No problem, because it doesn’t get any easier. Nothing really is easy when it comes to cosmology. Not cosmetology. Cosmology. One is the study of beauty treatments and their application, and the other is the science of collecting the pieces of your MIND off the floor.
Thanks to data from the WMAP probe launched in 2001, we now understand the universe is ‘flat’ like a sheet of paper. The shape of the universe is defined by the path light takes from one object to another. In this case, the light travels in a straight line (excluding gravitational bending). At the same time, the universe is expanding as evident by observations made by astronomers that show galaxies moving farther and farther apart at an increasing rate. But it isn’t because the galaxies are moving, it’s because space is expanding. The Astronomy Cast analogy is to think of space as dough and galaxies as raisins in the dough. As the dough rises, the raisins grow farther apart, but only because the dough is expanding. We will be stealing this analogy for the rest of this post.
Now, where is this expansion coming from? That’s where the Big Bang comes in. In the beginning (if you can really call it that, because the current thought on the nature of tim- TOO MUCH, GO BACK!) the universe exploded out a singularity. The resulting matter expanded into the space that was rapidly being created and thus the universe was born. As the universe expands, gravity is pulling the matter back in on itself, but luckily for us, the rate of expansion is greater than the force of gravity trying to pull it back in. Now, as the expansion continues, space becomes diluted, and the gravitational pull weakens, and dark energy takes over, pushing the matter out faster and faster, now free from gravity. This is because for whatever reason, even as the density of matter decreases, the density of dark energy in the universe remains constant. Here’s a picture. IMBIBE IT.
Back to the comic: Because the universe expands infinitely, and the amount of stable elements are finite, everything can and must exist. Think of it as Shakespeare’s Chimps for nerds. If you have all the space and matter in the world, eventually you will come upon another you and you will do it an infinite amount of times. Travelling in one direction for enough time is like travelling through multiple dimensions. OH CRAP. But if you’ve been paying attention at all to this, you will be calling me out right…. now.
“But wait! Matter is NOT infinite, and therefore as the universe expands, it grows less dense. Your crazy paradox is just that! The raisins are the same, they’re just farther apart.”
You’re right! …and as the universe keeps expanding?
“Then after a while, we won’t be able to see the raisins…”
Exactly. The problem with a static, infinite, filled-to-the-brim universe is detailed in Olber’s Paradox, where he posits that if such a universe existed, the night sky would be as bright as the sun with the glow of an infinite amount of stars. The truth is quite the opposite. We live in a universe where matter is a weird leftover. It’s mostly empty out there.
Carl Sagan once mused that “We are way for the cosmos to know itself.” But in that regard, our time is finite. As time drags on, stars will become more distant and move away from us at the speed of light. We will never see them. Astronomers in the distant, distant, distant future will gaze up at a dark sky, and without any other galaxies as a frame of reference, will assume that there never was anything else in the universe aside from us. It will appear to them as a dark lonely place, filled with nothing.
Cosmologist Lawrence Krauss once said facetiously in a lecture, “We live in a very special time, the only time we can observationally verify that we live in a special time.” He’s more right than he may give himself credit for.
I’ll get you a dustpan.
Maki opens up a whole lotta cans each containing a whole lotta worms with this post (and in between the lines of each concept lies a million nerdgasms), and I have every intention of revisiting some of these concepts in detail later. Suffice to say what he says given an infinite amount of space is true (I’ve seen it!). I mean there would by definition be an infinite amount of ‘parallel’ earths here in a single universe without the need to imagine alternate ones (even that shitty one from Sliders where the only thing different was that in that world green lights meant stop and red lights meant go). The real question as pointed out, is in the infinity.
Allow me to throw some crazy numbers at you, so you may glimpse that which boggles our minds and sends our imaginations soaring. Our universe is 13.7 billion years old. More specifically that is when the Big Bang occurred, since recent observations point towards an interesting ripple in the background radiation that might reveal possible evidence for multiple universes, which makes me pee a little. The observable universe is 93 billion light years in diameter. That’s 41 decillion cubic light years of real estate, containing 30 sextillion to a septillion stars and 80 billion galaxies (Fair enough if you can even understand what that means. Personally I’ve never even counted to a thousand and mentally the difference between a thousand and a million is ‘it’s big’ and ‘its quite big’. Try to conceive of a septillion and-oh boy, yep, my eyeball just fell out).
Now take into account cosmic inflation (starting at 10-37 seconds after the big bang) the full current universe can be assumed to be around 1023 times larger than the observable universe. That’s- that’s just, ugh, it’s just huge ok?! Now realize that there is so much space between just the planets of our own solar system that we cannot even build a scale model of it indoors.
Saying we’re mere ‘motes of dust’ is grandiose!
The scale of the universe is enough to send any contemplator into a numinous frenzy. A frenzy that may leave you humbled, knowing that you can never reach the infinite, or elevated, understanding that through it’s light, the infinite, in one unbroken line that started at the beginning of time, has already extended out and touched you.
This post was brought to you by Osmium (Os).
UPDATE: A brilliant question was posed that I, myself, had completely missed. Jalais asked, “…if the big bang occured 13.7 billion years ago, and the diameter of the observable universe is 93 billion light years, then wouldn’t some matter at some point had to have travelled faster than the speed of light to allow such an expansive universe?”
The answer is “YES, BUT…” only in a universe where spacetime is flat. Flat space would mean that the universe is actually only 13.7 billion years old, because that’s what we can see. The problem is that space is not flat, it’s curved and expanding. It’s okay, it’s totally confusing. But Ethan Siegel on Scienceblogs has an excellent visual explanation of this very same question. Thanks for the question!
Research for this article comes with HUGE thanks to Astronomy Cast (Episodes 77, 78, and 79) and a brilliant lecture by Lawrence Krauss, which I have embedded below. It’s a great talk that goes into far more detail than I could ever hope for.