More on this book
Kindle Notes & Highlights
Read between
January 4 - January 10, 2025
In 1610 Galileo announced to the world that by observing the heavens through a new instrument—what we would call a telescope—he had discovered that the universe consists of more than meets the eye.
Astronomy is full of homo sapiens-humbling insights.
The American writer Flannery O’Connor once said that every story has “a beginning, a middle, and an end, though not necessarily in that order.”
Einstein in effect reinvented physics.
Yes, scientists preferred to follow the principle of Ockham’s razor, dating back to the fourteenth-century Franciscan friar William of Ockham: Try the simplest assumptions first and add complications only as necessary.
Consider: How long would it take you to count to a million at the “one Mississippi” rate of one second per number? Eleven days—or, to be exact, 11 days, 13 hours, 46 minutes, and 40 seconds. How long would it take you to count to a billion at the same rate? A billion is a thousand million—that is, a million one thousand times over. So you would have to count a million Mississippis—eleven days of counting—a thousand times. That’s 31 years, 8% months. To reach a trillion, you’d have to count to a billion a thousand times—31 years a thousand times, or 31,000 years. A light-year—the distance light
...more
“Within a galaxy, everything moves,” Rubin would write. “In the universe, all galaxies are in motion.” Every two minutes “the earth has moved 2500 miles as it orbits the sun; the sun has moved 20,000 miles as it orbits the distant center of our galaxy. In a 70-year lifespan, the sun moves 300,000,000,000 miles. Yet, this vast path is only a tiny arc of a single orbit: it takes 200,000,000 years for the sun to orbit once about the galaxy.”
But they couldn’t help noticing that the outermost stars and gas seemed to be whipping around the center of the galaxy at the same rate as the innermost stars and gas. It was as if Pluto were moving at the same speed as Mercury.
“Don’t you understand?” Roberts said. “The galaxy has ended, but the velocities are flat.” He gestured at the points he’d plotted. “What is the mass out there? What is the matter? There’s got to be matter there.” They all stared at the photograph. Here was this beautiful swirl of billions of stars—the kind of majestic image that had captivated astronomers for more than half a century—though that’s not where they were looking. They were looking beyond it. Beyond the bulge, beyond the stars, beyond the gas of the spiral arms—beyond all of the light, whether optical or radio.
The universe was simple. It just couldn’t be perfectly simple.
The question of how the universe will end was as old as civilization, but the difference now was that scientists might be able to go out and make the crucial measurement.
If he chose philosophy, he couldn’t do physics. But if he chose physics, he would still be doing philosophy, because in order to do physics you had to ask the big questions. Before science was science (the study of nature through close observation), it was philosophy (the study of nature through deep thought). Even as science had accumulated all manner of empirical scaffolding over the past few centuries, the guiding impulse of the scientist had remained constant: What is our relationship to the natural world?
The idea wasn’t as fanciful as it might seem; studies of Sun-like stars had shown that about 84 percent were in binary systems, meaning that the Sun, if solo, would be an anomaly.
But photography didn’t just allow astronomers to collect light. It allowed them to collect light over time. Light didn’t just land on the photographic plate; it landed and stayed there, and then more light landed and stayed there, and then more light. The sources of light were so faint your eyes couldn’t see them, even with the help of a telescope, but the photographic plate could, because it was acting not like a moment-to-moment sensor but like a sponge. It could soak up light all night long. The longer the exposure, the greater the amount of light on the plate; the greater the amount of
...more
A CCD consists of a small wafer of silicon that collects light digitally; one photon creates one electrical charge. A photographic plate is sensitive to 1 or 2 percent of the available photons; a CCD can approach 100 percent.
“Is the Universe a Quantum Fluctuation?” According to the laws of quantum mechanics, virtual particles can arise out of the emptiness of space—and actually do, as experiments since the middle of the century had shown again and again. Tryon wondered if the universe might be the result of one such quantum pop.
Guth realized that the infant universe could have gone through a process that physicists call a “phase transition” and everybody else calls “the thing that happens when water turns into ice or vice versa.” When the temperature of water changes, the transformation doesn’t happen all at once. It’s not as if the word goes out and suddenly every molecule of H2O in the lake has melted into liquid or hardened into ice. Instead, the transformation happens piecemeal. Even within small sections of the pond the ice isn’t freezing or melting uniformly. Cracks and fissures appear faintly, then harden,
...more
In the summer of 1981, during a hike in the Dolomites, Schramm and Leon Lederman, the director of Fermilab, discussed the idea of founding an institute devoted to the scientific intersection that Schramm had been championing for the previous decade: particle physics and cosmology. The idea was somewhat radical; as Turner said, “The two disciplines had little in common, other than indifference for one another.” But NASA (perhaps as a consolation prize for awarding the Space Telescope Science Institute to Johns Hopkins rather than Fermilab) agreed to fund it, and Lederman and Schramm hired
...more
“The elements have evolved, and are evolving.”
Einstein lacked the courage of his equations: He missed predicting the expanding universe. A later generation lacked the courage of Gamow’s equations: They missed discovering the cosmic microwave background.
What they discovered instead was that our galaxy seemed to be racing through space at nearly 400 miles per second.
For the universe to contain such local volatility yet still appear homogeneous and isotropic on a large scale, that scale was going to have to be much larger than anyone had ever imagined.
