Several companies are testing brain implants – why is there so much attention swirling around Neuralink? Two professors unpack the ethical issues

Brain-computer interfaces have the potential to transform some people’s lives, but they raise a host of ethical issues, too. Andriy Onufriyenko/Moment via Getty Images

Nancy S. Jecker, University of Washington and Andrew Ko, University of Washington

Putting a computer inside someone’s brain used to feel like the edge of science fiction. Today, it’s a reality. Academic and commercial groups are testing “brain-computer interface” devices to enable people with disabilities to function more independently. Yet Elon Musk’s company, Neuralink, has put this technology front and center in debates about safety, ethics and neuroscience.

In January 2024, Musk announced that Neuralink implanted its first chip in a human subject’s brain. The Conversation reached out to two scholars at the University of Washington School of Medicine – Nancy Jecker, a bioethicst, and Andrew Ko, a neurosurgeon who implants brain chip devices – for their thoughts on the ethics of this new horizon in neuroscience.

How does a brain chip work?

Neuralink’s coin-size device, called N1, is designed to enable patients to carry out actions just by concentrating on them, without moving their bodies.

Subjects in the company’s PRIME study – short for Precise Robotically Implanted Brain-Computer Interface – undergo surgery to place the device in a part of the brain that controls movement. The chip records and processes the brain’s electrical activity, then transmits this data to an external device, such as a phone or computer.

The external device “decodes” the patient’s brain activity, learning to associate certain patterns with the patient’s goal: moving a computer cursor up a screen, for example. Over time, the software can recognize a pattern of neural firing that consistently occurs while the participant is imagining that task, and then execute the task for the person.

Neuralink’s current trial is focused on helping people with paralyzed limbs control computers or smartphones. Brain-computer interfaces, commonly called BCIs, can also be used to control devices such as wheelchairs.

A few companies are testing BCIs. What’s different about Neuralink?

Noninvasive devices positioned on the outside of a person’s head have been used in clinical trials for a long time, but they have not received approval from the Food and Drug Administration for commercial development.

A visitor experiences a BCI system during the 2023 China International Fair for Trade in Services in Beijing. Li Xin/Xinhua via Getty Images

There are other brain-computer devices, like Neuralink’s, that are fully implanted and wireless. However, the N1 implant combines more technologies in a single device: It can target individual neurons, record from thousands of sites in the brain and recharge its small battery wirelessly. These are important advances that could produce better outcomes.

Why is Neuralink drawing criticism?

Neuralink received FDA approval for human trials in May 2023. Musk announced the company’s first human trial on his social media platform, X – formerly Twitter – in January 2024.

Information about the implant, however, is scarce, aside from a brochure aimed at recruiting trial subjects. Neuralink did not register at ClinicalTrials.gov, as is customary, and required by some academic journals.

Some scientists are troubled by this lack of transparency. Sharing information about clinical trials is important because it helps other investigators learn about areas related to their research and can improve patient care. Academic journals can also be biased toward positive results, preventing researchers from learning from unsuccessful experiments.

Fellows at the Hastings Center, a bioethics think tank, have warned that Musk’s brand of “science by press release, while increasingly common, is not science.” They advise against relying on someone with a huge financial stake in a research outcome to function as the sole source of information.

When scientific research is funded by government agencies or philanthropic groups, its aim is to promote the public good. Neuralink, on the other hand, embodies a private equity model, which is becoming more common in science. Firms pooling funds from private investors to back science breakthroughs may strive to do good, but they also strive to maximize profits, which can conflict with patients’ best interests.

Neuralink’s first human implant was announced on Elon Musk’s social media platform X, formerly known as Twitter, in January 2024. NurPhoto via Getty Images

In 2022, the U.S. Department of Agriculture investigated animal cruelty at Neuralink, according to a Reuters report, after employees accused the company of rushing tests and botching procedures on test animals in a race for results. The agency’s inspection found no breaches, according to a letter from the USDA secretary to lawmakers, which Reuters reviewed. However, the secretary did note an “adverse surgical event” in 2019 that Neuralink had self-reported.

In a separate incident also reported by Reuters, the Department of Transportation fined Neuralink for violating rules about transporting hazardous materials, including a flammable liquid.

What other ethical issues does Neuralink’s trial raise?

When brain-computer interfaces are used to help patients who suffer from disabling conditions function more independently, such as by helping them communicate or move about, this can profoundly improve their quality of life. In particular, it helps people recover a sense of their own agency or autonomy – one of the key tenets of medical ethics.

However well-intentioned, medical interventions can produce unintended consequences. With BCIs, scientists and ethicists are particularly concerned about the potential for identity theft, password hacking and blackmail. Given how the devices access users’ thoughts, there is also the possibility that their autonomy could be manipulated by third parties.

The ethics of medicine requires physicians to help patients, while minimizing potential harm. In addition to errors and privacy risks, scientists worry about potential adverse effects of a completely implanted device like Neuralink, since device components are not easily replaced after implantation.

When considering any invasive medical intervention, patients, providers and developers seek a balance between risk and benefit. At current levels of safety and reliability, the benefit of a permanent implant would have to be large to justify the uncertain risks.

What’s next?

For now, Neuralink’s trials are focused on patients with paralysis. Musk has said his ultimate goal for BCIs, however, is to help humanity – including healthy people – “keep pace” with artificial intelligence.

This raises questions about another core tenet of medical ethics: justice. Some types of supercharged brain-computer synthesis could exacerbate social inequalities if only wealthy citizens have access to enhancements.

What is more immediately concerning, however, is the possibility that the device could be increasingly shown to be helpful for people with disabilities, but become unavailable due to loss of research funding. For patients whose access to a device is tied to a research study, the prospect of losing access after the study ends can be devastating. This raises thorny questions about whether it is ever ethical to provide early access to breakthrough medical interventions prior to their receiving full FDA approval.

Clear ethical and legal guidelines are needed to ensure the benefits that stem from scientific innovations like Neuralink’s brain chip are balanced against patient safety and societal good.

Nancy S. Jecker, Professor of Bioethics and Humanities, School of Medicine, University of Washington and Andrew Ko, Assistant Professor of Neurological Surgery, School of Medicine, University of Washington

This article is republished from The Conversation under a Creative Commons license. 

