Episode 12 of my podcast is here—my review of Copernicus’s De Revolutionibus. Click below to listen:
This is part of a series on New York City museums. For the other posts, see below:
There is no place in New York City to which I have a more intimate connection than the American Museum of Natural History. I practically grew up inside its walls. For a nerdy boy on the Upper West Side, it was the perfect place for a weekend outing. My mom recalls taking me there and letting me run around in the big Hall of Ocean Life, while she enjoyed a beer at the refreshment stand. (They do not sell beer anymore.) My dad took me plenty of times, too, and then followed up the visit with a meatball subway sandwich.
Kids still love the museum. The natural world, after all, is far more accessible than the highfalutin world of art. A child who is still figuring out the basics of the world around her has no need of elaborate images to reconnect her to her senses. And it is fortunate for our society that the museum is so accessible to children. Judging from the case of Carl Sagan, Stephen Jay Gould, or Neil deGrasse Tyson (as well as myself) the fascination exerted on youthful visitors to the museum often matures into a fascination for the natural world and a respect for the power of human reason. And you do not need to be a child to feel this twin amazement at world without and the intelligence within. I feel it every time I visit.
You can enter the museum from several spots. The grandest is, without a doubt, through the Roosevelt Rotunda on Central Park West. When walking up the stairs, the visitor will notice the heroic equestrian statue of President Theodore Roosevelt. It is worth pausing to continue this statue, for it encapsulates much of the controversial history of the institution. The mustachioed man is flanked by a Native American and an African man, both on foot, and both looking rather dejected to my eyes. The racial message is clear: the white man sits atop the lesser races. To its credit, the AMNH is acknowledging this imagery with a special exhibit, “Addressing the Statue.” I think this strategy is far preferable to the idea of simply removing it, since now the statue provides an opportunity for learning.
Theodore Roosevelt holds a special place in the history of the museum. His father was one of the museum’s founders, when it was still housed in the Arsenal Building of Central Park. The younger Roosevelt was himself an ardent naturalist, and we have him to thank for many of our country’s most beautiful national parks. But being a nationalist in those days did not mean what it means today. Roosevelt did an awful lot of hunting on behalf of the museum, providing some of the exotic animals that were later stuffed and mounted in the amazing displays. Our views on hunting big game and on racial differences have both, fortunately, evolved since then.
To thank the President for his support, the museum is studded with acknowledgements. The most extravagant of these is the massive mural painted by William Andrew Mackay, covering three tall walls of the Roosevelt Rotunda, where the visitor enters. These depict the eventful life of the naturalist president, turning him into a kind of secular saint on the walls of the cavernous room. But of course most people’s attention is absorbed by what is happening in the middle: the dramatic encounter between a brontosaurus protecting its calf, and the hungry allosaurus prowling for prey. Both the baby and the predator are dwarfed by the gargantuan form of the brontosaurus, whose already significant height is bolstered by standing on its hind legs. Personally I doubt that such a massive animal could perform such a maneuver without breaking its legs. Indeed, replica fossils had to be used, since the real fossils (made of stone, after all) are too heavy to mount in such a way.
Much as I would like to move on to the museum’s exhibits, there is one more relic from the museum’s past that deserves comment. Downstairs from the glorious Roosevelt Rotunda is the Roosevelt Memorial Hall, which includes four small exhibitions about the varied activities of the president: his interest in nature; his love of exploration; his time as a statesman; and his life as a writer. What draws most attention, however, is a diorama showing a meeting between Peter Stuyvesant—the Dutch leader of what later became NYC—and the indigenous Lenape people. Made in 1939, this diorama contains several omissions and inaccuracies that work in the Europeans’ favor, such as showing the Lenape almost nude. Again, to its credit, the AMNH has included annotations on the glass, pointing out several of these problems; and their website includes lesson plans to help visiting teachers use the diorama.
I am dwelling on these examples of the museum’s less noble past, not to portray the institution in a negative light, but to show that the museum is working to improve itself without burying its past. It is a model to imitate. And the museum has a long history. This year, 2019, marks the 150th anniversary of the institution. This makes the AMNH one year older than the Metropolitan, which was founded in 1870.
Now it is finally time to enter the museum. Luckily, the entrance fee is still a suggested donation for all visitors, so you need not break the bank. What should we see first? There is a great deal to choose from. In fact, the AMNH is the largest natural history museum in the world, with millions upon millions of specimens of animals, fossils, minerals, artifacts… It would be virtually impossible to see the entire thing in one day. For my part, it has taken me dozens of visits to fully wrap my mind around the museum; and even a lifetime would not suffice to learn all it has to teach.
Let us go on straight ahead from the Roosevelt Rotunda into the Hall of African Mammals. Simply as a work of art, this is one of the high points of the museum. In the center a herd of eight African elephants—bulls, cows, and calves—huddle together. Arranged around this heard, in little niches in the walls, are other exotic animals: lions, zebras, giraffes. The visitor would be forgiven for thinking that all of these were merely plastic replicas; but they are real taxidermied specimens of animals (one of the elephants was shot by Theodore Roosevelt himself). This gives the dioramas a kind of macabre air, which is combined with melancholy when examining endangered species such as the rhinos and the gorillas.
Yet art intervenes to uplift this collection of exotic bodies into a thrilling exhibit. Every diorama is masterfully done: the animals stand in dramatic, lifelike poses amid an environment so scrupulously recreated as to be totally convincing. Added to this are the paintings on the curved surfaces enclosing the dioramas. These hand-painted backgrounds are worthy works of art in their own right: adapting perspective to the wall’s curvature in order to create a nearly seamless continuation with the scene in the foreground. The result is a strange blend of natural beauty and human invention, which is at turns convincingly lifelike and technically astounding. As I walked along from diorama to diorama, I felt like pilgrim visiting a church, walking around from chapel to chapel.
The lion’s share of the credit for this work goes to Carl Akeley, who participated in both collecting and mounting these specimens. Though this business of big-game taxidermy can seem to us in the present day as grim and barbaric, I think that Akeley deserves to be viewed as an artist of high ability. Creating compelling nature dioramas is no easy matter. It requires a naturalist’s eye for fact and a sculpture’s eye for form. To construct a compelling design that is, at the same time, true to nature, requires a special knack. Akeley was a master of it.
A kind of sister to this gallery is the Hall of Asian Mammals, also accessible through the Roosevelt Rotunda. This is a decidedly smaller space; and as the plaque on the wall informs us, the animals here are owed to a “Mr. Ferney” and a “Colonel Faunthorpe,” who made six expeditions into Asia to hunt these animals. Two Asian Elephants stand in the center of this gallery, slightly smaller than their African counterparts. This gallery originally contained a specimen of a giant panda and a Siberian tiger, but the subsequent history of those species led the museum to place these in the Hall of Biodiversity as examples of endangered species (more later). On my latest trip, I learned that there is a type of Asian Lion with a rangy mane, which lives in a small sliver of India.
Now let us descend a flight of stairs once again to the Rockefeller Memorial Hall, on the ground floor. Here we can enter the space directly below the Hall of African Mammals: the Hall of North American Mammals. We find still more superb animal dioramas. The most famous of these is the Alaska Brown Bear. Two of these stand behind the glass. One is reared up on its hind legs, while the other prowls menacingly nearby. The height of the upright bear is startling. Standing before it, you feel how easily this creature could overpower you. Another superb display is of the moose, which features two bull moose jousting with their antlers. As a Canadian friend once told me, moose are the “king of the beasts.”
A quick trip through the Roosevelt Memorial Hall will lead us to one of the museum’s newer spaces: the Hall of Biodiversity. Opened in 1998, it did not exist when I was a young child. The room has a stunning design. Through the center is a swath of artificial rainforest, made to replicate one of earth’s most diverse environments. A legion of tentacled creatures hang from the ceiling, including a giant squid, an octopus, and a massive jellyfish. A glass case holds the giant panda and Siberian tiger, among others, as examples of endangered species; and the bones of the long-dead dodo can be found. Most of the action takes place on the far wall, which is illuminated from behind. Here is represented the entire panoply of life, from bacteria, to algae, to fungi, to plants, and finally to all the many variations of animals: worms, insects, crustaceans, mollusks, and vertebrates of every kind. (There is an online version that you can click through.)
The sheer abundance of models on display gives a visual illustration to the richness of life on this planet. This amazing variety, developed over 3 billion years of evolution, goes far beyond our humdrum ideas about plant and animal types. To give an example, once a teacher of mine asked everyone in class to make a guess at how many species of bee there are in the world. People’s guesses ranged between 12 and 300. The answer is 20,000. Unfortunately, this biodiversity is being dramatically curtailed through human action—which is why this gallery was made.
