Final answer:
We see old light from stars like Canopus because it takes time for light to travel across space. Thus, we're looking back in time to how these stars appeared years ago, with the light from Canopus being 310 years old.
Step-by-step explanation:
We are seeing extremely old light from stars like Canopus because light travels at a finite speed of approximately 299,792 kilometers per second (the speed of light). This means that when we observe distant objects in space, we are actually looking back in time. The light from Canopus, for example, takes roughly 310 light years to reach us, so we're seeing Canopus as it was 310 years ago. Due to this delay in the arrival of light, observing distant cosmic objects provides a historical record of the universe, giving us insight into the cosmic evolution. The fact that the universe is a vast expanse of time and space where we observe the past as we look further out is a core concept in cosmology, and provides astronomers with vital information about the early universe and the way galaxies and stars have developed over billions of years.