عدد المساهمات : 37598
تاريخ التسجيل : 21/09/2009
|موضوع: NASA geologist may have found out secret behind 'sailing stones' الأربعاء 19 يونيو 2013, 3:44 pm|| |
NASA geologist may have found out secret behind 'sailing stones'
Death Valley's mysterious "sailing stones" appear to move across the desert all by themselves. The stones, found in the cracked surface of a dried up lake bed in Death Valley, California, the stones apparently glide across the sandy ground by their own volition. However - a NASA geologist in now offering his own theory on how these sentient objects are able to move.
On the barren Racetrack Player, the large rocks weighing as much as 700 pounds leave trails in the sand, marking their tracks - some of which are nearly 600 feet long.
- اقتباس :
LOS ANGELES, CA (Catholic Online): On the barren Racetrack Player, the large rocks weighing as much as 700 pounds leave trails in the sand, marking their tracks - some of which are nearly 600 feet long.
A mystery to scientists for nearly a century, NASA geologist Professor Ralph Lorenz thinks he has found the answer. A planetary scientist, Lorenz believes the rocks become encased in ice during the winter. As the lake bed thaws and becomes muddy, the ice allows the rock to "float" on the mud - sailing around thanks to the strong desert winds.
"Basically, a slab of ice forms around a rock, and the liquid level changes so that the rock gets floated out of the mud," Lorenz said in an interview with Smithsonian magazine in 2009. "It's a small floating ice sheet which happens to have a keel facing down that can dig a trail in the soft mud."
However, no scientist has been able to record the rock physically moving to date - and it's widely believed that no one has ever seen the rocks in motion.
Lorenz devised his theory after a simple experiment on his kitchen counter, after he froze a small rock in just enough water that a small amount of the stone was sticking out of the ice.
Lorenz's theory indicates the rocks could move with only a slight breeze, under the right conditions, because the ice causes them to float, reducing their friction. Lorenz then flipped the stone upside down and placed it in a small pool of water with sand on the bottom.
The ice allowed the stone to float just enough that it still touched the sand and Lorenz found he could move the rock around simple by blowing it gently.
Scientists had previously theorized that massive sheets of ice locked several rocks together and blew them through the desert. New mathematical models calculated that winds would have to be hundreds of miles an hour to push the rocks in this way.
Lorenz's theory indicates the rocks could move with only a slight breeze, as the ice causes them to float - dramatically reducing their friction.
In spite of this recent explanation, park rangers say many visitors continue to attribute mythical properties to the rocks on the Racetrack Playa. According to folk legend, aliens and mysterious energy fields move the rocks. Some of the most superstitious believe that stones have magical properties.
Many of the stones are stolen by tourists. Park rangers warn against the practice. "We've had more instances of folks taking the rocks,' Death Valley spokesman Terry Baldino told the Los Angeles Times. "They don't seem to understand that outside of the Racetrack, these marvelous rocks have no value."