In other star systems, some moons could escape their planets and start orbiting their stars instead, new simulations suggest. Scientists have dubbed such liberated worlds “ploonets,” and say that current telescopes may be able to find the wayward objects.
Astronomers think that exomoons — moons orbiting planets that orbit stars other than the sun — should be common, but efforts to find them have turned up empty so far (SN Online: 4/30/19). Astrophysicist Mario Sucerquia of the University of Antioquia in Medellín, Colombia and colleagues simulated what would happen to those moons if they orbited hot Jupiters, gas giants that lie scorchingly close to their stars (SN: 7/8/17, p. 4). Many astronomers think that hot Jupiters weren’t born so close, but instead migrated toward their star from a more distant orbit. As the gas giant migrates, the combined gravitational forces of the planet and the star would inject extra energy into the moon’s orbit, pushing the moon farther and farther from its planet until eventually it escapes, the researchers report June 27 at arXiv.org.
“This process should happen in every planetary system composed of a giant planet in a very close-in orbit,” Sucerquia says. “So ploonets should be very frequent.”
Some ploonets may be indistinguishable from ordinary planets. Others, whose orbits keep them close to their planet, could reveal their presence by changing the timing of when their neighbor planet crosses, or transits, in front of the star. The ploonet should stay close enough to the planet that its gravity can speed or slow the planet’s transit times. Those deviations should be detectable by combining data from planet-hunting telescopes like NASA’s TESS or the now-defunct Kepler, Sucerquia says. Ploonethood may be a relatively short-lived phenomenon, though, making the worlds more difficult to spot. About half of the ploonets in the researchers’ simulations crashed into either their planet or star within about half a million years. And half of the remaining survivors crashed within a million years.
Even with few visible survivors, ploonets could help explain some bizarre exoplanetary features. Moon debris from such crashes could lead to giant ring systems around planets, like the 37 rings that encircle exoplanet J1407b, the team says.
Or, if the ploonet had an icy surface or an atmosphere before moving close to its star, the star’s heat would evaporate it, giving the ploonet a tail like a comet’s. Evaporating ploonets zipping by with a long light-blocking tail could explain strangely flickering stars like Tabby’s star, Sucerquia says (SN: 12/22/18, p. 9).
“Those structures [rings and flickers] have been discovered, have been observed,” Sucerquia says. “We just propose a natural mechanism to explain [them].”
While the solar system doesn’t have any hot Jupiters, ploonethood may be possible here, too. Earth’s moon is moving slowly away from the Earth, at a rate of about 4 centimeters per year. When it eventually breaks free, “the moon is a potential ploonet,” Sucerquia says — although that won’t happen for about 5 billion years.
The study is a good first step for thinking about what would happen to exomoons in real planetary systems, says planetary astrophysicist Natalie Hinkel of the Southwest Research Institute in San Antonio, who wasn’t involved in the new work. “Nobody’s looked at the problem quite like this,” she says. “It adds to the layers of how complex these systems are.”
Plus, ploonet is “a wonderful name,” Hinkel says. “Normally I sort of eye-roll at these made-up names, but this one is a keeper.”
A praying mantis depends on precision targeting when hunting insects. Now, scientists have identified nerve cells that help calculate the depth perception required for these predators’ surgical strikes.
In addition to providing clues about insect vision, the principles of these cells’ behavior, described June 28 in Nature Communications, may also lead to advances in robot vision or other automated systems.
So far, praying mantises are the only insects known to be able to see in 3-D. In the new study, neuroscientist Ronny Rosner of Newcastle University in England and colleagues used a tiny theater that played praying mantises’ favorite films — moving disks that mimic bugs. The disks appeared in three dimensions because the insects’ eyes were covered with different colored filters, creating minuscule 3-D glasses. As a praying mantis watched the films, electrodes monitored the behavior of individual nerve cells in the optic lobe, a brain structure responsible for many aspects of vision. There, researchers found four types of nerve cells that seem to help merge the two different views from each eye into a complete 3-D picture, a skill that human vision cells use to sense depth, too.
One cell type called a TAOpro neuron possesses three elaborate, fan-shaped bundles that receive incoming visual information. Along with the three other cell types, TAOpro neurons are active when each eye’s view of an object is different, a mismatch that’s needed for depth perception.
The details of the various types of nerve cells, and how they might receive, combine and send visual information, suggest that these insects’ vision may be more sophisticated than some scientists had thought, the team writes. And the principles guiding praying mantis depth perception may be useful to researchers working on improving machine vision, perhaps allowing artificial systems to better sense the depths of objects.
A new biomaterial delivered to the heart soon after a heart attack can heal damaged tissue from the inside out.
Heart attacks kill cardiac muscle tissue, scarring the heart and leaving permanent damage after just six hours. The damage prevents the heart from functioning properly. If there was a way to begin healing damaged tissue soon after a heart attack, doctors could prevent scar tissue from developing.