From a particle physics perspective, lambda wasn’t just a number. It was a property of space. And space, in particle physics, wasn’t empty. It was a quantum circus, a phantasmagoria of virtual particles popping into and out of existence. Not only did those particles exist, as experiments had shown, but they possessed energy. And energy, in general relativity, interacts with gravity. The result of quantum particles possessing energy that interacts with gravity was what physicists called the Casimir effect, after the Dutch physicist Hendrik Casimir.
The motions of galaxies didn’t make sense unless we inferred the existence of dark matter. The luminosities of supernovae didn’t make sense unless we inferred the existence of dark energy. Inference can be a powerful tool: An apple falls to the ground, and we infer gravity. But it can also be an incomplete tool: Gravity is . . . ? Dark matter is . . . ? Dark energy is . . . ?
How do you see something that is dark, if by “dark” you mean, as astronomers beginning in the 1970s and 1980s did, “impossible to see”? How do you do something that is, by your own definition, impossible to do? You don’t. You rethink the question. For thousands of years, astronomers had tried to apprehend the workings of the universe by looking at the lights in the sky. Then, starting with Galileo, they learned to look for more lights in the sky, those that they couldn’t see with their eyes alone but that they could see through a telescope. By the middle of the twentieth century, they were
...more
In 1986, Prince ton’s Bohdan Paczynski suggested that if these massive objects we couldn’t see did exist in the halo of our own galaxy—where astronomers thought most of the Milky Way’s dark matter resided—we could recognize their presence through a technique called gravitational lensing. In 1936, Einstein had suggested that a foreground star could serve as a lens of sorts on a background star. The gravitational mass of the foreground star would bend space, and with it the trajectory of the light from the background star, so that even though the background star was “behind” the foreground star
...more
Perhaps the most dramatic, and certainly the most famous, indirect evidence for the existence of dark matter was a 2006 photograph of a collision of two galaxy clusters, collectively known as the Bullet Cluster. By observing the collision in x-rays and through gravitational lensing, Douglas Clowe, then at the University of Arizona, separated visible gas from invisible mass. The visible (in x-ray) gas from both clusters pooled in the center of the collision, where the atoms had behaved the way atoms behave—attracting one another and gathering gravitationally. Meanwhile, the invisible mass
...more
How the galaxy clusters had grown over the history of the universe would help astronomers predict which side would win that tug of war in the future.
Since gravity gathered smaller structures into larger ones, and gravity was now losing the tug of war with dark energy, it was reasonable to assume that galaxy clusters would also be the latest-forming gravitationally bound structures in the universe. And as dark energy took a greater and greater toll, they would also be the last-forming such structures. Holzapfel thought of these clusters as the proverbial canaries in a coal mine.
But then, nobody ever said the universe had to be benign.
The meaning of reality might seem a subject best left to philosophers, but, like philosophy itself, it had always been the domain of physicists, too.
Once Galileo had provided empirical evidence that Copernicus’s Sun-centered system was correct, and once Newton had codified the math, scientists came to understand that equations on paper could do more than approximate reality: If you could find it in the heavens, you could capture it on paper—the point Kolb was trying to make. Then Einstein came along and reversed that process. If you could write it on paper, you could find it in the heavens.* If your equations told you that time passed differently for two observers moving in relation to each other, or that gravity bent light, then that was
...more
But Einstein, speaking from his own experience, then proceeded to argue the point that Wetterich was making to Schmidt: “I hold it that pure thought can grasp reality, as the ancients dreamed.”
In one generation astronomy had gone from the lone observer on a mountaintop taking photographs in visible light to dozens of collaborators around the globe pursuing a variety of specializations by looking at increasingly narrow bands along the electromagnetic spectrum.
Inflation already ensured that certain traces of the universe’s initial conditions would be forever out of reach. Those conditions would put even branes to shame, in terms of defying perceptions. If inflation can pop one quantum universe into existence, why not many? In fact, according to quantum theory, it should. It would, if inflation actually happened. In that case, our inflationary bubble would be one of an ensemble of 10500 inflationary bubbles, each its own universe. That’s
...more
It would be the revolution in thought that dark energy mandated. Almost certainly this revolution would require the long-awaited union of general relativity and quantum theory. It might involve modifying Einstein’s equations. It could feature parallel, intersecting, or a virtually infinite ensemble of universes. But whatever this revolution wound up being or doing, it would need what speaker after speaker at conference after conference acknowledged, adopting the same shrugging grace and gratitude as the Dicke birds when they learned they’d been scooped, as Vera Rubin when she realized that
...more
History was posterity in motion.
So: Let there be dark. Let there be doubt, even amid the certainty. Especially amid the certainties—the pieces of evidence that in one generation transformed cosmology from metaphysics to physics, from speculation to science.
“I have this three-year-old daughter at home,” Perlmutter said now, sitting in Smoot’s office, “and we’re just at that stage where she’s asking us, ‘Why?’ It’s pretty obvious that she knows it’s a bit of a game. She knows that whatever we say, she can then say, ‘Yes, but—why?’” He laughed. “I have the impression that most people don’t realize that what got physicists into physics usually is not the desire to understand what we already know but the desire to catch the universe in the act of doing really bizarre things. We love the fact that our ordinary intuitions about the world can be fooled,
...more
