Saturday, June 18, 2011

Why did the Moon Turn Deep Red on Total Eclipse Day?

The longest and the darkest Lunar eclipse of the century on 15th June, 2011 was a rare phenomenon to watch and understand the wonders of light. As the eclipsed progressed and earth tried to cover and more path of Sun rays reaching its satellite moon, it turned to a stunning crimson red shade instead of blackening.

The scientific reason behind this miracle was due to composition of light rays and the property of bending of light rays called refraction. We know that white light is made up of seven colours popularly called – VIBGYOR (Violet, Indigo, Blue, Green, Yellow, Orange and Red).

When the light travels from one medium to other having different densities it tends to bend. All the seven colours have different tendency to bend. Because of this reason only when light passes through water droplets of cloud a rainbow is seen. This was first explained by Isaac Newton in the year 1660 though glass Prism.

A lunar eclipse occurs when Earth lines up directly between the sun and the moon, blocking the sun's rays and casting a shadow on the moon. Moon does not have its own light, but is illuminated by sunlight. Lunar eclipse falls on full moon day. Due to alignment of earth between Sun and Moon, shadow of earth falls on the moon and part of it gets darkened.

When total lunar eclipse occurs the change of shades of moon as it moves deeper and deeper into Earth's shadow, is first from white to gray in shadow portion and then the moon changes colour, turning from gray to an orange or deep shade of red.

During total eclipse Moon remains completely within Earth's umbral shadow and no direct sunlight reaches to it. However, indirect sunlight still manages to reach and illuminate it.

The light before entering the earth atmosphere travel though vacuum and comes to denser medium. This bends the blue coloured components more and get deviated more to central part of earth. So, Violet to Blue coloured rays do not pass through the earth. Whereas, yellow to red spectrum bends less and cross the earth atmosphere from the other end and getting straightened to the alignment as was before entering the earth’s atmosphere. As now, the light moves from denser to the rarer medium.

This is how the red light is able to reach the moon surface and make it look angry on earth for stopping the sunlight on total eclipse day.

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