Analysis finds gender bias in peer-reviewer picks

Gender bias works in subtle ways, even in the scientific process. The latest illustration of that: Scientists recommend women less often than men as reviewers for scientific papers, a new analysis shows. That seemingly minor oversight is yet another missed opportunity for women that might end up having an impact on hiring, promotions and more.

Peer review is one of the bricks in the foundation supporting science. A researcher’s results don’t get published in a journal until they successfully pass through a gauntlet of scientific peers, who scrutinize the paper for faulty findings, gaps in logic or less-than-meticulous methods. The scientist submitting the paper gets to suggest names for those potential reviewers. Scientific journal editors may contact some of the recommended scientists, and then reach out to a few more.

But peer review isn’t just about the paper (and scientist) being examined. Being the one doing the reviewing “has a number of really positive benefits,” says Brooks Hanson, an earth scientist and director of publications at the American Geophysical Union in Washington, D.C. “You read papers differently as a reviewer than you do as a reader or author. You look at issues differently. It’s a learning experience in how to write papers and how to present research.”

Serving as a peer reviewer can also be a networking tool for scientific collaborations, as reviewers seek out authors whose work they admired. And of course, scientists put the journals they review for on their resumes when they apply for faculty positions, research grants and awards.

But Hanson didn’t really think of looking at who got invited to be peer reviewers until Marcia McNutt, a geophysicist and then editor in chief of Science, stopped by his office. McNutt — now president of the National Academy of Sciences in Washington, D.C. — was organizing a conference on gender bias, and asked if Hanson might be able to get any data. The American Geophysical Union is a membership organization for scientists in Earth and space sciences, and it publishes 20 scientific journals. If Hanson could associate the gender and age of the members with the papers they authored and edited, he might be able to see if there was gender bias in who got picked for peer review.

“We were skeptical at first,” he says. Hanson knew AGU had data for who reviewed and submitted papers to the journals, as well as data for AGU members. But he was unsure how well the two datasets would match up. To find out, he turned to Jory Lerback, who was then a data analyst with AGU. Merging the datasets of all the scientific articles submitted to AGU journals from 2012 to 2015 gave Lerback and Hanson a total of 24,368 paper authors and 62,552 peer reviews performed by 14,919 reviewers. For those papers, they had 97,083 author-named reviewer suggestions, and 118,873 editor-named reviewer requests.

While women were authors less often and submitted fewer papers, their papers were accepted 61 percent of the time. Male authors had papers accepted 57 percent of the time. “We were surprised by that,” Hanson says. While one reviewer of Hanson and Lerback’s analysis (a peer-reviewer on a paper about peer review surely must feel the irony) suggested that women might be getting higher acceptance rates due to reverse discrimination, Hanson disagrees. He wonders if “[women] are putting more care into the submission of the papers,” he says. Men might be more inclined to take more risks, possibly submitting papers to a journal that is beyond their work’s reach. Women, he says, might be more cautious.
When suggesting reviewers, male authors suggested female reviewers only 15 percent of the time, and male editors suggested women just 17 percent of the time. Female authors suggested women reviewers 21 percent of the time, and female editors suggested them 22 percent of the time. The result? Women made up only 20 percent of reviewers, even though 28 percent of AGU members are women and 27 percent of the published first authors in the study were women.

The Earth and space sciences have historically had far fewer women than men, but the numbers are improving for younger scientists. “We thought maybe people were just asking older people to review papers,” says Lerback. But when Lerback and Hanson broke out the results by age, they saw the gender discrepancy knew no age bracket. “It makes us more confident that this is a real issue and not just an age-related phenomenon,” Lerback says. She and Hanson report their analysis in a comment piece in the January 26 Nature.

“It’s incredibly compelling data and one of those ‘why hasn’t someone done this already’ studies,” says Jessi Smith, a social psychologist at Montana State University in Bozeman. While it’s disheartening to see yet another area of bias against women, she notes, “this is good that people are asking these questions and taking a hard look. We can’t solve it if we don’t know about it.”

The time when authors are asked to suggest reviewers might play a role, Smith notes. When scientific papers are submitted online, the field for “suggested reviewers” is often last. “That question for ‘who do you want’ always surprises me,” admits Smith. It’s a very small thing, but she notes that when people are tired and in a hurry, “that’s when these biases take place.”