Top science stories of 2023

Twelve standout news events and trends in a tumultuous year

As 2023 rolls to a close, Knowable Magazine has looked back over its articles and canvassed editorial committee members from the 51 academic journals — covering analytical chemistry to vision science — published by Knowable’s parent company, Annual Reviews. From good news to bad, from novel vaccines to insect invaders, this year left us with much to ponder. Here we present 12 newsworthy developments from 2023.

Jabs for hope

Hot on the heels of the Covid-19 vaccine success story (including updated jabs that target Omicron subvariants of the rapidly shifting virus), 2023 saw the greenlighting of several new vital vaccines. Abrysvo and Arexvy, the first vaccines against respiratory syncytial virus (RSV), a cold-like virus that can be dangerous for the old or the young, are now available in the United States and elsewhere. And the World Health Organization has recommended a second malaria vaccine, R21, following RTS,S in 2021. RTS,S has already been given to nearly 2 million children in Africa; the new vaccine is about half the price.

This double hit against malaria is a “huge win” for kids, says Matthew Laurens, a pediatric infectious disease specialist at the University of Maryland School of Medicine in Baltimore, who wrote about malaria vaccines in a 2022 opinion article for Knowable. “Like Covid-19, we need multiple malaria vaccines if we’re to succeed in combating this deadly disease.”

Scary smarts

One of the biggest newsmakers of the year was artificial intelligence (AI). San Francisco tech company OpenAI’s conversational bot ChatGPT, first launched in November 2022, was estimated to have more than 100 million monthly users by January 2023. People were simultaneously impressed and appalled by the capacity of AI based on deep learning (a technique inspired by the human brain) to write everything from poetry to class essays and research papers. “In terms of public interest, I have not seen anything like this in my 30-year career,” says Colin Phillips, a psycholinguist at the University of Maryland and co-editor of the Annual Review of Linguistics.

Rapidly improving AI has left governments, scientists and consumers alike wondering how best to harness its abilities and guard against its misuse, including the deepfakes now featuring in scams and propaganda. International leaders agreed to work together to guide the technology at the UK’s AI Safety Summit in November — hoping to get regulations in place before computers grow smarter than people.

Wild weather

News reports of broken heat records are starting to sound like, well, broken records. But 2023 really was a standout: The planet had its hottest year on record. As of October, it was about 1.4 degrees Celsius warmer than the 1850–1900 average, topping the previous greatest above-average heat bumps of about 1.3 degrees C in both 2020 and 2016.

This extreme heat of 2023 resulted from both long-term climate change trends and the year’s El Niño, a natural climate pattern that, overall, tends to make the world warmer. This was the hottest summer since recordkeeping began in 1880, and September was by far the most weirdly warm month ever seen. These trends have been shown to play a role in much of 2023’s wild and destructive weather, from Canada’s wildfires to Libya’s floods. Researchers suspect that the planet will hit a long-term average of 1.5 degrees C warming — a commonly quoted target for maximum warming — sometime in the early 2030s.

Rapidly improving AI has left governments, scientists and consumers alike wondering how best to harness its abilities and guard against its misuse.

“Climate change is no longer about our grandchildren or polar bears — it is here, and now affecting everyone, everywhere on the planet, but especially devastating for the poor,” says Diana Ürge-Vorsatz, an environmental scientist and climate expert at Central European University and vice-chair of the Intergovernmental Panel on Climate Change. Ürge-Vorsatz co-penned an editorial calling for action against environmental crises in 2022’s volume of the Annual Review of Environment and Resources, for which she is a committee member.

Everything electric to end emissions

In December, delegates at the United Nations climate change convention discussed the first official inventory of our actions to combat global warming. The “global stocktake” concluded that while the world is making some progress and it will be possible to reach the Paris goal of limiting global warming to 2 degrees Celsius, leaders are going to have to accelerate action to get there.

For now, fossil fuel production remains too high for climate targets. But a Climate Analytics report says that there’s a 70 percent chance that greenhouse gas emissions will fall in 2024, making 2023 the “peak” year. Of course, getting away from fossil fuels means ramping up alternative energy sources. Renewables are soaring — particularly solar, and particularly in China. “Prices fell and penetration increased exceeding all projections,” says Ürge-Vorsatz of renewables. “In the first half of 2023, several countries have produced over three-quarters of their electricity from weather-dependent renewable forms of energy — still often deemed impossible by many experts.” At the December UN meeting, nations pledged to triple the planet’s renewable energy capacity by 2030.

New batteries in development will also help — 2023 saw a lab breakthrough in developing “lithium air” batteries. Meanwhile, researchers note some signs of hope that nuclear fusion might one day be feasible. The National Ignition Facility, an experimental laser-based fusion device at Lawrence Livermore National Laboratory in California, has produced slightly more energy than it used a total of four times since December 2022.

Fancy feast

As the world’s population grows, the quest continues for alternative high-protein foods that might mimic the sensory pleasures of meat without the attendant environmental problems from deforestation, greenhouse gas emissions and more. One option now on US plates is lab-grown meat, which was approved by regulators in June 2023, making the United States the second country to move “cellular meat” to market. Meanwhile, companies are also pursuing ever-better ways to make high-protein foods out of everything from insects to filamentous fungi to microbes that can convert air and hydrogen into edible food.

“Climate change is no longer about our grandchildren or polar bears — it is here, and now affecting everyone, everywhere on the planet, but especially devastating for the poor.”

— Diana Ürge-Vorsatz

It’s exciting to see lab-grown meat finally reach the market, says Julian McClements, a food scientist at the University of Massachusetts Amherst and editor of the Annual Review of Food Science and Technology, who has written about next-generation plant-based foods. Scaling up that tech, he says, “has potential to create a more healthy, sustainable and ethical food supply.” At the same time, many nutrition experts are raising the alarm about ultraprocessed foods, and foods packed with sugars, salts and fats to increase desirability. Another more sustainable and healthier option to the world’s current diet would be to just eat more plants.

Body maps

Efforts to better understand the human body in health and disease got a boost this year with several projects aiming to map out vital organs and improve diversity in medical datasets. “It’s really an exciting time,” says Sarah Teichmann, co-lead of the Human Cell Atlas initiative and a member of the Annual Review of Genomics and Human Genetics editorial committee.

