Re: nearest star much closer ?


Mo wrote:

...

A distance in the solar system would be much further
outside the solar system. Atoms would be much larger.
You are not thinking Einstein.

George Dishman wrote:
It seems to be you who is confused, you asked what would
happen if the speed were greater _beyond_ the solar system.
The Earth's orbit is _within_ the solar system so unchanged.
...
Light could cross interstellar distances in less time, but it
would still travel in straight lines so parallax measurements
of distance, such as those made by the Hipparcos mission
would still be valid since our baseline length is correct.

The distance to the nearest star falls predominately in the
space outside the Solar System, so this distance needs to be
measured with measuring sticks from this outside space.
the baseline has to measured with these outside sticks also.

The sticks are defined as being 1 metre long so should
be the same length regardless of the speed of light. If
the speed of light varies, for example due to the refractive
index of a material, the length of the metre is unaffected
because the definition is based on the speed in a perfect
vacuum.

Thus the baseline we use would be incorrect.

The baseline is measured using light _inside_ the solar
system so is correct. Distances outside are measured
using a technique called parallax whch uses only the
baseline length and a measured angle so still gives the
correct answer.

http://en.wikipedia.org/wiki/Parallax

George

.

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