Knowing that the bias exists is part of the battle, Hanson says, but it’s also time for things to change. He’s pushing for more diversity in the journals’ editorial pool — for gender, nationality and underrepresented minorities. It’s also helpful to remember that suggesting people for peer review isn’t just about the author’s work. “Even small biases, if they happen repeatedly, can have career-related effects,” he says.

Peer-reviewer selection is something that hasn’t gotten a lot of scientific attention. “I think getting a dialog going for everyone to be aware of opportunity gaps, [asking] ‘what can I do to make sure I’m not contributing to this’… I think that will be important to keep editors and authors aware and accountable,” Lerbeck says. She’s now experiencing the peer-review life first hand: She’s now a graduate student at the University of Utah in Salt Lake City. While there, she’s starting a group to discuss bias — to make sure that the conversations keep going.

Physically abused kids learn to fail at social rules for success

Physical abuse at home doesn’t just leave kids black and blue. It also bruises their ability to learn how to act at school and elsewhere, contributing to abused children’s well-documented behavior problems.

Derailment of a basic form of social learning has, for the first time, been linked to these children’s misbehavior years down the line, psychologist Jamie Hanson of the University of Pittsburgh and colleagues report February 3 in the Journal of Child Psychology and Psychiatry. Experiments indicate that physically abused kids lag behind their nonabused peers when it comes to learning to make choices that consistently lead to a reward, even after many trials.
“Physically abused kids fail to adjust flexibly to new behavioral rules in contexts outside their families,” says coauthor Seth Pollak, a psychologist at the University of Wisconsin–Madison. Youth who have endured hitting, choking and other bodily assaults by their parents view the world as a place where hugs and other gratifying responses to good behavior occur inconsistently, if at all. So these youngsters stick to what they learned early in life from volatile parents — rewards are rare and unpredictable, but punishment is always imminent. Kids armed with this expectation of futility end up fighting peers on the playground and antagonizing teachers, Pollak says.

If the new finding holds up, it could lead to new educational interventions for physically abused youth, such as training in how to distinguish safe from dangerous settings and in how to control impulses, Pollak says. Current treatments focus on helping abused children feel safe and less anxious.

More than 117,000 U.S. children were victims of documented physical abuse in 2015, the latest year for which data are available.

“Inflexible reward learning is one of many possible pathways from child maltreatment to later behavior problems,” says Stanford University psychologist Kathryn Humphreys, who did not participate in the new study. Other possible influences on physically abused kids’ disruptive acts include a heightened sensitivity to social stress and a conviction that others always have bad intentions, Humphreys suggests.

Hanson’s team studied 41 physically abused and 40 nonabused kids, ages 12 to 17. Participants came from various racial backgrounds and lived with their parents in poor or lower middle-class neighborhoods. All the youth displayed comparable intelligence and school achievement.
In one experiment, kids saw a picture of a bell or a bottle and were told to choose one to earn points to trade in for toys. Kids who accumulated enough points could select any of several desirable toys displayed in the lab, including a chemistry set and a glow-in-the-dark model of the solar system. Fewer points enabled kids to choose plainer toys, such as a Frisbee or colored pencils.

Over 100 trials, one picture chosen at random by the researchers at the start of the experiment resulted in points 80 percent of the time. The other picture yielded points 20 percent of the time. In a second round of 100 trials using pictures of a bolt and a button, one randomly chosen image resulted in points 70 percent of the time versus 30 percent for the other image.

Both groups chose higher-point images more often as trials progressed, indicating that all kids gradually learned images’ values. But physically abused kids lagged behind: They chose the more-rewarding image on an average of 131 out of 200 trials, compared with 154 out of 200 trials for nonabused youth. The abused kids were held back by what they had learned at home, Pollak suspects.

If you think the Amazon jungle is completely wild, think again

Welcome to the somewhat civilized jungle. Plant cultivation by native groups has shaped the landscape of at least part of South America’s Amazon forests for more than 8,000 years, researchers say.

Of dozens of tree species partly or fully domesticated by ancient peoples, 20 kinds of fruit and nut trees still cover large chunks of Amazonian forests, say ecologist Carolina Levis of the National Institute for Amazonian Research in Manaus, Brazil, and colleagues. Numbers and variety of domesticated tree species increase on and around previously discovered Amazonian archaeological sites, the scientists report in the March 3 Science.
Domesticated trees are “a surviving heritage of the Amazon’s past inhabitants,” Levis says.

The new report, says archaeologist Peter Stahl of the University of Victoria in Canada, adds to previous evidence that “resourceful and highly developed indigenous cultures” intentionally altered some Amazonian forests.

