# Good Design and Empathy

Let me pick on DMV a little, but for a good reason – not just to complain about this much-disliked organization.

I registered my car in the California DMV more than a year ago. Since then I've familiarized myself with HOV lanes and their rules, and, consequently, the Clean Air Vehicle decals. It was learning through osmosis: I kept seeing these diamond shapes on the highway and the signs that informed me of the HOV lane rules. Later, by observing other cars on the road, I've noticed enough of the decals around me to spot a theme and wonder what they are. A quick google search confirmed what I had suspected: if your car satisfies certain requirements, you can purchase a decal, which lets you ride in the HOV lane when normally you wouldn't be allowed to.

I thought it might be good to get one, especially that I knew that my car satisfies the conditions. So I scrolled half way down the DMV webpage that Google found for me and found the link to the fillable PDF, which I downloaded and filled out. The form was mostly intuitive. In a few places I had to refer to my documents. There was a section at the top of Page 2 that I almost missed. And once I printed out the form, I noticed that the PDF software (Preview) messed up a few fields, which I had to correct in black ink. Then I put the form in an envelope, enclosed a check for 8, and mailed it out. Two or three weeks later, I receive my decals in the mail. I haven't put them on my car – the decals are sort of ugly looking, surprisingly large, and you need to literally plaster your car (with three of them, one from each side). So I'm waiting until I need to use one, for example, I'm in a rush and need to use the highway during rush hour. So far, fortunately, that hasn't happened. Nothing about the above should be shocking to you. I'm sure that you go through a similar workflow multiple times in a week (though – hopefully! – not all of them involve the DMV). It's actually one of the least painful of the DMV workflows. But from the point of view of good design, it's an awful one. It highlights the problem that I've noted hundreds of times, a kind of death of a thousand little daggers. All these suboptimal experiences set a kind of expectation in us; they numb us to the fact that poor user experience surrounds us. How could this experience be better? I like to think of user experience as layers of an onion, and peel one layer after another, at each level asking a simple question or two: what causes the most pain? What creates the most friction? In the case of my DMV decal experience, I think the most surface-level pain was filling the PDF out. It took me a long time, but, more painfully, when I finished filling out the PDF, I wasn't confident that the printed out version will contain all my edits. Why not? Try to fill this form out yourself on a Mac. Some fields (YEAR) replace my value with a 0 on blur. Some fields (UNIT NO) are misaligned. Some fields (top fields on page 2) seem like they are linked to the respective fields on page 1, but the values only show up on focus. Reliability is key, especially when paperwork is required (since the cost of an error is relatively high). So, in this first layer, I'd say that the PDF filling experience could be more reliable and consistent. That would be great. If that was solved, my next complaint would be the efficiency and complexity of the workflow. Why should I have to print out the PDF, then put it in an envelope, and mail it out? Ironically, the technology for fillable PDFs is significantly more advanced that the technology that makes online forms possible. That would save some trees, and save me and the DMV lots of time (let alone simplify my workflow of having to have an envelope, a stamp, and a nearby mailbox). Even in the most basic form (no error checking) it saves me 5 minutes to do the printing and mailing, and it saves the DMV somewhere between 5 and 20 minutes of bureaucracy. In the second layer, the filing/submission experience could be simpler and more efficient. With that out of the way, I'd focus on redundancy. Why do I need to enter all my personal info? The DMV has my address on file; if my address hasn't changed (the 98% use case!), I should not have to specify it. Similarly, the DMV has the VIM, the make, and the model of my car. In fact, all I should have to do is enter my unique identifier (I'd love a username that I keep with the DMV, but a physical ID, or name+license number will suffice) and the engine type/whatever the DMV requires to ensure that I qualify for the decal. Hell, even the latter isn't necessary – the DMV has the VIN, the vehicle make, model and year. Again, in 95% of all use cases, the car automatically satisfies the requirements. The input experience could be more minimal. From here it's not hard to realize that as a user, I should not even have to fill out a form. The DMV knows my registration info, and manages the eligibility rules. So the DMV should automatically – proactively – do the matching and simply send me the decals. They could add the8 fee to the annual vehicle registration fee. In fact, I should get the decals as soon as I register my car – I shouldn't have to wonder why some cars have decals and what they mean.

Of course, a good user experience designer will automatically see through all these layers. In fact, it's relatively easy to envision the ideal workflow that I described above. But  the point is not that the experience could be better. It should be better, and the fact that it's not points to fundamental gaps in how product and service designers (both the fillable PDF makers and the DMV) perceive users, their context, needs, and experience.

What causes this?  At a proxy level, there are incentive issues (the DMV doesn't feel the acute pressure to make the user experience better), use case complexity (I'm sure the makers of Preview tested their software, but I'm guessing fillable PDFs are very difficult to test exhaustively), responsibility issues (there is probably no single person responsible for the entire decal user workflow; and in many cases, the left hand in the organization is not talking to the right hand). But at the fundamental level, this is an issue of empathy.

Many experienced Product Managers will tell you that empathy differentiates a good PM from a great one. But empathy is a quality that needs to be shared by everyone in an organization, not just select employees. It's like common sense or the ability to communicate. And yet, it's far from prevalent. It's that way because companies don't emphasize it when hiring, they don't value it internally, and they rarely reward it. Worse, empathy is often misunderstood. Empathy is the capacity to recognize emotions felt by other people. It doesn't mean the ability to be compassionate (though it's a prerequisite for the latter). It does not mean being "nice" or "fair". To have empathy means to observe the other (easy), to actually listen to the other (hard), and to suspend one's ego (very, very hard).

There were probably dozens, maybe hundreds, or people involved in the design and implementation of the decal application experience. If just one in ten put themselves in the shoes of the end user (a little bit of empathy), they would invariably see the pain that the end user is feeling. If just one in fifty stopped to think about what would make the experience as painless as possible for the end user (a lot of empathy), I wouldn't have needed to write this post.

What could we, mere users, do to make a difference? The simplest thing each of us can do is expect more. Expect to be delighted. Expect to have a pleasurable experience. Train yourself to identify the pain, no matter how small, and talk about it. Complain, be vocal, fill out reviews, call Customer Service. Make it known that user experience is something you value a lot. Be critical of products and services which are unreliable, inefficient, redundant. Don't tolerate even a single little dagger. Organizations – even the DMV – respond to what their customers value. One voice is not enough, but one voice, multiplied a thousand times, is no longer a voice. It's a roar.

Some time ago this "ultimate cheat sheet" circulated through my various social networks. A couple of my friends asked me what I thought of it. My intuitive reaction was a negative one, but I needed to think about why I felt that way. This, in my mind, unraveled into a deeper theme, which I thought worth sharing.

But first, some context.

I am currently in my second year at Stanford Graduate School of Business. Prior to that, I spent six years working in a financial services firm. I left because I wanted to explore the broader world, and get back in touch with my deep passion (solving big problems with the help of software, which has the incredible ability to provide unprecedented leverage to almost any human activity – software is, after all, eating the world). Stanford allowed me to do it in a community of people who have great ideas, are ambitious, and surprisingly diverse (if you know where to look).

