The temperature began to rise at the center of the solar nebula because

If we represent the solar system on a scale that allows us to walk from the sun to pluto in a few minutes, then a) the planets are microscopic and the stars are millions of miles away. b) the planets are the size of basketballs and the nearest stars are a few miles away. c) the planets are marble size or smaller and the nearest stars are thousands of miles away.

If scientists only detect p waves in a certain layer of earths interior what does that tell us?

Hey, i was what is consisted in a sustainable city? like what unique designs they have, etc. for answering ; )