Advent Calendar of Science Stories 12: Time Tables

Returning to our mostly-chronological ordering after yesterday’s brief excursion, we come to one of the great problems of the 1700’s, namely determining the longitude at sea. Latitude is easy to find, based on the height of the Sun at noon– we told that story last week— but longitude is much trickier. Thanks to the rotation of the Earth, the best way to measure longitude is by measuring time– if you know what time it is where you are, and what time it is at some reference point (now established as Greenwich, UK), the difference between those times tells you the difference in longitude.

This is relatively easy to do on land, but making a system capable of tracking the time difference on a moving ship at sea was an extremely difficult problem. It was, of course, finally cracked by a lone genius working in…


And, OK, I skewed the presentation of that a little just to mess with Thony C. He wasn’t really a lone genius, and he’s not really famous. I’m talking about Tobias Mayer, a young German astronomer and mathematician whose observations made it possible to implement the “method of lunar distances” on a practical scale.

To modern people, accustomed to cheap and reliable timekeeping, the solution to the longitude problem seems obvious: just carry a clock with you. In the 1700’s, though, that was an awfully hard thing to manage, because mechanical clocks were a new and not entirely reliable technology. And while the clockmaker John Harrison did eventually crack the problem, it required almost superhuman effort, and the necessary clocks remained expensive and difficult to maintain for many years to come.

There’s another way to measure the time where you are, though, which is through astronomy. As the Moon moves across the sky, it’s visible more or less everywhere on the dark side of the Earth at the same time. Most of the Moon’s motion is just the rotation of the Earth, but as it moves in its orbit, it changes position relative to the background pattern of stars– not by a huge amount, but by enough over the course of a single night to serve as a useful method of establishing time. If you know that the Moon as seen from London will pass directly in front of a particular bright star at precisely midnight in London, and you see it pass that star at 10pm where you are, well, you’re two hours west of London, or about 30 degrees of longitude.

For this to be a useful method, of course, you need to know exactly where the Moon will be at various times in the future. Which is doable in principle, but actually pretty complicated, due to all the various forces that tug on the Moon in its orbit. Predicting the position of the Moon with sufficient accuracy to be useful for navigation defeated a lot of great scientists, due to the complexity of the calculations from Newton’s law of gravitation.

Mayer finally cracked it not with any spectacular new technique, just a series of improved observations of the orbit of the Moon over a period of several years. This gave him an exceptional empirical model of the orbit, allowing prediction of the Moon’s position well enough to find the time within a few minutes. Sadly, Mayer died young, of typhoid, but in recognition of his achievement his widow was granted three thousand pounds from the Board of Longitude, a very substantial sum of money.

Mayer’s method was still fairly complex, requiring calculations by a trained astronomer, and making it practical for use by seamen took a further refinement. This was done by Neville Maskelyne at the Royal Oservatory, essentially doing a lot of the more complicated calculations in advance and producing a simplified table. These tables were printed and distributed to ships, and became the first large-scale practical method of determining longitude at sea. Comparable tables are still generated– by the US Naval Observatory, for example– and used for celestial navigation. Nowadays, we have reliable clocks and GPS, but the methods developed by Mayer and Maskelyne can provide a fallback option for times when the batteries run out.

John Harrison and his clocks (and his pissing contest with Maskelyne and others over whether he should get the Longitude Prize) make for a better story in that they involve dramatic new technological inventions– bimetallic strips! novel escapements! diamond chips for reduced friction! Mayer’s less glamorous story is important as well, though, because it’s a reminder that science isn’t always dramatic “Eureka!” moments and sudden breakthroughs. Sometimes, great advances are made simply through dogged persistence and careful, patient observations. That might not sell a lot of books two hundred years later, but it saved an awful lot of ships at sea, which is a pretty damn good legacy.

(Part of a series promoting Eureka: Discovering Your Inner Scientist, available from Amazon, Barnes and Noble, IndieBound, Powell’s, and anywhere else books are sold.)

(Featured imaged from this astronomy page.)

The Problem of Science Stories

Last week Kate pointed me to this post about heroic stories of science saying “This seems relevant to your interests.” And, in fact, a good deal of the post talks about Patricia Fara’s Science: A Four Thousand Year History, the Union library’s copy of which is sitting on my desk, where I had looked something up in it just that morning. (Specifically, the part where Fara notes that the distinction between “science” and “technology” is largely a class-based fiction, dividing high-status philosophers from grubby practical mechanics.)

