The Czar Dictates

Taking my talents (?) to Patreon

2025-10-20T07:24:00.001-04:00

I'm moving my blogging over to Patreon. You can find me at Jacob Zelten | Patreon

Not that I expect to make money, just that its an easier platform to work with. And who knows how long Blogger will still be around.

For those few that followed me here, be aware that I will be republishing a few of my favorite pieces over there, to get it up and running.

The Singularity is near, and it's really stupid

2025-09-19T18:13:00.001-04:00

For reasons I won't get into, I searched for information about the meme Don't Create the Torment Nexus. (If you're not familiar, check it out first) on a well-known search engine.

And to my surprise, the search engine came back with a summary of the plot of Don't Create the Torment Nexus.

A book that does not exist.

Here it is, for your enjoyment, and in case you ever get asked to write a book report about it.

Overview of "Don't Create the Torment Nexus"

"Don't Create the Torment Nexus" is a science fiction novel by Walter Jon Williams. It explores themes of technology, ethics, and societal collapse in a dystopian future.

Key Themes

Technological Caution: The title itself serves as a warning against the potential dangers of unchecked technological advancement.
Dystopian Society: The story is set in a fragmented United States, where state governments impose tariffs, creating a chaotic environment for entrepreneurs and mercenaries.
Character Dynamics: The narrative follows two main characters, Cowboy and Sarah, whose paths intersect in a world driven by profit and violence.

Publication Details

Author: Walter Jon Williams
Genre: Science Fiction, Cyberpunk
First Published: 1983/1984
Availability: The book remains in print and can be found on various platforms like Smashwords, Barnes & Noble, and Kobo.

Reception

The novel has been noted for its prescient themes, reflecting contemporary issues such as corporate greed and societal fragmentation. It is recognized as one of Williams' best-selling works, appealing to fans of the cyberpunk genre.

How DCC Really Works

2025-09-17T08:37:00.001-04:00

The most important thing to know about how DCC works is this: you don't need to know how DCC works. Just as you can drive a car without knowing how an engine works, and use the internet without knowing TCP/IP, the only things you really need to know are how to set up and use DCC - and that's covered in great detail elsewhere on the DCCwiki.

Still here? OK, you really want to know how DCC works. There is a lot of misinformation and misunderstanding about DCC, so we'll take things step by step. If you know much about electronics, some of this will seem very basic. Please bear with it.

DCC is very different from DC. You may have heard the adage "with DC, you control the track; with DCC, you control the locomotives". And that's a very good way to look at it.

With DC, you control the voltage across the two rails of the track - for HO, typically that's between 0V and 14V. The voltage powers the motor, which determines how fast the train runs. And that's it. If you put two trains on the same track they both run (although probably at different speeds depending on the gearing between the motor and the wheels). If you turn the voltage to zero, they both stop.

With DCC, the voltage across the two rails is always 14V (again, assuming HO). Every locomotive on the track is always receiving 14V. The versatility of DCC comes from the fact that every locomotive on the track has a decoder chip - essentially, a tiny computer - inside it that controls the locomotive's speed and other functions such as lights and horn. How fast a locomotive runs is determined by sending a signal from your controller or cab along the rails to that locomotive - and only that locomotive - that is interpreted by the decoder, which in turn determines how much voltage out of the 14V available to it to pass to the motor. In this way, each locomotive can receive a different amount of the available 14V, and therefore each can run at its own speed. Similarly, a different signal instructs the decoder to switch on or off the lights, or sound the horn, and so on.

So what does that signal look like, and how does it go only to the right locomotive?

Since the signal is sent over the rails, it will be seen physically by every locomotive on the rails. (This is much the same as a computer network, such as WiFi.) The signal that is sent out by the controller consists of a sequence of information called a packet. A packet comprises an address and a command. Each decoder chip has it's own address, which is simply a unique identifying number. That number is stored in the Configuration Variables, or CVs, of the decoder, as described elsewhere in the wiki. The address is typically set to 3 at the factory, and normally you'll change it right away to something unique on your layout, such as the road number of the locomotive. Each decoder only responds to the commands that are addressed to it. (If you are familiar with computer networking, you will recognize that this is again very similar: each computer has a unique IP address, and only responds to packets intended for that address.) The command might be an instruction such as "set speed" (and direction, forward or reverse) plus a byte of data to specify the speed, for example "64" if you are using 128 speed steps and want 50% speed. It could also be a command to sound a horn or whistle, or to turn on or off lights, or anything else that particular locomotive is capable of. These commands correspond to the functions available on your decoder chip.

Simply put, this is how DCC can control several locomotives independently on the same track: each decoder only obeys commands that start with its particular address, and ignores commands addressed to other locomotives.

If you only want to know how DCC can control several locomotives on one track, you can stop reading here. But if you want to know more details about what those signals look like electrically, continue reading.

Now comes the part that causes the most confusion about how DCC actually works. Like other computer networks, the DCC signal consists of a binary code, a series of 0s and 1s. On learning this, many people assume that means that the voltage turns off to indicate a 0 and on to indicate a 1.

This is completely incorrect and it's where many online attempts to explain DCC go wrong. The key concept to grasp is that there are lots of ways to indicate 0s and 1s electronically, and On or Off is only one of them.

Probably the simplest scheme to send signals electronically is to have a high voltage for 1 and a low voltage for 0. For example, if you are familiar with Arduino microcontrollers, a voltage of 5V means HIGH, or 1, and a voltage of 0V means LOW, or 0. [Strictly speaking, because electronic circuits are never perfect, the Arduino treats anything above 3.0V as a HIGH and anything below 1.5V as LOW.]

But this is far from the only way to encode 0s and 1s. For example, the memory inside your computer, smartphone, smartwatch, Oura ring, or anything else you own that has a processor inside it, probably uses a type of memory called CMOS. Inside that memory, each bit is represented by a pair of transistors. To store a 1, one of the transistors is On and the other Off. To store a 0, the states of the two transistors are reversed.

This is the key fact about digital signals: a 0 bit in a signal does not necessarily correspond to 0V in a circuit. And with DCC, it definitely doesn't.

As we said earlier, using On and Off for 1 and 0 is a very simple scheme. However, this won't work for controlling our locomotives, for two important reasons. First, recall that the decoder powers the motor by taking 14V from the track, and then providing some fraction of that voltage to the motor according to the speed setting that was sent to it. If the voltage between the rails were set to zero to indicate a 0 bit, then no voltage would be available to the decoder, and the motor would lose power for an instant. If a signal is sent that requires a sequence of zeroes, the motor would lose power throughout that signal. Overall, the power available to the locomotives would drop depending on the number of 0s being transmitted. And obviously that's not good. We want the power to the locomotives to be constant, and therefore we need the voltage to be constant, not On/Off.

Second, an On/Off signal is fine for reading something simple such as a single bit, like the setting of a switch, but it's much harder to use to send a rapid sequence of bits. Suppose the controller sends a signal that is a sequence of 1s, for example to set the speed of a locomotive to 256. It's very hard for a decoder to figure out where one 1 stops and the next one starts, because it would just see a constant 14V (HIGH) signal. In order to know how many 1s were received, it would require very precise timers that are synchronized between the controller and all the locomotives, and that's not practical in this case.

So the designers of DCC used a clever trick for signalling 1s and 0s that solves both problems: it provides constant voltage to the track; and it makes it easy for decoders to detect where one bit ends and the next begins. Instead of signalling 1s and 0s by the level - high or low - of the voltage, DCC signals 1s and 0s by changing the level of the voltage. A change in voltage is much easier for a decoder to detect, and doesn't require synchronized clocks. The clever part is the voltage is always 14V - only the direction of the voltage changes. And the timing of the changes encodes the 1s and 0s.

