When James Buchanan was sworn into office on March 4, 1857, John Wood made history by making the first known photograph of a US Presidential inauguration. 

Wood was hired by Montgomery C. Meigs, an engineer managing the expansion of the US Capitol which added wings for the Senate and House. According to Robert O'Harrow's The Quartermaster, Meigs was an early days photography enthusiast. As prints became easier and more affordable to produce, he saw the value in using photography to make copies of architectural plans and hired Wood.

For the inaugural photo, Meigs constructed a small stage so that Wood could capture the scene. The crowd of more than 20,000 mostly stood on a platform Meigs had built to hide construction debris. His journal mentions that Wood was able to make the inauguration exposure in 4 seconds, as he had been experimenting with a 'photography process of great speed,' referring to the wet collodion process that was being widely adopted at the time. The image that resulted is an albumen print, resulting from a method of making prints that used a substance found in egg whites and table salt to bind photographic chemicals to paper. 

On Friday, xkcd #1190—Time—came to an end.

It was a huge project, but since it was all concealed within a single comic panel, I thought I’d end with this short post to explain what was going on. If you want to see the story yourself before I spoil anything, you can use one of the many excellent third-party Time explorers, like the Geekwagon viewer, or one of the others listed here.

When the comic first went up, it just showed two people sitting on a beach. Every half hour (and later every hour), a new version of the comic appeared, showing the figures in different positions. Eventually, the pair started building a sand castle.

There was a flurry of attention early on, as people caught on to the gimmick. Readers watched for a while, and then, when nothing seemed to be happening, many wandered away—perhaps confused, or perhaps satisfied that they’d found a nice easter-egg story about castles.

But Time kept going, and hints started appearing that there was more to the story than just sand castles. A few dedicated readers obsessively cataloged every detail, watching every frame for clues and every changing pixel for new information. The xkcd forum thread on Time grew terrifyingly fast, developing a subculture with its own vocabulary, songs, inside jokes, and even a religion or two.

And as Time unfolded, readers gradually figured out that it was a story, set far in the future, about one of the strangest phenomena in our world: The Mediterranean Sea sometimes evaporates, leaving dry land miles below the old sea level … and then fills back up in a single massive flood.

(A special thank you to Phil Plait for his advice on the far-future night sky sequence, and to Dan, Emad, and everyone else for your help on various details of the Time world.)

Time was a bigger project than I planned. All told, I drew 3,099 panels. I animated a starfield, pored over maps and research papers, talked with biologists and botanists, and created a plausible future language for readers to try to decode.

I wrote the whole story before I drew the first frame, and had almost a thousand panels already drawn before I posted the first one. But as the story progressed, the later panels took longer to draw than I expected, and Time began—ironically—eating more and more of my time. Frames that went up every hour were sometimes taking more than an hour to make, and I spent the final months doing practically nothing but drawing.

To the intrepid, clever, sometimes crazy readers who followed it the whole way through, watching every pixel change and catching every detail: Thank you. This was for you. It’s been quite a journey; I hope you enjoyed the ride as much as I did!

P.S. A lot of people have asked if I can sell some kind of Time print collection (or a series of 3,099 t-shirts, where you run to the bathroom and change into a new one every hour). I’m afraid I don’t have anything like that in the works right now. I just made this because I thought it would be neat, and now that it’s done, my only plan is to spend the next eleven thousand years catching up on sleep. If you liked the project, you’re always welcome to donate via PayPal (xkcd@xkcd.com) or buy something from the xkcd store. Thank you.

In trying to assess the the killing of Trayvon Martin by George Zimmerman, two seemingly conflicted truths emerge for me. The first is that is that based on the case presented by the state, and based on Florida law, George Zimmerman should not have been convicted of second degree murder or manslaughter. The second is the killing of Trayvon Martin is a profound injustice. In examining the first conclusion, I think it's important to take a very hard look at the qualifications allowed for aggressors by Florida's self-defense statute:

 Use of force by aggressor.--The justification described in the preceding sections of this chapter is not available to a person who: (1) Is attempting to commit, committing, or escaping after the commission of, a forcible felony; or

(2) Initially provokes the use of force against himself or herself, unless:

(a) Such force is so great that the person reasonably believes that he or she is in imminent danger of death or great bodily harm and that he or she has exhausted every reasonable means to escape such danger other than the use of force which is likely to cause death or great bodily harm to the assailant; or

(b) In good faith, the person withdraws from physical contact with the assailant and indicates clearly to the assailant that he or she desires to withdraw and terminate the use of force, but the assailant continues or resumes the use of force.

