually nearly "rigid" in the Euclidean sense,
in which spacio-temporal measurements can be accurately made according
to some operational procedure. The spacial, or distance, measurements
can be done by scratching equally spaced marks in the floor and walls
of the frame to aid in making measurements of visible things which are
at certain points in the frame at certain times, according to a
conveniently place set of synchronized clocks.

So, did SR (or rather Einstein) invent the concept of "frame of
reference"? I say no. I say that it was invented at least by Galileo,
who was one of the first to make kinematics a science, and that
requires a frame of reference for making space and time measurements
within. However, the frame concept goes back in Western culture at
least to Aristotle. Aristotle believe that all motion originated in
the actions of some Prime Mover, who/which sat at rest in some
absolute rest frame, say the earth frame. We can think of this as the
Prime Inertial Frame. One reason it is right to continue to think of
relativity as "relativistic," in spite of arguments to drop the
relativity connotation in favor of some notion of group theoretic
invariance, is because of the following: Of all the infinite number of
inertial frames in SR or Newtonian mechanics, no one of them is
preferred in any way for the invention of the laws of physics, unlike
the case of LET, which has a single frame in which Maxwell's equations
are truly satisfied. Now, it makes no sense to talk about the motion
of the Prime Inertial Frame with respect to any piece of matter, just
as it makes no sense to talk about the motion of the luminiferous
ether with respect to ordinary matter. But in relativity, there's a
perfect symmetry between any two inertial frames. Any frame can be
said to be either "at rest" or in motion with respect to some other
frame. In non-relativistic theories it never makes sense to talk about
the non-rest motion of an Absolute Rest Frame.




Now, let's go over Galileo's notion of the principle of relativity.
Galileo defended the view that the earth spins around its north
pointing axis and revolves around the sun (Copernican view), contrary
to the opinion of Aristotle, Ptolemy, and many of Galileo's peers, in
his book Dialogue Concerning the Two Chief World Systems. He confronts
the fixed earth view with a made-up dialog among three imaginary
persons: Salvatori (who represents to Copernican viewpoint), Sagredo
(a foil for Salvatori), and Simplicio (who defends the Ptolemaic
theory). I'm using the English translation of the book by Stillman
Drake, University Calif. Press, 1953. The book is laid out proceeding
by days.


First we have Galileo on setting up a frame of reference concept to
make distance measurements (pp. 12-13) from the First Day:

**** begin quote (p. 13) ***

SALV. Your choice and the reason you adduce for it seem to me most
excellent. So now we have it that the first dimension is determined by
a straight line; the second (namely, breadth) by another straight
line, and not only straight, but at right angles to that which
determines the length. Thus we have defined the two dimensions of a
surface; that is, length and breadth.

But suppose you had to determine a height -- for example, how high
this platform is from the pavement down below there. Seeing that from
any point in the platform we may draw infinite lines, curved or
straight, and all of different lengths, to the infinite points of the
pavement below, which of all these lines would you make use of?

SAGR. I would fasten a string to the platform and, by hanging a
plummet from it, would let it freely stretch till it reached very near
to the pavement; the length of such a string being the straightest and
shortest of all lines that could possibly be drawn from the same point
to the pavement, I would say that it was the true height in this case.

**** end quote ***

Next we go the Galilean Principle of Relativity, which can be stated
in the following form: It is impossible to perform any "mechanical"
experiment within a frame of reference that can distinguish the
frame's motion as either "at rest" or inertial. The inclusion of the
behavior of animals in Galileo's thought experiment goes outside the
realm of pure mechanics, yet is still not dealing with optics per se.
In it you will read of suggested measurements that require the
rigidity of a Euclidean frame. The argument (in the form of thought
experiments) is divided into two parts: First, how the behavior of
these animals and mechanical devices are manifested while the ship is
at rest ("standing still"), and second, how the behavior of these
thing is identical relative to the frame of the ship if the ship is in
inertial motion. The conclusion is that the inertial motion is not a
means to affect the behavior of these test subjects, and thus by
reversing the argument, the inertial motion of the ship cannot be
inferred from the behavior of these test subjects. But all of this
requires making measurements within an inertial frame.

