Question

How do astronomers estimate the size of the universe?

Answer 1

Hint:There are several methods and techniques that are used to measure the size of the universe. Most of these distance measurement techniques build upon the previous distance measurement techniques, in turn giving us a distance measurement “ladder” which gives a better perception in measurement of cosmic distances.

Complete answer:
To answer the question how big is our universe, it would make less sense if we talk about the entirety of it because the universe is expanding at speeds in the range of the speed of light. So, what we mean by estimating the size of the universe is, by calculating the size of the “visible” universe.
Now, this is done by a scientific process known as Red Shift. Similar to that of a car’s horn that changes pitch as it passes by due to the Doppler effect. Light too has a shift in its frequency or color depending on the fact that it is moving away from us or moving towards us. It has been observed as light moves away from us, it shifts for red. The faster it is relatively moving away from us, the more it shifts. When we look at (observe) a light wave that has travelled its way from the most distant parts in our universe, we measure its red shift and estimate the distance that the light wave has travelled from its point of origin to all the way here.

Note:
For a fact, we know that the universe is around 14 billion years old. So, assuming that the object whose light took 14 billion years to reach us would be the farthest is simply wrong as in these 14 billion years, the universe has expanded at an unknown rate. Some scientists even claim that the speed at which the universe is expanding is even far greater than the speed of light, but these are just assumptions and no valid proof is there to support them. That’s why we estimate the size of the visible universe as it makes more sense.