This attractive space opens up to what has always been, for me, the most dramatic room in the museum: the Hall of Ocean Life. Here is where I would spend most of my time as a child. This hall is one of the biggest spaces in the museum. It is dominated by the life-sized model of a blue whale, the largest animal to ever exist on the planet, hanging from the ceiling. This lightweight model weighs no less than 21,000 pounds—so just imagine what the real animal must weigh. It is frankly stupefying that something so large can be alive. The entire herd of elephants from the Hall of African Mammals can huddle underneath its belly.
Dioramas line the walls of both floors of this hall. The best of these are on the bottom, where you can find a polar bear, a pod of walruses, and a huddle of sea lions. Here, as elsewhere, these displays are amazingly dramatic and lifelike. We can see the sharks in pursuit of the poor sea turtle, and the dolphins jumping out of the water to catch some flying fish. But the real masterpiece of this hall is the battle between the sperm whale and the giant squid. The sperm whale is the biggest toothed predator in the world, and its prey is likewise large. This big-headed mammal dives deep under the water—sometimes over a mile deep, going more than an hour without breathing—in order to prey on the invertebrate monsters that lurk below.
The most notable foe of this whale is the giant squid, itself one of the world’s largest animals, capable of growing to over 40 feet in length. When a whale finally catches on of these squids, it must be a serious fight, as the suction-cup scars found on the hide of sperm whales attest to. The diorama evokes all the drama of this encounter. We arrive once the fight has commenced: the whale has one of the squid’s tentacles in its jaws, and the squid is wrapped around the whale’s enormous head. The diorama is illuminated in a semi-darkness that recalls the inky blackness of the deep ocean
As a child, I found this scene both fascinating and terrifying, and became obsessed. I drew the battle over and over, doing my best to perfect the two different forms: the smooth blue whale and the sprawling red squid. Even now, this conflict between the big-brained sperm whale and the monstrous giant squid calls to mind a deep conflict within our own nature.
This description only touches upon the strange, otherworldly beauty on display in the Hall of Ocean Life—a beauty that captivated me as a child and which still moves me. The world below the seas is more fantastic and alien than anything dreamed up in science fiction. You can see this clearly in the three dioramas depicting life in the ancient oceans: creatures whose bodies form spirals, cones, wings, prowling about on an ocean floor populated with blooming anemones. The colorful, twisting, bulbous forms of the coral reef also evoke this strange allure. A part of me has always wished to be a marine biologist.
Now we will leave the Hall of Ocean Life to travel back through the Hall of Biodiversity, to enter a space which I have still not adequately explored. The first is the Hall of North American Forests. This space is dedicated to the sorts of environments present in the United States and Canada, from the deserts of Arizona to the cold forests of Ontario. The most impressive object on display is a cross section from a 1,400 year-old Sequoia. It is enormous: big enough to serve as a dance floor or even to serve as the foundation for a house. Notable historical events are marked on the tree rings, going from the invention of book printing in China (in 600), to the crowning of Charlemagne (in 800), to the death of Chaucer (in 1400), to the ascension of Napoleon (in 1804), to when the tree was finally cut down, in 1891.
This hall is also notable for a diorama depicting the little critters who live in the soil, responsible for breaking down organic matter and keeping the cycles of life in swing. The worm, centipede, and daddy-long-legs are blown up to 24 times their actual size, which is not a pleasant sight. The same can be said for the giant model of a malarial mosquito, which does not increase my affection for that species. Teddy Roosevelt played a part in educating the public about the role mosquitos play in spreading malaria, since he had to deal with the disease when overseeing the Panama Canal.
When we leave this hall, we enter yet another of the museum’s grand entrance spaces. This is named, appropriately enough, the Grand Gallery. It is most famous for the hanging Great Canoe, made by the peoples of the Pacific Northwest. Carved from a single tree, this enormous boat can hold a dozen people and is suitable for use in ocean waves. The front features an exquisite painting of a killer whale. When I was a boy, I normally entered the museum here. At the time the canoe was filled with the plastic figures of Native Americans; and I would look at these mannequins with a kind of uncomprehending terror, since I could not figure out what those men were doing. The museum has since refurbished the canoe and removed the figures, hanging it higher so as to make the decoration more visible.
There are still other treasures to be found in this gallery. In one corner is a glass containing an ammonite fossil. This are extinct mollusks which looked like squids living in a spiral shell. This particular ammonite happened to fossilize under high pressure, which resulted in it being an iridescent rainbow. Nearby is a magnificent stibnite: a metallic crystal formed from antimony and sulfur. These crystals form themselves into a collection of jagged silver spikes all sprouting from a central core. A nearby child compared it to a porcupine.
The Grand Gallery normally leads to the Northwest Coast Hall; but it is currently closed for renovation. This hall is the oldest continued exhibit space in the museum, having been opened in 1900. The peoples of the Pacific Northwest are known throughout the world for the high quality of their visual art, including the iconic totem pole. This hall contained a great many of these poles, among other art, which made it one of the museum’s more beautiful spaces. Much of this was collected by the pioneering anthropologist, Franz Boas, during the famed Jesup North Pacific Expedition of 1897 – 1902. The current renovations are yet another example of the museum’s attempt to confront its past: updating the information to reflect how these cultures wish to be represented, rather than how anthropologists represented them 100 years ago.
The Grand Gallery also leads into the equally grand Hall of Human Origins. Opened in 1921, this hall was the first exhibit about the controversial topic of human evolution in the United States. The hall still performs this admirable task, teaching visitors about the evolutionary past of our own species. The visitor is first confronted with three skeletons, one of a modern human, one of a chimpanzee (our closest living relative), and one of a Neanderthal (our nearest extinct cousin). On the wall there are models of various primates, with their genetic similarity to humans shown underneath. Chimpanzees are nearly identical, with 99% similarity.
A major highlight are casts of famous human ancestor fossils, including Turkana Boy and Lucy. (I myself studied human evolution in the Turkana Basin, so it is always gratifying to see the plaque about the region.) There is also a reproduction of the Laetoli Footprints—imprints preserved in volcanic ash 3.5 million years ago, showing clear evidence of bipedalism—and a diorama of the what the two australopithecus may have looked like as they walked across the ashy plain (the male with his arm snuggly around his mate). There are also scenes representing the life of early humans, building shelters out of mammoth bones or being ambushed by giant hyenas. It was a tough life back in the paleolithic.
After moving through the Hall of Human Origins, you come to the Hall of Meteorites. This is most notable for containing a large chunk of the Cape York Meteorite. It is unknown when this iron meteorite struck the earth (near Cape York, in Greenland), though it was likely thousands if not millions of years ago. The original meteorite broke up into three large pieces, which were used by the Inuit living nearby to make iron tools. For decades Westerners searched for the mysterious source of iron (not easy to come by in the arctic), until Robert Peary, the explorer, finally found the meteorites and arranged for them to be transported and sold to the AMNH (likely without compensating the Inuit). The fragment displayed is so heavy that the foundations for the platform had to be built down to the bedrock below. It’s an awfully big rock.
The Hall of Meteorites normally leads to the Hall of Gems and Minerals. However, this hall is closed for renovations at the moment, which does not surprise me, since every time I visited the hall struck me as looking decidedly retro. The angular, geometrical design of the room (which appropriately mirrors that of a crystal) was praised highly when it was opened in the 1970s; but nowadays it looks very similar to how Kubrick imagined the future would be, in 2001: A Space Odyssey. Nevertheless, this is one of the most beautiful corners of the museum. The glass displays, arranged throughout the room, are filled with gleaming stones—gems which reflect and refract light in a thousand distinct ways.
(Visit here to see photos of the original gallery and concept drawings for the new gallery.)
This hall has a colorful history. Whenever I visit, I think that the hall looks like the kind of place Lex Luther would rob in order to get some kryptonite. Other people have had similar thoughts, it seems. In 1964, Jack Roland Murphy (“Murph the Surf”), with two accomplices, snuck into the museum and stole some of its most famous pieces: the Eagle Diamond, the DeLong Star Ruby, and the Star of India sapphire (all donated to the museum by J.P. Morgan). The thieves were eventually caught, and the jewels found and returned to the museum—the Star of India was found in a bus station foot locker—with the notable exception of the Eagle Diamond, which was likely cut into smaller pieces and sold. (Murph the Surf was later convicted for murder; in prison he became a minister and was released early; he is currently the vice president of the International Network of Prison Ministries.)
We have gone to the very end of the museum, but we have still left out one of the museum’s most notable wings: the Rose Center for Earth and Space. Opened in 2000 (so I did not see it as a child) this is the newest part of the museum, and it shows. The space-age design features a massive central sphere enclosed in a glass cube. The new Hayden planetarium is housed within this sphere, where visitors can see shows projected on the upper dome. Neil deGrasse Tyson is the first and, so far, the only director of the Rose Center; and he narrates many of the astronomical shows.
