Chapter Content
Okay, so, like, picture this, right? It's the late 1800s, and scientists are feeling pretty good about themselves. They're, like, patting themselves on the back because they think they've basically figured out everything. I mean, electricity, magnetism, gases, optics, sound, motion, they're all, you know, bowing down to these scientists. They've discovered X-rays, electrons, all that stuff, and they've even got these fancy units of measurement with names like Ohm and Watt and, like, Kelvin. Pretty cool, right?
Basically, if it could be vibrated, accelerated, distilled, weighed, turned into a gas, they did it. And, in the process, they came up with all these, like, super important laws. And, get this, the laws are so important, they're written with capital letters. You know, like "The Law of..." something or other. There are so many laws, it's, like, mind-boggling. The world is, you know, buzzing with all these new machines and inventions. So, a lot of smart people thought, "Well, looks like science is basically done."
So, there's this young guy, Max Planck, in Germany, and he's trying to decide if he should study math or physics. And everyone is, like, seriously trying to talk him out of physics. They're telling him, "Dude, all the big problems are solved. The next century is just going to be, you know, tidying up loose ends, not some revolution." But Planck, being Planck, ignores them and dives into theoretical physics, focusing on entropy. Entropy is a measure of disorder, you know, like a shuffled deck of cards compared to a brand-new deck, still in order.
Anyway, he thinks this is a promising area of research. He actually makes some progress, but then he discovers that some guy at Yale, this really quiet, secluded dude named J. Willard Gibbs, had already done it.
Now, Gibbs is a fascinating guy, even if most people haven’t really heard of him. He's, like, super reserved. He barely leaves his little neighborhood. He spends most of his life within, like, a three-block radius in New Haven, Connecticut, just going between his house and Yale. For the first ten years at Yale, he doesn't even bother collecting his salary. He had other income, apparently. He becomes a professor in 1871 and stays there until he dies in 1903. And get this, he only has, like, one student per semester, on average. His writing is, like, crazy complicated, full of his own symbols. But buried in those crazy formulas are some amazing insights.
From 1875 to 1878, Gibbs writes this series of papers, later compiled into a book about thermodynamics. It basically covers everything: gases, mixtures, solids, chemical reactions, you name it. What Gibbs wanted to show was that thermodynamics applies not just to, like, steam engines, but also to the atomic level of chemical reactions. Now, for some reason, Gibbs publishes these groundbreaking ideas in some obscure journal in Connecticut. That's why Planck doesn't hear about him until much later.
Planck doesn't give up, but, you know, maybe he's a little discouraged. So, he starts looking at other stuff. But hold on, let's, like, switch gears for a minute and head over to Cleveland, Ohio. There's this physicist, Albert Michelson, who is working with his friend, a chemist named Edward Morley. They're doing these experiments that are going to have a huge impact on the future.
What Michelson and Morley were actually doing, unintentionally, mind you, was, like, disproving the existence of this thing called the "luminiferous ether." It was supposed to be this, like, invisible, weightless, frictionless medium that filled the universe. Everyone, even freaking Newton, believed in it because it was supposed to be the thing that light waves traveled through. Light was thought to be a wave. And waves need a medium to travel through. So, everyone thought, "Yep, there's got to be an ether." Until, of course, it turned out there wasn't.
If you want a story about the American dream, look at Albert Michelson. He was born in a poor Jewish family, and they immigrated to America and ended up in a mining town during the gold rush. His family was so poor, he couldn’t afford college. He went to Washington, D.C., and hung around the White House, hoping to run into President Ulysses S. Grant during his daily walks. Apparently, Grant liked Michelson and got him into the U.S. Naval Academy. That's where he studied physics.
Ten years later, Michelson is a professor in Cleveland and starts trying to measure this "ether drift," the headwind created as the Earth moves through space. According to Newtonian physics, the speed of light should appear different depending on whether you're moving toward or away from the light source. But nobody could figure out how to measure it. Michelson had this idea that since the Earth moves toward the sun for half the year and away for the other half, he could measure the difference in the speed of light at different times of the year.
Michelson gets Alexander Graham Bell, who's like, fresh off inventing the telephone and rich, to fund the creation of this super precise instrument called an interferometer. Then, with Morley's help, he spends years taking careful measurements. It's such a delicate and intense process that Michelson, like, has a nervous breakdown and has to stop for a while.