Southwestern and northwestern Amazonian forests contain the greatest numbers and diversity of domesticated tree species, Levis’ team found. Large stands of domesticated Brazil nut trees remain crucial resources for inhabitants of southwestern forests today.

Over the past 300 years, modern Amazonian groups may have helped spread some domesticated tree species, Levis’ group says. For instance, 17th century v­oyagers from Portugal and Spain established plantations of cacao trees in southwestern Amazonian forests that exploited cacao trees already cultivated by local communities, the scientists propose.

Their findings build on a 2013 survey of forest plots all across the Amazon led by ecologist and study coauthor Hans ter Steege of the Naturalis Biodiversity Center in Leiden, the Netherlands. Of approximately 16,000 Amazonian tree species, just 227 accounted for half of all trees, the 2013 study concluded.
Of that number, 85 species display physical features signaling partial or full domestication by native Amazonians before European contact, the new study finds. Studies of plant DNA and plant remains from the Amazon previously suggested that domestication started more than 8,000 years ago. Crucially, 20 domesticated tree species — five times more than the number expected by chance — dominate their respective Amazonian landscapes, especially near archaeological sites and rivers where ancient humans likely congregated, Levis’ team says.

Archaeologists, ecologists and crop geneticists have so far studied only a small slice of the Amazon, which covers an area equivalent to about 93 percent of the contiguous U.S. states.

Levis and her colleagues suspect ancient native groups domesticated trees and plants throughout much of the region. But some researchers, including ecologist Crystal McMichael of the University of Amsterdam, say it’s more likely that ancient South Americans domesticated trees just in certain parts of the Amazon. In the new study, only Brazil nut trees show clear evidence of expansion into surrounding forests from an area of ancient domestication, McMichael says. Other tree species may have mainly been domesticated by native groups or Europeans in the past few hundred years, she says.

Quantum counterfeiters might succeed

Scientists have created an ultrasecure form of money using quantum mechanics — and immediately demonstrated a potential security loophole.

Under ideal conditions, quantum currency is impossible to counterfeit. But thanks to the messiness of reality, a forger with access to sophisticated equipment could skirt that quantum security if banks don’t take appropriate precautions, scientists report March 1 in npj Quantum Information. Quantum money as a concept has been around since the 1970s, but this is the first time anyone has created and counterfeited quantum cash, says study coauthor Karel Lemr, a quantum physicist at Palacký University Olomouc in the Czech Republic.
Instead of paper banknotes, the researchers’ quantum bills are minted in light. To transfer funds, a series of photons — particles of light — would be transmitted to a bank using the photons’ polarizations, the orientation of their electromagnetic waves, to encode information. (The digital currency Bitcoin is similar in that there’s no bill you can hold in your hand. But quantum money has an extra layer of security, backed by the power of quantum mechanics.)

To illustrate their technique in a fun way, the researchers transmitted a pixelated picture of a banknote — an old Austrian bill depicting famed quantum physicist Erwin Schrödinger — using photons’ polarizations to stand for grayscale shades. In a real quantum money system, each bill would be different and the photon polarizations would be distributed randomly, rather than forming a picture. The polarizations would create a serial number–like code the bank could check to verify that the funds are legit.

A criminal intercepting the photons couldn’t copy them accurately because quantum information can’t be perfectly duplicated. “This is actually the cornerstone of security of quantum money,” says Lemr.
But the realities of dealing with quantum particles complicate matters. Because single photons are easily lost or garbled during transmission, banks would have to accept partial quantum bills, analogous to a dollar with a corner torn off. That means a crook might be able to make forgeries that aren’t perfect, but are good enough to pass muster.
Lemr and colleagues used an optimal cloner, a device that comes as close as possible to copying quantum information, to attempt a fake. The researchers showed that a bank would accept a forged bill if the standard for accuracy wasn’t high enough — more than about 84 percent of the received photons’ polarizations must match the original.

Previously, this vulnerability “wasn’t explicitly pointed out, but it’s not surprising,” says theoretical computer scientist Thomas Vidick of Caltech, who was not involved in the research. The result, he says, indicates that banks must be stringent enough in their standards to prove the bills they receive are real.

Most Americans like science — and are willing to pay for it

Americans don’t hate science. Quite the contrary. In fact, 79 percent of Americans think science has made their lives easier, a 2014 Pew Research Center survey found. More than 60 percent of people also believe that government funding for science is essential to its success.