Below this “cosmic cathedral” (as the designer called it) is the Hall of the Universe. Here you can find information about stars, planets, galaxies, and the moon, all displayed on sleek metallic panels. There are scales that tell you what your weight would be on Mars and the Moon (in pounds, which requires a conversion for non-American visitors). In one clear glass case there is a self-contained ecosystem of algae and tiny shrimp—a microcosm that represents the macrocosm of earth. A curving walkway that leads away from the planetarium takes the visitor through the entire history of the universe, from the big bang to the present day.
The star of the hall is the Willamette Meteorite. This is another iron meteorite, yet it looks strikingly different from the Cape York Meteorite. Its surface is pockmarked—I believe from centuries of weather erosion. The rock has been on earth a long time. Possibly the core of an early proto-planet, smashed to smithereens in a cosmic collision, this meteorite struck earth thousands of years ago (but we have yet to be able to find the impact sight). It was found in Oregon, but it was likely moved by expanding and receding glaciers. As with the Cape York Meteorite, the Willamette Meteorite was taken without the consent of the native peoples who had long known about it. This led to a lawsuit, in 1999, by the Confederated Tribes of the Grand Ronde Community of Oregon, demanding the return of the rock (which had been in the museum for nearly 100 years by then). Luckily, the AMNH reached a deal that allowed it to keep the meteorite.
Adjoining the Hall of the Universe is the Hall of Planet Earth, devoted to geology. This gallery has accomplished the difficult job of rendering geology visible, tactile, and immediate. The space is filled with models of geological formations, many of which can be touched. These slices of earth help to illustrate the normally invisible processes below the surface which have shaped our planet—the slow churning of the continental plates, the effects of receding glaciers and running water, the volcanic explosions which hurl up new land from the depths. The hall also has a section devoted to climate change, which features an ice core (a piece of ice formed over thousands of years) which the visitor can “read” by moving a monitor over different sections, thus revealing how the climate has changed.
From what I observed, children love the Rose Center for Earth and Space. Everywhere I looked young kids were reading, looking, touching, laughing, and in general having a great time. To me this represents an accomplishment of a high order. Making whales and dinosaurs accessible to children is straightforward; but to make accessible the abstract theories of physics, the slow processes of geology, and the distant threat of global climate change—this calls for subtlety and skill, and the designers of this hall have accomplished their task with brilliance.
Now we must get to an elevator and ascend from the bottom to the top floor. We have dallied in the museum for a good, long time, and it will close soon, so we had better get to the spectacular fossil rooms on the fourth floor.
The proper place to begin is on the Orientation Hall. Here the visitor can see a video that explains some background of evolution and cladistics (making evolutionary trees). But the visitor will likely have difficulty focusing on this video, since in 2016 the museum added an enormous dinosaur to the room. This is the Titanosaur, a massive, long-necked sauropod whose form dominates the space. From tail to head, the animal stretches 119 feet (or 32 meters); and in life it likely weighed well over 60 tons (an adult elephant, by comparison, weighs about one-tenth as much). The size of these animals is simply staggering—especially considering that they began life in an egg scarcely bigger than that of an ostrich. How much vegetation did one of these have to eat in a day in order to survive?
The fossil rooms make a closed circuit, so the visitor can go in any direction. The most logical direction to go in, however, is to begin with the Hall of Vertebrate Origins—since this way the galleries are chronological.
From the perspective of biology, the Hall of Vertebrate Origins is likely the most fascinating hall of fossils, even if it lacks any of the spectacular specimens of later eons. We can see examples of the first vertebrates, on sea, on land, and in the air. One of the more memorable fossils on display are the jaws of the extinct Megalodon, a shark that lived millions of years ago, and which grew several times larger than today’s great white shark. The tremendous and terrifying jaws, hanging from the ceiling, dwarf even the bite of a Tyrannosaur. Nearby hangs a model of the Dunkleosteus, an armored fish that lived many hundreds of millions of years before the Megalodon, and which likely was major predator of its day. Further on is a Pterosaur, a member of the first known vertebrates to have achieved flight. (Commonly called dinosaurs, the Pterosaurs were closely related but technically not dinosaurs. Also, the term “Pterodactyl” only refers to one subgroup of the Pterosaurs.)
These three examples only touch on the immense biological richness in this hall. For anyone hoping to better understand the history of life on our planet, their time will be well spent in close examinations of the specimens on display. The museum also offers computer booths that allow visitors to scroll through various evolutionary trees and learn more about different species.
We now come to one of the museum’s most spectacular spaces: the Hall of the Saurischian Dinosaurs. Now, Dinosaurs are typically split into two large evolutionary groups, the Ornithiscia and the Saurischia. The latter includes all carnivorous dinosaurs as well as sauropods (and birds, the only living dinosaur group). This means that this gallery includes the famous Tyrannosaur. Even when manifestly dead, the Tyrannosaur has a commanding presence. The mere thought of it being alive is enough to cause goose bumps. And this predator—one of the largest to have ever walked the earth—was likely even more terrifying than we normally think. According to the paleontologist Stephen Brusette, Tyrannosaurus was highly intelligent, had excellent vision, and likely lived and hunted in packs. One of them is frightening enough; imagine a gaggle of T. Rex. And to think that this fearsome creature began its life no bigger than a chicken.
Across from the Tyrannosaur is another museum favorite, the Apatosaurus (sometimes called the Brontosaurus). This is a sauropod, somewhat smaller than the Titanosaur in the other room, but still large enough to make even the Tyrannosaur look petite by comparison. Another fearsome predator on display is the Allosaurus, a carnivore somewhat smaller than Tyrannosaurus that lived several million years earlier, which was an apex predator in its own epoch. This Allosaur is bending over to scrape some meat off of a fresh carcass. One less flashy specimen on display is the skull of a velociraptor (which, despite its portrayal in Jurassic Park, was about the size of a turkey).
Next we come to the Hall of the Ornithischian dinosaurs. This group does not contain quite as many star dinosaurs as the other hall, but it will not disappoint. Here can be found one of the museum’s most important specimens, a mummy of a duck-billed dinosaur. Unlike in the vast majority of dinosaur remains, here we do not only have the skeleton, but the skin of the ancient animal. This has allowed scientists to get a much better idea of what the scales of a dinosaur were like. Also on display is a Stegosaurus, famous for its small brain, spiked tail, and a back covered in vertical plates (whose purpose is still debated). My personal favorite, however, is the Triceratops, an herbivore that lived alongside T. rex and was one of its principal foes. Powerfully built, with a three-pronged horn and a protective ridge, hunting these beasts must have been no easy matter.
I am always moved by the dinosaurs. They were magnificent animals, many of them so far beyond the range of size and power that we can find among today’s land mammals and reptiles. That such a diverse group of powerful beasts could go entirely extinct from a chance event—a meteoric bolt from the blue—cannot but remind us of our own precarious existence. Indeed, these chance catastrophes play a disturbingly crucial role in the history of life on our planet. Dinosaurs themselves would never have become so dominant if not for the Triassic-Jurassic extinction event (possibly caused by volcanic activity), which eliminated much of their competition. And the mammals would never have been able to emerge as the current dominant life form if not for the Cretaceous-Paleogene extinction event, which eliminated every one of these creatures (except for birds), thus leaving the stage set for us. But how long will we last?
The next hall focuses on the early history of our own clan, the mammals. The further back one goes in evolution, the mudier become the distinctions between distinct lineages. Thus, some of the fossils on display in the Hall of Primitive Mammals do not strike us as mammals—and in fact are not, only early relatives. Into this class falls the Dimetrodon, a sail-backed cuadroped that looks far more reptilian to my eyes than anything resembling a house cat. But a close examination of its skull reveals the tell-tale opening behind its eye socket, leaving a bony arch which scientists have decided constitutes the defining mark of a new class of animal, the Synapsids, which includes mammals.
The Hall of Primitive Mammals is notable for the mammal island—a large array of fossil specimens that illustrate the range of mammalian diversity. By any measure, we mammals are an immensely diverse lot, having populated the land, sea, and air, occupying all sorts of niches, and ranging in size from a large insect (the smallest bat) to the biggest animal ever to exist (the blue whale). Amid this sea of variety we find the Glyptodont, an extinct relative of the armadillo, far larger and far more heavily armored. The face of this fossil preserves a sense of the patient drudgery which must have characterized this poor beast’s life, as it dragged its heavy shell through the landscape. The saber-toothed cat led a more exciting, if not more successful, life thousands of years ago, as did the lumbering cave bear. But the most terrifying skeleton of all may belong to the Lestodon, an enormous ground sloth whose gaping nose socket seems to look at you like a cyclops.
Finally we come to the Hall of Advanced Mammals, which features species more recently extinct (many of which died off during the great megafauna extinction 10,000 years ago). Here we can see a large array of specimens that illustrate the evolution of horses, growing up from dainty things the size of dogs up into the stallions of today (though, as often happens with evolution, this progress was not always linear). At the end of the hall we see extinct relatives of the elephant. One is the mastodon, which is about the size and build of a modern elephant, if slightly stockier. This nearly complete fossil skeleton was found in New York—amazing to consider.
