How to identify this cluster of universes?
March 12, 2023 8:35 AM Subscribe
I've got a story brewing that includes interdimensional travel and I'm trying to identify groups of universes whose physical constants are close enough that people from one will survive in the others. The obvious approach would be to give a selection of constants to a certain precision for each universe but that's sort of ungainly. Ideas?
Response by poster: The setting includes a robust collection of universes who have trading and cultural interaction. Basically how countries interact in the current world but physical laws sometimes differ.
posted by Tell Me No Lies at 9:06 AM on March 12, 2023 [1 favorite]
posted by Tell Me No Lies at 9:06 AM on March 12, 2023 [1 favorite]
Maybe something like "degrees of variation"? You can survive in universes fairly similar to your own, but the farther away you go in terms of variation, it becomes harder and harder to survive. A universe very similar to ours, you might only have to worry about diseases that your body never evolved resistance to, but one where all the proteins spiral the wrong way, you might have more trouble, and the universe where everything is made of cotton candy, including the atmosphere, is lethal.
posted by The otter lady at 9:31 AM on March 12, 2023
posted by The otter lady at 9:31 AM on March 12, 2023
So.. I'm not sure how this works in any real sense without a deep-dive into physics, and also making some serious concessions.
1) I'm part of our universe. You're part of our universe. This computer is part of our universe. In fact, I think it's often better to frame this as: I am universe. In the same way you'd say, "This rock is granite" or "this liquid is water". I'm universe. Mass and energy are conserved. If I suddenly hopped over to another universe, that conservation would be broken -- I'm universe, and I just blipped out of me. This entire existence now needs to reckon with the fact that a bunch of its energy just disappeared. It's a problem!
2) You could get around this if you instead decided that mass and energy are conserved within the multiverse. In fact, if you're at the level that you want your constants to make sense - as in, you want something approaching mathematical rigor in the setting you're building - I think this is the only way this works. OR, you have to equip everything that comes from one universe and travels to another with "reality stabilizing tethers" or something that multiversally keeps them connected to their existence and allows them to maintain conservation. You would need to do this for every bit of energy that makes the trip. Not just people, but like, the quarks that make up the protons and neutrons in every atom of the spaceship/whatever.
3) Constants are important because literally everything that happens in existence is an emergent property based on some of those basic constants. If you change one tiny thing in the underlying assumptions, the rest could be wildly different in wildly unpredictable ways. If you change the speed of light you are also changing, like, how much energy it takes an atom to hold together. If I go to some other universe (somehow), even though I'm fine, if oxygen atoms have fundamental different properties, my body can't do anything with that. Maybe I die slowly because they're poison, maybe I suffocate because I can't do anything with them (wrong size/weight/energy capacity), maybe they try and bond with Universe A-oxygen already in my blood and undergo fusion and now I'm a star, baby! For like a fraction of a second and then I'm dead.
4) Suggestion: linear algebra framework. Have some kind of travel network that translates things from one universe to another. Hand-wave this as requiring tremendous amounts of energy for each hand-wavey constant change. Universes with "small" constant changes (again, this doesn't really make sense, but let's go with it) require less energy to move between, making it easier/more convenient for those universes to interact with each other. It also sets you up for some good long-term storytelling, allowing your characters to make pretty far-from-home journeys if they essentially "get used to the water" and slowly move into more and more divergent universes. It'd be too difficult to go from here to a universe where the speed of light was half of what it is here, but maybe if you went to one where it was 0.0000001% different, and then 0.00001% different from that, and so on, you could wind up in radically different spaces. Everything that travels universes has to undergo and/or maintain a particular matrix transformation to be made part of the new environment. I'm not suggesting that this is the literal device, just, uh, a literary device. A way to think about it (and for one protagonist to explain to another so your readers are clued in).
5) You can then decide whether this travel works by stabilizing continuity with an active measure (tethers), or if you are doing Multiverse Alchemy and preserving equivalent exchange by transforming Universe A item into Universe B, and then an equivalent amount of energy is moved from Universe B into Universe A.
