Slide 1 of 19
"There is nothing softer and weaker than water, and yet there is nothing better for attacking hard and strong things."
The Chinese sage Lao Tzu stated this paradox in his ancient text, the "Tao Te Ching." Indeed, water's ability to wash, soothe and nourish contrast with its brute power, as exhibited by Niagara Falls , the Grand Canyon (carved over time by the Colorado River) and tsunamis.
Similarly paradoxical, water is both extremely familiar making up nearly two-thirds of our own bodies and covering three-quarters of the planet and extremely mysterious. Though you know it so well, many of its properties will completely surprise you. Others are so strange that they still elude scientific understanding.
Race to the bottomSlide 2 of 19
Race to the bottom
A logical person might assume that it would take longer for hot water to plunge down the temperature scale to 32 degrees Fahrenheit (0 degrees Celsius) and freeze than would cold water. But oddly enough, this is not always the case. As was first observed by a Tanzanian high school student, Erasto Mpemba, in 1963, hot water actually freezes faster than cold water when the two bodies of water are exposed to the same subzero surroundings.
And no one knows why.
One possibility is that the Mpemba effect results from a heat circulation process called convection. In a container of water, warmer water rises to the top, pushing the colder water beneath it and creating a "hot top." Scientists speculate that convection could somehow accelerate the cooling process, allowing hotter water to freeze faster than cooler water, despite how much more mercury it has to cover to get to the freezing point.Slide 3 of 19
Slippery substanceSlide 4 of 19
A century and a half of scientific inquiry has yet to determine why ice can make you fall down. Scientists agree that a thin layer of liquid water on top of solid ice causes its slipperiness, and that a fluid's mobility makes it difficult to walk on, even if the layer is thin. But there's no consensus as to why ice, unlike most other solids, has such a layer.
Theorists have speculated that it may be the very act of slipping, or skating making contact with the ice that melts the ice's surface. Others think the fluid layer is there before the slipper or skater ever arrived, and is somehow generated by the inherent motion of surface molecules.
We know you're looking for someone or something to blame, as you lie there on the ground fuming, but unfortunately the jury is still out on this one.Slide 5 of 19
AquanautSlide 6 of 19
On Earth, boiling water creates thousands of tiny vapor bubbles. In space, on the other hand, it produces one giant undulating bubble.
Fluid dynamics are so complex that physicists didn't know what would happen to boiling water in zero-gravity conditions until the experiment was finally performed on board a space shuttle in 1992. Afterward, the physicists decided that the simpler face of boiling in space probably results from the absence of convection and buoyancy two phenomena caused by gravity. On Earth, these effects produce the turmoil we observe in our teapots.Slide 7 of 19
Levitating liquidSlide 8 of 19