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Archaeologists recreated three common kinds of Paleolithic cave lighting



Enlarge / Spanish archaeologists recreated three common types of Paleolithic lighting systems.

Medina-Alcaide et al, 2021, PLOS ONE

In 1993, a media studies professor at Fordham University named Edward Wachtel visited several famous caves in southern France, including Lascaux, Font-de-Gaume, Les Combarelles, and La Mouthe. His purpose: to study the cave art that has justly made these caves famous.  Wachtel was puzzled by what he called “spaghetti lines” on the drawings, partially obscuring them. There were also images of, say, an ibex with two heads, a mammal with three trunks, or a bull drawing superimposed over the drawing of a deer.

His guide for the La Mouthe tour was a local farmer, and since there were no electric lights in this cave, the farmer brought along a gas lantern. When the farmer swung the lantern inside the cave, the color schemes shifted, and the engraved lines seemed to animate. “Suddenly, the head of one creature stood out clearly,” Wachtel recalled. “It lived for a second, then faded as another appeared.” As for those mysterious spaghetti lines, “they became a forest or a bramble patch that concealed and then reveled the animals within.”

Wachtel subsequently published a paper entitled, “The First Picture Show: Cinematic Aspects of Cave Art,” in which he concluded that the cave drawings were meant to be perceived in three dimensions—one of them being time. These could have been the first “protomovies,” he thought.

It’s an intriguing take, although it must be said that Wachtel’s ideas are speculative. There is no way to definitively prove what those prehistoric cave artists intended, and therefore it’s unwise to draw strong inferences about these being cinematic in nature, or to assume that this tells us anything about prehistoric artists’ conception of time. But his point about the importance of viewing cave paintings under the lighting conditions in which they were created and viewed in prehistoric times is sound.

La Mouthe: (left) Painted etching of a hut (or an animal trap). Edward Wachtel found that a moving, flickering light source would cause the colors of the hut to change, and the animals around it to appear and disappear. (right) A sketch shows "spaghetti lines" over various animals
Enlarge / La Mouthe: (left) Painted etching of a hut (or an animal trap). Edward Wachtel found that a moving, flickering light source would cause the colors of the hut to change, and the animals around it to appear and disappear. (right) A sketch shows “spaghetti lines” over various animals

Wachtel’s story recently resurfaced in a Twitter thread, and it couldn’t be more timely. Lighting sources could indeed hold vital clues to the different ways prehistoric peoples used caves, according to a new paper by a team of Spanish scientists, published in the journal PLOS ONE. They conducted in situ experiments with three different kinds of Paleolithic lighting sources, in the hopes of shedding some light (pun intended) on what those various illumination methods might tell us about the emergence of “human symbolic and artistic behavior” in the form of cave art.

There are nearly 350 such prehistoric caves in France and Spain alone, including the oldest cave painting yet known: a red hand stencil in Maltravieso cave in Caceres, Spain, likely drawn by a Neanderthal some 64,000 years ago. (The oldest known depiction of an animal was discovered in 2018 on the island of Borneo in Indonesia, dating back 40,000 years.) The Spanish team chose to conduct their experiments at the Isuntza 1 Cave in Spain’s Basque country, and selected two distinct spaces in particular.

The first was a large, wide chamber with walls of bedrock, with 99.7 percent relative humidity and an average temperature of 17.6 degrees C (63.6 degrees F).  They thought it would be ideal as a “staying chamber” for the experiments The second space was a second, slightly smaller chamber with similar relative humidity (99.9 percent) and average temperatures (14.2 degrees C, or 57.5 degrees F) similar to the first space. The two spaces are connected by a rough passage 40 meters long (about 131 feet).

Upper Paleolithic cave paintings in Altamira Cave, Spain.
Enlarge / Upper Paleolithic cave paintings in Altamira Cave, Spain.