The only author I know who does this kind of stuff is Greg Egan. If you haven't read his work, I highly recommend checking out Diaspora (standalone novel) and his Orthogonal trilogy (which changes a mathematical sign in one fundamental equation and the universe is radically different in how it operates, and he's still probably hand-waving stuff, but it's the stuff so far above my head I'm okay with it).
posted by curious nu at 11:14 AM on March 12, 2023
1) I'm part of our universe. You're part of our universe. This computer is part of our universe. In fact, I think it's often better to frame this as: I am universe. In the same way you'd say, "This rock is granite" or "this liquid is water". I'm universe. Mass and energy are conserved. If I suddenly hopped over to another universe, that conservation would be broken -- I'm universe, and I just blipped out of me. This entire existence now needs to reckon with the fact that a bunch of its energy just disappeared. It's a problem!
2) You could get around this if you instead decided that mass and energy are conserved within the multiverse. In fact, if you're at the level that you want your constants to make sense - as in, you want something approaching mathematical rigor in the setting you're building - I think this is the only way this works. OR, you have to equip everything that comes from one universe and travels to another with "reality stabilizing tethers" or something that multiversally keeps them connected to their existence and allows them to maintain conservation. You would need to do this for every bit of energy that makes the trip. Not just people, but like, the quarks that make up the protons and neutrons in every atom of the spaceship/whatever.
3) Constants are important because literally everything that happens in existence is an emergent property based on some of those basic constants. If you change one tiny thing in the underlying assumptions, the rest could be wildly different in wildly unpredictable ways. If you change the speed of light you are also changing, like, how much energy it takes an atom to hold together. If I go to some other universe (somehow), even though I'm fine, if oxygen atoms have fundamental different properties, my body can't do anything with that. Maybe I die slowly because they're poison, maybe I suffocate because I can't do anything with them (wrong size/weight/energy capacity), maybe they try and bond with Universe A-oxygen already in my blood and undergo fusion and now I'm a star, baby! For like a fraction of a second and then I'm dead.
4) Suggestion: linear algebra framework. Have some kind of travel network that translates things from one universe to another. Hand-wave this as requiring tremendous amounts of energy for each hand-wavey constant change. Universes with "small" constant changes (again, this doesn't really make sense, but let's go with it) require less energy to move between, making it easier/more convenient for those universes to interact with each other. It also sets you up for some good long-term storytelling, allowing your characters to make pretty far-from-home journeys if they essentially "get used to the water" and slowly move into more and more divergent universes. It'd be too difficult to go from here to a universe where the speed of light was half of what it is here, but maybe if you went to one where it was 0.0000001% different, and then 0.00001% different from that, and so on, you could wind up in radically different spaces. Everything that travels universes has to undergo and/or maintain a particular matrix transformation to be made part of the new environment. I'm not suggesting that this is the literal device, just, uh, a literary device. A way to think about it (and for one protagonist to explain to another so your readers are clued in).
5) You can then decide whether this travel works by stabilizing continuity with an active measure (tethers), or if you are doing Multiverse Alchemy and preserving equivalent exchange by transforming Universe A item into Universe B, and then an equivalent amount of energy is moved from Universe B into Universe A.
The only author I know who does this kind of stuff is Greg Egan. If you haven't read his work, I highly recommend checking out Diaspora (standalone novel) and his Orthogonal trilogy (which changes a mathematical sign in one fundamental equation and the universe is radically different in how it operates, and he's still probably hand-waving stuff, but it's the stuff so far above my head I'm okay with it).
posted by curious nu at 11:14 AM on March 12, 2023
Anathem also included this idea, although it didn't go into nitty-gritty details.
It depends on how you want this to work, but you could give each universe a "constants score." So, for example, in Universe A, Plank's Constant has a value relative to some baseline (eg, the average value for this constant in all known universes) of 1.001, and an electron volt has a value of 0.998, etc. You'd take the average of all these relative values and say that Universe A has a constants score of 1.0002 or whatever. And you'd say that as long as two universes are within 0.001 of each other, travel is possible. Or maybe people are really sensitive to EV differences, so you'd use the cube of the relative score to weight it more heavily.
You'll explain this once on p. 30 and then just refer to the constants score. Maybe name it after the person in the story who came up with the scoring method.
posted by adamrice at 12:06 PM on March 12, 2023
It depends on how you want this to work, but you could give each universe a "constants score." So, for example, in Universe A, Plank's Constant has a value relative to some baseline (eg, the average value for this constant in all known universes) of 1.001, and an electron volt has a value of 0.998, etc. You'd take the average of all these relative values and say that Universe A has a constants score of 1.0002 or whatever. And you'd say that as long as two universes are within 0.001 of each other, travel is possible. Or maybe people are really sensitive to EV differences, so you'd use the cube of the relative score to weight it more heavily.
