PSA: Water

The Surprisingly Strange Physics of Water

1. 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.

2. Levitating liquid

When a drop of water lands on a surface much hotter than its boiling point, it can skitter across the surface for much longer than you’d expect. Called the Leidenfrost effect, this occurs because, when the bottom layer of the drop vaporizes, the gaseous water molecules in that layer have nowhere to escape, so their presence insulates the rest of the droplet and prevents it from touching the hot surface below. The droplet thus survives for several seconds without boiling away.

‘Huge’ water resource exists under Africa

Scientists say the notoriously dry continent of Africa is sitting on a vast reservoir of groundwater.

They argue that the total volume of water in aquifers underground is 100 times the amount found on the surface.

The team have produced the most detailed map yet of the scale and potential of this hidden resource.

Writing in the journal Environmental Research Letters, they stress that large scale drilling might not be the best way of increasing water supplies.

Across Africa more than 300 million people are said not to have access to safe drinking water.

Demand for water is set to grow markedly in coming decades due to population growth and the need for irrigation to grow crops.

Plant Sends Tweets for Water

Botanicalls Kits let plants reach out for human help! They offer a connection to your leafy pal via online Twitter status updates to your mobile phone. When your plant needs water, it will post to let you know, and send its thanks when you show it love. It comes as a kit so that you can hone your soldering skills (or teach someone else) while you build a line of communication between you and your houseplant!

This kit comes with everything you need to get your plant tweeting in no time. The ATmega328 comes pre-programmed, but you can customize it with your own messages. The only thing you need to provide is a plant, network connection (and Ethernet cable), and a power outlet.

The Water-Powered Dolphin Jetpack

This incredible water-powered jetpack lets you plow effortlessly through the water like a dolphin.

NASA Probe Data Show Evidence of Liquid Water on Icy Europa

Data from a NASA planetary mission have provided scientists evidence of what appears to be a body of liquid water, equal in volume to the North American Great Lakes, beneath the icy surface of Jupiter’s moon, Europa.

The data suggest there is significant exchange between Europa’s icy shell and the ocean beneath. This information could bolster arguments that Europa’s global subsurface ocean represents a potential habitat for life elsewhere in our solar system. The findings are published in the scientific journal Nature.

“The data opens up some compelling possibilities,” said Mary Voytek, director of NASA’s Astrobiology Program at agency headquarters in Washington. “However, scientists worldwide will want to take a close look at this analysis and review the data before we can fully appreciate the implication of these results.”

NASA’s Galileo spacecraft, launched by the space shuttle Atlantis in 1989 to Jupiter, produced numerous discoveries and provided scientists decades of data to analyze. Galileo studied Jupiter, which is the most massive planet in the solar system, and some of its many moons.

400 Trillion Miles Away, a Comet Storm Waters a World

One of the great mysteries of planetary science is how Earth got so wet. By the time our planet formed about 4.5 billion years ago, the Sun’s heat had driven most of the Solar System’s complement of water out toward the edges. Most of it is still there, frozen solid in, among other things, the rings of Saturn, Jupiter’s moon Europa, the bodies of Neptune and Uranus and billions upon billions of comets.

But the Earth has plenty of water as well, and scientists have wondered for years how it got here. One leading theory: it came from a fusillade of comets that came screaming back in toward the Sun a half-billion years or so after our planet formed. That idea got a big boost just last week with the discovery that some comets, at least, have the same chemical signature as the water found on Earth.