DEA Picture Library/De Agostini/Getty Images

The Spanish researchers chose lighting types for their eight experiments based on known archaeological data: five torches tested in both spaces and the passage, as well as two stone lamps with animal fat, and a small fireplace, both tested just in the first space. All the torches were made from dry juniper branches joined together, like the remains of ancient torches found in the Aldene and Reseau Clastres caves. The researchers included a bit of birch to act as tinder, and added pine resin, animal fat, or a combination thereof to assess how well different fuel types worked.

The lamps were replicas of a sandstone lamp found in La Mouthe Cave in Dordogne, France. They used bovine animal fat as fuel, with three juniper wicks, arranged in a teepee shape inside the lamp. They also built a small fireplace on a clay substrate in the first chamber with juniper and oak as wood fuel.

For all the lighting experiments, the team measured how long the lighting source lasted (duration); the total amount of light reaching a specific surface or point relative to the human eye (illuminance, or lux); how much illumination was emitted in certain directions (luminous intensity); the minimum distance between the light source and total darkness (action radius); and luminance, which connects light intensity with the surface of the source. They also kept track of the highest temperature reached by each type of lighting source.

Those measurements showed that the various lighting sources had very different characteristics, and thus were probably used in different contexts. The wooden torches, for instance, emitted light in all directions, up to nearly six meters (19.6 feet), and lasted an average of 41 minutes. The torches exhibited uneven light intensity, and often needed to be relit by waving them from side to side, and they produced a lot smoke. So they worked best for exploring caves or crossing wide spaces. The team also found that adding resin intensified the flame, while adding animal fat extended its duration.

In contrast, the grease lamps emitted weaker light akin to the intensity of a candle, over a span of three meters (9.8 feet) or so. They burned consistently, and didn’t smoke, for over an hour, but they had a dazzling effect if the person was moving and didn’t illuminate the floor very well. Also, “It was necessary to maintain constant control over the wick to prevent it from sinking into the fatty fuel, causing the flame to be extinguished,” the authors wrote. This makes the lamps better suited for lighting small cave spaces over a longer period, complementing the advantages of the torches.

As for the fireplace—the only truly static system—its illumination covered a range of 6.6 meters (21.6 feet). However, it burned for just 30 minutes and gave off a lot of white smoke, making it unsuitable for use unless there were strong enough air currents to disperse that smoke. “The fireplace location was not appropriately placed regarding air currents,” the authors noted, which are “essential to achieving a prolonged stay underground. However, in the case of large fires, convection currents are produced, and they would be efficient enough to evacuate gases outside of the cave.”

The Spanish team also built a virtual 3D model of a section of the Atxurra cave known as the Ledge of the Horses. It’s a naturally formed platform just above a passage floor, with two panels of about 50 animal engravings: bison, goats, horses, and hinds, many of them overlapping. The ledge was also littered with scattered charcoal, lithic tools, and ashes from three probable fireplaces. In the virtual model, they conducted a spatial analysis of all three tested lighting sources.

The modeling showed that the decorated panels would be “barely perceptible” to someone standing in the lower parts of the gallery, even if that person were carrying a lamp or a torch. It would need to be illuminated from the top of the ledge to be seen. In contrast, the fireplaces appeared to be strategically located to illuminate the entire decorated space. Torches did prove to be a good lighting source for accessing that space, however, with an estimated travel time of 38.39 minutes—in line with the measured duration of the torches. “It does not seem by chance that the optimal routes estimated to access this space are covered with scattered charcoals, surely fallen from the torches used in the Magdalenian period,” the authors wrote.

The findings have no direct bearing on Wachtel’s speculation about prehistoric cinematic art. But the more archaeologists learn about Paleolithic lighting sources, the more we will understand about how those lighting sources affect human perception in a cave environment, with implications for the emergence of cave art. That’s why the Spanish team thinks it is essential to continue conducting these kinds of experiments.

“Only with a large corpus of archaeological remains, including different types of lighting systems (and fuels), studied through an interdisciplinary approach, will it be possible to adequately reproduce Paleolithic light resources,” they concluded in their paper, “Our experiments in Paleolithic lighting point to planning in the human use of caves in this period, and the importance of lighting studies to travel the activities carried out by our ancestors in the deep areas of caves. “

DOI: PLOS ONE, 2021. 10.1371/journal.pone.0250497  (About DOIs).