Standing a head taller is the Mammoth, a much closer relative of the elephant that went extinct not too long ago, while the Mesopotamian and Egyptian civilizations were well under way. It is massive, of nearly dinosaurian proportions, with tusks that curve so tightly inward that it seems they would have been useless for defense. (Scientists are now playing with the idea of using DNA from frozen mammoth remains to bring them back. I wish them luck.)
By now, you must be exhausted. Museum fatigue has set in, and you can no longer concentrate on or even enjoy what you are seeing. This is inevitable at the American Museum of Natural History. There is just way too much. I have already written far, far more than I planned to, and there is still so much of the museum left to explore. I have left out the Hall of Reptiles and Amphibians, the Hall of North American Birds, and the Hall of Primates. And that is not all. The museum has huge exhibits devoted to cultural anthropology. Aside from the aforementioned Northwest Coast Hall, there is the Hall of Asian Peoples, the Hall of African Peoples, the Hall of Mexico and Central America, and the Hall of South American Peoples.
And here I must add a note of criticism. It says a great deal that a museum of natural history would include exclusively non-Western cultures. Admittedly, this is largely a historical artifact of the time when the study of “primitive” living peoples was grouped with the study of human evolution and primate behavior in the discipline of “anthropology.” This grouping obviously reflected cultural and racial biases of the original founders of the field. But we have moved far beyond that, and now it seems discordant and strange to walk through, say, the Hall of Asian Peoples. How could a single hall, however well-made, encompass the enormous history and diversity of the Middle East, Central Asian, Southeastern Asia, and East Asia? Even encompassing the traditions of China alone would require a museum for itself. Not only that, but the cultural halls generally have a dark and dingy aspect, as if they have been left unchanged for decades.
So it is my hope that the museum soon refurbishes, not just the Northwest Coast Hall, but all of the cultural halls—taking into account not only advances in our understanding, but how the cultures themselves would like to be represented. Judging by the progress that the museum is already making in this respect, I think that the future looks bright.
What more can I say about the Museum of Natural History? I have already said more than I planned to, and yet it scarcely seems enough. My visits to the museum had a fundamental influence on me. My shifting interests throughout my childhood and adulthood—in marine biology, chemistry, physics, botany, human evolution, and human cultures—have virtually tracked the floor plan of the museum. From an early age, I have been possessed with a desire to collect, catalogue, and display—an urge which I am sure owes much to this place. Beyond its importance in my life, however, I see the Museum of Natural History as a model institution for the coming ages, as something much needed in our society, even as a kind of secular church for the new age: capable of appealing to the mind and to the emotions. I hope that every child may feel the wonder I felt, and still feel, at both the universe around us and the intelligence within, which has allowed us to know something of this universe.
My next podcast is my review of Ptolemy’s Almagest. To listen, click below:
The Rise and Fall of the Dinosaurs: A New History of a Lost World by Stephen Brusatte
My rating: 4 of 5 stars
Like so many people, I went through a dinosaur phase as a child. It was almost inevitable. Growing up on the Upper West Side, I could visit the Museum of Natural History nearly every week. Natural selection has overcome many engineering problems—flight, sight, growth, digestion—and it has certainly not failed in its ability to awe little boys. I picked up this book to finally learn something about these ancient beasts.
Any fair evaluation of this book must conclude that it does its job: it summarizes new discoveries about dinosaurs in accessible prose. Brusatte goes through the entire chronology of the group, from their beginnings as unremarkable reptiles which emerged after the great Permian-Triassic Extinction, to their gradual rise, growth, spread, and diversification, and finally to their eventual end—wiped out by an asteroid.
There are many interesting tidbits along the way. Dinosaurs had the efficient lungs we find in modern birds, which are able to extract oxygen during the inhale and exhale. They also had primitive feathers, which looked more like hairs. Indeed, modern birds are dinosaurs in the strict sense of the word. I was particularly surprised to learn that Tyrannosaurus Rex lived and hunted in groups; and that they achieved their massive size extremely quickly—growing several pounds a day for years on end.
I also appreciated Brusatte’s descriptions of the methods that paleontologists use—new statistical techniques for analyzing fossils, or piecing together ancient ecosystems, or determining rates of evolutionary change. Nowadays paleontologists to not merely look for old bones, but they study living animals to make hypotheses about the speed, strength, and size of these extinct creatures. One researcher even studied fossils under a microscope to deduce the color of the feathers from the indentations. Brusatte also covers some of the history of dinosaur research, which is surprisingly colorful—especially the tragic life of the Baron Franz Nopcsa von Felső-Szilvás.
So the book undoubtedly accomplishes its goal. My only complaint is the style. When Brusatte sticks to the science, he is clear and engaging. But whenever he chooses to embellish the story—which is rather too often—the prose becomes strained and grating. Here is a description of a seagull that opens his chapter on birds:
When the sun breaks through for a moment, I catch a glint reflected in its beady eyes, which start to dance back and forth. No doubt this is a creature of keen senses and high intelligence, and it’s onto something. Maybe it can tell that I’m watching. Then, without warning, it yawns open its mouth and emits a high-pitched screech—an alarm to its compatriots, perhaps, or a mating call. Or maybe it’s a threat directed my way.
In fairness, I did enjoy his description of what the dinosaurs would have experienced in the first few minutes after the asteroid impact.
More irksome, however, were the thumbnail sketches of his colleagues, which are interspersed throughout the book. I would have understood the necessity of these passages if Brusatte were introducing a researcher who would play an important role in the book. Yet inevitably these researchers were introduced with fanfare only to be immediately dropped. What is more, Brusatte always focuses on the quirkiest aspects of these researchers, in a superficial attempt at coolness; and he also makes sure to tell us that he is one of their best friends.
In one particularly aggravating example, Brusatte describes one researcher’s fashion (“leopard-print Lycra, piercings, and tattoos”), ethnicity (“half-Irish, half-Chinese”), hobbies (“raving and even occasionally DJ-ing in the trendy clubs of China’s suddenly hip capital”), and conversation style (“delivering caustic one-liners one moment, speaking in eloquent paragraphs about politics the next”). Does this add anything of value to the book?
These stylistic irritations mar what is otherwise an excellent popular book about dinosaurs. And since these offending passages do not add anything to the substance of the book, my advice is just to skip on until he gets back on the subject of dinosaurs—a topic which brings out the best in Brusatte.
But sound, as I have said above, only travels 180 toises in the same time of one second: hence the velocity of light is more than six hundred thousand times greater than that of sound.
This little treatise is included in volume 34 of the Great Books of the Western World, which I used to read Newton’s Principia and his Opticks. In this edition the Treatise comes out to about 50 pages, so I decided it was worth combing through. Christiaan Huygens is one of the relatively lesser known figures of the scientific revolution. But even a brief acquaintance with his life and work is enough to convince one that he was a thinker of gigantic proportion, in a league with Descartes and Leibniz. His work in mechanics prefigured Newton’s laws, and his detailed understanding of the physics of pendulums (building from Galileo’s work) allowed him to invent the pendulum clock. His knowledge of optics also improved the technology of telescope lenses, which in turn allowed him to describe the rings of Saturn and discover the first of Saturn’s moons, Titan.
Apart from all this, Huygens was the progenitor of the wave theory of light. This is in contrast with the corpuscular theory of light (in which light is conceived of as little particles), put forward 14 years later in Isaac Newton’s Opticks. Newton’s theory quickly became more popular, partially because of its inherent strength, and partially because it was Isaac Newton who proposed it. But Huygens’s wave theory was revived and seemingly confirmed in the 19th century by Thomas Young and Augustin-Jean Fresnel.
Essentially, Huygens’s idea was to use sound as an analogy for light. Just as sound consists of longitudinal waves (vibrating in the direction they travel) propagated by air, so light must consist of much faster waves propagated by some other, finer medium, which Huygens calls the ether. He conceives of a luminous object, such as a burning coal, as emitting circular waves at every point in its surface, spreading in every direction throughout a space.
Like Newton, Huygens was aware of Ole Rømer’s calculation of the speed of light. It had long been debated whether light is instantaneous or merely moves very quickly. Aristotle rejected the second option, thinking it inconceivable that something could move so fast. Little progress had been made since then, because making a determination of light’s speed presents serious challenges: not only is light several orders of magnitude faster than anything in our experience, but since light is the fastest thing there is, and the bearer of our information, we have nothing to measure it against.
This changed once astronomers began measuring the movement of the Jovian moons. Specifically, the moon Io is eclipsed by Jupiter every 42.5 hours; but as Rømer measured this cycle at different points in the year, he noticed that it varied somewhat. Realizing that this likely wasn’t due to the moon’s orbit itself, he hypothesized that it was caused by the varying distance of Earth to Jupiter, and he used this as the basis for the first roughly accurate calculation of the speed of light. Newton and Huygens both accepted the principle and refined the results.
