motion in space 3c (short version) The space speedometer
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>>1. In a frame where the tethered system is seen to be moving, the
>>length in the forwards direction is contracted by the Lorentz
>>contraction.
Are you saying it is not contracted in the rearward direction?
Or are you saying that there is no physical contraction only the
illusion of contraction? I say that the tether is shortened physically by
half when aligned with the motion at 0.866 c.
>>2. In that frame, light signals sent in opposite directions along the
>>tether take differing amounts of time, so the times
>>at which they reach the ends differ,
Yes, this is what the experiment measures.
>> and they have moved by different amounts. This has the
>> effect that the effective length as seen in the frame of the
>> spaceships is enlarged back to its original value.
Are you sure about that? This is the case if the signal goes out then
back as in the Michelson-Morely experiment or with any one clock out
and back measurement of the speed of light. The distance c(t1+t2)/2
turns out to be the same as if both ends of the tether reflected the
signals back to the sender. Is this what you are saying?
>>3. You seem to be ignoring time dilation, although this does
>> not have a major effect on the other part of the argument.
No, I am saying that the clocks are dilated by half throughout
this experiment, when the Lorentz equations are put in to determine
how much each clock changes in addition to the half dilation; the
correction is far less than a nanosecond for each clock separately.
This is why I set it up at 86.6% c so that it would be easier to show
what is happening.
If you want to say that the contraction is an illusion , the two-clock
experiment still works, but I don’t think an MM or a one-clock
out-and-back experiment would work. The contraction of the MM
experiment is the basis of its so-called failure to detect the motion in
space.
What seems to be misunderstood about the experiment that I am
describing is that the signals are not reflected back by the other craft.
They go in one direction from the source. The signals expand
spherically from the point of origin, where the two antennas were at the
transmission time. The receivers and computers and clocks record
them as they pass anywhere from 720 to 10,032 nanoseconds later in
this particular instance.
It is a little like taking an atomic clock to several VLBA telescopes to
calibrate the on-site clocks. However, in this case it is much easier.
The clocks can move apart very smoothly and slowly relative to each
other without the need to be taken by airplane and truck to the various
sites across the country and world.
In fact it may make more sense to some if the clocks were mated with
the same type of tape recorders as used in VLBA operations. This
would also make it possible to record atomic-clock-controlled radio
transmitters and thus count the interference of the signal coming in
against a standard that is both going out and used to compare the
received signal wavelength to wavelength. With the simple version,
tapes would record the times that the signals come in relative to the
60-second time-mark, that each clock creates at the same time that
the transmitter generates the outgoing signal. The orientation of the
tether can be recorded from the gyros on the craft. When the tapes
are played back, side by side in the same machine, they will show very
nicely the shifting back and forth of the received signals. At the
maximum-minimum orientation, this experiment will record 9,312
nanoseconds difference in the two signals (10,032-720 n.s.).
When the clocks are well synchronized and the orientation of the
tether perpendicular to the motion, the tapes will show evenly spaced
signals 60 seconds apart, i.e. each signal has a 5,376 nanoseconds
travel time between the two clocks, but you always have to remember
that the receiver clocks are not in the same place they were when the
other clock created the signal. As the rotation continues, one will fall
behind until the tether aligns with the general motion. It then catches
up as the experiment rotates past the aligned state. At the other
perpendicular orientation, the signals are side by side again on the
tapes, and then the other tape’s signal falls behind. If the experiment is
done with clocks that are out of synchronization, the same pattern will
appear on the tapes except they will be offset by the sync error.
I think that if you put aside thinking of this as first a relativity
experiment, it will make more sense. I understand what you are trying
to say in each of your responses; and I understand that everyone who
understands the theories of relativity also accepts that we are not
supposed to be able to tell our motion relative to the frame of
reference of the photons or space-time. The responses you give
pertain to the single clock experiments or to the case where a signal is
sent back that says when the signal arrived or were, as some describe,
the TV camera watches a clock (or a telescope) and transmits the
result back in real time; i.e., with information that also travels at the
speed of light. Your remarks are also related to multiple reference
frames moving relative to each other as well as with respect to
space-time.
Most relativity thought experiments talk about three reference frames:
the two that the observers exist in moving at different velocities and
different locations or passing each other, etc. and the one that the
photons exist in. What is often forgotten is that the actual signals
actually move relative to space and are not at all concerned with the
transmitters and receivers when or until they are inside the equipment.
The photons are owned by space-time. The experiments also move in
space-time. This needs to be remembered.
With the two-clock experiment, there are only meant to be two
reference frames. The clocks are meant to exist in the same frame. If
we imagined them placed on a one mile in diameter disk would we not
think them to be in the same reference frame. But, it really doesn’t
matter whether they are in the same frame if the two tapes can be laid
side by side and the information shifts the same way for each
revolution. Any number of pairs of clocks could be placed on the disk
at all angles to each other and a procedure worked out for their
synchronization or the post synchronization of the data. It is the data
vs. the orientation that gives the time information. The clocks must tick
at the same rate. That is all that is required. Of course you need to
sample all the orientations to find the maximum-minimum line.
We could set up a thought experiment that looks just like the MM
experiment, one mile across and in space moving at 0.866 c. But then
it would not be as easy to explain how the clocks are synchronized.