“In an ideal world, you treat a patient immediately when they’re having a heart attack to try to salvage some of the tissue and promote regeneration,” says Karen Christman, a bioengineer at the University of California, San Diego. The pursuit of this ideal inspired Christman, along with a team of researchers, to develop the biomaterial. In rodents and pigs, it appears to repair tissue damage and reduce inflammation directly after a heart attack, Christman and colleagues report December 29 in Nature Biomedical Engineering.
“I think it has a lot of potential,” Vimala Bharadwaj, a biomedical scientist at Stanford University who was not involved in the research. The paper “is definitely good proof of concept for what they’re trying to do.”
Previously, researchers found that stem cells derived from body fat can be used to heal bones, muscles and the heart (SN: 3/9/16). Christman wanted to work with the extracellular matrix, the lattice of proteins that provide structural support to the cells in cardiac muscle tissue. Like stems cells, it has regenerative abilities but is much less expensive, she says.
In 2009, Christman’s team produced a hydrogel using particles from this matrix. Trials in rats and later in humans showed that the material bonded to damaged areas and promoted cell repair and growth. However, due to relatively large particles of the hydrogel, it could be delivered to the heart only via a needle.
“Poking the heart with a needle could set off an arrhythmia,” says Christman. To use this treatment, doctors would need to wait a few weeks until the heart is more stable and the chance of these irregular heartbeats decreases. And that would be too late to prevent scarring.
The team took the previously created hydrogel, sifted out the larger particles with a centrifuge so only nanoparticles remained, and added water to dilute the mixture. That created a material thin enough to deliver to heart blood vessels intravenously. Based on the nanoparticles’ size, the team expected the mixture would slip through any gaps in cardiac blood vessels caused by the heart attack and adhere to the surrounding tissue. Once there, it would create a protective barrier while the heart healed.
Instead, animal experiments showed that the extracellular matrix material bound to the leaky vessels, preventing some inflammatory cells from moving into the heart tissue in the first place and causing further damage. The material reduced inflammation in the heart and stimulated the healing process by encouraging cell growth, the team reports.
Further safety studies will be needed to get the biomaterial ready for clinical trials. The first trial in humans will most likely be for repairing cardiac tissue post–heart attack. “A lot of my motivation is moving things out of the lab, actually into the real world,” Christman says.
Another real-world application of the biomaterial could be treatment for leaky blood vessels in other hard-to-access organs, including in the brain after a traumatic injury, Christman notes.
While Bharadwaj finds that application potentially promising, she says tests are needed to see whether the biomaterial improves headaches and cognitive or memory deficits in the brain after a traumatic injury. That’s needed to gauge whether it really is an effective TBI treatment.
As early as 252 million years ago, some plants may have curled up their leaves at night for a cozy “sleep.”
Fossilized leaves of two now-extinct Gigantonoclea species bear signs of nyctinasty, or circadian rhythmic folding at night, researchers report February 15 in Current Biology. That would make these specimens the first known fossilized examples of this curious plant behavior, the team says.
The two leaf fossils were discovered in a rock layer in southwestern China that dates to between 259 million and 252 million years ago. In both species, the leaves were broad, with serrated edges. But most curiously, they bear oddly symmetrical holes. Insects made those holes while feeding on the leaves while they were folded, say paleontologist Zhuo Feng of Yunnan University in Kunming, China and colleagues. Similar symmetrical patterns of insect damage in leaf fossils can be used to distinguish folding behavior from leaves that might have shriveled as the plant died, the team says.
Modern plants, including many in the legume family such as the orchid tree, that fold and unfold their leaves use specialized cells called pulvinus cells, which act somewhat like muscles (SN: 2/3/23). By shifting water from one part of the leaf to another, the cells can bloat or deflate, allowing the leaves to fold or curl.
These cells would be at the base of the leaves, which weren’t preserved in the fossils, so it’s not possible to say whether these ancient plants also had pulvinus cells, the team says. Although it’s also hard to prove this was nighttime behavior, the leaves would also have had to be folded long enough for insects to do their munching. But the find does suggest that such leaf folding emerged independently in different plant lineages: Nearly all the modern plants that do this are angiosperms, or flowering plants. But Gigantonoclea plants were gymnosperms, seed-producing plants such as conifers and ginkgos.
A focus on family might be the key to personal well-being.
Surveys in the social sciences, such as those measuring happiness or health, tend to focus on the smallest unit: the individual. But two new studies, each surveying over 10,000 people worldwide, show that primary unit of analysis may need scaling up. One study suggests that people adhere to public health guidelines less to protect themselves than their loved ones. And the other study provides an explanation for why that may be the case: People the world over prioritize family happiness over their own. Neither research team defined the term “family,” instead allowing respondents to interpret the term as they saw fit. As such, the results suggest that the exact nature of family, whether nuclear, blood-related or extended, does not matter.
