What can scientists gain clues about by analyzing the speed at which seismic waves travel?

When the earth was formed and cooled, why did nickel and iron end up in the center of the earth while basalt and granite ended up in the outer layers

After cloud droplets form, what must happen to them for precipitation to occur?

To apply in a gold the individual gold atoms are united to each other by means of a metallic bond. how would you use the gold block to determine the atomic radius of a gold atom?