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T E N Ǝ T

Jessica and I went to cinema yesterday.

Normally this wouldn’t be a big deal, but in our current circumstances, it was something of a momentous decision that involved a lot of risk assessment and weighing of the odds. We’ve been out and about a few times, but always to outdoor locations: the beach, a park, or a pub’s beer garden. For the first time, we were evaluating whether or not to enter an indoor environment, which given what we now know about the transmission of COVID-19, is certainly riskier than being outdoors.

But this was a cinema, so in theory, nobody should be talking (or singing or shouting), and everyone would be wearing masks and keeping their distance. Time was also on our side. We were considering a Monday afternoon showing—definitely not primetime. Looking at the website for the (wonderful) Duke of York’s cinema, we could see which seats were already taken. Less than an hour before the start time for the film, there were just a handful of seats occupied. A cinema that can seat a triple-digit number of people was going to be seating a single digit number of viewers.

We got tickets for the front row. Personally, I love sitting in the front row, especially in the Duke of York’s where there’s still plenty of room between the front row and the screen. But I know that it’s generally considered an undesirable spot by most people. Sure enough, the closest people to us were many rows back. Everyone was wearing masks and we kept them on for the duration of the film.

The film was Tenet). We weren’t about to enter an enclosed space for just any ol’ film. It would have to be pretty special—a new Star Wars film, or Denis Villeneuve’s Dune …or a new Christopher Nolan film. We knew it would look good on the big screen. We also knew it was likely to be spoiled for us if we didn’t see it soon enough.

At this point I am sounding the spoiler horn. If you have not seen Tenet yet, abandon ship at this point.

I really enjoyed this film. I understand the criticism that has been levelled at it—too cold, too clinical, too confusing—but I still enjoyed it immensely. I do think you need to be able to enjoy feeling confused if this is going to be a pleasurable experience. The payoff is that there’s an equally enjoyable feeling when things start slotting into place.

The closest film in Christopher Nolan’s back catalogue to Tenet is Inception in terms of twistiness and what it asks of the audience. But in some ways, Tenet is like an inverted version of Inception. In Inception, the ideas and the plot are genuinely complex, but Nolan does a great job in making them understandable—quite a feat! In Tenet, the central conceit and even the overall plot is, in hindsight, relatively straightforward. But Nolan has made it seem more twisty and convuluted than it really is. The ten minute battle at the end, for example, is filled with hard-to-follow twists and turns, but in actuality, it literally doesn’t matter.

The pitch for the mood of this film is that it’s in the spy genre, in the same way that Inception is in the heist genre. Though there’s an argument to be made that Tenet is more of a heist movie than Inception. But in terms of tone, yeah, it’s going for James Bond.

Even at the very end of the credits, when the title of the film rolled into view, it reminded me of the Bond films that would tease “The end of (this film). But James Bond will return in (next film).” Wouldn’t it have been wonderful if the very end of Tenet’s credits finished with “The end of Tenet. But the protagonist will return in …Tenet.”

The pleasure I got from Tenet was not the same kind of pleasure I get from watching a Bond film, which is a simpler, more basic kind of enjoyment. The pleasure I got from Tenet was more like the kind of enjoyment I get from reading smart sci-fi, the kind that posits a “what if?” scenario and isn’t afraid to push your mind in all kinds of uncomfortable directions to contemplate the ramifications.

Like I said, the central conceit—objects or people travelling backwards through time (from our perspective)—isn’t actually all that complex, but the fun comes from all the compounding knock-on effects that build on that one premise.

In the film, and in interviews about the film, everyone is at pains to point out that this isn’t time travel. But that’s not true. In fact, I would argue that Tenet is one of the few examples of genuine time travel. What I mean is that most so-called time-travel stories are actually more like time teleportation. People jump from one place in time to another instaneously. There are only a few examples I can think of where people genuinely travel.

