I was browsing through the Hubble Space Telescope site today and came across many beautiful images of astronomical objects taken with the space telescope.
Among them were the two galaxies displayed in this post.
The one at rightis M 101. It is a spiral galaxy that is about 25 Million Light Years away.


A light year is the distance that light travels in one year, so the pictures show the galaxies as they were 25 and 70 million years ago respectively. The distance of a light year can be easily calculated by multiplying seconds in a minute X minutes in a hour X hours in a day X days in a year X distance light travels in one second. As light travels very close to 300,000 Kms in a second the calculation becomes 60 X 60 X 24 X 365 X 300,000. The answer is 9,460,000,000,000 Kms.
That means that M 101 is 236,000,000,000,000,000,000 Kms away and NGC 1300, 66,20,00,000,000,000,000,000 Kms away. These are large distances in anyone's estimation - except maybe for astronomers. Compared to the most distant galaxies known M 101 and NGC 1300 are just in our back yard. The most distant galaxies are of the order of 13 billion light years distant from us. I won't even bother with the kilometer distance which would be meaningless and silly. Galaxies much older than 13 billion years old are unlikely to be found as the universe is about 13.7 billion years old.
This post raises many questions, in particular, how are astronomical distances measured and how do we know that the universe is about 13.7 billion years old? They are obvious topics for later posts.
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