If you’ve ever whacked the bottom of a ketchup bottle to get that tasty tomato goop flowing, you’ve put some serious physics to work. Ketchup is a non-Newtonian fluid. So are toothpaste, yogurt, ...

From ketchup to quicksand, non-Newtonian fluids have long fascinated and puzzled scientists. Unlike ordinary fluids, their flow properties change depending on how much force is applied, but the ...

The knife easily leaves swirls in the spread. rimglow/iStock via Getty Images Plus Those Transportation Security Administration requirements are drilled into every frequent flyer’s head: You can carry ...