Let's look at this in specific detail. Imagine you are the engineer in a model locomotive, looking at the track ahead of you. Suppose that the rail on your left is 14V, and the one on your right is 0V. Then, your decoder sees the voltage switch, so that the left rail becomes 0V and the right one 14V. The decoder recognizes this change in voltage direction as the beginning of a bit. A moment later, the voltage switches back again, and the decoder recognizes the end of that bit. That back-and-forth switch is called a pulse. Throughout this process, the voltage is always 14V; as noted above, only the direction changes. (If you like a physical picture, imagine two children playing on a teeter-totter or seesaw: when one end goes up, the other goes down, but the difference in height between the two children is the same either way.)

This is the key concept in understanding how DCC works: DCC indicates 1s and 0s by the length of each pulse.

Specifically, if the pulse is 116 microseconds long, it represents a 0. If it is 58 microseconds long, it represents a 1. And to reiterate, the voltage between the rails is always 14V, never 0V; only the direction changes.

The picture below is widely reproduced, and shows this idea graphically. Unfortunately it can be a bit confusing to interpret. The way to understand it is that when the blue-ish line is above the center black line, the left rail is 14V higher than the right rail, so current flows from left rail to right right. When the blue-ish line is below the center black line, the left rail is 14V lower than the right rail, so current flows from right to left.

[Some people like to think of this as the right rail always being 0V, while the left rail switches between 14V and -14V. In reality, this is exactly the same thing because "voltage" is not an absolute measure, like height above sea level; rather, voltage measures the relative difference between two points in a circuit, like the top and bottom of a waterfall. And the difference from -14 to 0 is the same as the difference from 0 to 14. In both descriptions, the right rail is 14V higher than the left rail, and that's what matters. So you can think of it whichever way works best for you, as long as you remember that there is always a difference of 14V in one direction or the other. If you prefer this viewpoint, the picture is much easier to read: the black line represents the right rail, always at 0V, and the blue-ish line represents the left rail, switching back and forth between 14V and -14V relative to the right rail.]

If you look closely at the picture, you will also notice that earlier I simplified the explanation of a pulse. In reality, a 0 is indicated by setting the voltage in one direction across the rails for a long time (116ms), then in the other direction for the same amount of time, before returning to the original direction, ready to send the next bit. Similarly, each 1 is indicated by a pair of short peaks (58us), one in each direction. (The technical reasons for this redundancy are too detailed to get into here.)

Now you might be wondering, if the voltage is continually switching back and forth, why don't the locomotives just stutter back and forth, instead of running smoothly in one direction? The solution is a component in the decoder called a rectifier, which takes current in either direction as input, and outputs it in a single constant direction. (The same component is what enables a USB adapter to take 110V AC or 220V AC and output 5V DC.)

There are a lot more technical details to DCC signalling if you are interested, for example the precise formats of address and data bytes; and what happens when no commands are being sent. That information can readily be found online, but it isn't necessary to understanding how DCC works.

And there we have it. In summary: DCC delivers a continuous voltage across the rails so that full power is always available to the locomotives. It sends signals by flipping the direction of the voltage. The 1s and 0s are encoded by the timing of the back-and-forth switching, or in other words, the length of the pulses. And those 1s and 0s are interpreted by the decoder chip into addresses and commands.

Death to Greige

2025-09-04T09:21:00.000-04:00

I just reread Kate Wagner's piece for The Nation, "Liberating Our Homes From the Real Estate–Industrial Complex" that dissects the rise of greige as a decorating theme, and feel like there's another pernicious incentive at work that wasn't mentioned (or if it was mentioned, I missed it and you can ignore the rest of this!). You should read that first for context.

Back? OK.

At the intersection of platformization and houses-as-assets capitalism is the idea that greigifying everything, as well as eliminating taste, also reduces every house to objects that Zillow and Redfin can most easily monetize, by which I mean attributes that can be counted: square footage, number of bedrooms, number of bathrooms, acreage, age, these are all things that the platforms can readily filter and sort on. Those messy, human characteristics like style and sense of space and environment are things Zillow and Redfin don't know how to sort [except in the crudest of ways], so the platforms would like to eliminate them from the equation. Platformization and greigification go hand in glove.

At its crudest, this reduction to lowest common denominators renders houses scattered across a school district as identikit as the apartments in a new block of rentals so that, for the benefit of capitalism, they can be marketed the same way. The goal is to take individually built houses and render them as the output of mass production after the fact.

Now ask yourself who benefits from this. The answer is "people who want to buy houses in large numbers as assets without actually looking at them". In other words, people who want houses to be not merely assets, but *commodities*.

And of course, these are not "people" at all, but investment firms.

Ultimately this is a painful echo of 2008. The original goal of CBOs was to financially commodify mortgages regardless of the underlying properties. Greigification seeks to physically commodify the properties themselves.

p.s. If you're interested in this kind of thing, you should be following Kate's blog, McMansion Hell and her column in The Nation.

Utopia

2025-09-03T11:58:00.007-04:00

Random thought: are we heading for an economy where the 1% and the 99% become completely economically disconnected? They will control AIs* to do mental work and robots to do physical work and massive amounts of wealth, and so they will have nothing we can afford and we will have nothing they want.

At first it sounds like one of those scifi dystopias where the poor live on a poisoned, ruined planet and the rich live on floating techtopias**, living off the crumbs that fall from their tables, except for the fact that they live in compounds rather than sky islands. But it could go differently.

Before I go any further: please do not piss on my parade. If you think my thought here is hopelessly utopian, you are probably right. I just don't want to hear it right now.

Imagine we choose to economically disconnect from them. They have all the dollars, so we won't use dollars. Their money is no good here. We farm and make things and perform and create arts and take care of each other in our own economy, independent of them, with our own currency or none at all***. Our economy would be based on the value of labor and its exchange, not capital. We can live on real food and read books and listen to live bands and watch actors on stage and care for each other while they eat highly processed junk and stream and read AI generated algorithmic slop while their best friend is a robot butler.

We don't need to overthrow them, as communist manifestos assume. We can just ignore them as they self-isolate, geographically and socially and economically. Now, an obvious objection to this is that they might send in security forces to tell us we can't farm this land because it belongs to them, or that we have to pay them taxes, or to take our produce. In other words, to treat us as an occupied country. However, there are more of us than there are of them. Many more. It would be the kind of occupation where they control only whatever square yard of land they have a solider standing on at any given moment.

Of course, this would mean giving up a lot of technology, but if we're honest, a lot of technology has not made our lives better. We work longer hours than pre-industrial peasants, have less leisure, are more stressed, and spend our time on social networks that make us unhappy by design.

The one great loss would be modern medicine. But considering how unaffordable that is to many Americans already, and how unavailable to most of the world population anyway, that's worth considering. Or maybe it's the one thing we trade food to the rich for.

Anyway, that's my utopia. What's yours?

—-

Now the footnotes.

* Useful AIs, not LLMs, which are the dumb animal trick of AI.

** Techtopia is a perfectly valid neologism. Thomas More created "utopia" in 1516 by latinizing greek roots meaning "no" and "place". "Techtopia" parallels that construction. (The root of "tech" is "to weave", by the way.) Arguably it should be Technotopia, since techno- is the combining form of the word, e.g. as in technology, but I think techtopia is snappier.

