WHAT’S SO SMALL TO YOU IS SO LARGE TO ME

Among the many reasons I chose to pursue physics was the desire to do something that would have a permanent impact. If I was going to invest so much time, energy, and commitment, I wanted it to be for something with a claim to longevity and truth. Like most people, I thought of scientific advances as ideas that stand the test of time.

My friend Anna Christina Büchmann studied English in college while I majored in physics. Ironically, she studied literature for the same reason that drew me to math and science. She loved the way an insightful story lasts for centuries. When discussing Henry Fielding’s novel Tom Jones with her many years later, I learned that the edition I had read and thoroughly enjoyed was the one she helped annotate when she was in graduate school.

Tom Jones was published 250 years ago, yet its themes and wit resonate to this day. During my ?rst visit to Japan, I read the far older Tale of Genji and marveled at its characters’ immediacy too, despite the thousand years that have elapsed since Murasaki Shikibu wrote about them. Homer created Odyssey roughly 2,000 years earlier. Yet notwithstanding its very different age and context, we continue to relish the tale of Odysseus’s journey and its timeless descriptions of human nature.

Scientists rarely read such old — let alone ancient — scientific texts. We usually leave that to historians and literary critics. We nonetheless apply the knowledge that has been acquired over time, whether from Newton in the 17th century or Copernicus more than 100 years earlier still. We might neglect the books themselves, but we are careful to preserve the important ideas they may contain.

Science certainly is not the static statement of universal laws we all hear about in elementary school. Nor is it a set of arbitrary rules. Science is an evolving body of knowledge. Many of the ideas we are currently investigating will prove to be wrong or incomplete. Scienti?c descriptions certainly change as we cross the boundaries that circumscribe what we know and venture into more remote territory where we can glimpse hints of the deeper truths beyond.

The paradox scientists have to contend with is that while aiming for permanence, we often investigate ideas that experimental data or better understanding will force us to modify or discard. The sound core of knowledge that has been tested and relied on is always surrounded by an amorphous boundary of uncertainties that are the domain of current research. The ideas and suggestions that excite us today will soon be forgotten if they are invalidated by more persuasive or comprehensive experimental work tomorrow.

When the 2008 Republican presidential candidate Mike Huckabee sided with religion over science — in part because scientific “beliefs” change whereas Christians take as their authority an eternal, unchanging God — he was not entirely misguided, at least in his characterization. The universe evolves and so does our scientific knowledge of it. Over time, scientists peel away layers of reality to expose what lies beneath the surface. We broaden and enrich our understanding as we probe increasingly remote scales. Knowledge advances and the unexplored region recedes when we reach these difficult-to-access distances. Scientific “beliefs” then evolve in accordance with our expanded knowledge.

Nonetheless, even when improved technology makes a broader range of observations possible, we don’t necessarily just abandon the theories that made successful predictions for the distances and energies, or speeds and densities, that were accessible in the past. Scientific theories grow and expand to absorb increased knowledge, while retaining the reliable parts of ideas that came before. Science thereby incorporates old established knowledge into the more comprehensive picture that emerges from a broader range of experimental and theoretical observations. Such changes don’t necessarily mean the old rules are wrong, but they can mean, for example, that those rules no longer apply on smaller scales where new components have been revealed. Knowledge can thereby embrace old ideas yet expand over time, even though very likely more will always remain to be explored. Just as travel can be compelling — even if you will never visit every place on the planet (never mind the cosmos) — increasing our understanding of matter and of the universe enriches our existence. The remaining unknowns serve to inspire further investigations.

My own research ?eld of particle physics investigates increasingly smaller distances in order to study successively tinier components of matter. Current experimental and theoretical research attempt to expose what matter conceals — that which is embedded ever deeper inside. But despite the often-heard analogy, matter is not simply like a Russian matryoshka doll, with similar elements replicated at successively smaller scales. What makes investigating increasingly minuscule distances interesting is that the rules can change as we reach new domains. New forces and interactions might appear at those scales whose impact was too tiny to detect at the larger distances previously investigated.

The notion of scale, which tells physicists the range of sizes or energies that are relevant for any particular investigation, is critical to the understanding of scientific progress — as well as to many other aspects of the world around us. By partitioning the universe into different comprehensible sizes, we learn that the laws of physics that work best aren’t necessarily the same for all processes. We have to relate concepts that apply better on one scale to those more useful at another. Categorizing in this way lets us incorporate everything we know into a consistent picture while allowing for radical changes in descriptions at different lengths.

In this chapter, we’ll see how partitioning by scale — whichever scale is relevant — helps clarify our thinking — both scientific and otherwise — and why the subtle properties of the building blocks of matter are so hard to notice at the distances we encounter in our everyday lives. In doing so, this chapter also elaborates on the meaning of “right” and “wrong” in science, and why even apparently radical discoveries don’t necessarily force dramatic changes on the scales with which we are already familiar.

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