Astrophysics for People in a Hurry

“[I]gnorance is the natural state of mind for a research scientist. People who believe they are ignorant of nothing have neither looked for, nor stumbled upon, the boundary between what is known and unknown in the universe.”

What science knows about the universe isn’t revealed but must be sought out. It’s easy to assume that people know all the answers, but, as scientists continue to explore reality, it keeps serving up new surprises. An attitude of humility toward what we don’t yet know serves science by keeping researchers hungry for new discoveries.

“We are stardust brought to life, then empowered by the universe to figure itself out—and we have only just begun.”

Humans have the privilege of wondering about the universe and exploring it to learn its secrets. It’s taken a tremendously long time to reach this point, and it’s something of an honor to be able to indulge our curiosity and learn about the mysteries of the cosmos. This may merely be the beginning of a long and grand adventure of discovery.

“According to Christian teachings of the day, God controlled the heavens, rendering them unknowable to our feeble mortal minds. When Newton breached this philosophical barrier by rendering all motion comprehensible and predictable, some theologians criticized him for leaving nothing for the Creator to do.”

Newton’s laws of physics apply everywhere, not just on our planet. The realm beyond our world is made of basically the same stuff as are we; thus, God’s heavenly domain must lie elsewhere. This idea caused a change in people’s view of the universe, and it threatened the settled ideas of religious belief.

“Cosmologists have plenty of ego. How could you not when your job is to deduce what brought the universe into existence? Without data, their explanations were just hypotheses. Now, each new observation, each morsel of data, wields a two-edged sword: it enables cosmology to thrive on the kind of foundation that so much of the rest of science enjoys, but it also constrains theories that people thought up when there wasn’t enough data to say whether they were right or wrong. No science achieves maturity without it.”

One of the essential lessons of the book is that science advances through observation and that theories stand or fall not on their elegance or the fame of the theorist but on the data that either backs or refutes them. Science is ruthless about learning what’s true; what we wish were true is irrelevant.

“Aided by modern detectors, and modern theories, we have probed our cosmic countryside and revealed all manner of hard-to-detect things: dwarf galaxies, runaway stars, runaway stars that explode, million-degree X-ray-emitting gas, dark matter, faint blue galaxies, ubiquitous gas clouds, super-duper high-energy charged particles, and the mysterious quantum vacuum energy. With a list like that, one could argue that all the fun in the universe happens between the galaxies rather than within them.”

The author takes an interest in not only the glamorous galaxies but also the less glamorous but arguably more important spaces between them. This permits him to look at the universe from angles that reveal things hidden from most popular books’ viewpoints. This added perspective helps make the book’s cosmology more compelling to non-science readers. The author avoids dry terminology and instead describes the discoveries of astrophysics in enthusiastic terms. He transmits his love for his field and makes the science of outer space seem adventurous.

“Nobody doesn’t like intergalactic space, but it can be hazardous to your health if you choose to go there.”

In his droll way, the author touts the fascination of intergalactic space while pointing out that, despite its interesting attributes, it’s not a place for normal human life. For that matter, most of the universe isn’t safe for people, yet it teaches many useful and absorbing lessons about the nature of reality, and it hints quietly that oases other than Earth must exist here and there amid the emptiness.

“The worst that can happen is we discover that dark matter does not consist of matter at all, but of something else. Could we be seeing the effects of forces from another dimension? Are we feeling the ordinary gravity of ordinary matter crossing the membrane of a phantom universe adjacent to ours? If so, this could be just one of an infinite assortment of universes that comprise the multiverse. Sounds exotic and unbelievable. But is it any more crazy than the first suggestions that Earth orbits the Sun? That the Sun is one of a hundred billion stars in the Milky Way? Or that the Milky Way is but one of a hundred billion galaxies in the universe?”

The strange, even contradictory discoveries of science sometimes test people’s reason, and we’re tempted to protest that those discoveries must be false because they make no sense. If the observations are correct, though, it’s not the observed phenomena that are wrong but our presuppositions about how our universe works. Much as Renaissance clerics couldn’t wrap their heads around the idea that the Earth orbits the Sun, people today have trouble with the possibility that our universe is one of many. The virtue of scientific inquiry is that it presents the data without bias, regardless of how that data might offend our sensibilities.

“Distant galaxies now visible in the night sky will ultimately disappear beyond an unreachable horizon, receding from us faster than the speed of light […] In a trillion or so years, anyone alive in our own galaxy may know nothing of other galaxies […] Are we, too, missing some basic pieces of the universe that once were? What part of the cosmic history book has been marked ‘access denied’? What remains absent from our theories and equations that ought to be there, leaving us groping for answers we may never find?”

The glory of science arises from using direct observation to deduce principles of the universe. The agony of scientists, then, is a puzzle that can’t be resolved by collecting data. If the universe were to expand beyond human ability to observe its receding parts, this would create a mystery that might never be solved. If such a situation is possible in the future, scientists can’t be sure they’re not already missing out on critical data about the cosmos—or about any phenomenon—that’s somehow no longer available.