***The alternative to currency is not barter, as many would have you believe, but ledgers and optionally fixed rates of exchange for commodities. Ledger-based trade has existed successfully for hundreds of years at a time in thousands of communities, often in parallel with official currencies and barter for untrusted outsiders. See "Debt: The First 5000 Years" by David Graeber for more exposition than I can fit in a Bsky thread.

A Brief History of Trumpistan

2020-12-12T07:19:00.000-05:00

January 21: A coalition of eighteen states led by Texas announce their succession from the United States, forming a new country reviving the name The Confederate States of America, or CSA. The Internet is thrown into a frenzy over whether to call them The Confederacy of Dunces or Trumpistan.

January 22: The CSA issues a correction to say that they meant "secession" all along, but a software bug planted in Google Docs in collaboration with Hugo Chavez auto-carroted it.

Later that day a massive convoy of gun-carrying CSA supporters in pickup trucks adorned with Trump 2020 flags arrives at Fort Sumter. Upon arrival they discover that the fort, which has not been an active military installation since 1947, is only accessible by boat. They mill around in confusion for an hour, fire a few shots in the air for the look of the thing, and return home.

January 23: Mexico announces plans for a wall along its border with Texas. So does New Mexico.

January 24: The United States recognizes the CSA and announces the closure of all Federal facilities in the CSA, including research labs, airports and military bases, decimating the economies of many towns. The Federal government also announces that drivers' licenses or other ID from secessionist states will no longer be accepted for any purposes. Many citizens of the CSA are stranded in Federal states, unable to board a plane, rent a car, or buy alcohol or tobacco. The latter causes widespread panic among the CSA refugees.

January 25: Various Federal states announce that cars with plates from the CSA states are no longer legal on their roads and must be registered in a Federal state. Drivers from West Virginia get pulled over in massive numbers in Virginia, Pennsylvania, and Ohio. Unable to pay the fines, their cars are seized and crushed into scrap metal, in most cases significantly increasing their value.

January 31: The Federal government announces that as of February 1, it will no longer pay Medicare claims from the CSA. There is widespread panic among the citizens as they realize that their new government is completely incapable of providing them with diabetes supplies or Hoverounds.

February 1: The CSA states meet in constitutional convention at the Austin Convention Center. They meet in the Starbucks as the Center itself is fully booked between an arms and ammo show and a pharmaceutical sales rep convention. Donald Trump is elected Interim President For Life.

February 10: The other six members of the Colorado River Compact announce the expulsion of Utah and plans to build a canal to divert the river around that state. Desperate, the male citizens of Salt Lake City take to the streets in a massive protest. Since this is Utah, it is the most well-behaved, conservatively dressed street protest in the history of the Americas. The women of Salt Lake City fortify the protesters with huge quantities of green Jello.

February 11: Green Jello shortages across Utah drive panicky protesters back into the streets. There is polite rioting and orderly looting of grocery stores. In desperation, many turn to yellow and red Jello.

February 28: CSA citizens begin to notice that no Federal Social Security payments have been received all month. Unable to pay their rent or afford food, white citizens forage for essential supplies, often liberating them from stores without paying, while black people loot.

March 31: After a month of chaos and disorder, Texas asks to rescind its secession. The Federal government accepts it back under strict conditions regarding the fair conduct of elections.

April (various): One by the one the other CSA states also ask to rejoin the Union. They are all readmitted, except for the Dakotas, which nobody wanted in the first place.

April 30: The CSA is formally disbanded. Donald Trump remains Interim President for Life.

Turning in my cool card

2019-06-09T08:31:00.005-04:00

OK, confession time. This is a list of some of the things and people I never really found funny, even though I may have pretended to like some of them at the time just to be cool with my friends:



The Goon Show
Spike Milligan
Kenny Everett
Steptoe and Son (Sanford and Son for those of you reading this in American)
Lord of the Rings 
The Young Ones in general, Rik Mayall in particular
Absolutely Fabulous (other than Joanna Lumley)
Ben Elton
Blackadder, Mr Bean, and frankly most of Rowan Atkinson's output except for a handful of sketches
Alexei Sayle
Pretty much the entirety of the 1980s UK alternative comedy scene, come to think of it
Bill Murray, except Ghostbusters and Groundhog Day
National Lampoon, especially Chevy Chase 
John Hughes
John Waters

And just for completeness, I lost patience with David Lynch somewhere around 1990. Great, David: nothing is what it appears to be. What the fuck is it then?

Phuh. Feels good to get that off my conscience.

Why we don't live in a simulated universe

2017-01-10T20:15:00.002-05:00

There's an oft-repeated theory that our universe is a simulation -- a computer program (or equivalent) created by some higher form of intelligence. The modern popular form of this claim is generally attributed to philosopher Nick Bostrom, although the basic idea goes back much further.

And the only problem with this idea is that it is completely wrong.

The basic "simulation argument" goes like this: imagine that an intelligent race becomes intelligent enough and powerful enough that they could simulate a universe in a computer. (We already do this ourselves, in a very crude sense, when we create computer models to simulate weather or traffic or any other aspect of the real world.) Our hypothetical aliens are able to build such rich simulations, they actually contain simulated intelligent beings of their own -- and those simulated beings would (somehow) perceive themselves to be conscious.

And here's the clever twist: according to the argument, those simulated beings could become intelligent enough to build their own simulated universes, with simulated intelligent beings of their own, who in turn... Eventually, there would be an enormously large pyramid of simulations-within-simulations. And from a simple probabilistic perspective, it's enormously unlikely that we happen to be in the topmost and only real universe (and sometime in the future will ourselves start simulating universes) rather than one of the vast number of simulations.

And this is completely mistaken.

The problem with the argument is that the universe we find ourselves in is enormously complicated from the point of view of having intelligent beings in it. For a start, you could discard the other one hundred billion galaxies in our observable universe and it wouldn't make any difference to us. So it's enormously more likely that the simulated universe we are in would be much simpler than this one. (How much more likely? Borrowing an argument from Roger Penrose, possibly something of the order of 10 to the power [10 to the power 100] -- a 1 with [10 to the power 100] zeroes after it -- more likely.)

So the simulation argument turns on itself: the exact same argument that leads to the conclusion that we live in a simulation, i.e. that there are many more simulations than real universes, also inevitably leads to the conclusion that this universe isn't simulated, because there would be hugely many more simpler simulations we would be more likely to find ourselves in.

Batman v Superman: Dawn of Just a Minute...

2016-03-27T09:20:00.000-04:00

The internet at large has already covered a lot of what's wrong with BvS, so rather than repeat what's already been said, I'm going to restrict myself to a couple of major things not much touched upon, specifically: the Act 3 climax is a huge mis-fire; and the post-climax codicil makes no sense whatsoever.

First, the climactic battle with Doomsday. The problem here is: who really cares? Comparisons to The Avengers are inevitable, and in that movie we've had all kinds of foreshadowing and build-up: the Avengers must stop Loki from using the Cube and opening the portal, failing every step along the way, until the emotional climax of Stark laying down his life... In BvS by contrast we get a rock-monster with arbitrary powers and an equally arbitrary weakness, that appears deus ex machina (quite literally) with no motivation nor character of any kind, and that is not set up in any emotionally meaningful way by preceding events or threats. And even ignoring the disconnect from the foregoing story, there's neither a logical reason that the Kryptonian spaceship even has the ability to create a Doomsday nor a narrative reason that Lex chooses to do so (contrast Avengers, where opening a portal is Loki's motivation from the very beginning).

