Inventor and engineer Mark Rober is a pretty sharp guy. He worked for NASA, for Christ’s sake.

Photo Credit: Facebook, Mark Rober

Rober recently shared a video on his YouTube channel that you have to see to believe.

Photo Credit: YouTube

Rober demonstrates how adding air to sand in a very specific way causes the sand to look and act like a fluid. So Rober decided to fill up a hot tub with sand and give it a go. He also enlisted his nephews to help him out.

Photo Credit: YouTube

Check out the video below to see this experiment in action.

h/t: Mashable