On July 27-28, 2018, several countries in the world, including India, witnessed a lunar eclipse that, including its partial formations and phases, lasted 6 hours and 14 minutes; the full lunar eclipse could be seen for 1 hour and 43 minutes. It was the longest lunar eclipse for the century. The eclipse lasted long because of the Moon being farthest from the Earth at this time. The Moon passed through the centre of the Earth’s shadow, at the shadow’s widest point.
For a lunar eclipse to occur, the Earth needs to pass between the Sun and the Moon. In a total lunar eclipse, the three celestial bodies are lined up perfectly.
The Blood Moon can be seen only during a total lunar eclipse.
During an eclipse of the Moon, which only reflects sunlight and does not have light of its own, the Earth, being between the Sun and the Moon, blocks the sunlight from falling on the Moon. However, not all light is blocked, as Earth’s atmosphere allows the refraction of light; this refracted light does get through to the Moon. But the refracted light gives a reddish colour to the Moon. This is because Earth’s atmosphere, acting like a prism, allows only the red to pass through to the Moon, while the rest of the light gets scattered; and this is because red has the highest wavelength in the spectrum.
The Earth’s atmospheric conditions determine how red the Moon appears: the clearer the atmosphere, the brighter and lighter the red shade of the Blood Moon.
What if the Earth had no atmosphere? Then there would be no Blood Moon as the Moon would appear black. However, there may be no one on Earth to see it, for our lives depend on the atmosphere of the Earth.
When a similar event occurred in January 2018, the Moon appeared huge so that it was called Super Moon. In July, however, the size of the Moon was smaller. While in January the Moon was close to the Earth, in July the Moon was at the farthest distance from the Earth – that is, in apogee. So this time around, the Blood Moon is a Micro Blood Moon. Besides, Mars appeared to the right of the Moon during the eclipse as a small red spot. (Every two years or so, the Earth overtakes Mars on the inside as it moves around the Sun, so Mars comes close to Earth, especially due to the elliptical shape of the orbit.) Sky watchers could also see Jupiter, Venus and Saturn. Incidentally, there is no need to protect the eye watching a lunar eclipse, and powerful binoculars would give a good view.