Study the first 3 graphics and then answer the questions that follow each. Once you are sure you understand how the lunar
day, the position of the sun and the moon, and orbital variations affect the tides, then try to apply this knowledge, and
Be the Captain.
Position of theSun and Moon
Be the Captain
Knowing when and how much the tides will rise and fall each day is important to beachcombers, mariners, fishermen, and the
people who operate seaside industrial and commercial facilities. Miscalculating the arrival and size of the tides can have
expensive, even deadly, consequences.
Predicting the tides is complicated because the tides are affected by many factors. In this activity, you'll have a chance
to consider some of the most important and universal influences, those due to the movements of the sun, the moon, and the
earth. In reality, a number of local and transient factors, such as the shape of the coastline, the flow of currents, and
the weather, must also be taken into account.
Play the animation below to see how the relative positions of the sun and the moon effect the tide, then answer the
Position of the Sun and Moon
The height of the tides varies over the course of a month. The highest highs and lowest lows, called spring tides,
occur when the moon and the sun are aligned. Moderate highs and lows, called neap tides, happen when the sun and
the moon are at 90o to one another.