My son's science project was supposed to demonstrate the concept of gravity. He dropped a rock off the balcony, timed it, and wrote in his report: 'Object fell. Conclusion: gravity works. Next time I will drop a heavier object to determine if speed increases.' His teacher wrote back: 'Please do not drop objects off the balcony. Also, Galileo covered this in 1590 and he did not have a balcony.'