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The evolution of the Universe

We’re not really going into the evolution of the Universe. But I couldn’t resist this picture from Scientific American (Jan 05).

At the top of the diagram is the young Universe, of more than 10½ thousand million years ago. The Universe was much smaller and denser then. It was populated with gigantic diffuse galaxies, without any hint of the spiral structure that we are used to seeing in most galaxies around today. These huge galaxies were forever bumping into each other, and the collisions triggered unbelievably intense bursts of star formation.

The early galaxies and their stars lived their lives in the fast lane, and did not last very long. They collapsed into supermassive Black Holes, producing the most spectacular firework displays of all time.

We can still see the displays today; although the ones that we see were a truly incredible distance away at the time. We get into trouble if we start trying to work out distances, because the Universe has expanded 5-fold (I think!) in the interim. But the light from them has been travelling for over ten thousand million years (10,000,000,000) to reach us.

As time passed, the Universe expanded. It spawned smaller galaxies with smaller and longer-lasting stars. The galaxies themselves lasted long enough to form the spiral structure that we are used to seeing.

I think astronomers reckon that our galaxy was formed about 10 thousand million years ago.