You could have four clocks in two pairs; all synchronized. The
experiment could be run as an MM experiment at the same time as as a
two clock experiment. The signals would be picked up and recorded
as they are created, reflected, or received at all four locations. The
times at the start and end will be the same for both paths as it is in any
MM experiment.
The two clocks at the ends of a single tether is an easier experiment to
show synchronization. All you need to do is look at the recorded data.
Even though the null points where the times are equal may not be at
90 and 270 degrees, they will be symmetrical about the max-min line,
i.e. 38 degrees and 322 degrees. This would mean that one clock is
considerably ahead of the other.
Try setting up the thought experiment yourself. Think about how the
clocks will be synchronized. Forget FOR THE MOMENT not being
able to detect motion through space-time. It was being a positivist that
made Einstein want to get rid of the idea of an ether that was
undetectable. Positivism made him put this law into relativity. You have
two clocks that can stay in sync for many hours at a time. Each will
trigger the transmitter to send a signal into space-time, at the same
time, or as near as possible. Relative to these times, they await the
reception of the other’s signal and record the time of that reception.
They do not send this signal back, they each record it relative to the
time on the receiver’s clock. Later they compare these times and the
orientations to see how they vary. They will vary; otherwise the MM
experiment does not work.
The MM experiment works because the path out sideways and back is
the same as the path upwind and downwind (if I can use the old terms
of motion of light in space) The legs upwind and downwind are
shortened by half in the MM experiment moving at 0.866 c. The time
for the signal to go upwind is not the same as the time to go downwind,
nor is the time to go out sideways the same as either upwind or
downwind. The average of the two round-trip courses are the same,
however, and that is why the MM experiment does not detect motion in
space. ???? HOW WRONG DO YOU THINK I HAVE THIS
PICTURE????????
If you can take two clocks at the ends of a tether, you can measure
the upwind time and the downwind time in almost the same time-frame.
The signals start at the same time, they are not received and recorded
at the same time. Likewise, you can measure the outward and back
times (perpendicular) in exactly the same time-frames. Because the
perpendicular times should be the same, we have a perfect way to
judge the quality of the synchronization. We know the direction with
respect to space, because that is where the times are the most
different (at least in the plane of the rotation). The lack of good
synchronization changes the magnitude of each time, depending on
which clock is in front, etc.
The concept of the experiment is easy once you see it, but it does
break a cherished law of the theories of relativity. There are many
reasons why we don’t want this law broken. I have read most of the
books written by everyone who has written about relativity. I
understand what you are saying and why you say it.
I may be wrong. Everyone must start out assuming I am. This is
understandable.
If you look at space from the uncertainty-principle point of view, it can
make sense that this experiment does not work. With the quantum
theory, it is not clear what is moving through space with respect to
photons, and it is not clear at all why they move. If, however, you
believe that signals of events travel across space somehow relative to
that space they are moving through, then this experiment is easy to
figure out. If you think that the VLBA works because of the uncertainty
principle, you will have a problem with this two-clock experiment. If you
think that relativity works because of uncertainty principles, the
two-clock experiment will not be understood.
I think there is a much simpler explanation for photons moving through
and across space, so this experiment is easy for me to keep pushing
onto the newsgroups at this time.
If the VLBA works because of the uncertainty of the position of a
photons position, and this uncertainty stretches sideways, forward, and
back relative to a particular signal or photon, for miles in this case, and
all this coordinated information is just probability, then you will probably
have problems with these two-clock experiments. This all ties back to
why it is not easy to find a satisfactory explanation of why one photon
or one electron can pass through two holes in an interference
experiment. Quantum theory expects it to happen, but, as many have
said, quantum theory does not explain why it happens. The Aspect
experiment is another example that quantum theory handles well, but it
does not explain why it happens very well.
The theories of relativity and the quantum theory leave the concepts of
space in such limbo that anyone who has an interest in how the
universe works will always be frustrated by the contemporary Standard
Models. The books written about relativity in recent years have made
nature look more like black magic than the complex, poorly understood
mystery that it is. The kids who will become the physicists of tomorrow
will find it hard to be challenged by some of this material. In the context
of the two-clock experiment relativity becomes very clear, plus a major
dilemma is cleared up. A new dilemma takes its place, but one that is
very revealing rather than confusing.
For the working scientist, a working model is always workable. The
model need only be partly right to be of value in the domain where the
work is done. At the extreme end, it is not always so workable- as the
modern times are beginning to show. But on the other hand our daily
lives work perfectly well with the Standard Model.
It would be nice to have a better concept of space than we have with
the S.M.
S.A. Benson
PS If you assume that relativity is right in all respects, then you can
reject the two-clock experiment out of hand. However, this is not a
complex relativity experiment. It involves creating signals in two
different places at the same time (with as much care as possible) and
the later interception of the signals by the opposite clock, recorder, etc.
The experiment is not the typical relativity experiment. It is really not a
relativity experiment at all. It is just that we know that clocks run slower
and rods get shorter with motion through space. Measuring the
difference between passage times is really a clock-and-recorder
problem. It is also good to remember to make the experiment big
enough so that a standard atomic clock can measure the difference in
passage times. The MM experiment expected an extremely small
difference in time if the idea was to work as Michelson expected it to.
Two standard atomic clocks 10,000 miles apart moving a few miles per
second will show a good deal of difference in the two times,--- 1156
nanoseconds.