essays recommendations

Excellent news and a reading recommendation

For years, I read the absolutely amazing ‘Do the Math’ blog by Tom Murphy, a UCSD physicist carefully explaining so! many! things! (Energy: generation, storage, usage, loss. Details of his lead-acid solar/battery home setup. So much more)

Now the good news – his dormant blog tells us that he’s written a textbook based on on that work, and even better its been vetted and revised and best yet? Free online and inexpensive if you want a print copy. I cannot recommend this enough.


Six feet is the wrong model

A friend sent me this paper on – “A physicist view of the airborne infection” by Luis A. Anchordoqui and Eugene M. Chudnovsky. They used SimScale to model airflow in an office and included a couple of nice visualizations:

The paper is quite concise and worth your time, just under 2.5 pages. Short version? Six feet ain’t enough and your office is a Petri dish.

From the physics point of view, we cannot find a good justification for a stationary 6-feet separation in a situation when people spend long time together in a room. Droplets containing the virus move in the air via convection. The convection pattern in a room can be very complex; see Fig. 1. It depends on the location of air conditioners, radiators, windows, and all items in the room, as well as on people producing vortices by moving around. The existing vortices in the air can make a location far away from the source of droplets more dangerous than the location 6 feet away. This applies to meeting rooms, office spaces, supermarkets, department stores, etc. The airflow pattern should be studied for all such facilities to avoid the spread of infection to large distances from a single infected person. The safest rooms must be those equipped with the air sucking ventilator at the top, like hospital surgery rooms

Luis A. Anchordoqui and Eugene M. Chudnovsky