IAS 2011 — Physics

The surface of a lake is frozen in severe winter, but the water at its bottom is still liquid. What is the reason ?

An artificial satellite orbiting around the Earth does not fall down. This is so because the attraction of Earth 1. does not exist at such distance 2. is neutralized by the attraction of the moon 3. provides the necessary speed for its steady motion 4. provides the necessary acceleration for its motion