Many small animals grow their teeth, claws and other “tools" out of materials that are filled with zinc, bromine and manganese, reaching up to 20% of the material's weight.
My colleagues and I call these “heavy element biomaterials," and in a new paper, we suggest that these materials make it possible for animals to grow scalpel-sharp and precisely shaped tools that are resistant to breaking, deformation and wear.
We examined ant mandible teeth and found that they are a smooth mix of proteins and zinc, with single zinc atoms attached to about a quarter of the amino acid units that make up the proteins forming the teeth. In contrast, calcified tools – like human teeth – are made of relatively large chunks of calcium minerals. We think the lack of chunkiness in heavy element biomaterials makes them better than calcified materials at forming smooth, precisely shaped and extremely sharp tools.
To evaluate the advantages of heavy element biomaterials, we estimated the force, energy and muscle size required for cutting with tools made of different materials. Compared with other hard materials grown by these animals, the wear-resistant zinc material enables heavily used tools to puncture stiff substances using only one-fifth of the force. The estimated advantage is even greater relative to calcified materials that – since they can't be nearly as sharp as heavy element biomaterials - can require more than 100 times as much force.
Biomaterials that incorporate zinc (red) and manganese (orange) are located in the important cutting and piercing edges of ant mandibles, worm jaws and other 'tools.' (Robert Schofield, CC BY-ND)
Why it matters
It's not surprising that materials that could make sharp tools would evolve in small animals. A tick and a wolf both need to puncture the same elk skin, but the wolf has vastly stronger muscles. The tick can make up for its tiny muscles by using sharper tools that focus force onto smaller regions.
But, like a sharp pencil tip, sharper tool tips break more easily. The danger of fracture is made even worse by the tendency for small animals to extend their reach using long thin tools – like those pictured above. And a chipped claw or tooth may be fatal for a small animal that doesn't have the strength to cut with blunted tools.
From an evolutionary perspective, these materials allow smaller animals to consume tougher foods. And the energy saved by using less force during cutting can be important for any animal. These advantages may explain the widespread use of heavy element biomaterials in nature – most ants, many other insects, spiders and their relatives, marine worms, crustaceans and many other types of organisms use them.
What still isn't known
While my team's research has clarified the advantages of heavy element biomaterials, we still don't know exactly how zinc and manganese harden and protect the tools.
One possibility is that a small fraction of the zinc, for example, forms bridges between proteins, and these cross-links stiffen the material – like crossbeams stiffen a building. We also think that when a fang bangs into something hard, these zinc cross-links may break first, absorbing energy to keep the fang itself from chipping.
We speculate that the abundance of extra zinc is a ready supply for healing the material by quickly reestablishing the broken zinc-histidine cross-links between proteins.
What's next?
The potential that these materials are self-healing makes them even more interesting, and our team's next step is to test this hypothesis. Eventually we may find that self-healing or other features of heavy element biomaterials could lead to improved materials for things like small medical devices.
Despite being the only bridge early hominin species could have crossed to enter Eurasia, the Arabian Peninsula bears little to no evidence of early human occupation.
Subverting expectations, a recent excavation in the Nefud Desert found tools dated to different stages of hominin evolution.
It turns out that early humans moved in and out of the peninsula whenever the climate allowed them to do so.
We know a good deal about how early hominins †the branch of our evolutionary tree that split from chimps and bonobos up to seven million years ago †moved around their place of origin in eastern Africa. Fossils indicate they eventually made it to Eurasia through the Levant area of western Asia. This luscious green region, located on the easternmost edges of the Mediterranean, served our ancestors as the highway between two continents, one they would cross many times †in both directions.
Given how the Arabian Peninsula, a landmass that encapsulates the Levant, was our ancestors' one and only access point to the wider world, one would think evidence of their presence would stretch from Israel to Yemen. However, this is not the case. While the Levant is littered with prodigious digging sites, the paleontological and paleoenvironmental records of the peninsula's interior have remained hauntingly empty and fragmented.
