How big is it?
Nobody really understands how vast the universe is. People throw words like “infinity” around as if they actually know what it means. They don’t. Nobody does. Because they can’t. There’s not enough substance in the human brain to contain a true understanding of how vast the universe is. And I haven’t even talked about infinity yet. That’s just the observable universe, which is the 92 billion light-year-wide hole we happen to live in, far beyond our comprehension. But I’ll try to explain it to you:
Everything, everyone, and every event you've ever experienced lies on the surface of a rock flying through space around a star. Most people know that the Sun is much, much bigger than Earth. It looks like this:
That little blue ball bearing? That's your life. That's all that matters to you. That's your dreams, ambitions, and hopes. And that's what they are; a pill flicked by a blaze of sunlight.
On July 23, 2012, a giant explosion occurred on the Sun that, had it occurred 9 days earlier, would have destroyed every electronic device on the planet and set humanity back to the 19th century.
Welcome to level one.
Now here is level two.
This is Betelgeuse (say that three times), a beautiful bright red star in the constellation Orion:
This is what astronomers believe Betelgeuse looks like, compared to the sun:
If you look closely, you might see it.
If Betelgeuse replaced the Sun in our Solar System, it would nearly swallow Jupiter. This would change the daytime sky on Saturn's moon Titan, which is also the furthest we've ever sent a lander.
One day, soon, Betelgeuse will go supernova. When it does, it will light up our sky for a few months, then disappear forever. Whatever companions, planets, or anything else, it has managed to accumulate during its short life will not only vanish, but leave no evidence that they ever existed. That's the universe.
Welcome to level two.
Now to level three.
This is Proxima Centauri. Proxima Centauri is a red dwarf star located, as its name suggests, in the constellation Centaurus.
Proxima Centauri is a truly unremarkable star. In fact, the only thing remarkable about it is how unremarkable it is. Even by our standards, it's small and dim: our Sun is 6.5 times as massive and 40,000 times as bright.
But, as the name suggests, it is the closest star to our Solar System, only 1.3 parsecs away.
What's a parsec, you ask? It's about 30 trillion km.
Thirty trillion kilometers. One kilometer is one million millimeters. One millimeter is about the width of a grain of sand. That means that even if you made one kilometer the width of a grain of sand, the distance from Earth to Alpha Centauri would still be about the same as the distance from Earth to Venus.
And what's in that 30 trillion km? Nothing. Nothing. There might be the occasional interstellar rock, a speck of cosmic dust, or a cosmic ray, but measured in terms of the distance from the Sun to the nearest star, it's nothing. Just nothing. That's essentially the universe. Matter is an afterthought, and we are afterthoughts of matter.
Welcome to level three.
Now to level four.
In themselves, stars are lonely islands in a black ocean. But as you zoom out, they begin to coalesce, like particles slowly forming into smoke. Eventually, they blur and become part of a larger structure.
This, the best we can make of it, is the Milky Way Galaxy. This is our home, not the one that will be noticed. This is what happens when the parsecs of emptiness between the stars grow and grow. It's 50,000 parsecs wide, and contains up to 400 billion stars, or about the number of grains of sand in a medium-sized sand dune.
See that mound in the center of the picture? Imagine being a grain of sand in that mound, contemplating the wonder of your own existence, all your great news, your fears, and your hopes for the future. Well, that grain of sand isn't you. It's every human being on this planet.
One day, a gamma-ray burst, a massive hypernova, will occur somewhere in the galaxy, and it will be so parallel to Earth that its energy will burn through our planet's ozone layer, destroying most life on the planet. Still, the Galaxy will continue as usual.
Welcome to level four.
Now to level five.
Our galaxy is not alone. It is part of a small cluster of galaxies that are gradually merging to form one giant galaxy:
Despite their closer proximity, they are still about 20 times larger than our Galaxy. And our small local group is just the tip of the iceberg to our true home:
This is the Virgo Supercluster, a cloud of galaxies centered on the Virgo Cluster, a dense cluster of galaxies four quadrillion times the mass of our Sun. The cluster is 16.5 million parsecs away, yet its gravity still pulls our local group toward it. Within the Virgo Cluster, its immense gravitational pull pushes galaxies to near-relativistic speeds, destroying their free hydrogen and leaving them bereft of new stars. Imagine, entire galaxies, slowly dying, unable to renew themselves, simply because of their location.
But that's not the end of it. It was recently discovered that the Virgo Supercluster is just a small component of an even larger structure, dubbed Laniakea: