Mark Reads ‘The Science of Discworld III’: Chapter 8

In the eighth chapter of Darwin’s Watch, I get to talk about TIME MACHINES! Intrigued? Then it’s time for Mark to read The Science of Discworld III. 

Oh, y’all, this was GREAT. I knew from past Science of DIscworld books and from a very, VERY basic understanding of general relativity that time travel was theoretically possible, but all this? This was so much fun to read as someone who has devoured science fiction since I was a kid. Time travel has been represented in so many different ways since the incarnation of these types of stories. (And I should also note that I love time travel that doesn’t focus on or feature any science. Kindred by Octavia Butler, for example, is one of my favorite time travel books, and it’s just a device. It’s never explained.) This chapter focuses entirely on the actual mechanics of traveling through time, and I AM SO INTO THIS. 

So, let’s start with this: the closed timelike curve, which is what is needed for an object to return to its own past. Accepting that this is required of time travel—which is interesting, because what if someone only wanted to travel ahead in time and never back to their past?—the authors run us through some of the more “feasible” methods of time travel. I use “feasible” lightly here, since the book openly addresses the fact that all of these methods aren’t actually possible yet. The first of those methods: black holes, white holes, and wormholes! All things I’ve seen in some form in SF novels. (It’s also truly amazing that I get to read this book just after the first photo of a black hole was ever published. THAT IS SO COOL, I love science.) But the authors do a great job of setting up my understanding of black holes so that each of the pieces that could lead to possible time travel make sense AND make it show how ridiculously difficult it would be to pull it all off. We are certainly not technologically advanced enough as a species to just build a black hole. Also, I’m a bit of a cynic about humans ever possessing this power. Leave it up to some terrible tech bro to utilize this for localized instant travel and then our whole planet gets sucked into a black hole because while that’s probably physically impossible, IT IS SPIRITUALLY QUITE BELIEVABLE. Anyway, a wormhole allows for “matter-transmission,” but not exactly a time travel device. And that’s where this is proposed:

The idea is to leave the white end of the wormhole fixed, and to zigzag the black one back and forth at just below the speed of light. As the black end zigzags, time dilation comes into play, and time passes more slowly for an observer moving with that end. 

So, it’s a more technical example of time travel, and I don’t know how you’d fine tune something like that. How much further into the future must your starting be? Either way, this theoretical travel doesn’t allow travel “back past the time barrier,” or some time after humans constructed the wormholes. So, not all that helpful, is it? You couldn’t even travel back to stop the construction of the wormholes in case that sets in motion some sort of terrible timeline!

There are magnetic wormholes, too, which require exotic matter, and this is already way over my head and currently impossible. (Currently. Because when this book was written, we hadn’t seen a photo of a black hole!!!) And if we can’t even make a black hole now, how are we gonna make a rotating black hole that’s connected to “infinitely many different regions of spacetime”? Also, how would we program it to land in the universe we wanted? WHAT IF WE WENT TO THE WRONG UNIVERSE. 

Basically: this chapter continued to give me ideas for super messed up science fiction stories, and that’s a perfect segue to the brilliance that science fiction writers came up with shit that is not all that far from our current understanding of reality. Because space can travel faster than light, and there’s an actual theory of how time travel and faster-than-light travel could work by warping spacetime to form a “mobile bubble” around an object and then make it surf a gravitational wave while INSIDE that bubble. 

The SF writers were right. There is no relativistic limit to the speed with which space can move.

I LOVE THIS. And I know this is something that was discussed many times as I made my way through the entirety of Star Trek, but that show got a LOT of shit right through imagination and prediction. So, is the future of travel a superluminary highway? Linked wormholes? Warp drives, which would probably require an energy level that is “10 billion times the mass of the known universe” in order to craft that mobile bubble? WHO KNOWS. And that’s not even addressing the bent space method of travel using bent-light in the shape of a ring!

All this to say: What if the universe does prevent paradoxes from existing? What if time travel will forever remain a theory because of what Hawking proposed? Argh, this is so frustrating and fun to think about, I swear.

https://www.youtube.com/watch?v=FqObsYdP0aY

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