In June, researchers unveiled a comprehensive atlas of the lung, compiled from studies of 2.4 million cells in 486 people and highlighting cellular features common in cancer and Covid-19. In October, the largest-yet brain atlas was released, including more than 3,000 cell types, some of them new to science. Researchers are also expanding efforts to sequence and study the genomes of ever more people on this planet, hoping to shift medical datasets away from a current, common bias toward men of European descent. In October, a plan was launched to create the largest-yet database of genomes from people of African ancestry. All these efforts “could help lead to global democratization of health care in the future,” says Teichmann.

Ocean waves

For the oceans in 2023, “it was the best of times, it was the worst of times,” says Nancy Knowlton, a marine biologist with the Smithsonian National Museum of Natural History in Washington, DC, who wrote about reasons to be optimistic about ocean health in the 2021 Annual Review of Marine Science. On one hand, beleaguered global oceans hit a record high temperature in April and in August (near the tail end of the summer season for the global south and north, respectively), with “seas as hot as a hot tub,” says Knowlton. On the other hand, she says, 2023 saw “major steps being taken to reverse the trajectory of ocean decline.”

“The CRISPR revolution is the fastest advance in biomedicine I have seen. ... This approval is just the first of many gene medicines to come.”

— Donald Kohn

That includes a High Seas Treaty, agreed upon in March after years of effort, to provide more oversight of international waters. The treaty carves out ways to share benefits from genetic resources dug from the deep, and to create marine protected areas far from any national shores. Meanwhile, progress was made on a separate treaty aimed at eliminating plastic pollution — including the single-use plastics that plague marine environments. That treaty, due in 2024, might cap plastic production, better regulate recycling and promote more sustainable, healthier materials — like bioplastics or novel uses of wood.

Insect invaders

The insects in the spotlight this year were bedbugs, which ravaged first Paris (during Fashion Week, no less) and then Asia. But buggy concerns go far beyond this; a raft of far more damaging pests are also on the move, devastating crops and forests around the world. In September, a report from the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) reported that alien invasives, including insects, are a major factor in 60 percent of species extinctions. But while pests are spreading and making pests of themselves, there’s a parallel problem of insect decline (sometimes called the “insect apocalypse”), though numbers are still scant to document the collapse among our planet’s 5.5 million species of insects.

“Insects are not optional; they are the little things that run the world and if they were to disappear, humans would last but a few months,” says University of Delaware entomologist Doug Tallamy (read his 2023 interview with Knowable). Researchers are investigating new angles for insect conservation, including using genomics to track and assist the creatures’ ability to adapt.

Transplant tech

Lab advances are promising hope for people in need of organ transplants. This year, medical researchers for the first time managed to transplant previously frozen organs: In a landmark study published in June, rats successfully received kidneys that had been cryogenically frozen for 100 days. Researchers also made great strides in exploring medical use of organs from animals: Last year, a 57-year-old man with terminal heart illness survived for two months after receiving a pig heart. In 2023, researchers reported that a monkey survived an amazing two years with a pig kidney, thanks in part to genetic modification.

“Organ transplantation is close to my heart, as some family members have been recipients of kidney transplants,” says Edgar Arriaga, a member of the Annual Review of Analytical Chemistry editorial committee who applies chemistry and engineering to biomedical challenges. The new developments “shine renewed optimism onto many people whose only hope for having a normal life is a functional organ.”

Reaching for stars

India became the fourth country to successfully put a lander on the Moon, to great fanfare. And NASA announced its intended crew for the next planned trip to the Moon (which will be in 2024 at the earliest). The four-person crew includes the first woman, the first person of color and the first non-American to head to the Moon.

Meanwhile, researchers looking far beyond the Moon to the stars now have a better tool in their toolkit: code that, finally, treats stars as the somewhat flattened, rotating, evolving balls that they are, rather than assuming they are perfect spheres. “At long last, this paper comes up with better models,” says Conny Aerts, an astrophysicist at KU Leuven in Belgium and a member of the Annual Review of Astronomy and Astrophysics editorial committee. “This is a remarkable achievement of major importance for astrophysics, because almost everyone in our field relies on stellar models.”

Fighting fat

The World Obesity Federation’s 2023 atlas predicts that more than half of the global population will be obese or overweight by 2035 — but new, effective drugs are emerging based on a better understanding of the hormones that control body weight. Many previous weight loss drugs targeted neurotransmitters such as norepinephrine to hit satiety and hunger centers in the brain. A new strategy instead targets the gut hormone GLP-1 (glucagon-like peptide 1), with a swath of benefits ranging from appetite suppression to blood sugar control.

New, effective drugs are emerging based on a better understanding of the hormones that control body weight.

The GLP-1-targeting drug Wegovy, approved in 2021, has proved wildly popular for weight loss, and this year a study showed that it could address heart problems in some patients, too. In November, a competitor, Zepbound, was also approved for weight loss in the United States. These developments are expected to lower the price on these expensive, injectable drugs. “This is truly an exciting and propitious time to be caring for individuals with the disease of obesity,” write endocrinologists Ania Jastreboff and Robert Kushner in an article tackling the subject in the Annual Review of Medicine.

Gene editing

In November, the UK medicines regulatory agency became the first in the world to approve a therapy that uses CRISPR gene editing — a revolutionary biotechnology that snips at DNA like a molecular scalpel. The United States followed suit in December. The treatment, called Casgevy, helps people with conditions caused by defective hemoglobin production or function, including sickle cell disease. The therapy is started by taking blood-producing cells out of the bone marrow of patients. The cells are genetically altered in the lab so that they produce fetal rather than adult hemoglobin, then infused back into the patient.

“The CRISPR revolution is the fastest advance in biomedicine I have seen,” says Donald Kohn, a medical geneticist at UCLA and coauthor of a recent overview of gene therapy in the Annual Review of Medicine. “This approval is just the first of many gene medicines to come.” CRISPR therapies are also being developed to tackle cancers, blindness, HIV, diabetes and more.

By Nicola Jones

What would signal life on another planet?

Astronomers have long debated what kind of chemistry might serve as a bona fide alien biosignature. With the launch of the James Webb Space Telescope, those ideas may be put to the test.

In June, astronomers reported a disappointing discovery: The James Webb Space Telescope failed to find a thick atmosphere around the rocky planet TRAPPIST-1 C, an exoplanet in one of the most tantalizing planetary systems in the search for alien life.

The finding follows similar news regarding neighboring planet TRAPPIST-1 B, another planet in the TRAPPIST-1 system. Its dim, red star hosts seven rocky worlds, a few of which are in the habitable zone — at a distance from their star at which liquid water could exist on their surfaces and otherworldly life might thrive.