Consequently, here there's no sense whatsoever that we're building towards this apocalyptic battle -- a problem highlighted by the fact that Wonder Woman decides to get involved in the fight for no adequately explored reason. (More generally, Wonder Woman is woefully underdeveloped -- and not in an intriguing, "show me more backstory!" kind of way, but in a frustrating "what does she want? why is she doing that?" way.) In fact, given that Luthor's main plot is all about manipulating Superman and Batman over many months into fighting each other, the whole Doomsday plot line feels like it was left over from an entirely different draft of the script. Having made the Batman v Superman conflict the core of their movie, the writers apparently had no idea what to give them to do once they had resolved that conflict.

Second, the post-battle State funeral. Why? In the Death of Superman comic book source material, this makes perfect sense. In the comics arc, Superman is a long-established hero, known and trusted, even loved; and the world watches as he fights Doomsday all the way across the country for days on end, other heroes falling by the wayside, until finally, battered into exhaustion in full view of friends and news cameras, he sacrifices his life to save the world. Of course the world mourns. But in BvS, (i) Superman is mysterious, distrusted, and even disliked; (ii) Doomsday appears out of nowhere and spends around twenty minutes in Metropolis, hardly enough time for everybody to decide that we've tried everything and the world is going to end unless Superman can stop it (frankly, anybody that was there for Zod is probably thinking "meh, I've seen worse"); and (iii) nobody witnesses Superman's self-sacrifice and death except Batman, Wonder Woman, and Lois Lane... but their word is good enough for the US government to throw a funeral fit for a president.

On reflection, the two best sequences in Dawn of Justice are (i) Batman rescuing Martha Kent, and (ii) Wonder Woman fighting Doomsday. The former is the one fight scene that is most true to the Batman character (I wouldn't be at all surprised to learn it was done entirely by the Second Unit); and the latter the only part of the movie where anybody seems to be having fun. Like Doomsday, Wonder Woman seems to have wandered in from the theater next door where she had been starring in a movie that was a lot more fun than the one I was sitting through.

And so it struck me: DC could in fact have made a far more interesting movie if Superman never appeared at all. Sure, he's out there in the world somewhere, motivating Lex and the others to their actions, but never actually seen. Edit out every scene with Kent or Superman (except maybe Bruce's nightmare sequences), give Wonder Woman some proper background and motivation, and you've probably got a pretty decent movie about how the rest of the world feels about Superman, and how it copes when he doesn't come flying to the rescue.

Quantum entanglement does not work like that

2015-12-05T15:43:00.001-05:00

Whenever the topic of quantum entanglement -- which Einstein decried as "spooky action at a distance" -- comes up in online conversation, somebody will always ask whether this phenomenon can be used for instantaneous communication. And this is a very reasonable question because although the answer is definitively No, it's far from intuitively obvious why this is so, not least because it depends on details of quantum behavior usually omitted from non-technical explanations -- details that are critical to understanding the phenomenon.

I originally wrote the explanation below in response to a post on Gizmodo. Several people said it was helpful, so I decided to preserve it online for when the question inevitably comes up again.

The Very, Very Short Version

Entanglement allows you to infer what result somebody else's experiment will get; but it doesn't allow you to influence what result they will get.

The long version:

First, entangle your electrons

Suppose you “entangle” two electrons (there are lots of ways to do this; we'll take it as given). What this means is that they are paired in such a way that certain of their properties are reflections of each other. (In technical language we would say they have a "shared state".) In particular, we are interested in the so-called "spin". So you send me one electron and keep the other. Now you measure yours to see if it's spin is pointed up or down; if you find yours is up, you’ll know that if I do the same experiment, mine is pointed down; and vice versa. (The entangled electrons are always opposite, like two sides of a coin).

Importantly, you won’t know whether you’ll get up or down until you do the experiment -- it’s a coin toss. The only way to tell which is the Up electron and which is the Down, by definition, is to do the measurement.

Anyway: so far, so normal. Up to this point, it's really no more surprising than if you had split a coin down the middle and sent one half to me. It's no surprise that if you kept the heads side, I got the tails side.

But note the really important part here: I can't use this to send you a signal. The typical misunderstanding at this point is to think that since the electrons are always opposite, if I somehow force my electron into the Up position before measuring, yours will instantaneously be in the Down position, and from there with enough entangled electrons I can easily construct a binary code. And the simple fact is, entanglement does not work like that. Although the electrons are opposite to begin with, anything I do to change the state of my electron does not change the state of yours; instead it just breaks the entanglement. I can no more flip your electron by flipping mine than I can turn your half of the coin from heads to tails.

Let's get spooky

But now it gets quantum. Unlike a coin, there are lots of ways you can measure spin: in fact you can choose any axis you want to measure it along. You don’t have to measure whether your electron is pointing up or down like this: |. You could measure whether it is pointing left or right, like this --. Or along any in-between axis, like / or \.

Now here's the critical part: electron spin is quantized. This means that whatever axis you measure spin on, the answer will always be precisely "+1" or "-1" units of spin (using the units that physicists typically choose), regardless of what state you thought the electron was previously in; in other words, either clockwise or counterclockwise. Yes, even if you think your equipment only generates up and down electrons, if you choose to measure it on the left-right axis, its spin will definitely be measured as either one unit of left or right spin. Oh, and of course if I measure mine on the same axis, it is pointing the other way. Or you could measure it on any orientation in between, and if I measure it on the same orientation, I get the opposite.

There is no analogy in the macroscopic world for this behavior that I can think of. If you had, say, a spinning basketball and you measured it's spin as "+1" in the up/down axis, it's spin on the left/right axis would be 0, and its spin in the / or \ directions would be somewhere between 0 and 1. This is a crucial difference between the quantum world and the familiar classical world.

One of the things this tells us is that, unlike basketballs and other classical objects, electrons don't have a definite spin until you measure it (and even then, that spin is only good until you measure it again on a different axis).

It gets worse (or maybe better)

Now, we’re not done. Up to now we've always measured our electrons on the same axis. It gets even spookier if you and I choose to measure our electrons along different orientations.

Suppose you measure on the | axis and, say, get Up; but I choose to measure on the -- axis. Now two things I said above seem to be in conflict:

entangled spins are always opposite, so mine must be Down; but
if I measure left/right I must get precisely left or right.

So what happens? Well, in fact I get left or right, and with an equal chance of each. It’s as if my electron was pointing Down after your experiment, and randomly chose which of left or right to flip to when I measured it.

Notice, by the way, that when I do my measurement, nothing now happens to your electron. If you were to subsequently measure your electron on the -- axis, your result would be completely random. The moment you measured your electron the first time, the entanglement was over. So no amount of cleverness with repeated measurements will let me send a signal either.

The really hard part

Now I do something even more interesting: instead of measuring --, I set my equipment at an angle to yours, lets say at /. If we think of a clock face with Up/Down at 12 o’clock / 6 o’clock, I set mine at 1 o’clock / 7 o’clock. Now what happens?

What I find is that when your result is Up (12), I’ll get 7 most of the time and 1 some of the time (the exact proportions can be predicted, and have been demonstrated experimentally literally billions of times). And if your result was Down (6), I get the opposite results; mostly 1, some 7. Somehow, my electron “knows” what axis you measured along and what result you got -- even though the orientation was not fixed at the beginning before the electrons separated. In fact, even the orientations of our measurements can be chosen long after the electrons have separated, yet the entanglement still occurs.

So maybe there's something here that can be used to communicate? Maybe you can send a signal with the way you choose the axis you measure on, since that influences the distribution of my measurements on a different axis?