You'll explain this once on p. 30 and then just refer to the constants score. Maybe name it after the person in the story who came up with the scoring method.
posted by adamrice at 12:06 PM on March 12, 2023
Maybe in a world in which this situation obtained, “people” (whatever sentient beings occupy the universes) would reach for a metaphor like “flavor” or “handedness” to characterize the incompatible sets of universes.
It might also be interesting to make the survivability non-reciprocal, analogous to blood type.
posted by staggernation at 12:35 PM on March 12, 2023
It might also be interesting to make the survivability non-reciprocal, analogous to blood type.
posted by staggernation at 12:35 PM on March 12, 2023
In stories of this type, a group of similar universes is usually referred to as a 'sheaf.'
posted by AugustusCrunch at 1:01 PM on March 12, 2023
posted by AugustusCrunch at 1:01 PM on March 12, 2023
trading and cultural interaction
In this case, as a reader, I’d be way less concerned about the hard (or even soft, hand woven) science of how the universes are interacting, as to the why - for relatively mundane things like faster than light travel or communication, it’s to make planet hopping and cultural interaction quick and human-scale comprehensible, for parallel universes it’s often to explore time interactions and the effects of choices. Trade & cultural interaction, even across wildly different non-parallel universes, still at its core comes down to “these different groups each have something the other needs or wants”, so maybe a really deep dive into what they’re exchanging and why would shed some light on the background mechanics necessary?
posted by Jon Mitchell at 1:36 PM on March 12, 2023
In this case, as a reader, I’d be way less concerned about the hard (or even soft, hand woven) science of how the universes are interacting, as to the why - for relatively mundane things like faster than light travel or communication, it’s to make planet hopping and cultural interaction quick and human-scale comprehensible, for parallel universes it’s often to explore time interactions and the effects of choices. Trade & cultural interaction, even across wildly different non-parallel universes, still at its core comes down to “these different groups each have something the other needs or wants”, so maybe a really deep dive into what they’re exchanging and why would shed some light on the background mechanics necessary?
posted by Jon Mitchell at 1:36 PM on March 12, 2023
Flavory for the handwavery: nondimensionalization is an actual handy way of thinking about systems. More euphonious reference, the Buckingham π theorem.
posted by clew at 1:40 PM on March 12, 2023
posted by clew at 1:40 PM on March 12, 2023
Can you make your world's "portal tech" that's naturally selective, i.e. it will take them a LOT MORE EFFORT to open a portal into somewhere that our physics are altered fundamentally, whereas the portals we open EASILY are the ones where the physics fundamentals are equal or largely the same?
posted by kschang at 6:18 PM on March 12, 2023
posted by kschang at 6:18 PM on March 12, 2023
I feel like governmental organizations tasked with explaining this to the public would be aiming for a pretty simple scheme that covers 95% of universes. Like you know the "color" of your universe, and there's a simple chart to memorize about which colors are compatible. People from blue and red can visit each other but not anywhere else. People from yellow/green/black can all visit each other, and can also visit red but not blue.
But of course the colors would be rough averages, and some individual universes on the fringes of each classification wouldn't follow the usual rules - causing annoyance. "Goddamn Google Maps keeps trying to route me through yellow, but I can't go to yellow, even though I'm green!"
And if your universe is among the unlucky 5% that doesn't fit the scheme at all, then you're stuck having to know all the details about the actual physical constants etc.
staggernation mentioned blood types above, that's the kind of thing I was thinking too. Or also the USDA food pyramid. A gross simplification, reasonably accurate for many people in a first-approximation kind of way, but with some serious bugs too, also not immune to politics, and eventually superseded by something hopefully better - as it had replaced the simpler system that preceded it. It might be interesting if you had a couple different systems in your universes, one on the way in and one on the way out.
As for the actual constants themselves, I kind of feel like it wouldn't be low-level things like the mass of particle X, but higher-level stuff like the contact angle that certain materials make with water? E.g. you wouldn't want to go to a universe where your cell membranes are hydrophilic, you'd collapse into a puddle of water. Or perhaps the temperature range at which the Krebs cycle functions. Or the speed at which electrical impluses travel through material X, below which some types of brains stop working.
posted by equalpants at 11:06 PM on March 12, 2023
But of course the colors would be rough averages, and some individual universes on the fringes of each classification wouldn't follow the usual rules - causing annoyance. "Goddamn Google Maps keeps trying to route me through yellow, but I can't go to yellow, even though I'm green!"