I don't think the import of this is being appreciated. Effectively, I can bait you into a fight and if I start losing I can can legally kill you, provided I "believe" myself to be subject to "great bodily harm." It is then the state's job to prove--beyond a reasonable doubt--that I either did not actually fear for my life, or my fear was unreasonable. In the case of George Zimmerman, even if the state proved that he baited an encounter (and I am not sure they did) they still must prove that he had no reasonable justification to fear for his life. You see very similar language in the actual instructions given to the jury:

In deciding whether George Zimmerman was justified in the use of deadly force, you must judge him by the circumstances by which he was surrounded at the time the force was used. The danger facing George Zimmerman need not have been actual; however, to justify the use of deadly force, the appearance of danger must have been so real that a reasonably cautious and prudent person under the same circumstances would have believed that the danger could be avoided only through the use of that force. Based upon appearances, George Zimmerman must have actually believed that the danger was real.

If George Zimmerman was not engaged in an unlawful activity and was attacked in any place where he had a right to be, he had no duty to retreat and had the right to stand his ground and meet force with force, including deadly force if he reasonably believed that it was necessary to do so to prevent death or great bodily harm to himself or another or to prevent the commission of a forcible felony.

There has been a lot of complaint that "stand your ground" has nothing to do with this case. That contention is contravened by the fact that it is cited in the instructions to the jury. Taken together, it is important to understand that it is not enough for the state to prove that George Zimmerman acted unwisely in following Martin. Under Florida law, George Zimmerman had no responsibility to--at any point--retreat. The state must prove that Zimmerman had no reasonable fear for his life. Moreover, it is not enough for the jury to find Zimmerman's story fishy. Again the jury instructions:

George Zimmerman has entered a plea of not guilty. This means you must presume or believe George Zimmerman is innocent. The presumption stays with George Zimmerman as to each material allegation in the Information through each stage of the trial unless it has been overcome by the evidence to the exclusion of and beyond a reasonable doubt. To overcome George Zimmerman's presumption of innocence, the State has the burden of proving the crime with which George Zimmerman is charged was committed and George Zimmerman is the person who committed the crime.

George Zimmerman is not required to present evidence or prove anything.

Whenever the words "reasonable doubt" are used you must consider the following: A reasonable doubt is not a mere possible doubt, a speculative, imaginary or forced doubt. Such a doubt must not influence you to return a verdict of not guilty if you have an abiding conviction of guilt. On the other hand if, after carefully considering, comparing and weighing all the evidence, there is not an abiding conviction of guilt, or, if having a conviction, it is one which is not stable but one which wavers and vacillates, then the charge is not proved beyond every reasonable doubt and you must find George Zimmerman not guilty because the doubt is reasonable.

It is to the evidence introduced in this trial, and to it alone, that you are to look for that proof.

A reasonable doubt as to the guilt of George Zimmerman may arise from the evidence, conflict in the evidence, or the lack of evidence.

If you have a reasonable doubt, you should find George Zimmerman not guilty. If you have no reasonable doubt, you should find George Zimmerman guilty.

This was the job given to the state of Florida. I have seen nothing within the actual case presented by the prosecution that would allow for a stable and unvacillating belief that George Zimmerman was guilty.

That conclusion should not offer you security or comfort. It should not leave you secure in the wisdom of our laws. On the contrary, it should greatly trouble you. But if you are simply focusing on what happened in the court-room, then you have been head-faked by history and bought into a idea of fairness which can not possibly exist.

The injustice inherent in the killing of Trayvon Martin by George Zimmerman was not authored by jury given a weak case. The jury's performance may be the least disturbing aspect of this entire affair. The injustice was authored by a country which has taken as its policy, for lionshare of its history, to erect a pariah class. The killing of Trayvon Martin by George Zimmerman is not an error in programming. It is the correct result of forces we set in motion years ago and have done very little to arrest.