Unfortunately, no. And the reason is this:

Remember that when you measure on your end, you always get a random result, either up or down. You can’t force your electron to Up, and thereby influence my distribution; you can only discover whether it is Up or Down (and then infer what I am seeing). You can choose the axis you measure on, but not the outcome you get. (You can't even "separate out" the Up electrons from the Down: the only way to know which is which is to measure them, which destroys the entanglement.) And since you are getting 12 or 6 at random, to me it looks like I'm getting 7 or 1 at random too.

One last throw of the dice?

So perhaps there is one last loophole. If being entangled affects the measurements I get, maybe there is some way I can tell whether our electrons are still entangled? Since entanglement breaking is also instantaneous, maybe that in itself can be used to send a message? But no. Even while our electrons are still entangled, your stream of results looks completely random to you. Similarly on the other end, whatever I measure looks completely random to me: 1 or 7, 7 or 1, with no pattern. It’s only when we bring our results together that we see that whenever you got 12 I was more likely to get 7, and whenever you got 6 I was more likely to get 1, thereby proving that our electrons were entangled.

This is what physicists mean when they say our results are correlated, and the degree of correlation (as mentioned above) is precisely predictable, and has been tested in the lab. But it's only by bringing our results together that we see the correlation -- in isolation, each of us appears to get a random series of results. And bringing our results together to compare requires conventional slower than light communication.

(By the way, this is the basis of quantum cryptography, but that's a long story for another time.)

So in summary...

A lot of the confusion here comes from non-technical explanations being loose in their language when they say that one electron "influences" the other. This is true in the sense explained above -- the result I measure is linked at a distance (yes OK, Albert, "spookily") to the result you measure. But it's not true in the sense that you could change your electron and instantaneously cause a change in my electron. Any change you make to your electron in an attempt to change mine simply breaks the entanglement, and our results are no longer connected in any way.

Experimental theology: religious football

2015-09-24T21:39:00.000-04:00

Somewhere between one third and one half of Americans believe that God / Jesus cares enough about the outcome of sports contests to intervene, typically in favor of those who pray most fervently. I propose to put this belief to the test with the new game of Religious Football.

The game is very simple. It is played on a conventional American football field with a standard ball. The game begins with the ball at midfield on a tee, and two teams of eleven prayers line up on opposite sides of the field, five yards from the 50 yard line. Each team prays as hard as it can for the ball to move towards the opponents' end zone. Prayers can be spoken or silent, according to each team's ecclesiastical tradition.

If a team manages to pray the ball across the line, they score a point, the ball is re-centered, and the process begins again. After 60 minutes, the game ends and the team with the most points win.

This is a game where the "twelfth man" is exceptionally important. Supporters are allowed, even encouraged, to pray along with their team to help move the ball. (Conversely, the 13th man will be hung from the goalposts at half time).

There are a few other rules and penalties, to maintain order. The major ones include:

Offsides: The players must maintain five yards from the ball at all times, so if one team's prayers cause the ball to move, it can advance and the other team must retreat. Approaching closer than that incurs a five yard penalty.
Illegal touching: touching the ball in any way, or causing it to move with anything other than the power of prayer, is a ten yard penalty.
Out of bounds: any reference to an opponent's mother, sister, or other female relative is completely out of bounds and will be penalized ten yards.
Roughing the pastor: any contact with the opponent's spiritual leader on the sidelines results in a 15 yard penalty.

I propose that we launch this game in Texas where, I'm told, both Jesus and football are popular.

I Hate Birthdays

2015-06-25T10:06:00.001-04:00

The thing I hate most about birthdays in the Web era is the absurdly insincere birthday greetings in email and on FB from corporations that happen to have my birthday in their database. What am I supposed to think about "good wishes" that don't emanate from any actual person? At best, it's an attempt to co-opt the natural human reaction of reciprocity; at worst, it's a crude sales pitch (who doesn't want a new weed trimmer on their birthday, right?).

If I wanted to read meaningless, empty, formulaic wishes that don't genuinely emanate from any real person with real feelings, I would go stand and stare in front of the birthday card rack at Hallmark for an hour.

At least, that's what I used to do before the restraining order.

Some Thoughts On Jurassic World

2015-06-23T13:30:00.001-04:00

Oh, and SPOILERS, obviously.

Here's a couple of thoughts about Jurassic World that I haven't seen mentioned elsewhere.

1. Owen (Chris Pratt) is actually responsible for hundreds of deaths. If instead of trying to escape from the Indominus Rex compound he had heroically accepted his fate and sacrificed his own life so that the others could escape without releasing the dinosaur, nobody else would have died. Also, the movie would have been over much more quickly.

2. Everybody online is complaining about Claire (Bryce Dallas Howard) running around the woods in her high heels and never once sinking in, losing a shoe, or breaking a heel. I think the director missed a great opportunity to capitalize on that. When Owen is pinned down by a pterosaur and Claire saves him, instead of shooting the pterosaur she should have spiked it in the head with her heel.

And then she and Chris could have exchanged some witty banter about how he's sorry for mocking her footwear, while all around them people continue to be dragged to their horrible deaths, all because Owen didn't sacrifice himself in the first act (see point 1 above).

3. As an aside, Claire is obviously not from New York or she would have a pair of sneakers in her purse that she changes into when it's time to run for the train.

4. I don't think I've ever seen such gratuitous product placement in a movie ostensibly about the evils of over-commercialization. Even in actual Mercedes commercials the camera doesn't caress the bodywork so lovingly before coming to rest on such a prominent shot of the emblem. The director of this movie either has the most profound sense of irony on the planet, or none at all. I'm not sure which.

How to win bar bets with Wikipedia

2015-05-19T10:02:00.000-04:00

Step 1: Edit Wikipedia to insert a fake "fact". Choose your fact carefully: it needs to be unlikely enough that your mark will bet against it, but not so crazy that it will provoke obvious incredulity ("Prince Philip, the Duke of Edinburgh, is a Furry"), causing the mark to doubt the veracity of Wikipedia. You also need to be sure that your edit won't get quickly reverted, so stay away from entries that are closely watched, controversial, or recently in the news ("in 2014, more goats were killed in rail accidents in the US than people").

Step 2: Choose your mark and place your bet.

Step 3: "Prove" your claim by looking it up on Wikipedia. Collect your winnings and leave before the mark checks other sources or your Wikipedia edit gets reverted.

Physics Problem: barometers and building height

2015-04-15T09:27:00.000-04:00

There's a physics problem that typically gets presented to children when they learn about pressure (air, water, and often mercury) and barometers. And it seems to me that the problem is broken. The question is: how could you use an ordinary barometer to measure the height of a tall building? And the expected answer is to measure the air pressure at the top and bottom, and then knowing the weight of air, compute the elevation change.

But let's check the feasibility of this with a quick back-of-the-envelope calculation. For any realistic earthbound circumstance, we can assume that the pressure drops linearly with altitude; see the chart below. For reference, Denver, Colorado is at about 1600m, and the highest town in Great Britain is under 500m; we won't find much in the way of tall buildings above an altitude of 4000m.

("Atmospheric Pressure vs. Altitude" by Geek.not.nerd - Own work. Licensed under CC0 via Wikimedia Commons)

So what would our barometer tell us? Since we're just investigating the feasibility here, we're going to round things a little to make the math easy. Don't worry, no truths were harmed during the making of this calculation:

For every 1000m of altitude gained, the pressure drops ~10kPa, the chart tells us (at least, over the range we are concerned with).
Thus for each meter, the pressure drops ~10Pa; that's 0.1hPa. (1 hectopascal or 1hPa = 100Pa, and is the modern unit equivalent to millibars, commonly used in meteorology.)

