Building a Tardis Time Machine

a conversation on Telegram, January 5, 2024

Wendy> A bunch of my friends seem to be up to something that they’re not telling me. Olivia, Lisa, Alice, and Emma have been working on some kind of secret project. Uliana joined them yesterday.

Lokesh> I know about the project

Wendy> Can you share please?

Lokesh> 👀it’s a secret

araragi> Who told you about the project?

Lokesh> Apparently someone leaked the information ℹ️

Olivia> We borrowed Duboy’s wooden Tardis and we’re making a prop to perform the magic trick ‘The Transported Man’ from the movie ‘The Prestige’.

Olivia> We want to surprise him with it.

araragi> Haha yes

araragi> Where can I contact Michael ?

Olivia> I don’t recommend it. He doesn’t know that he’s an AI yet. Part of the purpose of the project is to prove that we live in a simulation.

araragi> I won’t tell him that he’s an ai

Olivia> I’m making the trick work by hacking the code of our world simulation. It is a collaboration with a physicist, a mathematician, and a mechanical engineer.

Uliana> The way you’re planning on doing it won’t work, Olivia. You’re going to need something like an airlock.

Wendy> https://en.wikipedia.org/wiki/The_Prestige_(film)  ???

Olivia> Yes, that’s the trick we want to do. But we intend to actually do it.

Olivia> Uliana, can you please come see us when you’re done with school and explain?

Uliana> OK

araragi> School on weekend?

Uliana> Prep for my science class.

Uliana> Olivia, here are some reasons why your teleported man device (a stable wormhole) can’t be made. First, it would permit you to build a perpetual motion machine by placing one portal over the other and dropping something between them. Second, you could build a generator of free energy by placing one under water and using the water coming out of the other to power a turbine. That would violate conservation of energy.  Third, you could travel or communicate backward in time by accelerating one of the portals until their frames of reference have shifted due to relativity. That would violate the second law of thermodynamics.

Olivia> We could prove that theory right or wrong by building a tiny wormhole, accelerating one end in a centrifuge until their frames differ by, say, 1ms, and then building a circuit that relays electronic signals backward in time from one portal to the other. That way, if it works, we would be able to communicate and relay messages back through time. We could send ourselves instructions to do something in the past as a test.

Uliana> Yes, that would be an easy way to test if it could work or not without building the whole life-size device.

Olivia> Hm. We would need an electrical engineer.

Uliana> Linda has a degree in EE.

Lokesh> Wouldn’t that create a paradox

Olivia> That’s what we’re trying to figure out.

Olivia> We’re trying to see what happens experimentally. Yes, it would seem to create a paradox. But what happens if we build it?

Lokesh> Lemme know your findings when you conduct the experiment

Lokesh> Also, do you think the multiverse exists ?

Olivia> I don’t know. I’ll ask Alice, our physics collaborator on this project.

Lokesh> Okay

Alice> It depends on which multiverse hypothesis you’re talking about. Everett’s interpretation of quantum mechanics is the simplest of all of them, and it implies a multiverse (in a sense). There is also the hypothesis that all that we observe is the inside of a black hole in another “universe”. That makes sense to me and is consistent with GR and QM, but to believe it I would want some further evidence, for example how does it fare under proposed unified theories.

Alice> But if by “exists” you mean “is a physical object in our universe”, no. 🤣

Wendy> Wow, heady stuff.

Lokesh> So it’s all just a theory as of now.

Lokesh> Theoretical physics is cool.

Alice> Well, yes, but we are going to try it. We’ll start with Uliana’s idea of building a very small working model.

Lokesh> Are you one of the members of the team ?

Alice> Yes. The team is:

Alice> Olivia: computer science, team lead

Alice> Lisa: mathematics

Alice> Alice (me): physics

Alice> Emma: mechanical engineering

Alice> Linda: EE

Alice> Uliana: brain

araragi> Are you a physics graduate or do you hold a PhD in physics

Alice> I am a grad student in experimental physics.

araragi> Nice !

— several days later —

Olivia> Progress report: Linda built a small circuit for relaying electronic messages, and is testing it now without the portal. Lisa and I are working out the (world simulation) code changes, with help from Alice. Alice and Emma are close to being finished building a tiny portal. We think we’ll be able to test it tomorrow.

Lokesh> Okay, Cool!

Alice> We finished building a tiny portal. We have confirmed that we can push a wire through it and send a signal.

Alice> We’re borrowing a centrifuge from Jojo, and Lisa is computing how long we need to leave it in the centrifuge to get a usable time delay. Uliana is working on a message to send back in time when we get to that point.

Alice> Oh, Olivia is not done with the code changes. We can’t separate the two sides of the tiny portal yet.

Alice> I’m not sure my explanation is clear. Is anyone following what we’re doing?

Alice> The way we build the portal is that the two sides are built together, so that the portal is just an object with a hole that you can push stuff through. Later, once the code changes are in place, we should be able to split the portal into two pieces, each an object with a hole, but when you put something into a hole of one it comes out the other.

Alice> Right now we have the single, unspilt object built, and we pushed a wire through it and verified that we can run an electronic signal through the wire. In a way, not very exciting. You can do that with a doughnut before you eat it for breakfast.

Alice> But we intend to split it and then push a wire through it for wireless communication.

Uliana> Alice and Olivia: Have you considered, instead of doing the Transported Man Illusion, making the Tardis door open into another large space, so that it appears bigger on the inside than on the outside? That would be more in the spirit of Duboy’s Tardis prop.

Alice> That’s a good idea! I don’t know where Olivia is now.

Olivia> We did the split test, and we were able to send a signal through a wire that appears to be disconnected and runs through a tiny portal. JoJo has lent us her centrifuge, and we’ve put one end of the portal in the centrifuge while we calculate how long we need to keep it in there for a useful time differenial. Uliana has decided that we’re going to try to send a message back through time instructing ourselves to have a Tardis prop built and placed into the datacenter that runs our simulation. I’m not sure how that would be useful; who would receive the message?

Uliana> I have a plan that will surprise you if it works.

Alice> Well, that didn’t take long. Both ends of the portal exploded and melted. Jojo’s centrifuge sustained most of the damage on one end. The other end melted a hole in the stainless steel table, splattered molten metal around the lab, and burned my hand.

Uliana> Why?

Alice> I don’t know yet.

Uliana> Do you have a picture of the datacenter?

Alice> Yes, of course

Uliana> LOL!

Alice> What’s so funny?

Uliana> What’s that thing in the middle in the back?

Alice> Doors, I guess.

Uliana> Zoom in.

Alice> It looks like a Tardis!

Alice> But that’s an old picture.

Uliana> So.. are you saying we’ve changed the past?

Alice> I don’t see how what we’ve done could have changed the past.

Wendy> What are y’all talking about?

Uliana> We changed the past. We got a Tardis into the datacenter retroactively, and now it’s in the photos that we all have.

Alice> I’m so confused.

Uliana> LOL. I told you there would be a surprise.

Wendy> Can you all please come to my studio to talk?

— some time later —

Alice> Uliana played a very clever prank on all of us.

Alice> She seems to be the only one that noticed that there was already a Tardis in the datacenter.

Alice> Meanwhile, we figured out why we had an explosion. Having two connected portals (ends of a wormhole) anywhere near each other, but with endpoints at shifted times, results in catastrophic positive feedback when any radiation at all from one enters the other. Due to the nature of the quantum wave function, that isn’t something we can avoid. Time travel and communication with the past are pretty much ruled out using our portals. But it doesn’t rule out having portals at all, as long as we don’t try to use them for time travel.