WTF, Universe? I can see your past
The first of a series of posts about our weird as fuck Universe.
Perhaps you’ve seen this cliche in movies: there’s an academic at a house party who bores everyone to tears trying to explain how, contrary to popular belief, there’s really so little we understand about their narrow, obscure topic of research.
Well, I’m a cosmologist, and my field of study is the Universe as a whole. I don’t even have to get to my own narrow research topic before I can say, “We have no fucking clue what’s going on.”
It’s not that we don’t know a lot, because we do. But we’ve discovered that the stuff we know about is only a tiny fraction of what’s out there. We know there’s some weird shit going on, and we can quantify that shit, but we have yet to fit that shit into a coherent theory. And some of our theories are very odd. Unsettling. Even some of the things we know, to high precision, are difficult to conceptualize. If you’ll allow me the use of some jargon, we could call it, “weird as fuck.”
In this “WTF, Universe?” series, I will give an overview of our current understanding of cosmology, while acknowledging that the Universe, both what we do know and what we don’t know about it, doesn’t make any sense.
Tune in weekly for topics such as: the infinity of existence is getting even bigger; space, which is a relation between things but not a thing of itself, nevertheless can curve and ripple; most of the matter in the Universe is some weird “dark matter” that we don’t understand yet; and there’s an even weirder thing pushing stuff away from each other, causing the expansion of the Universe to accelerate.
Distance equals time
The first thing to understand about the Universe is that distance and time are practically the same.
The speed of light is a cosmic speed limit. Nothing can travel faster than light. Not even neutrinos. There was a short time where we thought, maybe, neutrinos could be faster, but it turned out to be a measurement error, and Einstein was saved.
Now, the speed of light is SUPER FAST, but at the same time, the Universe is SUPER HUGE, which means that even light takes a LONG FUCKING TIME to get from point A to point B, cosmologically speaking. We can measure these large distances in light-years — it takes light a billion years to travel a billion light-years.
The upshot of this is that we can only ever see the Universe as it was in the past. And the farther out we look, the farther back in time we are looking. This is true for everything, but usually it doesn’t matter. When you look at something 1 meter away, you are actually seeing it as it was, 1 billionth of a second ago. The light from the Sun is 8 minutes old. But the Universe is so large that when we observe distant objects with our telescopes, we are measuring light that took a super long time to reach us.
In fact, we know that the Universe had a beginning because we can almost see it. We can see all the way back in time to when the Universe was just a baby, 13 billion years ago. This light is called the cosmic microwave background radiation, sometimes described as the afterglow of the Big Bang, though I’m not sure science communicators realize how pornographic that sounds.
This post-climactic afterglow is the earliest light it is possible to see because earlier than that, the infinity of stuff in the infinite Universe was too close together for light to get anywhere without bumping into electrons. But that’s a subject for another post. Next time, I will attempt, and fail, to convey just how ridiculously large the Universe is — even our relatively small patch of sky that we call the “observable Universe” that isolates us from infinity.