What is a Light Year?

The video explains the concept of light speed, which is 300,000,000 meters per second, and why astronomers use light years to measure vast distances in space. It highlights that light takes 8.3 minutes to travel from the Sun to Earth, meaning we see the Sun as it was 8.3 minutes ago. The nearest star, Proxima Centauri, is 4.2 light years away, so its light takes 4.2 years to reach us. This illustrates that observing distant objects in space is akin to looking back in time due to the finite speed of light.

What is the distance of Proxima Centauri from the Earth in light years?

What does it mean when we say we are looking back in time when observing stars?