There are a bunch of things going on in this, and most of them are, indeed, relevant to my interests, as Eureka: Discovering Your Inner Scientist is largely a book of stories about science. Which will most likely fall in the “Sobel Effect” zone of an article cited in the post, being too simplistic and explicitly promotional for a lot of professional historians. It’s even been explicitly compared to Sobel’s work (by Library Journal), and I’m happy to have that pull quote on the Amazon page.

There’s also a bit of truth to the claim that these books take a skewed view of history. I’ve worked pretty hard at trying to make the stories in the book as accurate as I can, but the ultimate purpose of the book isn’t to be a complete and accurate piece of historical scholarship. I’m explicitly trying to promote science in general, and that necessarily involves being selective about the stories I choose to tell, and how I tell them (even if that causes me some angst). I got a good comment on my video about Darwin noting that I didn’t mention Alfred Russel Wallace, and that’s correct, because adding the story of Wallace would complicate matters and risk obscuring the point I really care about. (There’s a mention of Wallace in the book, but it’s very short…) It’s a good story, and might show up later this month on the blog, but it doesn’t serve my purpose to tell that story in that place.

But I chafe a bit at the implication, less in the blog post than in the “Sobel effect” article, that advocacy for science is fundamentally unserious and unworthy of real academics. That strikes me as just as problematically artificial as the science-vs-technology distinction I was looking up in Fara’s book.

The past is too huge to present in complete detail, so ultimately anybody who writes about it is making a choice about what sort of story to present. Telling the story of Wallace and Darwin and putting it in the proper context of class and social status and all that is one way to come at the story of evolution, and can make a number of important political points. But that’s a particular choice of story, serving a particular end, and it’s not intrinsically any better than a more streamlined treatment of events that aims at making a different point.

The notion that the only appropriate approach to history is through the lens of identity and social constructivism is a political stance, not anything inherent in the subject. The suggestion that there’s something inherently wrong with using a positive slant on history to promote science is the kind of corrosive nonsense that sometimes makes me want to get out of academia altogether.

Now, of course, there are limits. There’s a line beyond which simplifying the story tips over into being actively deceptive. As Thony describes, there’s a good case that Sobel’s most famous book crosses that line, and I try to talk about that when I teach it. The story of the Harrisons is very compelling, but the almost superhuman effort required to make those watches is itself a good argument that they weren’t really the solution to the longitude problem. Maskelyne’s lunar distance method was ultimately more practical, and continues to be taught and used well into the modern era of cheap and accurate mass-produced chronometers. Leaving that stuff out of the story changes things in a way that’s deeply problematic, and we should do better than that when communicating science with history.

At the same time, though, given the power narrative has to connect with people (see, for example, Jonathan Gotschall’s book arguing for storytelling as the fundamental human trait), it would be crazy not to use historical narratives as a tool for communicating science. The stories we tell about science are a powerful tool for drawing people in– the post about my timekeeping class includes a video from James Burke’s Connections series, which presents a highly simplified version of the history of science, but also made a big impression when I saw it back in the 70’s.

So, the trick is to find just the right balance between including enough complexity to avoid being deceptive while keeping the story simple enough to be useful. In the end, I always come back to the notion of lies-to-children, namely the simplified versions of how things work that we tell to those who aren’t yet ready to deal with the complexity of the full story. In the same way that we teach first-year students Newton’s Laws before Lagrangians because they’re not ready to handle the math, I think it’s reasonable to tell non-scientists a simpler version of the origin of evolution, as a way of priming them for a more complete treatment somewhere down the road.

That line between lies-to-children and actual lies is going to be an individual thing, though, both for the writer and the reader. I’ve done the best I can to be both accurate and engaging in Eureka, but I’m sure there will be people who feel I’ve distorted some of the stories in it. And there’s really not a lot I can do about that; in the end, I think losing a few people that way is a sacrifice worth making in order to use stories to connect with a broader audience.