But should the United States spend more money on scientific research than it already does? A layperson’s answer to that question depends on how much that person thinks the government already spends on science, a new study shows. When people find out just how much — or rather, how little — of the federal budget goes to science, support for more funding suddenly jumps.

To see how people’s opinions of public science spending were influenced by accurate information, mechanical engineer Jillian Goldfarb and political scientist Douglas Kriner, both at Boston University, placed a small experiment into the 2014 Cooperative Congressional Election Study. The online survey was given to 1,000 Americans, carefully selected to represent the demographics of the United States. The questions were designed to be nonpartisan, and the survey itself was conducted in 2014, long before the 2016 election.

The survey was simple. First, participants were asked to estimate what percentage of the federal budget was spent on scientific research. Once they’d guessed, half of the participants were told the actual amount that the federal government allocates for nondefense spending on research and development. In 2014, that figure was 1.6 percent of the budget, or about $67 billion. Finally, all the participants were asked if federal spending on science should be increased, decreased or kept the same.

The majority of participants had no idea how much money the government spends on science, and wildly overestimated the actual amount. About half of the respondents estimated federal spending for research at somewhere between 5 and 20 percent of the budget. A quarter of participants estimated that figure was 20 percent of the budget — one very hefty chunk of change. The last 25 percent of respondents estimated that 1 to 2 percent of federal spending went to science.

When participants received no information about how much the United States spent on research, only about 40 percent of them supported more funding. But when they were confronted with the real numbers, support for more funding leapt from 40 to 60 percent.

Those two numbers hover on either side of 50 percent, but Kriner notes, “media coverage [would] go from ‘minority’ to ‘majority’” in favor of more funding — a potentially powerful message. What’s more, the support for science was present in Democrats and Republicans alike, Kriner and Goldfarb report February 1 in Science Communication.
“I think it contributes to our understanding of the aspects of federal spending that people don’t understand very well,” says Brendan Nyhan, a political scientist at Dartmouth University in Hanover, N.H. It’s not surprising that most people don’t know how much the government is spending on research. Nyhan points out that most people probably don’t know how much the government spends on education or foreign aid either.

When trying to gather more support for science funding, Goldfarb says, “tell people how little we spend, and how much they get in return.” Science as a whole isn’t that controversial. No one wants to stop exploring the universe or curing diseases, after all.

But when people — whether politicians or that guy in your Facebook feed — say they want to cut science funding, they won’t be speaking about science as a whole. “There’s a tendency to overgeneralize” and use a few controversial or perceived-to-be-wasteful projects to stand in for all of science, Nyhan warns.

When politicians want to cut funding, he notes, they focus on specific controversial studies or areas — such as climate change, stem cells or genetically modified organisms. They might highlight studies that seem silly, such as those that ended up in former Senator Tom Coburn’s “Wastebook,” (a mantle now taken up Senator Jeff Flake). Take those issues to the constituents, and funding might end up in jeopardy anyway.

Kriner hopes their study’s findings might prove useful even for controversial research areas. “One of the best safeguards against cuts is strong public support for a program,” he explains. “Building public support for science spending may help insulate it from budget cuts — and our research suggests a relatively simple way to increase public support for scientific research.”

But he worries that public support may not stay strong if science becomes too much of a political pawn. The study showed that both Republicans and Democrats supported more funding for science when they knew how little was spent. But “if the current administration increases its attacks on science spending writ large … it could potentially politicize federal support for all forms of scientific research,” Kriner says. And the stronger the politics, the more people on both sides of the aisle grow resistant to hearing arguments from the other side.

Politics aside, Goldfarb and Kriner’s data show that Americans really do like and support science. They want to pay for it. And they may even want to shell out some more money, when they know just how little they already spend.

Volcanic eruptions nearly snuffed out Gentoo penguin colony

Penguins have been pooping on Ardley Island off the coast of the Antarctic Peninsula for a long, long time. The population there is one of the biggest and oldest Gentoo penguin (Pygoscelis papua) colonies. But evidence from ancient excrement suggests that these animals didn’t always flourish.

Stephen Roberts of the British Antarctic Survey and colleagues set out to see how the Ardley population responded to past changes in climate to better inform future conservation efforts. The researchers studied the geochemical makeup of lake sediment samples and identified elements from penguin guano. Knowing the fraction of guano in lake sludge over time let the researchers track penguin population changes.

