Explanation: How did this big rock end up on this strange terrain? One of the more unusual places here on Earth occurs inside DeathValley, California, USA. There a dried lakebed named Racetrack Playa exists that is almost perfectly flat, with the odd exception of some very large stones, one of which is pictured here in April of 2019 beneath a dark, Milky-Way filled sky. Now the flatness and texture of large playa like Racetrack are fascinating but not scientifically puzzling -- they are caused by mud flowing, drying, and cracking after a heavy rain. Only recently, however, has a viable scientific hypothesis been given to explain how heavy sailing stones end up near the middle of such a large flat surface. Unfortunately, as frequently happens in science, a seemingly surrealproblem ends up having a relatively mundane solution. It turns out that in winter thin ice sheets form, and winds push ice sections laden with even heavy rocks across the temporarily slick playa when sunlight melts the ice.
wolfie138 wrote: ↑Mon Apr 13, 2020 8:07 am
from those tracks, how is it they move in straight lines in the same direction each time :-/
What are the prevailing winds in California?
Winds. California lies within the zone of prevailing westerlies and on the east side of the semi-permanent high pressure area of the northeast Pacific Ocean. The basic flow in the free air above the state, therefore, is from the west or northwest during most of the year.
<<In December 1973, the crew of the cancelled Apollo 18 mission is informed that it will now proceed as a top secret Department of Defense (DoD) mission, disguised as a satellite launch. Commander Nathan Walker, Lieutenant colonel John Grey, and Captain Ben Anderson are launched toward the Moon to place detectors to alert the United States of any impending ICBM attacks from the USSR... Anderson speculates that the true intention of the ICBM warning devices is to monitor the aliens, and that the devices are the source of the interference. Anderson and Walker attempt to switch them off, only to discover they have been destroyed, with the same non-human tracks surrounding them. Walker’s wound shows signs of a developing infection, such as vein discoloration (possibly caused by necrosis), blood-shot eyes and he becomes contentious and paranoid. The mission cameras capture the rock samples moving around in the interior of Liberty, revealing that the aliens are camouflaged as Moon rocks. Increasingly delusional, Walker attempts to destroy the cameras within Liberty with a hammer, but he accidentally damages the system controls (by damaging the control panel with the hammer) causing Liberty to depressurize. Realizing the Soviet LK lander is their only source of oxygen, the pair travel to the LK lander in their Lunar rover. Walker causes the rover to crash as he runs away, believing he should not leave the Moon because of the risk of spreading the infection to Earth. As the rover crashes, the camera catches glimpses of the large space rocks, which begin to grow legs similar to that of spiders.
Anderson awakens and tracks Walker to the crater where they found the cosmonaut. Walker is pulled into the crater by the creatures. Anderson gives chase, but he is confronted by the aliens, and flees to the Soviet LK. Anderson uses its radio to contact USSR Mission Control, who connect him to the Department of Defense. The deputy secretary informs Anderson that they cannot allow him to return to Earth, admitting they are aware of the situation and incorrectly believe he is also infected. Anderson manages to contact Grey and they make arrangements for Anderson to return to Freedom. Anderson prepares the lander for launch, but Walker arrives, revealing he had survived the alien encounter earlier. However, he is now completely psychotic and demands to be let in. When Anderson refuses to let him in, he tries to break the lander's window with a hammer. Before Walker can enter the vehicle, his helmet is swarmed with rock aliens, which break the helmet open, killing Walker as his body is dragged away by a much larger alien rock.
Anderson launches, but the DoD warns Grey that Anderson is infected, and orders him to abort the rescue or communication (without which the CSM will be unable to return to Earth) will be cut off. The lander's engines shut off as it enters orbit, and it is in free fall. Small rocks within the craft float in the air, some of which reveal themselves to be rock aliens. Anderson is attacked and infected by the rock aliens, preventing him from controlling the vehicle. Grey tells Anderson that he is moving too fast as the LK speeds towards Freedom, and the space footage ends abruptly, implying the LK and Freedom collided.>>
Last edited by neufer on Mon Apr 13, 2020 12:26 pm, edited 1 time in total.
The sailing stone looks pretty fantastic. Look how many sedimentary layers it contains. It used to be a part of a large stationary mass of rock, which accumulated more and more layers of sediment over tens or hundreds of millions of years. But now it has been torn loose and spends short spurts of its existence sailing across Racetrack Playa in Death Valley, California, USA.
Nice photo! Oh wow; I left a reply to this earlier
& forgot to hit the submit button! Oh well;
all I said was that it was a strange phenomenon!
Is it exclusive to Death Valley?
Fine Art Image! That explanation came out before my first visit back in '69. Confirmation took many decades, finally arriving in the early 2000's. The photography term for this type of image is 'Light Painting'.
Based on email from James Norris, a leading authority and author on the sailing stones, the last sentence of the APOD text on the main NASA site has now been updated to read "It turns out that in winter thin floating ice sheets form in a rare ephemeral lake, and light winds push ice sections that then push even heavy rocks across the temporarily flooded playa when sunlight begins to melt the ice." We thank James and apologize for the previously less-accurate wording. - RJN
RJN wrote: ↑Wed Apr 15, 2020 4:49 pm
Based on email from James Norris, a leading authority and author on the sailing stones, the last sentence of the APOD text on the main NASA site has now been updated to read
"It turns out that in winter thin floating ice sheets form in a rare ephemeral lake, and light winds push ice sections that then push even heavy rocks across the temporarily flooded playa when sunlight begins to melt the ice."
RJN wrote: ↑Wed Apr 15, 2020 4:49 pm
Based on email from James Norris, a leading authority and author on the sailing stones, the last sentence of the APOD text on the main NASA site has now been updated to read
"It turns out that in winter thin floating ice sheets form in a rare ephemeral lake, and light winds push ice sections that then push even heavy rocks across the temporarily flooded playa when sunlight begins to melt the ice."
A Sailing Stone across Death Valley
Oh wow; I left a reply to this earlier
Oh well;