That is, until today. According to a new paper published in Nature, excavations in the Nefud Desert in Saudi Arabia unearthed traces of both human and Neanderthal occupation. By shrinking their search window to wetter periods on the geologic time scale †what the authors refer to as "brief 'green' windows of reduced aridity approximately 400, 300, 200, 130-75 and 55 thousand years ago" †archaeologists were able to find a number of Low to Middle Pleistocene Age tools used by proto-humans that ventured into the region after heavy rainfall transformed the desert into a wide-open grassland.
Digging in the desert
To say the interior parts of the Arabian Peninsula have never yielded evidence of hominins would not be entirely true. The earth here hides evidence of hominins, just not of hominin settlements. Whenever archaeologists make a discovery, it is usually the remnants of a makeshift workshop site, which are very different from the cave and rock shelters that can be stumbled upon throughout the more hospitable Levant region. Did we look hard enough, though?
Excavations in northern Saudi Arabia at a site called Khall Amayshan 4 (KAM 4) suggest we did not. On the surface, the site looks like any other part of the Nefud Desert. Below ground, however, sedimentary rocks and interdunal basins tell of a time when this place used to contain a network of lakes and rivers. Such a clear and detailed preservation of this time in geologic history cannot be found anywhere else on the peninsula and was formed serendipitously when a sand dune slid atop the basin to protect it from erosion.
We know the shores at KAM 4 have been occupied by hominins several times during the Pleistocene because different phases of lake formation correspond with a "distinct lithic assemblage" †an archaeological term for stone tools and their byproducts, of which KAM 4 is filled to the brim. A 400,000-year-old assemblage contains small hand axes made from slabs of quartzite, while a 55,000-year-old deposit contains a number of Levallois flakes.
These tools can teach us several things about the hominins that made and used them. In terms of appearance and design, some assemblages at KAM 4 seem to have more in common with those found in Africa than those from the Levantine woodlands, suggesting a different migration out of Africa might have taken place †one that ended up in Arabia rather than Eurasia. "It seems," the researchers write, "that much of Northeast Africa and Southwest Asia shared similar material culture."
Climate change and migratory patterns
Hominin species did not hop continents at random; their migratory patterns were a response to the changing climate of the Pleistocene. Judging from the results of their excavation at KAM 4, researchers identified no less than five distinct movements into the Arabian Peninsula. Given that most of the tools were dated to periods that saw increased rainfall, it is safe to say our ancestors only migrated into the desert when it became hospitable enough for them to do so.
Conversely, researchers were unable to find any tools that would have been left during interglacial periods. It seems that, as the region became warmer and more arid, the hominin populations that had made their home inside the peninsula dispersed once again. The unstable environmental conditions that plagued the peninsula may well explain the fragmentation of its fossil evidence, a problem that researchers in the relatively static Levantine woodlands rarely encounter.
Because climate change and the accompanying mass migratory movements can actually erase the vast majority of a species' fossil record, these findings bear relevance to modern readers. This year's UN climate report warns of Arctic summers without ice and tropical storms that will become even more ubiquitous than they already are. What if hundreds of thousands of people have to leave their homes either temporarily or indefinitely?
Mass psychogenic illness, also known as mass hysteria, is when a group of people manifest physical symptoms from imagined threats.
History is littered with outbreaks of mass hysteria.
Recently, alleged cases of Tourette's syndrome appeared all over the world. Was it real or mass psychogenic illness?
While the term is often avoided for fear of ridiculing something more serious,mass psychogenic illness (MPI) †also known as mass sociogenic illness (MSI) or mass hysteria †is a real occurrence that can cause a variety of physical symptoms to manifest in groups of people despite the lack of any physical cause. Often compared toconversion disorder, in which emotional issues are "converted" into physical problems, MPI tends to occur among people who share anxieties, fears, and a sense of community. In the right group of people, it can spread like a virus.
A curious case of the condition related to TikTok videos shows both how imagined conditions can spread and how our modern media landscape presents new problems never even dreamt of in a time before the internet.
TikTok tics
In 2019, a strange slew ofnew Tourette's cases made its way into hospitals all over the world. Oddly, these were suddenly occurring in children well over the age of six, the age of typical onset. Most peculiar of all, many of the patients were exhibiting identical symptoms and tics. While many cases of Tourette's are similar, these symptoms were precisely the same.
As it turned out, the tics were also identical to those exhibited by one Jan Zimmermann, a 23-year-old YouTuber from Germany with Tourette's. On his channel,Gewitter im Kopf, he documents his daily life with the condition. All of the patients who suddenly claimed to have tics were fans of his or of similar channels on YouTube and TikTok.
There was nothing physically wrong with the large number of people who suddenly came down with Tourette's-like symptoms, and most of them recovered immediately after being told that they did not have Tourette's syndrome. Others recovered after brief psychologicalinterventions. The spread of the condition across a social group despite the lack of a physical cause all pointed toward an MPI event.
Historical cases of mass hysteria
Of course, humans do not need social media to develop symptoms of a disease that they do not have. Several strange cases of what appears to have been mass hysteria exist throughout history. While some argue for a physical cause in each case, the consensus is that the ultimate cause was psychological.
The dancing plagues of the Middle Ages, in which hundreds of people began to dance until they were utterly exhausted despite apparently wishing to stop, are thought to have been examples of mass madness. Some cases also involved screaming, laughing, having violent reactions to the color red, and lewd behavior. Attempts to calm the groups by providing musicians just made the problem worse, as people joined in to dance to the music. By the time the dancing plague of1518 ended, several people had died of exhaustion or injuries sustained during their dance marathon.
It was also common for nunneries to get outbreaks of what was then considered demonic possession but what now appears to be MPI. In many well recorded cases, young nuns †often cast into a life of poverty and severe discipline with little to say about it †suddenly found themselves "possessed" and began behaving in extremely un-nunlikefashion. These instances often spread to other members of the convent and required intervention by exorcists to resolve.
A more recent example might be the curious story of theMad Gasser of Mattoon. During WWII in the small town of Mattoon, Illinois, 33 people awoke in the middle of the night to a "sweet smell" in their homes followed by symptoms such as nausea, vomiting, and paralysis. Many claimed to see a figure outside their rooms fleeing the scene. Claims of gassings rapidly followed the initial cases, and the police department was swamped with reports that amounted to nothing. The cases ended after the sheriff threatened to arrest anyone submitting a report of being gassed without agreeing to a medicalreview.
Each of these cases exhibits the generally agreed upon conditions for MPI: the people involved were a cohesive group, they all agreed on the same threats existing, and they were enduring stressful and emotional conditions that later manifested as physical symptoms. Additionally, the symptoms appeared suddenly and spread by sight and communication among the affected individuals.
Social diseases for a social media age
One point upon which most sources on MPI agree is the tendency of the outbreaks to occur among cohesive groups whose members are in regular contact. This is easy to see in the above examples: nuns live together in small convents, medieval peasants did not travel much, and the residents of Mattoon were in a small community.
This makes the more recent case that relies on the internet all the more interesting. And it's not the only one. Another MPI centered around a school in New York in2011.
As a result, a team of German researchers has put forth the idea of a new version of MPI for the modern age: "mass social media-induced illness." It is similar to MPI but differs in that it is explicitly for cases driven by social media, in which people suffering from the same imagined symptoms never actually come into direct contact with one another.
Of course, these researchers are not the first to consider the problem in a digital context. Dr. Robert Bartholomew described the aforementioned New York case in a paper published in the Journal of the Royal Society of Medicine.
All this seems to imply that our online interactions can affect us in much the same ways as direct communication has for ages past and that the social groups we form online can be cohesive enough to cause identical symptoms in people who have never met. Therefore, we likely have not seen the last of "mass social media-induced illness."
Flying across the American Southwest, brilliant points of light shine in the distant wastes of the Mojave Desert. Three glowing spots hover over the horizon, each surrounded by a gleaming field. These are the towers and mirrors (heliostats) of the Ivanpah generating station, one of the largest concentrated solar power plants on Earth. What is this technology that allows solar power to continue at night, and how does it work?
