In spite of evidence to the contrary, many people persist in the false belief that masks do not work, or that respiratory viruses are somehow not airborne. The Physics of aerosols is conceptually simple though mathematically complex. It’s also within the realm of what an undergraduate student in Physics, Chemistry, or Engineering would encounter along the way to a university degree.
Go get (or at least imagine) three spray bottles of different size. Spray their contents at a paper towel, a coffee filter, and tissue paper. What did you see? For the most part, you saw different sizes of mist and droplets that with few exceptions failed to make it through the barrier of choice. This is one of several physical processes that the aerosols too small to see go through when interacting with mask materials. You should also turn a faucet on super low until you get a thin stream of water. Build up some static charge on a comb or balloon rubbed on your hair and hold it near the water stream and watch the water stream change its path. These observations demonstrate some of the Physics that underly why masks and filter materials MUST work to mitigate aerosol emissions from any source, including people. I blab about it a bit more here.
This video explains the Physics in a bit more detail without breaking the brain, whereas this one shows how the aerosols that we exhale behave in masked versus non-masked scenarios.
BTW … these “prove” that masks MUST work.
Mathematics is an effective representational system for describing physical laws. It is a language that lets us predict with accuracy how forces and interactions produce various effects like motion. It gets complicated very fast and few people manage to endure the brutal process of formal university-level training in the disciplines that equip a person to use such tools with proficiency. The following list of laws/formulas are what you need to accurately predict the motion of aerosols — the ones you see and do not see. The parenthetical remarks are painfully oversimplified for the sake of brevity).
- Stoke’s Law (how objects move in fluids)
- Navier-Stokes Equations (the 3D partial differential equation version of Stoke’s Law)
- Drag Force (how size and shape and fluid properties affect motion)
- Reynold’s Number (describes turbulent/non laminar fluid flow)
- Diffusivity (binary in this case, relating temperature and pressure conditions to flow)
- Settling Velocity (all of the above piled into a measure of particle/aerosol speed)
- Knudsen Number (molecular motion vs. macroscopic motion)
- Mean Free Path (average distance between collisions)
- Slip Correction (based on which one of 3 regimes of particle motion is active)
- Cunningham Correction Factor (drag adjustment for slip correction)
There are also some electrical forces at play, but I thought I’d stop the list at 10 items for the sake of brevity, again.
On Being Intellectually Honest With Yourself
Right now, in hundreds of labs across the nation/world, there are scientists with labs set up to measure these things in particular. Some of them have been doing that research for most/all of your lifetime. Thousands of students majoring in Physics, Chemistry, and Engineering have taken their courses and even obtained graduate degrees under the supervision of these scientists who publish their findings in peer-reviewed journals. It requires a level of expertise that almost no one bothers to endure. Maybe 5% of us have enough formal training to tolerate the mathematics described above. That means that the vast majority of people on the planet today have no business challenging the findings of scientists in any field. It’s simply intellectually dishonest. Morally irresponsible skepticism at its worst. Don’t do that.
What about medical doctors? First, MD’s are not scientists. They do not practice Science. They are practitioners of specialities within Medicine. Second, Medicine exists because of sciences like Virology and Immunology. Third, medical advances depend on progress in Materials Science Engineering, Electrical Engineering, etc. that would not even exist apart from the Natural Sciences like Physics and Chemistry and Biology. Trust MD’s to do what MD’s know how to do, which has nothing to do with how or why masks work, but they have demonstrated for longer than most of us have been alive that masks do not harm you. How that’s not obvious is truly befuddling.
What about peer review? Can you trust it? Yes, mostly. Is it perfect? No. Can you name any human process that is? No. Is it better than your opinion? Yes, definitely. Head and shoulders better than your non-expert opinion on anything. Peer review in the natural sciences is brutal. It is largely immune to fraud because the methods are so demanding, but when you have millions of scientists worldwide publishing before perishing you are bound to have attempts at fraud. This is a human problem rather than a scientific problem. However, as a group, scientists are insatiably skeptical and eager to prove that you are wrong, which is why fraud is so easily and quickly exposed. Scientists are looking for the truth and resent fraud with extreme prejudice. It belittles the work of Science and besmirches the character of the craft. It is personal for them.
If you think that scientists are at work trying to deceive you then you are thinking foolishly. Some would call it blithering idiocy. You might be an otherwise smart person, but on this you are acting like a moron. Stop it!
Does that offend you? Note that I didn’t actually call you a name, but rather described poor patterns of thought. I’m not trying to offend you for the sake of being mean, but I am offended by people like you who persist in besmirching and discounting things that you have no knowledge of. Think about the offense that your belligerent ignorance projects onto the character and content of professional scientific disciplines.NOTE: I do apologize for offense here, but I am desperate to rattle the echo chamber cage of unfounded disbelief in all things scientific. It makes no sense why people with no knowledge of ________ persist in acting as though they have expert knowledge of _______. Suddenly, across the nation, the parents who were lost helping their 6th grader do math are suddenly infectious disease experts? Wut?
Morally responsible skepticism? If you are going to hold a viewpoint that stands in opposition to Science in general or a discipline therein in particular, then the ONLY intellectually honest thing to do is have the requisite skill to challenge the consensus view. Part of that skill set includes the ability to even understand the facts that obtain from Science. For example, that list of 10 mathematically complex features of aerosol motion. If you had to Google those things to get a clue, then you should almost certainly shut your mouth in opposition to aerosol science, masking, etc. You are being dishonest with yourself and spreading misinformation to others by spreading your uninformed opinions. In other words, you are dangerous to other people.
Follows the Science.
If you are able to DO the Science, then feel free to lead it.
Otherwise, take a seat and take notes.