the universe - what you see is not all you get!

Nebula N81 in the Small Magellanic Cloud, a galaxy near to ours (NASA).

Go outside on a clear night and look at the stars - and you see one of the most beautiful and amazing sights. But of course we can only see an infinitessimal fraction of what is "out there".

We cannot even see all the planets in our own solar system with the naked eye. And our sun is only one of an estimated 100-500 billion stars in our galaxy. (We can only see a few thousand of these, most of them stretching across the sky in the milky way, which is our view of the major part of our galaxy.) And our galaxy is considered to be only one of possibly more than 100 billion galaxies.

But it doesn't stop there. Scientists estimate that stars form only 1% of the combined matter and energy of the universe. Gas and dust and stuff make up perhaps another 4%, and the rest is mysterious "dark matter" (25%), which we can't see because it doesn't reflect or emit light, and don't know what it is, and even more mysterious "dark energy" (70%). It seems most likely that dark matter is made up of quite different particles from those which comprise the matter we are familiar with.

So if we can't see it, how do we know it's there? Its effects can be observed in two ways:

• Even though we can't see dark matter, it has effects that can be measured, like gravitaional influence on the motion of stars and even the rotational motion of galaxies.
• The universe has expanded since the big bang, and the speed of that expansion, in the past and now, can only be explained by the presence of dark matter (which slows down the expansion) and dark energy (which speeds it up).

What can we say? It's fascinating but a little beyond my comprehension. If God created the universe, it was an amazing conception. If it occurred naturally, perhaps even by accident, that is even more amazing.

Read more about dark matter and dark energy from NASA, and from Wikipedia (dark matter and dark energy).