The findings have important implications for society, says Karen Bogenschneider, a family policy expert at the University of Wisconsin–Madison who was not involved with either study. That’s because policy makers occasionally rely on research findings to develop programs such as those aimed at reducing substance abuse or inequality. When researchers frame societal issues in terms of the individual or community, so too do policy makers. And those programs may be less effective as a result.
For instance, several studies in the past couple decades have shown that including family members in addiction treatment programs lowers the addict’s risk of relapse and improves family relationships.
Moreover, these studies challenge the assumption that individualism has turned the self into the most important unit of survival (SN: 10/7/19).
Family bonds drove individuals to adopt pandemic-related health behaviors The idea that policy makers can target family to change behavior comes as no surprise to Martha Newson, an anthropologist at Kent University in England. For years, Newson has studied a concept known as fusion, where an individual becomes so enmeshed in a larger social unit that she or he is willing to sacrifice personal well-being, or even survival, for the group (SN: 6/23/16).
At the onset of the pandemic, Newson and her team began studying how social fusion might be influencing behavior around the world during the pandemic. From March to May 2020, over 13,000 participants from 122 countries were shown a sequence of five pictures, each with two circles, one for the self and the other for a given group such as family, country or all of humankind. In the first picture, the circles are far apart, but in subsequent pictures they grow closer and closer together until they fully overlap. Participants had to select one of the five pictures to indicate their level of fusion with the group. A participant had to select the fully overlapping circles to be considered fused to the group.
Participants also filled out scales to indicate how much they had performed a given public health action, such as social distancing or masking, in the previous week.
Participants who were fused to family were overrepresented among those reporting strong adherence to public health guidelines, Newson and colleagues reported January 13 in Science Advances. For instance, despite representing roughly a quarter of the participant pool, participants with strong family bonds constituted three-quarters of those who reported following social distancing guidelines. And almost half of participants with strong family bonds reported frequent handwashing compared with about one-third of participants with weaker family bonds.
Humans evolved in small-scale societies, Newson says. “When we have crises … these smaller units remain very important.”
On average, people value family happiness more than their own Meanwhile, another group of researchers had begun to question the widely accepted belief that many happy individuals sum up to a happy society. That idea originated in the West, and has often been treated as universal, says Kuba Krys, a cross-cultural psychologist at the Polish Academy of Sciences in Warsaw.
But research over the years has indicated that non-Westerners may not value personal happiness as much as people in the West. For instance, outside the West, people tend to see happiness as more interdependent, or grounded in harmony and balance with others, than independent, or grounded in the self.
If happiness exists at least partially outside the individual, then Krys and his team wondered what unit researchers should study. They looked to family.
The team had roughly 13,000 participants from 49 countries indicate how much the perfect or ideal person would agree with statements in two commonly used surveys of well-being. Statements appeared both in the standard “I” framing and in a new family framing. For instance, participants reflected on how the ideal person would respond to both the statements, “In most ways, my life is close to ideal” and “In most ways, the life of my family is close to ideal.”
Nearly half of the participants valued family well-being over personal well-being, while less than a third preferred their own happiness, the team reports in an upcoming paper in the Journal of Cross-Cultural Psychology. Moreover, participants in even the most individualistic countries, including the United States, valued family, on average, more than self. The word “family” has become associated with conservativism, Krys says. But family remains central to people’s lives, regardless of geography or political affiliation. “The shape of family has changed but family as an idea, as a basic unit, has not changed,” he says. “I would advise progressives … not to be afraid of touching on family topics.”
Bogenschneider’s research backs up this point. In a study of more than 200 state legislators, she and colleagues found that while abortion and same-sex marriage remain highly polarized, policy makers tend to view other family issues, such as those involving domestic violence, juvenile crime or teen pregnancy, as largely bipartisan.
This suggests that issues that aren’t typically centered around family, such as climate change or inequality, could be framed in terms of family to garner wider support, Bogenschneider says. Researchers who are seeking to translate their findings into policy and advocates who are advancing particular causes could, she adds, “elevate policy makers’ interest in those issues by focusing on families and family contributions.”
It turns out that certain behaviors in domestic cats could be telltale signs that an interaction is friendly, aggressive or something in between, researchers report January 26 in Scientific Reports.
“It is a question we hear a lot from cat owners,” says cat behavior expert Mikel Delgado of Feline Minds, a cat behavior consulting company in Sacramento, Calif., who was not involved in the study. “So I was excited to see that researchers are taking on this topic.” Scientists have studied cats’ social relationships — both with other cats and humans — but it can be tricky to tell whether two cats are playing or fighting, says veterinarian and cat behavior researcher Noema Gajdoš-Kmecová of the University of Veterinary Medicine and Pharmacy in Košice, Slovakia (SN: 9/23/19).
Sometimes cat owners miss the signs of a tense relationship because they think their pets are just playing, which can lead to stress and illness in the animals, she says. Other times, owners rehome their cats after incorrectly assuming their pets are fighting.