Traditional photovoltaic (PV) solar cells absorb sunlight and pour out electricity. Particles of light (photons) emitted by the sun travel through space, transit Earth's atmosphere, and smack into a solar panel. Some photons are reflected away by the panel and lost. Most of them are absorbed by the atoms of the panel, which then release electrons. The solar cell's electrical design gathers these electrons and channels them out as electrical current. Further electrical devices convert this low voltage direct current (DC) to higher voltage alternating current (AC) to send across power transmission lines.
Concentrated solar thermal (CST) power plants do not directly exchange solar photons for electrons. They gather the photons and use them to heat water, which turns a steam turbine, which turns an electrical generator. This is the same way that nuclear fission and fossil fuel plants generate electricity †the difference being that uranium or coal or natural gas are replaced by the heat of the sun's rays.
The solar concentrator's basic design is simple. An array of heliostats †a term for mirrors on swiveling mounts capable of tracking the sun †is built on the ground. These arrays cover many hundreds of acres, roughly comparable to a large traditional solar plant of similar capacity. Each mirror is continuously adjusted so that it points in a direction that bisects the angle between the sun and a giant power tower. Sunlight is thus beamed up toward a boiler system looming 400-800 feet above the earth.
Approaching the central tower, the converging solar light from thousands of mirrors becomes extremely powerful. Visible from many miles away, the nearly transparent air itself will shine with scattered optical power. Unlucky birds that intersect the concentrated beams are incinerated mid-air. This dense power is what ultimately drives electrical generation.
The top of the tower is a box with black walls †the sides of a boiler designed to absorb nearly all of the reflected light, which contains the fluid to be heated. Some plants, like Ivanpah in California, heat water for their steam turbines. Others use a more exotic molten salt working fluid.
Solar thermal concentration offers one major advantage over traditional PV solar cell technology: dispatchability. A properly configured CST plant can broil molten salt to more than 1000 degrees Fahrenheit, storing an incredible amount of heat energy. The liquid salt is then pumped into a holding tank, acting as a sort of battery. When sunlight is not available (roughly half the time), this stored up sunlight energy can be pumped out of the tank and used to power a turbine generator for on-demand power overnight.
Installed CST electricity generation across the globe is relatively low. While the technology works today, and paths to advance it have been laid out, the cost is currently too high to compete with standard photovoltaic cells. Many nations, including Israel, the United Arab Emirates, Morocco, China, Chile, Spain, and India have built giant power tower installations, yet most of their future commitments are unclear. While concentrated solar thermal power has been growing cheaper, PV cell cost has been dropping just as rapidly.
The future of this energy source may well hinge on continued development of its stored energy capability for dispatchable power, which is needed to fill in for inconsistent wind turbines and PV solar plants.
Options today to store energy are very limited. Lithium-ion technology has many downsides that prevent countries from running on batteries. Like the cells in a laptop, they are expensive, they degrade dramatically over time, and they are liable to catch fire. Global production capacity is far too small for the task, and that production is dominated by China.
Concentrated solar thermal technology is straightforward and clean. The design is beautiful and still being improved. Effectively storing sunlight for overnight power dispatch is a brilliant feature. Still, commercial grid electricity is a brutal market in which the cheapest wins. Will solar concentrator plants become competitive and multiply around the world? We shall see.
By studying the characteristics of stars, like their temperature and luminosity, astrophysicists figured out how stars evolve over time.
This amazing insight is the primary lesson of the Hertzsprung-Russell (HR) diagram.
Human beings, as the species Homo sapiens, have been around for about 300,000 years. That turns out to be about 100 million nights during which somebody, somewhere looked up at the dark sky and asked, "What are those twinkly lights?"
Given all those nights and all those people asking pretty much the same question, it is pretty remarkable that we happen to live in one of the first generations that actually knows the answer. Here in the 21st century, we know for sure what stars are, and a key reason we have that knowledge is because of a little something called the HR diagram. Over the summer, I wrote two other posts on what I called the "most important graph in astrophysics." Today, I want to finish the series by explaining how the HR diagram shows us how stars age and evolve.