If you’d like to judge for yourself whether I’m guilty of abusing history, Eureka: Discovering Your Inner Scientist is available from Amazon, Barnes and Noble, IndieBound, Powell’s, and anywhere else books are sold…

Advent Calendar of Science Stories 11: Feynman’s Plate

I’ve been trying to keep to a roughly chronological ordering of these stories, but this slow-motion snow storm that was waiting to greet us on our return from Florida made the schools open on a two-hour delay today, which eats the time I usually use for blogging and books stuff. So I’m going to jump forward three hundred years, to a story that I can outsource.

To set the stage, in the aftermath of WWII, Richard Feynman took up a faculty job at Cornell, but between working on the Manhattan Project and the death of his beloved wife, he found that he was completely burned out, and not able to do much useful work. Then, as he relates in his autobiography:

So I got this new attitude. Now that I am burned out and I’ll
never accomplish anything, I’ve got this nice position at the university
teaching classes which I rather enjoy, and just like I read the
Arabian Nights for pleasure, I’m going to play
with physics, whenever I want to, without worrying about any importance

Within a week I was in the cafeteria and some guy, fooling around,
throws a plate in the air. As the plate went up in the air I saw it
wobble, and I noticed the red medallion of Cornell on the plate going
around. It was pretty obvious to me that the medallion went around
faster than the wobbling.

I had nothing to do, so I start to figure out the motion of the rotating
plate. I discover that when the angle is very slight, the medallion
rotates twice as fast as the wobble rate – two to one [Note: Feynman mis-remembers here—the factor of 2 is the other way]. It came out of a
complicated equation! Then I thought, “Is there some way I can see in a
more fundamental way, by looking at the forces or the dynamics, why it’s
two to one?”

I don’t remember how I did it, but I ultimately worked out what the motion
of the mass particles is, and how all the accelerations balance to make it
come out two to one.

I still remember going to Hans Bethe and saying, “Hey, Hans! I noticed
something interesting. Here the plate goes around so, and the reason it’s
two to one is …” and I showed him the accelerations.

He says, “Feynman, that’s pretty interesting, but what’s the importance of
it? Why are you doing it?”

“Hah!” I say. “There’s no importance whatsoever. I’m just doing it for
the fun of it.” His reaction didn’t discourage me; I had made up my mind
I was going to enjoy physics and do whatever I liked.

I went on to work out equations of wobbles. Then I thought about how
electron orbits start to move in relativity. Then there’s the Dirac
Equation in electrodynamics. And then quantum electrodynamics. And before
I knew it (it was a very short time) I was “playing” – working, really –
with the same old problem that I loved so much, that I had stopped working
on when I went to Los Alamos: my thesis-type problems; all those
old-fashioned, wonderful things.

It was effortless. It was easy to play with these things. It was like
uncorking a bottle: Everything flowed out effortlessly. I almost tried to
resist it! There was no importance to what I was doing, but ultimately
there was. The diagrams and the whole business that I got the Nobel Prize
for came from that piddling around with the wobbling plate.

I thought of this for today because it came up yesterday on the radio. One of the callers asked a really good question, namely “How do you maintain an interest in science over the course of a long career studying difficult problems?” And, happily for me, I thought of this Feynman story, because one good way to keep going is to just keep playing with stuff.

You don’t always have to be beating your head against the biggest, most difficult questions– sometimes, great stuff comes out of playing around with little problems. Like the question “What is the relationship between the wobble and the spin of a thrown plate?”

Of course, not every playful investigation is going to lead to QED and a Nobel Prize, but even if it does turn out to be unimportant from a physics standpoint, playing with these things can be tremendously rejuvenating. Playing around with sticky tape earlier this year was tremendously helpful to me, not because it led anywhere professionally (though I may yet write an AJP article about that stuff), but because it was fun, and helped me maintain my interest in doing what I do.

So, the story of Feynman and the spinning plate is a useful reminder of the importance of noticing the little things around you, and keeping a playful attitude. Keep looking and thinking and asking questions, because even if they don’t lead anywhere directly useful, they help keep you energized and engaged.


(Part of a series promoting Eureka: Discovering Your Inner Scientist, available from Amazon, Barnes and Noble, IndieBound, Powell’s, and anywhere else books are sold.)

(Cornell china plate image from Collectable Ivy. This isn’t the same kind of plate Feynman was talking about, but it’s what Google came up with in the short time I had to devote to this.)

Eureka: Discovering Your Inner Scientist: Release Day!