“Trivial questions sometimes require deep and expansive knowledge of the cosmos just to answer them.”

This comment contains at least three major implications. First, small knowledge often derives from large knowledge: The author’s example is that the elements in the Earth’s crust can’t be fully understood without knowing the history of the universe, including how supernovas generate heavier atoms and disperse them. Second, it’s a testament to the importance of astrophysics, which might seem irrelevant to Earthly concerns but in fact helps us better understand our own world. Third, it’s a lesson on how to think: There’s more to everything than surface appearances.

“For reasons I have yet to understand, many people don’t like chemicals, which might explain the perennial movement to rid foods of them. Perhaps sesquipedalian chemical names just sound dangerous. But in that case we should blame the chemists, and not the chemicals themselves. Personally, I am quite comfortable with chemicals, anywhere in the universe. My favorite stars, as well as my best friends, are all made of them.”

The word chemical often causes people to panic because they think chemicals are poisonous. The word conjures up chemistry labs, toxins, and suspicious materials added to foods. However, water is a chemical, and people are made up mostly of chemicals. In fact, the word applies to nearly all pure stuff made of atoms, from aluminum foil to table salt. The author’s point is that we should be careful to understand the full meaning of basic scientific names and not allow ourselves to be railroaded into fearing things that are safe.

“In short, where gravity is high, the high places tend to fall, filling in the low places—a phenomenon that sounds almost biblical, in preparing the way for the Lord: ‘Every valley shall be raised up, every mountain and hill made low; the rough ground shall become level, the rugged places a plain’ (Isaiah 40:4). That’s a recipe for a sphere if there ever was one.”

Pulsars, the remains of large, dead stars, are so densely packed that one the size of Manhattan would contain the mass of something as large as the Sun. Gravity is extreme on their surfaces, which therefore become extremely smooth. The author cites a famous Christian prophecy as a way of suggesting that, after all the stars have died, their remnants will similarly be smoothed out, as if fulfilling the biblical command.

“Spheres are indeed fertile theoretical tools that help us gain insight into all manner of astrophysical problems. But one should not be a sphere-zealot. I am reminded of the half-serious joke about how to increase milk production on a farm: An expert in animal husbandry might say, ‘Consider the role of the cow’s diet…’ An engineer might say, ‘Consider the design of the milking machines…’ But it’s the astrophysicist who says, ‘Consider a spherical cow…’”

This is a famous joke among physicists, who know that their penchant for simplifying things by imagining them as spherical can lead to interesting discoveries but isn’t a practical way to solve more complex problems in the everyday world. A sphere is the simplest, most elegant shape, and it can contain volumes more efficiently than any other shape, which explains why spherical objects occur so often in the universe. For those objects, considering them to be spherical works in scientific investigations simply because they are spherical. Cows, not so much. 

“There are more things in heaven and earth, Horatio,

Than are dreamt of in your philosophy.”

This quote from Shakespeare’s play Hamlet captures nicely one of the main themes of the present book, which stresses that it takes an open and daring mind to do science, especially when the things to be studied fly in the face of our preconceptions. The universe is filled with nonintuitive things—the constant speed of light, no matter how speedy the observer; the expansion of space, which makes its furthest reaches impossible to observe; the disappearance of mass into black holes—and scientists, along with the taxpayers who support scientific work, must be willing to be stunned and challenged by such discoveries.

“Well-conducted experiments require a ‘control’—a measurement where you expect no effect at all, and which serves as a kind of idiot-check on what you are measuring. For example, if you wonder what effect beer has on a tulip plant, then also nurture a second tulip plant, identical to the first, but give it water instead. If both plants die—if you killed them both—then you can’t blame the alcohol. That’s the value of a control sample.”

It’s important when trying to learn about something to keep thinking beyond one’s first ideas. The concept of a control is an improvement over the simple notion of testing an effect on one thing. It keeps us from making too many assumptions, and it makes more rigorous the entire test. The author isn’t merely teaching simple astrophysics. He’s also teaching basic science, how to think like a scientist, and how to be skeptical.

“In retrospect, we didn’t have to go to the Moon to retrieve Moon rocks. Plenty come to us, although they were not of our choosing and we didn’t yet know it during the Apollo program.”

Part of the value of discovery is how it teaches us things we never expected. Humans traveled to the Moon partly to retrieve its rocks for study, not yet realizing that Moon rocks get splashed off its surface by bombarding asteroids and comets and fall down Earth’s gravity well and land on our planet. Now and then even Mars gets hit and splatters rocks into space that find their way to Earth. The rocks that plow through our atmosphere to land on the surface also plow through our ignorance about how the solar system works. Each such rock tells a story of the dynamic features of the space all around us.

