7. A Visit With the Perplexed
Below is an actual post to the alt.physics.new-theories usnet newsgroup.
I will intersperse my commentary in bold font. -- Arf!
(The names have been changed to protect the ignorant)
>> Taking into account all of the earth's motions eg. polar, orbital,
>> galactic etc, how fast are we travelling?
Dan is asking for the absolute motion of the earth.>This worries me, too. Let me pose a couple of spaceship questions,
"How fast is the earth traveling relative to . . . nothing."
In Newtonian physics this was unfindable.
In Maxwellian physics this was findable but the experiments
came up, strangely, to detect no motion.
In Einsteinian physics the question is meaningless.
Now comes comments by someone else who does not understand
the most basic ideas of SR: -- Arf!
>1. Imagine yourself sitting in a sealed space capsule totally unaware
>of the outside world. You know the mass of your capsule, which is
>fitted with a rocket engine.
>You fire the engine and measure, (with a spring balance) your
>acceleration, which turns out to be, say, 3x10^6 metres per sec^2.
>After 200 seconds, you calculate that your velocity is 6x 10^8 m/s^2
>or double the speed of light.
Velocity relative to what? He doesn't say but from the context>Now, before the SR experts jump up and down with explanations about
we'll assume he means relative to the inertial frame he was in before
he fired the engines.
He also used the Galilean/Newtonian formula for calculating his final
velocity as measured in that inertial frame from the acceleration.
What he has calculated will NOT be what is measured by the folks
he left behind in the original frame.
They will measure him as going less than the speed of light in their
(and his original) frame.
>2. When I fired my rocket, did I accelerate or did I decelerate? What
>was my spatial reference? Had I already been travelling with constant
>velocity in the direction of the rocket jet?
Acceleration as opposed to deceleration refer to whether the speed>Now back to the relativists. They say that while I was accelerating,
is increasing or decreasing. This depends upon the frame of reference.
When the car steps on the brakes the people sitting by the road
observe the car slowing down. The people in the car in the next
lane (going the same direction) notice the formerly "stationary" car
speed up in the "backwards" direction. It all depends on the frame
of reference. This, by the way, is all old Galilean/Newtonian
physics and needs none of the subtleties of relativity.
His question as to what he had been doing before he fired the
jets also sounds like he was asking for his absolute state of
motion -- a direct contradiction of postulate 1) -- Arf!
Again he brings up the acceleration/deceleration question without a frame.>Ah! but unknown to me, my time scale had dilated and my length scale
Also the "mass increase" is frame dependent. The mass of an object
measured in different frames will, according to SR, give different
results. The different frames are neither mentioned or implied. -- Arf!
"MMX" refers to the Michaelson-Morely experiment. It was a famous>on the spatial references I used)
experiment done in the 1890's which detected no motion through
Again the time and length changes are differences in measurements made
in different frames. In his frame nothing has changed. In his original
frame (with respect to which he is now moving) his ship is shorter and
his clocks are running slower.) In some other frame his ship is
thinner. -- Arf!
In the frame of the ship now, the rocket exhaust is travelling faster>OK, that being so, I became an instant SR convert and tried to
than the ship (in fact, in the frame of the ship the ship is, by definition,
at rest) and therefore the exhaust experienced the "mass increase"
He is not specifying which frame(s) he is talking about. -- Arf!
He wants his ABSOLUTE velocity to put into the equations when the 'v'>From this apparent paradox and using all my brainpower, I was able to
in the equations stands for the velocity relative to the frame in which
the measurements are being made.
The Lorentz transform equations are a way to calculate length, time, etc.
as measured in a frame that is moving at velocity v RELATIVE TO YOU from
the measurements made in that frame. Thus if I make a bunch of
measurements in my frame and I am moving at velocity v RELATIVE TO YOU
then you can filter my measurements through the Lorentz transform
equations and get the results of measurements in YOUR frame. The poster
is attempting to apply the Lorentz Transforms to ONE FRAME ALONE. This
makes no sense. -- Arf!
Right! The equations are nothing more than formulas to calculate>However, since SR says that no such entity exists, I am now totally
measurements in one frame from measurements in another. There
must be two frames in order for the formulas to have meaning. Choose
different frames and you'll get different answers. He wants THE
ANSWER. It's like asking if Columbus, Ohio is to the north or not
without giving any leeway to where the asker might be located. He wants
the absolute true answer: is Columbus, Ohio to the north or not? -- Arf!
Hott2Trott's version of SR certainly is contradictory. However, it
bears little resemblance to Einstein's version.
Maybe he should be surfing this website. -- Arf!
Next: The Twin Paradox
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