The primary force would be Thermal Convection, it pushes it and thus makes continents drift.
-Hope that helps, Nexxmexx :3
<span>This is not a good answer, because some one t o forgot to tell us the important temperature, and the given atmospheric pressure "at sea level" makes really no sense. In SI units with dry air at 20°C (68°F), the speed of sound c is 343 meters per second (m/s).</span>
Microscope lenses , glasses for people who can't see faraway as well and microwave lenses which reflect electromagnetic radiation. Oh and curved mirrors.