PLANET EARTH From Pole to Pole

The youngsters are exhausted but their mothers have made this journey before and they know that they're close to water. After many hundreds of miles they've arrived. The lives of these elephants are dominated by the annual rhythm of wet and dry, a seasonal cycle created by the sun（普遍认为潮汐是月球的引力导致的，但其实太阳对地球的引力也会导致潮汐效应。太阳引力导致的潮汐效应大约是月球的一半,当月球处在太阳与地球的连线上时,日月引力相互叠加,地球上的潮汐现象最强。当月球继续转过90度时,月球引起的潮汐效果将被太阳的作用抵消一大半,此时地球的潮汐现象最弱。）.



At the southern end of the earth, after four months of total darkness, the sun once more rises over Antarctica. Now at last the Emperor penguins abandon their huddle. The males are still carrying the precious eggs that they've cherished throughout the Antarctic winter. With the returning sun the eggs hatch. Other birds have not even arrived. but the Emperors by enduring the long black winter have given their chicks a head start. These youngsters are now ready and eager to make the most of the brief Antarctic summer.