When we talk about the first 30 minutes of time, we describe the universe expanding and cooling. As the universe cooled, the nuclear reactions that produced the first atomic nuclei slowed and stopped.

But it was only relatively cool.

The universe still held a temperature on the order of 1 billion kelvins–and that, by the way, converts to roughly 999,999,727°C, or 1,800,000,000ºF.

Ridiculous temperatures like those mean that the gases of the early universe must have been totally ionized. That is, electrons were not bound to atomic nuclei, and no atoms existed.

So how did we get to the universe we know today–a universe full of stars and galaxies?

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