And if your universe is among the unlucky 5% that doesn't fit the scheme at all, then you're stuck having to know all the details about the actual physical constants etc.
staggernation mentioned blood types above, that's the kind of thing I was thinking too. Or also the USDA food pyramid. A gross simplification, reasonably accurate for many people in a first-approximation kind of way, but with some serious bugs too, also not immune to politics, and eventually superseded by something hopefully better - as it had replaced the simpler system that preceded it. It might be interesting if you had a couple different systems in your universes, one on the way in and one on the way out.
As for the actual constants themselves, I kind of feel like it wouldn't be low-level things like the mass of particle X, but higher-level stuff like the contact angle that certain materials make with water? E.g. you wouldn't want to go to a universe where your cell membranes are hydrophilic, you'd collapse into a puddle of water. Or perhaps the temperature range at which the Krebs cycle functions. Or the speed at which electrical impluses travel through material X, below which some types of brains stop working.
posted by equalpants at 11:06 PM on March 12, 2023
Interesting macguffin.
I guess some gateways have material jump across into local-universe edition, and that had gains in energy density or matter confusion that's stronger/lighter/thinner and an advantage, better than any that can be had in that cosmos
I guess some gateways let matter through as-is, but it's configurations that can't be made in their cosmos and so there's an advantage to be had from it. Some holds its advantageous form, some matter just dissipates and other matter traipses back to the gateway to its home cosmos.
Some gateways promise an earlier time offset since the big bang of their cosmos, and some lie about it.
Early transits developed a kind of hobo code and then a formal wiki. Trading didn't really take off until tests were developed to be sure of the integrity of claims made about a cosmos on the other side of a gateway. You trade because there's some material or energetic gains to be had, and mutual benefit can be arranged. Their reputation matters so that you both gain. Sometimes it takes a long chain of gains to be found so that one cosmos can reimburse their suppliers with mutual benefit.
Some gateways lie or can be manipulated to appear other than what they are, and some visitors checked inadequately, and serve as a warning to that who came after them.
Whatever is on the other side of that gateway, the wiki and guide say what physics test to do. Maybe the double-slit experiment doesn't vary, or this tuning fork rings differently, or water at measured STP boils for less latent heat, or nuclear waste becomes harmless in minutes ... there's a lot of macguffin to explore and to hide as Chekov's MacGuffin in resolving your story arcs.
posted by k3ninho at 5:02 PM on March 15, 2023
I guess some gateways have material jump across into local-universe edition, and that had gains in energy density or matter confusion that's stronger/lighter/thinner and an advantage, better than any that can be had in that cosmos
I guess some gateways let matter through as-is, but it's configurations that can't be made in their cosmos and so there's an advantage to be had from it. Some holds its advantageous form, some matter just dissipates and other matter traipses back to the gateway to its home cosmos.
Some gateways promise an earlier time offset since the big bang of their cosmos, and some lie about it.
Early transits developed a kind of hobo code and then a formal wiki. Trading didn't really take off until tests were developed to be sure of the integrity of claims made about a cosmos on the other side of a gateway. You trade because there's some material or energetic gains to be had, and mutual benefit can be arranged. Their reputation matters so that you both gain. Sometimes it takes a long chain of gains to be found so that one cosmos can reimburse their suppliers with mutual benefit.
Some gateways lie or can be manipulated to appear other than what they are, and some visitors checked inadequately, and serve as a warning to that who came after them.
Whatever is on the other side of that gateway, the wiki and guide say what physics test to do. Maybe the double-slit experiment doesn't vary, or this tuning fork rings differently, or water at measured STP boils for less latent heat, or nuclear waste becomes harmless in minutes ... there's a lot of macguffin to explore and to hide as Chekov's MacGuffin in resolving your story arcs.
posted by k3ninho at 5:02 PM on March 15, 2023
This thread is closed to new comments.
Another might be sort of - philosophically/existentially? Say the dimensional transport needs a great deal of information to transport you to an alternate dimension, and there’s some in-universe controversy as a result whether the transport is actually transporting you to a place, or creating it in order to be travelled to.
posted by Jon Mitchell at 8:53 AM on March 12, 2023