"C'mon, let's walk around the tower more." said Marcus. David followed him to...
..... a stairwell that descended deep into the tower.
Down and down they went until the stairway stopped at a large room with huge humming machines that filled the room. "What are these?" asked David. "These machines collect energy from Terra's anti gravitation field. The energy is used to run the computer you saw at the top of the tower." replied Marcus. "Anti gravitation field?" a perplexed David quizzically replied. Marcus started to explain, but decided instead to motion David to the window in the machine room. Marcus then handed David a small coin he took from his pocket. "Now", said Marcus, "hold the coin outside the window and release it." David stretched his arm, with coin in hand, out the window. When David released the coin it ............