"How'd the moon get here? Look, you pinheads who attacked me for this, you guys are just desperate. How'd the moon get here? How'd the sun get there? How'd it get there? Can you explain that to me? How come we have that and Mars doesn't have it?" -Bill O'Reilly Once upon a time, humans looked at the tides -- going out and coming in -- and we had no idea what caused them. At high tides, the sea level would rise, and the coast would get swept up by the oceans, while at low tides, the water would recede, leaving tidepools behind.