Dialogue Concerning the Two Chief World Systems - from The Second Day
pp. 186--188

**** begin quote ***

[SALV.] Shut yourself up with some friend in the main cabin below
decks of some large ship, and have with you there some flies,
butterflies, and other small flying animals. Have a large bowl of
water with some fish in it; hang up a bottle that empties drop by drop
into a wide vessel beneath it. With the ship standing still, observe
carefully how the little animals fly with equal speed to all sides of
the cabin. The fish swim indifferently in all directions; the drops
fall into the vessel beneath; and, in throwing something to your
friend, you need throw it no more strongly in one direction than in
another, the distances being equal; jumping with your feet together,
you pass equal spaces in every direction. When you have observed all
these things carefully (though there is no doubt that when the ship is
standing still everything must happen in this way), have the ship
proceed with any speed you like, so long as the motion is uniform and
not fluctuating this way and that. You will discover not the least
change in all the effects named, nor could you tell from any of them
whether the ship was moving or standing still. In jumping, you will
pass on the floor the same spaces as before, nor will you larger jumps
towards the stern than toward the prow even though the ship is moving
quite rapidly, despite that fact that during the time that you are in
the air the floor under you will be going in a direction opposite to
your jump. In throwing something to your companion, you will need no
more force to get it to him whether he is in the direction of the bow
or the stern, with yourself situated opposite. The droplets will fall
as before into the vessel beneath without dropping toward the stern,
although while the drops are in the air the ship runs many spans. The
fish in their water will swim toward the front of their bowl with no
more effort than toward the back, and will go with equal ease to bait
placed anywhere around the edges of the bowl. Finally the butterflies
and flies will continue their flights indifferently toward every side,
nor will it ever happen that they are concentrated toward the stern,
as if tired out from keeping with the course of the ship from which
they will have been separated during long intervals by keeping
themselves in the air. And if smoke is made by burning some incense,
it will be seen going up in the form of a little cloud, remaining
still and moving no more toward one side than the other. The cause of
all these correspondences of these effects is the fact that the ship's
motion is common to all the thing contained in it, and to the air
also. That is why I say you should be below decks; for if this took
place in the open air, which would not follow the course of the ship,
more or less noticeable differences would be seen in some of these
effects noted. No doubt the smoke would fall as much behind us as the
air itself. The flies likewise, and the butterflies, held back by the
air, would be unable to follow the ship's motion if they were
separated from it by a perceptible distance. By keeping themselves
near it, they would follow it without effort or hindrance; for the
ship, being an unbroken structure, carries with it a part of the
nearby air. For similar reason we sometimes, when riding horseback,
see persistent flies and horseflies following our horses, flying now
to one part of their bodies and now to another. But the difference
would be small as regards the following drops, as to the jumping and
the throwing it would be quite imperceptible.

[SAGR.] Although it did not occur to me to put these observations to
the test when I was voyaging, I am sure that they would take place in
the way you describe. In confirmation of this I remember having often
found myself in my cabin wondering whether the ship was moving or
standing still; and sometimes at a whim I have supposed it going one
way when its motion was the opposite. Still, I am satisfied so far,
and convinced of the worthlessness of all experiments brought forth to
prove the negative rather than the affirmative side as to the rotation
of the earth.

**** end quote ***

As an end note to the above, I cannot help but imagine a young
Einstein reading Galileo's description of the ship in its two states
of motion and imagining the effect of making experiments of the
propagation of light within the "frame" in its two states of motion
and then concluding that all would have to proceed identically,
independent of the state of motion of the frame so long as that motion
is inertial (note his distinction between "constructive" and
"principle" approaches to the problem).

