During his work with the Mount Wilson reflector,
Hubble also made careful studies of the combined spectra
of the galaxies. These spectra are the result of the com-
bined spectra of millions of stars, and are bound to be
something of a jumble, but the main absorption lines can
be made out, and their Doppler shifts can be measured.
Hubble confirmed earlier work, at the Lowell Observatory
in Arizona, showing that all galaxies apart from a few
which are very close to us (now known to make up what
we call the Local Group) showed red shifts, indicating
that they are moving away from us. Moreover, the further
away they are, the faster they are receding. The entire
universe is expanding. This does not mean that we are in
a privileged position; every group of galaxies is racing
away from every other group.
By now we can observe systems which are thousands
of millions of light-years away, so that we are seeing them
as they used to be thousands of millions of years ago –
long before the Earth or the Sun existed. Once we look
beyond the Solar System, our view of the universe is
bound to be very out of date.
People used to believe that the Earth was all-
important, and lay in the exact centre of the universe with
everything else moving round it. We now know better.
The Earth, the Sun, even the Galaxy are very insignificant
in the universe as a whole. Indeed, the more we find out,
the less important we seem to be.THE UNIVERSE
▲ The Coma cluster of
galaxies: Hubble Space
Telescope, 4 March 1994.
The Coma cluster contains
1000 large galaxies and
thousands of smaller
systems; the mean distance
from us is 300 million
light-years. The largest
galaxy in the cluster,
NGC4881, has a diameter
of 300,000 light-years, three
times that of our Galaxy.▼The spiral galaxy M100,
in the Virgo cluster. The
image was obtained by the
Melipal telescope at the
VLT, using the Visible
Multi-Object Spectrograph
(VIMOS). The pink blobs are
huge clouds of glowing
hydrogen gas.F Atl of Univ Phil'03stp 3/4/03 5:41 pm Page 195