Today is the official release date for Eureka: Discovering Your Inner Scientist, so of course there are a bunch of exciting things happening:

— There’s a short excerpt at the Science of Us blog from New York Magazine. This is a chunk of the Introduction, about how scientists are smart, but not that smart.

— I wrote a Big Idea essay at Whatever, talking about how this book is about the BIGGEST idea in the history of humanity. Which is only a tiny bit of hyperbole.

— Rosemary Kirstein included Eureka as a gift suggestion, which is very cool, as she writes awesome books. You should check them out.

— Union’s director of communications wrote a nice news piece on the book (full disclosure: I play basketball with him regularly…).

— A review from Rhett at Dot Physics.

Also, I will be on Think tomorrow afternoon (well, noon Central time, 1pm Eastern) talking about the book. And I’ll be signing books Sunday from 12-1:30 at The Open Door in Schenectady. Other fun stuff is in the works, and details will be posted when available.

Advent Calendar of Science Stories 9: Newton’s Bodkin

I tooke a bodkine gh & put it betwixt my eye & [the] bone as neare to [the] backside of my eye as I could: & pressing my eye [with the] end of it (soe as to make [the] curvature a, bcdef in my eye) there appeared severall white darke & coloured circles r, s, t, &c. Which circles were plainest when I continued to rub my eye [with the] point of [the] bodkine, but if I held my eye & [the] bodkin still, though I continued to presse my eye [with] it yet [the] circles would grow faint & often disappeare untill I removed [them] by moving my eye or [the] bodkin.

If [the] experiment were done in a light roome so [that] though my eyes were shut some light would get through their lidds There appeared a greate broade blewish darke circle outmost (as ts), & [within] that another light spot srs whose colour was much like [that] in [the] rest of [the] eye as at k. Within [which] spot appeared still another blew spot r espetially if I pressed my eye hard & [with] a small pointed bodkin. & outmost at vt appeared a verge of light.

— From the notebooks of Isaac Newton, via the Cambridge University library

Mark Twain famously wrote that “Truth is stranger than fiction, but it is because Fiction is obliged to stick to possibilities. Truth isn’t.” This is why today’s story relies on the actual words of its subject, rather than me trying to write a scene in which a young Isaac Newton sticks a knife in his own eye.

The text and image above come from a notebook in which Newton recorded his thoughts and experiments around 1665. He was doing a lot of playing around with optics at the time, and investigating the ways we perceive color. Not one to leave a stone unturned when he could wedge a sharp bit of metal underneath it and lever it over, he investigated the effect of physical distortion of the eye both by pressing on the front of his closed eyeball, and also by working a bodkin up behind his eye, and pressing on the back of it. I’m not sure whether he used himself as a subject because he didn’t trust the observations of others, or because he was naturally a solitary and secretive sort. Or, possibly, all his friends fled when he started suggesting sticking sharp objects in uncomfortable places…

Anyway, this story stands as a sort of testament to the crazy shit that scientists have gotten up to over the last umpteen millennia. Newton is far from the only scientist to experiment on himself– particularly in the early days of the Royal Society, they got up to all sortsof weird stuff. But this continues for quite a while– Bill Bryson’s A Short History of Nearly Everything has a bunch of these stories, including one chemist who insisted on tasting everything he worked with (possibly Carl Wilhelm Scheele, but I don’t have the book here with me).

Like most modern scientists, I don’t really this kind of self-experimentation (or the sticking of sharp objects in the eyes of others, for that matter). At the same time, though, this kind of obsessive dedication to figuring things out no matter what is sort of perversely admirable. And while this is frequently presented as a “look at what a weirdo Newton was” tale, it’s actually a very human thing to do. Newton sticking a bodkin in his eye comes from the same kind of impulse that leads athletes to play through injuries, or artists to sacrifice personal comfort in pursuit of some particular vision.

So, a tip of the cap (from well out of dagger range) to Isaac Newton and all the other scientists down through the years who have gone past the normal bounds of common sense in pursuit of answers.


(Part of a series promoting Eureka: Discovering Your Inner Scientist, available from Amazon, Barnes and Noble, IndieBound, Powell’s, and anywhere else books are sold.)