One need only look the criminalization of Martin across the country. Perhaps you have been lucky enough to not receive the above "portrait" of Trayvon Martin and its accompanying tex. The portrait is actually of a 32-year old man. Perhaps your were lucky enough to not see the Trayvon Martin imagery used for target practice (by law enforcement, no less.) Perhaps you did not see the iPhone games. Or maybe you missed the theory presently being floated by Zimmerman's family that Martin was a gun-runner and drug-dealer in training, that texts and tweets he sent mark him as a criminal in waiting. Or the theory floated that the mere donning of a hoodie marks you a thug, leaving one wondering why this guy is a criminal and this was one is not.

We have spent much of this year outlining the ways in which American policy has placed black people outside of the law. We are now being told that after having pursued such policies for 200 years, after codifying violence in slavery, after a a people conceived in mass rape, after permitting the disenfranchisement of black people through violence, after Draft riots, after white-lines, white leagues, and red shirts, after terrorism, after standing aside for the better reduction of Rosewood and the improvement of Tulsa, after the coup d'etat in Wilmington, after Airport Homes and Cicero, after Ossian Sweet, after Arthur Lee McDuffie, after Anthony Baez, Amadou Diallo and Eleanor Bumpers, after Kathryn Johnston and the Danziger Bridge, that there are no ill effects, that we are pure, that we are just, that we are clean. Our sense of self is incredible. We believe ourselves to have inherited all of Jefferson's love of freedom, but none of his dependence on slavery.

You should not be troubled that George Zimmerman "got away" with the killing of Trayvon Martin, you should be troubled that you live in a country that ensures that Trayvon Martin will happen. Trayvon Martin is happening again in Florida. Right now:

In November, black youth Jordan Davis, a 17-year-old Jacksonville resident, was the only person murdered after Michael Dunn, 46, allegedly shot into the SUV Davis was inside several times after an argument about the volume of music playing.

According to Dunn's girlfriend, Rhonda Rouer, Dunn had three rum and cokes at a wedding reception. She felt secure enough for him to drive and thought that he was a good mood. On the drive back to the hotel they were residing at, they made a pit stop at the convenience store where the murder occurred. At the Gate Station, Rouer said Dunn told her that he hated "thug music." Rouer then went inside the store to make purchases and heard several gunshots while she was still within the building.

Upon returning and seeing Dunn put his gun back into the glove compartment, Rouer asked why he had shot at the car playing music and Dunn claimed that he feared for his life and that "they threatened to kill me." The couple drove back to their hotel, and claim they did not realize anyone had died until the story appeared on the news the next day.

After killing Jordan Davis, Michael Dunn ordered a pizza.

When you have society which takes at its founding the hatred and degradation of a people, when that society inscribes that degradation in its most hallowed document, and continues to inscribe hatred in its laws and policies, it is fantastic to believe that its citizens will derive no ill messaging.

It is painful to say this: Trayvon Martin is not a miscarriage of American justice, but American justice itself. This is not our system malfunctioning. It is our system working exactly as it should, given all of its programming. To expect our courts, our schools, our police to single-handedly correct for this, is to look at the final minute of the final quarter and wonder why we couldn't come back from twenty-four down.

To paraphrase a great man--We are what our record says we are. How can we sensibly expect different?

Just in time for the Fourth of July, Jeremiah Warren created an incredible relatively low-budget “bullet time” rig— with a 240 fps GoPro camera mounted to a ceiling fan —to photograph fireworks. He posted a full writeup showing how to build it on his web site.

The clever hack about using the GoPro on the ceiling fan is thanks to Mark Rober, who showed how to do it back in May, mostly with smaller-scale subjects.  But Jeremiah has taken the idea and run with it, adapting it for larger-scale photography.

And as you can see, the results are simply fantastic.You can find more videos and the full how-to on Jeremiah’s site.

I read with interest David Simon's recent blog post in which he responds to revelations that the NSA has been collecting the call records of all American mobile phone users.

David Simon, of course, created the Wire, a television series where institutions take on lives of their own and defy attempts by well-meaning people to reform them from within. So it came as a real shock to find Simon criticizing pundits who have objected to the extent of NSA surveillance, and accusing them of wilful ignorance about the nature of police work.

