5 Impossible Questions About The Universe (And Their Answers)
Twenty thousand years ago, a circle of cavemen looked up at the stars and Moon, grunted, and pondered what it all meant. Then a salivating jaguar leaped out of the dark and mauled them. So count yourself lucky that you live in an era of near-limitless understanding and jaguar-free environments, when these questions can be scientifically explored—and even answered, often in a surprising fashion.
Is The Universe Infinite?
The universe, if you haven't heard, is pretty big. But is it infinite? That seems like an unanswerable question, though NASA's ingenuity has again humbled humankind and reminded us what piddling little insects we really are.
NASA's Wilkinson Microwave Anisotropy Probe (WMAP) measured the age of the universe at 13.77 billion years, and it took a baby picture of the universe, known as the cosmic microwave background (CMB). It's the oldest picture you'll see today, or ever. It shows the origin of every thing that ever was, is, and will be. This image, to reiterate the monumentality of NASA's accomplishment, captures the electromagnetic afterglow of the Big Bang, showing the universe as it was only 375,000 years after it sprang forth from whatever primordial state previously existed, or maybe didn't exist:
The blotches display minute temperature fluctuations that seeded the universe with its current configuration of galaxies. This Big Bang energy exists today as kind of a thinned cloud of radiation, pervading the cosmos literally everywhere we look.
It also allowed scientists to tease out the universe's shape, size, and potential fate. They did this by measuring the size of the bright spots in the CMB. A useful way to figure out the shape of something too big to look at is to draw a triangle on it and zoom out, to see whether that triangle lies flat or if its sides curve. Zooming out on the universe is impossible, but visualizing a big triangle and measuring its sides isn't.
If the angles add up to more or less than 180 degrees, then space-time is either sphere-shaped and finite or saddle-shaped and infinite. Alternatively, if the angles equal 180 degrees, then that's just a regular, flat triangle, and the geometry of space is flat and infinite.
According to WMAP measurements, we are indeed living inside a flat and infinite universe. This suggests its ultimate fate is a big freeze. Space-time just keeps expanding until it eventually becomes as inconceivably cold, thin, and empty as a $9 bowl of Panera soup.
Does "Nothing" Exist?
The macroscopic world plays by the somewhat logical natural laws of the universe. But at the smallest scales, the subatomic quantum world completely upends our understanding of, well, everything. Including our concept of "nothing." "Nothing" seems pretty simple: no things. But quantum (il)logic flips it the bird.
What we perceive as empty space is constantly writhing with fluctuating fields and ghostly "virtual particles" that exist for infinitesimal periods, like transient bubbles in a quantum foam. So even if you took a perfectly sealed box, hoovered all the particles from it, then booted it from a spaceship and left it to tumble forever through the black abyss, the inside of that box would be alive with quantum happenings.
Scientists can't directly observe these virtual particles. But their effects are observable, through the Casimir effect, named for Dutch physicist Hendrik Casimir. In 1948, he posited that two metal plates extremely close to one another will be forced together by the virtual particles (which also act as waves) that form on either side of the plates and nudge them together. Half a decade later, his theory was confirmed.
But wait, doesn't this whole something-from-nothing violate natural energy conservancy laws? Well, kind of. The quantum guidelines state that energy doesn't always have to be conserved, as long as the violation only happens for a very short period of time. And since energy and matter are the same, the itty-bitty virtual particles can enjoy an ever-so-brief moment in the sun before rejoining the realm of ghosts and darkness.
Can We See An Atom?
Atoms aren't as indivisible as once thought, but one thing's certain: they're so unimaginably tiny that we can never hope to glance them with the naked eye. Or can we?
That right there is a strontium atom in an ion trap, which we think is the same device that the Ghostbusters used to catch Slimer. The positively charged strontium is held in place by an electric field produced by four electrodes, situated less than 0.08 of an inch apart. You're actually seeing photons that the atom emits, since the actual neutrons and stuff would be much too small to see even at this scale, but it's still an isolated atom, visible without any kind of microscope.
The photo was devised and taken by the University of Oxford's David Nadlinger. He traps atoms all the time for his quantum computing research, which will one day deliver us quantum computers that could filter through obscure porno searches in a fraction of a fraction (of a fraction) of a second.
