This Old Photo Technique Shows How Masks Help Prevent the Spread of COVID-19

Advanced imaging company LaVision has released a new video that shows just how effective a face mask can be at preventing the spread of infections like COVID-19. The video lends visual support to the CDC's recent recommendation that everyone wear a mask in any situation where it is difficult to maintain social distance.

See Airflow on Camera in This Awesome Harvard Demonstration of Schlieren Optics

Schlieren flow visualization and photography is one of those things that is just too cool. Using an optical trick, it allows a camera to capture, "small changes in the index of refraction in air." In other words, it can see anything that affects airflow: heat, sound waves, or just plain old air currents themselves.

And the video above, uploaded at the beginning of this year by the Harvard Natural Sciences Lecture Demonstrations YouTube channel, is one of the most fascinating demonstrations of Schlieren optics we've ever seen.