9·
24· 96 Tuesday; 4:20 pm
Okay
– as we describe it nowadays, an event is not something you (or I) can “move
away from” or “move toward.” Why
not? It happens in YOUR frame of reference. And
same for other relatively-moving observers.
But
is it necessary to think of observing this way?
Can you accelerate and leave your ref. frame stationary? Then you’d imagine light having to catch up
with you – maybe.
I’m
getting sleepy. . .
In the Einstein train-and-lightning thought experiment, the two lightning bolts leave marks on both the platform and railroad car, and it is from these marks that calculations of simultaneity (or not) are made by mid-point observers for both frames. The other observer is always considered to be the one who is moving. Relative simultaneity, relative length and relative time arise as a result of this distinction.
In the Einstein train-and-lightning thought experiment, the two lightning bolts leave marks on both the platform and railroad car, and it is from these marks that calculations of simultaneity (or not) are made by mid-point observers for both frames. The other observer is always considered to be the one who is moving. Relative simultaneity, relative length and relative time arise as a result of this distinction.
9
· 26 · 96 Thurs. 12:45 a.m.
Okay,
I’m awake, with nothin’ to do. I mean,
plenty to do
complex analysis
probs.
thesis work
write a letter or two
but nothing that I’m
compelled to
do.
It does seem like I need to
write something. Maybe just something
connected to physics, maybe something more personal. For lack of other ideas at the moment, I’ll
write about Lorentz contraction and cosmic expansion.
If one accepts redshift
phenomenon as due to cosmic expansion, the very-far-away galaxies are moving
away from any given observer at relativistically significant velocities. So, does Lorentz contraction apply to the
distance scales attached to the galaxies and moving past us (any observer) at
the speed at which the galaxy(ies) is (are) receding?
In other words, taking the Lorentz
contraction seriously (but maybe erroneously?) means the expanding universe
suddenly doesn’t seem so big. It is
contracted by its expansion!
See Steveo Weinberg’s book. If anybody discusses the issue, I would
expect it to be him.
2:30 pm 9/26/96
Begin a novel: Did you happen to
read my previous novel? It seems
improbable since I didn’t write a previous one; thus if you have read it,
please let me know as soon as possible.
(An early morning thought,
expressed in the afternoon, and missing some of the truthful oddness I felt in
it this morning.)
Photo and caption are from Genesis of the Big Bang (2001) by Ralph Alpher & Robert Herman.
9 · 28 · 96 Saturday 1:40 pm I should do a search for different ideas in
the literature about what the Lorentz contraction actually means.
In the meantime though,
I just opened Cosmological Constants
and started reading Alpher & Herman’s paper (p. 117) which mentions in its
abstract determining “the time dependence of proper distance.”
So I’ll read that first
and get back with y’all later about the Lorentz contraction thing. (I’m in the back room at 4111 Avenue F, where
most of my books are.) This is just a
note (at this point) to add: ylem! I’d heard of it in some Gamow book, but
never have seen it in a research publication until now, in the Alpher &
Herman paper “Remarks on the Evolution of the Expanding Universe”: "According to this theory the ylem (the
primordial substance from which the elements were formed) consists of neutrons
at a high density and temperature."
Ylem – what the universe
(and people) are made of; the matter that shrunk into little black holes
(electrons). What about protons (and
neutrons, as particles)?
10/8/96: If YLEM
is high-density high-temp neutrons, it sounds much like a neutron star. Which has neutrons as closely packed as they can get, doesn’t it? (Later.)
It’s 4:30 p.m., a Tuesday (Belgium) at 603 Blanco San Marcos Texas USA,
Earth (where?), “Sun” solar system, Galaxie 500 or Milky Way or whatever. Somewhere in space! HERE.
Somewhere in time! But who
believes in time anyway? It’s an
organizing principle for events. One
could choose to be disorganized and not assign times to events. Or not assign events to times. Is there really a history of the
universe? Sure – we created it. Could we choose disorganization over
organization in describing the universe?
Cause and effect don’t seem to allow that.
Anyway, I’m 42 years old. I
should get to work. I haven’t done that
except in a need-for-money fashion, part-time for the most part. It seems to me I have a resistance to
becoming an authority, among other things.
But if one keeps doing something, like physics in my case, becoming an
authority is inevitable. What I’ve
always been mainly interested in is asking questions about things. Becoming an authority is to give in to a mild
form of brainwashing. But it’s still
possible to raise questions, provided seeds were planted at some time in the
past, possibly. Maybe – most of the time
it seems now that I think about it – questions seem to pop out of nowhere.