To assess and categorize interactions, Gajdoš-Kmecová and colleagues watched about 100 videos of different cats interacting in pairs. After viewing around one-third of the videos, Gajdoš-Kmecová identified six types of behaviors, including wrestling and staying still. She then watched all of the videos and noted how often each cat exhibited one of the specified behaviors, and for how long. By running statistical analyses on the behaviors, she pinpointed three types of interactions between the cat pairs: playful, aggressive and intermediate.
To confirm the outcome, other members of the team also watched the videos and classified each interaction between felines.
Some clear connections emerged. Quietly wrestling, for instance, suggested playtime, whereas chasing and vocalizations, like growling, hissing or gurgling, implied aggressive encounters.
Intermediate interactions had elements of both playful and aggressive encounters, but especially included prolonged activity of one cat toward the other, such as pouncing on or grooming its fellow feline. These in-between encounters could hint that one cat wants to keep playing while the other doesn’t, with the more playful cat gently nudging to see if its partner wants to continue, the authors say. This work provides initial insights into cat interactions, Gajdoš-Kmecová says, but it’s just the start. In the future, she plans to study more subtle behaviors, like ear twitches and tail swishes. Both Gajdoš-Kmecová and Delgado also stress that one contentious encounter doesn’t necessarily signal a cat-astrophic relationship.
“This is not just about one interaction,” Gajdoš-Kmecová says. Owners “really should look into the different, multiple interactions in multiple periods of life of the cats and then put it into context.”
The night sky has been brightening faster than researchers realized, thanks to the use of artificial lights at night. A study of more than 50,000 observations of stars by citizen scientists reveals that the night sky grew about 10 percent brighter, on average, every year from 2011 to 2022.
In other words, a baby born in a region where roughly 250 stars were visible every night would see only 100 stars on their 18th birthday, researchers report in the Jan. 20 Science. The perils of light pollution go far beyond not being able to see as many stars. Too much brightness at night can harm people’s health, send migrating birds flying into buildings, disrupt food webs by drawing pollinating insects toward lights instead of plants and may even interrupt fireflies trying to have sex (SN: 8/2/17; SN: 8/12/15).
“In a way, this is a call to action,” says astronomer Connie Walker of the National Optical-Infrared Astronomy Research Laboratory in Tucson. “People should consider that this does have an impact on our lives. It’s not just astronomy. It impacts our health. It impacts other animals who cannot speak for themselves.”
Walker works with the Globe at Night campaign, which began in the mid-2000s as an outreach project to connect students in Arizona and Chile and now has thousands of participants worldwide. Contributors compare the stars they can see with maps of what stars would be visible at different levels of light pollution, and enter the results on an app.
“I’d been quite skeptical of Globe at Night” as a tool for precision research, admits physicist Christopher Kyba of the GFZ German Research Centre for Geosciences in Potsdam. But the power is in the sheer numbers: Kyba and colleagues analyzed 51,351 individual data points collected from 2011 to 2022.
“The individual data are not precise, but there’s a whole lot of them,” he says. “This Globe at Night project is not just a game; it’s really useful data. And the more people participate, the more powerful it gets.”
Those data, combined with a global atlas of sky luminance published in 2016, allowed the team to conclude that the night sky’s brightness increased by an average 9.6 percent per year from 2011 to 2022 (SN: 6/10/16).
Most of that increase was missed by satellites that collect brightness data across the globe. Those measurements saw just a 2 percent increase in brightness per year over the last decade. There are several reasons for that, Kyba says. Since the early 2010s, many outdoor lights have switched from high-pressure sodium lightbulbs to LEDs. LEDs are more energy efficient, which has environmental benefits and cost savings.
But LEDs also emit more short-wavelength blue light, which scatters off particles in the atmosphere more than sodium bulbs’ orange light, creating more sky glow. Existing satellites are not sensitive to blue wavelengths, so they underestimate the light pollution coming from LEDs. And satellites may miss light that shines toward the horizon, such as light emitted by a sign or from a window, rather than straight up or down.
Astronomer and light pollution researcher John Barentine was not surprised that satellites underestimated the problem. But “I was still surprised by how much of an underestimate it was,” he says. “This paper is confirming that we’ve been undercounting light pollution in the world.”
The good news is that no major technological breakthroughs are needed to help fix the problem. Scientists and policy makers just need to convince people to change how they use light at night — easier said than done.
“People sometimes say light pollution is the easiest pollution to solve, because you just have to turn a switch and it goes away,” Kyba says. “That’s true. But it’s ignoring the social problem — that this overall problem of light pollution is made by billions of individual decisions.”
Some simple solutions include dimming or turning off lights overnight, especially floodlighting or lights in empty parking lots.
