Astronomy Practice Exam

What are tides primarily caused by?

1. The Earth's rotational speed

2. The gravitational pull between the Earth, Moon, and Sun

3. The position of the planets in the solar system

4. The temperature of the water in the oceans

The correct answer is: The gravitational pull between the Earth, Moon, and Sun

Tides are primarily caused by the gravitational pull exerted by the Earth, Moon, and Sun. The gravitational force of the Moon is the most significant factor, as it exerts a pull on the Earth's oceans, creating a bulge or high tide in the water directly beneath it. On the opposite side of the Earth, another high tide occurs due to the centrifugal force resulting from the Earth-Moon system's rotation. The Sun also plays a role in the tidal phenomenon, albeit to a lesser extent compared to the Moon. When the Earth, Moon, and Sun are aligned during new or full moons, the gravitational forces combine to produce especially high and low tides, known as spring tides. Conversely, when the Moon is at a right angle to the Earth-Sun line, the differing gravitational influences result in lower high tides and higher low tides, called neap tides. Other factors, such as the Earth's rotational speed, the positions of the planets, and water temperature, do not primarily cause tides. While these may influence local tidal patterns or affect ocean currents, they do not have the direct gravitational impact that the Moon and Sun exert on Earth's oceans. Understanding the primary cause of tides is essential in studying oceanic behavior and the interaction between celestial bodies.