My question posed in this journal
on p. 135 (9· 26· 96) seems to be answered by the concept of “cosmic
time.” There must be a lack of
synchronization of clocks between two relatively moving observers in order for
length contraction to exist (if we accept that idea, rather than the idea that
it’s impossible to do a length measurement of a moving rod, which I call the
Einstein length measurement problem).
As M.S. Longair writes in Theoretical
Concepts in Physics, p. 317, “We now introduce a set of fundamental
observers, defined as observers who move in such a way that the Universe
appears to be isotropic to them. Each of
them has a clock and proper time measured by that clock is called cosmic time. There are no problems of synchronisation of
these clocks carried by fundamental observers because, for example, they could
be told to set their clocks to the same time when the Universe has a certain
density.”
But it sounds like too much of an idealization. Who will tell them to set their clocks? God?
Even if a clock is automatically set at a certain density, that means
density measures time. But I’ll accept
that idea of cosmic time, for the time being.
10/9/96 8:50
pm However, the renowned Hermann Bondi,
MA, FRS, in Cosmology p. 125, says,
when discussing Milne’s kinematic relativity,
In general relativity, the equivalence of the laws of nature is postulated for all observers whatever their positions and their state of motion. Such a formulation is clearly inappropriate in kinematic relativity. At the stage at which the cosmological principle is required laws of nature have not been defined. As was discussed in Chapter 1, the distinction between the actual motions and the laws of motion can hardly be drawn in cosmology, and is presumably quite inappropriate. The cosmo prinzip [my abbreviation] has therefore to be defined with respect to the actual aspect of the universe rather than with respect to the laws of nature. Now a good deal is known from purely terrestrial physics about observers at the same place in different states of motion. From this we know that although the laws of nature may be the same, the aspect of the universe will be different for observers in the same place in different states of motion. Accordingly, it is impossible to define the cosmo prinzip as implying that all observers, irrespective of their position and state of motion, obtain the same aspect of the universe. It becomes necessary to select a set of ‘fundamental observers’ of whom there is always one at each point. The cosmo prinzip, the contents of which will be discussed later, applies only to this set of observers.
Longair makes no such distinction in calling into service the fundamental
observers—he doesn’t say it is for purposes of satisfying the cosmo prinzip in kinematic relativity, just for making
time defined equivalently for observers throughout the U. Cosmic time.
But, I see now Bondi mentions fundamental observers in other
contexts. First, particles: “Any particle moving with the substratum is
called a ‘fundamental particle’.” Substratum
= the theo. construction that implies or states that the cosmo prinzip applies
in detail and not just statistically.
(See pp 65, 66.)
Then H. B. says: “In order to
apply the cosmological principle to the construction of the substratum it is
necessary to compare the physical aspect of the universe from various points in
it. For this purpose imaginary observers
have to be introduced, present at all points of space-time.” . . .
These observers are just a way of making specific what the cosmo prinzip
says: “any observers like ourselves
anywhere would obtain equivalent results from equivalent observations.” Hoo boy – observations or measurements, or
are they the same? The same, apparently.
An observer going by Earth at high speed is not a fundamental observer,
because he or she doesn’t see (see? observe? measure?) isotropy of U. So only observers to whom the U looks
isotropic (“no first harmonic deviation from isotropy”) are fundamental
observers. Real motions are the only
ones allowed, whereas in special relativity “equivalent observers means equivalent
for testing the laws of motion” – all possible motions, eh? Milne gets mentioned here (p. 67), too:
"The precise way in which these fundamental observers are introduced varies somewhat between different theories, but their distribution and general characteristics are always the same.” Oh, no! It’s the consistent observer—the horror of the universe (paraphrasing Brenda Ueland)! “An argument given by Milne which appears to be of rather restricted applicability shows that the observers must form a continuous rather than a discrete set, but in any case every current theory assumes them to form a continuous set."The cosmological principle may now be stated as: Every member of the 3-parameter set of fundamental observers obtains the same result of corresponding observations of the universe as every other member."
My question from p. 135 herein is definitively answered by Bondi on p.
71: “The universe itself therefore acts
as a synchronizing instrument which enables A and B (and hence all observers)
to synchronize their clocks.” Also: “Kinematic relativity also has a cosmic time,
and that cosmic time can only be dispensed with in a theory which adopts the
perfect cosmological principle, i.e., in the steady-state theory.” World map and world picture are also
mentioned on this page (Milne’s terms).
And next Bondi discusses whether cosmic time actually applies to the U
and not just to idealized models of it!
He says: “This question is common
to all theories other than the steady-state theory, but very little attention
seems to have been paid to resolving this problem which is relevant to the
logical foundations of all these theories.”