What it would take to detect that life, if it exists, isn’t a new question. But thanks to the JWST, it’s finally becoming a practical one. In the next few years, the telescope could glimpse the atmospheres of several promising planets orbiting distant stars. Hidden away in the chemistry of those atmospheres may be the first hints of life beyond our solar system. This presents a sticky problem: What qualifies as a true chemical signature of life?

“You’re trying to take very little information about a planet and make a conclusion that is potentially quite profound — changing our view of the whole universe,” says planetary scientist Joshua Krissansen-Totton of the University of Washington.

To detect such a biosignature, scientists must find clever ways to work with the limited information they can glean by observing exoplanets.

Chemicals in context

Even the most powerful telescopes, including the JWST, almost never “see” exoplanets — by and large, astronomers know these distant worlds only by the flickering of their stars.

Instead of viewing planets directly, astronomers train their telescopes on stars and wait for planets to “transit,” or pass between, their sun and the telescope. As a planet transits, a bit of starlight filters through its atmosphere and dims the star at certain wavelengths, depending on the chemicals in the atmosphere. The resulting dips and peaks in the star’s brightness are like a chemical barcode for the transiting planet.

Perhaps the most intuitive way to look for a biosignature in that barcode is to scour it for a gas that was clearly produced by life. For a time scientists thought that oxygen, which is abundant on Earth because of photosynthesis, served as a stand-alone biosignature. But oxygen can arise from other processes: Sunlight could break apart water in the planet’s atmosphere, for example.

And that problem isn’t unique to oxygen — most of the gases that living things produce can also arise without life. So instead of treating single gases as biosignatures in their own right, scientists today tend to consider them in context.

Methane, for instance, can be produced both with and without life. It wouldn’t be a convincing biosignature on its own. But finding methane and oxygen together “would be hugely exciting,” says planetary scientist Robin Wordsworth of Harvard University; it’s very difficult to produce that combination without life. Likewise, work by Krissansen-Totton and colleagues recently showed that finding methane along with the right amounts of other gases, such as carbon dioxide, would be hard to explain without life.

Watching how an exoplanet atmosphere changes over time might also provide valuable context that could strengthen otherwise weak biosignatures. Seasonal variations in the concentration of ozone, for example, could be a fingerprint of life, scientists reported in 2018.

Surprises, not assumptions

Of course, “if you’re looking for individual gases like oxygen or methane, then built into that are assumptions about what type of life is elsewhere,” says Krissansen-Totton. So some scientists are developing agnostic biosignatures that don’t assume alien biochemistry will be anything like Earth’s biochemistry.

One possible agnostic biosignature is an exoplanet atmosphere’s degree of chemical “surprisingness” — what scientists call chemical disequilibrium.

An atmosphere close to equilibrium would be chemically uninteresting, a bit like a closed flask of gas in a laboratory. Of course, no planet is as boring as a lab flask. Chemical reactions in a planet’s atmosphere can be powered by their stars and geological processes like volcanic activity can increase disequilibrium, and thus increase the chemical surprisingness of the atmosphere.

Life can also push planets away from equilibrium. And assuming that alien life produces gases of some kind, they could push a planet’s atmosphere much further from equilibrium than it would be otherwise. Yet disequilibrium alone “is not an unambiguous indicator,” says Krissansen-Totton.

In 2016, he and his colleagues calculated the thermal disequilibrium of the atmosphere of every planet in the solar system and Saturn’s moon Titan. By this measure, the Earth’s atmosphere stood out as extreme — but only if the oceans were built into the calculations. Ignoring its interactions with the ocean, the Earth’s atmosphere is actually closer to equilibrium than the atmosphere of Mars.

Still, even if it might not point to biology, finding an exoplanet atmosphere far from equilibrium would tell astronomers that something interesting is happening, Krissansen-Totton says, something that’s “modifying the atmosphere in a dramatic way that we need to understand.”

David Kinney, a philosopher of science at Yale University, recently worked with biophysicist Chris Kempes of the Santa Fe Institute to develop a new way of detecting possible agnostic biosignatures. It’s a deceptively simple idea: To find life, look for the weirdest planets.

If no assumptions are made about what alien life is like, practically any gas could be a biosignature in the right context. In 2016, MIT astrophysicist Sara Seager and colleagues proposed a list of about 14,000 molecules for consideration as possible biosignatures. Kinney and Kempes developed their assessment method by using that list of compounds, along with methods inspired by machine learning algorithms designed to recognize the odd-image-out in a set. This led to a way to precisely define and score the “weirdness” of a hypothetical exoplanet’s atmosphere compared to a set of other hypothetical atmospheres.

Kinney and Kempes argue that the weirdest atmospheres in a set are the most likely to host life. This rests on a few basic assumptions: Life in the universe is rare, it leaves traces in planetary atmospheres, and it’s hard to mimic those traces without life. Of course, those assumptions might turn out to be false, Kinney says. But “if we want to make no assumptions at all,” he adds, “then I think it’s very hard to make any kind of scientific progress, let alone in the area with such severe uncertainty as this one.”

First, understand non-life

To reduce that uncertainty, scientists will need to be able to confidently rule out non-life explanations for any potential biosignature. That requires a thorough understanding of alien geology and atmospheric chemistry. So instead of focusing on whether a planet is habitable, some scientists argue that studying obviously lifeless planets will bolster the search for alien life.

“There are so many really basic things that I think we need to learn about the planets first before we can even begin to ask the question of habitability,” says Laura Kreidberg of the Max Planck Institute for Astronomy in Germany, coauthor with Wordsworth of an overview of rocky exoplanet astronomy in the 2022 Annual Review of Astronomy and Astrophysics.

One enormous question is whether the potentially rocky planets that JWST can observe will have atmospheres at all. The only stars whose habitable-zone planets are within the telescope’s reach are red dwarfs, like TRAPPIST-1. These stars have a nasty habit of spewing harsh radiation that many scientists think would inevitably strip away the atmospheres of any habitable planets, which might explain the scant or nonexistent atmospheres of TRAPPIST-1 B and TRAPPIST-1 C.

Red dwarf stars also happen to be the most common in the Milky Way — so if their rocky planets can’t hold on to atmospheres, it would substantially winnow down the number of potentially habitable worlds.

If we can observe enough rocky exoplanets, “we’re going to be in a much, much stronger place to understand what a biosignature means,” says Wordsworth. “One really powerful thing that exoplanets give us is statistics.”

