On 31 January 2018 night, Indonesian people can enjoy four natural phenomena at once: full moon, total lunar eclipse, blue moon and supermoon.
Here are four things to know about the rare phenomenon:
The orbit of the Moon is tilted about 5 degrees relative to the Earth's orbit. Thus, the Moon is often slightly above or below the Earth's orbit path to the Sun. But twice in one cycle, the Moon crosses our orbit
When the crossing is in line with the full moon, then the moon will go into the shadow of the Earth, producing a total lunar eclipse. Because the Moon needs to be behind the Earth, relative to the Sun, a lunar eclipse can only happen during a full moon.
To watch the eclipse, we need to be on the Earth part of the night; This eclipse will mainly be seen in Asia, Australia, North America and the Pacific.
In North America, the next lunar eclipse will be visible on January 21, 2019.
- Blue moon that looks red
When the eclipse occurs, the Moon appears darkened as it moves into the shadow of the Earth called umbra. When the moon is in the shadow, it does not completely darken; instead it looks red due to a process called Rayleigh scattering.
The gas molecules in the Earth's atmosphere propagate the blue light waves from the Sun, while the more red light waves pass right through them.
This is why we have a blue sky and a red sunrise and sunset. When the Sun is high in the sky, red light passes directly to the ground, while the blue light is propagated in different directions, making it more likely to be caught in the eye when we look around.
As the sun sets, the angle of the Sun is lower in the sky and red light passes directly into our eyes, while the blue light is scattered away from the line of sight
.