Apogee
Topic: Movements of Ocean Water: Waves, Tides and Currents · NCERT: Class 11, Ch 13 "Movements of Ocean Water"
Meaning
Apogee is the point in the Moon's orbit where it is farthest from the Earth, about 405,000 km away. The Moon's path round the Earth is an oval, not a perfect circle, so its distance keeps changing. The Moon reaches apogee once a month, about two weeks after perigee, its closest point. At apogee the Moon's pull on the oceans is weaker. High tides are lower than usual, low tides are higher than usual, and the tidal range (the gap between high and low water) is smaller than average.
Example
If apogee falls during a neap tide (when the Moon is at its first or last quarter), the sea at a place like the Gulf of Khambhat in Gujarat rises and falls less than it normally would. Tidal ranges here are among the smallest of the month.
Don't confuse with
- Aphelion: this is the Earth's farthest point from the Sun, around 4 July. Apogee is about the Moon and the Earth.
- Perigee: the Moon's closest point to the Earth. At perigee the tidal range is larger, not smaller.