Just when you think that you know something..y ou learn that you really know very little.

Yesterday while taking my kids to school, I had to give way for an ambulance. My son noticed that we could hear the siren louder when the ambulance was behind us compared to when it was in front of us.

“Doppler effect” I explained.

He was pretty impressed and I added one more feather to my crown..

Few minutes later, we were behind a bus that had the sign for solar power with the tag line “make energy fresh every day”

I read that aloud and  said  “that is not possible, energy can neither be created nor destroyed” (first law of conservation, thermodynamics)

“Mom, you are wrong. Universe is expanding, that simply means the law is wrong”

I had never even thought about that. My son will be 16 soon and he has already thought of all that!

Btw, I was reading about what he said about expansion of universe..and some of the writers talk about stored gravitational energy is being used for the expansion.. This is beyond my ability to comprehend.. so if you know something about it, do leave a comment.