A theoretical astrophysicist by training, Ethan Siegel took the unconventional path of ditching research to become full-time science communicator.
Ethan Siegel has always been amazed by the human capacity to figure out scientific answers to even the deepest questions about physical reality. He believes this universe is the one thing we all have in common, and that knowing our shared cosmic story should be for everyone.
He spoke with FirstPrinciples about how and why he does it.
FirstPrinciples: What compels you to tackle fundamental questions for which the answers are so elusive?
Ethan Siegel: If you're a curious human, which I happen to be, you probably can't help yourself from asking new questions about what's next whenever you learn something new. When you learn that molecules make up matter, you instantly begin wondering about what composes molecules. When you learn about the atom, your attention shifts to subatomic particles. And when you learn about the interior of protons and neutrons, you then begin asking about the Standard Model and what lies beyond.
Similar questions arise on cosmic scales: where did stars, galaxies, and even the entire universe arise from, and how did things get to be the way they are today?
I'm constantly in awe of all that we've learned and all the questions that we can answer today, but each time we peel back the curtain of ignorance to reveal something novel, it always raises more questions.
So long as curiosity remains an inherent part of the human experience, I doubt we'll ever run out of fresh nourishment as far as seeking the answers to fundamental questions is concerned.
FP: Why do you focus specifically on your field?
ES: My specific field is physical cosmology: questions like how the universe began, how it evolved to be the way it is today, and what its ultimate fate is.
For nearly all of human history, big, existential questions such as these were beyond the realm of what science could answer or even address, and fell to philosophers, theologians, and even poets to consider. No longer!
Since the dawn of the 20th century, these have become questions whose answers can be revealed scientifically: through observation, measurement, experiment, and within the theoretical framework of our understanding of fundamental physics. When we talk about big ideas like the expanding Universe, the hot big bang, or cosmic inflation, these aren't just theoretical ideas that we consider; these are profound conceptions of our very existence that lead to testable predictions and observable features within our universe. The idea that we can answer the biggest questions of all by examining the universe we have access to is an idea that I feel compelled to pursue to its fullest — and thankfully that compulsion isn't unique to me.
FP: What do you find most surprising or amazing about our universe?
ES: The most amazing fact, to me, is one that most people take for granted: the fact that the universe can be understood at all in scientific terms.
The fundamental laws of nature do not change over time, nor from location-to-location in space. Nor do the values of the fundamental constants, which remain constant under all tests we've been able to perform. You can imagine a chaotic universe — one where the force of gravity changes from moment to moment, becoming stronger, weaker, or even reversing sign.
In such a universe, stable stellar systems and galaxies would be an impossibility, much less living creatures and intelligent beings. Yet, our universe is not only regular and ordered, obeying the same rules at all times and in all places, but can be understood and even predicted once we've advanced enough to understand what those rules are. If it were any other way, the universe would not be comprehensible in a scientific sense.
But the fact that we can understand the universe, despite our limitations as human beings, remains the most amazing fact of all.
What keeps you up at night?
ES: When I was a child, the existential threat hanging over humanity was that of nuclear war. Growing up in the late 20th century, we were well aware of the power of atomic bombs and were taught that, between the United States and the Soviet Union alone, there were enough bombs to destroy not only all of humanity at once, but much of the natural world as well. Today, the threat to humanity not only comes from our ability to do direct violence to one another, but indirectly: through the destruction of our planet's natural ecological habitat.
I envision the possibility of a successful, long-term future where we continue to invest in basic, fundamental research and to push the frontiers of knowledge forward, but that vision seems farther away from today's reality than ever.
Will we overcome our worst, most divisive instincts and find it within ourselves to continue to explore and investigate the deepest questions we've been able to formulate as a species? Despite all we've learned about the universe, the questions that keep me up at night aren't external questions about our shared reality; they're questions about ourselves and our capacity for love and compassion even in times of doubt, fear, and uncertainty.
FP: What discovery or advance do you hope to witness (or be part of) in your lifetime?
ES: Everywhere we look in the universe, we see structures: stars, planets, galaxies, quasars, clouds of gas, and much more. But practically all of it is made of matter, and not its equal-and-opposite counterpart: antimatter.
This is one of the greatest unsolved problems in our universe: the origin of the matter-antimatter asymmetry. Understanding why our universe is made of matter and not antimatter, or how there came to be a matter-antimatter asymmetry at all, is a topic that I'm greatly interested in, and one that interests both high-energy particle physicists as well as cosmologists and astrophysicists.
Will we be able to produce a matter-antimatter asymmetry in laboratory settings? Will we be able to explain how our universe came to have roughly one atom (and no anti-atoms) for every 1.5 billion photons? Can we discover the correct mechanism for how this asymmetry not only arose, but survived through the various epochs of cosmic history?
The biggest question of all — "Where did all this come from?" — depends on it.