Throughout my first year I've taken classes that immersed me in the world of business, and particularly early-stage ventures. I went to panels, where novice, seasoned, successful and failed entrepreneurs alike shared their experiences and gave their advice to wide-eyed business school students. I went to lunches with people who had something interesting to say. I extracted the essence of more than a hundred cases I've covered in class. I read articles that my classmates sent me, scavenged the Web for advice given by founders, CEOs, salespeople, and everyone else. As a result, by the end of my first year, I had an impressive cheat sheet of my own. I keep it in Evernote, titled "business advice", and despite being written in concise, bullet-point form, it now exceeds 20,000 words. So it remains useful, I organized it into about 50 themes over 5 major categories.

As I was restarting this blog, I considered sharing the entire file with the world. Why not? After all, it's a compression of more than a year of advice, given to me in various forms, ranging from very personal to heavily broadcast.

The problem with the advice I so diligently collected, and with James's advice, is that it's useless. It's useless, because it's compressed so much that it becomes almost impossible to apply. It lacks any context whatsoever to be put in practice. It is more than just "dead knowledge". It's knowledge that's been dead for years and is now shriveled, dehydrated and turns to powder as soon as you touch it.

In fact – and this is what was bothering me so much when I read the post – I believe that such advice has negative valueA big problem is that cheat sheets like this give their readers a false sense of security  – a belief that there is "the" right answer. There isn't. The astute adage "Ask ten people for advice and you'll get eleven opinions" is spot on. Every one of these rules is an outcome of a thought process or an experience. Each of them is a black box – whose inputs are the pros and cons, the context that the author faced, and the set of things he valued, and the output is a decision. And so to present these one hundred and three processes (or more, if these rules were came out of several experiences) as rules totally misses the point and encourages the reader to question the world around her less, rather than more.

I have no intention on picking on James. In fact, I am grateful to him for coming up with his 100+3 rules. I was staring at my own advice for more than a year and failed to see what was wrong with it. I needed to see someone else's advice to really get it.

- - -

Even then, it's not enough. I realized that first hand: equipped in this wonderful toolbox, I set out to put my knowledge into practice over the summer, working on a project with a couple of classmates of mine. And we did everything we weren't supposed to do. As I go over my 20,000-word business advice, I can highlight dozens of bullet points that I violated. The problem was not only that there was a lot of advice to absorb. More importantly, each of these bullet points comes with its little decision mechanism, and when you're on the ground, faced with an actual situation, with actual data, things don't look as black-and-white as they do in "business advice".

There truly is no free lunch. Yes, reading a book saves you time. But it's no lossless compression scheme. Reading a bullet point of advice might save you the 2 years (and \$) of business school and 1 year of going out and trying, and failing. But by reading a bullet point, you sacrifice the mental focus that you would subject yourself to if you actually had to read that case, think about that issue, then discuss it with your classmates, then hear the guest speaker's synthesis (which by now has all this wonderful context that you'll hopefully remember, even partially), and then write it up as a bullet point in your own "business advice", and then try it in the world, and fail, and finally internalize what it means.

- - -

I haven't deleted my "business advice" note. In fact, this note has a lot of value to me . It has a lot of value, because I do have the context. So long as my memory is good enough to trigger the circumstances that made me write down each piece of advice, I can use this advice as a starting point to making decisions.

And in fact, that's what advice is meant to be. It was never meant to replace good old thought process. But the more we expose ourselves to information digests, the more we skip the long article and skim over the TL;DR line, the more we shortcut our own thought process, seek comfort in our crutches wherever we go, and aim to become context-free. But – as your computer scientist friends will tell you – "context-free" is not very "intelligent".

# Technology, Venture, and Design

Before embarking on this second incarnation of my blog, I reflected on the past four years of my experiences in an effort to extract a theme closest to my heart. What stood out was an intersection of three areas. I think it's a particularly powerful intersection, one worth taking a deeper look into. These three areas are TechnologyVenture, and Design.

But let's step back a little.

We live in a bimodal age of both specialization and "skilllessness". Some of us specialize – they earn their PhDs, they deepen their understanding of a particular subject matter, they become comfortable in their very narrow and specific job roles. Others go in the opposite direction – they remain "generalists," a term which, more often than not, means having no particular skill but boasting the general ability to deal with people, with maybe an uncommon amount of common sense sprinkled on top. If successful, the former become fantastic individual contributors, and the latter become great managers.

But if we want to aim higher – if we want to change the world in small ways or in big ways, we need to change the way we look at it, and we need to revisit our role in it. We need to know enough about everything to tackle the increasingly complex problems, straggling the increasingly larger number of distinct fields. But we also need to know a lot about enough things to be able to actually make a difference. You may have heard of "T-shaped professionals", having some breadth of knowledge and one area of depth. I want to go one step further, advocating for the need to have deep expertise and experience in more than one area, in addition to the breadth of knowledge elsewhere. At the most basic level, it's because the best insight comes out of understanding several things so well that you can spot the subtlest of connections between them.

There are lots of combinations of areas which can offer such synergy, but I want to focus on three which I think are the most powerful.

- - -

### Technology

Technology truly is the driver of mankind's progress. Technology – literally the act of applying our knowledge – has a transformative ability. An insanely powerful flavor of technology that emerged in the twentieth century – software – is the best testament of that. Software frees us from most physical constraints. You can stack software on top of other software, which lets us create remarkable leverage. Fluency in technology – and software, specifically – is indispensable in the twenty-first century.

Many of the people I interact with hope that a superficial understanding of technology will do. After all, they can outsource the technical work. Well, as many firsthand experiences have taught me, there is absolutely nothing worse than having someone who does not understand technology attempt to manage, or in some meaningful way contribute to a problem that requires technology. Those people are like that broken wheel in the grocery cart – yes, it supports the cart, but it's really not that much more difficult with just three wheels, and boy is that broken wheel frustrating! You have to stop all the time, adjust the wheel and hope that it will continue moving in the right direction.

Here in business school, some of my classmates hope that they can just take an intro CS class and check the technical box. While they will no doubt do very well in that class, I'm afraid it's not enough. The flip side of that ability of technology to provide massive leverage is that to understand (let alone to harness) technology means to have to dig very deep, layer beneath layer, to achieve proficiency. You not only have to be able to write a Hello World! application; you have to understand what makes the computer print Hello World. It's a deep stack to understand, and for that, you also need to have a good command of mathematics. One CS class just won't cut it. It's about a mindset, a way of seeing the world.

I was fortunate to be exposed to leverage-providing technology very early in my life, thanks to my father who foresaw the rise of software and smuggled a computer into the country for me to play with. For those who believe in the importance of technology, but who don't have the background, the best advice I can give is to unconditionally immerse oneself in it. Set a goal – to write a photo-sharing app, or something – and be relentless in getting to that goal. At first, you won't even know what questions to ask. Struggle! Get help, google incessantly, learn by failing a hundred times which stackoverflow comment is useful and which one is useless.

- - -

### Venture

The desire to build a business, or a deep understanding of what makes businesses successful and unsuccessful, is an ability that I only learned to appreciate relatively late in life.

