Chapter One How to Live Safely in a Science Factual Universe In which we notice that we need metaphors to live (and do science) Before the lab, before the data collection, there is language. Language is sometimes direct and quite literal: "The prettiest rose is a red rose." But it is just as often figurative, working through comparisons that require imagination to comprehend them. To tell you the story of space-time is to use figurative language, most especially the metaphors that so many of us use to understand our everyday lives. Think about how the idea of space-time as a "fabric" has become culturally ubiquitous. Meanwhile, physicists describe electricity and magnetism as "fields." What does it mean to explain abstract ideas by drawing on these comparisons to our lived environments and everyday objects? It would be easy to jump into the science and the metaphors without spending time thinking about what exactly we are doing when we do so. But if we are to think carefully about the fundamental nature of the universe and everything inside of it--from space-time to the invisible dark matter that we''ve never seen or touched but feel fairly confident makes up most of the matter in the universe--then that means thinking carefully about metaphors and what work they are doing in our lives and scientific habits.

As a physicist and science communicator, I live with the weight of the metaphors we choose in science, asking myself almost daily: "Is this the right one? What misunderstandings does this metaphor induce?" I ask these critical questions while also knowing that I am completely dependent on metaphors for my own understanding. We live and breathe the world through metaphor, and our earliest metaphors have the power to govern our thinking. These are the lessons that Natasha Trethewey offers us in her 2020 essay, "You Are Not Safe in Science; You Are Not Safe in History: On Abiding Metaphors and Finding a Calling." In the essay, Trethewey meditates on her upbringing as a child of a white father and Black mother. It is here that I first saw these lines from Robert Frost''s essay "Education by Poetry": What I am pointing out is that unless you are at home in the metaphor, unless you have had your proper poetical education in the metaphor, you are not safe anywhere. Because you are not at ease with figurative values: you don''t know the metaphor in its strength and its weakness. You don''t know how far you may expect to ride it and when it may break down with you. You are not safe in science; you are not safe in history.

The first time I read Frost''s lines in Trethewey''s essay, I actually did a double-take. I was reading this essay for literary craft, not to study science craft. Yet there it was: "You are not safe in science. You are not safe in history." In the essay that follows, the metaphors Trethewey centers are focused on the embodied experience of being a child of miscegenation--a mixed-race marriage between a Black woman and a white man. Trethewey writes of the abiding metaphors that govern how Black children with white biological parents have historically been interpreted both socially and scientifically, i.e., as mules, the English version of the Spanish/Portuguese "mulato.

" Her father believed, as Robert Frost did, that Trethewey had to understand metaphors because they are powerful mediators of the relationship between our internal world and the outer universe. Her mother also believed that an education by metaphor was necessary because "if I could not parse the metaphorical thinking of the time and place into which I''d entered, I could be defeated by it." This is true for a physicist too. The beating heart of physics is creating models of the world because, ultimately, we are searching for mathematical metaphors that give us insight into our cosmos. The models that survive scrutiny become the next generation''s abiding metaphors. Abiding Metaphors How do we learn to think about our universe as it actually is? We start with our abiding metaphors, which shape how we understand our reality. Our childhood stories follow us through life. In my case, like many Black children of the 1980s United States, I was raised on Virginia Hamilton''s short-story collection The People Could Fly: American Black Folktales .

The titular tale, which concludes the collection, opens, "They say the people could fly." It is a story about enslaved Black folks escaping the horrors of enslavement by literally flying away. In reading this story to me, my mom passed on a multigenerational Black metaphor for Black freedom dreams. Because of course the point wasn''t that our African ancestors who were kidnapped and forced to endure the Middle Passage were actually capable of flying. Flight was a metaphor for the freedom that was stolen from them, and it was also a metaphor for the freedom that Black people restored for themselves when they took flight from enslavement, whether by running away or through other means. The People Could Fly is now one of the abiding metaphors of at least one physicist''s upbringing, or training as we might otherwise call it. To be a physicist is to parse not just the metaphorical thinking of the here and now but also to be trained in the metaphors of yesterday, including the ones that tell stories about what we are. To understand the abiding metaphors of her family and her culture, Trethewey''s essay excavates the race science that evolved to explain that people like her (people like me) are a specific kind of abomination.

It''s easy to understand race/racist science as a pseudoscience of the past, but not only does it live with us in the here and now, it was considered mainstream, state-of-the-art biological science right around the time that physicists began exploring fields. When I first read through Trethewey''s essay, I thought about the way the history of science and the history of racialism are themselves mixed. Specifically, I wondered about the impulse to categorize--the organizing impulse of racial classification got borrowed/intermixed/reused in science during key developmental moments in the seventeenth, eighteenth, and nineteenth centuries. Can this be separated from the way natural philosophers--then scientists--also attached themselves to searching for principles of order/ordering and hierarchy as fundamental truths about nature? Damascan-Ottoman polymath Taqi al-Din Muhammad ibn Ma''ruf ash-Shami al-Asadi (Taqi al-Din), and eventually French philosopher René Descartes, imagined the universe as an orderly, machine-like phenomenon. The idea that the universe has an organized, hierarchical structure is its own kind of abiding metaphor. The attempt to translate humanity (and later, identity) into a mathematical equation was a fundamental political practice that also had its roots in science, and it was also a scientific practice that was driven by politics. Trethewey writes in her poem "Taxonomy" that "this plus this equals this," which is a good summary of how physicists are taught to conceive of the world. Reading that line, I thought of the standard model of particle physics--we call it "the standard model" for short--which names every single particle that humans have ever detected in a collider or some other particle-detection instrument on Earth.

As I read and reread Trethewey''s essay, I found myself wondering whether her critical analysis of miscegenation had direct implications for how particle physics came to be. The ordering impulse that prompted the invention of the mulatto--the human child as a mule--is the same socialized instinct that encourages me to seek out a standard model for the particle menagerie and space-time that actually is my material foundation. I wondered what other abiding metaphors I had been taught as part of my education in cosmology and particle physics and how they were permanently altering how I would perceive the world. We imagine that matter is reducible to identifiable fundamental particles (we''ll come back to these later), and this is an organizing structure for our knowledge of the universe that our metaphors encourage us to arrive at. Hierarchy is baked into how we talk about physics now. One of the major open problems in the particle-physics community is literally "the hierarchy problem" (I''ll return to this in chapter 14). We don''t question the name or the assumption that a hierarchy will emerge. We only conceive of difference in existence and impact through a hierarchy of strength and impact.

This is what happens when you move through the world imagining that the abiding metaphors that govern your intellectual origins are synonymous with reality, when, as Trethewey says, "received knowledge becomes synonymous with truth." Hierarchy as a guiding metaphor has been useful to physicists in the past, but it doesn''t necessarily always serve us--or at least serve us well. One problem with the idea that the universe is reducible to fundamental particles is that the standard model does not explain gravity. We know that gravity is in fact an effect of space-time''s shape--how angles and distances are measured within it. If we imagine that space-time is a stage and the matter in it is a cast of actors, then why would reducibility apply to just the characters (matter) and not the stage (space-time)? At subatomic length scales, we might expect the weird rules of quantum mechanics to kick in. A quantum rule that could become relevant is that every measurable quantity, like distance, has the property whereby the more you try to pin it down, the more jittery it gets. So we might expect that there are jitters in space-time, at the tiniest of scales, and that there may even be a minimum measurable distance. Why would.