Mr. Simon pointed out that law enforcement agencies have been allowed to capture call records for decades, including in cases where the information harvested includes calls from people who are not under suspicion. In other words, there's nothing new going on to get worked up about.

Having labored as a police reporter in the days before the Patriot Act, I can assure all there has always been a stage before the wiretap, a preliminary process involving the capture, retention and analysis of raw data. It has been so for decades now in this country. The only thing new here, from a legal standpoint, is the scale on which the FBI and NSA are apparently attempting to cull anti-terrorism leads from that data. But the legal and moral principles? Same old stuff.

Seeing no difference in principle, only a difference in degree, in the NSA's surveillance program, Simon expresses annoyance with Americans who demand total protection from terrorism and then purport to be shocked when their government takes their requests seriously.

Mr. Simon cites the specific example of an investigation he covered as a police reporter in Baltimore in the 1980's. Criminals were using pay phones and pagers to evade detection, and tracking them down required indiscriminately recording numbers dialed from those pay phones, with the goal of sifting through the data later to find the pager numbers.

He argues that this kind of investigation, which targeted pay phones, was in some ways more invasive than the kind of tracking the NSA is accused of, since people expect to be anonymous when using a pay phone in a way that doesn't apply when they're calling from their own cell.

There is certainly a public expectation of privacy when you pick up a pay phone on the streets of Baltimore, is there not? And certainly, the detectives knew that many, many Baltimoreans were using those pay phones for legitimate telephonic communication. Yet, a city judge had no problem allowing them to place dialed-number recorders on as many pay phones as they felt the need to monitor, knowing that every single number dialed to or from those phones would be captured. So authorized, detectives gleaned the numbers of digital pagers and they began monitoring the incoming digitized numbers on those pagers — even though they had yet to learn to whom those pagers belonged. The judges were okay with that, too, and signed another order allowing the suspect pagers to be “cloned” by detectives, even though in some cases the suspect in possession of the pager was not yet positively identified.

I think Simon's fundamental argument, “same old stuff”, is mistaken in a number of important ways, and that some of this reflects our failure as technologists to communicate what modern surveillance can do.

First, there is the scope of the order. The Baltimore operation, and others like it, were limited to a specific criminal investigation. They were obtained under a warrant setting limits on what would be collected, and for how long.

The NSA program is universal and appears to be open-ended. Information is collected in aggregate. The program operates under the authority of secret court order, not a warrant. It is not clear whether the Administration even believes this type of surveillance requires a court order.

Second is the nature of the body carrying out the surveillance. In Simon's example, this was a municipal police force, overseen by a local court.

In our case, it's the NSA, a Federal agency whose job has traditionally been to collect foreign signals intelligence ①. The operation is overseen by a secret court system called FISC.

Third is the nature of the data being collected. When the Baltimore investigation took place, it collected a simple list of telephone numbers dialed from the monitored phones.

Modern call records contain much more data, reflecting the fact that almost all of us carry cell phones. A call record now includes unique device identifiers, routing information, cell tower IDs, and a wealth of additional information about the circumstances and location of the call. The location data is particularly powerful, turning mobile phones into de facto tracking devices whenever they are turned on.

Fourth is the question of oversight. The evidence used in the Balitmore case was collected by municipal police and presented (I'm assuming) in open court. Those against whom it was used had the chance to mount a defense, appeal the verdict to state and Federal courts, and enjoyed the presumption of innocence guaranteed to them by the Constitution.

The NSA call data is collected and used in secret. The agency is overseen as part of the very large national security establishment by a small, overworked group of legislators and senior government officials who have the requisite security clearance.

So I contend that the parallel Simon makes is false. The NSA is not a law enforcement organization, and intuitions from police reporting don't carry over.

But even if we grant the analogy, I think there's a more dangerous argument in Simon's essay, which is the contention that two programs that differ only in degree are necessarily "the same old thing". I believe this is not a safe assumption to make when talking about computers and their use in domestic surveillance.