Business is the ultimate applied science. The best way to test an idea is to build some life support around it and open it up to the world, to see if it can survive. You may have arrived upon the best theoretical result, but to change the world, you should turn your theory into a sustainable business. Being venture-minded is also a great way to ensure that you don't solve problems that nobody has, and that you don't just create a science fair project. Subject your ideas to the harshness of reality. If they blossom, you have come up with something of great value.

The best way to acquire a business intuition is to be in business. You have to have enough exposure to what makes a business tick. I spent six years at a company, but – while the management was wonderfully transparent, allowing me to learn what a company should and should not do – I barely saw the tip of the iceberg. That's why I recommend joining a company small enough so that you can understand fully what it does and why it does what it does.

You can also start a venture. The learning curve is steepest, and the things you learn you will never forget; but you will be subjected to the ebbs and flows of luck.

If you haven't had much experience with business, you can try business school. That's what I chose – and I'm glad I did. By immersing myself in a rich ecosystem focused on business issues, I've acquired an intuition I haven't had before. I think about the world differently now. But all the theory, the cases, the conversations are just one part of the equation. You have to go out and apply what you learned.

- - -

### Design

Design, or rather, the art of human experience, is another area that I consider essential. You may have the best technology, and the best business model, but to be truly successful, you have to understand how your product or service integrates with humans, their workflows, their pains, needs and desires.

You can't change the world if you don't interact with humans, be it a product that you design that people want to use (Tesla is changing the world – it's doing so by creating products that people love), or an institution you establish (which consists of a number of human beings), or even a book you write (which is read by humans).

Many of my friends think of design – or the experience that humans have with their creations – as secondary. I think that's what differentiates good solutions from great solutions. You can't outsource design: if you think you can, you betray the critical fact that you don't understand your product and your customer enough.

- - -

Understanding technology, being venture-minded, and caring about design and the human experience are incredibly powerful. In the next few decades, as software continues to eat the world, as technology roles remain the most lucrative, and as techniques such as analytics and hypothesis-driven experimentation push their way into most job descriptions; as consumers and businesses alike continue to demand human-centric products and services that understand user needs and reduce frictions to use; and as more ideas start seeing the light of day in the form of viable businesses, these three areas will seem just as indispensable as the ability to communicate or to use a computer is now.

Better be on the forefront than try to catch up when it's too late.

# Betting on the Timing of an Event

There are times when two or more parties disagree over when a particular event will happen and the disagreement is so strong that people are willing to bet each other. It is common to place “over-under” bets — if the event happens before time T, Andrew gets the money, otherwise Bob gets it. Usually the further the event is from T, the more money exchange hands.

I don’t like this style of betting because it’s not expressive enough. Instead, I prefer to bet by specifying my probability distribution of the timing of the event, and then using these distributions to determine payouts. It's a fun activity, requiring very little mathematics to execute well.

Essentially, each party graphs a probability distribution of the timing of the event — a histogram with the time on the horizontal axis and the probability density function on the vertical axis. The probability density function is simply “the relative probability that the event will happen around the time specified on the horizontal axis”. So if the histogram is twice as tall around 8pm than around 7pm, the event is twice as likely to happen around 8pm than around 7pm.

That’s all each person really needs to do. No need to worry about the area of the histogram summing up to 1 since the vertical axis can be scaled up appropriately. The two people should also agree on how money they are willing to bet — say k dollars each.

When the event actually occurs at time T, the two people compare the value of the probability density function (the height of the bar) at time T on their graphs and pay up based on the difference in these values. The height of each bar needs to be scaled appropriately so that the area under each curve adds up to 1 – that way, no player can cheat by making their graph "taller".

To do the scaling well, we need to calculate the area under the graph. A few heuristics that work include:

• Limiting oneself to "aliased" curves on graph paper, so that the area is simply the number of squares under the curve
• Limiting oneself to piecewise linear curves and doing relatively simple math to compute the area
• Scanning the graph and using a graphics editing application to determine the area under the graph (using e.g. the flood fill and histogram tools)

# Crowdsourced Art

I had this idea to get my friends together to create art. I created a simple tool which allowed them to draw on a small canvas. I gave them a small number of pixels each, but they could cooperate (and earn bonus pixels) or overwrite others' work.

I ran a small iteration of this project back in 2009 with my friends. People had fun so I decided to add a few new features. Currently, the tool has an ability to "mine" tokens directly on the page - with enough patience, you can earn free pixels just by staying on the page. I'm also trying to make it a little easier to draw and explore what others have done.

I hope to be done in a couple of weeks, at which point I'll give all my classmates a chance to contribute with a relatively large number of pixels each. In the meantime, you can play with the test run, by mining the pixels (you can also email me to get a token). The canvas so far is shown below. Click through to contribute!

This is the canvas of the current crowdsourcing art experiment.

By the way, in the 2009 iteration, my friends came up with this:

This is the result of the 2009 iteration of the project.

# The Actual Boston Subway Map

(Originally published August 3, 2010, a lazy many years after the author actually created the map)

Being a son of a seafarer, I developed a kind of fascination with being on the sea, and with maps. It is because of the latter (and because I happened to live in Boston, and because I didn’t quite like how MBTA imitated Harry Beck, and because I always wanted to know how far it actually is between the different subway stops) that in 2005 I decided to make an actual Boston subway map, that is, a geographically-accurate map of all subway stops.

It was several years ago — I believe MBTA may have added a few subway stops since then, and you can also see all these stops on Google Maps, but there’s something elegant in the simplicity of my diagram. It’s also a good case study of Google Maps, scripting and LaTeX.

The idea was to find all the subway stops on a map downloaded from Google Maps using the locations of the stops as reported by MBTA (as you can imagine, it was a humongous pain to click on every single station map to figure out where to actually plot each station), and put the coordinates of each station in a LaTeX file that would generate the pdf image of the subway map. I used pstricks, which is a great LaTeX package for drawing graphics.

Then I opened the large map in Photoshop and figured out the coordinates of each subway station and turned them into a LaTeX file. Finally, I ran LaTeX to generate the following image file:

The actual MBTA map (pdf).

## Sources

The tcsh file that downloads the relevant quadrants from Google Maps (the URL format for the quadrants has changed since 2005 – yes, 2005! – but you get the idea...)

The text file with coordinates of each station.

The translated TeX file.

# Disappearing Messages

(Idea originally conceived in 2009)

I’m fascinated by color. When I was younger I dreamt of discovering a color that nobody has ever seen before. And since most computer languages give you easy ways to manipulate graphics, I played with color on a computer.

One day I saw an interesting effect on some certificate I received. When I photocopied it in black and white, a word appeared in the photocopy ("COPY") that wasn’t visible in the original. This "security measure" took advantage of the photocopier’s inability to faithfully replicate the document (the word COPY was actually visible in the original but it was difficult to see because it consisted of a myriad of tiny dots). I wondered whether it would be possible to hide messages in documents even if the copier were to produce faithful facsimiles, but converted color to black & white images.

Introducing Disappearing Messages. If you're interested in the theory behind this effect, see this post and this post.

