This week, the world is celebrating the 50th year anniversary of the first people to walk on the surface of the Moon. On July 19, 1959, NASA’s Apollo 11 entered the Moon’s orbit. Aboard were astronauts Neil Armstrong, Buzz Aldrin, and Michael Collins. The following day, on July 20, Armstrong and Aldrin went aboard the Lunar Module Eagle while Collins stayed to pilot the Command Module Columbia. The Eagle soon landed on the surface of the Moon, making Armstrong and Aldrin the first two humans to walk on the surface of another celestial object.
Since that momentous day 50 years ago, only 12 people have ever walked on the surface of another world. And so far, there is no other world humans have stepped on besides the Moon.
The Moon carries great cultural significance to cultures around the world and throughout history. Just think of all the songs, from pop songs to folk songs, that mention the Moon. Not only that, but our human calendars are partly based on the Moon’s cycles. This can be seen in the fact that the word for month in many languages is based on the word for ‘moon’. This is not surprising given its prominence in our sky. It is, after all, our neighbor in space.
Better yet, it is the Earth’s companion in a vast universe that is mostly empty. (Well, empty relative to the things we humans are interested in, such as atoms and molecules. The vacuum of space is of course an exciting arena for many phenomena.)
To get a sense of how lonely our planet would be if it did not have a Moon, let’s look at the spaces between our other neighbors in space.
If the Earth were the size of a basketball, the Moon would be about the size of a tennis ball. Based on its composition, most scientists think that the Moon was formed from a collision between the young Earth and a Mars-sized planetary object billions of years ago. This proposed origin explains why the composition of the Moon is partly like that of the Earth, but also partly different.
At this scale, how far would the Moon be from the Earth? Try to make a guess for a moment.
Is it a couple of paces away? A dozen paces away? Actually it is more than 70 meters away! That is more than 30 times the diameter of the basketball.
Even though this sounds far—and at more than 380,000 kilometers it is—it is far closer to us than any other things in the universe. Even at its closest, the planet Venus gets no closer than 38 million kilometers from Earth.
In the scale of the basketball and tennis ball, Venus (which would be the size of a youth club basketball compared to the Earth’s professional league ball) would be around three quarters of a kilometer away!
Farther celestial objects seem even more unreachable. Mars does not get closer that 54 million kilometers away (more than a kilometer away, in the scale of the basketball Earth). Meanwhile, the Sun is around 150 million kilometers away (about three km away from the basketball Earth). The farthest reaches of the Solar System, the Oort Cloud, is 100,000 times farther than this. The next nearest star, Proxima Centauri, is more than 260,000 times farther.
In the context of these vast distances, the Moon is really just a proverbial stone’s throw away. Except that we need to throw the stone really fast to escape the Earth’s gravity and then maneuver it well to lands safely on the surface of the Moon.
It should then come as no surprise that despite the excitement over visiting other planets, futurists around the world say we should prioritize visiting the Moon again soon. This time, they say, the motivation should not be fear and aggression, as it was in the original space race between the United States and the Soviet Union.
Instead, the goal of visiting the Moon again is to take advantage of its strategic properties. This includes its weaker gravity, which can then allow rockets launched from there to require less starting fuel.
The Moon can also provide invaluable experience about the effects of living on an alien world, but unlike Mars which requires a great voyage across the dangerous, radiation-filled space between the planets, the Moon is only less than a dozen days away.
Of course, visiting the Moon again should not take priority over solving our problems here on Earth. In fact, the Moon’s importance to the development of life on Earth serves as a reminder of the fragility of our planet’s ability to host life.
Without a Moon to stabilize the Earth’s orbit, we would probably not be alive today. Such is the sensitive nature of life on this, or any planet. Hence, as we look up at the Moon during the 50th anniversary of the time people first walked on it, I hope it reminds us of how lonely our planet is in the universe, how there is no Planet B (and therefore no Plan B), and that we should do everything within our power to protect our home orbited by our lone but beautiful Moon.