In the portion of his essay that excited the most comment, Simon appears to express disbelief that the NSA can make broad use of the data it gathers:

When the government grabs every single fucking telephone call made from the United States over a period of months and years, it is not a prelude to monitoring anything in particular. Why not? Because that is tens of billions of phone calls and for the love of god, how many agents do you think the FBI has? How many computer-runs do you think the NSA can do — and then specifically analyze and assess each result?

Well, of course, the answer is "you would not believe how many 'computer-runs' the NSA can do". I believe this part of the essay especially caught tech people's attention, since it suggested that Simon might be naive about the capabilities of a modern datacenter. It's certainly the part Clay Shirky pounced on in his rebuttal.

But Simon is not a fogey who doesn't understand how powerful computers have become (though I feel that there are such people in positions of oversight in the House and Senate). I believe his error is in assuming that the analysis of these 'computer-runs' is any kind of bottleneck. There are powerful techniques for surfacing interesting features in any comprehensive list of interactions between human beings. I've written in the past about my distaste for the 'social graph' and the perverse worldview it imposes on our projects, but part of the appeal of that worldview is the real power of mathematics applied to exactly this kind of data. The analysis can be automated, and no good comes of it.

In a beautiful worked example, Kieran Healey has shown how a precocious British intelligence service could have identified Paul Revere as a person of particular interest based only on a set of membership lists of organizations he belonged to.

The point is, you don't need human investigators to find leads, you can have the algorithms do it. They will find people of interest, assemble the watch lists, and flag whomever you like for further tracking. And since the number of actual terrorists is very, very, very small, the output of these algorithms will consist overwhelmingly of false positives.

It's at this point that Simon's logic starts to work in the other direction. Given a long list of potential leads, investigators are going to focus on vetting the most likely, rather than taking any steps to clear false positives out of system. The penalty for missing a real terrorist is catastrophic, while the penalty for falsely accusing someone (when not only the accusation, but the very existence of the program, is secret) is nonexistent, even if the secret accusation ends up doing real harm. Limits on manpower won't constrain the investigation; they will only reduce its overall quality.

This isn't an abstract argument. We are all familiar with the tenebrous no fly list, a document that prevents several thousand people from traveling by air, and condemns thousands more to intrusive security measures each time they want to get on a plane. After 2001, this list rapidly expanded to thousands of names, with no avenues of appeal and no way to even check whether your name appeared in the document, to the point where the government finally had to improvise a 'redress' policy for travelers who found themselves living out a Kafka novel.

Characteristically, proposals for fixing the no-fly list and similar watch lists now call for collecting even more information, to help disambiguate people who share a name but not a date of birth with someone on the watch list. The basic problem—that lists of suspects are generated without accountability, without oversight, and with no incentive to avoid mistakes—persists.

There's also a more dangerous institutional problem to consider. When a system like this exists, it creates pressure for its own use. What is the point, after all, of having a very elaborate, extremely expensive ② database if you are only ever going to use it in exceptional cases? It is the nature of law enforcement to want to go after bad guys with all available tools. We saw a vivid demonstration of this in the years after the 2001 attacks, when the administration attempted to blur the lines between the 'War on Drugs' and the 'War on Terror', arguing that the proceeds from narcotics sales paid for terrorism.

Consider, too, a technique that has become standard in Federal investigations. It is a felony to make false statements to a Federal agent, and investigators routinely make use of this fact to gain leverage over a witness or suspect. People tend to be nervous when they talk to police, and unless they know better are liable to give inconsistent answers during questioning. Good interrogators can convert each of these inconsistencies into a felony count. Imagine how much more potent this tactic becomes when investigators can gain access to a database of your movements and contacts for the past decade.

The security state operates as a ratchet. Once you click in a new level of surveillance or intrusiveness, it becomes the new baseline. What was unthinkable yesterday becomes permissible in exceptional cases today, and routine tomorrow. The people who run the American security apparatus are in the overwhelming majority diligent people with a deep concern for civil liberties. But their job is to find creative ways to collect information. And they work within an institution that, because of its secrecy, is fundamentally inimical to democracy and to a free society.

I can't believe that David Simon, of all people, doesn't see the danger inherent in a permanent domestic surveillance program. I doubt that he would support a government initiative for all Americans to wear tracking devices in the name of fighting terrorism. Yet the NSA data collection program, whose output is functionally identical, seems not to trip the same alarm bells with him.