In this first experiment, text is visible in a color image, but when you render the image in black & white, the text will disappear.

Text to make disappear:

In the second experiment, text is only visible once you render the image in black & white. I've added a "distraction" text that you will see in the color rendering. (On your computer screen, you may still see both strings because of your browser's image color correction or color variability of your LCD screen. But if you print the image out in color, you will only see the "distraction" text.)

Text to make disappear:
Distraction text:

# A Continuous Party I Once Went To

(Part I – written in 2009)

It was July.  July 3rd, to be precise.  I remember the date because one doesn't arbitrarily show up in Boston for no reason and then forgets the minutest of details.  It's almost as if our brains, confused like hell, suddenly become more alert: such an unusual turn of events must mean something, and you know how our brains are just massive pattern matching devices where things that we do every day don't even enter our prefrontal cortex and things that don't make sense get escalated in panic; this is probably why we remember oddities.

Encouraged by an unlikely success at work; guilty for taking the better part of your friends' evening on July 3rd which was not a holiday; owing to a deity who somehow always intervenes at the right time but fails to give you an explanation you are really looking for but know that you will never get; or simply unwilling to go back to my apartment, I decided to drop my friend off in Boston.  Perhaps it was the irony of this statement that pushed me over the line. (I should have gone just a tad further and gone to Europe... maybe next time.) Anyway, I'll move on because I haven't even gotten to the interesting part; who cares why I went to Boston. Now I'm at the front door of this fraternity house in Boston.

The best thing about writing (and the thing that doesn't get much recognition) is the editing. Not the process of editing your writing, but the process of translating the spacetime into paper. The transition from a decision to go to the front door is so seamless that you probably didn't stop to think about what could have happened in the three hours prior to this (okay, two and a half). Though actually, nothing happened and hence the cut.  On reflection, maybe the lack of recognition is the best kind of recognition.  To make making nothing out of something look like nothing.

The sequence of images, sounds and thoughts that memory now presents to me is, how to put it, fluid.  It's non-linear, yes, but also selectively fuzzy and, most curiously, nondeterministic.  There is no single story.  With every thought the story changes slightly; the further I reach the more of one thing I reveal and of another I lose.  I can't be certain that everything is right (I'm quite sure some memories are imputed but does it matter since it's fiction anyway) but it feels familiar so I don't question it.  Some details are deemed more important than others.  I call this process "the third mode of storytelling", to differentiate it from the traditional way of recounting events and imagery (a kind of deliberate construction aimed at keeping the listener engaged) and from the way our brain constructs stories in dreams (there is I bet some mechanism that prevents our brains from confusing dreams with reality because the dreams always seem a little "off"--at least to me.  That seems like an evolutionary thing).

There is a party happening at the frat house.  The music is muted because--somewhat surprisingly, as, after all, it's the middle of summer--the door is closed.  I'm sure I can make myself remember what color the front door was, but I don't feel like it. Red? No, not red. There may have been greek letters painted on the door but kind of shoddily and I feel it's a reluctant must-have; just like the premium we pay on destroyed jeans (will future generations look at this anomaly in fashion with the same disdain we look at the '80s?).  I wish I could say something insightful about the smell in the air but, quite frankly, I only remember the visuals at this point and maybe that's the way it's supposed to be.  I don't knock, even though the thought of just barging in makes me uncomfortable.  I end up kind of awkwardly peering through the door just barely ajar only to, sadly, see nothing.  A few seconds pass, and I enter.

(Part II – Written in 2012)

The house has five stories (I always preferred the spelling "storeys", so much less simplistic). I enter at story 0 (which is not the bottom-most; I am European and an ANSI programmer and there was a basement level). There is music and a (matching? or am I imagining it now?) prevalent color, a warm yellow. The music blends with the color. It has beats but doesn't feel loud; good choice of genre for entrance music.

Story one has different music and a different color scheme. But what truly surprises me, what truly makes me pause, is the transition between the sets and thus the ambience of story 0 and story one (and, as I will later discover, all the floor transitions). The change is smooth and gradual (or is smooth and gradual really the same thing? What would gradual but not smooth look like?) and even though the two stories have nothing in common, walking upstairs doesn't generate an awkward combination of audiovisuals. The yellow turns into a dark brown; the beats disappear and turn gentle, indie-ish. I am at a party, that much I know, but as I transition between floors I realize I'm actually at a party that is a superposition of all these individual parties.[1]

Each floor creates its own atmosphere. Each floor captivates. I sit in a couch on floor II (which, by the way, is reddish and Reggae) and all the other floors--the rest of the world, for that matter--disappear. I could be on floor II forever. In fact, I forget I am on floor II. But there is floor xxx, which incidentally is also the roof, and I really want to figure out the sound and the color, if any, but by now I know that floor xxx won't disappoint.

And it doesn't. It's hip hop, the good kind not the mainstream shit. It's dark blue and it's dark outside and it's a good combination. Fresh summer air makes for a good finale.

But then I'm realizing what you probably remember, if you were reading carefully, and are jumping to answer, so go ahead and tell us! Yes, the basement level! What experience will the basement level provide? Can I handle all these transitions to find out? Of course I can! I must!

It's black. And it's electronica. It's a good floor to end this 180-mile night.

–––

1. I didn't know it at the time, but I would experience this again two years later in New Orleans, during JazzFest, the same effect but of a much larger scale: as I walk from one stage to another, the first genre becomes less distinct, then acquires a chaotic sort of richness, and finally fades to give way to the second genre. Takes about five minutes, which is prolonged, but which makes it kind of mysterious.

(This post was originally published on October 11, 2011)

I recently read Sum  and instinctively remarked to my friends that it's probably fairly easy to come up with a large number of different afterlives, some better some worse.  Well, I was called out on it.  So here's my pass.