By and by I despaired of the possibility of discovering
the true laws by means of constructive efforts based on
known facts. The longer and the more despairingly I tried,
the more I came to the conviction that only the discovery
of a universal formal principle would lead us to assured
results. The example I saw before me was thermodynamics.
The general principle there was given in the theorem: the
laws of nature are such that it is impossible to construct
a perpetuum mobile (of the first or second kind). How,
then, could such a universal principle be found? After ten
years of reflection such a principle resulted from a paradox
upon which I had already hit at age sixteen: If I pursue
a beam of light with the velocity c (velocity of light in
a vacuum), I should observe such a beam of light as a
spatially oscillatory electromagnetic field at rest. However,
there seems to be no such thing, whether on the basis of
experience or according to Maxwell's equations. From the
very beginning it appeared to me intuitively clear that,
judged from the standpoint of such an observer, everything
would have to happen according to the same laws as for an
observer who, relative to the earth, was at rest. For how,
otherwise, should the first observer know, i.e., be able to
determine, that he is in a state of fast uniform motion?
One sees that in this paradox the germ of the special
relativity theory is already contained. ...

--- Einstein, Autobiographical Notes, Albert Einstein:
Philosopher-Scientist, Volume One, p. 53, Open Court Classics.


I regard Einstein's intuition back then based on his thought
experiment as merely telling him the same thing that Galileo concluded
from his thought experiment about mechanics alone, only this time
including optics as well. It was a bold hypothesis for the time, given
that it flew in the face of the ether theory of light propagation, the
MMX notwithstanding (1887), the sixteen-year old Einstein (1895)
perhaps not even being aware of it at the time. But given that
Einstein was a believer in his Principle of the Harmony of Nature, how
could he have concluded otherwise? When Einstein said "everything
would have to happen according to the same laws," he meant everything
-- everything measurable that is.

Patrick

"Patrick Reany" wrote in message om...
Did SR invent the concept of 'frame of reference'?

[snip - merely quickly browsed, not enough time, sorry]

Patrick, I don't know if you have read Robert Geroch's
"General Relativity fom A to B". If not, I'm sure you will
find it to give a fascinating view on this subject. Geroch
gives a brilliantly clear and detailed account of the three
distinct views of Aristotle, Galileo and Relativity on one
and the same shared space-time.
If you haven't read this, you really should check it out!
Enjoy...

Dirk Vdm

Patrick Reany wrote in message
om...
Did SR invent the concept of 'frame of reference'?

First, what is a "frame of reference"? A "frame of reference" is an
aggregation of matter (usually nearly "rigid" in the Euclidean sense,
in which spacio-temporal measurements can be accurately made according
to some operational procedure. The spacial, or distance, measurements
can be done by scratching equally spaced marks in the floor and walls
of the frame to aid in making measurements of visible things which are
at certain points in the frame at certain times, according to a
conveniently place set of synchronized clocks.

So, did SR (or rather Einstein) invent the concept of "frame of
reference"? I say no.


{snip the rest of the irrelevant attempt at philosophy.}

That should be simple to decide. Simply find a reference where the words
"frame of reference", or even "frame" are used prior to 1905. Your own,
personal redefinitions and "imaginations" of historical documents are
irrelevant.

--
greywolf42
ubi dubium ibi libertas
{remove planet for return e-mail}

(Patrick Reany) wrote in message . com...
Did SR invent the concept of 'frame of reference'?

What difference does it make if the idea was introduced
with SR? It's more general than that and makes perfectly
good sense in Galilean relativity too.

First, what is a "frame of reference"? A "frame of reference" is an
aggregation of matter

Oops.

(usually nearly "rigid" in the Euclidean sense,

Oops.

Nope. A frame of reference is a coordinate system.

[Remaining silliness snipped]

- Randy

(Randy Poe) wrote in message . com...
(Patrick Reany) wrote in message . com...
Did SR invent the concept of 'frame of reference'?

What difference does it make if the idea was introduced
with SR? It's more general than that and makes perfectly
good sense in Galilean relativity too.

First, what is a "frame of reference"? A "frame of reference" is an
aggregation of matter

Oops.

(usually nearly "rigid" in the Euclidean sense,

Oops.

Nope. A frame of reference is a coordinate system.

You're claiming that a frame of reference of not a piece of matter?
Are there any physicists here that agree with Randy on this? Randy,
what are your references for this claim of yours? I'm interested.


