Statistical Mechanics and The Probability of the Universe

Act I: A Tragic Hero

In my third year of college I took a class called Kinetics and BioTransport. We learned about how medication interacts with our bodies, both physically and chemically. On the third day of class, our professor drew two large circles on the whiteboard.

“Why do you think drug efficacy varies so much between people, or even on the same person at different time points?” she asked, her cat-eyed, only-female-professor-in-the-department glasses glinting at us.

“Human physiology is orders of magnitude more complex than simplified drug trials. There are too many things a drug can interact with, so each time something different happens,” Gina* raised her hand and answered before the professor called on her. My friends and I hated Gina then. In reality Gina is lovely, regularly baked for our cohort, and now studies medicine.

“That’s right. But why is there uncertainty at all? Even if a system was complex to the nth degree, we could model it computationally. Yet we can’t accurately model molecular interactions in the body.”

A silent room full of junior biomedical engineering students usually meant we were sleeping at our desks, too tired to process anything. But there had been no twelve-hour homework assignments due that day, no medical device proposals or coding challenges to keep us up the night before.

Our professor had a look in her eyes, like she was about to tell us something big. She drew two large semicircles connected by a tube on the whiteboard.

“When particles enter the right semicircle, what happens?”

“They diffuse evenly to the other semicircle,” my voice cracked when I spoke. Our professor was my thesis advisor, so I was obligated to answer.

“Always?”

Yes, always. Osmosis. Diffusion. It’s what we learn in introductory physics or chemistry. Like adding food dye to water, particles spread out until they are evenly distributed throughout a medium. No one said anything though-- too frightened of being wrong to risk being right.

“Okay, why do particles evenly spread in a space? Why does our body and molecules in it seek homeostasis?” our professor asked. The class remained silent. In other classes we learned that molecules seek balance-- something about chemical properties and charge repulsion. At that moment it didn’t seem like enough.

“It’s because of probabilities.” Our professor is fully smiling at this point.

“Diffusion happens because particles are always moving randomly, and over time the most likely distribution is an even one. There’s no “reason” behind diffusion, it’s just the most likely arrangement of particles over time.”

The reaction in the classroom was instantaneous. Eyebrows were furrowed, mouths were gaped, and one student mumbled a quick “I have to go to the bathroom,” and limped out of the off-white classroom.

Act II: Hamartia

If you’re confused, well, I was too. My professor was implying that particles, aka the things that make up EVERYTHING, didn’t arrange themselves off of the scientific rules drilled into us as engineers. No, she was suggesting that scientific understanding of the world came down to likelihoods.

For example, you could bang your hand against a table a billion times. And a billion times your hand will hit the table and you’ll curse and wonder why you hit your hand. But during one attempt, your hand might pass through the table. This contradicts basic physics, and made all of us uncomfortable.

Blinking into the sunlight after class, I grabbed tea from my dorm room and headed to the Center for Engineering Innovation and Design. We called it the CEID (pronounced “seed”). A few wikipedia searches revealed that statistical mechanics is legit. Like, Einstein-Fermi-Boltzmann legit. And that everything-- the rules of physics, chemistry, biology, etc. -- are only conditions that influence the probability that something happens.

This made me very unhappy.

Studying science is like learning magic. If you put two elements together poof you have bronze, or plastic, or a smartphone. It gives us a semblance of control over the chaotic universe, a sense of self-determination hard to find elsewhere. When I started studying biomedical engineering, I thought I was learning how the universe worked-- how to construct and deconstruct the most mystical thing that existed, our own bodies.

But statistical mechanics threw a wrench into that. Statistical mechanics posits that evidence-based science is rooted in chance. Instead of gaining more control, I lose some.

I struggled to work for the rest of the week. I met with my professor and told her that learning statistical mechanics made me feel detached from my academic work. She laughed.

“Keep thinking about it. And your work. I think you’ll find that it’s actually more interesting now.”

Act III: The Dichotomy of Good and Evil

When Austrian physicist Ludwig Boltzmann first proposed that entropy was a collection of probabilistic microstates, the scientific community was baffled. Now, we use quantum computing to take advantage of these fluctuating probabilities.

Unlike the scientific community in the past two centuries, I do not embrace uncertainty. I eat the same thing for lunch on weekdays. I show up to coffee on time. I reread books.

The following semester I worked on my thesis. I wrote an algorithm to parse out protein trajectories in HIV infected and uninfected cells and compared them. And when unaccountable fluctuations showed up in the data, my professor and advisor brought up statistical mechanic techniques.

I resisted, to the best of my ability. Adding “random error” techniques felt like a copout. But I reached end of my rope. I added an error term with a Boltzmann constant, and suddenly everything worked.

My feelings were mixed when I presented my thesis. Months later I learned that my work was being used in further HIV studies.

I'm still uncomfortable with statistical mechanics. It confirms that there are no answers in life, something I hoped to find in the religion of science. To deny statistical mechanics is to ignore that life is random, spontaneous, and confusing. If we accept those uncertainties, we can use them to our advantage, like some high-tech quantum computer. Otherwise, we’ll submit a sub-par thesis that gets recycled before it's ever truly read. Maybe this is an answer in itself. Who knows, I'm only 24.