A Physics forum. Physics Banter

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » Physics Banter forum » Physics Newsgroups » Physics - General Discussion
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

Tags: ,

(SR) Lorentz t', x' = Intervals



 
 
Thread Tools Display Modes
  #1  
Old April 7th 05 posted to sci.physics,sci.physics.relativity,alt.physics,sci.math
The Ghost In The Machine
external usenet poster
 
Posts: 4,201
Default (SR) Lorentz t', x' = Intervals

..answers groups snipped.

In sci.math, Eleaticus

wrote
on 06 Apr 2005 04:44:46 GMT
:

Disclaimer: approval for *.answers is based on form, not content.
Opponents should first actually find out what the content is,
then think, then request/submit-to arbitration by the
appropriate neutral mathematics authorities. Flaming the hard-
working, selfless, *.answers moderators evidences ignorance
and atrocious netiquette.
Version: 0.02.1
Archive-name: physics-faq/criticism/lorentz-intervals
Posting-frequency: 15 days


(SR) Lorentz t', x' = Intervals
(c) Eleaticus/Oren C. Webster



------------------------------

Subject: 1. Introduction with the obvious debunking
of the use of 'just coordinates' in any
scientific formula.


Defenders of the Special Relativity faith are especially
fond of telling opponents of their space-time fairy tales
that they do not know the difference between coordinates
and magnitudes.


There are a few quirks.


That may often be so, but the fault lies ultimately with
SR dogma. The Lorentz-Einstein transformations cannot
possibly be 'just coordinates', which is the interpre-
tation required to support the many sideshow carnival acts
with which the SR faithful bedazzle the public, and establish
their moral and intellectual superiority.

If I get in my car and drive steadily for a few hours at 50
kilometers per hour, is 50t the distance I travel?


A unit-conversion problem. I'm not sure how seriously anyone
will take this proposal, but I propose a 'nil' to be the
distance light travels in a nanosecond. (This would be
exactly 0.299792458 m in more conventional measurements,
or just shy of an Imperial foot.) Therefore, you're suggesting
driving at velocity 74.5582 nils/s, or 268.410 kilonils per hour.
(Lightspeed is 1 giganils/s.) At the end of an hour,
of course, you've driven 268.410 microseconds -- so to speak.
More precisely, you've driven a distance in an hour that would
take light 268.410 microseconds to cover.

Of course it gets more complicated if one adjusts one's
clock properly; accelerating the car to 74.5582 nils/s will
slow down the carborne clock by a factor of about
2.78 * 10^-15 for the duration of the trip; since the trip
takes an hour one loses 10 picoseconds. This is probably
a detail that can't be measured at these velocities.


Of course not. The last time my hours-counting 'just coord-
inates' clock was set to zero was when Zeno first reported
one of his paradoxes to Parmenides.

That was a long time ago, so my t is not useful for such
purposes unless you also use my clock to established the starting
time, perhaps t0, and use the formula 50(t-t0) to calculate the
distance.

In any case, my t is even then not 'just a coordinate' because
it always represents particular elapsed times that can be
used in the (t-t0) form to calculate perfectly good time
intervals (elapsed times).

Alternatively, I could (re)set my clock to zero at the start
of some meaningful time interval, in which case my t shows a
scientifically perfect current and/or end time.

In which case, the Lorentz-Einstein t'=(t-vx/cc)/g is a function
of an elapsed time interval (not 'just a coordinate') and a time
interval (-vx/cc; the interval amount the t' clock is being
screwed up at time t) and thus cannot be 'just a coordinate'
since neither of the independent variables is such a 'just' thing.
{Their meaning is shown below, step-by-step.]


If it takes me 50 minutes to cross the Interstate highway,
was x/50 my velocity crossing it?


Your average velocity, in somethings per minute. (What
units are *you* using?)


Of course not. The origin of all my axes is at the very
spot where Zeno first presented his first paradox to
Parmenides. That makes my x equal a couple of thousands of
miles, plus, and is not useful for such purposes unless
you establish the starting x value, perhaps x0, and use the
formula (x-x0)/50 to calculate my velocity.

In any case, even then my x is not 'just a coordinate'
because it always repesents particular distance intervals
that can always be used in the (x-x0) form for any and every
scientific purose.

