As you know, Planet Earth is part of a galaxy called the Milky Way. Our Sun is a star, one of many stars in the visible universe. The sun burns at a temperature of 5800 degrees on the Kelvin scale, emitting radiation on a very broad spectrum of “colors.” This radiation spreads in straight lines in every direction and it is one of the main reasons for life on Earth. The distance of Earth from the Sun allows for decreased radiation infiltration thus creating excellent conditions for life.
Earth rotates around the sun. It is the third planet from the Sun, after Mercury and Venus. Its orbital rotation time is close to 365 days (1 earth year). Its orbit is elliptical, so the distance of Earth from the Sun varies during the year.
The moon, a part of earth that was detached from it due to a collision with a celestial object some 4.5 billion years ago, also moves in an elliptical orbit. The moon’s distance from Earth is very small when compared to other moons in our solar system. For example, the orbital radius of “Europe”, one of the moons of Jupiter, is almost twice the rotation radius of our moon. The lunar rotation time around Earth is approximately 27.3 days
As humans living in a three-dimensional world, we see and interpret what is around us whereby close objects seem larger than distant objects of the same size. Similarly, very distant objects will appear smaller to us in relation to their environment. This concept is called “angular size”- simply put, it is a measure of how much of the field of view the object covers.
For example, despite the enormous size of the sun, and the relatively small size of the moon, the angular size may seem similar for a Earth skywatcher, this is of course due to the moon’s proximity to Earth and the sun’s greater distance.
For cosmological historical reasons, the axis of the orbits of the Earth around the sun, the moon around Earth and earth’s rotation around itself (24 hours) are very similar. Readers who have previously read the “Red Moon” article will remember that I mentioned situations in which Earth, the moon and the sun share one axis
In such situations, if the moon is in the middle between Earth and the Sun, a solar eclipse can sometimes occur. For Earth bound skywatchers, if the “angular size” of the moon is equal to or greater than that of the sun, all the rays of sunlight coming towards the viewers are blocked by the moon and they cannot see the sun.
In the last few days, in the morning of June 21st 2020, a partial solar eclipse occurred. In some areas of India, a partial ring eclipse could be seen. In this situation the Earth, the moon and the sun are on one straight line. But at this time of year the angular size of the moon is relatively small, so the sunlight does reach the viewer’s eyes around the circumference of the moon. The image created in this type of scenario is a bright picture of the sun with a huge dark shadow in its center, because the moon is blocking it – looking strikingly like a golden ring of fire. In other parts of the world, the viewers’ position in relation to the phenomenon did not show a perfect ring rather the moon only partially blocked the sun- this is called a partial solar eclipse.