The Gentoo penguin colony was nearly wiped out three times over the 6,700 years that the penguins have occupied Ardley Island. But rather than lining up with changes in temperature or sea ice levels, these population dips corresponded to volcanic ash preserved in the geologic record from big eruptions of a volcano on nearby Deception Island. After each population crash, the colony took 400 to 800 years to recover, the team reports April 11 in Nature Communications.

Trackers may tip a warbler’s odds of returning to its nest

Strapping tiny trackers called geolocators to the backs of birds can reveal a lot about where the birds go when they migrate, how they get there and what happens along the way. But ornithologists are finding that these cool backpacks could have not-so-cool consequences.

Douglas Raybuck of Arkansas State University and his colleagues outfitted some Cerulean warblers (Setophaga cerulea) with geolocators and some with simple color tags to test the effects the locators might have on breeding and reproduction. This particular species globe-trots from its nesting grounds in the eastern United States to wintering grounds in South America and back each year. While the backpacks didn’t affect reproduction, birds wearing the devices were less likely than those wearing tags to return to the same breeding grounds the next year. The birds may have gotten off track, cut their trips short or died, possibly due to extra weight or drag from the backpack, the team reports May 3 in The Condor.

The study adds to conflicting evidence that geolocators affect some birds in negative ways, such as altering their breeding biology. At best, potential downsides vary from bird to bird and backpack to backpack. But that shouldn’t stop researchers from using geolocators to study migrating birds, the researchers argue, because the devices pinpoint areas crucial to migrating birds and can aid in conservation efforts.

Readers puzzled by proton’s properties

Proton puzzler
Uncertainty over the proton’s size, spin and life span could have physicists rethinking standard notions about matter and the universe, Emily Conover reported in “The proton puzzle” (SN: 4/29/17, p. 22).

Readers wondered about the diameter (or size) of the proton, which has three fundamental particles called quarks rattling around inside. “Still scratching my head over how combining three dimensionless quarks ends up forming a proton with a ‘diameter,’ ” online reader Down_Home wrote. “Maybe that word doesn’t mean what I think it means.”
The three quarks within the proton are only apparent when the proton is probed with high-energy particles, Conover says. At lower energies, particles “see” the entire proton as one entity. “In that case, the proton just behaves like a sphere of positive charge,” she says. Scientists measure the size of this sphere by looking at how electrons are deflected when they come close to the proton. “Researchers disagree on the sphere’s diameter, which makes for a bit of an identity crisis for the proton,” Conover says.

Blooming Arctic
Nearly 30 percent of ice covering the Arctic Ocean at summer’s peak is thin enough to foster sprawling phytoplankton blooms in the waters below, a recent study estimated. These ice-covered blooms were probably uncommon just 20 years ago, Thomas Sumner reported in “Thinning ice creates undersea greenhouses in the Arctic” (SN: 4/29/17, p. 20).

Several online readers wanted to know how the under-ice blooms get the carbon dioxide they need to photosynthesize.
Others wondered about the blooms’ potential effect on climate. “I’m not sure if this is good or bad news,” reader Witch Daemon wrote. More phytoplankton could mean that the Arctic could store more carbon, but the blooms wouldn’t exist if it weren’t for warming and melting ice, Witch Daemon reasoned.
When phytoplankton are trapped under ice, they absorb CO2 that’s dissolved in the upper ocean, says oceanographer and study coauthor Christopher Horvat of Harvard University.

What the blooms might mean for storing carbon in the ocean is uncertain, Horvat says. But if these under-ice blooms occur in addition to the familiar blooms along the edges of the ice, then there’s a chance that more carbon could be stored away.

Shields up
Most of the gases in Mars’ atmosphere may have been stripped away by solar wind, Ashley Yeager reported in “Extreme gas loss dried out Mars” (SN: 4/29/17, p. 20). The loss of so much gas may explain how the planet morphed from a wet, warm world to a dry, icy one.

Online reader Robert Knox wondered how long it took for the solar wind to strip Mars of its atmospheric gases. “Earth is closer to the sun, so the solar wind is more intense,” Knox wrote. “Why did this not happen to Earth?”

Luckily for us, Earth is protected by a magnetic field, Yeager says. This field deflects the solar wind and prevents it from picking away at the planet’s atmospheric particles. Mars lost most of its global magnetic field about 4.2 billion years ago, which allowed the solar wind to sweep away much of the planet’s atmosphere over a few hundred million years, she says.

Top 10 discoveries about waves

Physics fans are a lot like surfers. Both think waves are really fun.

