April 5, 2011: the Old Moon in the New Moon’s arms

~ The Old Moon in the New Moon’s arms ~ Click to enlarge

Weather permitting we may be able to observe, just after sunset, the two day young Moon, a slither of light, embracing or containing the old Moon in her arms. This beautiful phenomenon is also known as ‘ashen glow’, ‘earthshine’, or ‘Da Vinci Glow’ (because Leonardo draw a picture of it). It is possible only at this time of the lunation cycle, or when the Moon is at the same relative distance from the Sun, but waning, before the New Moon.

This faint glow is actually the soft light of our own planet reflected back to us by the Moon. Amazing stuff.

Scientists observe this reflection to measure the so called ‘albedo’ of the Earth, in order to determine the global clouds cover. This is so because the oceans reflect less light than the continents, approximately 10 %, while land masses reflect from 10 to 25%, but clouds up to 50%.

These calculations are helpful to determine differences in cloud covers throughout long periods of time, used principally in measuring the effects of climate change. The overall results obtained this way are still somewhat unclear, but nevertheless important to learn more secrets about the planet we live on.

Tonight we are unlikely to see it in the Northern Rivers of New South Wales though, because it has been raining on and off for days.

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