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Missouri AG wages war on masks as state blazes with delta cases



Enlarge / Eric Schmitt, Missouri Attorney General.

Missouri has been one of the hardest-hit states so far in these early days of a delta-fueled COVID-19 surge. Cases increased nearly 500 percent since the start of July, while vaccinations stalled. Right now, with just 41 percent of the state fully vaccinated, 112 of the state’s 114 counties have high or substantial levels of coronavirus spread. Hospitalizations are up statewide, and some facilities have already run out of ventilators and seen intensive care units hit maximum capacity. Deaths are also increasing, with more than 300 people losing their lives this month since July 1. And the proportion of COVID-19 tests coming back positive is still rising, suggesting that things will likely only get worse in the weeks to come.

By nearly every metric, this entirely preventable surge is tragic. Yet, it hasn’t stopped the Show Me State’s Republican attorney general, Eric Schmitt, from waging war on local health restrictions aimed at trying to curb transmission. On Monday, Schmitt filed a lawsuit to stop St. Louis County and St. Louis City from enforcing mask mandates for fully vaccinated people and children, which took effect that day.

The timing of the lawsuit is awkward. It partly rests on now-outdated guidance from the Centers for Disease Control and Prevention that fully vaccinated people didn’t need to wear masks in most indoor settings. “The Mask Mandates are arbitrary and capricious because they require vaccinated individuals to wear masks, despite the CDC guidance that this is not necessary,” the lawsuit claims. The rest of the lawsuit didn’t argue that masks were ineffective at curbing transmission but rather claimed that they were unnecessary for children—despite that they are largely ineligible for vaccinations—and that requiring them is “unconstitutional.” Otherwise, the lawsuit nitpicked language of the mandates, such as alleging that they didn’t define the word “dwelling.”

The CDC reversed its mask policy Tuesday, citing evidence that even fully vaccinated people are catching and spreading the hypertransmissible delta coronavirus variant—though at much lower frequencies than unvaccinated people. The agency now recommends universal masking in K-12 schools and that fully vaccinated people mask in indoor public settings when local transmission is high or substantial. Both the city and county of St. Louis have high levels of COVID-19 transmission, as defined by the CDC.

Lies and freedoms

Still, Schmitt is not backing down. Though his office did not immediately respond to a request from Ars, Schmitt took to Twitter and Fox News to blast the CDC’s update.

“People are tired of being lied to by elites & the ruling class,” Attorney General Schmitt, who is also running for US Senate, tweeted on Tuesday evening. “We were told—get vaccinated and you don’t have to wear a mask. Now the vaccinated are forced to wear masks in St. Louis. Kids forced to wear masks too. The lies go on and on.”

On Wednesday, Kansas City’s Democratic Mayor Quinton Lucas announced that he, too, would reinstate an indoor mask mandate in the city for all persons aged five and older, regardless of vaccination status. And Schmitt quickly said that he would sue to stop that mandate as well.

“To the great people of Kansas City: I will be filing a lawsuit to protect your freedoms,” Schmitt tweeted Wednesday. This mask mandate is about politics & control, not science. You are not subjects but citizens of what has been the freest country in the world & I will always fight for you.”

It’s unclear how the lawsuits will pan out, but Mayor Lucas has already noted that he intends to put up a fight of his own. A press release from his office stated:

In light of recent litigation between the State of Missouri and the City and County of St. Louis, Mayor Lucas will also introduce a resolution in the weeks ahead for City Council support of emergency actions. Mayor Lucas stands with Mayor Tishaura Jones and County Executive Sam Page in protecting Missourians from the spread of COVID-19.

In St. Louis, County Executive Page also stood behind the mask mandate. The courts will decide its fate, he said, according to the St. Louis Post-Dispatch, but “until then, the law stands.” Page argued that masks are necessary to help lower transmission as more people get vaccinated. “These cases, and this curve is shooting straight up,” he said. “And if we don’t make some decisions fast, we’re going to be in a bad spot.”

