Under river, outside time: The Woolwich Foot Tunnel Anomaly

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Under river, outside time: The Woolwich Foot Tunnel Anomaly (Portals of London)
When the Woolwich foot tunnel closed for repairs in 2011, it should have been a routine job. The pathway had been providing pedestrians with a quick route beneath the Thames since 1912. A century o…

When the Woolwich foot tunnel closed for repairs in 2011, it should have been a routine job. The pathway had been providing pedestrians with a quick route beneath the Thames since 1912. A century on, a few minor improvements were necessary. Contractors were hired to plug holes, improve access and bring communications capabilities into the 21st Century: swapping leaky tiles for a leaky feeder.

But Woolwich residents will recall that the refurb of this much loved and much used walkway did not go according to plan. When it finally re-opened it was 8 months behind schedule, having been closed for more than a year and a half. What the average Woolwich dweller doesn’t know, however, are the unusual circumstances behind this delay.

A Three-Sentence Review Of Looper

Looper is a time travel movie of the “self-healing timeline” mechanic (a-la Back To The Future, although Looper “fixes” itself faster and changes to the time stream can be observed and remembered by everybody affected by them). As a result of this, and a few other issues, it suffers from a handful of plotholes and internal inconsistencies: however, it’s still an enormously fun film that I’d recommend that you see.

Looper.
Looper. The second-best film of its category. For a given definition of “category”.

Looper is the second-best of all three movies that feature Bruce Willis travelling back in time and encountering a younger version of himself – and now it’s going to bug you until you work out what the other two are.

Suppose you have a time machine that can only jump to leap days. What’s the chance that a random jump will put you on a Monday? [Maths]

This link was originally posted to /r/puzzles. See more things from Dan's Reddit account.

by an author

Here’s a puzzle for you –

Like the TARDIS, your time machine has a fault.
Like the TARDIS, your time machine has a fault. The fault isn’t a failure of its chameleon circuit, but a quirk in its ability to jump to particular dates. Picture courtesy aussiegall (Flickr), licensed Creative Commons.

You own a time machine with an unusual property: it can only travel to 29th February. It can jump to any 29th February, anywhere at all, in any year (even back before we invented the Gregorian Calendar, and far into the future after we’ve stopped using it), but it can only finish its journey on a 29th of February, in a Gregorian leap year (for this reason, it can only jump to years which are leap years).

One day, you decide to take it for a spin. So you get into your time machine and press the “random” button. Moments later, you have arrived: it is now 29th February in a random year!

Without knowing what year it is: what is the probability that it is a Monday? (hint: the answer is not 1/7 – half of your challenge is to work out why!).

Dan Q

The Leap Machine (Puzzle)

Here’s a puzzle for you –

Like the TARDIS, your time machine has a fault.
Like the TARDIS, your time machine has a fault. The fault isn’t a failure of its chameleon circuit, but a quirk in its ability to jump to particular dates. Picture courtesy aussiegall (Flickr), licensed Creative Commons.

You own a time machine with an unusual property: it can only travel to 29th February. It can jump to any 29th February, anywhere at all, in any year (even back before we invented the Gregorian Calendar, and far into the future after we’ve stopped using it), but it can only finish its journey on a 29th of February, in a Gregorian leap year (for this reason, it can only jump to years which are leap years).

One day, you decide to take it for a spin. So you get into your time machine and press the “random” button. Moments later, you have arrived: it is now 29th February in a random year!

Without knowing what year it is: what is the probability that it is a Monday? (hint: the answer is not 1/7 – half of your challenge is to work out why!).

On This Day in 2040

Looking Forward

On this day in 2040 I first managed to get my Internet Time Portal working. It’s been a long time coming, but my efforts have finally paid off. The trick was just to run The Wayback Machine in reverse, which just required the integration of my flux capacitor with the webserver. Thankfully, Apache 5‘s plugin architecture’s made it pretty easy, but I’ve already talked about how time-travel/webserver integration works back in my blog posts at the end of 2039, so I won’t bore you with them all again.

Despite what I said about password security back in 2011, I haven’t actually changed the password for my blog in 28 years, so it was the obvious target for my first reverse-websurfing experiment. That’s why past-me will be surprised to find this article posted to his blog, now that I’ve connected back in time and posted it. And I know he’ll be surprised, because I was.

In fact, it was probably this moment – this surprising moment back in April 2012 – that first made me realise that reverse-chronological web access was possible. That’s why I spent most of the next three decades cracking the secret and finally working out a way to send information back in time through the Internet.

Looking Back

There’s so much potential for this new technology. I’m hoping that soon the technology will evolve to the point where I’ll even be able to use ancient and outdated Internet protocols like “Facebook” (remember that fad?) to actually communicate directly with the people of the early 21st century. Just think of what we can learn from them!

After the second coming of Jesus in 2028 resulted in the deletion the mysterious “Video R” from the entire Internet, as well as from the minds of everybody on Earth, we’ve only been able to speculate what this mysterious media contained. Whatever it was, it was something so offensive to our Lord and Saviour that He saw fit to wipe it from the face of the Earth… but you can’t help but be curious, can’t you? Of course, those of you reading this back in 2012 can still see the video, you lucky lucky guys.

The possibilities are limitless. As soon as I’ve finished making this post, I’ll be trying to make contact with the past version of myself and see if past-Dan is capable of looking up this Wikipedia article for me: for some reason I can’t get access to it now, in 2040…

This blog post is part of the On This Day series, in which Dan periodically looks back on years yet to come.