But by 1887, they have their results. And the results are completely unexpected.
As astrophysicist Kip Thorne put it, "The speed of light proved to be the same in all directions, in all seasons." This was, like, the first sign in 200 years that maybe Newton's laws weren't so universal after all. It was, in the words of one scientist, "possibly the most famous negative result in the history of physics." Michelson eventually wins the Nobel Prize for this - the first American to do so. But for years, the Michelson-Morley experiment just, like, hangs over the scientific community like a bad smell.
What's amazing is that even after this, Michelson thought that science was basically coming to an end. You know, just, like, putting on the finishing touches, the little flourishes.
But, of course, the world was about to enter a scientific revolution. It was a time when everyone would know a little bit, but nobody would know everything. Scientists were about to find themselves swimming in a sea of particles and anti-particles. Things would be popping in and out of existence so fast that even nanoseconds would seem slow. It was all going to get really weird. Science was about to switch from macroscopic physics, where you can see and touch things, to microscopic physics, where things happen too fast to even imagine. We were entering the quantum age, and the first guy to open the door was that previously unlucky Max Planck.
In 1900, Planck, now 42, and a theoretical physicist at the University of Berlin, unveiled his new "quantum theory." This theory said that energy isn't a continuous flow, but rather it comes in packets, which he called "quanta." It was a radical idea, and a good one. In the short term, it helped explain the Michelson-Morley experiment by suggesting that light might not necessarily be a wave. In the long term, it would lay the foundation for all of modern physics. Anyway, it was, like, the first sign that things were about to change.
But the really big stuff, the dawn of a new era, didn't happen until 1905. In that year, a German physics journal, *Annalen der Physik*, published a series of papers by this young Swiss clerk. He hadn't gone to college, he didn't have a lab, and he mostly just used the library at the Swiss patent office. He was a third-class technical examiner, mind you. He applied for second-class, and they turned him down.
His name was Albert Einstein. And in that one year, he sent *Annalen der Physik* five papers. Three of them were, in the words of C.P. Snow, "among the greatest in the history of physics." One paper looked at the photoelectric effect using Planck's quantum theory, one was about the behavior of small particles in suspension, which is known as Brownian motion, and one outlined his theory of special relativity.
The first paper explained the nature of light and won him a Nobel Prize. The second provided proof that atoms actually exist - something that was still being debated, believe it or not. The third, well, it completely changed the world.
Einstein was born in Germany in 1879, but he grew up in Munich. His early life didn't really suggest he would become a genius. He didn't even start talking until he was three. In the 1890s, his father's electrical business went bankrupt, and the family moved to Milan. Einstein, who was a teenager by then, went to Switzerland to continue his studies, even though he failed his first college entrance exam. He renounced his German citizenship in 1896 to avoid military service and went to the Swiss Federal Polytechnic in Zurich to study to become a high school teacher. He was a smart but not outstanding student.
In 1900, he graduated and started submitting papers to *Annalen der Physik*. His first paper was about, of all things, the physics of fluids in straws. He then wrote a series of papers on statistical mechanics and discovered that J. Willard Gibbs had already quietly published the same stuff.
Albert also fell in love with a classmate, a Hungarian woman named Mileva Marić. In 1901, they had a daughter, before they were married, and put the baby up for adoption. Einstein never saw his child. Two years later, he married Marić. In the meantime, Einstein took a job at the Swiss patent office, where he would stay for the next seven years. He liked the job because it was challenging enough to keep his mind busy, but it didn't distract him from his physics. And it was against this background that he developed his theory of special relativity in 1905.
"On the Electrodynamics of Moving Bodies" is, like, one of the most amazing scientific papers ever published. It has no footnotes, no citations, barely any math, and doesn't mention any work that influenced it. It only thanks one person, a colleague at the patent office named Michele Besso. C.P. Snow wrote that Einstein seemed to have "reached the conclusions by pure thought, alone, unaided." And, for the most part, that's true.
His famous equation, E=mc², doesn't appear in this paper, but it does appear in a short addendum a few months later. E stands for energy, m stands for mass, and c² stands for the speed of light squared.
