This simple explanation shows how far away the Moon really is

Even though we can see the Moon shining brightly at night and sometimes during the day, it’s hard to understand how big and far away our closest neighbor really is.

How big is the Moon, then?

It’s not as simple as you might think that answer is. The Moon, like Earth, is not a perfect sphere. Instead, it’s a little bit flat (what we call an oblate sphereoid). This means that the diameter of the Moon at the equator is smaller than the diameter from pole to pole.

But the distance between them is only four kilometers. The Moon is about 3,476 km across at its equator, and it is about 3,472 km across at its poles.

To figure out how big that is, we can compare it to something about the same size, like Australia.

From one coast to another

As the crow flies, it takes 3,606km to get from Perth to Brisbane. Australia and the Moon look about the same size if you put them next to each other.

But that’s only one way to see things. Even though the Moon is about as wide as Australia, if you look at its surface area, it is much bigger. It turns out that the Moon’s surface is much bigger than Australia’s.

Australia has about 7.69 million square kilometers of land. On the other hand, the Moon’s surface is 37.94 million square kilometers, which is almost five times the size of Australia.

How far away is it?

When you want to know how far away the Moon is, the answer is more complicated than you might think.

The Moon goes around the Earth in an elliptical path, which means that its distance from our planet is always changing. During a single orbit, this distance can change by up to 50,000 km. This is why the Moon’s size in the sky changes a little from week to week.

Everyone and everything else in the Solar System also has an effect on the Moon’s orbit. Even when all of that is taken into account, the answer to how far away the Moon is from the Earth is always changing. This is because the Moon is slowly moving away from the Earth because of the tides.

Because of the Apollo missions, we’ve been able to learn more about that last point. When astronauts went to the Moon, they put a number of mirror reflectors on its surface. Lasers from the Earth are always aimed at these reflectors.

By timing how long it takes that laser light to go to the Moon and back, scientists can get a very accurate idea of how far away the Moon is and how far away it is getting from Earth. What happened? At a rate of 38 mm per year, or just under 4 m per century, the Moon is moving away from Earth.

Get me to the moon!

Despite all of this, the average distance between the Moon and Earth is 384,402 km. So let’s see what that means.

If I took the fastest route suggested by Google to drive from Brisbane to Perth, I would travel 4,310 km. It would take about 46 hours to drive across our whole country on that trip.

If I wanted to cover the distance between the Earth and the Moon in kilometers, I would have to make that trip more than 89 times. If I drove nonstop, it would take five and a half months, assuming I didn’t get stuck in traffic.

The Apollo 11 astronauts didn’t have to follow Australian speed limits, which is a good thing. After its launch on July 16, 1969, it only took the command module Columbia three days and four hours to reach lunar orbit.

An eclipse coincidence

The diameter of the Sun at its equator is almost 1.4 million km, which is almost 400 times the diameter of the Moon.

The distance between the Earth and the Sun (149.6 million kilometers) is almost (but not quite) 400 times the distance between the Earth and the Moon. This is one of the most interesting oddities in astronomy.

What happened? In the sky of Earth, the Moon and the Sun look almost the same size. So, when the Moon and the Sun are in perfect alignment as seen from Earth, a total eclipse of the Sun happens.

On Earth, these amazing eclipses will end one day, which is a shame. Because the Moon is getting smaller, one day it will be too far away from the Sun to completely block it out. But that day won’t come for a long time. Most estimates say it won’t happen for about 600 million years.

The people who went to the moon

Even though we’ve sent robots to the coldest parts of the Solar System, the Moon is still the only other world where people have set foot.

After 50 years, the number of people who have walked on the Moon and are still alive is going down quickly. Twelve people have been through that, but as of now, only four are left.

Even though the Moon is so big, the 12 people who walked on it only scratched the surface. We hope to go back in the next few years to inspire a whole new generation and continue the human exploration of our nearest neighbor in space.