By Nikita Chanda
Like a little boy stealing bread from the grocery store, I am just trying to survive. Everyday, I face a battle within me. It is so tiring. Inside me, protons infest my body. The heat of my existence rips them apart from their homes, their nucleus. My maternal instinct to bring them together again overcomes me and my will to live. I am incapacitated by the lethal chokehold which is my inability to fix this. A being named Coulomb forces my protons apart from each other when they get too close. It hurts so much I wish I could make it disappear, but no matter how many times I search, Coulomb is invisible to the naked eye.
I have made futile attempts to force my protons together to find peace. I had come to the realization that the pressure from my stress allows protons to be near each other, so I put myself under extreme pressure to fulfill this goal. Alas, the protons would never stay in the same home. But in spite of that, I was able to seek refuge. There is this magical property within me that I have observed. You see, Coulomb, or the repulsion between my protons, creates a barrier that prevents them from being together– but by a miracle, my protons can tunnel through those barriers.
One may wonder, how does this let me shine? Shine, I feel, is a terrible choice of word. I don’t shine. I flame. I ignite with anger, with heat, because all my efforts are for naught. As it turns out, when my protons come together they don’t come together. They fuse. Their fusion blazes an eternal fire inside of me that I can never escape from. Shine? No. My “shine” is simply excessive amounts of energy in the form of heat and light. I am a smoldering entity struggling to endure the blazing fire kindling inside of me.
Quantum Tunneling in the Sun
The quantum mechanical phenomenon of protons tunneling through barriers to fuse together is called quantum tunneling.
Imagine dropping a ball down a curved hill. The ball goes down and up the hill, but then drops to its initial position. It doesn’t go over the top because you didn’t give it enough energy to do so. How can you make it go to the other side? Give it more energy. But, what if you can’t? Enter in: quantum mechanics. In the quantum realm, that ball can tunnel through the hill (Libretexts).
In quantum mechanics, a particle is described using a wavefunction, which tells us the particle’s momentum and position. A wavefunction squared gives the probability of a particle being at a given position during a given time, or its probability distribution (Orzel).
Due to the Heisenberg Uncertainty Principle, there is always some level of uncertainty as to where a particle is. This means that there is never a probability of 0 or 1. So, if we come across a barrier where it is virtually impossible for the particle to exist, the particle’s probability distribution rapidly decreases toward zero– meaning, there may be an extremely low probability, but it is still possible (Orzel).
What does this mean? Consider two positively-charged particles that would normally repel each other because of Coulomb’s force (Ash). In this case, the forbidden region where the proton’s wavefunction decreases exponentially is when the proton gets close to another proton, and the other side of this barrier shows the probability of them fusing together (Orzel). Like tunneling through a hill, the protons in the sun can essentially teleport to being fused together.
The probability distribution of a particle coming in from the left, hitting a barrier where the potential energy of the particle would increase above the total energy of the particle. The probability drops off rapidly in this region but does not reach zero, so there is a probability of seeing the particle to the right of the barrier. If it did tunnel, it would have the exact same amount of energy as it did to the left of the barrier (Orzel).
Now, it is clear how quantum tunneling exists inside the sun. But why do these protons have to fuse?
The sun is fueled by nuclear reactions that fuse H+ atoms together into helium. Fusion is not like bonding; it is the process of converting one element into another by changing an atom’s number of protons, releasing extreme amounts of energy. This phenomenon only occurs in environments with gigantic temperatures and pressures– like in the center of a star (Ash). When these protons fuse, one of them releases a positron(e+) and a neutrino(Ve), allowing the proton to act like a neutron. This creates an isotope of hydrogen, called deuterium. The deuterium nuclei then either merge to form helium nuclei or link with other protons to create another helium isotope (Ash). From here, these helium nuclei can fuse to make a beryllium isotope. Finally, the beryllium isotope releases two of its protons, resulting in helium. At each step of the way, huge amounts of energy are released in the form of both heat and sunlight (Ash).
This is what makes the sun, our source of life, shine.
The Heisenberg Uncertainty Principle
It is impossible to know both the position and momentum of a particle. Essentially, unlike the classical world we’re used to, the quantum realm is probabilistic as there will always be some level of uncertainty.
References
Orzel, Chad. How to Teach Quantum Physics to Your Dog. Scribner, 2010.
Ash, Arvin. “Why Does the Sun Shine? The Quantum Explanation for How the Sun Works”. YouTube, 17 Apr. 2021, https://www.youtube.com/watch?v=xR88vSiOvY4.
Libretexts. “4.9: Quantum-Mechanical Tunneling.” Chemistry LibreTexts, Libretexts, 17 July 2020, https://chem.libretexts.org/Courses/University_of_California_Davis/UCD_Chem_1 07B%3A_Physical_Chemistry_for_Life_Scientists/Chapters/4%3A_Quantum_Theory/4.09%3A_Quantum-Mechanical_Tunneling.
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