For surfers, it’s all about having a good time. For physicists, it’s about understanding some of nature’s most important physical phenomena. Yet another detection of gravitational waves, announced June 1, further reinvigorates the world’s science fans’ excitement over waves.

Waves have naturally always been a topic of scientific and mathematical interest. They play a part in an enormous range of physical processes, from heat and light to radio and TV, sonograms and music, earthquakes and holograms. (Waves used to even be a common sight in baseball stadiums, but fans got tired of standing up and down and it was really annoying anyway.)

Many of science’s greatest achievements have been discoveries of new kinds of waves or new insights into wave motion. Identifying just the Top 10 such discoveries (or ideas) is therefore difficult and bound to elicit critical comments from cult members of particular secret wave societies. So remember, if your favorite wave isn’t on this list, it would have been No. 11.

  1. Thomas Young: Light is a wave.
    In the opening years of the 19th century, the English physician Young tackled a long-running controversy about the nature of light. A century earlier, Isaac Newton had argued forcibly for the view that light consisted of (very small) particles. Newton’s contemporary Christiaan Huygens strongly disagreed, insisting that light traveled through space as a wave.

Through a series of clever experiments, Young demonstrated strong evidence for waves. Poking two tiny holes in a thick sheet of paper, Young saw that light passing through created alternating bands of light and darkness on a surface placed on the other side of the paper. That was just as expected if light passing through the two holes interfered just as water waves do, canceling out when crest met trough or enhancing when crests met “in phase.” Young did not work out his wave theory with mathematical rigor and so Newton’s defenders resisted, attempting to explain away Young’s results.

But soon Augustin Jean Fresnel in France worked out the math of light waves in detail. And in 1850, when Jean-Bernard-Léon Foucault showed that light travels faster in air than water, the staunchest Newton fans had to capitulate. Newton himself would have acknowledged that light must therefore consist of waves. (Much later, though, Einstein found a way that light could in fact consist of particles, which came to be called photons.)

  1. Michelson and Morley: Light waves don’t vibrate anything.
    Waves are vibrations, implying the need for something to vibrate. Sound vibrated molecules in the air, for instance, and ocean waves vibrated molecules of water. Light, supposedly, vibrated an invisible substance called the ether.

In 1887, Albert A. Michelson and his collaborator Edward Morley devised an experiment to detect that ether. Earth’s motion through the ether should have meant that light’s velocity would depend on its direction. (Traveling with the Earth’s motion, light’s speed wouldn’t be the same as traveling at right angles to the direction of motion.) Michelson and Morley figured they could detect that difference by exploiting the interference phenomena discovered by Young. But their apparatus failed to find any ether effect. They thought their experiment was flawed. But later Einstein figured out there actually wasn’t any ether.

  1. James Clerk Maxwell: Light is an electromagnetic wave.
    Maxwell died in 1879, the year Einstein was born, and so did not know there wasn’t an ether. He did figure out, though, that both electricity and magnetism could be explained by stresses in some such medium.

Electric and magnetic charges in the ether ought to generate disturbances in the form of waves, Maxwell realized. Based on the strengths of those forces he calculated that the waves would travel at the fantastic speed of 310 million meters per second, suspiciously close to the best recent measurements of the speed of light (those measurements ranged from 298 million to 315 million meters per second). So Maxwell, without the benefit of ever having watched NCIS on TV, then invoked Gibbs’ Rule 39 (there’s no such thing as a coincidence) and concluded that light was an example of an electromagnetic wave.

“It seems we have strong reason to conclude that light itself (including radiant heat, and other radiations if any) is an electromagnetic disturbance in the form of waves propagated through the electromagnetic field,” he wrote in 1864. His “other radiations, if any” turned out to be an entire spectrum of all sorts of cool waves, from gamma radiation to radio signals.

  1. Heinrich Hertz: Radio waves.
    Not very many people took Maxwell seriously at first. A few, though, known as the Maxwellians, promoted his ideas. One physicist who had faith in Maxwell, or at least in his equations, was Hertz, who performed experiments in his lab in Karlsruhe, Germany, that successfully produced and detected radio waves, eventually to be exploited by propagandists to spread a lot of illogical nonsense on talk radio.

His success inspired much more respect for the equations in Maxwell’s theory, which Hertz found almost magical: “It is impossible to study this wonderful theory without feeling as if the mathematical equations had an independent life and an intelligence of their own, as if they were wiser than ourselves,” Hertz said. His prime experimental success came in 1887, the same year that Michelson and Morley failed to detect the ether. Hertz died in 1894, long before his discovery was put to widespread use.

