6 Feet isn’t enough distance!

MrPaul

The news article:

https://www.theladders.com/career-advice/mit-researcher-says-the-6-feet-social-distancing-rule-isnt-enough-to-flatten-the-curve

The research paper:

https://jamanetwork.com/journals/jama/fullarticle/2763852

Sneeze gas cloud image:


Summary:
1. Stay at least two car lengths away from other people (think sedan not mini).
2. Wear a mask if you have to go out and expect to encounter people, or if you enter an occupied building that has a ventilation system.

I actually read this about a week ago. 23- 27 feet : two car lengths the distance the droplets travel during transmission. This MIT researcher isn't the only scientist suggesting this.

Thanks for posting this article. CDC changed this recommendation re mask wearing on Friday 04/03/20.

Very timely post.

UKGuy

Are you sure that's not a photo of the Mount St. Helens eruption?

geoff1000

The distancing can also be defeated, if people feel the need to apologise and thank for it, by shouting at each other as they pass. "THANKS FOR KEEPING A SAFE SOCIAL DISTANCE FROM ME, PLEASE ACCEPT THIS SAMPLE OF MY SALIVA TO SHOW MY GRATITUDE".

It would be rather like if a car alarm went off in the middle of the night for a few seconds, then the owner knocked on the doors of everyone in a hundred yard radius to apologise for the noise. 😀

A small wave of the hand or a thumbs-up, is probably better.

When I have to pass closer than six feet, I try to face way, even though this feels like I am subjecting the other person to a severe social rejection ; like the military college, where those who were expelled had to walk through a double line of the other pupils, who would turn to face away from them as they passed. ( I can't remember the name of the movie ).

Thanks for posting this. Unheard of information.

Lovelight

Thanks for sharing! @MrPaul

Yes @geoff1000 I'm also avoiding as much as I can to face anyone whenever I need to go out for essentials.

Though isn't this just a matter of someone coughing in one's direction? Or can someone just speaking from a distance also spread it?

geoff1000

@Lovelight
I think the Covid-19 virus particles are like any toxic chemical ; we can't avoid it completely, but our body can cope with a little at a time.

Imagine if the Normandy landings had taken place over a year. The beach defences would have coped with a few hundred invaders landing each day. The problem, or the key to success ( depending on one's point of view ) was that 160,000 troops arrived on that day.

Some illnesses are caused by the body's defences being overwhelmed, others by those defences over-reacting ( e.g. anaphylaxis ). Either way, the 'viral load' is crucial.

A cough is designed to clear the lungs and trachea ( compared to a sneeze which is designed to clear the nose ) ; and the virus is particularly effective, because it causes a body reaction, which aids the spread ( as well as having a delay, which allows the host to move to a new location ). Imagine if early stages of syphilis increased libido.

A cough therfore can carry virus particles from deep in the lungs, and project them a great distance ; but any exhalation, including vocalisation, carries particles from the airways.

Particles can remain airborne for some time, but the longer-lasting ones are smaller and hence carry less virus each.

I think social distancing and hand-washing is really a numbers game, like buying as few lottery tickets as possible, to minimise one's chances of "winning" a bad jackpot. Think of the residents of the Districts in The Hunger Games, trying to not get picked.

There is no practical strategy, to completely avoid taking in even a single virus particle ; the trick is to use as many methods as possible, to minimise the number. Most of the medical advice helps to prevent a person becoming infected, and also helps to prevent an infected person passing it on. Facing away at the point of closest approach, is just an extra step that I think we can do easily.

I remember the signs in shops requiring people to *not * have their face covered. In some countries, face covering in shops is now mandatory.

Looking away was regarded as shifty and suspicious, now it is good practice.

Strange times.

MrPaul

@geoff1000
The study linked below indicates that a single viral particle is enough to infect an organism. We do not know if this is true for COVID-19 in humans or not. We lack an immunity to this virus, our bodies cannot effectively recognize it at the moment of infection. Therefore I assume it is possible for one viral particle to infect.

https://www.sciencedaily.com/releases/2009/03/090313150254.htm

geoff1000

@MrPaul
I agree that a single particle can be enough ; like a single bullet can be instantly fatal, or a single sperm cell can cause pregnancy.

I suspect that most fatal gunshot victims, were only hit once ; and almost all pregnancies, are from a single sperm fertilising the egg.

The particle won't have time to act if it is : picked up on a hand, then washed off ; or inhaled then coughed or sneezed out. OCD hand-washers, coughing asthmatics, and sneezing hay-fever sufferers ; might be better off than most.

Some cultures celebrate by shooting firearms into the air ; and those bullets come down, almost as fast as they went up. A person would have to be very unlucky to be hit by one ; but if we were losing thousands of people a day to such accidents, the practice would probably be banned.

