Why do astronomers use scientific notation to describe sizes?

1 Answer
Mar 10, 2018

Please see below.

Explanation:

Astronomers use scientific notation to describe sizes as sizes very a lot. For example, distance to moon is 385,000 kilometers, but distance to Sun is about 150,000,000 kilometers (this is known as AU - Astronomic Unit of distance) and average distance of Neptune, farthest planet is 30 AU or 4,500,000,000 kilometers and it may take just around 4 hours for light to reach Neptune.

Now compare it with the nearest star Proxima Centauri, which is at a distance of four light-years and as in one year there are about 8766 hours, the distance to Proxima Centauri is about 8766 times the one to Neptune or in kilometers it will be

150000000×30×8766=39447000000000 kilometers.

This is still very small as compared to size of universe. For example, the bulge at the center of milky way is about 12000 light years or 3000 times distance to Proxima Centauri.

Further the observable universe spans some 93 billion light-years in diameter, as it is still expanding i.e.

about 93,000,000,000×9861750000000

= 917142750000000000000000 kilometers

A similar scale may apply to volumes, mass and number of stellar objects. It is for these reasons that astronomers use scientific notation to describe sizes.