• We are actually immortal.  When a near-death event occurs, the universe splits in two -- you continue in one branch, alive.  To everyone in the other, you are dead.  That's why you see others die in your universe.  The rules of the universe are constructed in such a way that it never appears as if people lived forever (that would raise some eyebrows!).  Instead, as you get older, people around you also get older, but by the time you're 90, you don't notice the strangeness.
• When you die, time simply stops.  You find yourself being able to control it entirely; you can rewind to your favorite life moment, and play it over and over again.  Since everything already happened, unfortunately you can't change your past.  You're confined to forever be a perfect spectator
• When you die, you move into Nothingness.  It's precisely what you can imagine it is -- a bunch of white and nothing else.  You don't exist physically, but you can perceive the whiteness.  It's a particularly boring existence, because you can reminisce and think of new things, but you can't make anything happen.  After years of such confinement everyone wishes they could move on, or die, or something -- ANYTHING -- but they can't
• When you die, your consciousness merges with that of other people who died.  It's hard to explain exactly what it feels like, because while we're alive we never feel that, but I can explain a few benefits.  (a) You can communicate with people instantaneously, (b) You feel their presence which is similar to physically being near them, (c) You share your feelings and thoughts more precisely than you ever could.  I can also explain a few drawbacks.  (a) You communicate with people instantaneously, whether or not you want to, (b) You feel their presence all the time. (c) You always share your feelings and thoughts
• Life is actually already an afterlife, a very special one.  It's Purgatory -- a test of whether you can become a better person so you can go to Heaven.  You invariably find out that you have failed
• It turns out that while nobody ever came back from an afterlife, we all know what it feels like, because our scientists have been able to digitally simulate "life" and let you experience it, and thus let you experience "moving on" from the digital life back to the real one.  It's believed that the actual afterlife feels the same way
• The afterlife is a shadow of your life.  You've lost the recollection of your death, so you relive moments of your life.  But something isn't quite right -- you get this strange feeling that you may sometimes get when dreaming, maybe thinking that it's a different kind of reality, a work of fiction.  However, the feeling never goes away
• As you lose your consciousness dying, time slows down to a crawl since with your life your perception of time dies.  Your consciousness can perceive the time slowing down, and eventually time stops and your consciousness becomes stuck in one moment in time, being able to perceive but with no sense of cause and effect, or sequencing (since that would require a notion of time).  While it sounds depressing, it's actually a wonderful feeling, since once memory is gone, all is life is pure consciousness.  And it's wonderful
• After you die, you relive the entire universe's existence, synesthesized in your brain to make the early events make sense to you.  At first, all you can hear is a strange buzzing.  Then flashes of lightning appear.  You watch the first particles form, chatty, confused, clinging to others fearing aloneness.  You watch planets form in a symphony of.  You witness stars die in spectacular dramas surpassing anything you saw when you were alive (by then, of course, you don't remember your life anymore).  By the time you witness your own birth, you have such wonderful perspective on everything around you that your birth has both a mystical significance and no significance at all
• When you die, you get in a time loop.  Usually it's about 10 seconds leading up to your death.  You don't remember that you're in a time loop, of course, so you happily relive your death, gruesome though it may be, over and over again
• We all die young.  When we die, we wake up in an afterlife, as an old, sick man who can never die.  The afterlife rules have allowed every resident of the afterlife one journey -- but only one -- to live another life in a world far away, as a young, healthy person.  Now that your trip is complete, you can only reminisce of good, young times
• There is a constant number of souls in the universe.  This means that when you die, you respawn as something else -- unlikely a human or even anything on Earth.  You may think that the number of conscious creates has been increasing on Earth, but the Universe is so vast, and so many quintillions of conscious creatures die in planetary implosions every minute, that the balance is kept pretty well.  You may have to wait up to twenty seconds after you die, but don't worry, time passes by quickly
• Everyone leads two lives.  In your first life, you are you.  In your second life, you are simultaneously every other person except for you.  In your second life, you get a perfect notion of what others think about you, but you do miss your own self a little bit.  Particularly, when everyone around you thinks something that you know is simply not true.  You are so misunderstood
• When you die, you realize that your life was a computer simulation, just like in the Matrix.  It turns out that in the actual life, technology solves every problem, there is no disease, famine, but there is also no emotion.  Is so incredibly boring that people built life simulations that they periodically subject themselves to, choosing not to know that they live in a fake world for the duration of their simulated lives
• In an afterlife, you can relive your life, but you can change a few crucial moments. To your surprise (and despite your hard efforts), your life always ends up being the sam
• The afterlife is spent waiting in line.  Eventually you forget why you're standing, or what you were doing before
• This life is our first life.  Each subsequent life is recycled from your prior life.  So each subsequent life is a little worse, a little less stable.  The scenes are the same, but your accomplishments are lesser.  Still, you live each life happier than any previous life, embracing it, knowing that the life after will be even worse
• There are several tiers of afterlife.  The High tier is wonderful.  The afterlife is warm and sunny, you hang out with your friends, drink a lot but never get a hangover.  The Middle tier is so-so.  It's cloudy all the time, you feel a little bit miserable most of the time.  The Low tier is shitty, it rains all the time, you have no friends, no money, and poor health.  Which tier you go into depends solely on your SAT score (or an equivalent, computed with an incredibly complicated formula from your life's achievements, if never took the SATs)
• After you die, if you weren't a good person, you are given one more chance.  You are brought back to Earth with an explicit mission.  At some time in your thirties, you will need to save a life of someone who dies tragically.  If you fail, you are gone for good.  As you grow older in your last-chance-life, you muse over the poor soul who failed to save you
• Some time ago, scientists proved what happens when we die.  It's nothing spectacular; describing it would be a waste of ink.  It's just good enough for people to look forward to, but not too good for people to start committing suicide.  Unsurprisingly, while the religious leaders accepted the undeniable proof, they still insist on parallels between the proven afterlife and whatever their religions promise.  Life goes on the same way as it was before we knew what the afterlife was
• In an afterlife, you retain most of your memories of your previous life.  Sadly, nobody believes you.  You try to prove it to people by describing events from your previous life, but they say you just read it in history books.  You try recalling facts that only you know about, but you don't quite remember all the details; you often get them wrong and so people just think you're crazy.  You're likely to spend the rest of your life in a mental institution, together with people who remember not one, but a hundred afterlives.  All the memories blend to them so even to you, what they say is just one unrecognizable jumble
• The afterlife features actual Greek gods.  The first thing you find out is that they exist -- the whole mythology.  The second thing you find out is that all the gods got tired of humans and stopped messing with their lives.  They had other, less petty, things to deal with, such as their own love triangles, betrayals, and murders
• You become the representative of the people you left behind.  You have to defend them in front of God who is angry with mankind and wants to wipe the entire human race out with some germ or a meteorite
• When you die, you just float out there above the universe.  You watch the universe die and restart itself.  It turns out that the probability of life in the Universe is astonishingly low, about 1e-159.  You patiently wait until you see something familiar, something biological, something you simply took for granted.  You could give up your immortality just for a glimpse of even the most despicable human behavior, even the most boring gesture, anything at all.  Watching a bacterium divide would make you ecstatic.  Instead, you traverse universe after universe, in search of something that is less likely to happen than a Universe filled with gold