Stellar evolution: a star's life cycle
You can read the first and second posts here and here, respectively. But for completeness, let's restate that the HR diagram is a plot with stellar luminosity (L for energy output) on the vertical axis and stellar surface temperature (T for temperature) on the horizonal axis. In the previous posts, we learned that when you measure L and T for a bunch of stars and then drop them onto this kind of plot, you find the majority of the points fall on a thick diagonal band running from high stellar luminosity and temperature (high L and T) to low stellar luminosity and temperature (low L and T). That band is what astronomers call the Main Sequence, and its discovery in the HR diagram was key to understanding what stars were and how they shined.
What the Main Sequence revealed were stars in their long middle age. Middle-aged stars (meaning stars in between their relatively short birth and death phases) support themselves against their own crushing, titanic gravity by releasing energy through fusion reactions in their hot, dense cores. Hydrogen nuclei are fused into helium nuclei, giving up a little energy along the way through good ol' E = mc2.
As long as there is hydrogen to burn in the core, a star is stable, happy, and free to shine its brilliance into the dark night of space. Luckily stars have lots of hydrogen to burn. A star like the sun contains about a billion billion billion tons of hydrogen gas. That translates into about 10 billion years of life on the Main Sequence. But a billion billion billion tons of gas is not infinite. Eventually, the hydrogen fusion party must end. The star will run out of fuel in the core, and that is when it stops being middle-aged.
What happens next is also revealed by the HR diagram, which once again, is why it is the most important graph in astrophysics. When astronomers first started dropping their stars onto the diagram more than 100 years ago, they saw not only the Main Sequence but also stars clustered in other places. There were lots of moderately bright stars with low temperatures (high L and low T). There were also lots of really, really bright stars with even lower temperatures (very high L and lower T). Using the laws of physics associated with hot glowing matter, astronomers could derive the sizes of these bright cool stars and found that they were much bigger than the sun. They identified giant stars (the bright ones), which were 10 times the size of the sun, and supergiants (the really, really bright ones), which were 100 times the size of the sun.
These various kinds of giant stars on the HR diagram were the all-important evidence for the evolution of stars. Stellar properties were not static. They aged and changed just like we did. Astrophysicists eventually saw that the evolution of a star on the HR diagram was driven by the evolution of nuclear burning in its core. As researchers got better at modeling what happens within stars as they age, they came to see that after the hydrogen fuel runs out in the core, gravity begins to crush what is left: inert helium "ash."
Eventually, the gravitational squeeze drives temperatures and densities in the core high enough to ignite the helium ash, allowing the helium nuclei to fuse into carbon nuclei. These internal changes rearrange the outer layers of the star, making them swell and bloat †first into the giants, and then into the supergiants. The details of why they get so large are complicated and require lots of detailed calculations (done with computers). What matters for us is that what comes out of those calculations are evolutionary tracks across the HR diagram. The tracks are predictions, telling astronomers how changes in a star's nuclear burning history will manifest in it its luminosity and temperature which, in turn, translates into how it will move across the HR diagram over time.
The changes for actual stars are too slow to watch over a human lifetime. But by taking measurements of lots of random stars (meaning they are at random points in their evolution), we can find the older ones in their giant or supergiant phases. Then, via some statistics, astronomers can then see if their theoretical evolutionary tracks match what they see in the HR diagram. The answer is a resounding yes.
So not only do we know what stars are (big balls of mostly hydrogen gas with a fusion furnace in the core), but we also know exactly how those luminous spheres evolve across billions of years of cosmic history †including lighting up the nights for a remarkable planet that is home to some remarkable hairless monkeys.
Before migrating to the sea, whales were terrestrial herbivores.
As they transitioned to the ocean and became carnivores, at least one proto-whale was an eating machine †both on land and in the sea.
This fearsome fossil was found in the Sahara desert, which used to be an ocean bottom.