Kyba shared a story about a church in Slovenia that switched from four 400-watt floodlights to a single 58-watt LED, shining behind a cutout of the church to focus the light on its facade. The result was a 96 percent reduction in energy use and much less wasted light , Kyba reported in the International Journal of Sustainable Lighting in 2018. The church was still lit up, but the grass, trees and sky around it remained dark.
“If it was possible to replicate that story over and over again throughout our society, it would suggest you could really drastically reduce the light in the sky, still have a lit environment and have better vision and consume a lot less energy,” he says. “This is kind of the dream.”
Barentine, who leads a private dark-sky consulting firm, thinks widespread awareness of the problem — and subsequent action — could be imminent. For comparison, he points to a highly publicized oil slick fire on the Cuyahoga River, outside of Cleveland, in 1969 that fueled the environmental movement of the 1960s and ’70s, and prompted the U.S. Congress to pass the Clean Water Act.
“I think we’re on the precipice, maybe, of having the river-on-fire moment for light pollution,” he says.
The Arctic today is a hostile place for most primates. But a series of fossils found since the 1970s suggest that wasn’t always the case.
Dozens of fossilized teeth and jaw bones unearthed in northern Canada belonged to two species of early primates — or at least close relatives of primates — that lived in the Arctic around 52 million years ago, researchers report January 25 in PLOS ONE. These remains are the first primate-like fossils ever discovered in the Arctic and tell of a groundhog-sized animal that may have skittered across trees in a swamp that once existed above the Arctic Circle. The Arctic was significantly warmer during that time. But creatures still had to adapt to extreme conditions such as long winter months without sunlight. These challenges make the presence of primate-like creatures in the Arctic “incredibly surprising,” says coauthor Chris Beard, a paleontologist at the University of Kansas in Lawrence. “No other primate or primate relative has ever been found this far north so far.”
Between frigid temperatures, limited plant growth and months of perpetual darkness, living in the modern Arctic isn’t easy. This is especially true for primates, which evolved from small, tree-dwelling creatures that largely fed on fruit (SN: 6/5/13). To this day, most primates — humans and few other outliers like Japan’s snow monkeys excepted — tend to stick to tropical and subtropical forests, largely found around the equator.
But these forests haven’t always been confined to their present location. During the early Eocene Epoch, which started around 56 million years ago, the planet underwent a period of intense warming that allowed forests and their warm-loving residents to expand northward (SN: 11/3/15).
Scientists know about this early Arctic climate in part because of decades of paleontological work on Ellesmere Island in northern Canada. These digs revealed that the area was once dominated by swamps not unlike those found in the southeastern United States today. This ancient, warm, wet Arctic environment was home to a wide array of heat-loving animals, including giant tapirs and crocodile relatives. For the new study, Beard and his colleagues examined dozens of teeth and jawbone fossils found in the area, concluding that they belong to two species, Ignacius mckennai and Ignacius dawsonae. These two species belonged to a now-extinct genus of small mammals that was widespread across North America during the Eocene. The Arctic variants probably made their way north as the planet warmed, taking advantage of the new habitat opening up near the poles.
Scientists have long debated whether this lineage can be considered true primates or whether they were simply close relatives. Regardless, it’s still “really weird and unexpected” to find primates or their relatives in the area, says Mary Silcox, a vertebrate paleontologist at the University of Toronto Scarborough.
For one thing, Ellesmere Island was already north of the Arctic Circle 52 million years ago. So while conditions may have been warmer and wetter, the swamp was plunged into continuous darkness during the winter months.
Newly arrived Ignacius would have had to adapt to these conditions. Unlike their southern kin, the Arctic Ignacius had unusually strong jaws and teeth suited to eating hard foods, the researchers found. This may have helped these early primates feed on nuts and seeds over the winter, when fruit wasn’t as readily available.
This research can shed light on how animals can adapt to live in extreme conditions. “Ellesmere Island is arguably the best deep time analog for a mild, ice-free Arctic,” says Jaelyn Eberle, a vertebrate paleontologist at the University of Colorado Boulder.
Studying how plants and animals adapted to this remarkable period in Arctic history, Beard says, could offer clues to the Arctic’s future residents.
A mucus-wicking robotic pill may offer a new way to deliver meds.
The multivitamin-sized device houses a motor and a cargo hold for drugs, including ones that are typically given via injections or intravenously, such as insulin and some antibiotics. If people could take such drugs orally, they could potentially avoid daily shots or a hospital stay, which would be “a huge game changer,” says MIT biomedical engineer Shriya Srinivasan.
But drugs that enter the body via the mouth face a tough journey. They encounter churning stomach acid, raging digestive enzymes and sticky slicks of mucus in the gut. Intestinal mucus “sort of acts like Jell-O,” Srinivasan says. The goo can trap drug particles, preventing them from entering the bloodstream.