Eight Things You Need to Know About Science

Copies of Eureka: Discovering Your Inner Scientist have been turning up in the wild for a while now, but the officially official release date is today (available from Amazon, Barnes and Noble, IndieBound, Powell’s, and anywhere else books are sold). To mark that, here’s some stuff I wrote about the core message of the book, presented in Internet-friendly listicle form:

Eight Things You Need to Know About Science

1) Everybody Is a Scientist: Most people picture scientists as remote eggheads, who think in ways that ordinary people can’t comprehend, but the reality is very different. Scientists are not that smart, and ordinary people use scientific thinking all the time—in fact, every time you play cards, or sports, or even a video game like Angry Birds, you’re thinking like a scientist.

2) Science Is a Process: The basis of all of science is a simple four-step process: you Look at the world around you, you Think about why it might work that way, you Test your theory with experiments and observations, and you Tell everyone you know the results of the test. This is exactly the process you use in videogames: you look at the arrangement of pigs and blocks, you think about which block you should hit with which bird, you test your theory by launching birds, and if it works, you brag to your friends about how you cleared the level. It’s a process that’s part of everything we do.

3) Stamp Collecting and Biology: The scientific process starts with collecting observations about the world, in exactly the same way that people collect stamps, or coins, or rocks. And this can be crucial to scientific discovery. Charles Darwin wasn’t the first person to come up with the idea of evolution—his own grandfather was promoting evolutionary ideas sixty years before On the Origin of Species—but Charles became an icon of science because his theory was backed by mountains of evidence, collected over years of careful observation, a piece at a time, like so many stamps.

4) Card Players and Astronomers: Astronomers tell us that we’re surrounded by vast amounts of “dark matter” that we can’t see, five times as much as the matter we do see. This sounds downright crazy, but astronomers like Vera Rubin detected it through the same reasoning process used by a good card player. They used tiny clues in the light that we do see, together with knowledge of the laws of physics, to prove the existence of dark matter in the same way that a good bridge player figures out who’s holding the ace of spades without ever seeing the other players’ cards.

5) Jocks Are Nerds: The stereotype of athletes is basically the polar opposite of scientists: physically gifted, but not too bright. This couldn’t be farther from the truth—in fact, there are few activities more ruthlessly scientific than competitive sports. Success on the playing field demands constant thinking: making a mental model of what the other players will do next, which is then immediately tested, and refined for the next play. A major sporting event is several hours of high-speed science on display, and the winner will be the team that did the best job of thinking like scientists. This process of repeated making, testing, and refining of models is at the heart of science, and the same rapidly repeated process powers the atomic clocks that make GPS navigation possible.

6) Science Is Social: Movies and comic books are full of lone geniuses, great scientists whose lack of people skills force them to work alone. In reality, though, science is an intensely cooperative and social activity. Great scientists are almost always great communicators, and some of the most successful theories in modern science succeed because they tap into our love of story. And scientific discoveries always come from teams of scientists working together, whether in lab groups about the size of a basketball team, or the thousand-member collaborations that discovered the Higgs boson at the Large Hadron Collider. Collaboration and communication are essential to success in science.

7) Science Is What Makes Us Human: The institutions of modern science are a recent development, but the process of science is as old as humanity itself. As far back as we have evidence of humans, we see people doing science. Ancient monuments like Stonehenge and Newgrange show this process in action: Stone Age people looked at the world and notice the motion of the Sun across the seasons, they thought about how to use that pattern to predict the seasons, they tested their theory over years, and they told their descendants the results, passing them down through centuries. With this knowledge, they built monuments that still work perfectly to mark the solstices, five thousand years later.

8) Science Is For Everyone: All too often we’re told that science is an exclusive club—that only men, or Europeans, or rich people are capable of science. These are toxic misconceptions. Science is the heritage of every human, and great discoveries have come from people of every gender, culture, and background. The only thing you need to do science is curiosity and a willingness to employ the process: Look at the world around you, Think about why it works that way, Test your theory, and Tell everyone what you find. It’s a process that we use every day, in hobbies and games. If we recognize that, and make more conscious use of the process of science, we all have the ability to improve our knowledge of the universe, and use to make the world a better place.


(Like this? Want to read more? Eureka: Discovering Your Inner Scientist is available from Amazon, Barnes and Noble, IndieBound, Powell’s, and anywhere else books are sold…)

Eureka: Bridge to Dark Matter

The first time you hear about dark matter, it sounds kind of crazy– asserting that we’re surrounded by tons of invisible stuff is usually a good way to get locked up. But the process of its discovery is surprisingly ordinary: it’s just what you do when you play cards.