Alternatively, I could move my x-axis origin to the starting
(zero) point of some meaningful distance, in which case my x
shows a scientifically perfect current and/or end distance.

In which case, the Lorentz-Einstein x'=(x-vt)/g is a function
of a current/ending distance interval (not 'just a coordinate')
and a distance interval (-vt; the interval amount the x' axis
is being screwed up at time t) and thus cannot be 'just a coordinate'
since neither of the independent variables is such a 'just' thing.
{Their meaning is shown below, step-by-step.]


------------------------------

Subject: 2. Table of Contents

1. Introduction with the obvious debunking
of the use of 'just coordinates' in any
scientific formula.
2. Table of Contents.
3. The Lorentz-Einstein transforms.
4. The 'just coordinates' argument.
5. Single-system, little-purpose ambiguity.
6. Relating two coordinate measures/systems.
7. Distances and moving coordinate axes.
8. Time intervals.
9. Einstein's (1905) derivations.
10. A word about intervals.
11. Intervals versus the Twins Paradox.
12. Summary

------------------------------

Subject: 3. The Lorentz-Einstein transforms

Special Relativity's space-time circus is based on
the 'transformation' equations by which it is believed
one can relate a nominally 'stationary' system's space
and time coordinates to those of an inertially (not
accelerating) moving other observer.

That moving observer's own physical body and coordinate
system might have been identical in size to those of the
stationary observer before the traveller began moving,
but are 'seen' as very different by the stationary observer
when the relative velocity of the two is great enough, a
high percentage of the velocity of light.

Concerning ourselves - as is customary - with just
the spatial coordinate axis that lies parallel to
the direction of motion, and with time, Einstein
arrived at these formulas that relate the moving
system measures or coordinates (x' and t') to the
stationary system coordinates (x and t):

x' = (x - vt)/sqrt(1-vv/cc) (Eq 1x)
t' = (t - vx/cc)/sqrt(1-vv/cc) (Eq 1t)


Be extremely careful here. Einstein in particular
used chi and tau. I like to use (x_O, t_O) and (x_A, t_A),
for clarity (tagging the coordinate systems with the name
of the observers).


The v is for the two systems' relative velocity as seen
by the stationary observer, and is positive if the dir-
ection is toward higher values of x. By concensus,
the moving system x'-axis higher values also lie in
that direction, and all axes parallel the other system's
corresponding axis.


Actually, it's a little more complicated in 4-space.
However, the Lorentz reflects things more or less properly;
if x_A = (x_O - v * t_O) * gamma(v), then it's clear that,
as t_O increases, x_O must increase with positive v if x_A
is to be constant (e.g., a certain point within A's car,
snail shell, boat, or spacecraft).


We used vv to mean the square of v but might use v^2
for that purpose below. Similarly for c.


Poor editing. If you're going to post this tract once
a week at least take the time to clean it up in a
text editor *then* cut and paste it.

Not that it's all that useful to post it anyway.


Because it is believed that no physical object can
reach or exceed c, the square-root term in both
denominators is presumed always less than one, which
means that the formulas say both x' and t' will tend to
be greater than x and t, respectively. However,
SRians call the x' result 'contraction' - which means
shortening - and the t' result 'dilation' - which
means increasing.


Ah yes, that old chestnut.

It's not really a contraction or an expansion, but a
*hyperbolic twist*. The problem setup gets complicated,
but here's one method.

O and A are the customary observers. At time 0 they are
coincident, for mathematical convenience. O has marked off
two points, one at his local origin, and one some distance
along the x-axis (call the distance d_O). How does A determine
d_O, assuming the Lorentz?

It turns out the simplest method by which A can measure d_O is
by simply taking the time he crosses over the first mark
(namely, 0), and the time he crosses over the second mark
(call it t_A), subtracting the two, and doing some fiddling.
How much fiddling?

Well, the second mark is at

x_A = (d_O - v * t_O) * gamma(v)
t_A = (t_O - v * d_O / c^2) * gamma(v)

where t_O is some convenient value (as the mark is expected
to last indefinitely.

