Everytime we look at the sun, we are looking in past. Due to the finiteness of the speed of light, it takes 8 minutes for light to come to earth. So when I am looking at the sun, I am currently looking at sun 8 minutes ago.
When I am looking at the moon, I am looking at the moon half second ago, and jupiter 30 minutes ago. If due to some cosmic catastrophe, the sun is destroyed, it would take us 8 minutes to realize that impact of missing sun.
It’s amazing how the sky is the book to the past. Soem of the stars are billions of light years away. That means that it might be possible, the the stars we see in the sky, may no longer be existing.
Einstein proved that nothing can go faster than speed of light because no massive object can travel at that speed. Light is fast at the speed of 299, 792, 458 m/s. Even at the break-neck speed, light takes billions of years to travel from one corner of the universe to other.
So if Human needs to dominate or colonize the universe, we need to find a clever way to intergalactic space travel. Even accelerating close to speed of light, would make our journey impossible.