Quandaries and Queries


Hi: My question is an astronomy one:

ANDROMEDA Galaxy is 2,500 light years away. A light year is 6 trillion miles. What is 2,500 X 6 trillion miles in a mathematical number?

Thank you




Hi Roly,

One light year is approximately 5,900,000,000,000 miles and the Andromeda Galaxy is approximately 2,500 light years away, so that is

5,900,000,000,000 2,500 = 15,000,000,000,000,000 miles

(I rounded to two significant figures.)

I think you are looking for a name for this number. Since you used the term trillion for 6,000,000,000,000 I assume you are using the American system of naming numbers. In this case 15,000,000,000,000,000 is 15 quadrillion. You can see the difference between the American system and the British system in our note called Billions and more!



In June 2022 Roma sent us this note.

Your distance to Andromeda is incorrect.  Andromeda is approximately 2.5 million light years from Earth. So it would be 2.5 million x 5.9 trillion.

Roman is correct. When Penny responded to this question she didn't check to see if Roly's stated distance to Andromeda was correct. The correct distance is

5,900,000,000,000 2,500,000 = 15,000,000,000,000,000,000 miles

or 15 quintillion miles.

Thanks Roman,