Since A passes directly over the mark we have x_A = 0, or
t_O = d_O / v. Therefore,

t_A = (d_O / v - v * d_O / c^2) * gamma(v)
= (d_O/v) * (1 - v^2/c^2) * gamma(v)
= (d_O/v) / gamma(v) .

Did the length contract or expand here?

Another alternative is for A to shoot out a lightbeam at d_O
the moment he crosses over the first mark, and then try
to compute the length from a small reflective mirror that
O has conveniently placed at the second mark. As O sees it,
A emits a lightpulse at (0,0) and hits the mirror at
(d_O, d_O/c), coming back to O at (0, 2*d_O/c).

What does A see?

Well, the mirror in A's coordinate system transforms into

x_A = (d_O - v * d_O/c) * gamma(v)
= d_O * (c - v)/c * gamma(v)
t_A = (d_O/c - v * d_O/c^2) * gamma(v)
= d_O * (c - v)/c^2 * gamma(v)

Since A cannot see this directly (the light has to get back to him),
the measured time -- call it t_m_A -- is t_A + x_A / c.
This gives us

t_m_A = 2 * d_O * (c - v)/c^2 * gamma(v)

A might naively assume that the distance is c * t_m_A -- and
he'd be wrong.

Since c/(c-v) = 1/(1 - v/c)
= 1/sqrt((1 - v/c)*(1 - v/c)) 1/sqrt((1 - v/c)*(1 + v/c))
= gamma(v)

for positive v, t_m_A is again too short, although not by the same
factor as the earlier measurement.


------------------------------

Subject: 4. The 'just coordinates' argument

The 'just coordinates' argument is so patently ridiculous
that even opponents have a hard time accepting just how
simple and obvious its debunking can be, as shown in this
section. However, further sections take a more arithmet-
ical approach that you'll maybe find more professorial.

The 'just coordinates' argument is that t is mot a
duration, not a time interval; it's just an arbitrary
clock reading. But what if the moving system observer
comes speeding by while you make your annual 'spring
forward' or 'fall back' change? The formula says that
the moving system clock's 'just coordinate' reading
can be calculated from yours:

t' = (t - vx/cc)/sqrt(1-vv/cc) (Eq 1t)


Imagine the moving system oberver's confusion if his
clock changes its reading while he's looking at it!


But clocks *always* change their reading while one's looking at it.
If one takes one second to read a clock, the clock advances by
one second as one is reading it.

As it is, most scientists ignore this issue anyway, using
GMT or just using a high-precision interval timer. If one
wants to call that a duration as opposed to a reading, fine --
SR has the implicit assumption that space is isotropic and
that one can move and rotate the coordinate system using
any rigid transform (combination of translations and rotations),
prior to the start of the actual measurement -- and after
the measurement if one is careful about one is doing (one
has to avoid, for example, Sagnac's effect).

So this particular objection verges on the silly.

[snip for brevity]

------------------------------

Subject: 5. Single-system, little-purpose ambiguity.

Since we're going to be comparing measurements on two
coordinate systems in the next section,


Are we? Be extremely careful here.

let's go to
our supply cabinet and get our yard-stick (which we
use to measure things in inches) and our meter-stick
(which we use to measure things in centimeters).

Here, I'm getting mine. Oh! Oh!


I'm going to get my nilstick. It's just under a foot
long and works very well -- it's also made purely
of light rays.


There's an ant on mine, and he ... she ... sure is
hanging on, right at the 3.5 inch mark of the yard-
stick.


And how long, wide, and thick is this ant?


Let's see if I can wave the stick around enough that
she'll let go. Nope.


Sagnac's effect.


However, before I gave up I waved the stick and the
ant 'all over the place".


That's about as precise as me pointing vaguely eastward
and stating "London is thataway".


Always, however, the ant was at the 3.5" mark on the
yard-stick, and always 3.5" away from the end of the
stick, however far and wide I have transported her.


In the stick's coordinate system, yes. To properly
characterize the motion in the world's coordinate
system I'd need some more details.


Neither of those 3.5" facts means very much. Of the
two, the distance aspect meant almost nothing. So
the distance was 3.5" from the end. So what? That
length, distance, was not in use. And only maybe
the ant might have been concerned with just what
location, 'just coordinate', on the stick she was
at.