Whales are carnivorous, although gigantic baleen whales feed on such tiny prey that it is hard to believe that they ever get enough food. Toothed whales dine on fish, squid, and octopi. (Fun fact: Orcas, also known as killer whales, are not really whales †they are gigantic, killer dolphins.)
Before moving into the sea, it is believed that whales were once terrestrial herbivores and somewhat deer-like. About 43 million years ago, say the authors of a new study, at least oneprotocetid †a semi-aquatic whale †was something else entirely. According to a fossil recently found in the Sahara desert, it was a four-legged, walking, swimming, Jurassic World-like nightmare.
In more gentle, scientific terms: "Unique features of the skull and mandible suggest a capacity for more efficient oral mechanical processing than the typical protocetid condition, thereby allowing for a strong raptorial feeding style."
Likely feeding on both land and in the sea, Phiomicetus anubis was fierce, with teeth and jaws powerful enough to tear apart its prey. The study says that it was about 10 feet long and weighed as much as 1,300 pounds, with a head reminiscent of a jackal's. Thus, its discoverers had good reason to name it after Anubis, the Egyptian god of death.
The Sahara was not always a desert
Authors Mohamed Sameh, Abdullah Gohar, and Hesham Sallam with the Phiomicetus anubis fossil.Credit: Abdullah Gohar (courtesy of the authors)
P. anubis was found in the Sahara desert, which was once under water. It is believed that such Protocetidae hail from the Eocene era in the Indo-Pakistan region. Its fossil was found in the Fayum Depression in the Egyptian Western Desert, an area that has been the site of numerous prehistoric whale discoveries, as well as discoveries of early fish, sharks, and land mammals.
The researchers did not find all of P. anubis, but they did find enough to deduce its characteristics based on its cranium, jaws, cervical and thoracic vertebrae, and its rib fragments.
Chow time
Examination of the whale's teeth suggests that it routinely digested prey that were too large to swallow whole and thus had to be torn apart. Among its likely fare: large fish, smaller cetaceans, turtles, and invertebrates such as nautiloids. As far as how it caught and killed its food, the study says:
"Phiomicetus may have used the same mechanism that modern crocodilians and sharks use in hunting large prey items (e.g. large fish or small cetaceans) by pulling them onto land or tearing them by seizing a part of the prey with powerful jaws then rolling and twisting the entire body."
The researchers also assert that P. anubis was not above scavenging.
Conventionalism is the idea that right and wrong depend entirely on the cultures and traditions to which we belong. What one culture calls immoral, another accepts as normal.
But if we accept this reasoning, we are forced to conclude that any manner of atrocities †from ritual child sacrifice to female genital mutilation †are permissible.
Without a universal standard of morality, it is difficult to claim that some behaviors are always wrong.
On August 17, 2021, the Taliban, fresh from their takeover of Afghanistan, released a statement that they would protect the existing rights of Afghan women "within the framework of Islam." There was no mention of "human rights" or the Western idea of equality. Instead, the Taliban were appealing to a 2500-year-old tradition †the idea of cultural relativity.
The belief that right and wrong and good and bad depend on the culture to which one belongs is popular today. We are loath to say that one culture is better or worse than another, that one way of doing things is "immoral," or that some traditions are a bit disgusting or weird. Doing so risks being labeled culturally insensitive †or worse. But what do we lose by being willfully blind to vast differences in moral standards between cultures?
You say potato, I say ritual child sacrifice
From where do you get your morals? Your sense of right and wrong? If you are an absolutist, it will presumably come from some kind of universal (possibly religious) moral order. But if you are a relativist, you likely will point to some worldly source, like society, family, or personal conscience.
Broadly speaking, there are two kinds of relativists: subjectivists and conventionalists.
Subjectivists are those who believe values and morals are made entirely by you as an individual. It finds expression in French philosopher Jean-Paul Sartre, who wrote, "You are free, therefore choose †that is to say, invent. No rule of general morality can show you what you ought to do."
