A few years ago, researchers announced the development of the blackest black ever, a place where colors go to die. It was called Vantablack®, and it was so absorptive of visible light that only the tiniest amount escaped its surface to reflect back to our eyes. (All of that light energy is dissipated into the surrounding substrate, so Vantablack doesn't become hot.)
In a new paper published in the journal ACS Applied Materials & Interfaces, scientists at Purdue University announced BaSO4 (barium sulfate), the whitest white ever. BaSO4 is practically impervious to the colors of the visible spectrum. Even better, while it's a very cool invention in the colloquial sense, it's also cool in the thermal sense.
The coolest white
The infrared image on the right shows how a square of the super-white paint and the board on which it's painted — shown in a normal image on the left — are cooler than the surrounding materials.Credit: Purdue University/Joseph Peoples
Most outside paints actually warm the surfaces to which they're applied. While there are already some reflective paints on the market, they only reflect 80 to 90 percent of sunlight, not enough for a cooling effect.
By contrast, BaSO4 results in 98.1 percent of sunlight bouncing off. According to senior investigator Xuilin Ruan, "If you were to use this paint to cover a roof area of about 1,000 square feet, we estimate that you could get a cooling power of 10 kilowatts. That's more powerful than the central air conditioners used by most houses."
Ruan and his colleagues tested BaSO4 using thermocouples, high-accuracy devices that measure voltage to determine temperature. They found that at night, BaSO4 surfaces are 19° F. cooler than surrounding air. Under strong sunlight the effect is not quite so extreme, but still dramatic: 8° of cooling.
The researchers even found the paint works in cold weather. Testing it on a 43° F. day, the surface on which BaSO4 was painted was a brisk 25° F. Their tests also indicate that BaSO4 is hardy enough for outdoor conditions.
How the new white was developed
Xuilin Ruan and a square of BaSO4Credit: Purdue University/Jared Pike
Research in the field of radiative paint for cooling goes back to the 1970s, though Ruan's team has been working toward BaSO4 for only six years. Along the way, they analyzed over 100 reflective materials, trying them out in about 50 experimental formulations.
Lead author, postdoc Xiangyu Li explains, "We looked at various commercial products, basically anything that's white. We found that using barium sulfate, you can theoretically make things really, really reflective, which means that they're really, really white."
The whitest white paint before — developed by the same team just last autumn — depended on calcium carbonate, a compound commonly found in seashells, rocks, and blackboard chalk.
The team crammed as many tiny BaSO4 particles into the paint as possible. Says Li: "Although a higher particle concentration is better for making something white, you can't increase the concentration too much. The higher the concentration, the easier it is for the paint to break or peel off."
Another factor that makes the team's BaSO4 formulation so reflective is that the researchers used barium sulfate particles of many different sizes. When it comes to reflecting light, size matters.
Co-author and PhD student Joseph Peoples said, "A high concentration of particles that are also different sizes gives the paint the broadest spectral scattering, which contributes to the highest reflectance."
The team's formulation method, they report, is compatible with commercial paint production.
Cool support for the planet
Purdue has applied for patents relating to BaSO4, though there are as yet no plans to make it commercially available.
However, the sooner they release it, the better. Air conditioning currently accounts for 12% of U.S. energy consumption. Also, many air conditioners use hydrofluorocarbons (HFCs). While HFCs constitute just a small percentage of greenhouse gases, they trap thousands of times the amount of heat as carbon dioxide.
Therefore, BaSO4 can play a role in combating global warming by reducing energy consumption and the emission of HFCs.
Ancient and near ancient records are often less than trustworthy. Even if you ignore the parts with reports of sea monsters or ants that mine gold, certain events often seem exaggerated. If we trust what the Greeks wrote, we'd have to assume Persia invaded with an impossibly high percentage of their entire population. The Romans, fond of showing how horrible the people they subdued were, spoke of the Celts using the Wicker Man for human sacrifice, though we can find no hard evidence of Wicker Men having existed.
You can probably understand why most historians take certain claims with a grain of salt, especially when those claims talk about dramatic events.
One seemingly mundane area this includes is the weather. What one person might record as an unprecedented weather event another person might think of as normal. Determining which account is correct a thousand years after the fact can be difficult, assuming that neither of them was exaggerating in the first place.
Luckily, as science marches on, it can provide new ways to investigate the past. An international team of researchers has managed to use isotopes from stalagmites in Northern Italy to better understand what the weather was like in the sixth century and to provide evidence for some fantastic historical records.
Ancient truths hidden in a cave
In a recent study published in Climatic Change, researchers investigated stalagmites in a cave in Tuscany. Stalagmites, which are the pointy rock formations on the ground in caves, provide a record of the environmental conditions they formed in. By examining different parts of the stalagmites, the team could determine what the climate was like, for instance if it was wetter or drier than normal, at different points in history. Uranium-thorium dating was used to provide precise dates for these points.