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A global index to track the health of tropical rainforests



We’ve known for decades that tropical rainforests are special. They’re nearly unrivaled in biodiversity, and research has shown that they absorb more carbon dioxide than any other ecosystem. A recent study showed that the tropics sequester four times as much carbon dioxide as temperate and boreal ecosystems combined—and several studies have estimated that all terrestrial ecosystems combined sequester as much as 30 percent of the total carbon dioxide in the atmosphere each year.

We’ve also known for decades that these ecosystems are at risk of vanishing. As much as 20 percent of tropical rainforests have been cleared in the last 30 years, with an additional 10 percent lost to degradation. Beyond these direct threats, forests worldwide, and especially rainforests, are experiencing severe losses due to climate change—notably higher temperatures and drought.

Until now, there haven’t been means to systematically keep tabs on the health of these critical ecosystems. But a collaboration of nearly 50 institutions has recently developed a comprehensive index to measure the health and vulnerability of all tropical rainforests around the world. The result is a potential warning system that allows scientists and policymakers to monitor and prioritize which forests are at the highest risk of irreversible damage and loss.

“Rainforests regulate the Earth’s climate; if they cannot function well—the patterns of climate will change almost everywhere on Earth,” says lead author Sassan Saatchi of the Jet Propulsion Laboratory at the California Institute of Technology and the Institute of Environment and Sustainability at the University of California, Los Angeles. “If we lose the ability of the tropical forests to function normally, for example absorb the carbon from the atmosphere, it may mean that all of the efforts we’re doing in terms of climate change mitigation may become moot.”

Preventing tipping points

This new tropical forest vulnerability index (TFVI) combines close to a dozen data sets spanning up to 37 years of measurements (1982–2018). Past efforts have focused on limited regions or have largely relied on fieldwork, but the TFVI brings together a wide range of available measurements and models of rainforest stresses and responses.

Stress measurements included climate data about temperature, the dryness of the air (vapor pressure deficit), and the amount of water entering and leaving each system (the water balance). Responses included tree cover, carbon storage, above-ground biomass, productivity, and evapotranspiration—the amount of water that each system exchanges with the atmosphere during photosynthesis. Available measurements also included an existing biodiversity index and the temperature of the land surface or, in forests, the temperature of the tree and leaf surfaces. In addition, models and satellite data were calibrated with ground readings as much as possible.

When combined, these measurements give a historical record of the overall health and functioning of rainforests around the world over the past several decades. From this, it’s possible to see how much stress different forests have survived in the past and to flag current and future stress readings that are far outside of past variations. The researchers suggest that too many stresses may create feedback loops that lead to tipping points, beyond which a forest will no longer recover, and the damage will become irreversible. Such tipping points can be rapid and cause mass tree deaths, or they can trigger relatively gradual transitions to a different ecosystem type, like a savanna.

Global rainforest health check

Based on current measurements, the index shows that forests in the Amazon are particularly vulnerable, while African forests in the Congo Basin are more resilient. The authors suspect this may be due to less development in the Congo Basin, as well as a history of more frequent droughts there. Forests in Asia are particularly threatened by land use and forest fragmentation.

The intention of the index is to help the early identification of forests that are in the most need of additional protections, as well as to provide specific guidance on exactly which stress factors the forests are experiencing. While some interventions, like slowing climate change, may require longer-term solutions, others—like forest fragmentation—could be managed with restoration projects.

The authors were also careful to include measures of uncertainty throughout the index, and the code for the index is freely accessible so that anyone can use it and, hopefully, improve upon it as well. Every month, the index is updated with the latest data, and the team expects to launch an online version in the next year.

“This index is not the ultimate answer. One of the biggest caveats is that, as much as we know about the ecosystem, we are always surprised how the ecosystem works, and it can still become vulnerable to something that we don’t know about, or it may become resilient to something that we thought it has been vulnerable to,” says Saatchi. “But this is a work in progress, and the more knowledge we gain in terms of the function of these ecosystems, the better we can predict which direction they’ll go. The index will help us to continuously take the pulse of global rainforests as their health is changing.”