Here’s the second green-screen video I’ve done to promote Eureka: Discovering Your Inner Scientist, which comes out three weeks from tomorrow (but can be pre-ordered today!). This one is about card games, modern astrophysics, and why you probbaly shouldn’t play bridge against Vera Rubin:

For those who dislike video, I’ll put the approximate text at the end of this post. This is, of course, a shortened version of a longer argument from the book. This benefits enormously from images and data provided by Becky Koopmann, one of my astronomer colleagues at Union.

Because I get to use these to cross-promote stuff that I like, I threw in a great Surviving the World Comic, and by a weird coincidence, ended up wearing a T-shirt with that same slogan on it (the first time I recorded video, I had an astronomy-themed shirt, but the camera glitched and didn’t record any audio, so we had to re-shoot). And, of course, there are cute-kid photos…

There’s a third video in the works, but probably not next week because of work and Thanksgiving. Unless I get really inspired and it comes together awfully quickly. And, of course, if you like this please consider buying the book, which has more on this story, and many others like it….


If you follow science news at all, it seems like every week astronomers announce the discovery of some amazing new thing: unusual stars, planets around those stars, giant black holes, even whole new galaxies. But here’s the most amazing part: for every new bit of matter astronomers see through their telescopes, there’s five times as much stuff out there that we can’t see. It’s called “dark matter,” and we have no idea what it is.

That might seem incredible—after all, insisting that you’re surrounded by lots of invisible stuff is a great we to get yourself locked up. So how can this be science? What could make astronomers think there’s all this invisible “dark matter” running around?
The answer is surprisingly mundane. Astronomers discovered that dark matter exists by using the same skills you use to play cards.

I don’t mean that they’re lucky, or the whole thing is a big bluff. I’m talking about the process a good card player uses to figure out the cards held by the other players, particularly in a game like bridge.

Bridge is one of the world’s most popular card games, and what sets it apart from other games is the “bidding” process. A game opens with the players taking turns offering a number, and a suit—two clubs, three hearts, four spades. The suit is what they want to be trump, and the number is how many tricks they think they can win, together with their partner.

Now, predicting how many tricks two of you can win together would be a lot easier if you know your partner’s cards. But you can’t just look at your partner’s hand, or even ask them what they have. Instead, you have to figure it out from the bidding, using a complicated set of “conventions” about what you should bid given what cards you have. It’s a tricky and indirect process, but it works. A good bridge player who knows the conventions will start the game knowing almost exactly which cards each other player is holding, just from the pattern of bids.

Astronomy is a lot like bridge. Astronomers want to know what’s going on in distant parts of the universe, but as much as they might like to, they can’t go there to investigate. All they can do is look at the light that reaches Earth. Astronomers can ask two questions—“How much light?” and “What color is the light?”— so they’re a little better off than bridge players, but only a little bit.

But like bridge players, they have conventions they can use—in this case, the laws of physics. Knowing the laws of physics lets them get an incredible amount of information out of those two questions. Because they know the physics of how stars operate, they can use the total amount of light to determine the distance to certain types of stars. More distant stars appear fainter, and if you know how much light it emits, and how much you detect, you can figure out how far away it is. This lets astronomers map the universe, all the way out to distant galaxies billions of light-years away.

The real goldmine, though, is asking what colors of light we see coming from a distant object—its spectrum. Quantum physics tells us that atoms emit light only at certain very special frequencies, and each element in the periodic table has its own unique pattern of frequencies. So looking at the spectrum of a distant star can tell you exactly what it’s made of.

More than that, though, the spectrum of a distant object tells you how it’s moving. This is because of the Doppler effect: waves emitted by a moving source shift their frequency depending on their velocity. That’s responsible for the “eeeeee-owwwww” sound of a fast moving car going past. As it approaches, the car catches up to the sound waves it already emitted, and the sound shifts to shorter wavelengths, and higher frequency. As it recedes, it “runs away” from the earlier waves, and shifts to longer wavelengths and lower frequencies. The same thing happens with light: if an object is moving toward us, we see the light shifted toward the blue, and if it’s moving away, we see the light shifted toward the red.