Huygens gets through his wave theory, reflection, and refraction fairly quickly; and in fact the bulk of this book is dedicated to an analysis of Icelandic spar—or, as Huygens calls it, “The Strange Refraction of Icelandic Crystal.” This is a type of crystal that is distinctive for its birefringence, which means that it refracts light of different polarizations at different angles, causing a kind of double image to appear through the crystal. Huygens delves into a detailed geometrical analysis of the crystal, which I admit I could not follow in the least; nevertheless, the defining property of polarization eludes him, since to understand it one must conceive of light as a transverse, not a longitudinal, wave (that is, unlike a sound wave, which cannot be polarized). In the end, he leaves this puzzling property of the crystal for future scientists, but not without laying the groundwork of observation and theory that we still rely upon.
All together, this little treatise is a deeply impressive work of science: combining sophisticated mathematical modeling with careful experimentation to reach surprising new conclusions. Huygens illustrates perfectly the rare mix of gifts that a scientist must have in order to be successful: a sharp logical mind, careful attention to detail, and a creative imagination. The world is full of those with only one or two of these qualities—brilliant mathematicians with no interest in the real world, obsessive recorders and cataloguers with no imagination, brilliant artists with no gift for logic—but it takes the combination to make a scientist of the caliber of Huygens.
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There is not a single effect in Nature, not even the least that exists, such that the most ingenious theorists can ever arrive at a complete understanding of it.
One of the most impressive aspects of the Very Short Introduction series is the range of creative freedom allowed to its writers. (Either that, or its flexibility in repurposing older writings; presumably a version of this book was published before the VSI series even got off the ground, since its author died in 1993.) This is a good example: For in lieu of an introduction, Stillman Drake, one of the leading scholars of the Italian scientist, has given us a novel analysis of Galileo’s trial by the Inquisition.
Admittedly, in order to contextualize the trial, Drake must cover all of Galileo’s life and thought. But Drake’s focus on the trial means that many things one would expect from an introduction—for example, an explanation of Galileo’s lasting contributions to science—are only touched upon, in order to make space for what Drake believed was the crux of the conflict: Galileo’s philosophy of science.
Galileo Galilei was tried in 1633 for failing to obey the church’s edict that forbade the adoption, defense, or teaching of the Copernican view. And it seems that he has been on trial ever since. The Catholic scientist’s battle with the Catholic Church has been transformed into the archetypical battle between religion and science, with Galileo bravely championing the independence of human reason from ancient dogma. This naturally elevated Galileo to the status of intellectual heroe; but more recently Galileo has been criticized for falling short of this ideal. Historian of science, Alexandre Kojève, famously claimed that Galileo hadn’t actually performed the experiments he cited as arguments, but that his new science was mainly based on thought experiments. And Arthur Koestler, in his popular history of astronomy, criticized Galileo for failing to incorporate Kepler’s new insights. Perhaps Galileo was not, after all, any better than the scholastics he criticized?
Drake has played a significant role in pushing back against these arguments. First, he used the newly discovered working papers of Galileo to demonstrate that, indeed, he had performed careful experiments in developing his new scheme of mechanics. Drake also points out that Galileo’s Dialogue Concerning the Two Chief World Systems was intended for popular audiences, and so it would be unreasonable to expect Galileo to incorporate Kepler’s elliptical orbits. Finally, Drake draws a hard line between Galileo’s science and the medieval theories of motion that have been said to presage Galileo’s theories. Those theories, he observes, were concerned with the metaphysical cause of motion; whereas Galileo abandoned the search for causes, and inaugurated the use of careful measurements and numerical predictions in science.
Thus, Drake argues that Galileo never saw himself as an enemy of the Church; to the contrary, he saw himself as fighting for its preservation. What Galileo opposed was the alignment of Church dogma with one very particular interpretation of scripture, which Galileo believed would put the church in danger of being discredited in the future. Galileo attributed this mistaken policy to a group of malicious professors of philosophy, who, in the attempt to buttress their outdated methods, used Biblical passages to make their views seem orthodox. This was historically new. Saint Augustine, for example, considered the opinions of natural philosophers entirely irrelevant to the truth of the Catholic faith, and left the matter to experts. It was only in Galileo’s day (during the Counter-Reformation) that scientific theories became a matter of official church policy.
Drake’s conclusion is that Galileo’s trial was not so much a conflict between science and religion (for the two had co-existed for many centuries), but between science and philosophy: the former concerned with measurement and prediction, the latter concerned with causes. And Drake notes that many contemporary criticisms of Galileo—leaving many loose-ends in his system, for example—mirror the contemporary criticisms of his work. The trial goes on.
Personally I found this book fascinating and extremely lucid. However, I am not sure it exactly fulfills its promise as an introduction to Galileo. I think that someone entirely new to Galileo’s work, or to the history and philosophy of science, may not get as much out of this work. Luckily, most of Galileo’s own writings (translated by Drake) are already very accessible and enjoyable.
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It is shown in the Scholium of Prop. 22, Book II, that at the height of 200 miles above the earth the air is more rare than it is at the surface of the earth in the ratio of 30 to 0.0000000000003998, or as 75,000,000,000,000 to 1, nearly.
Marking this book as “read” is as much an act of surrender as an accomplishment. Newton’s reputation for difficulty is well-deserved; this is not a reader-friendly book. Even those with a strong background in science and mathematics will, I suspect, need some aid. The historian of mathematics Colin Pask relied on several secondary sources to work his way through the Principia in order to write his excellent popular guide. (Texts by S. Chandrasekhar, J. Bruce Brackenridge, and Dana Densmore are among the more notable vade mecums for Newton’s proofs.) Gary Rubenstein, a math teacher, takes over an hour to explain a single one of Newton’s proofs in a series of videos (and he had to rely on Brackenridge to do so).
It is not that Newton’s ideas are inherently obscure—though mastering them is not easy—but that Newton’s presentation of his work is terse, dense, incomplete (from omitting steps), and at times cryptic. Part of this was a consequence of his personality: he was a reclusive man and was anxious to avoid public controversies. He says so much himself: In the introduction to Book III, Newton mentions that he had composed a popular version, but discarded it in order to “prevent the disputes” that would arise from a wide readership. Unsurprisingly, when you take material that is intrinsically complex and then render it opaque to the public, the result is not a book that anyone can casually pick up and understand.
The good news is that you do not have to. Newton himself did not advise readers, even mathematically skilled readers, to work their way through every problem. This would be enormously time-consuming. Indeed, Newton recommended his readers to peruse only the first few sections of Book I before moving on directly to Book III, leaving most of the book completely untouched. And this is not bad advice. As Ted said in his review, the average reader could gain much from this book by simply skipping the proofs and calculations, and stopping to read anything that looked interesting. And guides to the Principia are certainly not wanting. Besides the three mentioned above, there is the guide written by Newton scholar I. Bernard Cohen, published as a part of his translation. I initially tried to rely on this guide; but I found that, despite its interest, it is mainly geared towards historians of science; so I switched to Colin Pask’s Magnificent Principia, which does an excellent job in revealing the importance of Newton’s work to modern science.
So much for the book’s difficulty; on to the book itself.
Isaac Newton’s Philosophiæ Naturalis Principia Matematica is one of the most influential scientific works in history, rivaled only by Darwin’s On the Origin of Species. Quite simply, it set the groundwork for physics as we know it. The publication of the Principia, in 1687, completed the revolution in science that began with Copernicus’s publication of De revolutionibus orbium coelestium over one hundred years earlier. Copernicus deliberately modeled his work on Ptolemy’s Almagest, mirroring the structure and style of the Alexandrian Greek’s text. Yet it is Newton’s book that can most properly be compared to Ptolemy’s. For both the Englishman and the Greek used mathematical ingenuity to draw together the work of generations of illustrious predecessors into a single, grand, unified theory of the heavens.
The progression from Copernicus to Newton is a case study in the history of science. Copernicus realized that setting the earth in motion around the sun, rather than the reverse, would solve several puzzling features of the heavens—most conspicuously, why the orbits of the planets seem related to the sun’s movement. Yet Copernicus lacked the physics to explain how a movable earth was possible; in the Aristotelian physics that held sway, there was nothing to explain why people would not fly off of a rotating earth. Furthermore, Copernicus was held back by the mathematical prejudices of the day—namely, the belief in perfect circles.
Johannes Kepler made a great stride forward by replacing circles with ellipses; this led to the discovery of his three laws, whose strength finally made the Copernican system more efficient than its predecessor (which Copernicus’s own version was not). Yet Kepler was able to provide no account of the force that would lead to his elliptical orbits. He hypothesized a sort of magnetic force that would sweep the planets along from a rotating sun, but he could not show why such a force would cause such orbits. Galileo, meanwhile, set to work on the new physics. He showed that objects accelerate downward with a velocity proportional to the square of the distance; and he argued that different objects fall at different speeds due to air resistance, and that acceleration due to gravity would be the same for all objects in a vacuum. But Galileo had no thought of extending his new physics to the heavenly bodies.
