There are great things to come in the future, jet cars and all that. But the past held a few wonders too—for example, jars of mercury available at the corner apothecary. Just 50 years ago, people treated the shiny
liquid metal like a toy. Sadly, I’ll never experience the strange sensation of sticking my entire arm into a barrel of mercury, as kids once did during factory tours. Today mercury is considered a horrific poison, so bad that schools are evacuated for
a broken thermometer.

Make Sinking Ice

Cost: $65
Time: 2
Hours
Safe | | | | |
Risky

Want a surefire bet for your next cocktail party? First, tell your guests
that aquatic life—at least in temperate
climates—depends largely on the fact
that ice floats. If it sank, lakes would freeze solid instead of forming an
insulating layer of ice on top, killing all the fish. Now bet that you can
magically make an ice cube sink. Grab one from a glass of special cubes