-:-

In public statements, the NSA director has defended domestic surveillance as a vital tool in preventing terrorism.

The term 'terrorism' is a magic word, unlocking government powers we normally associate with wartime. The current and previous Administration have, at various times, asserted the right of the government to conduct invasive and open-ended surveillance on people it suspects of terrorism, detain suspects in terrorism cases indefinitely without trial, 'render' them to countries for interrogation and torture, kill people it considers terrorists, including American citizens, with giant flying robots, or keep such people alive against their own will.

This is total power over human life. The authorities assure us that numerous checks exist to prevent abuses of this power, but of course the checks are also classified. The government is promising that the secret police won't put innocent people in the secret prisons because the secret courts would never allow it.

This system puts enormous pressure on a small group of fallible human beings. For the secrecy to work, the number of people in on the secret must be small ③. But this group is all part of the same hierarchy, subject to the same pressures, and unable to communicate its concerns outside the same closed circle.

Talk of secret prisons, indefinite detention, and force-feeding can sound tendentious (though it's all uncontested public record!). Americans have a deep faith in the rule of law and have not proven receptive to the argument that truly innocent people will find themselves placed in the "terrorist" category by accident.

There is a tendency among those who grew up under the rule of law to treat it like the Rock of Ages, an immovable substrate in which all the institutions of the state are forever anchored. And so even ordinarily skeptical people tend to assume that the government obeys its own laws when no one is looking. To an astonishing extent, and to the great credit of American civic life, this is actually true.

But I think a better metaphor for the rule of law is that it is the soil in which democratic institutions take root. Like the soil, it can be depleted. And once depleted, it is not easily replenished.

Secrecy erodes the rule of law because it makes democratic accountability impossible. Secrets can't be held too broadly, so secrecy concentrates responsibility and asks too much of human nature. That is why every intelligence agency, unless given rigorous outside oversight, commits terrible excesses.

I think Simon agrees about the perniciousness of this secrecy. In a later rebuttal he's called for a modern-day version of the Church Committee, a group of people from outside the security establishment with top-secret access and the power to compel testimony.

And I agree with Simon that the current state of affairs is the "inevitable consequence of legislation that we drafted and passed."

American politics since the Cold War has operated under the conceit that national security must transcend partisan differences. And so we have seen large bipartisan majorities voting for pre-emptive war and domestic surveillance even though both of those policies were highly controversial outside Congress.

This tradition has created a vast space beyond political accountability. When both political parties pursue a nearly identical policy, there are no electoral consequences when the policy proves disastrously wrong. Who do you vote against?

People have good intuitions about the danger of indiscriminate collection and retention of their data. They're not being hysterical. For the last decade, we've been concentrating on how to regulate the way this data gets used in the private sector. But now that the coercive power of the state has entered the picture, the stakes are much higher, and we have an opportunity to politicize the debate. David Simon tells us to resign ourselves to the consequences of technological change:

"The question is not should the resulting data exist. It does. And it forever will, to a greater and greater extent."

But I think that is wrong. Whether the data should exist, and for how long, is exactly the question. The answer is not a technological inevitability, but a political choice.

I believe a world in which everything is recorded and persists forever carries the seeds of something monstrous ④. It is in the nature of computer systems to remember things indefinitely, but there's nothing difficult about programming machines to forget. It just requires laws to do it. We can't treat it as a technical problem. And to get the laws passed, we need to politicize the issue.

Still, these barricades are going to seem awfully lonely if we can't even get David Simon up there with us. The man should be a natural ally, and the fact that he sounds so exasperated troubles me. The fact that he seems resigned to a future of total information retention troubles me. The fact that we are talking past each other troubles me most of all.

① Simon also mentions the FBI, but it's unclear to me that this agency has anything to do with the accusations of widespread call monitoring.

② The expensive part is keeping everything secret, and staffing it with people cleared for such access. The database itself is likely quite modest in size.

③ The Washington Post has estimated the number of people with Top Secret clearance at 854,000. The number of people with full knowledge of all secret programs is much smaller, as this information is carefully compartmentalized.

④ Except Pinboard archives. Those are great!