The grandaddy of all time travel stories, The Time Machine by H.G. Wells, is one example. There are vivid descriptions of the world outside the machine playing out in fast-forward. But even here, there’s an implication that from outside the machine, the world cannot perceive the time machine (which would, from that perspective, look slowed down to the point of seeming completely still).

The most internally-consistent time-travel story is Primer. I suspect that the Venn diagram of people who didn’t like Tenet and people who wouldn’t like Primer is a circle. Again, it’s a film where the enjoyment comes from feeling confused, but where your attention will be rewarded and your intelligence won’t be insulted.

In Primer, the protagonists literally travel in time. If you want to go five hours into the past, you have to spend five hours in the box (the time machine).

In Tenet, the time machine is a turnstile. If you want to travel five hours into the past, you need only enter the turnstile for a moment, but then you have to spend the next five hours travelling backwards (which, from your perspective, looks like being in a world where cause and effect are reversed). After five hours, you go in and out of a turnstile again, and voila!—you’ve time travelled five hours into the past.

Crucially, if you decide to travel five hours into the past, then you have always done so. And in the five hours prior to your decision, a version of you (apparently moving backwards) would be visible to the world. There is never a version of events where you aren’t travelling backwards in time. There is no “first loop”.

That brings us to the fundamental split in categories of time travel (or time jump) stories: many worlds vs. single timeline.

In a many-worlds story, the past can be changed. Well, technically, you spawn a different universe in which events unfold differently, but from your perspective, the effect would be as though you had altered the past.

The best example of the many-worlds category in recent years is William Gibson’s The Peripheral. It genuinely reinvents the genre of time travel. First of all, no thing travels through time. In The Peripheral only information can time travel. But given telepresence technology, that’s enough. The Peripheral is time travel for the remote worker (once again, William Gibson proves to be eerily prescient). But the moment that any information travels backwards in time, the timeline splits into a new “stub”. So the many-worlds nature of its reality is front and centre. But that doesn’t stop the characters engaging in classic time travel behaviour—using knowledge of the future to exert control over the past.

Time travel stories are always played with a stacked deck of information. The future has power over the past because of the asymmetric nature of information distribution—there’s more information in the future than in the past. Whether it’s through sports results, the stock market or technological expertise, the future can exploit the past.

Information is at the heart of the power games in Tenet too, but there’s a twist. The repeated mantra here is “ignorance is ammunition.” That flies in the face of most time travel stories where knowledge—information from the future—is vital to winning the game.

It turns out that information from the future is vital to winning the game in Tenet too, but the reason why ignorance is ammunition comes down to the fact that Tenet is not a many-worlds story. It is very much a single timeline.

Having a single timeline makes for time travel stories that are like Greek tragedies. You can try travelling into the past to change the present but in doing so you will instead cause the very thing you set out to prevent.

The meat’n’bones of a single timeline time travel story—and this is at the heart of Tenet—is the question of free will.

The most succint (and disturbing) single-timeline time-travel story that I’ve read is by Ted Chiang in his recent book Exhalation. It’s called What’s Expected Of Us. It was originally published as a single page in Nature magazine. In that single page is a distillation of the metaphysical crisis that even a limited amount of time travel would unleash in a single-timeline world…

There’s a box, the Predictor. It’s very basic, like Claude Shannon’s Ultimate Machine. It has a button and a light. The button activates the light. But this machine, like an inverted object in Tenet, is moving through time differently to us. In this case, it’s very specific and localised. The machine is just a few seconds in the future relative to us. Cause and effect seem to be reversed. With a normal machine, you press the button and then the light flashes. But with the predictor, the light flashes and then you press the button. You can try to fool it but you won’t succeed. If the light flashes, you will press the button no matter how much you tell yourself that you won’t (likewise if you try to press the button before the light flashes, you won’t succeed). That’s it. In one succinct experiment with time, it is demonstrated that free will doesn’t exist.