Just so with x and t.


You do have a point. Any (O,A) problem has to reflect
the fact that light travels at lightspeed back to the
observer. In the computations above I took pains to
ensure exactly that. Otherwise, one has what I might
call a "phantom observation". Any x != 0 for either
coordinate system might fall into this category.

Even OWLS measurements might fall into this category,
as an OWLS measurement requires the difference between
two measurements of two clocks -- and these two clocks
are by their very nature *in two different coordinate systems*.

A TWLS measurement merely requires a mirror, a good clock,
a good marker, and a light source.


So, is the 3.5" reading just a coordinate? Or a
distance/length? It's ambiguous in and of itself,
and really makes no difference what you say until
you try to make use of the number.

Hey, my address is 5047 Newton Street. If you
are looking for me and you're at 4120 Newton, it
is helpful information, because it tells you which
direction to go. Is that 'just coordinate'?


There are a large number of Newton Streets. My Newton
Street might be somewhere in San Francisco. Yours
might be somewhere in Dallas. His might be in
Concord -- and it gets *really* squirrely as there
are a fair number of cities named Concord!

Small wonder the USPS created long ago the notion of
5-digit (or 9-digit) numbers to zip the mail to
where it's intended to go.


Where it really becomes useful, perhaps, is in
telling you how far away I am. That's not just
a coordinate value, that's a distance, length,
interval.


Not really. In some streets, houses are numbered
every 2; others might decide to use 10 as a delta.
Still other locales might use 100 -- usually for
large commercial buildings. Conversion into
yard, meters, nils, or miles is at best approximate,
and at worst downright impossible.


However, it is subtracting 4120 from 5047 that
tells you which direction and how far.


Not really. For starters, the direction is not
directly along the street -- in most locales even
numbers and odd numbers occupy opposite sides.

It gets even wackier when Newton Street sits exactly
on a city boundary, which means City A gets to number
the houses on its side of the street as it likes, whereas
City B numbers its houses according to its desires.
Much hilarity -- if one can call it that -- may ensue.

It is only
because both 5047 and 4120 are distances from the
same point - ANY same point - that the result means
anything.


They don't mean that much, even if all of the preceding
are discounted. Most housing developments have
varying-size lots. I've also neglected to mention
corners and bends.


My x - my yardstick reading - is always a distance
or length; it is impossible to be otherwise with
an honest, competently designed yardstick.


At least on a yardstick one has a fighting chance
of uniform lengths -- unless you're waving it
around, which induces various forces on your ant
because of centripetal considerations.


Whether or not its reading is of good use in some
particular scientific formula depends on whether
I put the zero end of the yardstick at some useful
place. As in the introduction, we should either
put it at the starting location/end, or use two
readings from it: (x-x0).


And there's also the issue of the size of the tick --
or the ant.


------------------------------

Subject: 6. Relating two coordinate measures/systems.

Taking care to not damage our brave little ant, I place
my yard-stick onto the table, zero end to the left, 36"
end to the right.

Now I place the 'just coordinate' meter-stick on the table
in the same orientation, in a random location, and find
that the ant's coordinate on the meter-stick is 51.


And I place my nil stick on top of both of yours (it
is transparent and has a channel; the ant is safe)
and get a reading of 19.105. Your point is valid
but very long-winded.

[snip for brevity]

But, you say, the Lorentz transform contain a -vt term.


That it does, out of necessity. Even the conventional Galilean
transform:

x_A = (x_O - v * t_O)
t_A = (t_O)

has such a term. To omit that term freezes the problem.

Or has it ocurred to you that the ant, after you've made it
yardstick-sick, might want to move along its length to somewhere
else to avoid your armwaving? So after you've put the stick
down it's at the 3.5 mark. However, 1 second later, the ant,
crawling at a uniform velocity of 0.5 in/sec, will end up
at the 4.0 mark. 2 seconds later, it will be at 4.5 mark,
and it will eventually crawl off the stick, and presumably to
someplace a little less whirly, like her queen's anthill... :-)

Just for giggles, the ant is wearing a wris****ch, and has
a tiny little ruler of her own, anchored permanently on
her thorax. Not much use, perhaps (it's always 0 at
her thorax), but it's clear that that v * t_O term,
assuming her watch remains synchronized (or nearly so)
with the table-clock, is necessary.