In the simplest terms, this equation means that mass and energy are equivalent. They're just two forms of the same thing: energy is released mass, and mass is energy waiting to be released. And since c² is a huge number, this equation means that every object contains an incredible amount of energy. You may not feel like a powerhouse, but an average-sized adult contains the potential equivalent of about 30 hydrogen bombs if you knew how to release it. And every single object contains that kind of energy.
Einstein's theory explained how radioactivity works, how uranium continuously emits radiation without melting like an ice cube. It explained why stars can burn for billions of years without running out of fuel. It gave geologists and astronomers billions of years more to play with. It also showed that the speed of light is constant and that nothing can travel faster than light. This helps us understand the nature of the universe. And it also solved the problem of the luminiferous ether by showing that it doesn't exist.
Physicists didn't really pay much attention to what a patent clerk was writing, so despite being informative, Einstein's papers didn't get much attention. Einstein applied for a university lectureship but was rejected. Then, he applied for a high school teaching job and was rejected again. So, he went back to his job as a third-class examiner, where he continued to think. And he was far from finished.
The poet Paul Valéry once asked Einstein if he carried a notebook to record his thoughts. Einstein looked at him, a little surprised, and said, "Oh, that's not necessary. I rarely carry a notebook." It would have been nice if he did. Einstein's next idea was the greatest of all ideas. It was "unquestionably the highest intellectual achievement of man," in the words of one historian.
In 1907, or so the story goes, Einstein started thinking about gravity after seeing a worker fall off a roof. Although, like all good stories, the truth seems questionable. Apparently, Einstein was just sitting in a chair when he started thinking about gravity.
Actually, Einstein started thinking about how to explain gravity. He realized from the beginning that something was missing from his special theory of relativity, and that was gravity. His special theory only dealt with things moving without any obstacles. But what happens when a moving object, especially light, encounters an obstacle like gravity? He spent the next ten years thinking about this, and in 1917, he published a paper called "Cosmological Considerations in the General Theory of Relativity." Now, special relativity was a profound achievement. But, if Einstein hadn't come up with it, someone else would have within five years. It was something that was bound to happen. But general relativity was different. Without it, one scientist wrote, "we might still be waiting for the theory today."
Einstein was a pipe-smoking, gentle, private, and eccentric character, and it was impossible for him to stay hidden forever. In 1919, after the war, the world suddenly discovered him. And at the same time, his theory of relativity became famous for being incomprehensible. *The New York Times* decided to write a story about it, and for some reason, they sent a golf reporter to interview him.
The reporter, predictably, got everything wrong. He claimed that Einstein had found a publisher brave enough to publish a book that only 12 people in the world could understand. No such book or publisher existed. But the idea stuck. Soon, in people's minds, the number of people who could understand relativity got even smaller.
The British astronomer Arthur Eddington was asked if it was true that he was one of only three people in the world who understood Einstein's theory. Eddington paused and said, "I'm trying to think who the third person is." The problem with relativity wasn't that it involved a lot of differential equations and other complicated math, but that it wasn't intuitive.
Essentially, relativity says that space and time aren't absolute, but relative to the observer. And the faster you move, the more pronounced the effect. We can never accelerate ourselves to the speed of light. The more we try, the more distorted we become to an outside observer.
At the same time, popularizers tried to make these concepts understandable to the general public. Bertrand Russell wrote a book called *The ABC of Relativity*. He used the analogy of a train 90 meters long traveling at 60% of the speed of light. To someone standing on the platform, the train would appear to be only 70 meters long. The people on the train would sound slow and slurred. Their movements would seem clumsy. Even the clocks on the train would appear to be running at only four-fifths of their normal speed.
But, and here's the thing, the people on the train wouldn't notice anything different. Everything would seem normal to them. It would be us on the platform who would appear small and slow. It all depends on your position relative to the moving object.
In reality, this effect happens every time you move. Every time you fly across the country, you step off the plane a tiny fraction of a second younger than the people who left after you. Even walking across the room changes your experience of space and time. It's just that the changes are too small for us to notice. But for other things in the universe, like light, gravity, and the universe itself, these things matter.
