Deuterium, the first element in the Universe
Consisting of a proton and a neutron, deuterium is the first element in the universe to form and thereby the most important. In this student friendly talk I will discuss how the tiny fraction of deuterium that is left over from the Big Bang nucleosynthesis can tell us about the conditions when it formed. I will also demonstrate two new high-precision measurements of the deuterium abundance in high-redshift gas clouds. The increased precision calls for improved theoretical nucleosynthesis predictions. For that I present an updated version of the public AlterBBN code including new reactions, updated rates, and the possibility of adding new physics such as dark matter.