Moon's shadow, like a ship, creates waves

Moon

During a solar eclipse, the Moon's passage overhead blocks out the majority of the Sun's light and casts a wide swath of the Earth into darkness. The land under the Moon's shadow receives less incoming energy than the surrounding regions, causing it to cool.

In the early 1970s, researches proposed that this temperature difference could set off slow-moving waves in the . They hypothesized that the waves, moving more slowly than the travelling temperature disparity from which they spawned, would pile up along the leading edge of the Moon's path -- like slow-moving waves breaking on a ship's bow. The dynamic was shown theoretically and in early , but it was not until a on 22 July 2009 that researchers were able to observe the behavior.

Using a dense network of ground-based receivers, Liu et al. tracked the influence of the 2009 eclipse as it passed over Taiwan and Japan. The researchers looked for changes in the total electron content in the ionosphere and find with periods between 3 and 5 minutes traveling around 100 meters per second (328 feet per second) that originated from the leading and trailing edges of the shadow, analogous to bow waves and stern wake common in maritime activity.

They find that there was a 30 minute time difference between the arrival of the bow and stern waves suggesting that, were the Moon's shadow a ship, it would be 1,712 kilometers (1,064 miles) long. The researchers indicate that this would correspond to the part of the Moon's shadow that produced at least an 80 percent obscuration of the Sun's light.


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More information: Geophysical Research Letters, doi:10.1029/2011GL048805 , 2011
Citation: Moon's shadow, like a ship, creates waves (2011, October 5) retrieved 20 August 2019 from https://phys.org/news/2011-10-moon-shadow-ship.html
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Oct 05, 2011
This seems to provide some circumstancial support to the notion that "some" of what we call "gravity" may actually be a repulsive force in the form of radiation pressure, as clearly this is a Mass Shadow effect, causing the wave due to a combination of changes most importantly in thermal energy absorbed by the water from radiation, but also a direct change in radiation pressure due to the Moon's "Mass Shadow".

Radiation Pressure from the Sun produces a net "thrust" on the Earth which is roughly equal to the Solar Constant, seeing as how Earth radiates heat away roughly symetrically in all directions as infrared. But the initial EM comes in from the direction of the Sun almost exclusive, ignoring stars for the moment.

So it is natural that the Moon would block an amount of radiation pressure equal to the fraction of the Solar Constant under its shadow (minus any neutrinos or exotic radiation that passes all the way through the moon...)

Oct 05, 2011
what we call "gravity" may actually be a repulsive force in the form of radiation pressure
You're extrapolating the above observation a bit too much, IMO - but this is basically, what the ancient de Duillier-LeSage theory of gravity is about. There are another experiments, which indicate the Moon shadow can affect the gravity at the Earth.
http://en.wikiped...s_effect
I consider them a sort of neutrino flux shielding.

Oct 06, 2011
Cat Stevens released Moonshadow in 1971, coincidence? I think not! http://www.songfa...p?id=288

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