[Remaining silliness snipped]

- Randy

No. A coordinate system may or may not be associated with a reference
frame (a piece of matter used to assign spacio-temporal coordinates of
events). If it is then they are "essentially" the same thing, if they
aren't then it is a pure mathematical abstraction. A coordinate system
may be an abstraction, but a reference frame never is. If you're a
physicist, you should know better. Still, considering how badly
physics education ever defines ANYTHING, it's no wonder.

Think of it this way: A pure mathematician can get by with a
coordinate system, but an experimental physicist requires a frame of
reference to make real measurments within.

Einstein often used the term "a coordinate system" to refer to a
reference frame. I don't see that he ever distinguished them. I do
distinguish them, though, for the obvious reasons I stated above. I
give examples below:

What has nature to do with our coordinate systems and
their state of motion? If it is necessary for the purpose of
describing nature, to make use of a coordinate system
arbitrarily introduced by us, then the choice of its state
of motion ought to be subject to no restriction; the laws
ought to be entirely independent of this choice (general
principle of relativity)." (First printed in 1919. Appeared
in Albert Einstein's General Relativity, Crown Publication,
New York, 1979, p63.)

Could we BUILD a relativistic physics valid in all CS
[coordinate system/s]; a physics in which there would be
no place for ABSOLUTE, but only for relative motion?
This is indeed possible!
We have at least one indication, though a very weak
one, of how to BUILD the NEW PHYSICS. Really
relativistic physics must apply to all CS and, therefore, also
to the special case of the inertial CS. The new GENERAL
LAWS valid for all CS must, in the special case of the
inertial system, reduce to the old, known laws.
The problem of formulating physical laws for every
CS was solved by the so-called general relativity theory;
the previous theory, applying only to inertial systems, is
called the special relativity theory. The two theories cannot,
of course, contradict each other, since we must always
include the old laws of the special relativity theory in the
general laws for an inertial system. But just as the inertial
CS was previously the only one for which physical
laws were formulated, so now it will form the special
limiting case, as all CS moving arbitrarily, relative to each
other, are permissible.
This is the PROGRAM for the general theory of relativity.
[Found in: Evolution of Physics, p. 212-213, emphasis mine.]

You do not describe nature using pure abstract coordinate systems --
you use matter frames from which measurements are taken.

In the following quote we see how Einstein uses the two expressions
interchangeably, compared to how he use CS above:

The special theory of relativity is an adaptation of
physical principles to Maxwell-Lorentz electrodynamics.
From earlier physics it takes the assumption that Euclidean
geometry is valid for the laws governing the position of
rigid bodies, the inertial frame, and the law of inertia.
The postulate of equivalence of inertial frames for the
formulation of the laws of Nature is assumed to be valid
for the whole of physics (special relativity principle).
From Maxwell-Lorentz electrodynamics it takes the postulate
of invariance of the velocity of light in a vacuum
(light principle).

Found in: "Fundamental ideas and problems of the theory of
relativity," in Gerald Tauber's Albert Einstein's Theory of
General Relativity, Crown Publ., 1979, p. 53.

Clearly, to Einstein a frame of reference is a piece of matter, which
he sometimes refers to as a "coordinate system."

Patrick

"Dirk Van de moortel" wrote in message ...
"Patrick Reany" wrote in message om...
Did SR invent the concept of 'frame of reference'?

[snip - merely quickly browsed, not enough time, sorry]

Patrick, I don't know if you have read Robert Geroch's
"General Relativity fom A to B". If not, I'm sure you will
find it to give a fascinating view on this subject. Geroch
gives a brilliantly clear and detailed account of the three
distinct views of Aristotle, Galileo and Relativity on one
and the same shared space-time.
If you haven't read this, you really should check it out!
Enjoy...

Dirk Vdm

Thanks for the tip, Dirk. I did check it out. It is a very good
presentation of the fundamentals of GR. However, I find Geroch's use
of the Aristotelian viewpoint somewhat weaker than I used. Seems that
Geroch could have gotten by with a Cartesian viewpoint for the
pre-Galilean viewpoint to make his points. I'll keep reading the book
and make some posts giving Geroch's viewpoint. He make's some very
good philosophical statements on the limitations of physics, which,
when I present them, I will no doubt be derided for.