  1. John Michell: Seismic waves.
    Michell, an English geologist and astronomer, was motivated by the great Lisbon earthquake of 1755 to investigate the cause of earthquakes. In 1760 he concluded that “subterraneous fires” should be blamed, noting that volcanoes — “burning mountains” — commonly occur in the same neighborhood as frequent earthquakes.

Michell noted that “the motion of the earth in earthquakes is … partly propagated by waves, which succeed one another sometimes at larger and sometimes at smaller distances.” He cited witness accounts of quakes in which the ground rose “like the sea in a wave.” Much later seismologists developed a more precise understanding of the seismic waves that shake the Earth, using them as probes to infer the planet’s inner structure.

  1. Wilhelm Röntgen: X-rays.
    When Hertz discovered radio waves, he knew he was looking for the long-wavelength radiation foreshadowed in Maxwell’s equations. But a few years later, in 1895, Röntgen found the radio wave counterpart of the opposite end of the electromagnetic spectrum — by accident.
    Mysterious short-wavelength rays of an unknown type (therefore designated X) emerged when Röntgen shot cathode rays (beams of electrons) through a glass tube. Röntgen suspected that his creation might be a new kind of wave among the many Maxwell had anticipated: “There seems to exist some kind of relationship between the new rays and light rays; at least this is indicated by the formation of shadows,” Röntgen wrote. Those shadows, of course, became the basis for a revolutionary medical technology.

Besides providing a major new tool for observing shattered bones and other structures inside the body, X-rays eventually became essential tools for scientific investigation in astronomy, biology and other fields. And they shattered the late 19th century complacency of physicists who thought they’d basically figured everything out about nature. Weirdly, though, X-rays later turned out to be particles sometimes, validating Einstein’s ideas that light had an alter ego particle identity. (By the way, it turned out that X-rays aren’t the electromagnetic waves with the shortest wavelengths — gamma rays can be even shorter. Maybe they would be No. 11.)

  1. Epicurus: The swerve.
    Not exactly a wave in the ordinary sense, the swerve was a deviation from straight line motion postulated by the Greek philosopher Epicurus around 300 B.C. Unlike Aristotle, Epicurus believed in atoms, and argued that reality was built entirely from the random collisions of an infinite number of those tiny particles. Supposedly, he thought, atoms would all just fall straight down to the center of the universe unless some unpredictable “swerve” occasionally caused them to deviate from their paths so they would bounce off each other and congregate into complex structures.

It has not escaped the attention of modern philosophers that the Epicurean unpredictable swerve is a bit like the uncertainty in particle motions introduced by quantum mechanics. Which has its own waves.

  1. Louis de Broglie: Matter waves.
    In the early 1920s, de Broglie noticed a peculiar connection between relativity and quantum physics. Max Planck’s famous quantum formula related energy to frequency of a wave motion. Einstein’s special relativity related energy to the mass of a particle. De Broglie thought it would make a fine doctoral dissertation to work out the implications of two seemingly separate things both related to energy. If energy equals mass (times the speed of light squared) and energy equals frequency (time Planck’s constant), then voilà, mass equals frequency (times some combination of the constants). Therefore, de Broglie reasoned, particles (of mass) ought to also exist as waves (with a frequency).

That might have seemed wacky, but Einstein read de Broglie’s thesis and thought it made sense. Soon Walter Elsasser in Germany reported experiments that supported de Broglie, and in America Clinton Davisson and coworkers demonstrated conclusively that electrons did in fact exhibit wave properties.

De Broglie won the physics Nobel Prize in 1929; Davisson shared the 1937 Nobel with George Thomson, who had conducted similar experiments showing electrons are waves. Which was ironic, because George’s father, J.J. Thomson, won the 1906 Nobel for the work that revealed the existence of the electron as a particle. Eight decades later Ernst Ruska won a Nobel for his design of a powerful microscope that exploited the electron’s wave behavior.

  1. Max Born: Probability waves.
    De Broglie’s idea ignited a flurry of activity among physicists trying to figure out how waves fit into quantum theory. Niels Bohr, for instance, spent considerable effort attempting to reconcile the dual wave-particle nature of both electrons and light. Erwin Schrödinger, meanwhile, developed a full-fledged “wave mechanics” to describe the behavior of electrons in atoms solely from the wave perspective. Schrödinger’s math incorporated a “wave function” that was great for calculating the expected results of experiments, even though some experiments clearly showed electrons to be particles.