------------------------------

Subject: 7. Distances and moving coordinate axes.

We discovered x'=x.z' + x/g as the correct formula
for relating one coordinate to another system's.

But the Lorentz transform contains another term,
-vt/sqrt(1-vv/cc). What is it?

Let's start with our x'=51 cm, x=3.5", x.z'=42.11 example.

Every minute, let's move the meter-stick one inch to our
right.

At minute 0, the cm reading was 51 cm.
At minute 1, the cm reading is now 50 cm.
At minute 2, the cm reading is now 49 cm.

In this instance, v=1 inch/minute. And t was 0, 1, 2.

What has happened is that we have made our x.z' a lie,
and increasingly so. -vt/.3937 is the change in x.z'.


x' = (x.z - vt/.3937) + x/.3937.

Obviously, vt/.3937 is not a coordinate; even most SRians
wouldn't imagine it was. It is an interval, the distance
over which the moving system has moved since t=0.


And, of course, x/.3937 is the distance of our brave
little ant from the point where x=0 and the centimeter
reading is x.z'-vt/.3937. Yes, every minute the meter-
stick moves to the right and the meter-stick coordinate
of the spot where x=0 gets less and less - and eventually
negative.

Make sure you understand that every minute the x'
coordinate, because of -vt/g, becomes a better measure
of, say, the 3.5" paper we might be measuring with
the yard-stick, given that 51 was too big a number and
-vt is negative. That is, until the two origins coincide
at x'=x=0, and then it gets worse and worse.

With -vt positive (because v0) the situation is different.

With 51 and -vt positive, x' just gets worse and worse
over time.

Quite obviously, the fact that we now have the
correct formula for relating an x interval to an
arbitrary x' coordinate even when the x' axis is
moving, does not mean that x'is anything more than
nonsense for use in any scientific formula.

Unless we were smart enough to put the x zero point
in a useful location, and use (x'-x.z'+vt/.3937) in
the scientific formula. (x'-x.z'+vt/.3937) equals the
useful, Ratio Scale value x/.3937.


Actually, it doesn't. Of course your v = 1.4121 * 10^-12 c
will yield gammas on the order of (1 - 10^-24), which
would basically be an error of about 15 atomic nuclei per
astronomical unit (if that) -- but it's not exactly zero.


------------------------------

Subject: 8. Time intervals.


[snip for brevity, as it's redundant]


------------------------------

Subject: 9. Einstein's (1905) derivations.

When we return to Einstein's derivations of the transform
formulas with a well-focused eye, we find he was a wee bit
confused - or at least self-contradictory.

When he set up his (at first unknown) tau=moving system
time formulas, he created three particular instances of tau.

Tau.0 is the time at which light is emitted at the moving
origin toward a mirror to the right that is moving at rest
wrt that moving origin and at a constant distance from that
origin. He lets the stationary time slot have the value t,
a constant, the stationary system starting time.

Tau.1 is the time at which the light is reflected.


Tau.1 is a phantom time; it cannot be directly observed.

He lets the stationary time be t+x'/(c-v); t is still a
constant and x'/(c-v) is the time interval since t.

Tau.2 is the time at which the light gets (back) to the
moving origin. The stationary time value is put as t +
x'/(c-v) + x'/(c+v); t is still a constant and x'/(c-v)
+ x'/(c+v) is the time interval since t.

On the thesis that the moving observer sees the time to
the mirror as the same as the time back to the origin,
he sets

.5[ tau.0 + tau.2 ] = tau.1.

Tau.0 completely drops out of the analysis and leaves
no trace, and has no effect.


That's what YOU think. tau.2 = tau.0 + delta.tau; this
means tau.1 = tau.0 + 1/2 delta.tau, whatever delta.tau
might be. Granted, this is easily fixed by translation
of the coordinate systems.

It's not dropped out at all, and a careful analysis
will show this.


Further, the t you see in tau.0, tau.1, and tau.2 also
completely drops out with no trace and no effect, leaving
us with exactly what you'd get if you had explicilty said
t' is an interval and so is t.


