2CS60_K2 _ 1TeachersGuideK3.indd 2 4/23/10 8:28:53 AM

Gravity causes the tides! Gravity is the force that keeps the moon in orbit around earth. But did you know the moon pulls on the earth too? The closer two objects are, the more pulling force they have on each other. The earth has solid land and liquid oceans. Whatever portion of the earth is closest to the moon is most strongly affected by the moon’s gravity. The water there rises in a bulge, causing the sea to rise in a high tide. In order for there to be a high tide somewhere on earth, there must be a low tide somewhere else. The relationship between gravity and tides is fascinating. To learn more, fi nd a book or website about the tides. WHAT IS GRAVIT Y? The downward force on an airplane is caused by gravity. Gravity is the force tha