Tenet has a similarly simple object to explain inversion. It’s a bullet. In an exposition scene we’re shown how it travels backwards in time. The protagonist holds his hand above the bullet, expecting it to jump into his hand as has just been demonstrated to him. He is told “you have to drop it.” He makes the decision to “drop” the bullet …and the bullet flies up into his hand.

This is a brilliant bit of sleight of hand (if you’ll excuse the choice of words) on Nolan’s part. It seems to imply that free will really matters. Only by deciding to “drop” the bullet does the bullet then fly upward. But here’s the thing: the protagonist had no choice but to decide to drop the bullet. We know that he had no choice because the bullet flew up into his hand. The bullet was always going to fly up into his hand. There is no timeline where the bullet doesn’t fly up into his hand, which means there is no timeline where the protagonist doesn’t decide to “drop” the bullet. The decision is real, but it is inevitable.

The lesson in this scene is the exact opposite of what it appears. It appears to show that agency and decision-making matter. The opposite is true. Free will cannot, in any meaningful sense, exist in this world.

This means that there was never really any threat. People from the future cannot change the past (or wipe it out) because it would’ve happened already. At one point, the protagonist voices this conjecture. “Doesn’t the fact that we’re here now mean that they don’t succeed?” Neil deflects the question, not because of uncertainty (we realise later) but because of certainty. It’s absolutely true that the people in the future can’t succeed because they haven’t succeeded. But the protagonist—at this point in the story—isn’t ready to truly internalise this. He needs to still believe that he is acting with free will. As that Ted Chiang story puts it:

It’s essential that you behave as if your decisions matter, even though you know that they don’t.

That’s true for the audience watching the film. If we were to understand too early that everything will work out fine, then there would be no tension in the film.

As ever with Nolan’s films, they are themselves metaphors for films. The first time you watch Tenet, ignorance is your ammuntion. You believe there is a threat. By the end of the film you have more information. Now if you re-watch the film, you will experience it differently, armed with your prior knowledge. But the film itself hasn’t changed. It’s the same linear flow of sequential scenes being projected. Everything plays out exactly the same. It’s you who have been changed. The first time you watch the film, you are like the protagonist at the start of the movie. The second time you watch it, you are like the protagonist at the end of the movie. You see the bigger picture. You understand the inevitability.

The character of Neil has had more time to come to terms with a universe without free will. What the protagonist begins to understand at the end of the film is what Neil has known for a while. He has seen this film. He knows how it ends. It ends with his death. He knows that it must end that way. At the end of the film we see him go to meet his death. Does he make the decision to do this? Yes …but he was always going to make the decision to do this. Just as the protagonist was always going to decide to “drop” the bullet, Neil was always going to decide to go to his death. It looks like a choice. But Neil understands at this point that the choice is pre-ordained. He will go to his death because he has gone to his death.

At the end, the protagonist—and the audience—understands. Everything played out exactly as it had to. The people in the future were hoping that reality allowed for many worlds, where the past could be changed. Luckily for us, reality turns out to be a single timeline. But the price we pay is that we come to understand, truly understand, that we have no free will. This is the kind of knowledge we wish we didn’t have. Ignorance was our ammunition and by the end of the film, it is spent.

Nolan has one other piece of misdirection up his sleeve. He implies that the central question at the heart of this time-travel story is the grandfather paradox. Our descendents in the future are literally trying to kill their grandparents (us). But if they succeed, then they can never come into existence.

But that’s not the paradox that plays out in Tenet. The central paradox is the bootstrap paradox, named for the Heinlein short story, By His Bootstraps. Information in this film is transmitted forwards and backwards through time, without ever being created. Take the phrase “Tenet”. In subjective time, the protagonist first hears of this phrase—and this organisation—when he is at the start of his journey. But the people who tell him this received the information via a subjectively older version of the protagonist who has travelled to the past. The protagonist starts the Tenet organistion (and phrase) in the future because the organisation (and phrase) existed in the past. So where did the phrase come from?

This paradox—the bootstrap paradox—remains after the grandfather paradox has been dealt with. The grandfather paradox was a distraction. The bootstrap paradox can’t be resolved, no matter how many times you watch the same film.

