Physicists have worked out how to pour water as quietly as possible

The key to pouring water very quietly from a teapot is not just holding the spout close to the cup, but creating a perfectly smooth stream of liquid.

Mouad Boudina at Seoul National University in South Korea drinks tea every morning. Repeatedly pouring tea into a cup from a traditional teapot from his hometown in Morocco made him wonder what makes this process noisy. To find out, he and his colleagues experimented with pouring water in the lab.

They filled an acrylic cylinder with…