A typical household digital barometer can detect a change of +/- 0.5hPa (50Pa), and an analog "certified precision" $600 aneroid barometer is only accurate to 1hPa (100Pa). So with one of these instruments, we can hope to measure building height to, at best, an accuracy of 5 to 10m -- maybe good enough to estimate the number of stories, but not the height.

Fortunately there are two other possible ways to use a barometer to determine a building's height:

Drop the barometer off the top of the building and time how long it takes to hit the ground below. For a building in the range of 100m to 200m, timing accurate to 0.01s would give a precision of around 0.5m, so we will probably want to use some kind of electronic timing device rather than a hand-operated stopwatch. (With manual timing we could reasonably only count on a timing accuracy of 1/10s, which by coincidence converts to about the same height accuracy as the digital barometer.) For example, we could have synchronized clocks at top and bottom, an electromagnet release that records the start time and a sound-activated circuit to record the stop time. For a heavy barometer, we can ignore air resistance.
Find the building custodian and say to him "If you can tell me how tall this building is, I will give you this lovely barometer". This is definitely my favorite solution.

NOTE TO STUDENTS: do not use this answer in any test unless you are very sure about the sense of humor of your teacher.

The American problem

2015-04-13T09:20:00.002-04:00

The fundamental tension in America is that the red states want to be Sparta and the blue states want to be Athens, and the only thing that unites them in common cause is fear of Persia.

On the intractability of free will

2015-04-10T08:31:00.000-04:00

[Author's note: the thoughts here originated as a Letter to the Editors at New Scientist, in response to a somewhat throwaway remark, in an article about randomness, that chance may be essential to the existence of free will. I felt that the point deserved delving into in more depth. New Scientist did publish the letter, but as is typical edited it down for publication -- in particular, many of my adverbs did not survive. Consequently, I wanted to share the full text here.]

Randomness may be necessary to "admit free will" in an otherwise-mechanical universe ("Chance", New Scientist 14 March 2015, p.28ff) but by itself it is not sufficient. It's hard to argue scientifically about the existence of free will in the absence of a rigorous definition of what it is, but we can say something about what it does. And at a minimum, it's existence requires that the outputs of my brain -- my actions -- are not completely determined by the inputs plus initial state. This is, of course, an astonishing proposition that is contrary to any other known physical system or law. Even if we introduce randomness, we merely allow a range of outcomes distributed probabilistically, but we still have no element of intentionality or purpose, the other essential ingredient in free will. Randomness alone would make us no more free than tumbling dice.

One intriguing possibility, however, is that whatever free will actually is, randomness provides a means for it to influence the brain without apparently violating known physical law; a curtain behind which it can hide. Imagine that free will is able to influence apparently-random outcomes deep in the brain, to achieve a desired output, but is also constrained by the need to appear random over the long term. The brain would be like a rigged casino where the roulette wheel comes up red or black at the casino's own choosing, but it must still ensure that the two come up equally over the long term if it is not to be caught breaking the rules. Correspondingly, we might speculate that free will rigs the brain game by influencing individual apparently-random quantum outcomes, which chaotic systems in turn amplify to macroscopic scale, but is limited in the long run because the overall outcomes must match our probabilistic quantum expectations.

Intriguingly, existing psychological experiments are consistent with this model of free will. For example, we know that behaviors that are usually considered exercises of free will such as "paying attention" or "resistance to temptation" are limited and can be exhausted, requiring time to recharge, even though they don't seem to be associated with anything as obvious as depletion of specific neurotransmitters or saturation of synapses. Yet this is exactly what we expect if free will can only influence a limited number of outcomes while staying hidden within known physical laws.

Whatever free will turns out to be -- assuming it exists at all -- understanding it will take at least as great a conceptual leap as that from classical mechanics to quantum theory. And perhaps it is only the reality of chance that connects these three views of reality into a consistent, scientifically explicable universe.

Athens and Sparta: A Parable About Open and Closed Source Software

2015-04-01T08:13:00.000-04:00

Among all the city-states of Classical Greece, the most famous are certainly Athens and Sparta. Sometimes allies, often enemies, despite their shared language and culture, these two could not have been more different. So in the rivalry between Athens and Sparta, who ultimately emerged the winner?

In the 5^th century BCE, the dominant city-state was Sparta. It was hierarchical, authoritarian and ruled by tyrannical kings and aristocrats. It’s greatest cultural values were discipline and conformity, and the kings of this highly militaristic state were also its generals. Sparta was incredibly effective at concentrating its resources to conquer a chosen goal – the phrase “the tip of the spear” could have been invented for them. As a result, Spartans were feared in battle across the Greek world, and Sparta was able to impose its military will on its neighbors.

But then, Athens began to rise to prominence and oppose the hegemony of Sparta. It became a famous center of creativity in the arts, learning and philosophy, home to Plato's Academy and Aristotle's Lyceum. Athens also gave the ancient world Socrates, Pericles, Sophocles and many more philosophers, writers and politicians. Its schools and forums were often lively, open-air marketplaces for competing ideas. It thrived on chaos. Even more remarkable were its experiments in democracy that included a unique combination of direct and representative democracy: everybody was expected to participate in and contribute to Athenian civic life. In stark contrast to Sparta’s general-kings, Athens elected its generals according to the needs of each war.

For a century, Athens and Sparta were in almost constant conflict for dominance of the Greek world, pausing occasionally and briefly to unite against a common enemy. Finally, in 404BCE, Athens was defeated for good and fell under Spartan rule. So did this mean that Sparta had won? Not exactly: Sparta’s dominance was short-lived. Neither Athens nor Sparta ever fully recovered from the costs and destruction of their wars, which impoverished most of the Greek world and ushered in the end of Greek pre-eminence.

So if both Sparta and Athens lost, who won? While Sparta and Athens were exhausting themselves in civil war, far to the west a small village called Rome was growing into a regional power. Rome was something strange and new: it borrowed many ideas from the Greeks, but had no real artistic culture of it’s own. Its sculpture, painting and poetry were second-rate derivations, sometimes even direct copies, of the works of the Greeks. It contributed no significant advances in mathematics or science, and barely anything to philosophy. Even the gods that the Romans claimed to worship were obvious imitations of the Greek pantheon. And yet, the Romans were exceptional engineers, great builders and implementers of others’ ideas. While the Greeks declined, Rome conquered a vast empire, convincing native populations almost everywhere that it was in their best interests to assimilate into Roman ways.

In the end, neither Sparta nor Athens won: both lost to Rome.

De-cluttering

2015-03-27T10:12:00.002-04:00

My three step plan for de-cluttering my house:

Rent a storage locker
Fill it with all the junk that I never use and / or really don't need
Default on the rent

Diet

2015-03-25T18:30:00.002-04:00

A friend of mine who is big into "natural foods" told me never to eat anything I couldn't pronounce, which is why I don't eat quinoa or acai.

What would Jesus do?

2015-03-19T09:33:00.001-04:00

A church in San Francisco has promised to remove controversial sprinklers it installed to deter rough sleepers, reports the BBC. "After an outcry, the city's archdiocese admitted it had been "ill-conceived" for St Mary's Cathedral to treat homeless people in this way", it goes on.

The new policy replaces the sprinklers with landmines and automatic machine guns.

Physics and the Marvel Movies

2014-12-05T09:16:00.001-05:00

Broadly speaking, the Marvel studio movies have managed to remain largely physically credible; and by this I mean that, while there are conceits that you simply have to accept for the sake of the story, and much of what goes on is often beyond current engineering, medical science, and so on, it is at least plausible. For example, in the Iron Man movies, the suit itself is a fairly reasonable extrapolation of current and experimental military exoskeletons; the arc reactor power source, however, you're just going to have to take at face value.

