The Darkness of Matter and Energy
A novelist must have a decent grasp of facts -- or current theories -- in order to write credible fiction.
Dark matter. Dark energy. Intriguing theories I’ve long read about. As I began thinking about the Resurrection, a new thought came to me about these two mysterious forces. The thought required me to dig more deeply into them for my ideas to stand up.
Fiction works when built on facts and theories.
One Fact, Two Theories
Crudely speaking, the only fact we know is that the universe is expanding but not in the way one would expect.
To explain this fact and some other puzzling aspects of the universe, theoretical physics postulated dark matter and dark energy.
Dark matter acts like matter. It creates gravitational forces that would explain the movement of galaxies’ outer bands.
Dark energy is the force that’s expanding the universe.
Dark energy acts like energy. Well, not like matter anyway. Is it Einstein’s cosmological constant? Is it or is dark matter a particle — WIMPs or weakly interacting massive particles — or large astronomical objects like planets or dwarf stars — MACHOs or massive astrophysical compact halo objects? According to CERN, the WIMPs’ proponents are dominating the discourse on what dark matter is.
Wimps over machos, I kind of like that! It reminds me of Jesus calling for words over swords. Just as WIMPs contain more power than MACHOs, so do words over swords — or guns in modern parlance. (In case you’re wondering where Jesus eschewed swords…it’s when Peter sliced off a servant’s ear, and Jesus rebuked Peter. And it’s inherent in Jesus never using weapons like swords, whips, lashes, or torture; but only used words and actions that didn’t physically harm anyone. I can’t say psychologically because he certainly upended a lot of people’s lives and preconceptions. But I digress.)
Dark Matter
The Perimeter Institute for Theoretical Physics created a short video explainer on dark matter. Katie Mack narrated it; she’s the Hawking Chair in Cosmology and Science Communication.
Dark matter is made of something entirely different from standard atoms and molecules. Visible matter of atoms and molecules comprises only 15 percent of all mass. When astronomers discovered spiral galaxies weren’t spraying stars outward from their outer bands and were not rotating slower at the very outer edges (due to being beyond the rotational gravitational forces of the galaxy’s centre), they realized something existed that they couldn’t see. This something made the outer stars circle a galaxy’s central bulge at a constant pace. Astrophysicists call this outer band a halo and the gravitational force in it, dark matter. Every halo around every galaxy shares a common structure and a common shape. The universal density profile.
Universal density profile: No matter a galaxy’s shape and size, all halos share a universal density profile. “[Halos] first form with a central ball of density then slowly over time accumulate more dark matter particles.” Paul Sutter on history of structure.
The Untouchable Mass
Astrophysicist Paul Sutter says that dark matter must be cold, collision-less, and abundunt. It makes up 85 percent of matter.
Cold: moves slowly compared to speed of light;
Collision-less: doesn’t interact with photons;
Abundant: it’s everywhere; it streams through everything and everyone. It can because it doesn’t interact with itself or us.
Dark matter is untouchable.
When we touch, we feel an electromagnetic force, the force photons carry. As I discussed earlier, photons are both particles and waves. We see photons in the visible electromagnetic spectrum, but they also occur in the spectrum beyond what we can see.
Apparently, dark matter doesn’t interact with photons. Think about it, dark matter is invisible. Cosmologists don’t just use sensors that detect only the visible spectrum, but the entire known electromagnetic spectrum from radio waves at the low-frequency end to gamma waves at the high-frequency end. Yet they can’t “see” it with all our current detecting telescopes and the like. So they have to use indirect methods to detect it.
Janna Levin says that neutrinos — which also don’t interact with us, which feature I used in my novel Time and Space — is a form of dark matter. But neutrinos are not heavy and abundant enough to explain the whole of dark matter. She says the surprising part is “that it’s so hefty.”
Does dark matter explain the asymmetry of matter and antimatter — that there’s a slight bias towards matter over antimatter (which is why there’s a universe — if matter and antimatter were equal in abundance, they’d annihilate each other)? Levin says we don’t know.
If dark matter “doesn’t do electromagnetism,” then it can’t collide with us or with itself. It’s untouchable.
