New 3D computer model shows how far a cough can spread indoors

This unsettling simulation shows how mucus-mist can rapidly spread in a grocery store.

cough simulation
  • Finnish researchers have shown how a single cough can blast small aerosolized saliva particles around a grocery store.
  • There is an ongoing scientific debate about how the novel coronavirus moves through the air.
  • The bigger risk when it comes to COVID-19 is the transmission of larger droplets through close contact with others (three feet or less).

Using a computer simulation, researchers in Finland have shown how a single cough can blast small saliva and mucus particles around a grocery store well beyond a six-foot social distancing radius.

In the 3D simulation, a cloud of green particles originating from a person coughing in one aisle are shown spreading into the next aisle over. The cough releases a turbulent mist of droplets — aerosolized particles — which stay suspended in the air and move over into the parallel row.

Knowledge gaps

These findings highlight an ongoing scientific debate about how the novel coronavirus moves through the air. The simulation's images are certainly concerning, but the risk of actually getting enough of a virus aerosol to contract a respiratory illness like COVID-19 is unknown according to Kumi Smith, an assistant professor of epidemiology and community health at the University of Minnesota. She told Business Insider that while the video "gives the impression that any shared airspace will lead to transmission," evidence has yet to support that.

When it comes to COVID-19, the bigger risk comes from close contact with another person within three feet or less through which larger droplets (larger than five to 10 microns) could be transmitted by talking, coughing, or sneezing. The larger the droplet the more likely it is to fall onto nearby objects or to the ground after expulsion. So if a person touches these droplets and then rubs his or her face, they could contract the virus. (Hence, the importance of frequent hand washing.) William Schaffner, a professor of preventive medicine and infectious diseases at Vanderbilt University Medical Centre, told Business Insider that droplet transmission within three to six feet accounts for a majority of virus transmissions.

But while close interactions between people are much more likely to spread an infectious dose of virus-laden particles, other research indicates the large versus small droplets difference may be irrelevant when it comes to distance between individuals. For example, Lydia Bourouiba, a fluid dynamics scientist at MIT, recently showed that a sneeze can spray droplets of various sizes a whopping 23 to 27 feet from a nose. And while a sneeze is not a typical symptom of coronavirus, an asymptomatic person who randomly sneezes could expel and spread the pathogen.

The importance of distancing

two men social distancing while wearing protective masks

Photo: Kate Trifo on Unsplash

The Finnish simulation and Bourouiba's research emphasize how important social distancing measures, as well as additional precautions like wearing masks, are to public. Earlier this month, the Centers for Disease Control and Prevention (CDC) officially advised that Americans wear masks or other mouth and nose coverings when going out in public to prevent the spread of the virus. If everyone abided by these recommendations, the coronavirus crisis would likely be sufficiently addressed. Facial coverings are most effective at stopping the potential spread of the virus to others, so long as they are properly used, rather than as a way to guard yourself. According to the World Health Organization, there is currently no evidence that wearing a mask protects healthy people from becoming infected with respiratory infections. But since anyone could be asymptomatic and carrying COVID-19, we should all be covering our face by some means while in public areas.

However, wearing a mask doesn't mean you should let your guard down. It should supplement social distancing and other protective protocols, not replace them. So continue to maintain that minimum six--foot distance, keep washing your hands, and please cover your mouth when you cough or sneeze.

A landslide is imminent and so is its tsunami

An open letter predicts that a massive wall of rock is about to plunge into Barry Arm Fjord in Alaska.

Image source: Christian Zimmerman/USGS/Big Think
Surprising Science
  • A remote area visited by tourists and cruises, and home to fishing villages, is about to be visited by a devastating tsunami.
  • A wall of rock exposed by a receding glacier is about crash into the waters below.
  • Glaciers hold such areas together — and when they're gone, bad stuff can be left behind.

The Barry Glacier gives its name to Alaska's Barry Arm Fjord, and a new open letter forecasts trouble ahead.

Thanks to global warming, the glacier has been retreating, so far removing two-thirds of its support for a steep mile-long slope, or scarp, containing perhaps 500 million cubic meters of material. (Think the Hoover Dam times several hundred.) The slope has been moving slowly since 1957, but scientists say it's become an avalanche waiting to happen, maybe within the next year, and likely within 20. When it does come crashing down into the fjord, it could set in motion a frightening tsunami overwhelming the fjord's normally peaceful waters .

"It could happen anytime, but the risk just goes way up as this glacier recedes," says hydrologist Anna Liljedahl of Woods Hole, one of the signatories to the letter.

