What is known about the origins of galaxies?

On Wed, 5 May 1999 you wrote:

> What is known about the origins of galaxies?

The origins of galaxies are not very well known. There are two main
camps that believe they know how galaxies formed. One group of
astronomers believes that, when the universe was young, giant clouds of
gas broke up into smaller clouds. The small clouds became galaxies,
breaking up further to form stars. Because these galaxies formed from
larger clouds, they would tend to be grouped together in the sky. Also,
all sizes of galaxies should have been present from the beginning of the
universe through today.

The other group of astronomers believe that galaxies formed when many
small clouds fell together under gravity and merged to make larger clouds
that became galaxies. In this view, gravity would eventually cause big
galaxies to form, and even groups and clusters of galaxies, but in the
past galaxies should have been smaller than today.

To date, both theories fit what astronomers can observe, although many
theorist's favorite computer models show that galaxies should start small
and build up. It is really only by looking at the most distant galaxies
that we can hope to figure out how galaxies really form. Astronomers are
finally starting to be able to see distant galaxies, but it is hard work
and filled with many pitfalls and uncertainties. It will still be
several years until we truly understand how galaxies form.

Thanks for writing!

Sincerely,
Kurtis Williams

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