Science Advances, 2021. DOI: 10.1126/sciadv.abe9829

K.E.D. Coan is a freelance journalist covering climate and environment stories at Ars Technica. She has a PhD in chemistry and chemical biology.

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Rocket Lab not yet close to profitability, proxy statement reveals



Enlarge / Peter Beck, founder of Rocket Lab, is seen as essential to Rocket Lab’s success.

Rocket Lab

Running a rocket launch company is an expensive proposition. You need hundreds of employees, lots of expensive machines and tooling, plenty of hardware, and at least one launch site. To make matters worse, for a purely commercial launch firm like Rocket Lab, you typically only get paid when you deliver someone’s satellite into orbit.

So it is perhaps no surprise that the US-based company, which launches from New Zealand and has about 600 employees, has been losing a lot of money. According to a new proxy statement, Rocket Lab experienced net losses of $30 million and $55 million in 2019 and 2020, respectively. Given the company’s financial position, an independent auditor, according to the proxy statement, “expressed substantial doubt” about Rocket Lab’s “ability to continue as a going concern.”

These are the kinds of details we rarely see in the often financially opaque launch business, but as part of the process of converting into a publicly traded Special Purpose Acquisition Company, Rocket Lab had to make extensive financial disclosures. The full 712-page document can be downloaded here.

Rocket Lab reported revenue of $48 million in 2019 and $35 million in 2020. The decrease last year was due, in part, to the COVID-19 pandemic, the company said. It has contracts for 15 additional Electron launches for this year and beyond, valued at $127 million in launch and space systems revenue.

As of March 31 of this year, Rocket Lab has $34.2 million of cash and cash equivalents on hand. In addition to this, the company said it has access to both a $35 million revolving line of credit and a $100 million secured loan with Hercules Capital that is not repayable until June 2024. Rocket Lab acknowledged that there may be a fairly long pathway to profitability.

“We expect to continue to incur net losses for the next several years and we may not achieve or maintain profitability in the future,” the proxy statement says. “We believe there is a significant market opportunity for our business, and we intend to invest aggressively to capitalize on this opportunity.”

These financial losses may not cool the ardor of investors in Vector Acquisition Corporation, which is seeking to merge with Rocket Lab later this summer. Shareholders in Vector are due to vote on the proposed merger at a meeting on August 20. This merger will provide Rocket Lab with about $500 million in cash.

One reason investors will probably still be interested in Rocket Lab is that, unlike a lot of the space companies that have recently gone the SPAC route to become publicly traded, the launch company has solid revenue, demonstrated hardware, and a path toward growing its business.

Rocket Lab is already working to expand beyond small launch, including building its own satellites, performing satellite servicing in orbit, and building a medium-lift rocket called Neutron with a reusable first stage. In the proxy statement, Rocket Lab noted that Neutron has lift capacity of up to 8 metric tons to low-Earth orbit, 2 tons to the Moon, and 1.5 tons to Mars and Venus. Its first launch may occur as early as 2024.

Neutron, the company said, “will enable significantly higher revenue per launch with its capability to deploy larger spacecraft and greater numbers of spacecraft per launch as compared to our Electron launch vehicle, and will also be capable of supporting crewed flight and cargo resupply to the International Space Station.”

In terms of risks, the company cited the unexpected but potential loss of Peter Beck as its leader. Fiery, charismatic, and demanding of his employees, Beck has relentlessly promoted the Rocket Lab brand publicly and been a key driver of its technological innovation, the company said.

“We are highly dependent on the services of Peter Beck, our President, Chief Executive Officer and Chairman,” the proxy statement said. “Mr. Beck is the source of many, if not most, of the ideas and execution driving our company. If Mr. Beck were to discontinue his service to us due to death, disability or any other reason, we would be significantly disadvantaged.”

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