Can viruses, bacteria, and fungi be considered parasites?

Describe the path of a ray that approaches a mirror parallel to the principal axis.

Estimate the schwarzschild radius (in kilometers) for a mini-black hole formed when a superadvanced civilization decides to punish you (unfairly) by squeezing you until you become so small that you disappear inside your own event horizon. (assume that the your weight is 50 kg)

Observations show that interstellar clouds can have almost any shape and