The word “biosignature” may evoke a smoking gun. But, says Krissansen-Totton, “exoplanet life discovery is going to be a gradual accumulation of evidence.”

As that evidence continues to roll in, scientists can begin to test their hypotheses about rocky planets in a rigorous way, and perhaps reevaluate them.

“Astronomy is, at its heart, such a discovery science,” says Kreidberg. “For all of our best-laid plans and frameworks and systems, as soon as we start getting data and observing things, everything turns upside down.”

Elise Cutts is one of those ex-scientists who realized that writing about research is more fun than doing it. She’s based in Graz, Austria; find her @elisecutts.

Orbital resonance − the striking gravitational dance done by planets with aligning orbits

Planets can gravitationally affect each other when their orbits line up. NASA/JPL-Caltech

Chris Impey, University of Arizona

Planets orbit their parent stars while separated by enormous distances – in our solar system, planets are like grains of sand in a region the size of a football field. The time that planets take to orbit their suns have no specific relationship to each other.

But sometimes, their orbits display striking patterns. For example, astronomers studying six planets orbiting a star 100 light years away have just found that they orbit their star with an almost rhythmic beat, in perfect synchrony. Each pair of planets completes their orbits in times that are the ratios of whole numbers, allowing the planets to align and exert a gravitational push and pull on the other during their orbit.

This type of gravitational alignment is called orbital resonance, and it’s like a harmony between distant planets.

I’m an astronomer who studies and writes about cosmology. Researchers have discovered over 5,600 exoplanets in the past 30 years, and their extraordinary diversity continues to surprise astronomers.

Harmony of the spheres

Greek mathematician Pythagoras discovered the principles of musical harmony 2,500 years ago by analyzing the sounds of blacksmiths’ hammers and plucked strings.

He believed mathematics was at the heart of the natural world and proposed that the Sun, Moon and planets each emit unique hums based on their orbital properties. He thought this “music of the spheres” would be imperceptible to the human ear.

Four hundred years ago, Johannes Kepler picked up this idea. He proposed that musical intervals and harmonies described the motions of the six known planets at the time.

To Kepler, the solar system had two basses, Jupiter and Saturn; a tenor, Mars; two altos, Venus and Earth; and a soprano, Mercury. These roles reflected how long it took each planet to orbit the Sun, lower speeds for the outer planets and higher speeds for the inner planets.

He called the book he wrote on these mathematical relationships “The Harmony of the World.” While these ideas have some similarities to the concept of orbital resonance, planets don’t actually make sounds, since sound can’t travel through the vacuum of space.

Orbital resonance

Resonance happens when planets or moons have orbital periods that are ratios of whole numbers. The orbital period is the time taken for a planet to make one complete circuit of the star. So, for example, two planets orbiting a star would be in a 2:1 resonance when one planet takes twice as long as the other to orbit the star. Resonance is seen in only 5% of planetary systems.

Orbital resonance, as seen with Jupiter’s moons, happens when planetary bodies’ orbits line up – for example, Io orbits Jupiter four times in the time it takes Europa to orbit twice and Ganymede to orbit once. WolfmanSF/Wikimedia Commons

In the solar system, Neptune and Pluto are in a 3:2 resonance. There’s also a triple resonance, 4:2:1, among Jupiter’s three moons: Ganymede, Europa and Io. In the time it takes Ganymede to orbit Jupiter, Europa orbits twice and Io orbits four times. Resonances occur naturally, when planets happen to have orbital periods that are the ratio of whole numbers.

Musical intervals describe the relationship between two musical notes. In the musical analogy, important musical intervals based on ratios of frequencies are the fourth, 4:3, the fifth, 3:2, and the octave, 2:1. Anyone who plays the guitar or the piano might recognize these intervals.

Musical intervals can be used to create scales and harmony.

Orbital resonances can change how gravity influences two bodies, causing them to speed up, slow down, stabilize on their orbital path and sometimes have their orbits disrupted.

Think of pushing a child on a swing. A planet and a swing both have a natural frequency. Give the child a push that matches the swing motion and they’ll get a boost. They’ll also get a boost if you push them every other time they’re in that position, or every third time. But push them at random times, sometimes with the motion of the swing and sometimes against, and they get no boost.

Orbital resonance can cause planets or asteroids to speed up or start to wobble.

For planets, the boost can keep them continuing on their orbital paths, but it’s much more likely to disrupt their orbits.

Exoplanet resonance

Exoplanets, or planets outside the solar system, show striking examples of resonance, not just between two objects but also between resonant “chains” involving three or more objects.

---

Art & Science Collide series.

This article is part of Art & Science Collide, a series examining the intersections between art and science.

You may be interested in:

Literature inspired my medical career: Why the humanities are needed in health care

I wrote a play for children about integrating the arts into STEM fields – here’s what I learned about interdisciplinary thinking

Pictures have been teaching doctors medicine for centuries − a medical illustrator explains how

---

The star Gliese 876 has three planets with orbit period ratios of 4:2:1, just like Jupiter’s three moons. Kepler 223 has four planets with ratios of 8:6:4:3.

The red dwarf Kepler 80 has five planets with ratios of 9:6:4:3:2, and TOI 178 has six planets, of which five are in a resonant chain with ratios of 18:9:6:4:3.

TRAPPIST-1 is the record holder. It has seven Earth-like planets, two of which might be habitable, with orbit ratios of 24:15:9:6:4:3:2.

The newest example of a resonant chain is the HD 110067 system. It’s about 100 light years away and has six sub-Neptune planets, a common type of exoplanet, with orbit ratios of 54:36:24:16:12:9. The discovery is interesting because most resonance chains are unstable and disappear over time.

Despite these examples, resonant chains are rare, and only 1% of all planetary systems display them. Astronomers think that planets form in resonance, but small gravitational nudges from passing stars and wandering planets erase the resonance over time. With HD 110067, the resonant chain has survived for billions of years, offering a rare and pristine view of the system as it was when it formed.

Orbit sonification

Astronomers use a technique called sonification to translate complex visual data into sound. It gives people a different way to appreciate the beautiful images from the Hubble Space Telescope, and it has been applied to X-ray data and gravitational waves.

With exoplanets, sonification can convey the mathematical relationships of their orbits. Astronomers at the European Southern Observatory created what they call “music of the spheres” for the TOI 178 system by associating a sound on a pentatonic scale to each of the five planets.

