look back in time

Light travels extremely fast (186,000 per second). However, because of the vast distances between the earth and the Sun (∼93 million miles), it still takes 8 minutes for light from the sun to reach Earth. So, when we see that light, we are seeing what the sun looked like 8 minutes ago. Similarly, when astronomers look through telescopes into deep space they are looking back in time and seeing what things in the universe looked like at an earlier point in time, not what it looks like now.  As of 2017, astronomers were able to look back to less than 1 second of the Big Bang which they maintain is when the universe came into existence from an initial singularity.