By Newton’s day, the evidence against the old Ptolemaic system was overwhelming. Much of this was observational. Galileo observed craters and mountains on the moon; dark spots on the sun; the moons of Jupiter; and the phases of Venus. All of these data, in one way or another, contradicted the old Aristotelian cosmology and Ptolemaic astronomy. Tycho Brahe observed a new star in the sky (caused by a supernova) in 1572, which confuted the idea that the heavens were unchanging; and observations of Haley’s comet in 1682 confirmed that the comet was not somewhere in earth’s atmosphere, but in the supposedly unchanging heavens.
In short, the old system was becoming unsustainable; and yet, nobody could explain the mechanism of the new Copernican picture. The notion that the planets’ orbits were caused by an inverse-square law was suspected by many, including Edmond Haley, Christopher Wren, and Robert Hooke. But it took a mathematician of Newton’s caliber to prove it.
But before Newton published his Principia, another towering intellect put forward a new system of the world: René Descartes. Some thirty years before Newton’s masterpiece saw the light of day, Descartes published his Principia Philosophiæ. Here, Descartes summarized and systemized his skeptical philosophy. He also put forward a new mechanistic system of physics, in which the planets are borne along by cosmic vortices that swirl around each other. Importantly, however, Descartes’s system was entirely qualitative; he provided no equations of motion.
Though Descartes’s hypothesis has no validity, it had a profound effect on Newton, as it provided him with a rival. The very title of Newton’s book seems to allude to Descartes’s: while the French philosopher provides principles, Newton provides mathematical principles—a crucial difference. Almost all of Newton’s Book II (on air resistance) can be seen as a detailed refutation of Descartes’s work; and Newton begins his famous General Scholium with the sentence: “The hypothesis of vortices is pressed with many difficulties.”
In order to secure his everlasting reputation, Newton had to do several things: First, to show that elliptical orbits, obeying Kepler’s law of equal areas in equal times, result from an inverse-square force. Next, to show that this force is proportional to the mass. Finally, to show that it is this very same force that causes terrestrial objects to fall to earth, obeying Galileo’s theorems. The result is Universal Gravity, a force that pervades the universe, causing the planets to rotate and apples to drop with the same mathematical certainty. This universal causation effectively completes the puzzle left by Copernicus: how the earth could rotate around the sun without everything flying off into space.
The Principia is in a league of its own because Newton does not simply do that, but so much more. The book is stuffed with brilliance; and it is exhausting even to list Newton’s accomplishments. Most obviously, there are Newton’s laws of motion, which are still taught to students all over the world. Newton provides the conceptual basis for the calculus; and though he does not explicitly use calculus in the book, a mathematically sophisticated reader could have surmised that Newton was using a new technique. Crucially, Newton derives Kepler’s three laws from his inverse-square law; and he proves that Kepler’s equation has no algebraic solution, and provides computational tools.
Considering the mass of the sun in comparison with the planets, Newton could have left his system as a series of two-body problems, with the sun determining the orbital motions of all the planets, and the planets determining the motions of their moons. This would have been reasonably accurate. But Newton realized that, if gravity is truly universal, all the planets must exert a force on one another; and this leads him to the invention of perturbation theory, which allows him, for example, to calculate the disturbance in Saturn’s orbit caused by proximity to Jupiter. While he is at it, Newton calculates the relative sizes and densities of the planets, as well as calculates where the center of gravity between the gas giants and the sun must lie. Newton also realized that gravitational effects of the sun and moon are what cause terrestrial tides, and calculated their relative effects (though, as Pask notes, Newton fudges some numbers).
Leaving little to posterity, Newton realized that the spinning of a planet would cause a distortion in its sphericity, making it marginally wider than it is tall. Newton then realized that this slight distortion would cause tidal locking in the case of the moon, which is why the same side of the moon always faces the earth. The slight deformity of the earth is also what causes the procession of the equinoxes (the very slow shift in the location of the equinoctial sunrises in relation to the zodiac). This shift was known at least since Ptolemy, who gave an estimate (too slow) of the rate of change, but was unable to provide any explanation for this phenomenon.
The evidence mustered against Descartes’s theory is formidable. Newton describes experiments in which he dropped pendulums in troughs of water, to test the effects of drag. He also performed experiments by dropping objects from the top of St. Paul’s Cathedral. What is more, Newton used mathematical arguments to show that objects rotating in a vortex obey a periodicity law that is proportional to the square of the distance, and not, as in Kepler’s Third Law, to the 3/2 power. Most convincing of all, Newton analyzes the motion of comets, showing that they would have to travel straight through several different vortices, in the direction contrary to the spinning fluid, in order to describe the orbits that we observe—a manifest absurdity. While he is on the subject of comets, Newton hypothesizes (correctly) that the tail of comets is caused by gas released in proximity to the sun; and he also hypothesizes (intriguingly) that this gas is what brings water to earth.
This is only the roughest of lists. Omitted, for example, are some of the mathematical advances Newton makes in the course of his argument. Even so, I think that the reader can appreciate the scope and depth of Newton’s accomplishment. As Pask notes, between the covers of a single book Newton presents work that, nowadays, would be spread out over hundreds of papers by thousands of authors. The result is a triumph of science. Newton not only solves the longstanding puzzle of the orbits of the planets, but shows how his theory unexpectedly accounts for a range of hitherto separate and inexplicable phenomena: the tides, the procession of the equinoxes, the orbit of the moon, the behavior of pendulums, the appearance of comets. In this Newton demonstrated what was to become the hallmark of modern science: to unify as many different phenomena as possible under a single explanatory scheme.
Besides setting the groundwork for dynamics, which would be developed and refined by Euler, d’Alembert, Lagrange, Laplace, and Hamilton in the coming generations, Newton also provides a model of science that remains inspiring to practitioners in any field. Newton himself attempts to enunciate his principles, in his famous Rules of Reasoning. Yet his emphasis on inductivism—generalizing from the data—does not do justice to the extraordinary amount of imagination required to frame suitable hypotheses. In any case, it is clear that Newton’s success was owed to the application of sophisticated mathematical models, carefully tested against collections of physical measurements, in order to unify the greatest possible number of phenomena. And this was to become a model for other intellectual disciples to aspire to, for good and for ill.
A striking consequence of this model is that its ultimate causal mechanism is a mathematical rule rather than a philosophical principle. The planets orbit the sun because of gravity, whose equations accurately predict their motions; but what gravity is, why it exists, and how it can affect distant objects, is left completely mysterious. This is the origin of Newton’s famous “I frame no hypothesis” comment, in which he explicitly restricts himself to the prediction of observable events rather than speculation on hidden causes (though he was not averse to speculation when the mood struck him). Depending on your point of view, this shift in emphasis either made science more rational or more superficial; but there is little doubt that it made science more effective.
Though this book is too often impenetrable, I still recommend that you give it a try. Few books are so exalting and so humbling. Here is on display the furthest reaches of the power of the human intellect to probe the universe we live in, and to find hidden regularities in the apparent chaos of experience.
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My rating: 3 of 5 stars
The Earth sings MI, FA, MI so that you may infer even from the syllables that in this our domicile MIsery and FAmine obtain.
Thomas Kuhn switched from studying physics to the history of science when, after teaching a course on outdated scientific models, he discovered that his notion of scientific progress was completely mistaken. As I plow through these old classics in my lackadaisical fashion, I am coming to the same conclusion. For I have discovered that the much-maligned Ptolemy produced a monument of observation and mathematical analysis, and that Copernicus’s revolutionary work relied heavily on this older model and was arguably less convincing. Now I discover that Johannes Kepler, one of the heroes of modern science, was also something of a crackpot.
The mythical image of the ideal scientist, patiently observing, cataloguing, calculating—a person solely concerned with the empirical facts—could not be further removed from Kepler. Few people in history had such a fecund and overactive imagination. Every new observation suggested a dozen theories to his feverish mind, not all of them testable. When Galileo published his Siderius Nuncius, for example, announcing the presence of moons orbiting Jupiter, Kepler immediately concluded that there must be life on Jupiter—and, why not, on all the other planets. Kepler even has a claim of being the first science-fiction writer, with his book Somnium, describing how the earth would appear to inhabitants of the moon (though Lucian of Samothrace, writing in the 2nd Century AD, seems to have priority with his fantastical novella, A True Story). This imaginative book, by the way, may have contributed to the accusations that Kepler’s mother was a witch.
