How big it is.
No one really understands how vast the universe is. People bandy words like “infinite” around as if they actually know what they mean. They don’t. No one does. Because they can’t. There isn’t enough matter in a human brain to contain a true understanding of how vast the universe is. And I’m not even talking about infinity. Just our observable universe, which is the 92 billion-light year wide cubby hole we happen to reside in, is vast beyond our understanding. But I will try to spell it out for you:
Everything, everyone, and every event you have 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 the Earth. This is how much bigger:
That little blue ball bearing? That’s your life. That’s everything that matters to you. That’s your dreams, your ambitions, your hopes. And there they are; a pill flicked away by a solar flare.
Welcome to level one.
Now here’s level two.
This is Betelgeuse (say it 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 carefully, you might even see it.
If Betelgeuse were placed in our own Solar System, it would almost swallow Jupiter. It would turn the day sky blue on Saturn’s moon Titan, which is also the farthest we have ever sent a lander.
One day, sooner rather than later, Betelgeuse will go supernova. When it does, it will light up our sky for a few months, than fade forever. Whatever companions, planetary or otherwise, it has managed to accrue over its brief life will not only cease to exist, but leave no evidence of their ever having existed. Such is the universe.
Welcome to level two.
Now on 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 completely unremarkable star. In fact the only thing remarkable about it is just how unremarkable it is. Even by the standards of red dwarfs, it is small and dim: 6 and a half times smaller and 40,000 times dimmer than the Sun.
But, as its name suggests, it is our Solar System’s closest star, a mere 1.3 parsecs away.
What is a parsec you ask? Well that doesn’t really matter but what you need to know is that it is roughly 30 trillion km.
Thirty trillion km. A km is a million milimetres. A milimetre is roughly the width of a grain of sand. That means that even if you reduced a km to the width of a grain of sand, the distance from Earth to Alpha Centauri would still be nearly the distance from Earth to Venus.
And what is in that 30 trillion km? Nothing. Nothing whatsoever. Well there may be the occasional interstellar rock, speck of cosmic dust or cosmic ray, but measured against the vast volume stretching from our Sun to its nearest neighbors, it’s nothing. Just frigid, cold, black, emptiness. That is, essentially, what the universe is. Matter is an afterthought, and we are an afterthought of matter.
Welcome to level three.
Now on to level four.
In themselves, stars are lonely islands in a sea of black. But as you zoom out, they begin to come together, like particles slowly forming into smoke. Eventually they blur and become part of a larger structure.
This is, as best as we can construct it, the Milky Way Galaxy. It is our home, not that it would notice. It is what happens when that parsec of nothing between stars adds up and up and up. It is 50,000 parsecs across, and contains up to 400 billion stars, or about as many as there are grains of sand in a fair-sized dune.
See that dune in the middle of the picture? Imagine being a grain of sand in that dune, contemplating wonders of your own existence, the sheer import of the news and your fears and hopes for the future. Well that sand grain isn’t you. It’s all human beings on the planet.
And our galaxy isn’t alone. It is part of a small group of galaxies that are gradually coming together to form one gigantic galaxy:
Though the distances are closing, they are still about 20 times larger than our Galaxy. And our little Local Group is just the tip of the tail to our true home:
This is the Virgo Supercluster, a cloud of galaxies centered on the Virgo Cluster, a dense, well, cluster of galaxies a quadrillion times the mass of our Sun. The Cluster is 16.5 million parsecs away, and yet we still feel its gravity.
But recently it was found that the Virgo Supercluster is just a small component of an even larger structure, dubbed Laniakea:
Laniakea is essentially a vast, three dimensional river basin of flowing galaxies, all being drawn toward the Great Attractor, a mysterious object that we can’t see, because the Milky Way blocks it in our skies. See that little dot marked “You are here”? That’s our Local Group. More than a trillion stars, just like our Sun, all blotted out by a pointer.
Laniakea is 159 million parsecs across, and contains 100 quintillion times the mass of the Sun. To measure yourself against that is equivalent to a mite living in a grain of sand comparing itself to the largest, broadest beach in the world.
Welcome to level four.
Now on to level five.
Laniakea is actually a fairly representative component of the wider observable universe. Current estimates place the diameter of the observable universe at 29 billion parsecs, which, assuming a volume for Laniakea of a 150 sextillion cubic parsecs, means that our observable universe contains about a hundred million structures about the size of Laneakea; a fairly comprehensible number by most standards.
But note that I said “observable universe.” The universe that we can see is only that fraction of it whose light has managed to reach our eyes within the 13.8 billion years since the Big Bang:
But the “real” universe, we think, is far, far, far larger than that. No one really knows exactly how much bigger, but one estimate I read placed it at 10^10^12.
What is that? It’s one followed by a trillion zeroes. Don’t even try to comprehend it. You can’t. There’s no number you could throw at it that would make a dent in it. Cube it. Multiply it by a duotrigintillion. Hell, cube it, fill a space that big with atoms and then count the atoms. Still the same number. Our concept of reality breaks against numbers like that. And that isn’t even the highest number out there.
According to the many worlds hypothesis of quantum mechanics, for every quantum event that takes place, another parallel universe exists in which the alternative quantum event took place. Now consider the number of quantum events since the Big Bang. Consider how many quantum events have occurred as a conseqence of those events. Now consider that, according to the many worlds hypothesis, not only did every single one of those events create their own universe, but every single one of those universes must exist.
And what is the total number of universes? 10^10^115. Again, don’t even try to comprehend that number. It makes a googolplex look small. But that’s just our universe, with its own laws of physics. Some speculate that universes can form that have their own laws of physics. Given that string theory allows for 10^500 possible physical laws, the number of potential universes that may exist is…
10^10^10^7.
Even expressing that number in words is difficult. But I will try. Imagine 1 followed by 10 million zeroes. Now imagine one followed by that many zeroes. That’s how big that number is. It’s so big that there isn’t enough room in the universe even to write it down. Not just the observable universe. The whole universe.
Think about what keeps you up at night. Our world is prey to megalomaniacs, pestillence, perhaps even the whims of gods and monsters. What are they compared to this? A wisp in the wind. Who do you pray to? Who do you place your hopes in? What are your dreams? They are nothing. Less than nothing, compared to what is out there.
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