Are we looking back in time when we see light from a star a nebula or a galaxy?

Yes, when we observe light from a star, nebula, or galaxy, we are looking back in time. This is because light travels at a finite speed, approximately 299,792 kilometers per second (186,282 miles per second). Therefore, the light we see from distant celestial objects has taken years, decades, or even millions of years to reach us, allowing us to observe them as they were in the past. For example, if a star is 1,000 light-years away, we see it as it was 1,000 years ago.