In reading Kepler, I was constantly reminded of a remark by Bertrand Russell: “The first effect of emancipation from the Church was not to make men think rationally, but to open their minds to every sort of antique nonsense.” Similarly, the decline in Aristotle’s metaphysics did not prompt Kepler to reject metaphysical thinking altogether, but rather to speculate with wild abandon. But Kepler’s speculations differed from the ancients’ in two important respects: First, even when his theories are not testable, they are mathematical in nature. Gone are the verbal categories of Aristotle; and in comes the modern notion that nature is the manifestation of numerical harmonies. Second, whenever Kepler’s theories are testable, he tested them, and thoroughly. And he had ample data with which to test his speculations, since he was bequeathed the voluminous observations of his former mentor, Tycho Brahe.
At its worst, Kepler’s method resulted in meaningless numerical coincidences that explained nothing. As many a statistician has learned, if you crunch enough numbers and enough variables, you will eventually stumble upon a serendipitous correlation. This aptly describes Kepler’s use of the five Platonic solids to explain planetary orbits; by trying many combinations, Kepler found that he could create an arrangement of these regular solids, nested within one another, that mostly corresponded with the size of the planets’ orbits. But what does this explain? And how does this help calculation? The answer to both of these questions is negative; the solution merely appeals to Kepler’s sense of mathematical elegance, and reinforced his religious conviction that God must have arranged the world harmoniously.
Another famous example of this is Kepler’s notion of the “harmonies of the world.” By playing with the numbers of the perihelion, aphelion, orbital lengths, and so forth, Kepler assigns a melodic range to each of the planets. Mercury, having the most elongated orbit, has the biggest range; while Venus’s orbit, which most approximates a perfect circle, only produces a single note. Jupiter and Saturn are the basses, of course, while Mars is the tenor, Earth and Venus the altos, and Mercury the soprano. He then suggests (though vaguely) that there are beings on the sun, capable of sensing this heavenly music. (The composer Laurie Spiegel created a piece in which she recreates this music; it is not exactly Bach.) Once more, we naturally ask: What would all this speculation on music and harmonies explain? And once more, the answer is nothing.
Kepler’s writing is full of this sort of thing—torturous explorations of ratios, data, figures, which strike the modern mind as ravings rather than reasoning. But the fact remains that Kepler was one of the great scientific geniuses of history. He was writing in a sort of interim period between the fall of Aristotelian science and the rise of Newtonian physics, a time when the mind of Europe was completely untethered to any recognizable paradigm, free to luxuriate in speculation. Most people in such circumstances would produce nothing but nonsense; but Kepler managed to invent astrophysics.
What gives Kepler a claim to this title was his conception of a scientific law (though he did not put it as such). Astronomers from Ptolemy to Copernicus used schemes to predict planetary movements; but there was no one underlying principle which could explain everything. Kepler’s relentless search for numerical coincidences led him to statements that unified observations of all the planets. These are now known as Kepler’s Laws.
The first of these was the seemingly simple but revolutionary insight that planets orbit in ellipses, with the sun at one of the foci. It is commonly said that previous astronomers preferred circles for petty metaphysical reasons, seeing them as perfect. But there were other reasons, too. Most obviously, the mathematics of shapes inscribed in circles was well-understood; this was the basis of trigonometry.
Yet the use of circles to track orbits that, in reality, are not circular, created some problems. Thus in the Ptolemaic system the astronomer used one circle (the eccentric) for the distance, and another, overlapping circle (the equant) for the speed. When these were combined with the epicycles (used to explain retrogression) the resultant orbits, though composed of perfect circles, were anything but circular. Kepler’s use of ellipses obviated the need for all these circles, reducing a complicated machinery into a single shape. It was this innovation that made the Copernican system so much more efficient than the Ptolemaic one. As Owen Gingerich, a Copernican scholar, has said: “What passes today as the ‘Copernican System’ is in detail the Keplerian system.”
Yet the use of ellipses, by itself, would not have been so useful were it not for Kepler’s Second Law: that planets sweep out equal areas in equal times of their orbits. For when a planet is closest to the sun (at perihelion) it is moving its fastest; and when it is furthest (at aphelion) it is slowest; and this creates a constant ratio (which is the result of the conserved angular momentum of each planet). Ironically, of the two, Ptolemy was closer than Copernicus to this insight, since Ptolemy’s much-maligned equant (the imaginary point around which a planet travels at a constant speed) is a close approximation of the Second Law. Even so, I think that Kepler moved far beyond all previous astronomy with these insights, jumping from observed and analyzed regularities to general principles.
Kepler’s Third Law seemed to have excited the astronomer the most, since he even includes the exact date at which he made the realization: “… on the 8th of March in this year One Thousand Six Hundred and Eighteen but unfelicitously submitted to calculation and rejected as false, finally, summoned back on the 15th of May, with a fresh assault undertaken, outfought the darkness of my mind.” This law states that, for every planet, the ratio of the orbital period squared to the orbital size cubed, is constant. (For the orbital size Kepler used half the major axis of the ellipse.)
While it is no doubt striking that this ratio is almost the same for every planet (this is because the planet’s mass is negligible compared with the sun’s), it is difficult to completely sympathize with Kepler’s excitement, since the resultant law is not useful for predicting orbits, and its significance was only explained much later by Newton as a derivable conclusion from his equations. Kepler, being the man he was, used this mathematical constant to fuel his metaphysical speculations.
However much, then, that Kepler’s theories may strike us nowadays as baseless, crackpot theorizing, he must be given a commanding place in the history of science. The reason I cannot rate this collection any higher is that Kepler is extremely tiresome to read. In his more lucid moments, his imaginative energy is charming. But much of the book consists of whole paragraphs of ratio after ratio, shape after shape, number after number, and so it is easy to get lost or bored. Since I have a decent grasp of music theory, I thought I might be able to get something out of his Harmonies of the World, but I found even that section mostly opaque, swirling in obscure and impenetrable reasoning.
The great irony, then, is that Kepler’s writings can strike the modern-day reader as far less “scientific” than Ptolemy’s; but perhaps we should expect such ironies from a man who helped to inaugurate modern science, but who made his living casting horoscopes.
My rating: 4 of 5 stars
And though all these things are difficult, almost inconceivable, and quite contrary to the opinion of the multitude, nevertheless in what follows we will with God’s help make them clearer than day—at least for those who are not ignorant of the art of mathematics.
The Copernican Revolution has become the prime exemplar of all the great transformations in our knowledge of the world—a symbol of scientific advance, the paradigmatic clash of reason and religion, a shining illustration of how cold logic can beat out old prejudices. Yet reading this groundbreaking book immediately after attempting Ptolemy’s Almagest—the Bible of geocentric astronomy—reveals far more similarities than differences. Otto Neugebauer was correct in calling Copernicus’s system an ingenious modification of Hellenistic astronomy, for it must be read against the background of Ptolemy in order to grasp its significance.
The most famous section of De revolutionibus was, ironically, not even written by Copernicus, but by the presumptuous Andreas Osiander, a Lutheran theologian who was overseeing the publication of the book, and who included a short preface without consulting or informing Copernicus. Knowing that Copernicus’s hypothesis could prove controversial (Luther considered it heretical), Osiander attempted to minimize its danger by asserting that it was merely a way of calculating celestial positions and did not represent physical reality: “for it is not necessary that the hypotheses should be true, or even probable; but it is enough if they provide a calculation which fits the observations.”
Though this assertion obviously contradicts the body of the work (in which Copernicus argues at length for the reality of the earth’s movement), and though Copernicus and his friends were outraged by the insertion, it did help to shield the book from censure. And arguably Osiander was being a good and true Popperian—believing that science is concerned with making accurate predictions, not in giving us “the truth.” In any case, Osiander was no doubt correct in this assertion: “For it is sufficiently clear that this art is absolutely and profoundly ignorant of the causes of the apparent irregular movements.” Neither Ptolemy nor Copernicus had any coherent explanation of what caused the orbits of the planets, which would not come until Einstein.
After this little interpolation, Copernicus himself wastes no time in proclaiming the mobility of the earth. In retrospect, it is remarkable that it took such a long stretch of history for the heliocentric idea to emerge. For it instantly explains many phenomena which, in the Ptolemaic system, are completely baffling. Why do the inner planets (Venus and Mercury) move within a fixed distance of the sun? Why does the perigee (the closest point in the orbit) of the outer planets (Mars, Jupiter, Saturn) occur when they are at opposition (i.e., when they are opposite in the sky from the sun), and why does their apogee (the farthest point) occur when they are in conjunction (when they are hidden behind the sun)? And why do the planets sometimes appear to move backwards relative to the fixed stars?
But putting the earth in orbit between Venus and Mars neatly and instantly explains all of these mysteries. Mercury and Venus always appear a fixed distance from the sun because they are orbiting within the earth’s orbital circle, and thus from our position appear to go back and forth around the sun. Mars, Jupiter, and Saturn, by contrast, can appear at any longitudinal distance from the sun because their orbits are outsider ours; but if Mars’ orbit were tracked from Jupiter, for example, it would, like Venus and Mercury, appear to go back and forth around the sun. Also note that Mars will appear to go “backwards” from earth when earth overtakes the red planet, due to our planet’s shorter orbital period. And since Mars will be closest to us when it is on the same side of the sun as earth (opposition from the sun), and furthest from us when it is on far side of the sun (conjunction with the sun), this also explains the apogee and perigee positions of the outer planets.