“Whether you prefer to sprint, swim, walk, or crawl from one place to another on Earth, you can enjoy close-up views of our planet’s unlimited supply of things to notice. You might see a vein of pink limestone on the wall of a canyon, a ladybug eating an aphid on the stem of a rose, a clamshell poking out from the sand. All you have to do is look.”

It’s part of the author’s job to notice things. Though he focuses mainly on celestial objects, his mind is well trained to observe anything of interest. Though the purpose of the comment is to discuss what it’s possible to see at various scales, the underlying message is that the world is full of things, not simply in outer space but all around us on Earth, and that the universe can be amazing wherever we pay attention to it.

“Looking more closely at Earth’s atmospheric fingerprints, human biomarkers will also include sulfuric, carbonic, and nitric acids, and other components of smog from the burning of fossil fuels. If the curious aliens happen to be socially, culturally, and technologically more advanced than we are, then they will surely interpret these biomarkers as convincing evidence for the absence of intelligent life on Earth.”

The author makes a wry comment about the human tendency to pollute its world with burning hydrocarbons. Alien observers might be tempted to conclude that our species is too foolish to survive, or they might also have gone through a similarly dangerous stage of development and will take bets on whether we make it past our own folly.

“Of all the sciences cultivated by mankind, Astronomy is acknowledged to be, and undoubtedly is, the most sublime, the most interesting, and the most useful. For, by knowledge derived from this science, not only the bulk of the Earth is discovered […]; but our very faculties are enlarged with the grandeur of the ideas it conveys, our minds exalted above [their] low contracted prejudices.”

This epigram from 18th-century astronomer and science popularizer James Ferguson neatly encapsulates the author’s own enthusiasm for astronomy and astrophysics. Ferguson believed, and the author agrees, that the study of the cosmos benefits and ennobles humanity. The study of our enormous universe can put our petty squabbles and violent conflicts into better perspective while inspiring desire to learn together about the vast cosmos in which we live.

“Now imagine a world in which everyone, but especially people with power and influence, holds an expanded view of our place in the cosmos. With that perspective, our problems would shrink—or never arise at all—and we could celebrate our earthly differences while shunning the behavior of our predecessors who slaughtered one another because of them.”

Though it requires a society wealthy and technologically advanced enough to indulge its curiosity, astrophysics isn’t an idle pursuit with no application to the problems of daily life. For one thing, it helps focus our energies on areas of interest to everyone—we’re destined to try, at least, to visit the faraway worlds we study today—and the need to cooperate worldwide on the large cosmological experiments we undertake forces us to address disagreements in a friendly and cooperative manner. Astrophysics doesn’t directly cure poverty, but it adds to our knowledge and brings us together, which enhances efforts to abolish the suffering humans still inflict on one another. 

“[…] more bacteria live and work in one centimeter of my colon than the number of people who have ever existed in the world. That kind of information makes you think twice about who—or what—is actually in charge.”

Some people who realize how large the universe actually is become depressed with that knowledge. The author points out that people also are gigantic in comparison to the smallest things in the universe. Both perspectives call into question our conceits about our place in the universe. The simple fact of the amazing scale of the universe ought to leave us in awe about where we live.

“Imagine a life-form whose brainpower is to ours as ours is to a chimpanzee’s. To such a species, our highest mental achievements would be trivial. Their toddlers, instead of learning their ABCs on Sesame Street, would learn multivariable calculus on Boolean Boulevard. Our most complex theorems, our deepest philosophies, the cherished works of our most creative artists, would be projects their schoolkids bring home for Mom and Dad to display on the refrigerator door with a magnet.”

The genetic variations between humans and chimps are very small, yet the differences in their abilities to think are quite large. If it doesn’t take much to improve a creature’s capacity to do advanced calculations, then there may be creatures in the universe, not too different from ourselves, who can easily outthink our smartest minds.

“Every cup [of water] that passes through a single person and eventually rejoins the world’s water supply holds enough molecules to mix 1,500 of them into every other cup of water in the world. No way around it: some of the water you just drank passed through the kidneys of Socrates, Genghis Khan, and Joan of Arc.”

The sheer immensity of the numbers of molecules in a single cup of water leads not to despair but to a sense of unity with all other people. It’s also true that every breath you take contains molecules inhaled by every person who ever lived. We are inseparably embedded in the ongoing project of life; our smallest activities are connected to the entire history of humanity.

“At least once a week, if not once a day, we might each ponder what cosmic truths lie undiscovered before us, perhaps awaiting the arrival of a clever thinker, an ingenious experiment, or an innovative space mission to reveal them. We might further ponder how those discoveries may one day transform life on Earth.”

The author’s perspective, both as an astrophysicist and a human, is forward looking. He believes that science and creative imagination are good for us and offer a perspective wider and more accurate than the biased, self-serving, arrogant viewpoint we often assume. The power of intelligence can do much more than invent weapons and new techniques of dominating others; it can also project possibilities for a human-made paradise on Earth if we’re willing to try for it.