By the way, I'm referring here to the interlocking movies produced by Marvel themselves, also known to fans as the MCU, for Marvel Cinematic Universe. The movies made by other studios, such as the X-Men and Fantastic Four franchises, threw credibility overboard a long time ago.

Next year (2015), the MCU is going to get seriously weird, however. With the introduction of Quicksilver and Wanda to the Avengers, and a Dr. Strange movie -- Stephen Strange was name-checked in Captain America: The Winter Soldier, so presumably this will take place in the same continuity -- it's hard to see how Marvel will explain itself without just shrugging and saying "Magic".

Before that happens, therefore, I wanted to jot down some notes on the least physical elements of the movies to date, basically because I enjoy this sort of thing. Oh, and I probably shouldn't need to say this, but obviously:

SPOILERS!

Iron Man 1: Deceleration is the big issue here. Stark pulls some serious Gs in his flight maneuvers, especially when he opens the flaps to evade the fighter jets; but that's not the biggest problem -- let's just accept that he has invented the world's best pressure suit. No, the big issue is when he lands hard, going from full speed to a three-point landing in nothing flat. It doesn't matter how good his airbags are, his body is coming to a stop in a very short period of time. In any realistic scenario, when they open up the suit after a landing like that, they're going to find a can of Tony Stark soup. (By the way, when I first watched the movie, that wasn't the thing that made me go "Oh, c'mon!". No, that was when Tony returned from Afghanistan and he wants a burger... so he goes to Burger King. He's in California: obviously, he's going to go to In'n'Out. Let's try to keep this at least a little realistic, OK?)
Iron Man 2: The "internal problem" in this movie is that Tony's arc reactor is poisoning him so he needs to replace the palladium that is a key component. Using instructions left to him by his father, he creates... a new element. Did anybody involved look at the Periodic Table and ask "Gee, where will this new element, which is chemically and electrically very similar to palladium, fit? I wonder why nobody else noticed that gap?". I suppose it's possible to dismiss this as one of those conceits I mentioned, but a much better solution is at hand: have Tony create a room-temperature superconductor. Not only is this a reasonable extrapolation of current science, it's an area where researchers are exploring many different approaches, so there's plenty of room for Tony to try something new and solve the challenge. Also, Tony is a genius at engineering, not basic science (notwithstanding the Avengers, where he just a generic STEM genius), so it's a better fit for the character.
Captain America: One could quibble about just how the Super Serum works, but the big physical problem here is simply conservation of mass: Steve Rogers bulks up by at least 100 pounds in a matter of seconds, so where did all that matter come from? Note that the naive answer "it came from the energy they drew from the electrical grid" doesn't work, because it takes an enormous amount of energy to make a very small amount of mass. To give a sense of scale, consider the Soviet Union's Tsar Bomba, the largest hydrogen bomb ever tested. That bomb yielded on the order of 50 megatonnes-equivalent, roughly 10 times all of the conventional explosives combined used in World War II. In order to create Steve Rogers' 100 pound gain, you would need to harness the energy yield of approximately twenty Tsar Bombas, and do so in just a few seconds.
The Avengers: This has been well addressed elsewhere, but the most obvious engineering problem is whether or not the helicarrier could fly; and the likely answer is No. At the depicted size of carrier, the rotor blades would have to be much larger. Or at the size of rotor shown, they would have to spin much faster, but then you get into problems of material science (the blades would break apart) or tip speed (what happens if the tip exceeds the speed of sound?).
The Hulk: One of the nicer touches in the Hulk movies (and his appearance in the Avengers) is that they take seriously what happens to the ground beneath him when the Hulk jumps and lands. But as with Captain America above, where does the extra mass of the Hulk's body come from? In the comic books, the Hulk is the result of exposure to a fictional "gamma bomb", but as noted even the largest nuclear explosions convert only a few pounds of matter to energy, so even if you could capture all that energy, turned back into matter it would still only amount to the same few pounds. The most plausible explanation I can come up with is that the Hulk, in fact, weighs the same as Banner and his huge size comes from the fact that he is inflatable -- really, they should call him The Inflatable Hulk. I do realize, however, that this theory may be difficult to reconcile with other depicted elements of the character.
Guardians of the Galaxy: Obviously there's a lot we just have to take for granted in this movie because aliens, but my gripe is with a very Earthbound technology. Peter Quill has been playing the same cassette tape for over 25 years, and it still isn't a tangled, broken mess? He even plays it in a Sony Walkman without damaging it, which is just downright ridiculous. (On a lesser but related note, when he finally unwraps Awesome Mix 2, it's amazing that the tape hasn't degraded to the point that it is hopelessly stuck together.)

I'm sure there's more to be found in the movies not mentioned above, but that's all for now. Comments welcome.

Quantum Leap: the Movie

2014-10-10T08:55:00.001-04:00

Like many people, I found the ending of Quantum Leap unsatisfactory. I've long had an idea for a story that would wrap it up both more neatly and provocatively.

And by the way, if anybody from the copyright holder (or anybody who knows somebody...) happens to be reading: I disclaim all rights in this idea. Use if freely. I'd far rather see this made than get paid (although a "from an idea by..." credit would be nice.)

[fade to black]
Open on: the same set and title card that closed out the original TV series.

Burn in: Dr. Sam Beckett never returned home.
[crossfade to]
Burn in: ...Until today

Open on Sam, emerging from a leap. He is in an anonymous office bathroom, could be anywhere in America, any time from the 1980s to the present day. POV over his shoulder, he looks into a wall mirror and sees...

…himself, as young as he looked at the beginning of the project.

Sam: Oh boy!

[Titles]

The story then unfolds: after many years of leaping, Sam has somehow leaped into his own body. It is 1999 [the "present day" of the project in the original series], just a few days before the experiment that launched his first leap. And Sam has just days to decide: knowing what he knows now, does he take the leap or not? If he does leap, he knows he may never get home again. This may be his one and only chance to break out. But if he doesn't leap, does he change history and erase all the good he has ever done? He has no idea... and no help (at first).

Back in his own timeline [our present day], a long-retired Al dozes in a chair. The QL project was shut down years ago. They had lost contact with Sam, and after months with no sign of him, everybody had assumed he was lost in time. The one exception: Al never gave up hope, and even though the project is mothballed, he still has the comm device gathering dust in a drawer of his desk.

And after all these years it blinks into life, and starts bleeping, waking Al.

So now Al, with the help of a grown-up Sammy Jo, tries to reboot Ziggy, contact Sam in 1999, and figure out the consequences of his decision. But the closer they get to the choice to leap or not, the more erratic and unhelpful Ziggy becomes: instead of converging, her predictions and probabilities are bouncing wildly, as every choice Sam makes seems to involve terrible paradoxes and instabilities. Whatever Sam chooses seems to be wrong...

On the fallibility of autobiographical memories

2013-11-18T16:53:00.002-05:00

I suspect that most people who have not actively studied the subject have a fairly naive view of how autobiographical memories work. They imagine our memories of events in our lives to be little home movies, tucked away in slots in our brains, ready to be recalled when prompted by circumstance or demanded by our conscious selves.

That this model is entirely inadequate was brought home to me the other day when I was recalling a particular drive I used to take on a weekly routine in my early 20s, when I lived in England. The memory was crisp and detailed, including the undulations of the road, signposts to various villages along the route, and the appearance of the landscape at different times of year. Just one detail was wrong: in my memory, I was driving on the right and sitting in the left-hand seat, as one would in America or Europe; of course, since these events took place in England, the reverse would have been how it actually took place.