A Primer Puzzle

There’s a film that I’m a huge fan of, called Primer. Since I first discovered it I’ve insisted on showing it at least twice at Troma Night (the second time just for the benefit of everybody who didn’t “get it” – i.e. everybody – the first time). If you haven’t already seen it, this post might be a little spoilery, so instead of reading it, you should warm up your time machine, go and watch the film, turn off the time machine, get into the time machine, come out again right now, and then read its Wikipedia page until you understand it. Then come back.

Time Travel in Primer. Click to embiggen.

Still with me? Right.

Why Primer is awesome, and why you should care

In Primer, the protagonists accidentally stumble across the secret of time travel and use it to cheat the stock market. The film isn’t actually about time travel or science-fiction: it’s actually about the breakdown in the relationship between the protagonists, but it’s got some pretty awesome science-fiction in it, too, and that’s what I’d like to talk about. The mechanism of time travel in Primer, for example, is quite fascinating: the traveler turns on the machine using a timer switch (turning it on in person risks the possibility of meeting a future version of themselves coming out of the machine). They then wait for a set amount of time, then they turn off the machine, get into it, wait for the same amount of time again, and emerge from the time machine at the moment that it was turned on.

This is a lot weaker than many of the time travel devices featured in popular science fiction literature, films, and television. It’s not possible to travel forwards in time (except in the usual way with which we’re familiar). Travelling backwards in time takes as long as it took the machine to travel forwards through the same period, making long journeys impossible. The machine has to be strategically turned on at the point at which you want to travel back to, reducing spontaneity, and it can’t be used again in the meantime without resetting it. Oh, and the machine is dangerous and causes long-term damage to humans travelling in it, but that’s rather ancillary.

There’s a certain believability to the time travel mechanic in Primer that gives it a real charm. As far as it is explored in the film, it permits a deterministic universe (so long as one is willing to be reasonably unconventional with one’s interpretation of the linearity of time, as shown in the diagram above), provides severe limits to early time travel (which are great for post-film debate), and doesn’t resort to anything so tacky as, for example, Marty McFly gradually “fading out” after he inadvertently prevented his parents from getting together in Back to the Future.

Marty begins to disappear. I love this film, too, but not even slightly for the same reasons.

Experiments in the Primer universe

I’ve recently been thinking about some of the experiments that I would be performing it I had been the inventor of the Primer time machine.

First and foremost, I’d build a second, smaller time machine of the same design. We know this to be possible because the first machine built by the protagonists is smaller than the ones they later construct. I want to be able to put one time machine inside another. Yes, yes, I know that this is what the protagonists do in the movie, but mine has a difference: mine is capable of being operated (power supply only needs to be a few car batteries, as we discover in the film) within the larger time machine. That’s right, I’m building a time machine inside my time machine.

  • Experiment One attempts to explore the relativism of time. Start the larger time machine and warm it up. Stop the larger time machine. Start the smaller time machine. Get into the larger time machine, carrying the smaller time machine, and travel back. Once back, turn off the larger time machine. Experiment with sending things forwards in time using the second time machine (which has traveled backwards in time but while running, from our frame of reference). If objects inserted into it come out in the future, before it is picked up, this implies that there might be a fixed frame of reference to chronology. It also indicates that it is possible to build a machine for the purpose of traveling forwards in time, too, although only – for now – at the usual rate.
  • Experiment Two attempts to accelerate the rate at which a traveler can move forwards or backwards through time. Based on the explanation given in the movie, the contents of the time machine oscillate backwards and forwards through the period of time between their being turned on and being turned off, for a number of repetitions, before settling. If we are able to synchronise the oscillations of two time machines, one inside the other (by turning them on and off simultaneously, using timers attached to each and their own distinct, internal, power supplies), might we be able to set up a scenario that, in X minutes, switches off, and we can get inside the inner machine and travel back to the switch-on time in X/2 minutes? If so, what happens if we send such a two-machine construction back in time as in Experiment One – do we then have a “time accelerator”?
  • Experiment Three takes advantage of the fact that for an object within the field, an extended period of time has passed (during the oscillations), while from the reference point of an external observer, a far shorter period of time has passed. Experiment with the use of an oscillating time period field to accelerate slow processes. Obvious ones to start with are the production of biologically-produced chemicals, as is done in the film (imagine being able to brew a 10-year-old whiskey in a day!), but there are more options. Processing time on complex computer tasks could be dramatically reduced, for example. Build a large enough time machine and put a particle accelerator in it, and you can bring masses up to relativistic speeds in milliseconds.
  • Experiment Four is on the implications on spacetime of sending mass back in time. As we know, flinging mass in a direction of space produces an equal and opposite acceleration in the opposite direction, as demonstrated by… well, everything, but let’s say “a rocket” and be done with it. Does flinging mass backwards through time produce an acceleration forwards through time? This could be tested by sending back a mass and a highly-accurate timepiece, removing the mass in the past, and letting the timepiece travel back to the future. The timepiece is checked when the experiment starts, when the mass is removed, and when the experiment ends. If the time taken for the second half of the experiment, from the perspective of the timepiece, is longer than the time taken for the first half, then this implies that Newtonian motion, or something equivalent, can be approximated to apply over time as well as space. If so, then one could perhaps build an inertia-generating drive for a vehicle by repeatedly taking a mass out of one end of a time machine, transporting it to the other, and sending it back in time to when you first picked it up.

The scientific possibilities for such a (theoretical) device are limitless.

But yeah, I’d probably just cheat the stock market, too. At least to begin with.