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Why moon does not fall to Earth?

The moon does not fall to earth because of its tangential velocity. The following video explains it well.

English: Diagram of orbital motion of a satell...

The initiative http://lunarscience.nasa.gov/ask-a-scientist/ by NASA will answer all your doubts on moon.

Is the gravitational force between moon & earth are equal ?

Newton's law of universal gravitation for two ...
Newton’s law of universal gravitation for two bodies. This law governs gravitational forces in the Earth. (Photo credit: Wikipedia)

Is the gravitational force between moon & earth are equal ?

If the question is- “Is the force exerted by earth on moon is equal to the force exerted by moon on earth?” then the answer is “Yes

I hope that more questions will follow.

Please post your questions as comments to this post.

  • Comparison of charge and mass

Why does the sun appear to rise and set though it is actually not moving?

Why does the sun appear to rise and set though it is actually not moving?

Shivangi asks


English: Animated image of Earth rotating.

First of all I would like to remind you that it is incorrect to say that “sun is not moving”. Sun is also moving. But the question here is, “Sun appears to rise and set not because of its motion”.

Sunset and sunrise are caused by the rotation of earth. When earth rotates, the position of sun appears to change and it seems as if the sun is revolving around the earth; just like we feel that the ground is revolving around us when we are looking out from a rotating merry-go-round.

Parallax Method

Can you please explain about paralax method?

How to use it to calculate the distance between two astronomical objects?

Asked Shivangi


Parallax  is the change in the apparent position of an object due to change iv view point.

Read more here

The parallax method is a way of measuring distances of far-away objects.

Read more: http://wiki.answers.com/Q/What_is_the_parallax_method#ixzz21XoSSONi

Parallax Method to determine the distance of stars



Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines.

Astronomers use the principle of parallax to measure distances to celestial objects including to the Moon, the Sun, and to stars beyond the Solar System.

See the animation below to understand the parallax method for determining the stellar distances

Find more information here



Aswin Ramesh Asked (via email)
is it the same method that we use in trigonometry ?
Parallax is a different concept, though we are using the principle of trigonometry to solve problems based on it.

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