Music from planetary orbits, created by astronomers at the European Southern Observatory.

A similar musical translation has been done for the TRAPPIST-1 system, with the orbital frequencies scaled up by a factor of 212 million to bring them into audible range.

Astronomers have also created a sonification for the HD 110067 system. People may not agree on whether these renditions sound like actual music, but it’s inspiring to see Pythagoras’ ideas realized after 2,500 years.

Chris Impey, University Distinguished Professor of Astronomy, University of Arizona

This article is republished from The Conversation under a Creative Commons license. 

Why interstellar objects like ‘Oumuamua and Borisov may hold clues to exoplanets

The detection of two celestial interlopers careening through our solar system has scientists eagerly anticipating more

By Theo Nicitopoulos

On October 17 and 18, 2017, an unusual object sped across the field of view of a large telescope perched near the summit of a volcano on the Hawaiian island of Maui. The Pan-STARRS1 telescope was designed to survey the sky for transient events, like asteroid or comet flybys. But this was different: The object was not gravitationally bound to the Sun, or to any other celestial body. It had arrived from somewhere else.

The mysterious object was the first visitor from interstellar space observed passing through the solar system. Astronomers named it 1I/‘Oumuamua, borrowing a Hawaiian word that roughly translates to “messenger from afar arriving first.” Two years later, in August 2019, amateur astronomer Gennadiy Borisov discovered the only other known interstellar interloper, now called 2I/Borisov, using a self-built telescope at the MARGO observatory in Nauchnij, Crimea.

While typical asteroids and comets in the solar system orbit the Sun, ‘Oumuamua and Borisov are celestial nomads, spending most of their time wandering interstellar space. The existence of such interlopers in the solar system had been hypothesized, but scientists expected them to be rare. “I never thought we would see one,” says astrophysicist Susanne Pfalzner of the Jülich Supercomputing Center in Germany. At least not in her lifetime.

With these two discoveries, scientists now suspect that interstellar interlopers are much more common. Right now, within the orbit of Neptune alone, there could be around 10,000 ‘Oumuamua-size interstellar objects, estimates planetary scientist David Jewitt of UCLA, coauthor of an overview of the current understanding of interstellar interlopers in the 2023 Annual Review of Astronomy and Astrophysics.

Researchers are busy trying to answer basic questions about these alien objects, including where they come from and how they end up wandering the galaxy. Interlopers could also provide a new way to probe features of distant planetary systems.

But first, astronomers need to find more of them.

“We’re a little behind at the moment,” Jewitt says. “But we expect to see more.”

Alien origins

At least since the beginning of the 18th century, astronomers have considered the possibility that interstellar objects exist. More recently, computer models have shown that the solar system sent its own population of smaller bodies into the voids of interstellar space long ago due to gravitational interactions with the giant planets.

Scientists expected most interlopers to be exocomets composed of icy materials. Borisov fit this profile: It had a tail made of gases and dust created by ices that evaporated during its close passage to the Sun. This suggests that it originated in the outer region of a planetary system where temperatures were cold enough for gases like carbon monoxide to have frozen into its rocks. At some point, something tossed Borisov, roughly a kilometer across, out of its system.

One potential culprit is a stellar flyby. The gravity of a passing star can eject smaller bodies, known as planetesimals, from the outer reaches of a system, according to a recent study led by Pfalzner. A giant planet could also eject an object from the outer regions of a planetary system if an asteroid or comet gets close enough for the planet’s gravitational tug to speed up the smaller body enough for it to escape its star’s hold. Close approaches can also happen when planets migrate across their planetary systems, as Neptune is thought to have done in the early solar system.

‘Oumuamua, on the other hand, is not what scientists expected. Observations suggest it is quite elongated — perhaps 240 meters long and as narrow as 40 meters. And unlike Borisov, it didn’t show any gas or dust activity, raising the possibility that it originated closer to its star where it was too warm for ices to form. If this was the case, a stellar flyby or giant planet probably would not have been able to pull the object out of its system. Instead, it may have been ejected during the death throes of its star: Pulses of gas from a dying star could push planets and planetesimals outward, destabilizing their orbits enough to send some of them flying into interstellar space.

It’s possible, however, that ‘Oumuamua did form in the cold outer reaches of its system and, as it neared the Sun, developed a gas tail that was not detected by telescopes. One clue is that the object sped up more than would be expected from the gravity of the solar system alone. A recent study suggests that such a boost could have come from small amounts of hydrogen outgassing that the telescopes didn’t detect. Several asteroids in our solar system may have gotten a similar boost from outgassing of water vapor, according to another study. Future observations by the James Webb Space Telescope, and by the JAXA Hayabusa2 Extended Mission (which will rendezvous with one of these solar system asteroids, known as “dark comets,” in 2031) may detect low levels of outgassing.

“We’ll have to wait and see, but they could be analogs of ‘Oumuamua,” says planetary scientist Darryl Seligman of Cornell University, coauthor with Jewitt of the review of interstellar interlopers.

Searching for nomads

More data, from more interlopers, may help resolve some of these questions. In order to gather these data, scientists will need better odds of detecting the objects when they pass through the solar system. “If Pan-STARRS1 didn’t observe where we did that particular night, it’s likely that ‘Oumuamua would never have been found,” says astronomer Robert Weryk, formerly of the University of Hawaii, who discovered the interloper in the telescope’s data.

The upcoming Legacy Survey of Space and Time at the Vera C. Rubin Observatory is expected to increase astronomers’ chances of finding these fast movers: Beginning as soon as 2025, the observatory’s telescope will image the entire visible southern sky every few nights, and its primary mirror has a diameter nearly seven meters larger than Pan-STARRS1, enabling it to see fainter objects, farther away. Once interlopers are detected, ground- and space-based telescopes will image them to try to determine what they are made of. And if a reachable target is discovered, the European Space Agency and the Japan Aerospace Exploration Agency’s Comet Interceptor, slated to launch in 2029, could be redirected to image the visitor up close.

Eventually, astronomers hope to build a catalog of interstellar objects similar to the inventory of exoplanets, which has grown to over 5,500 entries since the first discovery in 1992. That future inventory could help researchers answer the long-standing question of how typical Earth and the solar system are. The compositions of a large sample of interstellar objects could yield clues about the makeup of objects in exoplanetary systems — including ones that might support life.

