The Coming World of Magic

I was not too surprised to see an article titled U.S. millennials post ‘abysmal’ scores in tech skills test, lag behind foreign peers in today’s Washington Post. The article says that in a test of literacy, math and technological problem-solving skills, US millennials (defined as age 16-34) ranked very low against their peers in other countries no matter how the data was cut by race, gender, and education.

This ties to a recent revelation of mine. I have been coaching an FTC robotics team this year. The team has done well and has designed a very innovative robot. The boys on it are all bright, eager, and have learned a great deal. In many ways, they are much like me at that age: geeks fascinated by technology, computers, military history and so on. But there was one surprising difference: not one of them knew any programming.

There are kids out there at this age (15-16) who do know how to program. But in a sample of 5 hard-core geeks, not one knows how to code? I was rather shocked, to be honest.

But it comes back to a trend that the test cited in the article above gets at: users of technology do not necessarily understand it. Today’s technology with its ready games, images, social media, suck up a lot of the time. This has already had a noticeable effect on the reading of books. Less recognized is the effect it is having on the sorts of skills mentioned in the article.

If a teenager is spending an hour on social media and another few hours on gaming or surfing, that’s the same time in their busy lives they might have spent in the past reading, learning to program, learning how a radio works or fixing a lawnmower. It can lead to a generation of people who are savvy about navigating the web, have an innate sense of how a GUI should work, but have little idea of the technology behind it.

In the case of this particular study, the results are relative: the US scores low, other countries score high. Some of the distractions for US youth must be present for youth in other countries. This may mean that the scores have little to do with technological distractions but, then again, the US may be worse because it was an earlier adopter of the new marvels.

We’ll see how this plays out but for the science fiction author in me, it’s not hard to imagine a future where most of the world population has a superficial understanding of technology: they know how to order a pizza online or track down an old friend, but they have little idea of what happens behind the scenes. It’s not like 20 or 40 years ago, the average person understood the underpinnings of technology but if the geek portion of a generation isn’t learning how the technology works, then there may be very few technologists and very little innovation down the road.

From a story point of view where conflict is necessary to drive the story arc, one can imagine a future where the rich countries are complacent and comfortable in their technological cocoon but have lost the ability to create new technology. Or perhaps this is what happens to very mature civilizations: maybe Earthlings encounter a space-faring race where very few of the aliens really understand how their technology works, leaving them unable to react quickly enough to an aggressive, more flexible race (us).

It would be an interesting turn-around from the uber-dominant, militaristic alien races to have one that, while more advanced, is more like a clumsy giant, out maneuvered by a still agile humanity.

As to the article itself, I can’t say it is all doom and gloom for the US. These things always have a way of coming and going. What I wouldn’t advocate as a response, however, is more homework. I think homework has been over done. Free time to explore is what kids really need. And maybe incentives to understand their world better: maybe more tangible rewards for the ones who start writing or programming, ‘doing’, instead of soaking up all that lovely media out there.

To circle back to the title: if we do create generations of descendants who have no understanding of the technology in their bright and shiny world, they will essentially look to technology as magic.

Arthur C. Clark’s 3rd law is:

Any sufficiently advanced technology is indistinguishable from magic

I think most of us, when seeing it, imagine it applies to a less advanced race experiencing the technology of a more advanced race. But what if, instead, the technology of the advanced race appears to themselves as magic?

Space Wonders: Better than Traveling There

Just a quick gallery today of some of my newer pictures from Space Engine. I’m looking forward to addition of accretion disks around black holes and blue stragglers in globular clusters in upcoming updates. As in the earlier post, all images are exactly as captured in Space Engine, without any post processing, cropping, etc.

Warp Speed: How Fast do you have to go to get the Stars to Sail by?

In a star cluster orbiting the  milky way (Space Engine)
In a star cluster orbiting the milky way (Space Engine)

John Pyle’s post on Light Speed, Not so Much, reminded me about something I wanted to look into based on my Space Engine experience. In this wonderful simulator you can go anywhere in the universe with the engine kindly accelerating you to fantastic speeds, as necessary. As part of the experience, you get to experience the Star Trek warp effect: stars go sailing by all around you as a readout at the bottom of the screen shows your current speed. It might be km/s over a planet or AU/s in a planetary system. Between stars, you typically get to go parsecs per second (a parsec is 3.26 light years). Hop over to the next galaxy and you’ll be travelling at hundreds of kilo-parsecs per second. This is a good thing, because otherwise travel would be tediously slow.

