The researchers, who have recently published the findings in Physical Review Letters, have confirmed how this phenomenon occurs in granular fluids, that is, those composed of particles that are very small and interact among those that lose part of their kinetic energy. Thanks to this theoretical characterization, “we can simulate on a computer and make analytical calculations to know how and when the Mpemba effect will occur,” said Antonio Lasanta. Lasanta is from the UC3M Gregorio Millán Barbany University Institute for Modeling and Simulation on Fluid Dynamics, Nanoscience and Industrial Mathematics. “In fact,” he said, “we find not only that the hottest can cool faster but also the opposite effect: the coldest can heat faster, which would be called the inverse Mpemba effect.”

The fact that preheated liquids freeze faster than those that are already cold was observed for the first time by Aristotle in the 4th century AD. Francis Bacon, the father of scientific empiricism, and René Descartes, the French philosopher, were also interested in the phenomenon, which became a theory when, in 1960, a Tanzanian student named Erasto Mpemba explained to his teacher in a class that the hottest mixture of ice cream froze faster than the cold one. This anecdote inspired a technical document about the subject, and the effect began to be analyzed in educational and science magazines. However, its causes and effects have hardly been studied until now. Read more

The first thing you should do if you’re stranded in the wild is find a source of drinkable water. The most obvious sources are streams, rivers and lakes. Animals always know where the water is, so be on the lookout for wildlife or animal tracks. Lush green vegetation is also a sign that water is nearby. Swarming insects may be a hassle, but they also signal that a water source isn’t far away.

Bird flight paths in the morning or evening can point you in the right direction. Stay on the move until you find a water source. When you pause to rest, use your ears — rivers can be heard in the quiet woods from great distances. Remember that water always flows downhill, so low-lying areas and valleys are a good bet.

If you find a muddy area, there may be groundwater available. Dig a hole about a foot deep and one foot in diameter and wait. You may be surprised to find that the hole is soon filled with water. This groundwater will be muddy, but straining it through some cloth will clean it up, and it will get you by in the short term. It’s crucial to remember that any time you drink found water without purifying it, you’re taking a risk. Read more

Getting lost or stranded in the wild is something that could happen to just about anyone. Day hikers, tourists, Sunday drivers and experienced outdoorsmen are all subject to circumstances beyond their control. Any and all of them could end up alone and lost, with only their wits to rely on for survival. The single most important thing you need to live is water. If you’re resourceful and know where to look, you can find or collect good drinking water in just about any environment on Earth.

It’s best to get water from fast-moving sources like this river.

To maintain good health, the human body needs a minimum of two quarts of water per day [source: Field Manual 21-76-1]. If you’re lost in the wild, chances are you’ll be exerting yourself, and you may be in a hot or cold environment. Both of these factors mean you should drink more than the min­imum amount. It’s easy to think that a cold environment might pose less of a risk, but that’s not the case. You may perspire less, but you lose water through your skin because of the dry air. You should also drink more water if you’re in heavy winds. Read more

Water which has been contaminated with mercury and other toxic heavy metals is a major cause of environmental damage and health problems worldwide. Now, researchers from Chalmers University of Technology, Sweden, present a totally new way to clean contaminated water, through an electrochemical process. The results are published in the scientific journal Nature Communications.

“Our results have really exceeded the expectations we had when we started with the technique,” says the research leader Björn Wickman, from Chalmers’ Department of Physics. “Our new method makes it possible to reduce the mercury content in a liquid by more than 99%. This can bring the water well within the margins for safe human consumption.”

According to the World Health Organisation (WHO), mercury is one the most harmful substances for human health. It can influence the nervous system, the development of the brain, and more. It is particularly harmful for children and can also be transmitted from a mother to a child during pregnancy. Furthermore, mercury spreads very easily through nature, and can enter the food chain. Freshwater fish, for example, often contain high levels of mercury. Read more

When it comes to astronomy, the good old days aren’t so old. We’ve been studying the heavens for centuries, but our technology is still getting better. While we only discovered an exoplanet (that is, a planet not supported by our solar system) for the first time in 1992, scientists were pretty darn quick to figure out ways to determine the composition of some of Earth’s far-distant cousins.

Glowing a dark magenta, the exoplanet GJ 504b — illustrated here with an artist’s depiction — weighs in at about four times Jupiter’s mass.

Back in the day, we could only determine whether a planet had water by watching it pass in front of its host star during orbit, or by collecting imaging data from planets far enough away from their host stars. That worked reasonably well, but (luckily for us) there were too many cool planets to explore that just didn’t fit that specific description.

What we really needed was a way of looking at planets — outside of super-specific time periods and parameters — that would give us the same concept of what a planet’s atmosphere consisted of, and whether water was a part of it. But how do we get a good look at the light of a planet or star when we can’t track its transit? We look at the non-visible light it emits in the infrared spectrum. That information can then be compared to modeling data to gather all kinds of information about the planet.

Let’s take the planet Tau Boötis b as an example. Found in 1996, Tau Boötis b was the first planet found not by watching its transit (it doesn’t pass in front of its star), but by noticing it exerted a bit of a pull on its star. Using this new spectroscopic technique, scientists were able to confirm its orbit. Read more