• You are respawned as a molecule, an electron with consciousness.  You perceive everything around you, and can affect the environment you're in.  Unfortunately, your signals are too weak to be accurately detected by most instruments and so scientists who study you and your fellow Afterlifers puzzle over seemingly random effects you cause.  They even gave the name to a whole branch of physics that studies these phenomena. They call it "Quantum Mechanics"
• When you die, you find yourself in a hallway with an infinite number of doors.  You can't open any of the doors, but each door has a note on it.  The notes say you're really close, the further you go the closer you are.  And so you wander in an infinite hallway, passing closed doors, hoping for an end that never happens
• When you die, your consciousness scatters throughout the environment that surrounded you.  Consciousness, it turns out, if just the network of particles that makes up your body, the more connected the cells and particles are, the stronger your consciousness.  After your mind begins to decay, you still exist, but are much more spread out
• When you die, you meet your family and friends who died before you.  They have all been watching over you.  They have seen everything; they know your every secret.  They judge you.  You are first confused, then angry, then resigned over the unfairness: you never saw their secrets.  So, even though at first you resolve not to sink to that level, you begin judging those that come after you just as those who came before you do to you
• The Afterlife is actually pretty simply.  You are reincarnated, with the memory of your prior life, but not just after you die.  You come back to Earth exactly 100,000 years later.  As you walk around Earth, you meet other people who were respawned and mingle with the contemporary humans.  You compare your notes on the world you left behind, and, to nobody's surprise, pretty much recreate what you were familiar with.  You realize that when you were first alive, there were other humans roaming the Earth alongside you, who had died around 100,000 BC.  Unfortunately, their consciousness had not developed sufficiently well for them to be able to tell you what those memories they are having are
• When you die, you become a particle of light.  You see what it is like to travel with the speed of light.  It's actually a humongous disco show, a blur.  You are born in one of the suns, and four weeks later you enjoy taking a walk to Earth.  You may bounce off the atmosphere and spiral in a particular direction, maybe encountering another planet, maybe getting sucked into a black hole (which is, suffice it to say, really boring), maybe traveling for the rest of the universe's existence, until you slow down and head back crashing with all other particles
• When you die, you become the creator of new souls.  Everyone who's ever died gives up a bit of their soul to create a new one for a newborn baby.  You can decide what part of your soul you give up.  Maybe it's a dark part, and if enough people choose to do that, the man is a conflicted, evil man
• When you die, you find yourself back on Earth, exactly the same as when you left.  However, the only thing missing is other people.  The Afterlife is completely devoid of other people or any other beings with a soul
• When you die, you become a bit in a massive computer system.  You work hard, getting flipped, sometimes many hundred times a second, sometimes not at all for months.  You kind of like this afterlife.  The demand for bits is always growing, and the system upgrades itself, so you'll never get bored.  If you're lucky, you may be a part of a computer algorithm that uses you to draw an entire image, and so you get a glimpse of what the user may be looking at.  You can chat with other bits but not too much -- the computer hardware is built not to tolerate interference between bits.  You are amazed at the complexity of software being built, and at the wonders that the system's users are given access to.  In fact, you learn quite a lot about the users simply by getting flipped around
• In an afterlife, everyone ends up making their immoral life look just like what they are used to -- their regular life.  At first, you want to start anew, maybe pick up a hobby.  But eventually you give up, too.  It's just too much effort
• In an afterlife, you are granted an unlimited number of wishes, but whenever you make one, you forget something from your past.  You ask for money and other personal goods.  Quickly you realize the futility of such selfish wishes and turn to your family, ensuring they are healthy, have good jobs and are happy.  If they get into an accident, you wish them to get better.  You also start wishing good things upon mankind.  Unfortunately, by the time your loved ones arrive to the afterworld, you've forgotten them
• When you die, you find a book that contains the precise descriptions of millions of lives that you have to live through, sequentially.  When you are respawned, you forget about the book's existence, so you don't end up valuing the most precious lives
• The rules of the afterlife allow you to go back on earth, as an invisible observer, as a form of tourism.  You see all the other Afterlifers, though.  You wish you didn't, because this means that it's way too crowded around the big events, like Jesus's birth or JFK's assassination.  You keep going back and back again, but you simply position yourself anywhere near where the action is.  You much prefer random times in the past where you may run into one, maybe two other people
• The afterlife is a Vermont village
• There is a curious connection between the afterlife and the earthly life.  From the afterlife, you can affect things in the earthly life, but very subtly.  You try to leave messages, by carefully arranging grains of sand (you can't really lift any heavier objects that grains of sand), or letting the wind blow in the right way into a window during rain to reveal a hidden message.  To your great disappointment, nobody can see the messages.  You keep trying, though
• You get to choose your afterlife from a list of several thousand.  Naturally, some afterlives are more popular than others, so there is a fairly convoluted application process.  Some afterlives are incredibly selective, allowing in only the more noble of people.  Others require internships in other afterlives first.  Others make you take a test.  It's very competitive out there
• Once you die, an extra-dimensional being pulls you from the aether, demanding to know what life is like.  It turns out that crossing all dimensions, there is an entity that has always been and will always be, is omnipresent, and all-knowing.  However, it can't create anything, let alone life
• Once you die and gain some perspective, you realize that the passage of time is not nearly as much of a problem as the fact that the space shrinks.  It gets more and more crowded, which is annoying given that all these new souls keep arriving but the real estate gets more and more pricey
• Just after you die, you realize you have been incredibly close to discovering what afterlife was while you were alive.  Your intuition, bolstered by irrefutable proof, was right.  If only you had just a few hours of life left.  But then you realize that some complex law of the universe, a kind of exclusion principle, prevented you from revealing the facts of the afterlife, and resulted in your death
• When you die, you are randomly assigned a color, blue or green.  There are two identical afterlives, and you end up in one of the two based on your assigned color.  You never mix with the people of the other afterlife, and because you were never given the context, you (and everyone in each afterlife) is convinced that they are in hell and the other afterlife is heaven
• The afterlife is run by a corporation.  It strives to maximize profits, which is strange because it's unclear what good money is for in an afterlife.  Because it's pretty much a monopoly, you don't feel like you're treated well at all.  In fact, you feel you're only a statistic that the corporation uses to convince more investors to contribute, a kind of "look how many people we can efficiently handle" and "there will always be an increasing demand for our services"
• You get quizzed on your life.  If you fail, you repeat your life.  As you are about to take the test, you realize that you really don't want to go back to your miserable, aching life.  In fact, nobody wants to do that.  But the quiz is very hard.  Some even think it's rigged, to make it impossible to pass.  It's almost as if there was no afterlife but nobody had the guts to tell you
• When you die, you find yourself sitting in front of a TV screen, watching another person's life.  After that person dies, they end up watching someone but still watch them so now you watch two people -- the person watching the TV and the person being watched.  This repeats forever, which is quote fun, because you keep watching new lives.  You begin to wonder who is watching you.  You try sending them signals by zooming in an out in a kind of cipher, but you realize that there is no way for your watcher to ever communicate to you anything about themselves.  You decide to send signals periodically hoping that someone in the chain above you can communicate back to you, because you feel lonely.  Then, one day, when the person being watched hundreds of thousands lives away dies, and you decide to zoom onto the person they start watching in their afterlife, you realize that the person is you