But it is found also in Frederick Nietzsche's "perspectivism," which allows for no facts at all †not least moral facts †but only interpretations from our particular vantage point. When he wrote that "every great philosophy up till now has consisted of… the confession of its originator, and a species of involuntary and unconscious autobiography," he meant to say that whenever we declare this or that to be the case, we are only expressing or projecting our own values.
So, subjectivists will argue that you have your values, and I have mine. I am a vegetarian, and you are a meat eater. You are happy to download movies illegally, and I am not. And that is okay.
Conventionalists, on the other hand, argue that our morals come from the society, culture, or historical norms of our time. They see right and wrong as embedded in the traditions and conventions of our age. And the first clear formulation of this is found in Herodotus.
It's all Greek to me
Any well traveled person can attest that the more you see of the varied and incongruous behaviors across the world, the more you see your own afresh. But in spite of all these different cultures, we have an incredibly hard time abandoning our own.
As Herodotus wrote in Histories †a sprawling, entertaining, and often hilariously inaccurate account of the peoples and times of the 5th century BCE †if someone were asked "out of all the customs in the world" which they thought were the best, they would almost always "end by preferring their own. So convinced are they that their own usages far surpass those of all others."
As wild and exciting as a new land might be, we still come back home and tell our friends how strange and weird it was.
To flesh out his point, Herodotus tells a story involving the Persian emperor, Darius. Darius asked his Greek captives if they would accept payment to eat their dead father's body. The Greeks said they would never, ever do so. The proper funeral rites of Greece demanded corpses to be burned. Darius then sent for his Indian captives, a group of people called the "Callatians", who he knew did eat their father's body after death. Would they accept any money to burn their father's bodies? They were shocked and offended. It was an utter sacrilege, and they refused any money.
His point? What one people thinks is the height of taboo, another will see as normal. We each have the morals that we do simply because we were born in a particular time and place.
Can we declare that another culture is immoral?
The problem with conventionalism, or cultural relativity, is that it is hard to see how we can ever judge another culture's questionable practices. If we truly believe that "right and wrong are wholly defined by society," then we are forced to admit that any manner of atrocities †from ritual child sacrifice to the Holocaust †are okay.
If a country has a long and popular tradition of female genital mutilation, then we have no grounds to say that it is wrong. If a culture accepts child marriages or a pre-adolescent age of consent, that is just the way they do things. And, with our opening example, if the Taliban or Afghan Muslim tradition subjugates women and forbids free speech, what grounds do we have to rebuke them?
It seems that there are few ways out of this problem. One way might be to commit to what is called "political realism," which dates back to another "father of history" in the ancient Greek, Thucydides. This theory maintains that right and wrong, or the idealistic notions of justice and honor, simply do not apply in international relations. When we are dealing with states against states, it is dog-eat-dog or "might makes right" †a form of ethical survival of the fittest, perhaps.
But this is unsatisfactory. If we are to salvage the idea that certain beliefs or practices are morally wrong, reprehensible even, no matter where or when they occur, we likely have to revert to some kind of moral absolutism. This is no easy position to argue, since to do so seems to require some universal or objective ethical yardstick by which to bash others. We need a reply when someone asks, "On what grounds is your way better?" One way, of course, is religion. But if not religion, then what?
It is a thorny issue, but what the Taliban's wily and manipulative press conference has revealed is that there is a paucity to moral relativism that most find hard to accept. Perhaps Afghanistan has taught us that we are more absolutist than we thought.
However, it's still relatively expensive to store energy. And since renewable energy generation isn't available all the time – it happens when the wind blows or the sun shines – storage is essential.
Here are three emerging technologies that could help make this happen.
Longer charges
From alkaline batteries for small electronics to lithium-ion batteries for cars and laptops, most people already use batteries in many aspects of their daily lives. But there is still lots of room for growth.
For example, high-capacity batteries with long discharge times – up to 10 hours – could be valuable for storing solar power at night or increasing the range of electric vehicles. Right now there are very few such batteries in use. However, according to recent projections, upwards of 100 gigawatts' worth of these batteries will likely be installed by 2050. For comparison, that's 50 times the generating capacity of Hoover Dam. This could have a major impact on the viability of renewable energy.
