Question

1. How can one estimate the number of galaxies in the observable Universe? Why is this only an estimate and which information is required to improve it?

Answer 1

The number of galaxies is estimated by the following method -

A portion of the sky is chosen randomly and imaged using a telescope and the number of galaxies is determined in that particular portion. This number is then estimated for the whole Universe using their relative ratios.

This is only an estimate because a certain portion of the sky can contain a higher number of galaxies than a certain other portion and vice versa.

In order to improve it, several portions of the sky can be mapped individually.