So, if the concepts of relativity seem a little strange, it's only because we don't experience these interactions in our everyday lives. However, we do often encounter other kinds of relativity, like with sound. If you're at a park and someone is playing bad music, you know, the music seems quieter the further you walk away. It isn't that the music is quieter. It's just that your position relative to the music has changed. It might be hard to believe, to something really small or slow, that a speaker can produce, like, two different music volumes.
The most challenging and unintuitive idea in general relativity is that time is a component of space. We instinctively think of time as eternal and absolute. In fact, Einstein argued, time is changeable. Time even has shape. Time is combined with three dimensions of space to form an entity called "spacetime."
Spacetime is usually explained by saying, "Imagine a flat, flexible surface, like a carpet, with a heavy object, like an iron ball, placed on it." The weight of the ball makes the carpet stretch and sag. That's roughly analogous to the effect of a massive object, like the sun, on spacetime. Now, if you roll a smaller ball across the carpet, it will try to move in a straight line. But as it approaches the larger ball, it will roll toward the lower point, and be pulled toward it. That's gravity, a product of the curvature of spacetime.
Any object with mass creates a tiny dimple on the fabric of the universe. From this point of view, gravity is an effect. In the words of physicist Michio Kaku, it's "not a 'force' but a by-product of the warping of space and time."
Of course, the sagging carpet analogy can only help us understand so much because it doesn't include the effect of time. But even so, that’s about as far as the brain can imagine things. It's nearly impossible to imagine space and time woven together to form a fabric of spacetime. But, I think we can all agree, it was an impressive insight for a young man staring out a window at the Swiss patent office.
Einstein's theory of general relativity made many predictions. One of them was that the universe must either be expanding or contracting. But Einstein wasn't a cosmologist, so he accepted the prevailing view that the universe was static and eternal.
Somewhat instinctively, he added something called the "cosmological constant" to his equations, which was basically a mathematical fudge factor. He did this to counteract the effects of gravity. History books tend to forgive Einstein for this mistake, but it was actually a pretty big blunder. He called it "the biggest blunder of my life."
Coincidentally, around the same time that Einstein was adding this constant to his theory, an astronomer at the Lowell Observatory in Arizona was recording the spectra of distant stars and noticed that they seemed to be moving away from us. This astronomer had an epic, galaxy-worthy name: Vesto Slipher.
It turns out that the universe isn't static. Slipher discovered that these stars were exhibiting a Doppler shift, the same mechanism you hear from a car passing you on the race track. This phenomenon also applies to light. In the case of receding galaxies, it's called a redshift.
Slipher was the first to notice this effect and realize its importance for understanding the movement of the universe. Unfortunately, no one paid much attention to him. You’ll recall that Percival Lowell had been there, studying canals on Mars, so the Lowell Observatory was a, let’s say, “unique” place to be. In the early 1900s, it was basically a backwater. Slipher didn't know about Einstein's theory of relativity, and the world didn't know about Slipher, so his discovery didn't have much of an impact.
The credit ended up going to a very self-assured guy named Edwin Hubble. Hubble was born in 1889 in Missouri and grew up there and in Illinois. He was a gifted athlete and was also charming, stylish, and handsome. By his own account, he was always doing heroic things. He was a world-class liar.
This was unusual because Hubble's life was full of real achievements. At a track meet in 1906, he won first place in the pole vault, shot put, discus, hammer throw, standing high jump, running high jump, and the relay race. In the same year, he set the Illinois state record for the high jump.
As a scholar, he breezed into the University of Chicago, where he studied physics and astronomy. He was then selected as one of the first Rhodes Scholars to Oxford University. When he returned to Illinois in 1913, he was wearing a long cape, smoking a pipe, and speaking in a strange accent, something he would maintain for the rest of his life. He later claimed that he had worked as a lawyer in Kentucky in the 1920s, but actually, he had been teaching high school and coaching basketball in Indiana.
In 1919, at the age of 30, he moved to California and took a job at the Mount Wilson Observatory. He quickly became one of the most important astronomers of the 20th century.
Let's pause for a moment to consider how little people knew about the universe at the time. Today, astronomers believe there may be 140 billion galaxies in the visible universe. This is a massive number. If you compared each galaxy to a kidney bean, the beans would fill the old Boston Garden. In 1919, when Hubble first looked through a telescope, we only knew of one galaxy: the Milky Way. Everything else was either thought to be part of the Milky Way or a cloud of gas far away. Hubble soon proved this view to be wrong.
