Neutrinos: Balancing the Astronomical with the Subatomic

Neutrinos: Balancing the Astronomical with the Subatomic

In the climax of Disney’s Enchanted, Queen Narissa in dragon form balances precariously on the top of New York City’s Woolworth Building, gloating about her imminent victory over the story’s heroine and hero. Suddenly, Pip the chipmunk upsets the delicate balance by stepping onto Narissa’s hand and causing the evil queen to plunge to her death, while Giselle the princess rescues her true love from falling to his as well (start at 1:45 into the clip below).

Just as balance is a matter of life-and-death in Enchanted, delicate balance also impacts life in this universe. Researchers seeking to understand the development of the universe found a balance-affecting “chipmunk” of their own, namely neutrinos with mass. Only instead of plunging the universe to its death, these neutrinos ensured balance in the early universe and ultimately made life possible.

After the big bang (the cosmic beginning approximately 13.7 billion years ago), matter and energy were distributed throughout the universe in a very smooth fashion. Only small fluctuations from that smoothness on the order of 1 part in 100,000 existed. Over the next 13 billion years, those small fluctuations grew into the planets, stars, galaxies, and clusters of galaxies that astronomers see as they peer deep into space. Two competing types of processes shaped the celestial structures. First, the universe’s expansion and high temperatures tended to drive the matter and energy apart. Second, the gravitational attraction between the matter and energy drew them together.

If the former process dominates, then all the matter in the universe spreads out before any stars, planets, or galaxies form. If the latter dominates, then only enormous, dense objects like black holes result. The life-essential astronomical bodies (galaxies, stars, planets, moons, etc.) require a delicate balance between these two processes. 

An elusive subatomic particle called the neutrino seems to play an important role in maintaining that balance. The inventory of subatomic particles that an average person can identify includes protons, neutrons, and electrons. Electrons are fundamental particles with a mass around 1,000,000 (in scientifically assigned units). The fundamental particles that comprise protons and neutrons are called quarks and they have masses ranging from 1,000,000 to 200,000,000,000. All of these particles strongly interact and have large masses.

In contrast, neutrinos have masses less than 1 (although scientists have not yet determined the exact mass) and interact very weakly. Given the number of neutrinos produced in the early universe, millions and millions of them stream through your body every second. Yet, even with such a small mass and weak interactions, the vast quantities of neutrinos subtly affect the universe.

A team of British scientists used this weakly interacting effect to constrain the mass of the neutrinos. (Neutrinos come in three kinds with slightly different masses, so the team constrained the sum). The special characteristics of neutrinos give them a unique role throughout the universe. Normally anything with mass would facilitate galaxy formation, but the weak interactions of neutrinos end up contributing to the expansion, rather than to formation. Consequently, on galaxy cluster length scales neutrinos count toward the mass budget but smooth out the matter—the larger the mass, the more the neutrinos’ smoothing effect. Although the effect is small, after a few billion years, it produces a detectable signature. The research team used a survey of 700,000 galaxies with measured redshifts to determine what range of neutrino masses was consistent with the observed clustering. They found that the sum of neutrino masses was less than 0.28.1

This number means that the formation of something like Earth becomes possible. However, the research uncovered more details in an increasingly complex picture of how the universe unfolded. In order for galaxies, stars, and planets to form, the mass of the universe and expansion rate must balance precisely. That mass, of which neutrinos make up a part, shows fine-tuning. Along with the amount and kind of dark matter and the amount of dark energy, the number and mass of neutrinos must meet exacting criteria or the universe ends up uninhabitable.

Thus, these difficult-to-detect “chipmunks” that seem to escape our notice prove to be extremely important in the delicate balance of cosmic forces working to either pull apart or attract matter and energy. This scenario comports well with the Christian idea that a super-intelligent Designer fashioned the universe with a specific purpose, namely for humanity to have a place to live.

  1. Shaun A. Thomas, Filipe B. Abdalla, and Ofer Lahav, “Upper Bound of 0.28 eV on Neutrino Masses from the Largest Photometric Redshift Survey,” Physical Review Letters 105 (July 16, 2010): 031301.