Today's publication of Quanta Magazine:
In a secluded laboratory buried under a mountain in Italy, physicists have re-created a nuclear reaction that happened between two and three minutes after the Big Bang.
The reaction involves deuterium, a form of hydrogen consisting of one proton and one neutron that fused within the cosmos’s first three minutes. Most of the deuterium quickly fused into heavier, stabler elements like helium and lithium.
Their measurement of the reaction rate, published today in Nature, nails down the most uncertain factor in a sequence of steps known as Big Bang nucleosynthesis that forged the universe’s first atomic nuclei.