The Doppler shift is what tells us that the universe is expanding. It’s als one of the keys to dark matter. Some of the best and most important evidence was first measured by the astronomer Vera Rubin, who has spent about sixty years using the Doppler effect to measure the motion of galaxies.
She started in the 1950’s, looking at the motion of whole galaxies, and groups of galaxies, but in the late 1960’s, she turned to looking at motion within galaxies. When we look at a rotating spiral galaxy, the stars on one side are moving toward us, and have their light shifted to the blue, while the stars on the other side are moving away and shifted to the red. The difference tells us how fast the galaxy is rotating, at different distances from the center.

This is a very tricky measurement, because the light from a galaxy is very faint, but one of Rubin’s colleagues, Ken Ford, had invented a new type of spectrometer that made it much easier. So Rubin and Ford started looking at rotating galaxies, and they found something amazing. They saw the rotation they expected, with stars on opposite sides of the center of the disk moving in opposite directions, but as they looked farther out from the center, the speed stayed the same.

This was shocking, because they expected the rotation speed to decrease farther out, for the same reason that the outer planets in our solar system move slower than the inner ones. The farther you go from the Sun, the weaker its gravity. The force just isn’t strong enough to hold a fast-moving planet in a big orbit. The same thing should happen with galaxies: at the outer edge, where you run out of stars, there shouldn’t be enough gravity to keep fast-moving stars in orbit. But Rubin saw fast-moving stars as far out as there was light to see. The only way this can happen is if there’s a huge amount of other matter there, five times as much as the stars that we see, providing the extra gravity.

When Rubin first reported this, everybody thought it must’ve been a mistake. So she measured another galaxy, and saw the same thing. And another. And another. Other people measured more galaxies, and saw the same thing. Other bits of evidence started to accumulate, as well, all of it pointing in the same direction: for every bit of matter we see through a telescope, there’s five times as much dark matter. It doesn’t produce light, but we know it must be there because its gravity leaves an imprint on the light we do see. Combining the spectrum we see with knowledge of the laws of physics leads inevitably to dark matter in the same way that combining the bidding history with the conventions tells a good bridge player what’s in their partner’s hand.

I tell this story not just because dark matter is weird and cool—which it is—but because it tells us something important about the nature of science. Ideas like dark matter are so strange and improbable that it may seem like scientists must be making them up just to mess with your head.

But science isn’t weird and arbitrary like that. At its core, science is a surprisingly ordinary process: you look at the world, you think about why it might work that way, you test your theory with further observations, and you tell everyone about it. This process is as old as humanity itself, and something we all use, all the time. It’s what you do any time you decide to relax by playing a few hands of bridge: you look at the bidding history, you think about what it tells you about the other players’ cards, and you test your theory by playing the game. And, if you win, you brag about it to all your card-playing friends.

Modern science is full of amazing things that we can’t see directly, but know have to be true. From the outside, these might seem like they arrive out of nowhere, as if by magic. But then again, so does bridge, if you don’t know the process. When you put it all together, discovering dark matter is no more magical than figuring out who’s holding the ace of spades.

Eureka: Quantum Crosswords

My new book comes out one month from yesterday, or four weeks from tomorrow. Of course, yesterday was Sunday, and tomorrow’s a federal holiday, both lousy times for promotional posts, so I’ll drop this in today instead. Here’s a promotional video I put together, about how the history of quantum mechanics can be compared to working a crossword puzzle:

This is basically the talk I gave at TED@NYC last year, done in front of a green screen with slides edited in behind me for that An Inconvenient Truth vibe (Nobel committee, take note…). With some bonus cute kid photos and an explicit reference to the book, which isn’t allowed at TED things.

I’ve got another of these ready to upload, and will be shooting a third at some point, to give you a couple more examples of the central argument and some further cool science. If you like it, I’ve got a whole book worth of this you can buy. Well, pre-order at this point, but four weeks from tomorrow, look for it wherever books are sold…

The Copernicus Complex by Caleb Scharf

I enjoyed Caleb Scharf’s previous book, Gravity’s Engines a good deal, so I was happy to get email from a publicist offering me his latest. I’m a little afraid that my extreme distraction of late hasn’t really treated it fairly, but then again, the fact that I finished it at all in my current state of frazzlement may be the best testament I can offer to its quality. This is a sweeping survey of what we’ve learned about our place in the universe over the last five hundred years or so.

