Why is it difficult to see galaxies and objects that are very far from us?
One of the reasons that explain this is 'Redshift'.
We have built massive telescopes and keep innovating to explore the world beyond the Earth. The information about other galaxies and objects of the universe will help us know more about how we have reached till here. Today we will be talking about why we need to build massive telescopes to see these lights that are coming to us from a billion light years away.
Straightaway, one of the biggest reasons is 'Redshift'. When light left from the stars and galaxies, formed during the early days of the universe, it had to travel a large distance, almost 13.6 to 13.8 billion light years. While the light travels it loses or changes it colour because of the change in wavelength of the light. This shift in wavelength is called as 'Redshift'.
But why does 'Redshift' happen?
Einstein's theory of General Relativity explains this phenomenon. It says that the universe is expanding and the objects too are going away from each other. Because of this the wavelength of the light shifts towards red spectrum. Red has the highest wavelength in the visible colour spectrum. If the wavelength of light increases further, the light becomes infrared.
The light that reaches us is normally in the red spectrum or near- and mid-infrared part of the electromagnetic spectrum. And for that we need infrared telescopes that can track these lights.