Many of the numbers we use in science have never been measured directly; we only know them from indirect measurements. How far is it to the sun? What is the diameter of Saturn’s rings? You can use nonstandard measurements and simple ratios for estimating sizes or distances.
Though you can’t see infrared radiation light with your eyes, you can focus it with a mirror or a lens and feel the warmth it produces. Try this Snack and you'll also learn how parabolic shapes concentrate energy.
When you push the plunger on a syringe, water is forced into a second syringe, extending its plunger and lifting a mechanical arm. The process illustrates aspects of fluid pressure, force, mechanical work, and biomechanics.
If you see a straight rod and a curved slot, common sense says the rod can't possibly fit through the slot. But if the rod is angled and rotated through space and the slot is the exact right shape, it will pass through.