Through history, eclipses have inspired fear and curiosity, especially when total lunar eclipses turned the moon blood-red. An effect that terrified people who had no knowledge and no understanding. Let us see what a lunar eclipse is.
A lunar eclipse occurs when the Moon passes directly behind the Earth into its shadow.
So, this can appear only when the Sun, Earth and Moon are perfectly lined up like this:
Therefore, a lunar eclipse can only happen the night of a full moon.
Here are all the phase of the Moon beginning with the new moon and ending with the waning crescent.
As said before, a lunar eclipse occurs only when the Moon passes behind the Earth shadow.
But we have to notice that the shadow of the Earth can be divided into two distinctive parts: the Umbra and the Penumbra.
According to the position of the Moon, it will happen different types of lunar eclipses:
The red moon is possible because while the moon is in total shadow (umbra), the light from the sun passes through the Earth’s atmosphere and is send toward the moon.
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Some eclipse are only partial, in fact, this happens when the Sun, Earth and Moon are not quite perfectly aligned. So the Moon passes through the Earth penumbra.
For this reason, we don’t see the full moon in red but only a crescent.
When this happens, the Earth blocks some of the sun’s light from directly reaching the moon’s surface and covers a part of the moon with the penumbra. The rest receives the same amount of sunlight as usual and is as bright as a full Moon.
Lunar eclipse such a beautiful phenomenon but how to watch it?
Lunar eclipses are the easiest sky watching events to observe. We simply have to go out, look the sky and enjoy the show!
We don’t need a telescope or any other special equipment, we just have wait because a lunar eclipse can take a couple of hours to unfold.
When is the next lunar eclipse?
Here is a schedule of upcoming lunar eclipses:
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Sept. 16, 2016: Penumbral eclipse. Visible from Europe, Africa, Asia, Australia, western Pacific Ocean.
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Feb. 11, 2017: Penumbral eclipse. Visible from Americas, Europe, Africa Asia.
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August 7, 2017: Partial eclipse. Visible from Europe, Africa, Asia, Australia.
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January 31, 2018: Total eclipse. Visible from Asia, Australia, Pacific Ocean, western North America.
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July 27, 2018: Total eclipse. Visible from South America, Europe, Africa, Asia, Australia.
The last lunar eclipse was on March 23, 2016. It was a penumbral lunar eclipse.
The half of the moon shine as bright as usual while the other half is in the darkness
From the ancient time, going back to Antiquity, lunar eclipses permitted the calculation of the diameter of the Moon and the distance between the Earth and the Moon.
They used the angular diameter or apparent size to measure those things.
The angular diameter of an object is the “visual” diameter of the object measured as an angle.
With Do, the angular diameter of the Earth’s umbra and geogebra]
You can seeing the duration of a lunar eclipse who he found 2 hours
So the Moon’s diameter is determined by the Earth’s diameter which 3 Moon embody the diameter of Earth
The diameter of Moon is [12 740/3] 4246 Km
The distance Earth-Moon, we know that the Moon go around the Earth on 708 hours. Aristarchus said the eclipse lunar last 2 hours so for one hour the Moon cross 6370 Km.
During 708, the Moon travel 4 509 960Km which the circumference Earth’s orbital.
So the distance Moon-Earth is [ radius = 4 509 960 / 2π ] = 717 782 Km.