Why did the universe start with just hydrogen and helium?
Big Bang nucleosynthesis
Why did the universe start with just hydrogen and helium?
Imagine baking a cake with just flour, sugar, and eggs; you can't make anything fancy without more ingredients.
In the early universe, it was like a cosmic kitchen with just hydrogen and helium. These ingredients were all that was around to start forming new elements. Big Bang nucleosynthesis (BBN) explains how this happened in just a few minutes after the universe began.
Example
If you start with flour (hydrogen) and sugar (helium), you can't bake a chocolate cake (lithium) without adding more ingredients (elements heavier than lithium).
Remember this
Big Bang nucleosynthesis (BBN) is the cosmic recipe that explains how hydrogen, helium, and traces of lithium were formed in the first few minutes of the universe.
Text adapted from Wikipedia, licensed under CC BY-SA 4.0.
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