One of the neat things about Space Engine is that it doesn’t just pop you over to your destination, you travel to it, accelerating and decelerating. You fly through dusty arms of galaxies, through nebula, globular clusters. As I mentioned stars zip by a la Star Trek. This got me to wondering: I think Space Engine has a pretty solid model of spatial relationships and velocity. Therefore, I can use it to gauge what Star Trek warp factor I’d need to be traveling to get the same visual effect of star motion that we’ve seen since the original series. Of course, I had a feeling the TV show was way off but it is fun to do the numbers.

First, I’ll use the newer series’ definition of warp. You can find a great definition of what warp factors mean at Star-fleet.com’s engineering department: Warp Factors Defined. At warp 5, you’re going 215 times the speed of light and at warp 9 you’re going 1516 times the speed of light. That’s pretty fast, right? Indeed it is but as the old cliché goes, space is really big. At warp 5, it’s 40 hours per light year. Not bad for the local neighborhood but not too zippy. At warp 9, it’s only 5.9 hours per light year, so several light years per day.

So what would the star motion look like? Fire up Space Engine, play around with your speed and… you’ve got to be going around a light year per second to start to notice much star motion. Pick a densely populated region like the heart of a star cluster and maybe you can get away with 0.1 light years per second. But at those speeds, you are just starting to notice star motion. If you really want to be seeing stars zip by, like in the opening credits,  you might be looking at 1 to 5 or more light years per second.

Even at warp 9.99, at 7912 times the speed of light, you’re crawling by at one light year per hour+, or ~4000 times slower than the speed you need to get the stars to zoom by. I’m not sure how to turn that back into a warp factor but since warp 10 is the max, it is something like warp 9.9999, perhaps?

This means that if you intend to use that cool “star gliding” effect in your own stories, you better be having your star ships travel much, much faster than they do in Star Trek, so fast that your ship could get to the Andromeda galaxy in a few days. That’s probably too fast for most science fiction stories, unfortunately. Put another way, the Star Trek apparent star motion isn’t really practical, although it sure does look cool.

Just goes to show that space is really, really big.

SpaceEngine: Go Anywhere in the Universe

Sunset on a Brown Dwarf
Comets around a Brown Dwarf

Along with the Universe Sandbox, here’s another great tool for the science fiction author: SpaceEngine. This fascinating program is still in beta, and a bit buggy, but to get an idea of what it can do, take a look at these pictures, all of which are unmodified screenshots. Most are from my son’s exploration over a few hours. The first two are my own effort after about 30 minutes of playing around.

Aurora on a Distant Planet
Aurora on a Distant Planet

Whereas Universe Sandbox is an orbital dynamics simulator, great for playing around with solar systems and disrupting them by blowing up a planet or shooting black holes through them, SpaceEngine takes a different route. It models a huge number of known astronomical objects, from every moonlet in our solar system, to nearby stars, globular clusters, nebula, galaxies, etc.

Gas Giant
Gas Giant and Galaxy

Where it really gets interesting is the vast number of astronomical objects for which there is no known data because where current observational data runs out, it creates the rest procedurally.

Ringed Waterworld
Ringed Waterworld

Pick a galaxy and fly into it. Find a star in that galaxy and zoom to it, visit its planets and moons, search for life, exotic planet rises, there’s really no limit. I’d consider some of these for cover art for certain classes of novels.

Over a Desert World
Over a Desert World

When poking around the universe can keep you busy for days, who knows what story ideas you might find?

Ice Moon orbiting gas giant in a binary star system
Ice Moon orbiting gas giant in a binary star system

SpaceEngine not only creates lovely visuals, it backs it up with  physical data: object mass, gravity, atmosphere, orbital period, mean temperature, even modeling presence of life. It’s fun if you just want to poke around alien worlds and its a dream come true for Science Fiction worldbuilders. Plus it has more lens-flares than the last Star Trek reboot!

An Alien Shore
An Alien Shore

Has anyone else given it a try yet? What do you think of the pictures from it?

Souls and Virtual Reality

poster for The Matrix
poster for The Matrix (Photo credit: Wikipedia)

You go to sleep and wake… as an elf in a tree-city much like Tolkien’s Caras Galadhon. Pretty cool, eh? You likely would experience angst over left-behind loved-ones. But how else might you react?

