The moon has a radius of 1,080-miles (1,737-kilometers). This means that the moon's diameter is 2,159-miles (3,475-kilometers) across. For comparison, the diameter of Earth is 7,918-miles (12,742-kilometers). This shows that the moon is approximately a quarter the width of Earth. The moon's size impacts specific processes on Earth, the most notable of which is the tides. The moon’s gravitational pull causes the oceans to bulge on either side. As the planet rotates, these bulges also rotate, causing the rise and fall of seawater. Gravitational force is dictated by the size and distance of objects, so if the moon were the size of Mars’s moons, Phobos and Deimos, it would not have as strong of a gravitational pull and thus would not affect the tides.
Compared To Other Objects in the Solar System
It can be hard to visualize just how big celestial bodies are and the moon is no exception. Earth’s moon is fairly big in comparison to other moons in the solar system, but what exactly does that mean? The moon orbiting Earth is the fifth largest moon in the solar system. Moons larger than ours include, in decreasing order, Ganymede, Titan, Callisto, and Io. Even though Earth’s moon is not the biggest in the solar system, it is the largest when compared to the planet it orbits. The moon is also quite a bit bigger than the dwarf planet, Pluto which has a radius of 1,477-miles (2377-kilometers). This makes Pluto around 70% the size of Earth's moon.
Compared to countries on Earth
It still might be hard to visualize just how large the moon is when only comparing it to other celestial objects. Comparing the size of our moon to countries and continents on Earth might show more context into its sheer size. The United States of America has a diameter of 2,897-miles (4,662-kilometers), making it almost the same width as the moon. However, having the diameter of the moon only paints a part of the picture. To compare the moon's size to the size of countries on Earth, the surface area is required. The moon’s surface area is 14.6-million square miles (38-million square kilometers). When compared again to the United States of America, the moon has approximately four times as much surface area. This is smaller than the continent of Asia (including Russia) which boasts a surface area of 17.2-million square miles (44.6 million square kilometers).