AceCuddlerMike

A falling bullet falls at a fraction of it's firing speed. It's something like one tenth! Hardly "almost as fast".

pmvines

@geoff1000 @AceCuddlerMike True story. There was a haunted trail and the scare actor was supposed to fire a gun with a blank, and it was a real bullet. He shot it up into the air and when it fell it hit someone and they died. Only in Alabama

geoff1000

@AceCuddlerMike
Do you have any references for that ?

AceCuddlerMike

And Kuwait. I think 20 ppl died celebrating the end of the Gulf War. They come down around 200 ft per second depending on variables like wind and the shape of the round. Still quite fast. But modern firearms fire rounds at around 2500 fps.

geoff1000

@pmvines @AceCuddlerMike

The muzzle velocity of a handgun is roughly the speed of sound ( 760 mph ), a rifle bullet is about two or three times that ( 1500 to 2500 mph ).

The terminal velocity of an object increases with density, lead is about 11.

A human being in free fall achieves about 120 mph, so a lead bullet will be much faster.

AceCuddlerMike

Like I said, a round will fall at 200-300 feet per second (136-204 miles per hour). If that's what you mean by "much" faster. Still nowhere near it's firing velocity, right?

AceCuddlerMike

@geoff1000 Actually the instructor teaching Glock and M4 certification talked about it. But since you asked I just googled and found lots of pages saying the same thing, so just do a search. Only time the falling speed would be even close to half of the firing speed would be if you're talking about old black power weapons.

AceCuddlerMike

@geoff1000 Instructor was a retired Navy Seal contracted at Camp Peary.

pmvines

Since a bullet has such a velocity I can imagine even partial velocity would be enough to injure and if hit in the right place cause death

pmvines

When I was young I was told that if you were to drop a penny off of the empire State building it would kill you

UKGuy

Dropping a penny off a tall building wouldn't kill you unless you forgot to let go of it.

pmvines

@UKGuy good point

AceCuddlerMike

@pmvines "When I was young I was told that if you were to drop a penny off of the empire State building it would kill you" Yeah but who could get down there that fast? : |

MrPaul

Keep in mind that we are talking about people sneezing and coughing out warm aerosols which experience buoyancy relative to the colder air around them. This means the tiny micro droplets do not fall immediately but can linger in the air for much longer than large droplets would.

Check out this video about the nature of a ring vortex to get an idea of just how far these particles can travel.

geoff1000

@AceCuddlerMike
OK, I'll concede.

The most usual weapon to be fired into the air, is the Kalashnikov, which is similar to a .30 cal. I probably ignored that it wouldn't be coming down point-first.

A large-calibre handgun would probably have a more similar downward speed, because : the initial velocity is lower, the round is less pointed so travelling sideways makes less difference, and the round is larger so has a greater mass / area ratio.

However, I think we are agreed that they come down fast enough to ruin someone's day.

deefine

Seriously some of this stuff just causes undue paranoia; if your immune system is good, this 99% means nothing. Probably 80% of Americans have already been infected, and probably 60% of those already have anti-bodies or will get through it without even noticing it.

I used to be a germaphobe, and when you really start thinking about how you can get infected, you will not want to touch anything, breath anything, go anywhere... it's a prison sprung from a trap.

Kids who played in the dirt have better immune systems growing up; same with breast-fed babies. It's OK to get a little bit, it's a threat if you get overwhelmed.

Focus on getting a good healthy diet, cut out excessive sugar and fat, get good exercise, some sunlight, enough vitamins, and follow the personal guidelines from the medical professionals. Stop scaring yourself with articles and videos that show how you can get just one speck of virus on you, you'll more likely die from a compromised immune system from all of the anxiety than anything else, seriously, being terrified compromises you.

AceCuddlerMike

@davebutton I'm more paranoid about possibly infecting someone old and weak.

Lovelight

@geoff1000

"..but any exhalation, including vocalisation, carries particles from the airways.

Particles can remain airborne for some time, but the longer-lasting ones are smaller and hence carry less virus each. .." That's freaky.

Thank you for the explanation and simplification! Some of it I knew, though not like others such as how it can be transmitted just from speaking.

geoff1000

The word "cough" is onomatopaeic ; saying it, is a gentle cough.

It won't bring up virus particles from deep in the lungs, or project them as fast as a regular cough ; but if you pass by someone and say, "I didn't cough at you", then you just did. 😀

Zek

Closing narrow hiking trails and tunnels makes sense, but the result of my city closing parks and beaches, where there was plenty of space to be 10ft away from people, is now the nearby streets are too crowded with runners and dog walkers. Runners still spitting, dog poop still left everywhere.