Re: beginner thought experiments
- From: "PD" <TheDraperFamily@xxxxxxxxx>
- Date: 3 Jul 2006 17:38:58 -0700
Henry Haapalainen wrote:
"Tom Roberts" <tjroberts137@xxxxxxxxxxxxx> kirjoitti
viestissä:1W_og.125521$dW3.25242@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Ning Hu wrote:According to laws of physics wave-lenghts do not change.
Hi I have a few thought experiments I like to see how other peoples
opinions are on the results,
You have received a number of replies from people who know nothing about
modern physics, but who nevertheless have strong opinions about such
things. If you really are interested in _OPINIONS_ then they are valid.
But if you are interested in _SCIENCE_ they are not.
I will discuss science.
Experiment 1:
A space ship travelling at close to the speed of light shoots a
constant stream of Laser beam out of it's back end. To a stationary
observer away from the space ship, Does the beam travel at speed of
light or does it travel at the speed of light minus the speed of the
space ship?. What does the people on the space ship see?
My opinion does not matter. But my knowledge of experimental tests of SR
does. Experiments similar to this have been performed, and always yield
the value c in an inertial frame relative to which the emitter of the
light is moving. An observer in that frame observes that while the light
moves with speed c, it is redshifted compared to what people on the ship
would measure. People on your space ship cannot see the light, because
they cannot intercept it, given your configuration. If the light source
were located such that they could observe it, they would see nothing
strange, and the frequency and wavelength of the light would be their
usual values for that particular source.
This is, of course, completely in accord with the prediction of special
relativity.
Which laws of physics would that be?
That is bad
physics. (HH)
Experiment 2:
point A, B and C lay on a straight line with B being the midpoint of A
& C. Assuming B to be a stationary point in space. 2 friends depart
from point B in similar space ships, 1 heading for point A and the
other heading for point C at same speed/accelleration, When they reach
their destination, they will both turn back and head back towards B.
Have they aged the same amount when they finally unite?
With the same background as above, yes they will have aged by identical
amounts. I'm implicitly assuming that your "stationary point in space" is
at rest in some inertial frame that extends sufficiently accurately to
include the entire trips of both friends.
It can be difficult for an inexperiencesd person to tell sense from
nonsense around here. The only way I know is based on the fact that the
cranks and idiots do not refer to physics textbooks, while knowledgeable
people often do. I recommend:
Taylor and Wheeler, _Spacetime_Physics_.
Tom Roberts
.
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- From: Henry Haapalainen
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