So Tenet has three instances of misdirection in its narrative:

  • Inversion isn’t time travel (it absolutely is).
  • Decisions matter (they don’t; there is no free will).
  • The grandfather paradox is the central question (it’s not; the bootstrap paradox is the central question).

I’m looking forward to seeing Tenet again. Though it can never be the same as that first time. Ignorance can never again be my ammunition.

I’m very glad that Jessica and I decided to go to the cinema to see Tenet. But who am I kidding? Did we ever really have a choice?

Starting out

I had a really enjoyable time at Codebar Brighton last week, not least because Morty came along.

I particularly enjoy teaching people who have zero previous experience of making a web page. There’s something about explaining HTML and CSS from first principles that appeals to me. I especially love it when people ask lots of questions. “What does this element do?”, “Why do some elements have closing tags and others don’t?”, “Why is it textarea and not input type="textarea"?” The answer usually involves me going down a rabbit-hole of web archeology, so I’m in my happy place.

But there’s only so much time at Codebar each week, so it’s nice to be able to point people to other resources that they can peruse at their leisure. It turns out that’s it’s actually kind of tricky to find resources at that level. There are lots of great articles and tutorials out there for professional web developers—Smashing Magazine, A List Apart, CSS Tricks, etc.—but no so much for complete beginners.

Here are some of the resources I’ve found:

  • MarkSheet by Jeremy Thomas is a free HTML and CSS tutorial. It starts with an explanation of the internet, then the World Wide Web, and then web browsers, before diving into HTML syntax. Jeremy is the same guy who recently made CSS Reference.
  • Learn to Code HTML & CSS by Shay Howe is another free online book. You can buy a paper copy too. It’s filled with good, clear explanations.
  • Zero to Hero Coding by Vera Deák is an ongoing series. She’s starting out on her career as a front-end developer, so her perspective is particularly valuable.

If I find any more handy resources, I’ll link to them and tag them with “learning”.

This is for everyone with a certificate

Mozilla—like Google before them—have announced their plans for deprecating HTTP in favour of HTTPS. I’m all in favour of moving to HTTPS. I’ve done it myself here on adactio.com, on thesession.org, and on huffduffer.com. I have some concerns about the potential linkrot involved in the move to TLS everywhere—as outlined by Tim Berners-Lee—but still, anything that makes the work of GCHQ and the NSA more difficult is alright by me.

But I have a big, big problem with Mozilla’s plan to “encourage” the move to HTTPS:

Gradually phasing out access to browser features.

Requiring HTTPS for certain browser features makes total sense, given the security implications. Service Workers, for example, are quite correctly only available over HTTPS. Any API that has access to a device sensor—or that could be used for fingerprinting in any way—should only be available over HTTPS. In retrospect, Geolocation should have been HTTPS-only from the beginning.

But to deny access to APIs where there are no security concerns, where it is merely a stick to beat people with …that’s just wrong.

This is for everyone. Not just those smart enough to figure out how to add HTTPS to their site. And yes, I know, the theory is that is that it’s going to get easier and easier, but so far the steps towards making HTTPS easier are just vapourware. That makes Mozilla’s plan look like something drafted by underwear gnomes.

The issue here is timing. Let’s make HTTPS easy first. Then we can start to talk about ways of encouraging adoption. Hopefully we can figure out a way that doesn’t require Mozilla or Google as gatekeepers.

Sven Slootweg outlines the problems with Mozilla’s forced SSL. I highly recommend reading Yoav’s post on deprecating HTTP too. Ben Klemens has written about HTTPS: the end of an era …that era being the one in which anyone could make a website without having to ask permission from an app store, a certificate authority, or a browser manufacturer.

On the other hand, Eric Mill wrote We’re Deprecating HTTP And It’s Going To Be Okay. It makes for an extremely infuriating read because it outlines all the ways in which HTTPS is a good thing (all of which I agree with) without once addressing the issue at hand—a browser that deliberately cripples its feature set for political reasons.