I can sympathize with Geroch's decision to choose Aristotle rather
than Descartes, a contemporary of Galileo, to represent the naive
viewpoint for starting physics. The only problem with this choice is
that it's pretty hard to think of Aristotle as introducing a
coordinate system over this prime frame of his. I can't think of
anyone living between Aristotle and Descartes that could be used.

Anyway, I'll characterize Geroch's Aristotelian viewpoint as this:
there is nothing more one needs to fully characterize events in space
and time than a single frame of reference. I'll characterize Geroch's
Galilean viewpoint as this: there is something to be gained in the
characterization of events in space and time by employing multiple
frames of reference, and we need to agree on some standards of event
comparison between reference frames. Such a viewpoint suggests the
notion of the "universal quantity" (or more subtly a "universal
quality") that comes from the multi-frame perpective that is lacking
in the Aristotelian viewpoint. What do you think of my
characterizations? I'm trying to anticipate Geroch, since I have not
read more than the first page of his Galilean viewpoint chapter.
Afterall, we know that the PoR is used as a heuristic in the
formulation of the laws of physics post Newton, though I don't know
that Newton ever used it that way.

My biggest gripe is that Geroch's approach to teaching GR is so good
it should be considered by the Establishment as THE approach that all
physics students should get as their standard introduction to
Newtonian mechanics, and not just reserve it for GR classes. It's a
little slower intro, but it's so much clearer about what physics is
really all about (because physics is about laws, it's also about
events and reference frames). One reason there are so many cranks in
the world is because they come out of their physics classes holding to
the Aristotelian viewpoint, in spite of their education! It must be
that their education did not specifically address this prevalent
misconception about the nature of physics. Misconceptions have to be
directly confronted to be removed.

Patrick

"Patrick Reany" wrote in message om...
"Dirk Van de moortel" wrote in message
...
"Patrick Reany" wrote in message om...
Did SR invent the concept of 'frame of reference'?

[snip - merely quickly browsed, not enough time, sorry]

Patrick, I don't know if you have read Robert Geroch's
"General Relativity fom A to B". If not, I'm sure you will
find it to give a fascinating view on this subject. Geroch
gives a brilliantly clear and detailed account of the three
distinct views of Aristotle, Galileo and Relativity on one
and the same shared space-time.
If you haven't read this, you really should check it out!
Enjoy...

Dirk Vdm

Thanks for the tip, Dirk. I did check it out. It is a very good
presentation of the fundamentals of GR. However, I find Geroch's use
of the Aristotelian viewpoint somewhat weaker than I used. Seems that
Geroch could have gotten by with a Cartesian viewpoint for the
pre-Galilean viewpoint to make his points. I'll keep reading the book
and make some posts giving Geroch's viewpoint. He make's some very
good philosophical statements on the limitations of physics, which,
when I present them, I will no doubt be derided for.

I can sympathize with Geroch's decision to choose Aristotle rather
than Descartes, a contemporary of Galileo, to represent the naive
viewpoint for starting physics. The only problem with this choice is
that it's pretty hard to think of Aristotle as introducing a
coordinate system over this prime frame of his. I can't think of
anyone living between Aristotle and Descartes that could be used.

Anyway, I'll characterize Geroch's Aristotelian viewpoint as this:
there is nothing more one needs to fully characterize events in space
and time than a single frame of reference. I'll characterize Geroch's
Galilean viewpoint as this: there is something to be gained in the
characterization of events in space and time by employing multiple
frames of reference, and we need to agree on some standards of event
comparison between reference frames. Such a viewpoint suggests the
notion of the "universal quantity" (or more subtly a "universal
quality") that comes from the multi-frame perpective that is lacking
in the Aristotelian viewpoint. What do you think of my
characterizations? I'm trying to anticipate Geroch, since I have not
read more than the first page of his Galilean viewpoint chapter.