• When you die, you stay in the same physical universe you were in.  You are finally truly happy.  But one thing gnaws at you.  Entropy keeps increasing.  One day this universe will die.  And then what?  What will happen to your lifetime?  Will you cease to exist?  Or will you more to another afterlife?  You can't imagine being just as blissful there
• It turns out that anyone can control the afterlife here, from Earth.  Politicians have seized this opportunity to test alternate histories to determine which of their actions will have the more desirable result.  They shape the afterlife to look exactly like the one on Earth including the decision they are about to make, and then let it play out and see what would happen tens of years later (time is just one of the things that can be controlled).  Recently a faction began advocating for the rights of the afterlifers.  After all, we're all going to be one of them at some point, and we wouldn't appreciate being guinea pigs being experimented on with stupid political decisions.  For now, however, people prefer to live their earthly life better than have a better afterlife
• You wake up in front of a book you are writing.  It turns out that every one of us has been dreamt up by an immortal writer, trying to capture the essence of mortality
• Due to strangeness of physics, the afterlife is at a precise location in space, about eighty light years away from Earth.  You spend your after-lifetime conflicted whether you want mankind to ever discover this location or not.  There are many people here who think they should start communicating out to the human race some facts that are known here, such as the location of buried treasures or solutions to mysteries.  Ultimately, you decide that it will do more bad than good and sit quietly, hoping that you are never discovered, trying to minimize your celestial footprint so that scientists on Earth with their ever-improving instruments can never detect you
• The afterlife is an infinite escalator.  Most people just stand on it, but you can walk up and down if you'd like.  You pass people every so often (either by walking up or down or by them walking up or down) but in the long run everyone is just going up at a fairly uniform rate.  You just hope you don't meet that really annoying guy who may want to spend the rest of his life here talking to you
• Your life has been a simulation.  It's a pretty low-fidelity simulation, actually.  You could compare it to the videogames of the 70s.  Imagine what the afterlife life must be like!  (Well, nobody can)
• In the future, humans discover what causes people to die and become capable of reversing the process, thus making mankind immortal.  To deal with population growth, however, everyone on Earth decides to create a synthetic afterlife, a place where all people are "sent" when they "die".  Over time, we decide that it's better if the afterlifers don't mix with the humans, and, in fact, if nobody really knows what an afterlife is.  That uncertainty creates a more stable population (and makes possible some large organizations that claim without any scientific evidence that the afterlife is exactly the way they envisioned it)
• In the afterlife, we are given a chance to carefully construct a world for our new life.  One thing we're not told, though, is that as soon as we start our new life in our beautifully designed world, we lose all memory of having created it in the first place.  Most times, then, we end up not taking advantage of the wonders left in the world by our immortal selves
• In the afterlife, we awake as librarians.  We have been dreaming a life described by a book we just finished reading.  It turns out that the afterlife is all about classification, and the only way to classify a book is to live out a life and see what the protagonist was really feeling
• There is no God.  God liked His creation so much that he decided to start living as a mortal on Earth, lifetime after lifetime.  It's addictive, being mortal is.  But we who die and go to the afterlife, don't know that.  We pass by one opportunity to go back to Earth after another in fear that God comes back when we're not there and we'll miss out
• It turns out people can, and in fact do, come back from the afterlife.  All they remember is that it was worse than the earthly life
• After you die, you are put in an interrogation room and asked one question.  This is a simple yes or no question.  It is, "Do you believe in God?".  Answering correctly grants you an afterlife; answering incorrectly makes you perish forever.  Nobody has answered this question correctly yet
• God is an accidental God who just happened to mix some life in a test tube.  He doesn't understand the significance of it all, and in fact, he doesn't care about it.  He just experiments with matter to get cool visual effects
• God is himself looking for an afterlife.  He sees all these people arrive in his world, claiming it to be their afterlife.  He doesn't understand why that can be; after all, his world is pretty normal.  It's as if some humanlike forms started appearing on Earth claiming it was their afterlife.  That makes him very uncomfortable about his own afterlife
• You are given a choice between the red pill and the blue pill, just like in the Matrix, but for the life of it you can't remember which one was which in the movie.  IF you take the wrong pill, you live the entire afterlife in the Matrix.  But regardless of which pill you took, you keep doubting whether you are in the Matrix or not.  There is simply no way to find out
• Everything is familiar in the afterlife.  It's as if you've lived it before.  That's because you have: the afterlife is an infinite permutation of the moments you've lived in your mortal life
• After you die, you find yourself in a lavatory of a plane, on an infinitely long flight.  The flight is so boring (and it's unclear whether it actually leads to anywhere fun), but the lavatory has a cool feature in that it allows you to relive and entire lifetime.  You just wish there were more lavatories on the plane; whenever someone comes in, they stay there until their entire earthly life is over
• After you die, you can pick the time period you get respawned in.  The overwhelming majority of people pick the future, for example the year 2150, only to discover to their shock that they are the only person alive.  It turns out that there was a biological disaster that wiped human life from Earth in 2012
• The afterlife is precisely what you want it to be just before you die.  Every effort is made to accommodate everyone's wish, and ideally everyone would just be happy that way, but of course there are many incompatible wishes, so we had to build multiple different afterlives, based on who people don't want to hang out with.  The biggest haters get the smallest afterlives.  Over time, they no longer remember why they hated all these other people, and just feel lonely
• As you die, your consciousness fades slowly, and your perception of time changes.  You feel weaker consciousness-wise, like moving from a dream to a deeper dream.  First you lose the conception of death, then of yourself.  Finally, you lose the conception of anything
• There is no such thing as an afterlife.  Instead, there is a beforelife.  The day you are born, you have already gone through a long lifetime of comfort and serenity.  Some of us remember it, and are thus deeply saddened, knowing that they will never achieve what they had
• Consciousness is not a complex process in the brain, it's a particular arrangement of particles, a fingerprint.  You share this fingerprint with other beings, but you only perceive the strongest manifestation of the consciousness as you, and your human instance overpowers all others.  When you die, the next strongest instance could be in some insect, or a flower, or a bacterium. This pattern lives overwhelmingly in your brain, in a very concentrated fashion, which is why you think of yourself as having your body.  When you die, the consciousness It flips back to a less strong one, like a flower or a bee
• Afterlife is one example where Communism worked out.  It's all that Lenin could have wished for.  However, it still sucks.  You’re fed but never taste, you find yourself unable to form an opinion because nobody is interested in it, every day is the same as the day before
• In an afterlife, everyone has a pass at creating their own idea of a life, and then everyone lives that life out.  There are no rules, no limitations, anything is possible.  However, you’re approximately #100-billionth in line so you have to live through some pretty terrible designs first
• In an afterlife, you are paired with an alternative version of you for whom everything in life went better.  It's pretty depressing.  But then someone whole life went worse than yours was paired with you.  They look up to you the same way you look up to your role model.  That makes you feel better

