In the first minutes of the Big Bang, the universe whipped up a cocktail of hydrogen, helium, and a pinch of lithium. But the recipe went wrong: according to calculations by George Gamow, Ralph Alpher, and Fred Hoyle, there should be three times more lithium than astronomers see. This mismatch has defied resolution for decades.
A new study proposes two invisible chefs. The first particle, heavy, decays seconds to hours after the blast, releasing neutrinos. These neutrinos turn some protons into neutrons, slashing lithium output but overdoing it on deuterium — heavy hydrogen whose quantity is precisely measured from the light of distant clouds. Then the second particle steps in, a light one that lives more than a day. It decays into photons, and this light neatly breaks apart the excess deuterium without touching lithium. The result: both elements fall into the observed corridor. This precise dance of decays shows for the first time that the lithium puzzle can be solved without harming deuterium.
If lithium were born as calculated, every liter of water would contain enough to power thousands of batteries. In reality, there's three times less.