Travelling to space was once something that only a very small percentage of the world's most qualified people could do.
The likes of Neil Armstrong and Buzz Aldrin will always be remembered as the first men on the moon but in the 2020s alone, we've seen the likes of Elon Musk, Katy Perry and Jeff Bezos head up above the world's atmosphere.
Seeing the Earth from above is undoubtedly a life-changing and eye-opening experience but the beauty of space travel is that to this day, we're still learning more and more about it.
Back in 1962, when things were a little newer, John Glenn became one of the lucky few to head up in a rocket, and he saw something which 'he'd never seen anything like'.
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"This is Friendship 7," Glenn said during that first orbit. "I'll try to describe what I'm in here. I am in a big mass of some very small particles, that are brilliantly lit up like they're luminescent. I never saw anything like it. They round a little; they're coming by the capsule, and they look like little stars. A whole shower of them coming by."
"They swirl around the capsule and go in front of the window and they're all brilliantly lighted. They probably average maybe seven or eight feet apart, but I can see them all down below me, also."
Glenn, who was the third American in space, became the first human to orbit the Earth before returning home but it also became memorable for other reasons as he described the 'fireflies' to colleagues back on home turf, which left them concerned about the potential impact on the spacecraft.
"They're very slow; they're not going away from me more than maybe 3 or 4 miles per hour. They're going at the same speed I am approximately. They're only very slightly under my speed," he added.
"They do have a different motion, though, from me, because they swirl around the capsule and then depart back the way I am looking. There are literally thousands of them."
The mystery became a little clearer when they disappeared when he was in 'bright sun', having first noticed them when the Sun was 'coming up'.
He said at the time: "Now that I am out in the bright sun, they seem to have disappeared. It was just as the sun was coming up. I can still see just a few of them now, even though the sun is up some 20° above the horizon."
NASA later determined that the 'fireflies' were actually just tiny icy particles traveling alongside the spacecraft, which were illuminated by the Sun at certain angles.
Glenn would later die in 2016 at the age of 95, but there's no doubt that he will have remembered the beautiful sight of the mysterious 'fireflies' for the rest of his life.
James Moorhouse