What fantasy reader hasn’t given this at least some thought? Myself, since as long as I can remember, I’ve spun daydreams, sometimes weeks long, of just such adventures. But what would I really think if suddenly transported to another world, maybe even in a different body? Sadly, I would be forced to alter my assessment of the chances that I’m living in a virtual world.

There has been a lot of discussion lately about whether all of us are presently living in a Matrix-like world. Some even go so far as to say it is likely that this is the case, probably because if there were virtual worlds, there would be a lot of them, therefore you’d more likely be in a virtual one than a real one. I’d like to see the analysis for those who posit this because while I think it is entirely possible, I don’t think it is all that likely.

My assessment would change, though, if fundamental elements of my current reality suddenly changed. And nothing is more fundamental than my body and the world I perceive. This is because while I think you can construct ways for people to move from one world to another or body swap (or both), and it’s an accepted fictional trope, in reality making such a move seems nearly impossible. How does one change universes? There may in fact be multiple universes but in no cosmology proposed by scientists is it very easy to travel between them. Under some theories, the other universes would not even have our laws of physics.

But even supposing you could make the leap, how do you pick out the cosmically insignificant speck of habitable space (not just a planet but the surface of that planet) and arrive at an appropriate velocity (an extension of my discussion under Teleportation and Momentum Matching.) I suppose you could posit universes that fork off our own and remain connected in some way but, even so, it still seems unlikely you could simply pop from one to the other without some sort of high-tech cocoon to protect you in transit.

Then, once arrived in the new universe, there’s all the issues of communicating there: do you already know the language? How is that shoved into your brain? And do the denizens appear human: our basic body plan may be likely, perhaps, but it isn’t likely that the other folks would be so human-like that we would find it desirable to be one of them. And what about atmospheric and microbiological compatibility? Not an issue if you get a new body but a big deal if your current one pops over to the new world. And a really big deal if the portal is bi-directional. I would be a lot less concerned about dragons ravaging our Earth and a lot more concerned about alien diseases doing the same.

On the body-swapping, how exactly do you move a consciousness from one body to another? It seems possible you could move memories, especially imperfect ones to a new body, but the actual consciousness? If you believe in souls you could imagine the soul moving along but there is no scientific evidence or justification for souls that I’ve ever come across. I suppose if the cranial cavity is the same in both skulls, you could move the brain and re-connect everything. That seems do-able. But a consciousness swap such as we’ve seen in Star Trek episodes? Cool to write, hard to imagine how that really works.

None of this is strictly speaking impossible but it seems extraordinarily unlikely to me. If I ever found myself in such a situation, I’d be forced to conclude that I am more likely a virtual entity and I was simply moved from one simulation to another. As discussed earlier, any virtual simulation is likely to have well-defined abstraction layers for speech, body perception/interface and so on. Re-targeting these to a new language, body, world, even physics system, is a small extension for any entities capable of executing a virtual world simulation that can fool us. Therefore, there is no practical barrier to moving a simulated consciousness to a new simulation. Now, that simulated entity might be very sad at the loss of his old friends and family or freaked out to the point of insanity if it suddenly found itself in a Cthulhu-esque squid body. But you can certainly imagine the transfer taking place without any messy issues of wormholes and hostile microbes.

In the end, I might not object to such a transfer, especially if it occurred at the end of a (simulated) life. But it would certainly raise fundamental questions about the meaning of life, my family and friends, and so on. These are not the sort of realizations those who run the VR show may want their VR entities aware of, as it would affect the simulation. But maybe they move people without full or any memories intact. Perhaps those who remember past-lives are simply remembering incompletely purged past-memories. If a simulated world is not complete, that is, if not all the entities are fully realized, than the fact that past-life recallers seem to remember a disproportionate number of historically “cool” lives (me, I was King Henry V in a past life), might actually make sense because in that case, any given VR entity was pulled from a limited pool of past people, which could, if the VR executor so chooses, be disproportionately higher stature folks.

One reason those who run a VR show may not want their entities aware of this is it raises the basic question of why? Is my entire life and all the pain and suffering simply for the entertainment of others? One plausible and morally acceptable reason might be for self-entertainment: we’re all astronauts on a million year journey to another galaxy and the simulations are a way to pass the time. But even then, during the simulation, you might not want to know you are in one. There are many other possibilities for the ‘why’ behind a virtual world.