It creates gravity but doesn’t create pressure — no electromagnetic force. In this way, it brings atoms and molecules, visible matter, together without making objects touch each other.
Together without pressure. There’s a metaphor in that.
“Something that acts exactly like a new invisible particle is needed to explain the data.”
Since that something hasn’t been discovered and is unknown, it opens up the possibilities for my novels. I won’t be writing my idea here, but developing it in Plottr and Scrivener. It’ll be in the background and explained, perhaps in novel 3…
Dive in to my trilogy and you’ll eventually find out!
Here’s Ars Technica with Paul Sutter’s longer explanation:
Dark Energy
Meanwhile, we have dark energy, just as invisible, even more puzzling, yet apparently interacting with dark matter.
In a nutshell, dark energy is accelerated expansion of the universe.
Some espouse it’s the cosmological constant like the speed of light is a constant. It exists and expands the universe, it has tension and a repulsive effect, and that’s about it…so far as theoretical physicists know. No one knows how to explain it physically or how to interpret it.
Dark energy is even harder to detect than dark matter because it’s a subtle effect that happens across vast cosmic space and vast timescales. But according to Paul Sutter, it’s the most powerful and most important component in the universe today.
Dark energy doesn’t change with time. It’s a constant.
Five billion years ago dark energy overtook dark matter in density because dark energy is a constant while matter density dropped exponentially over time and continues to drop. When Sutter explains this, he didn’t say if this is all matter, visible and dark, or only visible matter. He did say electromagnetic radiation density dropped exponentially and is lower than matter today.
The Future Could Be Weird
I think the biggest obstacle to understanding dark energy is being unable to see into the future. How will galaxies and the universe expand into time? We can only look to the distant past and compare it to the present to predict the future. But if Benjamin D. Wandelt is correct, and the future is weird, the past and present could mislead us about the future.
Wandelt, theoretical physicist, explained to Sutter that they don’t know how dark energy relates to fundamental physics like general relativity and quantum mechanics. And then he said something that widened my eyes and made me grin. Talk about helping out an author with her novel ideas!
“…in a universe where quantum mechanics also exists, quantum mechanical fluctuations can produce weird things. You can have a wall, and a particle that’s on one side of the wall can suddenly appear on the other side of the wall. So fluctuation. Now, if you have an infinite amount of time and an infinite amount of space, weird things can happen and will happen. Suddenly, you can have the appearance of a whole fully formed planet, just fluctuating out of nowhere. In principle, you can actually have a new beginning.” Wandelt.
Huh. He said it’s called the “Boltzmann brain scenario.”
So instead of the empty universe that an infinite future of expansion is predicted to bring, you’ll have random fluctuations popping up new planets (and new galaxies?) out of nowhere.
An earth with everybody on it where we remember our history.
Dynamically Linked Dark Matter and Energy
Dark energy creates volume, that is, space as it expands the universe over time. Sutter says dark energy increases as the universe ages, yet he’d said earlier dark energy is a constant. So how can that contradiction exist? As the universe expands, dark energy’s tension and repulsive effect increase. The repulsive effect is what pushes the galaxies apart. But does that mean there’s more dark energy? Couldn’t it mean that as the density of matter decreases, the effect of the same amount of dark energy increases? It’s all questions and theories!
Meanwhile, an astrophysicist, Lu Yin, at the Asia Pacific Center for Theoretical Physics in South Korea, studied a model of interacting dark matter and dark energy. This model of evolving dark energy coupled to dark matter can potentially explain the 21-cm neutral hydrogen radio signal from the formation of the first stars and galaxies.
“the interaction between dark matter and dark energy triggers the formation of stars and galaxies to occur earlier than it does in standard cosmology, which creates a stronger 21-cm signal.” Dynamical dark energy might explain strange 21-cm signal. Paul Sutter. On phys.org.
In this dynamical model, dark energy and dark matter co-evolve and keep each other in check.
One More Video
Katie Mack narrates a shorter “explanation” of dark energy but doesn’t include this dynamical model:
“Understanding dark energy is a great place to find new physics. It’s either a new energy field in the universe. Or it’s something that can revise our understanding of quantum physics.” Katie Mack.
All of this gives me an in, in my fiction. Heh.