Sweeping sands across the Sahara and other dune expanses are blown by more than just wind, scientists have discovered. Powerful electric fields spring up near the desert floor and propel sand grains into the air. By accounting for this electricity, researchers say they can design better climate change models, and even explain features of the dust on Mars.Scientists have long been at a loss to explain why sand sweeping across the desert doesn't bounce higher when the wind gets stronger. But when researchers at the University of Michigan made the first calculations ofelectricity's role in this dance of particles, they were finally able to match their models with observations.As wind forces sand to scrape over Earth's surface in a process called saltation, the friction causes the sand particles to pick up loose electrons from the ground, giving them a negative charge and leaving the surface with a positive charge, the researchers found. "It's sort of like when you stroke your cat and feel little sparks, or run a balloon on your head to make your hair stand up," said Jasper Kok, a graduate student in applied physics at the University of Michigan, who led the study with his advisor, Michigan atmospheric scientist Nilton Renno.
The research will be published in the January 11 issue of the journal, Physical Review Letters.
The separation ofcharges
creates an electric field that can reach strengths of 100,000 to
200,000 volts per meter at a centimeter from the surface.
This field in
turn draws even more sand up into the air because the positively
charged ground particles are attracted to the floating negative ones.
The electric field also explains why the skipping particles do not reach greater heights when the wind blows faster.
"Now we think that as the
wind speed increases, so does the electricity, and they sort of cancel
each other out," Kok said. "The bouncing sand is electrically attracted
to the surface. We were very excited when we plotted that graph and it
all matched up."
Saltation is the force that forms sand dunes, sculpts rocks and causes erosion.
A sliver of four-billion-year-old sea floor has offered a glimpse into the inner workings of an adolescent Earth. The baked and twisted rocks, now part of Greenland, show the earliest evidence of plate tectonics, colossal movements of the planet's outer shell. Until now, researchers were unable to say when the process, which explains how oceans and continents form, began. The unique find, described in the journal Science, shows the movements started soon after the planet formed. &quo...Climate change and phenomena
Anthony North: We are facing dangers, today, from global warming. This essay is not going to argue whether this is man-made or a natural cycle as such, but is to suggest another avenue of research – into the relationship between climate and paranormal experience.Many researchers, including myself, have suggested that an environment can have an effect upon the mind. But does the present climate change offer a possibility of testing the hypothesis in action?Gaia: The idea that the Earth is a form ...Study explains rainforest similarities
Celebrated in Buddhist temples and cultivated for its wood and cottony fibers, the kapok tree now is upsetting an idea that biologists have clung to for decades: the notion that African and South American rainforests are similar because the continents were connected 96 million years ago. Research by University of Michigan evolutionary ecologist Christopher Dick and colleagues shows that kapok---and perhaps other rainforest--trees colonized Africa after the continents split when the trees' se...Did comets cause killer cold spell ?
Tiny diamonds sprinkled across North America suggest a "swarm" of comets hit the Earth around 13,000 years ago, kicking up enough disruption to send the planet into a cold spell and drive mammoths and other creatures into extinction, scientists reported on Friday.They suggest an event that wouldtranscend anything Biblical -- a series of blinding explosions in the atmosphere equivalent to thousands of atomic bombs, the researchers said.The so-called nanodiamonds are made underhigh-temperature, hi...Ancient tsunami 'hit New York'
A huge wave crashed into the New York City region 2,300 years ago, dumping sediment and shells across Long Island and New Jersey and casting wood debris far up the Hudson River. The scenario, proposed by scientists, is undergoing further examination to verify radiocarbon dates and to rule out other causes of the upheaval. Sedimentary deposits from more than 20 cores in New York and New Jersey indicate that some sort of violent force swept the Northeast coastal region in 300BC. It may ...Prehistoric jungles laughed at global warming
Evidence has been found to suggest that giant creatures such as the massive one-tonne titanoboa snake would have thrived in hot jungles millions of years ago with temperatures significantlywarmer than those seen today."Fossil boffins say that dense triple-canopyrainforests, home among other things to gigantic one-tonne boa constrictors, flourished millions of years ago in temperatures 3-5°C warmer than those seen today - as hot...Massive ice chunks break up in Antarctica
An ice shelf in western Antarctica is breaking up with huge ice chunks crumbling away and an area over 1300 square miles in danger of breaking off completely in the next few weeks."Massive ice chunks are crumbling away from a shelf inthe western Antarctic Peninsula, researchers said Wednesday, warning that 1,300 square miles of ice - an area larger than Rhode Island - was in danger of breaking off in coming weeks. . "...Prepare for another ten scorching years
Temperature records will be repeatedly shattered over the next few years, say researchers behind the first rigorous look at how global climate will change during the next decade. The prediction comes from an innovative technique that combines the approaches used by weather forecasters, who typically look a few days ahead, and climate modellers, who produce projections that run up to the end of the century. The result is a model that can project as far as 2015, filling in a long-standing gap in c... Animal Language
One of the ways most animals communicate is with sound, they may neigh, bark,
purr or quack; we speak. These auditory messages convey
meaning for the species concerned. We understand words,
horses understand neighs, dogs understand barks and so on.
Quacks don?t correspond with words, neighs
mean little to cats, but what is universal is body language.
Animals can understand the body language of their species and of others.
They usually recognize a...Global warming could change Earths tilt
It is thought that global warming could cause the Earth"s axis to tilt significantly within the next hundred years, with the rebound from melting ice sheets and the rise in sea levels both contributing to changes in the planet"s tilt."Warming oceans could cause Earth"s axis to tilt in the comingcentury, a new study suggests. . The effect was previously thought to be negligible, but researchers now say the shift will be lar...