Scientists recreated the nuclear reaction that occurred immediately after the Big Bang

From Popular Mechanics

• The researchers solved a key variable in a reaction that occurred very soon after the Big Bang.
• By detonating protons in a deuterium cloud, scientists simulated how the first elements joined together to form a helium isotope.
• The calculated proton collection rate maps to a later measurement and offers scientists new tools to continue the study.

In a research laboratory deep in a mountain in Italy, scientists made a new measurement of a nuclear reaction that immediately followed the Big Bang.

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By recreating conditions with more sophisticated materials and tools than ever, scientists say they have made the most faithful simulation of this nuclear reaction, which also matches our understanding of what happened next.

In Nature, the researchers explain their experiment:

“The light elements were produced in the first minutes of the Universe through a sequence of nuclear reactions known as the Big Bang nucleosynthesis (BBN). We bombarded a high purity deuterium gas target with an intense proton beam and detected γ rays from the nuclear reaction. Our experimental results establish the most uncertain input of nuclear physics for BBN calculations and substantially improve the reliability of the use of primordial abundances to probe the physics of the early Universe. ”

The researchers used “period-corrected” deuterium – one of the very first compounds formed after the Big Bang – and a very specific laser to measure how fast deuterium, in turn, joined to become helium-3. By blasting a deuterium cloud with a proton beam, scientists can directly observe how a proton joins the deuterium nucleus to form helium-3.

This particular reaction is the key to understanding our very, very young universe. And scientists have relied on extremely plausible assumptions, because they never understood a fundamental part of this reaction. How easy is it to get the deuterium to even grab the proton in the first place? How fast do deuterium molecules absorb protons to become helium-3?

“The most important thing”, Thomas Lewton a How much explains, “Uncertainty prevented physicists from comparing that image to the appearance of the cosmos 380,000 years later, when the universe cooled enough for electrons to start orbiting atomic nuclei.”

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This means that the scientists’ experiment had a very simple pass-fail test for its results. After detonating deuterium gas with protons and measuring the resulting amount of helium, they had to link that value to existing and more concretely understood numbers for background radiation and other factors 380,000 years later. And, thankfully, their value fills the equation well.

The search also has a ripple effect, like solving the first equation in a system and then using the found value to replace it with the others. In this case, knowing the absorption rate of the deuterium proton leads to a better understanding of the countless subsequent chemical processes.

“Our experimental results solve nuclear physics’ most uncertain input for BBN calculations and substantially improve the reliability of using primordial abundances to probe early Universe physics,” the researchers conclude.

A large missing piece has been identified and is very similar in shape to helium-3.

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