Now, a grandiose description like that often portends a bunch of wifty philosophizing that poses grand questions but doesn’t answer any. Happily, Scharf’s book is largely free of that– it’s not that he actually has concrete answers for questions about the origin of life in the universe, but he resists the worst sort of speculation, and grounds everything in solid modern science.

In fact, if anything, it’s a bit anti-philosophical, starting with the title. Scharf spends a good deal of time arguing against more extreme versions of the Copernican principle, the idea that the Earth isn’t special. This is one of those meta-scientific ideas, like Occam’s Razor, that are perfectly sensible in a simple form, but are sometimes stretched well beyond their natural domain, as if they were built into the very structure of the universe.

The mis-application of the Copernican principle that Scharf argues against is the idea that the Earth has to be perfectly mediocre, unexceptional in every regard. You’ll sometimes hear this trotted out in arguments that there must be bazillions of inhabited planets out there, just like Earth, and therefore we need to spend more on the favored space exploration schemes of whoever’s talking. Scharf dismantles this line of thinking with a clear and thorough survey of modern astronomy, showing that the Earth is, in fact, special. Our Sun isn’t an average star, but a type that’s a little bit unusual. Our solar system, with rather circular and relatively stable orbits, looks unusual when compared to the many exoplanet systems that have been discovered– we don’t even have any examples of the most common planet types we’ve seen around other stars. And Earth itself is a little unusual, with our large Moon stabilizing the rotation axis. Given what we now know about astronomy, there are lots of ways in which the Earth is, in fact, special.

At the same time, though, he’s careful not to go too far the other way, into asserting that our uniqueness indicates that life is exceedingly improbable and therefore rare. After all, as he points out, everything is unique in some sense. If you flip a fair coin twenty times, writing down the sequence of heads and tails, the resulting string will be literally one in a million (1,048,576, if you want to get pedantic). But that’s true of absolutely any string of coin-flips– they’re all unique. Similarly, any life-bearing world out there will have a large number of features that make it unique, and would allow alien bloggers to hold forth about the improbability of such a combination occurring elsewhere. Just as the improbability of a particular string of coin-flips doesn’t tell you all that much about the general operation of flipping coins, the contingent factors associated with our particular brand of life don’t tell us all that much about life in general.

The main weakness of the book isn’t a weakness of the book itself, but the underlying science. Scharf goes through as much detail as he can about what we can say about the conditions for life and the possibility of life elsewhere, but it’s necessarily an incomplete picture. We don’t yet have enough information to make many sensible statements about what’s really going on with life in the universe, and that constrains what he can do with this book. But he does muster a good argument that we’re really close to having enough information to address these questions in a concrete manner, thanks to ongoing developments in exoplanet searches and robotic probes and all that sort of thing. It’s a fun time to be in science.

This is, in many ways, a book that’s pitched just right for me. It engages in speculation about some fun subjects, but it’s appropriately constrained speculation, with Scharf looking askance at the more excessive sorts of speculation in a manner I find very congenial. If you’re an enthusiastic follower of the wilder sort of Fermi paradox/ anthropic principle/ “rare Earth” stuff that’s out there (or an “Ancient Aliens” theorist, for that matter), you won’t find much to like. But if you want a compact and engaging survey of what we actually know about the possibilities involved with life in the universe, this is an excellent read.

Eureka: “Fun, Diverse, and Accessible”

The exciting news of the week: Eureka: Discovering Your Inner Scientist has gotten a starred review in Publishers Weekly. Woo-hoo!

They’ve said nice things about my previous two books, but getting the star is a big deal. And it’s a really good capsule description of the book, with a great pull quote in the last sentence:

This fun, diverse, and accessible look at how science works will convert even the biggest science phobe.

Really, I can’t ask for better than that.

I found out this was coming at the end of last week, where it was an absolute life-saver after some sanity-threatening stuff that I can’t talk about. I didn’t see the actual text until last night when Google alerted me that it had been posted, though, while I was on the verge of dozing off in front of the tv after another exhausting week. So this one review significantly boosted two weekends…

And with that, I’m off to take The Pip to soccer, then drive down to NYC where I’m going to see the reunited Afghan Whigs play the Beacon Theater tonight. So, here, have an atypically upbeat Whigs song (a cover, actually, but a sentimental favorite):

I say again: woo-hoo!