For instance, imagine a future where synthetic entities have replaced organic ones. Some might argue the fate of humanity is to go extinct, the only question is whether we leave behind self-aware synthetic progeny. In such a world, the synthetics might wish to keep alive, for historical purposes or as a hedge against unknown threats, a simulation of their fore-bearers. Or perhaps, in order to “seed” synthetic consciousness with a good range of capabilities, they actually grow their consciousness in a simulation of organic civilizations. Maybe the childhood of a self-aware android is a life or two in a simulation of 21st century Earth. If I were creating synthetic entities, I might do exactly that. It’s not be a bad way to train a virtual entity’s neural network (or however it is technologically realized).

Back to the topic of souls mentioned in the title, if a soul is the “something” that makes a self-aware being unique, extracting that from an organic brain seems rather close to impossible to me. But extracting that from a simulated VR entity seems quite possible. Put another away, it may be that the only beings with souls are simulated beings. Therefore, the only way for life to develop to the point of having souls is for organic humans to create a virtual world with virtual entities, or create synthetic entities in real robot bodies whose consciousness could be moved from machine to machine. Or both: if you can have a synthetic entity running around a simulation, you could put the same being into a physical body to allow it to interact with the real world.

This leads to perhaps a disquieting thought: what if only synthetic entities are able to have a soul and an afterlife? Or what if we are all androids-in-training in the year 120,000 CE?

Climbing the Next Hill

Pixar: For the birds
Pixar: For the birds (Photo credit: Colin ZHU) Maybe they are scared of their next revision.

My revision of Shadow of the Archon finished, I updated my progress bar to show 100% this morning. I even left it there for a whole 30 minutes while I started on the next revision. Now, it’s back to 1%.

As I set out on another revision, I’m reminded of Nila’s post on Pixar Rule #18: “You have to know yourself: the Difference between doing your best and fussing. Story is testing, not refining.” Of all the rules so far, I think that one has had the widest range of interpretations in the comments section. I don’t think anyone really gets the ‘testing’ part but clearly there’s a worry about spending too much time on a project. Sometimes you have to move on.

I’m trying to be better with this project. After the first draft, as planned, I did a major revision and polish, then had some readers look at it as an ‘alpha stage’. Post that feedback (and some soak time while I worked on other things), the next part of the plan was to mark up a printed copy, revise it, do one more pass on-screen to ‘polish it’, before having another set of eyes on it. After that, we’ll see. I like the story but we’ll see what the feedback looks like.

As I reset my progress bar this morning, I was reminded of my school days: my fellow students and I worked up from 1st grade to 6th grade in elementary, from 7th to 8th in Junior high, from freshman to senior in High School and so on into college. It was bottom rung to top rung, with the reward being getting to start at the bottom again. I actually loved school so I don’t mean that in a negative way but it was funny going from high to low at each major step. Sort of like finishing a revision only to start another one (or a new first draft).

How to Make Time Travel Work

Cover of "Back to the Future"
Cover of Back to the Future

I’m talking about how to make it work in your stories, not how to build a time machine. Apologies if you are looking for engineering schematics.

Time travel has got to be one of the oldest tropes in fantasy and science fiction. Who wouldn’t want to go back and fix a mistake or just observe the past? Trouble is, basic time travel has, as we all know, fundamental paradoxes. What happens if you kill your grandfather or commit one of the endless variations? Yet, there doesn’t seem to be an end to time travel stories in sight, and, why not? They can be fun. Plus for TV shows, there’s the added bonus of getting to use all those cool historical outfits the studios have lying around.

While I usually groan at time travel, I have to confess one of my favorite Star Trek: Next Generation episodes is Yesterday’s Enterprise. And I still get a chuckle out of Back to the Future.

As with Teleporters or Lasers or the like, an author can simply ignore any issues with time travel. However, in this case, if you are too blatant with the impossibilities it is likely to kill your story with editors and agents, not to mention readers. This is one trope where some amount of hand-waving is required. Let’s look through the methods.

First off, I’m just talking about going back in time. Going forward is easy.

Don’t Pollute the Timeline

This is a favorite of Star Trek but shows up in many other places. It’s basically a way to say you are dealing with time travel paradoxes without actually dealing with them, which makes it fine for certain stories but, for me, anyway, not very satisfying.

