Face mask study reveals worst material for blocking COVID-19
A study published Friday tested how well 14 commonly available face masks blocked the emission of respiratory droplets as people were speaking.
- The study tested the efficacy of popular types of face masks, including N95 respirators, bandanas, cotton-polypropylene masks, gaiters, and others.
- The results showed that N95 respirators were most effective, while wearing a neck fleece (aka gaiter) actually produced more respiratory droplets than wearing no mask at all.
- Certain types of homemade masks seem to be effective at blocking the spread of COVID-19.
Which face mask best protects against COVID-19? To find out, a team of researchers at Duke University recently conducted a simple experiment.
The team measured how well 14 popular face masks blocked respiratory droplets from exiting people's mouths while speaking. To measure the droplets, the researchers used "a black box, a laser, and a camera," Martin Fischer, one of the authors of the study, told CNN.
"The laser beam is expanded vertically to form a thin sheet of light, which we shine through slits on the left and right of the box."
Fischer et al.
A smartphone camera recorded video of the participants, and a computer algorithm counted the number of droplets they emitted. To establish a control trial, the participants spoke into the box both with and without a mask. And to make sure that the droplets weren't in fact dust from the masks, the team conducted more tests by "repeatedly puffing air from a bulb through the masks."
Fischer et al.
The results, published Friday in Science Advances, showed that some masks are pretty much useless. In particular, neck fleeces (also called gaiters) actually produced more respiratory droplets compared to the control trial — likely because the fabric breaks down big droplets into smaller ones.
The top three most effective masks were N95 respirators, surgical masks, and polypropylene-cotton masks. Bandanas performed the worst, but were slightly better than wearing no mask at all.
Fischer et al.
Research on mask efficacy is still emerging. But the new results seem to generally align with prior tests. For example, a study from June published in Physics of Fluid found that bandanas (followed by folded handkerchiefs) were least effective at blocking respiratory droplets. That same study also found, as others have, that masks made from multiple layers of quilter's fabric were especially effective at blocking droplets.
The researchers hope other institutions will conduct similar experiments so the public can see how well different masks can block the spread of COVID-19.
"This is a very powerful visual tool to raise awareness that a very simple masks, like these homemade cotton masks, do really well to stop the majority of these respiratory droplets," Fischer told CNN. "Companies and manufacturers can set this up and test their mask designs before producing them, which would also be very useful."
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The idea of 'absolute time' is an illusion. Physics and subjective experience reveal why.
- Since Einstein posited his theory of general relativity, we've understood that gravity has the power to warp space and time.
- This "time dilation" effect occurs even at small levels.
- Outside of physics, we experience distortions in how we perceive time — sometimes to a startling extent.
Physics without time<p>In his book "The Order of Time," Italian theoretical physicist Carlo Rovelli suggests that our perception of time — our sense that time is forever flowing forward — could be a highly subjective projection. After all, when you look at reality on the smallest scale (using equations of quantum gravity, at least), time vanishes.</p><p style="margin-left: 20px;">"If I observe the microscopic state of things," writes Rovelli, "then the difference between past and future vanishes … in the elementary grammar of things, there is no distinction between 'cause' and 'effect.'"</p><p>So, why do we perceive time as flowing <em>forward</em>? Rovelli notes that, although time disappears on extremely small scales, we still obviously perceive events occur sequentially in reality. In other words, we observe entropy: Order changing into disorder; an egg cracking and getting scrambled.</p><p>Rovelli says key aspects of time are described by the second law of thermodynamics, which states that heat always passes from hot to cold. This is a one-way street. For example, an ice cube melts into a hot cup of tea, never the reverse. Rovelli suggests a similar phenomenon might explain why we're only able to perceive the past and not the future.</p><p style="margin-left: 20px;">"Any time the future is definitely distinguishable from the past, there is something like heat involved," Rovelli wrote for the <a href="https://www.ft.com/content/ce6ef7b8-429a-11e8-93cf-67ac3a6482fd" target="_blank"><em>Financial Times</em></a>. "Thermodynamics traces the direction of time to something called the 'low entropy of the past', a still mysterious phenomenon on which discussions rage."</p>
The strange subjectivity of time<p>Time moves differently atop a mountain than it does on a beach. But you don't need to travel any distance at all to experience strange distortions in your perception of time. In moments of life-or-death fear, for example, your brain would release large amounts of adrenaline, which would speed up your internal clock, causing you to perceive the outside world as moving slowly.<br></p><p>Another common distortion occurs when we focus our attention in particular ways.</p><p style="margin-left: 20px;">"If you're thinking about how time is <em>currently</em> passing by, the biggest factor influencing your time perception is attention," Aaron Sackett, associate professor of marketing at the University of St. Thomas, told <em><a href="https://gizmodo.com/why-does-time-slow-down-and-speed-up-1840133782" target="_blank">Gizmodo</a></em>.<em> "</em>The more attention you give to the passage of time, the slower it tends to go. As you become distracted from time's passing—perhaps by something interesting happening nearby, or a good daydreaming session—you're more likely to lose track of time, giving you the feeling that it's slipping by more quickly than before. "Time flies when you're having fun," they say, but really, it's more like "time flies when you're thinking about other things." That's why time will also often fly by when you're definitely <em>not</em> having fun—like when you're having a heated argument or are terrified about an upcoming presentation."</p><p>One of the most mysterious ways people experience time-perception distortions is through psychedelic drugs. In an interview with <a href="https://www.theguardian.com/books/2018/apr/14/carlo-rovelli-exploding-commonsense-notions-order-of-time-interview" target="_blank"><em>The Guardian</em></a>, Rovelli described a time he experimented with LSD.</p><p style="margin-left: 20px;">"It was an extraordinarily strong experience that touched me also intellectually," he said. "Among the strange phenomena was the sense of time stopping. Things were happening in my mind but the clock was not going ahead; the flow of time was not passing any more. It was a total subversion of the structure of reality."<br></p><p>It seems few scientists or philosophers believe time is completely an illusion.</p><p style="margin-left: 20px;">"What we call <em>time</em> is a rich, stratified concept; it has many layers," Rovelli told <em><a href="https://physicstoday.scitation.org/do/10.1063/PT.6.4.20190219a/full/" target="_blank">Physics Today</a>.</em> "Some of time's layers apply only at limited scales within limited domains. This does not make them illusions."</p>What <em>is</em> an illusion is the idea that time flows at an absolute rate. The river of time might be flowing forever forward, but it moves at different speeds, between people, and even within your own mind.
Dominique Crenn, the only female chef in America with three Michelin stars, joins Big Think Live.
Having been exposed to mavericks in the French culinary world at a young age, three-star Michelin chef Dominique Crenn made it her mission to cook in a way that is not only delicious and elegant, but also expressive, memorable, and true to her experience.
Controversial physics theory says reality around us behaves like a computer neural network.
- Physicist proposes that the universe behaves like an artificial neural network.
- The scientist's new paper seeks to reconcile classical physics and quantum mechanics.
- The theory claims that natural selection produces both atoms and "observers".
Vanchurin interview:<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="539759cbfd8fcd5b6ebf14a3b597b3f9"><iframe type="lazy-iframe" data-runner-src="https://www.youtube.com/embed/bmyRy2-UhEE?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span>
Vanchurin on “Hidden Phenomena”:<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="18886ffd5e5840bb19d4494212f88d82"><iframe type="lazy-iframe" data-runner-src="https://www.youtube.com/embed/2NDVdNwsHCo?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span>Vitaly Vanchurin speaking at the 6th International FQXi Conference, "Mind Matters: Intelligence and Agency in the Physical World." The Foundational Questions...
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