How does the gravity of the sun and the moon affect the earths tides

Long, the ocean tides we experience on earth are caused by the sum of the moon's gravitational gradient and the sun's gravitational gradient. When the sun and the moon are aligned, or nearly aligned, their gravitational gradient fields add together constructively, leading to extra strong tides (high tide is extra high and low tide is extra low). This alignment happens when the moon is a new moon or a full moon, which occurs about every two weeks. The moon takes about a month to orbit the earth, hence strong tides occur about twice a month. In contrast, when the sun and the moon are unaligned, their gravitational gradients tend to cancel out, leading to weak tides (high tide is not very high and low tide is not very low). But even when the sun and moon are perfectly unaligned (they form a 90 degree angle relative to the earth), there are still tides because the moon's gravitational gradient is stronger than the sun's. The sun's gravitational gradient never completely cancels out the moon's. The biweekly strong tides are called "spring tides" even though they occur all year long. The name does not refer to the season "Spring", but to the verb "spring" which means to leap forth, because the strong high tides leap higher up the shore. The biweekly weak tides are called "neap tides".