Aallegra.338
net.space
utcsrgv!utzoo!decvax!ucbvax!npois!harpo!mhtsa!allegra!green
Wed Mar 31 20:52:12 1982
Cosmic Microwave Anisotropy
Today I heard a colloquium by Ed Cheng, a member of the Princeton
group that has measured the anisotropy of the cosmic microwave background.
The results so far can be summarized as follows:
Three groups, Berkeley, Princeton, and Florence, have measured
a dipole moment in the background. All three agree on this measurement.
Of these groups, the first two have measurements covering enough of
the sky to report on the quadrupole moment. These two groups disagree
significantly on the quadropole moment. The difficulty in the quadrupole
moment lies in the contribution of the galaxy. (The galaxy does not
affect the dipole measurements because the dipole effect is relatively
large and because the galaxy as viewed from here has little dipole moment).
Errors in how the contribution of the galaxy are handled could explain
the measured quadrupole moment. The final word on whether there is
a quadrupole moment awaits more sensitive experiments.
Leaving Ed's talk, I would like to comment on the fact that
the microwave radiation does not establish an absolute or preferred
rest frame, any more than does the earth or the sun or the galaxy.
It is merely the rest frame of a larger object than any other object
we have measured.
Jim Green
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