Some of the stars you see in the night sky are already gone. Why is it possible to still see their light?

they are light years away

Explanation:

when you look at the sky you are looking at about 6 million years in the past because time travels differently between space and our atmosphere. That's why astronauts can feel like they have been gone for 3 days but really for 3 months.

Key point:

Light travels differently between space and Earth

"griffith's experiment discovering the "transforming principle" in pneumococcus bacteria. griffith's experiment, reported in 1928 by frederick griffith, was the first experiment suggesting that bacteria are capable of transferring genetic information through a process known as transformation." - griffith's experiment.