I’ve received various comments, in public and in private, that suggest that quite a few readers are wondering why a Ph.D. physicist with decades of experience in scientific research is spending time writing blog posts on things that “everybody knows.” Why discuss unfamiliar but intuitive demonstrations of the Earth’s shape and size, and why point out new ways of showing that the Earth rotates? Where’s all the discussion of quantum physics, black holes, Higgs bosons, and the end of the universe?
One thing I’m not doing is trying to convince flat-earthers! A flat-earther’s view of the world is so full of conceptual holes that there’s no chance of filling them. Such an effort would be akin to trying to convince a four-year-old Santa Claus devotee that the jolly fellow can’t actually fly through the air and visit half a billion homes, stopping to eat the cookies left for him in every one, all in one night. Logic has no power on a human whose mind is already made up. (If you’re an adult, don’t be that human.)
Instead my goals are broader, and more contemplative than corrective. Here are a few of them.
Better Explanations for the Curious
Science is often presented in grade schools to children as though it is a set of facts to be memorized. But to my mind, this is neither the essence of science nor the most important aspect of science to know. While it’s good for everyone to learn some of the foundational lessons of science, details of these facts can always be looked up in a book or on a website. But it’s more difficult to come to an understanding on one’s own of how science is done, why it is done that way, and why it leads to dependable results.
As far as I know, these crucial elements of the scientific process are rarely taught in grade schools, perhaps because they’re not even conveyed to most science teachers and don’t appear much in textbooks. At best, some kind of cartoon “hypothesis testing” often masquerades as the “scientific method.” But a few isolated tests of this or that hypothesis give no real insight into how and why science manages to produce a reliable vision of the world out of an interlocking, self-checking, extended series of discoveries and interpretations. Nor does it make clear how technology is the ultimate test of scientific claims. Without these insights, science can easily becomes just another belief system. (“Religion is the story we learn at home and in places of worship, and science is the story we’re made to memorize in school.” “The main reason to learn about science is so that we can pass the test on Thursday.” “Science is just the atheist’s creed.”)
It would be ideal if many of the scientific facts presented in science class were taught along with an explanation of how they are known and can be checked. It’s not good when science is presented as dogma, or explained in terms that are either too shallow to be right or too arcane to be clear. So when I find particularly simple ways to confirm basic facts about the world, ones that children could check for themselves or with the guidance of a science teacher, I think it’s important to highlight them. It’s vital that educators of all kinds — parents, science teachers, and indeed all of us who understand how and why science works — be in a position to answer the inevitable skeptical questions… not those from the flat-earther types who won’t listen to reason, but those from children and from adult skeptics who still might. The explanation that finds the right balance — easy to understand, short to explain, possible to directly verify — is usually the best one to lead with. (Rarely is this the one that was used by the original discoverers, who almost always had to think of something far more clever, and to use subtle reasoning and techniques that were then state-of-the-art.)
So that’s why I think it’s worth showing that, with modern technology, there are little-known but conceptually simple methods for confirming essential features of our planet. For those of us who are already science-inclined, these arguments are not necessary. But for those who are not, they may be.
The Importance of Periodic Review
For precisely the reasons I’ve just outlined — that science is a process, not a set of accepted facts — it’s a good idea (and very common) for scientists, whether professionals or students, to review for themselves both how the scientific web of knowledge was assembled historically, and how it holds together nowadays. This kind of exercise is a sort of brain calisthenics; it keeps the mind fresh and clear.
Every time I reconsider what I know from scratch, I learn something new. Typically I find connections between well-known facts that I hadn’t previously recognized. Sometimes I discover gaps in my own logic, and a couple of times in my career I’ve even discovered gaps in the scientific community’s logic. So it’s well worth going through this kind of introspection, even starting at the beginning with basic astronomy.
The basis of knowledge changes over time. Back in Einstein’s early days, people were still using all sorts of clever indirect arguments to prove that atoms exist and demonstrate their properties, whereas nowadays we can explicitly “see” them using special microscopes. Similarly, the Greeks knew the Earth was roughly spherical long before Renaissance explorers actually sailed around it, and before we got our first glimpse of it from outer space. Foucault, in 1850, certainly knew that the Earth was spinning, and was familiar with the scientific data that confirmed it. He designed his famous pendulum not in order to prove that the Earth spins, but to demonstrate it to others for whom precise astronomical measurements and complex scientific arguments have little meaning. Through the slow rotation of the pendulum, the Earth’s spin became public knowledge, in the best sense, rather than esoteric wisdom. But Foucault knew a gyroscope would be better, for reasons that I emphasized in my last post. Technology wasn’t up to it then, but it is now, though still too expensive for museums and universities.