The new device, dubbed RoboCap, whisks away this problem. The pill uses surface grooves, studs and torpedo-inspired fins to scrub away intestinal mucus like a miniature brush whirling inside a bottle. In experiments in pigs, RoboCap tunneled through mucus lining the walls of the small intestine, depositing insulin or the IV antibiotic vancomycin along the way, Srinivasan and colleagues report September 28 in Science Robotics. After churning for about 35 minutes, the pill continued its trip through the gut and eventually out of the body.
RoboCap is the latest pill-like gadget made to be swallowed. In 2019, some of the same researchers who developed RoboCap debuted a different device — one that injects drugs by pricking the inside of the stomach (SN: 2/7/19). That pea-sized injector was not designed to work in the small intestine, where some drugs are most easily absorbed. The RoboCap may also be able to deliver larger drug payloads, Srinivasan says.
Great scientists become immortalized in various ways.
Some through names for obscure units of measurement (à la Hertz, Faraday and Curie). Others in elements on the periodic table (Mendeleev, Seaborg, Bohr, among many others). A few become household names symbolizing genius — like Newton in centuries past and nowadays, Einstein. But only one has been honored on millions and millions of cartons of milk: the French chemist, biologist and evangelist for experimental science Louis Pasteur.
Pasteur was born 200 years ago this December, the most significant scientist birthday bicentennial since Charles Darwin’s in 2009. And Pasteur ranked behind only Darwin among the most exceptional biological scientists of the 19th century.
Pasteur not only made milk safe to drink, but also rescued the beer and wine industry. He established the germ theory of disease, saved the French silkworm population, confronted the scourges of anthrax and rabies, and transformed the curiosity of vaccination against smallpox into a general strategy for treating and preventing human diseases. He invented microbiology and established the foundations for immunology. Had he been alive after 1901, when Nobel Prizes were first awarded, he would have deserved one every year for a decade. No other single scientist demonstrated more dramatically the benefit of science for humankind.
He was not, however, exactly a saint. A Pasteur biographer, Hilaire Cuny, called him “a mass of contradictions.” Pasteur was ambitious and opportunistic, sometimes arrogant and narrow-minded, immodest, undiplomatic and uncompromising. In the scientific controversies he engaged in (and there were many), he was pugnacious and belligerent. He did not suffer criticism silently and was often acerbic in his responses. To his laboratory assistants, he was demanding, dictatorial and aloof. Despite his revolutionary spirit in pursuing science, in political and social matters, he was conformist and deferential to authority.
And yet he was a tireless worker, motivated by service to humankind, faithful to his family and unwaveringly honest. He was devoted to truth, and therefore also to science. In his youth, Pasteur did not especially excel as a student. His interests inclined toward art rather than science, and he did display exceptional skill at drawing and painting. But in light of career considerations (his father wanted him to be a scholar), Pasteur abandoned art for science and so applied to the prestigious École Normale Supérieure in Paris for advanced education. He finished 15th in the competitive entrance examination, good enough to secure admission. But not good enough for Pasteur. He spent another year on further studies emphasizing physical sciences and then took the École Normale exam again, finishing fourth. That was good enough, and he entered the school in 1843. There he earned his doctoral degree, in physics and chemistry, in 1847.
Among his special interests at the École Normale was crystallography. In particular he was drawn to investigate tartaric acid. It’s a chemical found in grapes responsible for tartar, a potassium compound that collects on the surfaces of wine vats. Scientists had recently discovered that tartaric acid possesses the intriguing power of twisting light — that is, rotating the orientation of light waves’ vibrations. In light that has been polarized (by passing it through certain crystals, filters or some sunglasses), the waves are all aligned in a single plane. Light passing through a tartaric acid solution along one plane emerges in a different plane.
Even more mysteriously, another acid (paratartaric acid, or racemic acid), with the exact same chemical composition as tartaric acid, did not twist light at all. Pasteur found that suspicious. He began a laborious study of the crystals of salts derived from the two acids. He discovered that racemic acid crystals could be sorted into two asymmetric mirror-image shapes, like pairs of right-handed and left-handed gloves. All the tartaric acid crystals, on the other hand, had shapes with identical asymmetry, analogous to gloves that were all right-handed. Pasteur deduced that the asymmetry in the crystals reflected the asymmetric arrangement of atoms in their constituent molecules. Tartaric acid twisted light because of the asymmetry of its molecules, while in racemic acid, the two opposite shapes canceled out each other’s twisting effects.
Pasteur built the rest of his career on this discovery. His research on tartaric acid and wine led eventually to profound realizations about the relationship between microbes and human disease. Before Pasteur, most experts asserted that fermentation was a natural nonbiological chemical process. Yeast, a necessary ingredient in the fermenting fluid, was supposedly a lifeless chemical acting as a catalyst. Pasteur’s experiments showed yeast to be alive, a peculiar kind of “small plant” (now known to be a fungus) that caused fermentation by biological activity.
