What is causing this strange shimmering pattern of light during a total solar eclipse? Below this question was left a comment linking to the Smarter Every Day video Space Station Transiting 2017 ECLIPSE, My Brain Stopped Working - Smarter Every Day 175.

At about 04:30 they show a short clip of a video recording of what looks like a white bed sheet hanging vertically and a shimmering pattern of light on it, I assume related to the total solar eclipse.

What's going on? What causes this? What's it called?
These are called shadow bands.

As the sunlight is reduced to a very narrow strip, in the last few moments before totality, turbulence and refraction in the atmosphere will cause shimmering bands of light and shadow. 

What you are seeing here is essentially the same as the twinkle that you see from stars.