# The Theories of Time Travel

(Originally published on October 22, 2010)

Let’s assume that what we all secretly hope for is true: that backwards time travel is possible (with a fast enough rocket you can travel forward in time already, thanks to Einstein). It’s unclear what such time travel would look like — there are many different theories and, consequently, interesting implications on the Universe, causality (why hasn't anyone visited us from the future?) the existence of paradoxes, and the existence and the nature of time loops. Some include interesting design constraints: my favorite is the theory of time travel put forth in Primer.

Note that to help myself think through this, I have a human being travel in time; this may lead to inaccuracies and further questions — in most of the cases below, we can probably replace me with a photon, or even a quark, and get more precise results (“memory” becomes “momentum” or “spin”, etc.). But it’s more fun to think about people traveling in time.

### Possibility one: there is only one version of the Universe

• If the links between causes and effects are not maintained, we have a consistent (paradox-free) time travel: moving backwards in time rewrites history and the previous version is lost. The I that travels back in time (call it I1) is not the same as the I that I1 meets in the past (I2). Whether I2 enters the time machine or not is irrelevant to I1. If I1 kills I2′s grandfather, I2 will not be born but I1 will not be affected in any way. It’s a very safe theory of time travel.
• If the links between cause and effect are maintained (but their temporal relationship isn’t, necessarily), the Universe has to decide how to handle duplicates of matter/energy: it may choose to allow them, or not, or have an opinion somewhere in between.
• If duplicates are allowed, I1 is identical to I2 but they are allowed to co-exist. If I1 prevents I2 from entering the time machine, I1 will cease to exist. What if I1 kill’s I2′s grandfather (who is also I1′s grandfather)?
• It’s possible that I1 will simply not be able to do this — this is the theory where the Universe maintains its consistency (by making it prohibitively expensive — either by requiring you to put a lot of energy into your action or outright generating laws that locally forbid you to perform it), somewhat akin to what the writers of Lost did in the show. This energy-effect constrained time travel — the Universe not letting me kill my grandfather — is interesting. In order to maintain its consistency, the Universe would need to propagate all actions forward (“play them out”). If there is a sequence of actions that cause an inconsistency, the energy required to continue along this sequence would increase, proportionally to the probability of an inconsistency. It would be like an invisible magnetic field that steers actions in a particular direction. This could be implemented by a biased averaging out of quantum effects: let’s take light for example. We know that according to quantum theory, the movement of photons from A to B is realized through an infinite number of different paths which average out to a straight line. However, if the probabilities of the paths are different (due to the fact that some paths may cause an inconsistency in the future), the paths could actually average to something that’s not a straight line. To us it would seem that light travels in curved paths (without the presence of any “real” field, such a gravitational one)! Of course, these probabilities change gradually so no obviously apparent deviations from the norm would occur at first. For example, if I’m intending to kill my grandfather, the Universe will start steering me away from my intention through a small sequence of very likely events. If I persist in my intentions, the events increase in magnitude, but it’s possible (because there are just so many possible events that can influence me) that I will never realize my intention without even seeing anything strange with the Universe.
• Otherwise, we have a phenomenon known as the Grandfather Paradox. I1 may create an unstable point in the spacetime: I1 (and thus I2, and the grandfather) will both exist and not exist at the same time, in a kind of macro-Shrödinger effect. What’s worse, anything that either was caused by I2 or the grandfather or would have been caused by I1 will also both exist and not exist. It’s unclear what effect this will have on the rest of the Universe — as these effects ripple through time, they expand their scope (the events that the grandfather caused themselves caused other events) but decrease their magnitude (think of it as a sound wave propagating through space, maybe bouncing off objects).
• It’s possible that over time, as soon as they become small enough to be captured by quantum uncertainty, they stabilize so the ripple has a finite size (I can’t visualize what the ripple would actually look like, maybe a really fast-flashing grandfather).
• Or the Universe could cease to exist.
• If duplicates of matter/energy are not allowed, I1 would need to replace I2 (for this to work, the Universe would somehow need to have a unique identifier for everything in it). It’s difficult to think about replacing something complex like a human being because he or she is made of many building blocks, each having a different identifier, so let’s simplify and think of something that consists of a single block (say, a photon). The photon would replace its version from the past. Does this photon have “memory”, that is, its future state?
• If so, the photon will likely change its course (behave differently than I1 did). This may mean that I2 may never end up traveling in time, but that’s fine because there is only version of it. This is equivalent to the theory of rewritten history.
• If not, I1 simply merges into I2 — I2 enters a time loop which it will never be able to leave. It’s not aware of that, however, so to I1, the time travel ends its consciousness.
• If somehow we can maintain this option at a macro scale, it’s possible that an individual may travel back in time and maintain his or her memory, provided that the interval of time travel is small (for example, if I1 travels back to before I2 was born, I1–an individual–would have to replace a bunch of particles which aren’t even part of a human being. That will very likely result either in the destruction of I2–I2 will not be possible given the new state that all of its particles will have assumed before they created it–or in the destruction of I1–the “memory” that each particle has will be insignificant and so I1′s consciousness will end as soon as he travels in time)
• Another way not to allow duplicates would be for I1 and I2 to “swap” places: as soon as I1 travels backwards in time, it takes I2′s place and I2 takes I1′s place in the future. When I1 gets to the time when it first traveled in time, he ceases to exist. There is no paradox because time travel transfers both I1 and I2. It doesn’t matter whether I1 actually enters the time machine the second time around or not, because his existence ceases past that point anyway.
• Finally, the Universe may choose some option in between, for example, I1 and I2 will be entangled in a way that doesn’t increase entropy. This may look like a kind of constrained time travel, where paradoxes are not possible because they are prevented by the entanglement of I1 and I2 (in other words, I1′s and I2′s actions will either make both of them survive the interval of their co-existence, or make them both self-destruct. At the event of time travel, I2 goes back and I1 is the only entity remaining. ** This brings me to an interesting idea: what if time travel and quantum theory are actually one and the same? What if the time interval where I1 exists in the past (and influences outcomes) is equivalent to the cat being both alive and dead: it cannot be inspected, and nothing can be said about what happened or what any of the outcome that I1 could have influenced was. The instant at which I1 entered the time machine would then correspond to the box being open — we find out what all those outcomes were.

### Possibility two: there are many versions of the Universe

This is similar to the first case (rewriting history) but if the Universe bifurcates with every time travel, an awful lot of energy is needed to do time travel. Alternatively, the Universe may already exist in its virtually infinite forms, each form corresponding to a different possible unfolding of an event. We know from Newton that at a high level the world seems deterministic, but at a quantum level it’s not — this randomness I see as a basis for the different unfolding of the events (hence, once and for all answering the problem of free will: there is no free will, but there is also no determinism — what we perceive as “choosing” is just a particular folding up of all the quantum uncertainties). So every time we put a cat in a box, there are Universes in which the cat is dead and Universes in which it’s alive. We know which path we’re on as soon as we open the box. Time travel would then simply be an opportunity to follow a different path.

There is one problem with many of the sub-theories above, and that is a problem of the sudden injection of matter/energy: if I appeared from the future, the mass/energy of the universe wouldn’t be conserved (I could build a kind of automated time travel machine that continuously adds energy or mass to the universe, or–even better–reduce the entropy of the entire universe). So my arrival needs to be coupled with disappearance of energy or mass. Or maybe some other matter/energy is transferred into the future (where the travel originated). Possibly an arrangement such as one in Primer is needed where travel is only possible to a limited point in time, where all the prep work has been done, for example enough energy has been set aside to be “displaced” by the newly arriving energy. It may also be that the time travel portal has a standby energy consumption — it consumes energy at some rate, like a leaking pipe, all the time — this would allow energy of at most that rate to be transferred from the future.

Another way to solve the sudden injection problem is to borrow me for the duration of the time travel episode from the time chronologically after the event of time travel. That is, if in the year 2010 I go back to the year 2005, my extra existence for five years between 2005 and 2010 will be borrowed from what would have been my existence between 2010 and 2015. In other words, as soon as I reach the year 2010 the second time around, I jump to the year 2015. This is a kind of quantum entanglement, but not of I1 and I2, but rather of I1 and the future version of I1.