Why doesn’t it solve the problem? Because there is truly no way to avoid polluting the timeline. Even if you avoided making contact with any sentient beings, what about that fly that changed course, causing the frog to be elsewhere when the snake wanted to eat, causing the snake to search farther afield for food, biting the naturalist causing her to spend a week in the hospital and miss meeting the man with whom she would have mothered the next Einstein? Or leave out organisms, what about changes in gravitational or electromagnetic fields? You might not think that speck of dust floating in space is all that important but maybe it’s trace as a meteor inspires a poet who writes a poem that changes the life of a person who… You get the point. History is a very chaotic system and tiny perturbations can have dramatic effect. Oh, and don’t forget the microbes time travelers will leave behind.

Echo Park Time Travel Mart
Echo Park Time Travel Mart (Photo credit: Scott Beale)

Destiny

One way to deal with this is to take the approach that the time travel event was always part of how things were meant to be. There was never an earlier timeline where the time traveler did not appear. This sounds weird but Hawkings has noted that, so far, anyway, we don’t have a good physics reason for why time runs forward. And maybe the universe is cyclical: it runs forward to a certain point then runs backward undoing everything in exactly the same way. If we were living on the backward progressing arc, supposedly we wouldn’t even realize it (we would still think as if we were going forward). Or something like that.

This method has neither aesthetic nor intellectual appeal to me. I have to confess it doesn’t even make a lot of sense to me but I’m willing to concede that smarter people than me think it does so there you go. While your story need not posit the backward replay of the universe to make use of this method, it has similar problems: that of freewill. If things can run backwards as well as forwards, then there is nothing unpredictable in the universe. Using destiny to make your time travel work isn’t any different: something must occur, therefore the characters have no choice in what they do.

There are some physicists who think freewill may be an illusion. But do you really want your story to be about characters who can’t actually make any choices? Seems to remove the entire point of a story. If you use this one, you may want to be very sparing with it and be careful of nudging the reader into the conclusion that your characters’ desires are irrelevant to what occurs because if that’s the case, why care about what happens to them?

Observability Horizon

Time travel involves a violation of known laws of physics. This is not a problem because your time travel story is speculative fiction. But that doesn’t mean we can’t take advantage of other laws of physics: if the time travel is to a place beyond the temporal event horizon from earth, there is no possibility of a paradox, at least for a single time travel event.

As any astronomy buff knows, looking into space is looking back into time. If you look at the sun, you see the sun as it was about 500 seconds ago. Look at a star and you are looking back at least a few years, maybe thousands. Galaxies are millions of years away. So, for something that is X light seconds away, if you travel back in time less than X seconds, anything you do can’t change anything that has happened on Earth. It’s harmless.

For instance, lets say you had a 10-year-old child. Let’s also say you travel back in time 11 years. If you do that on earth, who is to say something you did might not change whether your child was even born, let alone the course of his life? But instead, let’s say you travel 10 years back in time to Gliese 832, which is 16 light years away. Now, even if the first thing you did was construct a planet-destroying death beam and fired it at earth, it would not arrive until after your ‘present.’ There is no way for your time travel to affect your child or anything else on earth, at least in the present. When that death beam pulse finally gets here, it’s another matter.

Of course, you might be wondering, what good is time travel if it can’t actually affect the past? Well, obviously, this method doesn’t allow you to change events in your local space. But it could still make an interesting story. Imagine if humans are losing a war to an alien race in 2113 but they have the ability to do this sort of time travel. They send humans back in time 10,000 years to several habitable planets 10,000 light years away with the hope that some of them proceed to the point where they can arrive at the home-world in 2113 with the technology necessary to save the world. Kind of a deus ex machina ending but there’s a story there. Or maybe there is no intent for the time traveling humans to save the present, instead, this is an ark-in-time: humanity dies on Earth but lives on, propagating through time and space.

This falls apart if your time travelers turn around and go back in time to the originating world. However, just like it takes infinite energy to go the speed of light, maybe it takes infinite energy to violate the laws of temporal observability: you can try but it won’t work. It’s hard for me to imagine a mechanism that would actually cause that to be but (a) I’m not a cosmologist and (b) this might be obscure enough that this method might satisfy most readers.