Same issue, same fix.


What doesn't drop out in the stationary time values is
x'/(c-v) and x'/(c+v), the time interval it takes for
light to get to the fleeing mirror, and the time interval
it takes for light to get back to the approaching origin.

Thus, his resultant t' formula is strictly based on time
intervals in the stationary system. Time intervals since
some starting time, yes, but time intervals.

There is absolutely nothing in the derived formulas that
depends on arbitrary coordinates like the constant t in
the stationary time arguments.

Let's look at the x dimension; it is x'=x-vt [as x increases
by vt, the effect over time is x'=(x+vt)-vt)], which Einstein
explicitly sets up as a constant stationary distance.

He uses that x' not just in the time interval parts of the
stationary time arguments, but also in the x (distance)
stationary system argument for the tau at the time light
is reflected.

x' can't be the stationary system coordinate of the mirror
at that time. That value is x'+vt.

x' is explicitly an interval, distance.

Thus, the whole tau derivation of the t' formula is fully and
explicitly based on x' - a spatial length/distance/interval -
and the two time interals x'/(c-v) and x'/(c+v).

While we're at it, if the starting t is not zero, his
x'=x-vt formula is complete nonsense also. Given that
there was some L that was the mirror x-location and length
when the light is emitted, if t was already, say, 500, then
x'=L-vt could have been a very negative length.


The issues here are fixable. The conventional SR coordinate
system has both observers O and A coincident at time t_O = t_A = 0.
(Or, if you prefer, t = tau = 0.) The same is true for x_O = x_A = 0
at time 0.

If one prefers, one can use tensors. I'd have to look up the details
but from a functorial standpoint (if that's the word I want),
one can define

x_A = f(x_O, t_O)
t_A = g(x_O, t_O)

and work from there. The pair (f,g) constitute some sort of tensor.
Einstein goes on to prove that the tensor must ultimately resolve
to the Lorentz.



------------------------------

Subject: 10. A word about intervals.

There are intervals, and there are intervals.

If we put our yard stick zero point at one end
of a piece of paper and read off the coordinate
at the other end of the paper, we have a good
measure of the paper's length, a Ratio Scale
measure. [Absolute temperature scales are ratio
scale.]


Actually, we do not. How did you orient that paper?
Did you measure along an edge? Did you just drop the
stick in any old orientation on a sheet of paper that just
happened to be on the table first? Is there a Rubik's Cube
under the paper, distorting it? Did your dog (assuming you
have one) chew the paper first? What if your 3-year-old
son (ditto) decided to play "crumple the tax form, Daddy"?
What, precisely, are you measuring?

Even if one assumes an edge measurement of an
idealistically flat 8 1/2" x 11" 20-pound bond sheet with
perfect 90 degree corners, there's still the issue of
which edge.


If instead we put the one end of the paper at the
one inch mark (or the zero end of the stick one
inch 'into' the length of the paper) we get measures
that are one inch off the true, ratio scale length.

The two messed up measures are still intervals,
but they are Interval Scale measures. [Household
temperature scales are interval scale, which is
why your physics and chemistry professors won't
let you use them without first converting to the
ratio scale absolute temperatures.)

t'=t/g and x'=x/g represent ratio scale measures,
given that t and x were ratio scalae to start with.

t'=t.z'+t/g and t'=t/g-vx/gcc are both interval
scale measures, even given a good ratio scale t
and a good ratio scale x.

x'=x.z'+x/g and x'=x/g-vt/g are both interval
scale measures, even given a good ratio scale x
and a good ratio scale t.

Look for the "(SR) Lorentz t', x' = degraded measures"
document soon at a newsgroup near you.


So convert them to a convenient coordinate system first.

Oh, look. There's a *second* sheet of paper underneath
the first, offset to (but in the same orientation as) it.

*Now* what are you measuring? Same issue as your
"offset mark" -- and there's no real good coordinate
system, just convenient ones.


------------------------------

Subject: 11. Intervals versus the Twins Paradox.

t'=(t-vx/cc)/g shows t' being greater than t.


Be extremely careful here. As you may have noticed
in my computations above, the time interval measured
by the moving observer depends on precisely how
he measures it.