“Planetesimals are the building blocks of exoplanets,” says astronomer Meredith Hughes of Wesleyan University in Middletown, Connecticut. This means they “can provide information about the diversity of environments, including ones that could be habitable.”

Now, ‘Oumuamua is beyond the orbit of Neptune, and comet Borisov is almost as far. They will continue their journey back into interstellar space, where it’s anyone’s guess what will happen next. Perhaps they will spend an eternity wandering the vast voids of space, or maybe they will be captured by a star. Or they could collapse into a disk of evolving gas and dust in a new planetary system and begin their journeys all over again.

Astronomers estimate there could be more interstellar objects in the Milky Way than stars in the observable universe. Finding more of them will offer a new way to probe the mysteries of the cosmos.

“The really cool thing,” Pfalzner says, “is that interstellar objects come to us.”

A newly identified ‘Hell chicken’ species suggests dinosaurs weren’t sliding toward extinction before the fateful asteroid hit

Birdlike dinosaur Eoneophron infernalis was about the size of an adult human. Zubin Erik Dutta

Kyle Atkins-Weltman, Oklahoma State University and Eric Snively, Oklahoma State University

Were dinosaurs already on their way out when an asteroid hit Earth 66 million years ago, ending the Cretaceous, the geologic period that started about 145 million years ago? It’s a question that has vexed paleontologists like us for more than 40 years.

In the late 1970s, debate began about whether dinosaurs were at their peak or in decline before their big extinction. Scientists at that time noted that while dinosaur diversity seemed to have increased in the geologic stage that spanned 83.6 million to 71.2 million years ago, the number of species on the scene seemed to decrease during the last few million years of the Cretaceous. Some researchers have interpreted this pattern to mean that the asteroid that struck the Gulf of Mexico was simply the final blow for an already vulnerable group of animals.

However, others have argued that what looks like a decrease in the diversity of dinosaurs may be an artifact of how hard it is to accurately count them. Fossil formations might preserve different dinosaurs more or less often based on factors like their favored environment and how easily their bodies fossilized there. The accessibility of various outcrops could influence what kinds of fossils researchers have so far found. These biases are a problem because fossils are what paleontologists must rely on to conclusively answer how healthy dinosaur populations were when the asteroid hit.

At that crucial moment, what was really happening to dinosaur diversity? Discovery, identification and description of new dinosaurs provide vital clues. This is where our work comes in. Close examination of what we’d thought was a juvenile specimen of an already known species of dinosaur from this time period revealed that it was actually part of an adult from a completely new species.

Our work focusing on the life stage of our specimen demonstrates that dinosaur diversity may not have been declining before the asteroid hit, but rather that there are more species from this time period yet to be discovered – potentially even through reclassification of fossils already in museum collections.

Kyle Atkins-Weltman holds the femur of the new dinosaur as it was received, with the other fossils in the background. Kyle Atkins-Weltman

Clues inside the bones of a birdlike dinosaur

Our new study focused on four hindlimb bones – a femur, a tibia and two metatarsals. They were unearthed in South Dakota, in rocks of the Hell Creek Formation, and date to the final 2 million years of the Cretaceous.

When we first examined the bones, we identified them as belonging to a family of dinosaurs known as the caenagnathids – a group of birdlike dinosaurs that had toothless beaks, long legs and short tails. Direct fossil and inferred evidence indicates these dinosaurs were covered in complex feathers, much like modern birds.

The only known species of caenagnathid from this time and region was Anzu, sometimes called the “chicken from Hell.” Covered in feathers and sporting wings and a toothless beak, Anzu was between roughly 450 and 750 pounds (200 and 340 kilograms). Despite its fearsome nickname, though, its diet is a matter of debate. It was likely an omnivore, eating both plant material and small animals.

Because our specimen was significantly smaller than Anzu, we simply assumed it was a juvenile. We chalked up the anatomical differences we noticed to its juvenile status and smaller size – and figured the animal would have changed had it continued to grow. Anzu specimens are rare, and no definite juveniles have been published in the scientific literature, so we were excited to potentially learn more about how it grew and changed throughout its lifetime by looking inside its bones.

Just like with a tree’s rings, bone records rings called lines of arrested growth. Each annual line represents part of a year when the animal’s growth slowed. They would tell us how old this animal was, and how fast or slow it was growing.

We cut through the middle of three of the bones so that we could microscopically examine the internal anatomy of the cross-sections. What we saw completely uprooted our initial assumptions.

Teal markers point to lines of arrested growth on the cross-section of fossilized bone. Toward the outside of the bone, the lines are much closer together, reflecting less growth per year. Researchers counted exactly six lines, meaning this animal was between 6 and 7 years old when it died. Holly Woodward

In a juvenile, we would expect lines of arrested growth in the bone to be widely spaced, indicating rapid growth, with even spacing between the lines from the inside to the outside surface of the bone. Here, we saw that the later lines were spaced progressively closer together, indicating that this animal’s growth had slowed and it was nearly at its adult size.

This was no juvenile. Instead, it was an adult of an entirely new species, which we dubbed Eoneophron infernalis. The name means “Pharaoh’s dawn chicken from Hell,” referencing the nickname of its larger cousin Anzu. Traits unique to this species include ankle bones fused to the tibia, and a well-developed ridge on one of its foot bones. These weren’t features a young Anzu would outgrow, but rather unique aspects of the smaller Eoneophron.

Expanding the caenagnathid family tree

With this new evidence, we started making thorough comparisons with other members of the family to determine where Eoneophron infernalis fit within the group.

It also inspired us to reexamine other bones previously believed to be Anzu, as we now knew that more caenagnathid dinosaurs lived in western North America during that time. One specimen, a partial foot bone smaller than our new specimen, appeared distinct from both Anzu and Eoneophron. Where once there was one “chicken from Hell,” now there were two, and evidence for a third: one large (Anzu), weighing as much as a grizzly bear, one medium (Eoneophron), humanlike in weight, and one small and yet unnamed, close in size to a German shepherd.

Eoneophron infernalis and the smaller unnamed species now join the larger Anzu as late-Cretaceous caenagnathid dinosaurs from the Hell Creek region. Zubin Erik Dutta

Comparing Hell Creek with older fossil formations such as the famous Dinosaur Park Formation of Alberta that preserves dinosaurs that lived between 76.5 million and 74.4 million years ago, we find not only the same number of caenagnathid species, but also the same size classes. There, we have Caenagnathus, comparable to Anzu, Chirostenotes, comparable to Eoneophron, and Citipes, comparable to the third species we found evidence for. These parallels in both species count and relative sizes offer compelling evidence that caenagnathids remained stable throughout the last part of the Cretaceous.

