Things in space being “xxxx lightyears away”, therefore light from the object would take “xxxx years to reach us on earth”

Question

I don’t really understand it, could someone explain in basic terms?

Are we saying if a star is 120 million lightyears away, light from the star would take 120 million years to reach us? Meaning from the pov of time on earth, the light left the star when the earth was still in its Cretaceous period?

In: 292

Answer 1

Big numbers get hard to interpret, so let’s take it down to something easy to understand – a light switch.

The speed of electricity through a wire is about 100 times slower than the speed of light in a vacuum.

If you have a light switch in Los Angeles connected to a bulb in Chicago (about 2000 miles away), it will take approximately one second for the light to turn on after the switch is flipped.

A light-second is therefore 100 times that distance. That’s about the distance to the Moon.

A light-year is ~30 million light seconds.