When we find simpler explanations and demonstrations, we streamline the learning and teaching of science, even at the professional level. This makes a larger fraction of science more obvious to a larger set of people. That’s always good. It allows us to place our focus on newer, more subtle, and more controversial developments in science, especially those whose implications might threaten our species’ and our planet’s future.
Chance, Limitations, and Humility
There’s another important mental exercise, healthy for scientists and non-scientists alike. We should never forget that the timing and details of scientific discoveries are often impacted by the limitations of both the human body and the environment in which we find ourselves. Imagine, for instance, that we were unable to hear sound. How would this limitation have correspondingly curtailed our scientific knowledge? Considering these sorts of questions should give us pause, and make us wonder how our actual limitations might be currently affecting our understanding of the world.
Suppose that Earth, like Venus, was covered in a permanent layer of thick cloud. We’d infer the existence of the Sun from the daily pattern of light and dark, and of the Moon from ocean tides, but we’d have no intuitive idea of their size, shape, appearance or distance. And of the stars, we’d know nothing at all.
Without this information, much of what the pre-industrial world knew about the Earth would have been inaccessible. Most ancient Greek methods of ascertaining the Earth’s properties relied on shadows — of the Earth on the Moon, or of tall poles on the ground — and on analogy — if the Sun and Moon are spheres, why not the Earth? (The only exception I can think of is the observation that ships disappear hull-first as they sail away, which indicates that the Earth’s surface is slightly curved; but how would you confirm this is not an optical illusion?)
Despite this limit on our sensory experience, technology of the nineteenth and twentieth century would have allowed us to infer the shape, size, and spin rate of the Earth, using the methods I described in recent weeks: volcanic explosions for the shape and size, a big pendulum or a gyroscope for the spin. The knowledge would have come many centuries late, but would not have escaped us entirely.
But here’s something for you to ponder. Could we have determined whether the Earth orbits the Sun?
Meanwhile, what if the surface of the Earth were dangerous and inaccessible for some reason, and we lived far below it? This is not as strange a speculation as it may sound. Most planets and moons in the universe may have uninhabitable surfaces. But oceans underneath thick ice crusts may be kept warm either by underground radioactivity or, for a moon near a large planet, by tidal forces. Certain moons of the Sun’s outer planets are in this category. It is quite possible that the majority of intelligent life in the universe lives in such oceans, sandwiched between a rocky bottom and a thick ice crust that never melts.
If we were such a species, what would we know? Shock waves could travel round an ocean as well as around an atmosphere, so the method that exploits volcanic explosions would permit a measurement of our home’s shape and size. It’s spin could be revealed by a Foucault’s pendulum or a gyroscope. The Sun and any other nearby objects could be inferred from tides, though again, little would be known about them.
At some point, we’d perhaps find technology that would allow us to climb above the ice. What a remarkable day that would be: our first glimpse, through the eyes of a robotic camera, of the Sun, the stars, and perhaps a giant planet filling a third of the sky.
Except for one thing. A species living in an subsurface ocean probably wouldn’t have eyes, for what good would they be? And in that case, what technologies would they put on a robot sent to break through the ice? Would some technologies that we humans take for granted be so underdeveloped that they would not have been considered?
Like most Earthly mammals, a subsurface species might well have senses of smell and hearing far better than their sense of sight, and would be much more interested in what the region above the ice smells and sounds like, rather than what it looks like. Only after journeying out of the atmosphere would it be learned that space is mostly vacuum, where neither hearing or smell is of much use. Yet the scientists of this species might still be initially more inclined toward developing powerful chemical sensors — smell-detectors — for exploring the cosmos, rather than focusing on the eye-like telescopes that we humans are so familiar with.
These considerations are entertaining, but they display their teeth when we turn them around on ourselves. What does our own heavy reliance on seeing make us “blind” to? And what scientific insights might lie hidden due to the accidents of our planet’s particular features, of our location in the cosmos, or of the time when we’re alive?
Had our eyes been just a bit stronger, the discoveries of Galileo — the moons of Jupiter, the rings of Saturn, the phases of Venus, the craters of the Moon, and the spots on the Sun — would all have been known to everyone for generations, and would not have needed the technology of the telescope. Had we been born close to our galaxy’s center, where stars are far closer to one another, we might well have known in ancient times that we orbit an ordinary star, and perhaps would know far more about stars and black holes than we do now. How would our progress in science have been different if we could sense magnetic fields, as migrating birds seem to?
Muons from cosmic rays pass through our bodies constantly, but we only learned about them in 1936. Is it conceivable that there might exist species that can sense them? Why not? Creatures living at a time and place in which cosmic ray storms were common might require early warning of the deadly radiation to come, in order to take refuge underground.
It is difficult but important to stretch the mind in these directions, and imagine possibilities that may at first seem remote. When we do so, we learn that we may know far less about the universe than many believe we do. What else lies just beyond our current reach, merely because of the accidents of where and when we live, and of who and what we are?