In the mid-18th century, the Italian
anatomist Luigi Galvani suspected that electricity held the secret of life after he observed that a current discharged from a storage device called a Leyden jar could
make the dissected legs of frogs twitch as though they were reanimated. He also saw such movements during a thunderstorm,
as if the atmospheric electricity found its
way into the limbs. He thought that animals themselves might generate their own electricity, and his ideas inspired Mary Shelley when she described the reanimation of a reconstructed corpse in her book Frankenstein (1818).
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Some philosophers have argued that “beauty” in science stands as a proxy for truth. Many scientists have agreed. The British physicist Paul Dirac, for example, claimed that it is more important for a theory to be beautiful than for it to conform with experimental tests. And Einstein stated that “the only physical theories we are willing to accept are the beautiful ones.” Such aesthetic judgments seem a little shallow, however, and also perilous: we might be tempted to place undue trust in an idea simply because we deem it beautiful. Indeed, other scientists are skeptical that perceptions of beauty are any guide to validity; what matters in the end is whether a theory fits what we see in the real world. The 19th-century British zoologist Thomas Henry Huxley said that the great tragedy of science is “the slaying of a beautiful hypothesis by an ugly fact.” But hypotheses and theories are not the only sources of scientific beauty.
Evangelista Torricelli’s studies of air pressure in the 1640s revealed the extraordinary pressure that pushes down on everything at Earth’s surface owing to the weight of the atmosphere—what he called an “ocean of air”—above it.
Torricelli’s studies led to the invention of the barometer for measuring atmospheric
pressure. His ideas were verified in 1648 by the French philosopher Blaise Pascal, who had his
brother-in-law carry a primitive barometer (an inverted tube filled with mercury) up a mountain in the French region known as the Massif Central
and observe that the air pressure dropped at the higher altitude.
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Experiments are at the core of science. It is typically by experimentation that scientific progress is made: say, from the discovery of the first virus in 1892 to the creation of covid-19 vaccines in 2020. We might be tempted to assume, then, that the process by which experiments lead to reliable and useful knowledge is well understood. But that’s not really so. In putting together my book Beautiful Experiments, a (highly selective) history of experimental science, one of my aims was to show that scientific knowledge has not been steadily churned out from the well-oiled machinery of experimental methodology; the emergence of robust theories and concepts from empirical investigations is altogether more haphazard, and more interesting.
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Known for his theory of evolution by natural selection—the central organizing framework
for understanding life—Charles Darwin was also an astute observer of nature and an avid experimenter, driven by a deep curiosity about the living world. His experiments on earthworms,
conducted in his garden from the 1870s to the 1880s, showed how efficiently they manipulated
leaves to plug the holes they make in the soil as protection against predators or rain. Even the humble worms, said Darwin, “show some degree
of intelligence.”
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Electrons were the first subatomic particles—“pieces of atoms”—to be discovered. Though they were known to carry an electrical
charge, it was extremely challenging to measure that charge accurately. The American scientist
Robert Millikan did it in experiments conducted in 1909–’13 in which he observed the movements of tiny oil droplets in an electric field, assuming that the smallest difference in their charge corresponded to a difference of just a single electron.
His work showed how important it was for experimenters to develop an instinctive feeling for their
apparatus.
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We can, as I do here, talk about some experiments as being “beautiful,” though what that means isn’t easily stated. There are many potential aesthetic virtues in an experiment: beauty of concept, economy of instrumental design, the aptness with which the two are aligned, and elegance of reasoning in interpreting the results. These are qualities that require creativity and imagination—there is no prescription for them.
Physicist Chien-Shiung Wu’s demonstration of the violation of parity (1956), which showed that nature distinguishes right from left, shattered one of the long-standing assumptions
of fundamental physics. The experiment, said her friend Wolfgang Pauli, the Austrian physicist, showed that “God is left-handed.” The discovery
of parity violation won the 1957 Nobel Prize for the two theorists who suggested it—Tsung-Dao Lee and Chen Ning Yang. Wu should have shared
that award but did not.
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The 2015 discovery of gravitational
waves by the Laser Interferometer Gravitational-
Wave Observatory (LIGO) in the US verified the prediction of general relativity: that violent events involving extremely massive astrophysical bodies, such as the merging of two black holes, produce ripples in space-time called gravitational waves. The experiment used an immense instrument in which light beams were sent and reflected back along two tubes that were each
four kilometers long. The distortions of space-time caused by a passing gravitational wave
change the way the light beams interfere when they return and cross one another.
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There are scientists who seem to have a talent for aesthetically pleasing experimental design—none more so than the New Zealand–born physicist Ernest Rutherford, who in 1908 discovered the dense atomic nucleus by scattering alpha particles from gold foil and subsequently proposed the “solar system” model of the atom, in which subatomic particles orbit one another in mostly empty space. A beautiful experiment marshals the available resources to disclose what casual inspection will not. For example, many biologists consider the 1958 experiment by Matthew Meselson and Franklin Stahl on how DNA replicates to be the most beautiful in their discipline. Their trick was turning a seemingly impossible puzzle—how to distinguish between possibilities whose outcomes look identical—into a soluble one by using atomic isotopes to create DNA strands that are chemically identical but physically separable.
An elegant experiment can look like a collaboration with nature to uncover “something deeply hidden,” as Einstein put it. Physics Nobel laureate Frank Wilczek has suggested that beauty in a scientific idea becomes manifest when you get out more than you put in: the idea delivers something new and unexpected.
When an experiment does that, we see science at its most magical: we ask a question of the universe, and it tells us something more. Every scientist longs for such moments, and treasures them if they come.
This story was excerpted from Beautiful Experiments: An Illustrated History of Experimental Science (2023).