Nadlinger wanted to visualize an atom and offer us a "wonderfully direct and visceral bridge" between the logical, respectable macroscopic world and the wild, wacky quantum world, where subatomic particles cavort drunkenly. Visualizing a single atom, even a relatively beefy strontium atom with 38 protons, is insane given its mind-warpingly insubstantial size: billions would easily fit inside a red blood cell.
It had to be zapped with a blue-violet laser, so it could absorb and re-emit that light, making it visible through a long-exposure photograph. So what we're really seeing is the soothing glow of laser light being re-emitted from the atom. But hey, tomato tomahto.
What Does Temperature Really Mean In Space?
Picture the following scenario. Your colony is hurtling through space, destined for a far-off planet where you'll be free to practice polygamy and worship the glorious space rat without fear of persecution. Suddenly, you realize you're approaching a cloud of interstellar gas that's glowing furiously at 4 million degrees. But fuel supplies are running low, thanks to an unadvised decision to stop at Tau Ceti for flamin' hot Cheetos. The solution? Smash your spacefaring, nuclear-powered Mayflower right through that ominous gas cloud.
See, that gas has a high temperature, but there's a difference between temperature and what we think of as heat. Temperature is the average energy in each molecule. But when you're worried about getting fried, you're really thinking about energy density, or energy per volume. Since space is mostly empty, with just a few lonely particles flitting about, high energy per particle doesn't mean high energy density. So that cloud isn't all that "hot." You can pass through it without becoming space-barbecue.
The same holds true at the other end of the temperature spectrum. Say you're jettisoned into space, possibly after a mutiny or a HAL-like AI malfunction. Sure, you'd suffocate. But you wouldn't freeze, at least not for a while.
As Harvard puts it, space has no temperature. Not in a thermodynamic sense, at least, which states that temperature is a function of heat energy in matter, because space has almost no matter.
The abject lack of matter dramatically slows heat transfer between your insignificant body and the inky void. A vacuum is actually a hell of a good insulator. You'd have between 12-26 hours before you're frozen, giving you plenty of time to transmit your will to Earth and curse the mutineers who left you in such a lurch.
How Is Space-Time Expanding Faster Than The Speed Of Light?
As the universe continues its unabated and ever-quickening expansion, far-flung galaxies look like they're receding from us faster than light. They're retreating from us (and from every other point in the universe) at a rate that increases with their distance from a place. Pick any place you want—the universe has no center. The best way to visualize it is to imagine that all galaxies are flying apart as if on the outer surface of an inflating balloon.
But space isn't expanding at a speed, it's expanding at a speed-per-unit-distance. And oh man is it hauling ass: A galaxy that's one megaparsec (3.26 million light-years) from us appears to be zooming away at a rate of 42 miles per second. And that rate increases with distance. So something two megaparsecs away appears to be receding at 84 miles per second, and for each additional megaparsec, you tack on another 42 miles per second. If we look at something that's far enough, it's seemingly fleeing at a rate greater than the speed of light.
Really though, it's space-time itself that's moving, or expanding. Not that it's expanding into anything, like an empty space, because nothing exists other than the universe itself. It makes more sense the less you think about it.
This reveals another cosmic quirk: Local cosmic laws may not always agree with the happenings on the other side of the universe. Local laws are ruled by Einstein's special relativity, but the far-off reaches are governed by general relativity, developed by … also Einstein. In general relativity, there are no set, preferred, or official reference points—everything is relative.
So since there's no inertial reference frame, space-time can seemingly violate whatever speed law it wants, because it isn't "expanding with respect to anything outside of itself," since nothing outside of itself (the universe) exists. Alternatively, here's how it's explained by astrophysicists in countless space shows: Yes, there isn't any thing that can move faster than light, but space-time ain't no thing.
Furthermore, a person (or tentacled slime-monster) in those faster-than-light-receding galaxies wouldn't notice anything odd going on in their vicinity. But looking out, they'd see the same thing all other sensate beings would see: the galaxies receding at ever-increasing rates with distance.
So far-off future beings, be they cyborgs, energy clouds, or wookies, will inhabit such a stretched-out universe that they'll seemingly be all alone, glimpsing only empty darkness in every direction. And finally, they'll have some peace, and get around to finishing that book.
Top image: David Nadlinger/University of Oxford