Pasteur demonstrated that, in the absence of air, yeast acquired oxygen from sugar, converting the sugar to alcohol in the process. “Fermentation by yeast,” he wrote, is “the direct consequence of the processes of nutrition,” a property of a “minute cellular plant … performing its respiratory functions.” Or more succinctly, he proclaimed that “fermentation … is life without air.” (Later scientists found that yeast accomplished fermentation by emitting enzymes that catalyzed the reaction.)
Pasteur also noticed that additional microorganisms present during fermentation could be responsible for the process going awry, a problem threatening the viability of French winemaking and beer brewing. He solved that problem by developing a method of heating that eliminated the bad microorganisms while preserving the quality of the beverages. This method, called “pasteurization,” was later applied to milk, eliminating the threat of illness from drinking milk contaminated by virulent microorganisms. Pasteurization became standard public health practice in the 20th century.
Incorporating additional insights from studies of other forms of fermentation, Pasteur summarized his work on microbial life in a famous paper published in 1857. “This paper can truly be regarded as the beginning of scientific microbiology,” wrote the distinguished microbiologist René Dubos, who called it “one of the most important landmarks of biochemical and biological sciences.”
The germ theory of disease is born Pasteur’s investigations of the growth of microorganisms in fermentation collided with another prominent scientific issue: the possibility of spontaneous generation of life. Popular opinion even among many scientists held that microbial life self-generated under the proper conditions (spoiled meat, for example). Demonstrations by the 17th century Italian scientist Francesco Redi challenged that belief, but the case against spontaneous generation was not airtight. In the early 1860s Pasteur undertook a series of experiments that should have left no doubt that spontaneous generation, under conditions encountered on Earth today, was an illusion. Yet he was nevertheless accosted by critics, such as the French biologist Charles-Philippe Robin, to whom he returned verbal fire. “We trust that the day will come when M. Robin will … acknowledge that he has been in error on the subject of the doctrine of spontaneous generation, which he continues to affirm, without adducing any direct proofs in support of it,” Pasteur remarked.
It was his work on spontaneous generation that led Pasteur directly to the development of the germ theory of disease.
For centuries people had suspected that some diseases must be transmitted from person to person by close contact. But determining exactly how that happened seemed beyond the scope of scientific capabilities. Pasteur, having discerned the role of germs in fermentation, saw instantly that something similar to what made wine go bad might also harm human health.
After disproving spontaneous generation, he realized that there must exist “transmissible, contagious, infectious diseases of which the cause lies essentially and solely in the presence of microscopic organisms.” For some diseases, at least, it was necessary to abandon “the idea of … an infectious element suddenly originating in the bodies of men or animals.” Opinions to the contrary, he wrote, gave rise “to the gratuitous hypothesis of spontaneous generation” and were “fatal to medical progress.”
His first foray into applying the germ theory of disease came during the late 1860s in response to a decline in French silk production because of diseases afflicting silkworms. After success in tackling the silkworms’ maladies, he turned to anthrax, a terrible illness for cattle and humans alike. Many medical experts had long suspected that some form of bacteria caused anthrax, but it was Pasteur’s series of experiments that isolated the responsible microorganism, verifying the germ theory beyond doubt. (Similar work by Robert Koch in Germany around the same time provided further confirmation.)
Understanding anthrax’s cause led to the search for a way to prevent it. In this case, a fortuitous delay in Pasteur’s experiments with cholera in chickens produced a fortunate surprise. In the spring of 1879 he had planned to inject chickens with cholera bacteria he had cultured, but he didn’t get around to it until after his summer vacation. When he injected his chickens in the fall, they unexpectedly failed to get sick. So Pasteur prepared a fresh bacterial culture and brought in a new batch of chickens.
When both the new chickens and the previous batch were given the fresh bacteria, the new ones all died, while nearly all of the original chickens still remained healthy. And so, Pasteur realized, the original culture had weakened in potency over the summer and was unable to cause disease, while the new, obviously potent culture did not harm the chickens previously exposed to the weaker culture. “These animals have been vaccinated,” he declared.
Vaccination, of course, had been invented eight decades earlier, when British physician Edward Jenner protected people from smallpox by first exposing them to cowpox, a similar disease acquired from cows. (Vaccination comes from cowpox’s medical name, vaccinia, from vacca, Latin for cow.) Pasteur realized that the chickens surprisingly displayed a similar instance of vaccination because he was aware of Jenner’s discovery. “Chance favors the prepared mind,” Pasteur was famous for saying.
Because of his work on the germ theory of disease, Pasteur’s mind was prepared to grasp the key role of microbes in the prevention of smallpox, something Jenner could not have known. And Pasteur instantly saw that the specific idea of vaccination for smallpox could be generalized to other diseases. “Instead of depending on the chance finding of naturally occurring immunizing agents, as cowpox was for smallpox,” Dubos observed, “it should be possible to produce vaccines at will in the laboratory.”