Batteries work by creating a chemical reaction that produces a flow of electrical current.
One of the biggest obstacles is limited supplies of lithium and cobalt, which currently are essential for making lightweight, powerful batteries. According to some estimates, around 10% of the world's lithium and nearly all of the world's cobalt reserves will be depleted by 2050.
Furthermore, nearly 70% of the world's cobalt is mined in the Congo, under conditions that have long been documented as inhumane.
Scientists are working to develop techniques for recycling lithium and cobalt batteries, and to design batteries based on other materials. Tesla plans to produce cobalt-free batteries within the next few years. Others aim to replace lithium with sodium, which has properties very similar to lithium's but is much more abundant.
Safer batteries
Another priority is to make batteries safer. One area for improvement is electrolytes – the medium, often liquid, that allows an electric charge to flow from the battery's anode, or negative terminal, to the cathode, or positive terminal.
When a battery is in use, charged particles in the electrolyte move around to balance out the charge of the electricity flowing out of the battery. Electrolytes often contain flammable materials. If they leak, the battery can overheat and catch fire or melt.
Scientists are developing solid electrolytes, which would make batteries more robust. It is much harder for particles to move around through solids than through liquids, but encouraging lab-scale results suggest that these batteries could be ready for use in electric vehicles in the coming years, with target dates for commercialization as early as 2026.
While solid-state batteries would be well suited for consumer electronics and electric vehicles, for large-scale energy storage, scientists are pursuing all-liquid designs called flow batteries.
A typical flow battery consists of two tanks of liquids that are pumped past a membrane held between two electrodes. ( Qi and Koenig, 2017, CC BY)
In these devices both the electrolyte and the electrodes are liquids. This allows for super-fast charging and makes it easy to make really big batteries. Currently these systems are very expensive, but research continues to bring down the price.
Storing sunlight as heat
Other renewable energy storage solutions cost less than batteries in some cases. For example, concentrated solar power plants use mirrors to concentrate sunlight, which heats up hundreds or thousands of tons of salt until it melts. This molten salt then is used to drive an electric generator, much as coal or nuclear power is used to heat steam and drive a generator in traditional plants.
These heated materials can also be stored to produce electricity when it is cloudy, or even at night. This approach allows concentrated solar power to work around the clock.
This idea could be adapted for use with nonsolar power generation technologies. For example, electricity made with wind power could be used to heat salt for use later when it isn't windy.
Concentrating solar power is still relatively expensive. To compete with other forms of energy generation and storage, it needs to become more efficient. One way to achieve this is to increase the temperature the salt is heated to, enabling more efficient electricity production. Unfortunately, the salts currently in use aren't stable at high temperatures. Researchers are working to develop new salts or other materials that can withstand temperatures as high as 1,300 degrees Fahrenheit (705 C).
One leading idea for how to reach higher temperature involves heating up sand instead of salt, which can withstand the higher temperature. The sand would then be moved with conveyor belts from the heating point to storage. The Department of Energy recently announced funding for a pilot concentrated solar power plant based on this concept.
Advanced renewable fuels
Batteries are useful for short-term energy storage, and concentrated solar power plants could help stabilize the electric grid. However, utilities also need to store a lot of energy for indefinite amounts of time. This is a role for renewable fuels like hydrogen and ammonia. Utilities would store energy in these fuels by producing them with surplus power, when wind turbines and solar panels are generating more electricity than the utilities' customers need.
Today these fuels are mostly made from natural gas or other nonrenewable fossil fuels via extremely inefficient reactions. While we think of it as a green fuel, most hydrogen gas today is made from natural gas.
Scientists are looking for ways to produce hydrogen and other fuels using renewable electricity. For example, it is possible to make hydrogen fuel by splitting water molecules using electricity. The key challenge is optimizing the process to make it efficient and economical. The potential payoff is enormous: inexhaustible, completely renewable energy.
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