In fact, t' = 2 * d_O * (c + v)/c^2 * gamma(v) might
apply, if one assumes marks (in O's space) at
x_O=0 and x_O = -d_O, and A fires a beam of light
at the mirror attached to the mark at the instant
his origin passes over O's. (This is merely t_m_A with
-v substituted for v.)


The reason Special Relativity will not allow the
use of its basic time equation in determining what
SR has to say about the twins' ages, is that t' and
x' are supposedly just coordinates, and they say you
have to take the coordinate pairs (t',x') and (x,t)
into consideration in both the time and place the
twins' separation started and the time and place the
twins reunited.


Actually, SR isn't all that useful here anyway. The
twin traveling in the rocket is experiencing acceleration,
which is explicitly forbidden in SR problems. With
the usual formulations of the twin paradox, admittedly,
the rocket twin will be converted into meat jam (if the
rocket doesn't simply disintegrate because of the
very heavy forces during acceleration!).

Assuming Newtonian ideals the acceleration of the
rocket twin to near lightspeed will take the better
part of a year (g = 9.805 m/s/s, c = 299792458 m/s,
t = c/g = 30575467.4 s, 1 Gregorian year = 31556952 seconds).

(It will also take a ridiculously large amount of rocket fuel.)

[rest snipped]

Here are a few thoughts for you.

[1] Your comments aren't too bad -- but extremely long-winded.
My requirements for any thought experiment are these:

[a] Define your coordinate systems properly.
[b] Make sure you know what you're measuring, and how
you're measuring it, and in which coordinate system
you're measuring.
[c] Explicitly state your assumptions.
[d] Remember that x_O != 0 and x_A != 0 are "phantom measurements";
the observer is forever anchored at his origin and cannot
move therefrom. Since lightspeed is constant the adjustment
is relatively simple, of course -- just add (or subtract)
x_A / c, and you've got your time interval.

[2] There's nothing wrong with shifting coordinate systems, as long
as one follows [1][a] and uses rigid transformers (translations
or rotations). Note that moving something at a uniform velocity
might be construed as a shear -- although in SR's case it's
more like a hyperbolic rotation.

[3] SR and GR have been validated by a bevy of scientific
experiments, from the MMX (which admittedly is a
weak validation as it also can be used to justify
BaT/emissive theory; the only thing MMX disproves
is the notion, apparently common at the time, that
lightspeed is c relative to a single unique fixed
source) to the extremely sophisticated measurements
being currently conducted by Gravity Probe B and
the computations of Mercury's orbital perturbations
and various orbiting binary stars -- some of which
contain pulsars.

Derivatives of SR and GR must also be used in design of
such things as particle accelerators, which routinely
accelerate particles faster than light -- if one
believes in Newtonian theory, which doesn't work at
such power levels. It turns out the accelerators
see mass gains, which must be compensated for.

[4] There is no absolute velocity. Even in the case of light, there's
only an absolute speed.

[5] Nothing you've stated here disproves SR, from a mathematical
standpoint. It is merely a warning that one has to be careful
during problem setup.

--
#191,

It's still legal to go .sigless.
Ads
 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
(SR) Lorentz t', x' = Intervals The Ghost In The Machine Physics - General Discussion 0 December 18th 04 04:01 PM
(SR) Lorentz t', x' = Intervals Uncle Al Physics - General Discussion 1 November 17th 04 02:13 AM
(SR) Lorentz t', x' = Intervals Uncle Al Physics - General Discussion 0 November 1st 04 03:31 PM
(SR) Lorentz t', x' = Intervals Uncle Al Physics - General Discussion 2 August 15th 04 01:05 AM
(SR) Lorentz t', x' = Intervals Dirk Van de moortel Physics - General Discussion 2 September 26th 03 12:16 PM


All times are GMT +1. The time now is 09:34 AM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2008, Jelsoft Enterprises Ltd.Search Engine Friendly URLs by vBSEO 2.4.0
Copyright ©2004-2008 Physics Banter, part of the NewsgroupBanter project.
The comments are property of their posters.
iPhone Reviews - Your File Host - Remortgages - Remortgage - Car Accident Lawyer Los Angeles