Pasteur cultured the anthrax microbe and weakened it for tests in farm animals. Success in such tests not only affirmed the correctness of the germ theory of disease, but also allowed it to gain a foothold in devising new medical practices.
Later Pasteur confronted an even more difficult microscopic foe, the virus that causes rabies. He had begun intense experiments on rabies, a horrifying disease that’s almost always fatal, caused usually by the bites of rabid dogs or other animals. His experiments failed to find any bacterial cause for rabies, leading him to realize that it must be the result of some agent too small to see with his microscope. He could not grow cultures in lab dishes of what he could not see. So instead he decided to grow the disease-causing agent in living tissue — the spinal cords of rabbits. He used dried-out strips of spinal cord from infected rabbits to vaccinate other animals that then survived rabies injections.
Pasteur hesitated to test his rabies treatment on humans. Still, in 1885 when a mother brought to his lab a 9-year-old boy who had been badly bitten by a rabid dog, Pasteur agreed to administer the new vaccine. After a series of injections, the boy recovered fully. Soon more requests came for the rabies vaccine, and by early the next year over 300 rabies patients had received the vaccine and survived, with only one death among them.
Popularly hailed as a hero, Pasteur was also vilified by some hostile doctors, who considered him an uneducated interloper in medicine. Vaccine opponents complained that his vaccine was an untested method that might itself cause death. But of course, critics had also rejected Pasteur’s view of fermentation, the germ theory of disease and his disproof of spontaneous generation. Pasteur stood his ground and eventually prevailed (although he did not turn out to be right about everything). His attitude and legacy of accomplishments inspired 20th century scientists to develop vaccines for more than a dozen deadly diseases. Still more diseases succumbed to antibiotics, following the discovery of penicillin by Alexander Fleming — who declared, “Without Pasteur I would have been nothing.”
Even in Pasteur’s own lifetime, thanks to his defeat of rabies, his public reputation was that of a genius.
Pasteur’s scientific legacy As geniuses go, Pasteur was the opposite of Einstein. To get inspiration for his theories, Einstein imagined riding aside a light beam or daydreamed about falling off a ladder. Pasteur stuck to experiments. He typically initiated his experiments with a suspected result in mind, but he was scrupulous in verifying the conclusions he drew from them. Preconceived ideas, he said, can guide the experimenter’s interrogation of nature but must be abandoned in light of contrary evidence. “The greatest derangement of the mind,” he declared, “is to believe in something because one wishes it to be so.”
So even when Pasteur was sure his view was correct, he insisted on absolute proof, conducting many experiments over and over with variations designed to rule out all but the true interpretation.
“If Pasteur was a genius, it was not through ethereal subtlety of mind,” wrote Pasteur scholar Gerald Geison. Rather, he exhibited “clear-headedness, extraordinary experimental skill and tenacity — almost obstinacy — of purpose.” His tenacity, or obstinacy, helped him persevere through several personal tragedies, such as the deaths of three of his daughters, in 1859, 1865 and 1866. And then in 1868 he suffered a cerebral hemorrhage that left him paralyzed on his left side. But that did not slow his pace or impair continuing his investigations.
“Whatever the circumstances in which he had to work, he never submitted to them, but instead molded them to the demands of his imagination and his will,” Dubos wrote. “He was probably the most dedicated servant that science ever had.”
To the end of his life, Pasteur remained dedicated to science and the scientific method, stressing the importance of experimental science for the benefit of society. Laboratories are “sacred institutions,” he asserted. “Demand that they be multiplied and adorned; they are the temples of wealth and of the future.”
Three years before his death in 1895, Pasteur further extolled the value of science and asserted his optimism that the scientific spirit would prevail. In an address, delivered for him by his son, at a ceremony at the Sorbonne in Paris, he expressed his “invincible belief … that science and peace will triumph over ignorance and war, that nations will unite, not to destroy, but to build, and that the future will belong to those who will have done most for suffering humanity.” Two hundred years after his birth, ignorance and war remain perniciously prominent, as ineradicable as the microbes that continue to threaten public health, with the virus causing COVID-19 the latest conspicuous example. Vaccines, though, have substantially reduced the risks from COVID-19, extending the record of successful vaccines that have already tamed not only smallpox and rabies, but also polio, measles and a host of other once deadly maladies.
Yet even though vaccines have saved countless millions of lives, some politicians and so-called scientists who deny or ignore overwhelming evidence continue to condemn vaccines as more dangerous than the diseases they prevent. True, some vaccines can induce bad reactions, even fatal in a few cases out of millions of vaccinations. But shunning vaccines today, as advocated in artificially amplified social media outrage, is like refusing to eat because some people choke to death on sandwiches.
Today, Pasteur would be vilified just as he was in his own time, probably by some people who don’t even realize that they can safely drink milk because of him. Nobody knows exactly what Pasteur would say to these people now. But it’s certain that he would stand up for truth and science, and would be damn sure to tell everybody to get vaccinated.