The Barry Arm Fjord

Camping on the fjord's Black Sand Beach

Image source: Matt Zimmerman

The Barry Arm Fjord is a stretch of water between the Harriman Fjord and the Port Wills Fjord, located at the northwest corner of the well-known Prince William Sound. It's a beautiful area, home to a few hundred people supporting the local fishing industry, and it's also a popular destination for tourists — its Black Sand Beach is one of Alaska's most scenic — and cruise ships.

Not Alaska’s first watery rodeo, but likely the biggest

Image source: whrc.org

There have been at least two similar events in the state's recent history, though not on such a massive scale. On July 9, 1958, an earthquake nearby caused 40 million cubic yards of rock to suddenly slide 2,000 feet down into Lituya Bay, producing a tsunami whose peak waves reportedly reached 1,720 feet in height. By the time the wall of water reached the mouth of the bay, it was still 75 feet high. At Taan Fjord in 2015, a landslide caused a tsunami that crested at 600 feet. Both of these events thankfully occurred in sparsely populated areas, so few fatalities occurred.

The Barry Arm event will be larger than either of these by far.

"This is an enormous slope — the mass that could fail weighs over a billion tonnes," said geologist Dave Petley, speaking to Earther. "The internal structure of that rock mass, which will determine whether it collapses, is very complex. At the moment we don't know enough about it to be able to forecast its future behavior."

Outside of Alaska, on the west coast of Greenland, a landslide-produced tsunami towered 300 feet high, obliterating a fishing village in its path.

What the letter predicts for Barry Arm Fjord

Moving slowly at first...

Image source: whrc.org

"The effects would be especially severe near where the landslide enters the water at the head of Barry Arm. Additionally, areas of shallow water, or low-lying land near the shore, would be in danger even further from the source. A minor failure may not produce significant impacts beyond the inner parts of the fiord, while a complete failure could be destructive throughout Barry Arm, Harriman Fiord, and parts of Port Wells. Our initial results show complex impacts further from the landslide than Barry Arm, with over 30 foot waves in some distant bays, including Whittier."

The discovery of the impeding landslide began with an observation by the sister of geologist Hig Higman of Ground Truth, an organization in Seldovia, Alaska. Artist Valisa Higman was vacationing in the area and sent her brother some photos of worrying fractures she noticed in the slope, taken while she was on a boat cruising the fjord.

Higman confirmed his sister's hunch via available satellite imagery and, digging deeper, found that between 2009 and 2015 the slope had moved 600 feet downhill, leaving a prominent scar.

Ohio State's Chunli Dai unearthed a connection between the movement and the receding of the Barry Glacier. Comparison of the Barry Arm slope with other similar areas, combined with computer modeling of the possible resulting tsunamis, led to the publication of the group's letter.

While the full group of signatories from 14 organizations and institutions has only been working on the situation for a month, the implications were immediately clear. The signers include experts from Ohio State University, the University of Southern California, and the Anchorage and Fairbanks campuses of the University of Alaska.

Once informed of the open letter's contents, the Alaska's Department of Natural Resources immediately released a warning that "an increasingly likely landslide could generate a wave with devastating effects on fishermen and recreationalists."

How do you prepare for something like this?

Image source: whrc.org

The obvious question is what can be done to prepare for the landslide and tsunami? For one thing, there's more to understand about the upcoming event, and the researchers lay out their plan in the letter:

"To inform and refine hazard mitigation efforts, we would like to pursue several lines of investigation: Detect changes in the slope that might forewarn of a landslide, better understand what could trigger a landslide, and refine tsunami model projections. By mapping the landslide and nearby terrain, both above and below sea level, we can more accurately determine the basic physical dimensions of the landslide. This can be paired with GPS and seismic measurements made over time to see how the slope responds to changes in the glacier and to events like rainstorms and earthquakes. Field and satellite data can support near-real time hazard monitoring, while computer models of landslide and tsunami scenarios can help identify specific places that are most at risk."

In the letter, the authors reached out to those living in and visiting the area, asking, "What specific questions are most important to you?" and "What could be done to reduce the danger to people who want to visit or work in Barry Arm?" They also invited locals to let them know about any changes, including even small rock-falls and landslides.

Harvard study finds perfect blend of fruits and vegetables to lower risk of death

Eating veggies is good for you. Now we can stop debating how much we should eat.

Credit: Pixabay
Surprising Science
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The common cuttlefish

Credit: Hans Hillewaert via Wikicommons
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