For nearly two decades astrophysicists have been converging on what is now referred to as the concordance model. In this model based on solid observations and theory, we live in an expanding Universe with expansion initiated in the Big Bang. However, there’s more to it. There is not only the normal matter that makes up stars, planets, and people, but also dark matter . Dark matter is so named because it doesn’t show itself by emitting or reflecting light, but is only revealed by its gravitational effects on other matter. We do not yet know what dark matter really is though the best bet is that it’s some form of elementary particle or particles that have yet been discovered. Alternatively, some astrophyiscists feel that there is no real need to appeal to dark matter. That is the same observations that could be explained by  dark matter could potentially also be explained by the force of gravity itself acting differently on large scales (millions of light years and greater)  than it does on scales of a fraction of a light year.  In such a theory you would only need normal matter acting differently.

Dark matter has made its way into science fiction over the years. In S.W. Ahmed’s novel, Dark Matter,  dark matter is an illusion developed by alien races to hide their vast colonies in the Galaxy from undeveloped planets such as our own. In Star Trek: the Next Generation, the Enterprise encounters a dark matter nebula. Neither is a particularly realistic instance of dark matter. In the first case, it’s hard to hide all of the forms of radiation  a Galactic colony would produce. In the second case, it could exist, but wouldn’t have any significant appearance to the eye as would a normal nebula.

And don’t forget The Physics and Astronomy of Science Fiction by Steven D.Bloom where you can read more about dark matter and much more.It makes a great Christmas or Hannukah gift.