You haven't got very far then. Ah, lucky you. But
fear not, on second and third reading it gets even
better :-)
I think you'll soon see why he takes Aristotle rather
than Descartes. An obvious reason seems to me that,
independently of Descartes' philosophy (or what I
remember of it from a [too] long time ago), his name
is far too firmly linked with the concept of 'Cartesian
coordinates' and thus with 'coordinate transformations',
of which the Galilean transformation is perhaps the
most obvious in a physics context, whereas Aristotle
would have only one absolute viewpoint, and, in the
most rigorous and systematic way, never even develop
the concept of a reference frame to begin with, so to
speak ;-)


Afterall, we know that the PoR is used as a heuristic in the
formulation of the laws of physics post Newton, though I don't know
that Newton ever used it that way.

My biggest gripe is that Geroch's approach to teaching GR is so good
it should be considered by the Establishment as THE approach that all
physics students should get as their standard introduction to
Newtonian mechanics, and not just reserve it for GR classes.

I understand that the book is used in some places as
an introduction to special relativity, and I agree that
that is the best possible choice.

It's a
little slower intro, but it's so much clearer about what physics is
really all about (because physics is about laws, it's also about
events and reference frames). One reason there are so many cranks in
the world is because they come out of their physics classes holding to
the Aristotelian viewpoint, in spite of their education! It must be
that their education did not specifically address this prevalent
misconception about the nature of physics. Misconceptions have to be
directly confronted to be removed.

hm, alas, the direct confrontation does not always
seem to help :-)


Patrick

Dirk Vdm

(Patrick Reany) wrote in message . com...
(Randy Poe) wrote in message . com...
(Patrick Reany) wrote in message . com...
Did SR invent the concept of 'frame of reference'?

What difference does it make if the idea was introduced
with SR? It's more general than that and makes perfectly
good sense in Galilean relativity too.

First, what is a "frame of reference"? A "frame of reference" is an
aggregation of matter

Oops.

(usually nearly "rigid" in the Euclidean sense,

Oops.

Nope. A frame of reference is a coordinate system.

You're claiming that a frame of reference of not a piece of matter?

Yes.

A coordinate system may be fixed relative to some "piece of
matter". But it is not a piece of matter.

I suppose I know what you're thinking in your muddled way.
For instance, I might define the earth-moon-centered frame
of reference. This is a coordinate system which is located
at the center of mass of the earth-moon system.

Now in your murky depths, you're thinking (and probably going
to reply) "aha! it's defined in terms of the earth and moon
and those have mass". That's true. It's defined in terms
of two large massive objects.

But the reference frame doesn't have any mass. What is
its mass?

If you and I are sitting still relative to each other, what
is the mass of our reference frame? Our total mass? But
what if there are other unknown objects in the universe
which share our reference frame, which are at rest relative
to us (for instance, everything on my desk)?

Are there any physicists here that agree with Randy on this? Randy,
what are your references for this claim of yours? I'm interested.

Well, just that I've never heard anybody ascribe a mass
or a kinetic energy or a charge distribution, or a
mass distribution or a dielectric constant or a temperature
or, etc, etc, to a reference frame. And collections of
matter have those properties.

What is your reference for saying a frame of reference has
mass?

- Randy

(Patrick Reany) wrote in message . com...
You're claiming that a frame of reference of not a piece of matter?

If I say "the frame of reference of the earth's surface" (a
rotating frame), what piece of matter is that?

If I say "the frame of reference of the earth's center of
mass" (a non-rotating frame), what piece of matter is that?

For that matter, if I talk about two frames of reference
relative to ME, but rotating at different rates, those
are clearly different frames of reference. What piece
of matter are you associating with each one?

If I say "the frame of the cosmic background", what piece of
matter is that?

- Randy

(Patrick Reany) wrote in message . com...
You're claiming that a frame of reference of not a piece of matter?

If I say "the frame of reference of the earth's surface" (a
rotating frame), what piece of matter is that?

If I say "the frame of reference of the earth's center of
mass" (a non-rotating frame), what piece of matter is that?

For that matter, if I talk about two frames of reference
relative to ME, but rotating at different rates, those
are clearly different frames of reference. What piece
of matter are you associating with each one?

If I say "the frame of the cosmic background", what piece of
matter is that?

- Randy