Detailed Instructions: Given a passage and a query based on the passage, generate an unambiguous, concise and simple answer to the query from information in the passage. Note that the answer may not be present in exact form.
Problem:A more pronounced tide, when high tides are very high and low tides are very low, is called a "spring tide." These periods occur during the New Moon, when the Sun and Moon are lined up on the same side of the Earth, and the Full Moon, when the Moon and Sun are on opposite sides of the Earth. Together, the gravitational effects of the moon and the sun affect the Earth's tides on a monthly basis. Click the image to see an animation. The moon is a major influence on the Earth's tides, but the sun also generates considerable tidal forces. Solar tides are about half as large as lunar tides and are expressed as a variation of lunar tidal patterns, not as a separate set of tides. The Earth experiences two high tides per day because of the difference in the Moon's gravitational field at the Earth's surface and at its center. You could say that there is a high tide on the side nearest the Moon because the Moon pulls the water away from the Earth, and a high tide on the opposite side because the Moon pulls the Earth away from the water on the far side. The moon is the dominate tidal influence. The moon's tidal influence is about twice that of the sun. Remember, tides are due to a non-uniform gravitational field, squishing and squashing on a body in free motion within the gravitational field. The height of the tides is also affected by the position of the Moon in its orbit around the Earth. The Moon travels around the Earth once every 28 days. Depending on where it is on its journey, the difference between high and low tide may be more or less pronounced. Sun's Tidal Effect. Even though the Sun is 391 times as far away from the Earth as the Moon, its force on the Earth is about 175 times as large. Yet its tidal effect is smaller than that of the Moon because tides are caused by the difference in gravity field across the Earth. The Earth's diameter is such a small fraction of the Sun-Earth distance that the gravity field changes by only a factor of 1.00017 across the Earth. The elliptial orbits of the moon around the Earth and the Earth around the sun have substantial effects on the earth's tides. Click the image for a larger view. Just as the angles of the sun, moon and Earth affect tidal heights over the course of a lunar month, so do their distances to one another. The actual force differential across the Earth is 0.00017 x 174.5 = 0.03 times the Moon's force, compared to 0.068 difference across the Earth for the Moon's force. The actual tidal influence then is then 44% of that of the Moon. The Moon is the dominant tidal influence because the fractional difference in its force across the Earth is greater than the fractional difference seen from the Sun. This difference in force follows the inverse square law. Tides are the natural rise and fall that occurs in major bodies of water, such as the ocean or large lakes. Tides are caused by the gravitational relationship between the Moon and the Earth. The Moon's gravity pulls on the Earth, causing the water to swell in the direction of the Moon. The exact timing and number of high tides per day varies by location, and is affected by such factors as geography, the shape of the coastline, the salinity of the water, the time of year, and the weather, among other things. Query: how does the moon influence the tides
Solution:
The elliptial orbits of the moon around the Earth and the Earth around the sun have substantial effects on the earth's tides.