So we're just about ten years into the discovery that the universe is probably blowing apart due to a cosmic, anti-gravitational force called dark energy. And how much more do we know about it?

Scientists have made some headway, but there are still some frighteningly large questions to be addressed.  They now agree that dark energy makes up 75 percent of the cosmos. Dark matter, another mysterious substance, commands a 21 percent share. And as for the protons and electrons we all know and love? A mere sliver of the total, at a paltry four percent. The latest issue of the journal Physics World features reflections and insights from two of the leading dark energy astrophysicists, Eric Linder and Saul Perlmutter, of the University of California, Berkeley. They say that planned and potential space missions - like the probe pictured here - could make the next decade an exciting one for astrophysics. Who knows, maybe we'll get really lucky and understand the nature of ten or even, dare I say, twelve percent of the universe!—Gregory Mone

Make Sinking IceCost: $65Time: 2
HoursSafe | | | | |
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

Send a jolt of electric current through water—H₂O, in chemical shorthand—and each water molecule splits into its components: two parts hydrogen and one part oxygen. That process is called electrolysis.