Our new discovery suggests that this dinosaur group was not declining in diversity at the very end of the Cretaceous. These fossils show that there are still new species to be discovered, and support the idea that at least part of the pattern of decreasing diversity is the result of sampling and preservation biases.

Did large dinosaurs go extinct the way a Hemingway character quipped he went broke: “gradually, then suddenly”? While there are plenty of questions still outstanding in this extinction debate, Eoneophron adds evidence that caenagnathids were doing quite well for themselves before the asteroid ruined everything.

This article has been updated to correct the full name in English of the new species.

Kyle Atkins-Weltman, Ph.D. Student in Paleoecology, Oklahoma State University and Eric Snively, Associate Professor of Anatomy and Cell Biology, Oklahoma State University

This article is republished from The Conversation under a Creative Commons license. 

What if every germ hit you at the exact same time? An immunologist explains

Your immune system encounters a legion of potential pathogens every day. Klaus Vedfelt/DigitalVision via Getty Images

Joseph Larkin III, University of Florida

Curious Kids is a series for children of all ages. If you have a question you’d like an expert to answer, send it to curiouskidsus@theconversation.com.

---

What would happen if all the diseases in the world hit us at the exact same time? – Gabriella, age 12, Irving, Texas

---

When I was younger, I would watch “Batman” on my black-and-white television after school. Usually, Batman would face either the Joker, the Penguin, the Puzzler, Catwoman or any one of his usual opponents. However, on some occasions, Batman would have to face them all at the same time.

What would happen if, like Batman, the immune system had to face all of its rivals at once?

I am an immunologist who teaches the fundamentals of immunology to college undergraduates. My research generally focuses on factors that regulate immune responses and prevent autoimmune diseases – conditions where the immune system attacks your own body. As a scientist studying how we build immunity against pathogens such as the virus that causes COVID-19, understanding how the immune system combats multiple threats at the same time is immensely important to me.

There’s no reason why you can’t come down with strep throat at the same time as when you have a cold. In fact, sometimes fighting off one enemy can leave a hole in your defenses that another opportunistic pathogen can take advantage of.

BAM! Understanding the rivals

The first point to consider is what your immune system protects you from. The potential bad guys include cancer cells and dangerous microorganisms – including bacteria, viruses, fungi and more – that cause infections. The immune system must also be careful not to damage healthy cells and beneficial microorganisms that live on and inside you.

You interact with thousands of microorganisms with every breath of air you take. Is the immune system facing off against all of them? Sort of.

T regulatory cells (red) determine whether an immune response should be mounted. NIAID/Flickr, CC BY

It takes a tremendous amount of energy to fight a battle once a rival gains a foothold within your blood or tissues, so your immune system works to prevent it from getting in the body in the first place. Your skin, snot, saliva and tears form a critical first line of defense. This is why burn victims who lose too much skin often die from overwhelming infection – their defensive barriers are too compromised and pathogens pour in.

The immune system greatly prefers catching a microbe in snot and blowing it out of your nose, or giving you time to wash it off the skin of your hands, over having to wage a cellular war. Gathering an army of immune cells to fight pathogens takes a lot of energy and makes you feel awful.

For example, the immune system increases your body temperature to make it an uncomfortable place for microorganisms to live and grow, but that fever can also make you want to lie down for days.

BOOM! Where are their weaknesses?

When Batman faced multiple opponents, he would find a weakness shared by all of the opponents and target it to foil their plans. The immune system uses the exact same strategy.

Certain microbes are considered pathogens largely because they are in the wrong place – such as inside your body instead of on your skin – and causing damage. Pathogens have specific parts on their surfaces called pathogen associated molecular patterns, or PAMPs.

Very importantly, your body doesn’t make PAMPS. This means if your immune system comes across a PAMP, it knows it isn’t supposed to be there and will mount an attack. Because the same PAMP is present on many different pathogens, a strategy to combat one PAMP can defeat many pathogens.

There are molecules in cells all over your body that can recognize PAMPS and destroy anything those PAMPS are on. It’s as though your immune system set up booby traps that can only attack your enemies.

Many of those booby traps are toll-like receptors. This family of molecules is located on the surface and inside of many of your cells. Once microbes contact these booby traps, they trigger an alarm that warn other cells of potential danger. In technical terms, this alarm is called inflammation.

SPLAT! Raising an army of defenders

Whereas Batman would need to think of a new strategy to combat the Joker, the Penguin and Catwoman, your immune system devised a plan long ago.

When the virus that causes COVID-19 emerged in 2019, it was something people’s immune systems likely had never seen before. However, some people already had immune cells that could target components of the virus. How is that possible?

The immune system makes many immune cells that are specific to antigens, or unique and recognizable parts of cancers and microorganisms, it hasn’t encountered before. This occurs through a process where pieces of your DNA randomly recombine to form unique immune cell receptors. The DNA in each of these immune cells is different from the DNA in any other cell in your body. Researchers believe that each person can generate at least a trillion different combinations of immune receptors, which is more than the number of pathogens an average person would ever face in their lifetime overall.

Your immune system can churn out billions of unique antibodies.

Although the immune system makes a lot of immune cells, most of them aren’t used because you’re not exposed to the antigen they’re made to recognize. However, when an immune cell recognizes an antigen, it rapidly makes many copies of itself. Since pathogens can also multiply rapidly, clonal selection allows you to rapidly raise an army to fight them.

Usually this strategy works well with one or two coinfections, such as if you have the common cold and an eye infection at the same time. But what if you were infected with a trillion pathogens at the same time? It would take a tremendous amount of energy and time to build an appropriate army against each microorganism all at once. Unfortunately, the immune system likely would be overwhelmed by this challenge, and you would probably die.

Fortunately, your immune system – like Batman – usually figures out the best way to shift a battle against rivals to its favor, pulling out a victory in the final minutes of the episode.

---

Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to CuriousKidsUS@theconversation.com. Please tell us your name, age and the city where you live.

And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.

Joseph Larkin III, Associate Professor of Microbiology and Cell Science, University of Florida

This article is republished from The Conversation under a Creative Commons license.