What is the Distance from Earth to Moon?

It is easy enough to come up with a number that will tell us how far the Moon is from the Earth. The distance is stated as an average – 238,857 miles or 384,403 kilometers. It’s the closest celestial body, since the stars we see in the night sky and the sun that warms the Earth are millions of miles away.

But there is a lot more to the story of how close the Moon is to the Earth. First of all, there’s the word “average.” This means that the Moon is not always the same distance away. Sometimes it is closer and sometimes it is a few miles farther away. Why? Because the best information we have from astronomers shows that the Moon doesn’t make a circular orbit around the Earth. The orbit is elliptical or slightly elongated.

Two Numbers

Research shows that the Moon is closest to the Earth at a point given the interesting name of “perihelion.” At this point, the distance from Earth to Moon is 225,622 miles or 363,104 kilometers. When the orbit takes the Moon as far from the Earth as it’s going to get (aphelion) the distance is 252,088 miles or 406,696 kilometers. The distance varies by 43,592 kilometers!!

Because of this, we see the Moon differently at various times. If the night is very clear and the sun is in a certain place in relation to the Moon, the surface looks very bright. If the Moon is also in the part of its orbit that puts it close to the Earth the Moon may appear to be very large.

Measuring or Guessing?

At some point in the past, astronomers were probably making an educated guess at how far the Moon was from the Earth. Information available in the 21st century makes this “educated guess” much more accurate. Reports from the National Aeronautics and Space Administration (NASA) indicate that astronauts put reflective mirrors on the Moon’s surface as part of a plan to measure distance across space. Laser beams are directed to the Moon and the reflection comes back to Earth. By calculating the amount of time it takes for this light to travel scientists can come up with a number that indicates how far the Moon is from the Earth.

Why is the Moon and the distance from Earth so interesting to scientists? The answer is rather simple: The Moon is the only object that naturally orbits the Earth. Theories also suggest that the position of the Moon and the distance from Earth has a lot to do with life on our planet. This natural satellite may affect our tides, our moods and much more in plant and animal life.

The Moon also provides us with one of the key measurements for the passage of time. Our 12 calendar months are loosely based on the phases of the Moon, which rotate about in 29.5 days. The Moon actually orbits the Earth in 27.3 days. In general terms, the Moon is our closest celestial neighbor, even though it is thousands of miles away.