Oxygen isotope ratios were then measured to distinguish between wetter and drier periods. Combining this with the uranium-thorium data, the researchers could compile a timeline of climate activity over several hundred years. The oxygen isotope ratios in the sixth century indicated unusually wet weather.
The authors speculate that the moisture could have come from the North Atlantic Oscillation's negative phase, which tends to push moist air into Italy.
The water miracles of the Italian saints
Stalagmite Sample RL12, which was the focus of this study. Points on the sample that were used for dating and isotope collection are labeled. Zanchetta et al
While these findings provide strong evidence for lots of rain in Sixth Century Italy, this isn't the first report to suggest that the weather might have been extreme at the time.
Records of the saints from that time feature numerous examples of holy men somehow controlling troublesome water. One, the tale of St. Frigidian, features the saint successfully commanding the Serchio river to flow into a raked track he created, saving Lucca from flooding. A fifth of the miracles described in the Dialogues on the Miracles of the Italian Fathers, a record of saints, are "water miracles" of this kind.
While it is true that some of the most noteworthy miracles in the Bible involve water , such as the parting of the Red Sea by Moses, the miracles described in Dialogues are often unique feats with no obvious literary precursor, suggesting that they aren't repeats of existing stories in a new setting.
Additionally, French religious documents from the same period have no similar emphasis on water miracles. This suggests, though does not prove, that the Italians had separate motivations for listing so many of them.
Does this mean we can start trusting any old document?
Co-author Robert Wiśiewski of the University of Warsaw explained how documents like the Dialogues can be used to help improve our understanding of history:
"Literary sources, in particular stories about saints, should not be taken as a direct record of past events, They do, however, reflect the worldview of church writers and the basis for their interpretation of extraordinary weather phenomena."
Insects might often seem like a nuisance, yet life on this planet would be impossible without them. Sure, mosquitoes kill more humans every year than any other animal, but there's a trade-off when it comes to such invertebrates: without pollinators, we wouldn't be able to survive. And while Americans might scoff at the idea, insects are a food source for four-fifths of the planet (and Americans really should consider this route).
Speaking of 80 percent, that was the same percentage of one 2016 study regarding European insect collapse. More recent research has found that 40 percent of insect populations are in decline; one-third is in danger of extinction. On the face that sounds like more enjoyable summers until you realize that, for humans at least, the trend could result in no more summers at all. As two Australian researchers phrase it,
"Unless we change our ways of producing food, insects as a whole will go down the path of extinction in a few decades. The repercussions this will have for the planet's ecosystems are catastrophic to say the least."
Pesticides have long been identified as a driver of insect collapse. They're not the only agricultural problem, however. In fact, as a new study (published in Science) shows, the thousand little cuts that have led to climate change are driving extinction—especially, in this case, of monarch butterflies.
Insect ecologists Art Shapiro and Matthew Forister looked at 450 butterfly species at 70 different locations in the western United States. While butterfly numbers have been dropping regularly since 1977 at a rate of 1.6 percent every year, the trend seems to be increasing. Just last month, a disturbing report from Mexico found that the hibernating population of monarchs has decreased by 26 percent since 2019, predominantly due to deforestation and drought— factors helping drive or due to climate change.
Credit: Dave / Adobe Stock
While problematic, human development and pesticides have nowhere near the impact of warming autumns. Fall temperatures have outpaced summer increases for years, disrupting butterfly breeding patterns and the life cycles of the plants they depend on.
Fewer butterflies aren't just an aesthetic problem. Forister notes that the loss of these key pollinators could cause an ecosystem collapse in the coming years. Hotter falls also negatively impact bee populations. Recent colony collapses in Colombia are likely the result of monocropping avocados and citrus.
The enormity of this problem cannot be overstated. Insects fertilize for us—three-quarters of all crops across the globe. According to a 2016 study, 1.4 billion jobs depend on pollinators. With the loss of insects, our food supply (and a giant economic driver of society) goes with them.
Regional efforts to save monarch butterflies are underway. Tribal organizations in Oklahoma are trying to replant milkweed—often viewed as a pest by farmers—to boost butterfly populations. The Tribal Alliance for Pollinators (TEAM) has secured nearly a quarter-million dollars in the last three years to plant milkweed and nectar plants to help the annual butterfly migration to Mexico.
The road ahead will not be easy. Until legislative measures are enforced to curb climate change, seasons will continue to be unpredictable: warmer autumns, colder winters, especially in places unaccustomed to such drastic changes in temperature—last month's storms in Texas provide a cautionary tale. Yet we've had many such tales at this point. With the loss of insects, there won't be any more stories left to be told.
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Stay in touch with Derek on Twitter and Facebook. His most recent book is "Hero's Dose: The Case For Psychedelics in Ritual and Therapy."