Over the next ten years, Hubble set out to answer two of the most fundamental questions about the universe: How old is it? How big is it? To answer these questions, he had to know two things. How far away are certain galaxies, and how fast are they moving away from us? Redshift could tell us how fast they were receding, but not how far away they were. To do that, he needed something called a "standard candle."
Hubble got lucky. Shortly before, a woman named Henrietta Swan Leavitt had figured out a way to find these stars. Leavitt was a "computer" at the Harvard College Observatory. The computers spent their lives studying photographs of stars and making calculations. It was a thankless job. But in those days, it was the closest women could get to astronomy at Harvard. This system had an unexpected benefit. It meant that half of the smartest minds were put to work on things that men might have overlooked.
Another Harvard computer, Annie Jump Cannon, invented a system for classifying stars that is still used today. Leavitt's contribution was even more profound. She noticed that a type of star called a Cepheid variable pulsed rhythmically. Cepheid variables are rare, but at least one of them is familiar to most of us. The North Star is a Cepheid variable.
We now know that Cepheid variables pulsate because they have become red giants. The chemical processes in red giants are difficult to understand. But, in brief, as they burn their remaining fuel, they create a rhythmic process of brightening and dimming. Leavitt's genius was that she realized that by comparing the size of Cepheid variables in different parts of the sky, you could calculate their relative distance. They could be used as standard candles, a term she created and is still used today.
Hubble combined Leavitt's measurements with Vesto Slipher's redshifts and began to measure points in space with a new perspective. In 1923, he proved that the nebula in Andromeda was actually a galaxy, with 10,000 light years in diameter and was at least 900,000 light years away. The universe was bigger than anyone had imagined.
In 1924, Hubble wrote a paper called "Cepheids in Spiral Nebulae," using the word *nebula* to refer to galaxies, where he proved that there were numerous individual galaxies, some of which were much larger and more distant than our own.
This discovery alone would have made Hubble famous, but he then turned his attention to another question, and what he found next was even more remarkable. Hubble began measuring the spectra of distant galaxies, something Slipher had already started doing in Arizona. Using the new telescope at Mount Wilson, plus some clever reasoning, by the early 1930s, he had concluded that all the galaxies in the sky (except our own) were moving away from us. Moreover, their rate was directly proportional to their distance. The further away a galaxy was, the faster it was receding.
This was a shocking conclusion. The universe was expanding, quickly, and in every direction. You don't need much imagination to realize that it must have expanded from one center point.
As Stephen Hawking pointed out, it's strange that no one had thought about explaining the universe before. Newton and every astronomer after him should have realized that a static universe would collapse on itself. And if the stars were constantly burning in a static universe, it would make the whole universe unbearably hot. A constantly expanding universe instantly solved this problem.
Hubble was better at observing than thinking, so he didn't fully appreciate the significance of his discovery. In part, that's because he was woefully ignorant of Einstein's theory of general relativity. Which is interesting, because on one hand, Einstein and his theories were world famous by this time, and on the other hand, in 1929, Albert Michelson, by then an old man, accepted a position at Mount Wilson Observatory and could have mentioned to Hubble that Einstein's theory applied to his discoveries.
Regardless, Hubble didn't take the opportunity to gain any theoretical ground. He left it for Georges Lemaître, a Belgian priest and scholar. Lemaître combined theory with practice, and created a "fireworks theory." This theory claimed the universe began as a geometric point, a "primeval atom," that exploded. This was a good sign for the modern Big Bang theory, but it was way ahead of its time. So, Lemaître didn't get very far.
Neither Hubble nor Einstein are mentioned in the great news headlines. Nevertheless, they had made their contribution, even though they didn't know it.
In 1936, Hubble wrote a popular book called *The Realm of the Nebulae*. In this book, he finally showed that he knew about Einstein's theory, even if it was just 4 pages out of 200.
Hubble died of a heart attack in 1953. Yet, there was one last oddity waiting for him. For undisclosed reasons, his wife refused to hold a funeral, and never revealed what she did with his remains. A half-century later, the whereabouts of the greatest astronomer of the century remains unknown. To commemorate him, all you can do is look toward the sky, towards the Hubble telescope.