As we all see the moon which is easily visible to all the people with naked eye. It is one of the beautiful objects in earth’s night sky. By its phases it amazes the curious minds to think. It was also the reason for the development in astronomy. However, have you ever imagined why the moon doesn’t fall into the earth like other objects ? Or maybe one day it will collide with earth resulting in the end of human civilization ? So let’s find out the science of the moon orbiting the earth.
As we all know that gravity is the force responsible for objects falling into the earth and the same gravity is responsible for the motion of the moon around the earth. Yet the apple falls into the earth while the moon doesn’t fall into the earth. Does gravity also have a double standard ?
Why does an apple fall into the earth ?
An apple falls because of gravitational force between earth and the apple. The equation for gravitational force between earth and apple is given below
G- Gravitational constant
M- Mass of earth
m- Mass of apple
Since, there is a huge difference between the masses of earth and apple. Therefore, apples being lighter attracted towards earth instead of earth being attracted towards apples. This movement of the apple towards earth is seen as an apple falling into the earth.
Why doesn’t the moon fall into the earth ?
Newton did a thought experiment to answer this question, so let’s prepare to imagine.
Performing example at earth’s surface :
Let’s imagine you are at a surface of earth and throw a rock horizontally, it will go horizontally and due to gravity it will follow a curved part and will fall onto the earth.
Now, if you throw the same rock horizontally but with high velocity, the rock will follow the curved part and will fall on the surface of earth but further away as compared to earlier one.
Performing experiments at the top of tall building :
Let’s you throw a rock horizontally, it will follow a curved part and will fall onto the earth at a more distance away from you compared to the ground situation.
Now, if you throw a rock with high velocity horizontally, it will fall onto the earth at a greater distance away from you as compared to the above case.
You repeated the experiment many times with every time increasing the horizontal velocity.
At a certain velocity, you will find that the rock will try to fall onto the surface of earth but due to the spherical shape of the earth it will always miss the surface. This is termed as orbit.
Hence, the moon is always falling into the earth but luckily due to spherical shape of earth it is always missing the surface. If the moon will have more velocity then it will escape from the earth’s gravitational field but fortunately it has perfect velocity neither falling into earth nor escaping from earth’s gravitational field.