Forked Universes

Another way to deal with time travel is to say that each time travel event “clones” a universe: when you travel back in time, you create a duplicate of the universe at the time you arrive. Anything you do occurs in a separate universe. You can still kill your grandfather but only the grandfather in this duplicate universe, not the one who sired your father who then made you. No paradox.

Of course, universes do tend to contain a fair amount of energy, as in mind-bogglingly vast amounts. But according to current theory, the universe sprang from perturbations in a vacuum so I am not sure this is a really a problem. The energy would come from outside the universe, maybe it doesn’t really matter in the grand scheme of things. Or maybe it’s the old “how many angels can dance on the head of a pin” conundrum. The answer in the middle ages was an infinite number because god could put an angel down on half of the pin, make a half-sized angel, put it down in a quarter of the remaining space, make a quarter size angel, put it down in an eighth of the remaining space, and so on without end. Maybe when you duplicate a universe through time travel you actually make two halves, like a fertilized egg dividing: same mass but now two half-sized cells. To someone in the smaller universe, things might still look the same.

The main issues with this approach for your readers is how to make the universe cloning seem plausible. Some may also wonder just what can cause a cloning event. For instance, does it have to be a sentient being, because if physical processes can cause it there would be a near infinite and ever-increasing number of universes. Even if it has to be a sentient being, you might soon have a vast number of clones out there. Of course, any person in any given clone would only be aware of his or her universe. And maybe the plethora of many universes provides a setting in itself: your characters might hop between possibilities. While they could not return to their own universe in the past, nothing says they couldn’t go from universe A to B and back to A, as long as they arrived in A later than their departure.

As a side note, you could use this for the issue of freewill instead of time travel: maybe every decision results in a universe fork. While it is true that all possible decisions exist in the set of all universes, any given individual is experiencing the results of his decisions. Not sure it really solves the freewill problem but it’s an interesting thought.

Superposition

Quantum mechanics tells us that an electron in a hydrogen atom isn’t orbiting the proton like a planet around a sun. It’s actually in a probability cloud, sort of smeared out in time and space. I think QM would say even Jupiter is in a probably cloud in its orbit around the sun, just that given the mass of the sun and Jupiter, and the distances involved, the probability envelope is really tiny: i.e., for all practical purposes it inhabits a point in a space.

What if time travel works this way? Any given time travel event adds to a cloud of timelines. What happens in the now is the sum of timelines in the past. You can go back and kill your grandfather but that will either not really happen in the present because that event is improbable or you will change the now so that you aren’t present.

Maybe to change the past, you have to go back multiple times and nudges events so that the probability sum results in your desired outcome, or at least a different outcome: this sort of time travel seems rife with unintended consequences. This is actually at the core of my next short story (see, I take my own advice to heart. While I find most time travel stories paradoxical, how would I make this impossibility possible? I’m going with superposition.)

Where in the Past Art Thou?

That’s it for ways I can think of to make time travel work but before I wrap, let’s touch on the where of time travel. Let’s say you do find a way to travel back in time. Where do you go? Not only is everything moving in space, it is moving relative to other things. There isn’t a universal coordinate system. If you want to travel back to Earth one hundred years ago, how do you specify where the earth was then, both in its relationship to the sun (and remember our orbit is not perfect, it does vary due to interactions with the other planets, even with passing asteroids) and the sun’s position in the galaxy and the galaxy’s position in the local cluster, etc., etc. Not only would it be very difficult to compute where the earth was with respect to where it is now, how does your time machine spit you out in the intended spot, and at a velocity that allows you to interact with the Earth (rather than, say, impact it at relativistic speeds?)

Let’s say you can do all that: you can put your time traveler in the exact spot and with the precise velocity vector to avoid smacking into something. Do you know where the surface of the Earth was 100 years ago? Things move, not just down but up. Continents drift: 100 years ago America was about 8 feet closer to Europe. Trees grow. It would suck to appear in the middle of an oak tree, wouldn’t it? For all those reasons, time travel might be best executed in a spaceship with enough delta-v to match the destination.

It’s all handwaving

While the Observability Horizon and the Universe Forking methods avoid time travel paradoxes, they have their own problems. In the end, all of these methods simply constitute more obscure ways to explain time travel. Even so, they may satisfy many readers’ suspension of disbelief better than “avoid polluting the timeline”. And for those it doesn’t satisfy, you might get points for trying or at least amuse them as they think through the puzzle you posed.