When the Universe was still in its infancy, nuclei such as helium and hydrogen isotopes began to form. Our current knowledge about this process — the so-called primordial nucleosynthesis — is limited, as the scattering off this particle ‘soup’ meant that the Universe was opaque to electromagnetic radiation. By comparing theoretical predictions with the measured abundance of the nuclei created, we can challenge our understanding of the early Universe. But are there no other ways to look back into the past?
Alexandre Ivanchik and Vlad Yurchenko think that we might be able to learn something from the contribution of neutron and tritium nuclear decays to the cosmic neutrino background. They have predicted that these decays are the only source contributing to the spectrum for antineutrinos within a certain energy range. And as the cosmic neutrino background was formed prior to the nucleosynthesis, an experimental observation of these antineutrinos would allow us to witness the creation of the first light elements.
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Reichert, S. Greetings from the past Universe. Nature Phys 14, 1071 (2018). https://doi.org/10.1038/s41567-018-0353-z