Radio Free Earth

Back at the first San Francisco Science Hack Day I wanted to do some kind of mashup involving the speed of light and the distance of stars:

I wanted to build a visualisation based on Matt’s brilliant light cone idea, but I found it far too daunting to try to find data in a usable format and come up with a way of drawing a customisable geocentric starmap of our corner of the galaxy. So I put that idea on the back burner…

At this year’s San Francisco Science Hack Day, I came back to that idea. I wanted some kind of mashup that demonstrated the connection between the time that light has travelled from distant stars, and the events that would have been happening on this planet at that moment. So, for example, a star would be labelled with “the battle of Hastings” or “the sack of Rome” or “Columbus’s voyage to America”. To do that, I’d need two datasets; the distance of stars, and the dates of historical events (leaving aside any Gregorian/Julian fuzziness).

For wont of a better hack, Chloe agreed to help me out. We set to work finding a good dataset of stellar objects. It turned out that a lot of the best datasets from NASA were either about our local solar neighbourhood, or else really distant galaxies and stars that are emitting prehistoric light.

The best dataset we could find was the Near Star Catalogue from Uranometria but the most distant star in that collection was only 70 or 80 light years away. That meant that we could only mash it up with historical events from the twentieth century. We figured we could maybe choose important scientific dates from the past 70 or 80 years, but to be honest, we really weren’t feeling it.

We had reached this impasse when it was time for the Science Hack Day planetarium show. It was terrific: we were treated to a panoramic tour of space, beginning with low Earth orbit and expanding all the way out to the cosmic microwave background radiation. At one point, the presenter outlined the reach of Earth’s radiosphere. That’s the distance that ionosphere-penetrating radio and television signals from Earth, travelling at the speed of light, have reached. “It extends about 70 light years out”, said the presenter.

This was perfect! That was exactly the dataset of stars that we had. It was a time for a pivot. Instead of the lofty goal of mapping historical events to the night sky, what if we tried to do something more trivial and fun? We could demonstrate how far classic television shows have travelled. Has Star Trek reached Altair? Is Sirius receiving I Love Lucy yet?

No, not TV shows …music! Now we were onto something. We would show how far the songs of planet Earth had travelled through space and which stars were currently receiving which hits.

Chloe remembered there being an API from Billboard, who have collected data on chart-topping songs since the 1940s. But that API appears to be gone, and the Echonest API doesn’t have chart dates. So instead, Chloe set to work screen-scraping Wikipedia for number one hits of the 40s, 50s, 60s, 70s …you get the picture. It was a lot of finding and replacing, but in the end we had a JSON file with every number one for the past 70 years.

Meanwhile, I was putting together the logic. Our list of stars had the distances in parsecs. So I needed to convert the date of a number one hit song into the number of parsecs that song had travelled, and then find the last star that it has passed.

We were tempted—for developer convenience—to just write all the logic in JavaScript, especially as our data was in JSON. But even though it was just a hack, I couldn’t bring myself to write something that relied on JavaScript to render the content. So I wrote some really crappy PHP instead.

By the end of the first day, the functionality was in place: you could enter a date, and find out what was number one on that date, and which star is just now receiving that song.

After the sleepover (more like a wakeover) in the aquarium, we started to style the interface. I say “we” …Chloe wrote the CSS while I made unhelpful remarks.

For the icing on the cake, Chloe used her previous experience with the Rdio API to add playback of short snippets of each song (when it’s available).

Here’s the (more or less) finished hack:

Radio Free Earth.

Basically, it’s a simple mashup of music and space …which is why I spent the whole time thinking “What would Matt do?”

Just keep hitting that button to hear a hit from planet Earth and see which lucky star is currently receiving the signal.*

Science!

*I know, I know: the inverse-square law means it’s practically impossible that the signal would be in any state to be received, but hey, it’s a hack.