As I thought about it more, I realized that the same was true for (almost) all of my memories of England involving cars. In my mind's eye I am opening the wrong door, getting in or out of the wrong side of the car, driving on the wrong side of the road. Only by a conscious effort of will can I restore the image in my head to how reason tells me it actually must have happened.

What this tells us is that autobiographical memories are not really like a movie, but more like the script of a movie. Somewhere in my memory is stored a script about that familiar drive, perhaps associated with a high-fidelity description or image of the landscape, and a slug line such as:

EXT. DAY: CARL drives a late-model compact through winding country roads.

...and from that, like a movie director, my brain constructs the movie, using its library of backdrops and knowledge of what driving involves. Only now that I have spent more years driving on the right than I ever did on the left, it defaults to the more habitual perspective, like an American movie director setting a scene in England and forgetting that they drive on the other side there.

I said "almost" above, for good reason. A few of my English driving memories are correctly oriented, invariably ones involving some amount of drama. For example, once while driving on the M25 I was witness to a multiple-car pile-up that caused a huge back-up on both sides of the motorway. In my memory of that event, I remember every moment with great precision, including which lane I was in and how I avoided being part of the accident myself.

Time Travel Does Not Work Like That

2013-10-24T09:28:00.001-04:00

Whenever a discussion thread turns to time travel, somebody will always raise the challenging question: If you jump forward in time, say by a week, shouldn't you reappear in outer space because the Earth has continued to move and is now seven days further along in its orbit?

And I always feel obliged to answer: Time travel does not work like that.

This conception of time travel typically imagines a time machine as a box of some kind that jumps in time but stays in the same place. And written into that conception are some assumptions that mislead. One is the assumption that you can "jump" discontinuously from one point in time to another. A second is the assumption that movement in time can be considered separately from movement in space. And a third is the implication that the expression "in the same place" is well-defined: as Relativity taught us, we have to ask "the same place relative to what? The Earth? The sun? The center of the galaxy?" (and once we answer that question, we realize that we have pretty much answered our own conundrum.) To properly understand what should happen in time travel, we need to overturn each of those assumptions.

So as far as we know* there is no possibility of "a box that travels through time but doesn't travel through space". It's not just hard, it's an oxymoron -- although in order to understand why, you have to teach yourself to think about spacetime properly, instead of thinking of space and time as separable.

So we have to take a few steps back, discard the presumption that such a box exists, and ask what an actual time machine could be like. And it turns out that (realistic) time travel is a characteristic of a region of spacetime, not a characteristic of a particular machine.

The first thing to understand is that nothing ever moves through space alone or through time alone**. Everything is moving through spacetime, all the time (so to speak). And that movement is always continuous. It simply doesn't make sense to say that a particle X moved from time t1 to time t2 without specifying space coordinates too. The only thing that makes sense is to say that X moved from spacetime position (x1, y1, z1, t1) to (x2, y2, z2, t2). This is so basic that, Relativity shows, even basic concepts like "before", "after", and "simultaneous" are not well defined if you don't specific both time and space coordinates.

The second thing to understand is that physicists have dreamed up lots of ways that time travel might be possible, and all of them involve a continuous path through spacetime, not a mysterious jump. The trick is, the spacetime curves in such a way that when you return to the same coordinates in space, you arrive at a different time from, say, an identical twin who stayed home. However, at no point do you perceive anything "weird" or discontinuous happening. Think of it as being like an extreme version of the famous Twins Paradox from Relativity. In that "paradox" you leave home with a clock that reads 2pm, travel in a big loop at almost the speed of light, come home, and your clock now reads 3pm while an identical clock that stayed home reads 4pm. (This happens all the time, on a smaller scale, right here on Earth: the GPS satellites you rely on for satnav have to correct for the fact that their atomic clocks drift slightly from identical clocks on the surface of the Earth). If the spacetime path you follow is sufficiently warped, when you get home your clock might read 3pm while the one on Earth reads 1pm -- congratulations, you've traveled an hour into your own past!

Of course, we should also note that when you return from your big loop you might be a little surprised to discover that the Earth isn't where you expected it to be, it's actually a little earlier in its orbit from where you would calculate according to the clock that traveled with you, so you have to adjust your path in spacetime a little to navigate back to it. But notice there was still no "jump" involved: you traveled away from Earth, you traveled back to Earth, and found something unexpected, because the paths you and Earth followed through spacetime put your clocks out of sync.

Note also that I pulled a little sleight of hand in that paragraph. When I said "where you expected the Earth to be", I should really specify relative to what for the sentence to have any meaning. And what I really mean is "relative to where you would expect it to be if you had traveled at low speed through flat spacetime and your clock had kept time with Earth clocks". This is kind of a subtle point, but it is at the heart of what's going on here. Your clock tells you where Earth "should" be, and relative to your clock Earth has moved "out from under you" -- but that is only because you assume that you and your clock traveled in flat spacetime. If you could look back with a telescope and watch the Earth the whole time you were on your trip you would see nothing odd happen, other than that it's position drifts slowly more and more backwards from where your clock says it should be. But at no point does Earth blink out of view and reappear further back in its orbit, the way a "time jump" is typically depicted in sci-fi.

So really, when I say "return to the same coordinates", I need to specify relative to what. If I "return to the same coordinates" relative to the Earth, it's right where I expect. If I choose some other point of reference relative to which the Earth is moving, it's not.

By the way, one of the first people to demonstrate rigorously that this kind of thing could happen in General Relativity was Einstein's good friend Kurt Godel. He showed that if the universe is rotating and sufficiently large, you could follow a very long loop around the universe and return to your starting point at an earlier time. Reportedly, Einstein was quite upset by this.

Now, when we see time travel in TV or movies, one way to think about it is to assume that the device is creating its own region of curved spacetime that is extremely small and very severely curved. I like to pretend that the time travel in 7 Days works this way: the device creates a highly distorted region of spacetime around the capsule. The capsule travels in that highly distorted region which takes it both into space (relative to the Earth) and back in time (again, relative to the Earth). It then emerges from that distorted region and navigates back to Earth traveling in our (relatively) flat spacetime. But rather than "jumping 7 days into the past", I think of it as "traveling 7 days into the past and elsewhere in space".

Another way to think about it is this: the most consistently realistic depiction of time travel in fiction is wormholes: a wormhole connects two different points in both space and time. If you had a pair of wormholes -- or a single wormhole that connects two points close to each other in space but distant in time -- you would effectively have the classic time machine. And in fact, the wormhole is simply an extreme*** example of curved spacetime.

I have an even longer answer than this that also explains why we haven't met time travelers from the future yet, but it runs to several pages, and I'm saving it for the book I'm never going to write, "Physics for Smarties: an essential math-free guide for curious arts and humanities students".

Anyway, I hope that helps a little bit, and if you take away nothing else, remember "continuous path through spacetime" and "doesn't travel in space -- relative to what?"

Footnotes

*And yes, I readily concede that "as far as we know" is not very far, but the fundamental character of General Relativity is very, very suggestive on this point.

**OK, you could imagine such a thing if you wanted to, but we have no idea what physics would describe it, so basically you could decide how it behaves completely arbitrarily. It does whatever you want it to do. You just have to bear in mind that there are no absolute coordinates in spacetime, so if you define that your box "doesn't travel through space", it's up to you define what you mean by that: doesn't travel relative to what frame of reference? In short, your time box does whatever you choose it to do, because you are making it up.

***Insert your own Wormhole Extreme! reference here.