What Am I Riddles

Question: I move faster in certain solids, but slower in certain gases. I am typically broken by objects with large masses. I can be used as for pleasure, practice, and even an alarm. If used excessively, I can cause harm. What am I?

Question: It is able, but not capable.
It can stop, but not go.
It is dead, but not yet perished.
It's a ghost, but not paranormal.

Is it high, or is it low?

Question: We are just like people. We grow, we get old, we die off. We come in many different colors. Black, white, brown. We come in a army, there are thousands of us, yet we have no war. But we will still die off over the years. What am I?

Question: I rule the ends of the universe. I control its laws. I reign the galaxy. The start of space is the start of me. The end of the universe is the end of me. The name of my slaves bring mighty terror to you. The universe wouldn't work if it wasn't for me. What am I?

Question: The more you cut into me the bigger I grow, what am I?