Imagine a day, you come out of home and see a big rock (immovable by normal humans) lying on your way. And no body knows how it came there. And apparently, it sailed its own way at your doorsteps.
Sounds creepy. But there are some rocks known to move on their own. These rocks are as heavy as 300 kgs and they may cover a distance of upto 250 meters.
These rocks are found in the Mojave desert of California where the temperature goes upto 57 C on a hot day. In this desert, there is a plain surrounded from all sides by mountains. In this plain, the temperature in the night may go down to sub zero. And this is the key behind the movement of the stones.
Scientists have been trying to understand the mechanism behind the movement of these stones since 1948 when it was first observed. And it took so many years, when just last month, the work of Dr. Lorenz of Hopkins University revealed the mechanism behind this movement.
Apparently after the rain what ever water is remaining on the surface of the soil, it freezes to ice under sub-zero conditions. If this ice is surrounding a stone, then it will be responsible for the movement of the stone. When wind breeze moves over the ice, this ice partially melts and a motion in the direction of the wind is initiated. The friction offered by the surface of the soil is relatively less as compared to the push by the ice layer covering the stone. As a result, the stone is compelled to move in the direction of wind.
Thus, a suitable combination of water on the surface around the stone, a sub zero temperature condition, a slight wind breeze makes it possible for a heavy stone of ~ 300 kgs to move with out any human intervention.
This is an interesting observation solving a mystery revolving around scientists mind for over 70 years.
You may read a lot more in details about sailing stones here and about the answer to the mystery here.
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