If the universe is 13.8 billion today, but different ages the more we look back, what does it mean that a star is the first?
June 13, 2025
In our physical universe, there is always an order in which things happen. The sun, the earth and the rest of our solar system were formed at a particular time: about 4.5 billion years ago, right here in our own Milky Way. However, when we look at our sun in detail, we find that it contains a large percentage of heavy elements: approximately 1–2% of the sun consists of elements that could only have been forged in previous generations of stars. Our universe, however, is an impressive 13.8 billion years: completely three times older than the Sun. If we could rewind the clock closer to the start of the Hot Big Bang, we would find that the stars existed most of the time, but they were more pristines, less evolved and contained less heavier elements.
At some point, in this imaginary setback, we would find something remarkable: the first stars of all that are formed in cosmic history. If we had to return before that, we would not find stars at all, only neutral atoms and before that, even more states of primitive matter. But what would you find the first stars …
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