Born, a German physicist and good friend of Einstein’s, deduced the key to clarifying the wave function: It was an indicator of the probability of finding the particle in a given location. Combined with Werner Heisenberg’s brand-new uncertainty principle, Born’s realization led to the modern view that an electron is wavelike in the sense that it does not possess a definite location until it is observed. That approach works fine for all practical purposes, but physicists and philosophers still engage in vigorous debates today about the true physical status of the wave function.

  1. LIGO: Gravitational waves.
    Soon after he completed his general theory of relativity, Einstein realized that it implied the possibility of gravitational radiation — vibrations of spacetime itself. He had no idea, though, that by spending a billion dollars, physicists a century later could actually detect those spacetime ripples. But thanks to lasers (which maybe would have been No. 11), the Laser Interferometer Gravitational-Wave Observatory — two huge labs in Louisiana and Washington state — captured the spacetime shudders emitted from a pair of colliding black holes in September 2015.
    That detection is certainly one of the most phenomenal experimental achievements in the history of science. It signaled a new era in astronomy, providing astronomers a tool for probing the depths of the universe that are obscured from view with Maxwell’s “other radiations, if any.” For astronomy, gravitational radiation is the wave of the future.

Flight demands may have steered the evolution of bird egg shape

The mystery of why birds’ eggs come in so many shapes has long been up in the air. Now new research suggests adaptations for flight may have helped shape the orbs.

Stronger fliers tend to lay more elongated eggs, researchers report in the June 23 Science. The finding comes from the first large analysis of the way egg shape varies across bird species, from the almost perfectly spherical egg of the brown hawk owl to the raindrop-shaped egg of the least sandpiper.
“Eggs fulfill such a specific role in birds — the egg is designed to protect and nourish the chick. Why there’s such diversity in form when there’s such a set function was a question that we found intriguing,” says study coauthor Mary Caswell Stoddard, an evolutionary biologist at Princeton University.

Previous studies have suggested many possible advantages for different shapes. Perhaps cone-shaped eggs are less likely to roll out of the nest of cliff-dwelling birds; spherical eggs might be more resilient to damage in the nest. But no one had tested such hypotheses across a wide spectrum of birds.

Stoddard and her team analyzed almost 50,000 eggs from 1,400 species, representing about 14 percent of known bird species. The researchers boiled each egg down to its two-dimensional silhouette and then used an algorithm to describe each egg using two variables: how elliptical versus spherical the egg is and how asymmetrical it is — whether it’s pointier on one end than the other.

Next, the researchers looked at the way these two traits vary across the bird family tree. One pattern jumped out: Species that are stronger fliers, as measured by wing shape, tend to lay more elliptical or asymmetrical eggs, says study coauthor L. Mahadevan, a mathematician and biologist at Harvard University.
Mahadevan cautions that the data show only an association, but the researchers propose one possible explanation for the link between flying and egg shape. Adapting to flight streamlined bird bodies, perhaps also narrowing the reproductive tract. That narrowing would have limited the width of an egg that a female could lay. But since eggs provide nutrition for the chick growing inside, shrinking eggs too much would deprive the developing bird. Elongated eggs might have been a compromise between keeping egg volume up without increasing girth, Stoddard suggests. Asymmetry can increase egg volume in a similar way.

Testing a causal connection between flight ability and egg shape is tough “because of course we can’t replay the whole tape of life again,” says Claire Spottiswoode, a zoologist at the University of Cambridge who wrote a commentary accompanying the study. Still, Spottiswoode says the evidence is compelling: “It’s a very plausible argument.”

Santiago Claramunt, associate curator of ornithology at the Royal Ontario Museum in Toronto, isn’t convinced that flight adaptations played a driving role in the evolution of egg shape. “Streamlining in birds is determined more by plumage than the shape of the body — high performing fliers can have rounded, bulky bodies” he says, which wouldn’t give elongated eggs the same advantage over other egg shapes. He cites frigate birds and swifts as examples, both of which make long-distance flights but have fairly broad bodies. “There’s certainly more going on there.”

Indeed, some orders of birds showed a much stronger link between flying and egg shape than others did. And while other factors — like where birds lay their eggs and how many they lay at once — weren’t significantly related to egg shape across birds as a whole, they could be important within certain branches of the bird family tree.