Natural Science Forum / Physics / Particle Physics / September 2004

Point taken. To answer your question, the background radiation of
space (2.7K) is "uncoupled" from the universe. That's why it is an
accurate remnant of that period 400,000 years after the Big Bang. As
such, it does not effectively change the speed of light in space
compared to the vacuum. Now, interstellar gas does have an effect, but
interstellar gas is so dilute that (I believe) the increment above 1
for the index of refraction is too small to be measured. I would be
thrilled to learn otherwise from someone who knows the measurements
better.

As to your object lesson, I would modify the parable.
Imagine a boy who asks a teacher a question. The teacher doesn't
understand the question. The boy repeats the question, which is "What
is 12-5?". The teacher says, "It's in your textbook, and it's part of
your homework. Why are you asking me for the answer you should be
learning yourself?" The boy doesn't like that answer and goes to the
library and finds an algebra book. The boy spends endless hours
frowning at the algebra book and then, after some days, comes back to
the teacher and says, "This book says 12-5 = x." The teacher says,
"Silly child. You refuse to do your homework. Stop studying a book you
are not ready for yet. When you have learned some arithmetic and
showed me you know how to do that, I will show you some algebra."
What does this say about the student?
What does this say about the teacher?
2 words come to mind: stubborness and laziness.

PD