🚀 go-pugleaf

> In article <514@x.UUCP> john@x.UUCP (John Woods) writes:
> >> 
> >Well, not quite.  It is, in fact, a tad warmer in the rough direction of
> >Saggitarius, which is therefore the center.  The difference is extremely
> >small, so it took some time to detect it.
> 
> Well, Saggitarius is the direction of the centre of the Milky Way
> galaxy; I`m just a poor innocent philosopher, but that seems like quite
> a coincidence to me (i.e. that we just happen to be at the point in our
> orbit around galactic downtown at which the centre and the Universe's
> own central point are in the same direction.
> 
> On the other hand, that it is a big coincidence doesn't mean it can`t be
> a coincidence.  But doesn't the universe having an observable centre
> screw up some cosmological stuff that works well otherwise?
> 
> 			Charlie Martin

OK folks.  Allow me summarize the current state of affairs.  The blackbody
background of the universe, which is detectable in the microwave region,
is isotropic to a high degree of accuracy.   The only exception to this
is a weak dipole moment (of order 10^-3).  All higher order anisotropies
are down from this by *at least* an order of magnitude.  This dipole moment
has a straightforward interpretation.  It is exactly what one would
expect if the observer (that's us) were moving at a few hundred kilometers
a second with respect to the microwave background.

The direction of motion of the sun is toward RA 11.4, dec 5 degrees.  The
velocity is about 400 km/sec.  The galactic center is at RA 12.8, dec 27.5
degrees.  In other words, they are not in the same direction.  The motion
of the sun is presumed to have the following components

                 motion with respect to the local standard of rest
  [ This is approximately our motion with respect to the motion of stars
    at the same distance from the galactic center and orbiting in perfect
    circles.]

                 rotation of the galaxy
                 motion of our galaxy within the local group
                 motion of the local group within the Virgo Supercluster
                 motion of the supercluster due to nearby superclusters

If we correct for the motion of the sun relative to the local group of
galaxies we find a residual motion of about 550 km/sec toward galactic
coordinates longitude = 265 degrees, b=35 degrees.  Although our motion
within the local supercluster is not entirely certain there is evidence
that our average motion with respect to galaxies at a distance of 50 Mpc h^-1
is the same as that observed in the microwave background.  In other words,
the frame of reference in which the galaxies are, on the average, motionless
is the same as the one in which the microwave background is isotropic.

This is taken as evidence that the universe is homogeneous and isotropic,
which is to say that it has no center.

Of course, this is science.  I have been privately assured that the center
of the universe is well known to be in Texas somewhere.


"Don't argue with a fool.      Ethan Vishniac
 Borrow his money."            {charm,ut-sally,ut-ngp,noao}!utastro!ethan
                               Department of Astronomy
                               University of Texas
-- 

"Don't argue with a fool.      Ethan Vishniac
 Borrow his money."            {charm,ut-sally,ut-ngp,noao}!utastro!ethan
                               Department of Astronomy
                               University of Texas