President Trump spoke to reporters on board Air Force One, a day after he announced a 10% across-the-board tariff on U.S.

These cyclical ripples, also called cymatics, travel far faster than human eyes can see, so he uses ultra-high-frame-rate cameras slow them down ... inch-deep dish of water vibrated by a speaker.

You simply use a slow shutter speed, usually a half a second or longer, maybe up to as long as 30 seconds. The water in motion blurs to become as smooth as glass. The trick is getting that long ...