Dark Matter and Dark Energy
I hijacking me own newsletter for a little science writing. My science knowledge is shallow, but I am interested by astronomy and astrophysics to the extent that an educated member of society should be. Two of the most recent major discoveries in astrophysics are the discoveries of “dark matter” and “dark energy”. The astrophysicists who coined those names did no one any favors because they gave license to every lazy TV and film writer to use them as plot points in their productions. Because they are mysterious (literally we don’t know what they are), they make good plot devices.
So what the hell are they then?
Astronomers have never directly observed dark matter or dark energy. They’ve only been observed in their effects. In the late 70s, astrophysicist Vera Rubin was looking at the rotation of galaxies. We’ve known since the times of Kepler and Newton that things further out from the gravitational center of a system (for instance, our solar system) tend to move slower as they revolve. The outermost planets take the longest period of time to revolve around the sun. What Rubin was looking at were galaxies. The stars furthest from the center seemed to be moving much faster than would be predicted by theory. Her conclusion was that the matter we could see in a galaxy was only a small percentage of what was there (because according to the theory, the velocity of the revolution was related to the mass of the system.) We can see a lot of matter in the universe—it glows, fortunately. Stars, galaxies, dust—it all gives off some electromagnetic energy—light, radio waves, high energy photons, etc.
Scientists proposed all kind of explanations for the invisible mass that caused galaxies to spin faster than theory predicted, but one by one, all those proposals were proven false. In the end, we have evidence that around every galaxy in the universe is a penumbra of matter that does not emit light or radio waves and does not interact with light. This matter has mass but is otherwise invisible and does not interact with ordinary matter (you, me, the sun, and everything we can see or detect in the universe). Dark matter is therefore believed to be a totally different kind of matter, and the only property that we know it has is mass. Things with mass are affected by gravity. So all that extra velocity that Rubin observed was being goosed along by a ghostly, invisible stuff that have weight.
(This is a black rectangle, but it’s what I imagine that both dark matter and dark energy look like.)
That’s fascinating to me, and I love the fact that we didn’t discover it until I was in high school. And subsequent calculations have shown that the mass of the dark matter is far greater than the all the visible matter—the billions of galaxies that make up the visible universe.
Dark energy is even weirder. After the big bang brought the universe into existence, matter started spreading out. And the thing is that it wasn’t just matter being blown out into empty space. Space itself was expanding. I don’t really understand this, but people smarter than me do. This was discovered in the 1920s. It was thought that the expansion of the universe would eventually slow and possibly turn into a contraction due to the effect of the gravity of all the matter in the universe. Imagine a ball being thrown up in the air that decelerates and is eventually pulled back down to Earth by it's gravity.
But what astrophysicists discovered in subsequent decades was that not only was expansion happening, but it seemed to speed up the further away the observed object (usually a galaxy) was from us.
What appears to be happening is that as more space is formed in the gaps between stars and galaxies. something in that space is pushing everything further apart, at fast and faster velocities. We call it “energy,” but really, we have no idea what it is. There are all kinds of theories, and I suspect that over the next few decades of astrophysical observations, we may learn more about these two massive and unknown features of our universe. We only proved that the universe was expanding faster in the 1990s. All of this is pretty cutting edge.
But despite its obscurity, the phrases dark matter and dark energy were quickly adopted by the creators of science fiction filmed entertainment as cool-sounding explanations for anything. For instance, in the Marvel Cinematic Universe, dark energy is something that extremely powerful beings can harness for their own uses. In The Avengers, Thor returns to Earth after the the Bifrost, a kind of road through space connecting various worlds, has been destroyed. Loki asks him, “With the Bifrost gone how much dark energy did the Allfather have to muster to conjure you here?” Dark matter has shown up all over the place in science fiction movies and TV shows. The fuel used by the spacecraft in Futurama is dark matter. It shows up in Star Trek, The X-Files, Final Fantasy V and many, many others.
None of these pieces of entertainment is meant to be especially accurate as far as the science goes. They’re for fun, not to educate viewers. The problem with that is that, in the case of dark matter and dark energy, they only became widely accepted explanations for what astrophysicists were observing in the past few decades, and even so, we have no idea what they are. Not surprisingly, they become these vessels that the creators of science fiction entertainment can pour all their science fiction mumbo-jumbo into.
I’m OK with that, but I do appreciate it when creators try to get the science right and save the mumbo-jumbo for something outside our experience. The Expanse (both the series of books by James A. Corey and the Amazon TV adaptation) try to keep the future space-faring human society pretty grounded. In the universe of The Expanse, we can’t travel faster than light, and we are able to travel within the solar system because of something called the Epstein Drive—a piece of technology that doesn’t currently exist. When we have contact with aliens, at first it’s because we accidentally discover a substance that the baddies of the series call the “protomolecule,” which some very advanced civilization left on an outer moon. We don’t have to understand the protomolecule—just understand that it was produced by a civilization much more advanced than our own. I guess Corey (which is the pen name for two writers in New Mexico) or the television producers could have called in “dark matter",” since it is a mysterious, Deus ex machina substance. But since we do know something about that dark matter does not interact with visible matter except by having a gravitational field, it would not have made sense for our future protagonists to find some alien “stuff” that was dark matter.
Another example of a science fiction work that tried to be realistic in terms of what was known at the time it was created is 2001: A Space Odyssey (1968). It was created before dark matter or dark energy had been discovered or widely accepted in the fields of astronomy. But the more earthly technology is all pretty believable. No breaking the laws of physics, except by the creators of the monoliths.
But if a science fiction story takes place in the distant future, like Dune or Foundation, I am willing to accept all kinds of science fiction “magic.” It is easy to imagine that people in the future will have cracked things that seem utterly impossible now, like fast-then-light travel or communication. They come up with their own new lingo for these things. But writers and producers of science fiction now—please stop using “dark matter” and “dark energy” as plot points. To me, it just comes off as pretentious.
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