Cosmic Microwave Background
Name: Jack H.
How is it that we can "see" the cosmic microwave background radiation? It seems
to me that, no matter which way its photons were heading when they started on their way in the
year 380,000, they must surely have left the matter of the universe behind by now. They
travel at the speed of light and we do not even come close, (do we?). So why are they
still around here?
Understanding the "Big Bang" is not at all in line with our intuition. It is not as if we are
sitting "over here" on Earth and "it" happened "over there" about 13 billion years ago. Except
for the predicted (and observed) fine structure, it occurred in all directions in space
simultaneously -- it is the very creation of space itself. So our intuition fails us, and must
be disregarded. The experimental observation is that no matter what direction we look into
space, other galaxies are receding from us. From the Doppler
shift in the wavelength(s) of light we are able to tell how far these sources are, and how
fast they are receding from us. The observation is that not only are they moving away from us
(and one another) more recent observations suggest that the furthest (i.e. oldest) sources may
even receding at an increasing rate.
No one (even the experts, not just us poor mortals) has a good explanation for why this is and
so there are tags that we put on the observations "dark matter", "dark energy" etc., but that
is not an explanation, it is a name tag.
The "Universe" the "All" is weird indeed.
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Update: June 2012