This allows Copernicus to collapse five circles—one for each of the planets, which were needed in the Ptolemaic system to account for these anomalies—into one circle: namely, the earth’s orbit. The advantages are palpable.
Nevertheless, while I think the benefits of putting the planets in orbit around the sun are obvious, perhaps even to a traditionalist, it is not obvious why Copernicus should put the earth in motion around the sun rather than the reverse. Indeed, this is exactly what the eminent astronomer Tycho Brahe did, several generations later. For it makes no observational difference whether the sun or the earth is in motion. And in the Aristotelian physics of the time, the former solution makes a great deal more sense, since the heavens were supposed to be constituted of the lightest elements and the earth of the heaviest elements. So how could the heavy earth move so quickly? What is more, there is no concept of inertia or gravity in Aristotelian physics, and so no explanation for why people would not fly off the earth if it were in rapid motion.
Copernicus takes a brief stab at answering these obvious counterarguments, even offering a primitive notion of inertia: “As a matter of fact, when a ship floats on over a tranquil sea, all the things outside seem to the voyagers to be moving in a movement which is the image of their own, and they think on the contrary that they themselves and all the things with them are at rest.” Even so, it is obvious that such a brief example does not suffice to refute the entire Aristotelian system. Clearly, a whole new concept of physics was needed if the earth was to be in motion, one which did not arrive until Isaac Newton, born nearly two hundred years after Copernicus. It took a certain amount of boldness, or obtuseness, for Copernicus to proclaim the earth’s motion without at all being able to explain how the heaviest object in the universe—or so they believed—could hurtle through space.
In structure and content, De revolutionibus follows the Algamest pretty closely: beginning with mathematical preliminaries, onward to the orbits of the sun (or, in this case the earth), the moon, and the planets—with plenty of tables to aid calculation—as well as a description of his astronomical instruments and a chart of star locations, and finally ending with deviations in celestial latitude (how far the planets deviate north and south from the ecliptic in their orbits). Copernicus was even more wedded than Ptolemy to the belief that celestial objects travel in perfect circles, which leads him to repudiate Ptolemy’s use of the equant (the point around which a planet moves at a constant speed). The use of the equant upset Copernicus’s sense of elegance, you see, since its center is different from the planet’s actual center of orbit, thus requiring two overlapping circles.
Copernicus’s own solution was an epicyclet, which revolves twice westward (clockwise, from the celestial north pole) for each rotation eastward on the deferent. And so, ironically, though Ptolemy is sometimes mocked for using epicycles, Copernicus followed the same path. I also find it amusing that the combined effect of these circular motions, in both Ptolemy and Copernicus, added up to a non-circular orbit; clearly nature had different notions of elegance than these astronomers. In any case, it would have to wait until Kepler that it was realized that the planets actually follow an ellipse.
Perhaps the greatest irony is that Copernicus’s book is not any easier to use than Ptolemy’s as a recipe book for planetary positions. Now, it is far beyond my powers to even attempt such a calculation. But in his Very Short Introduction to Copernicus (which I recommend), Owen Gingerich takes the reader through the steps to calculation the position of Mars on Copernicus’s birthday: February 19, 1473. To do this you needed the radix, which is a root position of the planet recorded at a specified time; and you also need the planet’s orbital speed (the time needed for one complete orbit, in this case 687 days). The year must be converted into sexigesimal (base 60) system, and then converted in elapsed Egyptian years (which lack a leap year), in order to calculate the time elapsed since the date of the radix’s position (in this case is January 1st, 1 AD). Then this sexigesimal number can be looked up in Copernicus’s tables; but this only gives us the location of Mars with respect to the sun. To find out where it will appear in the sky, we also need the location of earth, which is another tedious process. You get the idea.
I read the bulk of this book while I was on vacation in rural Canada. Faced with the choice between relaxation or self-torture, I naturally chose the latter. While most of my time was spent scratching my head and helplessly scratching the page with a pencil, the experience was enough to show me—as if I needed more demonstration after Ptolemy—that astronomy is not for the faint of heart, but requires intelligence, patience, and care.
There was one advantage to reading the book on vacation. For it is the only time of year when I am in a place without light pollution. The stars, normally hiding behind street lights and apartment buildings, shone in the hundreds. I would have seen even more were it not for the waxing moon. But this did give me the opportunity to get out an old telescope—bought as a birthday present for a cousin, over a decade ago—and examine the moon’s pitted surface. It is humbling to think that even such basic technology was years ahead of Copernicus’s time.
Looking at the brilliant grey circle, surrounded by a halo of white light, I felt connected to the generations of curious souls who looked at the same moon and the same stars, searching for answers. So Copernicus did not, in other words, entirely spoil my vacation.
My rating: 4 of 5 stars
A most excellent a kind service has been performed by those who defend from envy the great deeds of excellent men and have taken it upon themselves to preserve from oblivion and ruin names deserving of immortality.
This book (more of a pamphlet, really) is proof that you do not need to write many pages to make a lasting contribution to science. For it was in this little book that Galileo set forth his observations made through his newly improved telescope. In 50-odd pages, with some accompanying diagrams and etchings, Galileo quickly asserts the roughness of the Moon’s surface, avers the existence of many more stars than can be seen with the naked eye, and—the grand climax—announces the existence of the moons of Jupiter. Suddenly the universe seemed far bigger, and stranger, than it had before.
The actual text of Siderius Nuncius does not make for exciting reading. To establish his credibility, Galileo includes a blow-by-blow account of his observations of the moons of Jupiter, charting their nightly appearance. The section on our Moon is admittedly more compelling, as Galileo describes the irregularities he observed as the sun passed over its surface. Even so, this edition is immeasurably improved by the substantial commentary provided by Albert van Helden, who gives us the necessary historical background to understand why it was so controversial, and charts the aftermath of the publication.
Though Galileo is sometimes mistakenly credited with inventing the telescope, spyglasses were widely available at the time; what Galileo did was improve his telescope far beyond the magnification commonly available. The result was that, for a significant span of time, Galileo was the only person on the planet with the technology to closely and accurately observe the heavens. The advantage was not lost on him, and he made sure that he published before he got scooped. In another shrewd move, he named the newly-discovered moons of Jupiter after the Grand Duke Cosimo II and his brothers, for which they were known as the Medician Stars (back then, the term “star” meant any celestial object). This earned him patronage and protection.
Galileo’s findings were controversial because none of them aligned with the predictions of Aristotelian physics and Ptolemaic astronomy. According to the accepted view, the heavens were pure and incorruptible, devoid of change or imperfection. Thus it was jarring to find the moon’s surface bumpy, scarred, and mountainous, just like Earth’s. Even more troublesome were the Galilean moons. In the orthodox view the Earth was the only center of orbit; and one of the strongest objections against Copernicus’s system was that it included two centers, the Sun and the Earth (for the Moon). Galileo’s finding of an additional center of orbit meant that this objection ceased to carry any weight, since in any case we must posit multiple centers. Understandably there was a lot of skepticism at first, with some scholars doubting the efficacy of Galileo’s new instrument. But as other telescopes caught up with Galileo’s, and new anomalies were added to the mix—the phases of Venus and the odd shape of Saturn—his observations achieved widespread acceptance.
Though philosophers and historians of science often emphasize the advance of theory, I find this text a compelling example of the power of pure observation. For Galileo’s breakthrough relied, not on any new theory, but on new technology, extending the reach of his senses. He had no optical theory to guide him as he tinkered with his telescope, relying instead on simple trial-and-error. And though theory plays a role in any observation, some of Galileo’s findings—such as that the Milky Way is made of many small stars clustered together—are as close to simple acts of vision as possible. Even if Copernicus’s theory was not available as an alternative paradigm, it seems likely to me that advances in the power of telescopes would have thrown the old worldview into a crisis. This goes to show that observational technology is integral to scientific progress.
It is also curious to note the moral dimension of Galileo’s discovery. Now, the Ptolemaic system is commonly lambasted as narcissistically anthropocentric, placing humans at the center of it all. Yet it is worth pointing out that, in the Ptolemaic system, the heavens are regarded as pure and perfect, and everything below the moon as corruptible and imperfect (from which we get the term “sublunary”). Indeed, Dante placed the circles of paradise on the moon and the planets. So arguably, by making Earth the equal of the other planets, the new astronomy actually raised the dignity of our humble abode. In any case, I think that it is simplistic to characterize the switch from geocentricity to heliocentricity as a tale of declining hubris. The medieval Christians were hardly swollen with pride by their cosmic importance.
As you can see, this is a fascinating little volume that amply rewards the little time spent reading it. Van Helden has done a terrific job in making this scientific classic accessible.