Measuring helium in distant galaxies may give physicists insight into why the universe exists

• When theoretical physicists like myself say that we’re studying why the universe exists, we sound like philosophers.
• But new data collected by researchers using Japan’s Subaru telescope has revealed insights into that very question.
• The Big Bang kick-started the universe as we know it 13.8 billion years ago.

After the Big Bang

• In the first milliseconds after the Big Bang, the universe was hot, dense and full of elementary particles like protons, neutrons and electrons swimming around in a plasma.
• Physicists believe that just one second after the Big Bang, the nuclei of light elements like hydrogen and helium began to form.
• This process is known as Big Bang Nucleosynthesis.
• Because the nuclei formed during Big Bang Nucleosynthesis can still be observed today, scientists can infer how many neutrinos and antineutrinos were present during the early universe.

A clue in helium

• Using a technique that allows researchers to distinguish different elements from one another based on the wavelengths of light observed in the telescope, the Subaru scientists determined exactly how much helium exists in each of these 10 galaxies.
• Importantly, they found less helium than the previously accepted theory predicted.
• With this new result, my collaborators and I worked backward to find the number of neutrinos and antineutrinos necessary to produce the helium abundance found in the data.

What does it all mean?

• The Subaru data points us directly to a source for that imbalance: neutrinos.
• Through known and likely particle physics processes, the asymmetry in the neutrinos could propagate into an asymmetry in all matter.
• So, are these tiny little neutrinos the key to answering the age old question, “Why does anything exist?” According to this new research, they just might be.