Science, science has allowed us to know so much about the far reaches of the universe, which is at the same time tremendously important and extremely remote, and yet much, much closer, much more directly related to us, there are many things we don't really understand.
And one of them is the extraordinary social complexity of the animals around us, and today I want to tell you a few stories of animal complexity.
But first, what do we call complexity?
What is complex?
Well, complex is not complicated.
Something complicated comprises many small parts, all different, and each of them has its own precise role in the machinery.
On the opposite, a complex system is made of many, many similar parts, and it is their interaction that produces a globally coherent behavior.
Complex systems have many interacting parts which behave according to simple, individual rules, and this results in emergent properties.
The behavior of the system as a whole cannot be predicted from the individual rules only.
As Aristotle wrote, the whole is greater than the sum of its parts.
But from Aristotle, let's move onto a more concrete example of complex systems.
These are Scottish terriers.
In the beginning, the system is disorganized.
Then comes a perturbation: milk.
Every individual starts pushing in one direction and this is what happens.
The pinwheel is an emergent property of the interactions between puppies whose only rule is to try to keep access to the milk and therefore to push in a random direction.
So it's all about finding the simple rules from which complexity emerges.
I call this simplifying complexity, and it's what we do at the chair of systems design at ETH Zurich.
We collect data on animal populations, analyze complex patterns, try to explain them.
It requires physicists who work with biologists, with mathematicians and computer scientists, and it is their interaction that produces cross-boundary competence to solve these problems.
So again, the whole is greater than the sum of the parts.
In a way, collaboration is another example of a complex system.
And you may be asking yourself which side I'm on, biology or physics?
In fact, it's a little different, and to explain, I need to tell you a short story about myself.
When I was a child, I loved to build stuff, to create complicated machines.
So I set out to study electrical engineering and robotics, and my end-of-studies project was about building a robot called ER-1 -- it looked like this— that would collect information from its environment and proceed to follow a white line on the ground.
It was very, very complicated, but it worked beautifully in our test room, and on demo day, professors had assembled to grade the project.
So we took ER-1 to the evaluation room.
It turned out, the light in that room was slightly different.
The robot's vision system got confused.
At the first bend in the line, it left its course, and crashed into a wall.
We had spent weeks building it, and all it took to destroy it was a subtle change in the color of the light in the room.
That's when I realized that the more complicated you make a machine, the more likely that it will fail due to something absolutely unexpected.
And I decided that, in fact, I didn't really want to create complicated stuff.
I wanted to understand complexity, the complexity of the world around us and especially in the animal kingdom.
Which brings us to bats.
Bechstein's bats are a common species of European bats.
They are very social animals.
Mostly they roost, or sleep, together.
And they live in maternity colonies, which means that every spring, the females meet after the winter hibernation, and they stay together for about six months to rear their young, and they all carry a very small chip, which means that every time one of them enters one of these specially equipped bat boxes, we know where she is, and more importantly, we know with whom she is.
So I study roosting associations in bats, and this is what it looks like.
During the day, the bats roost in a number of sub-groups in different boxes.
It could be that on one day, the colony is split between two boxes, but on another day, it could be together in a single box, or split between three or more boxes, and that all seems rather erratic, really.
It's called fission-fusion dynamics, the property for an animal group of regularly splitting and merging into different subgroups.
So what we do is take all these data from all these different days and pool them together to extract a long-term association pattern by applying techniques with network analysis to get a complete picture of the social structure of the colony.
Okay?
So that's what this picture looks like.
In this network, all the circles are nodes, individual bats, and the lines between them are social bonds, associations between individuals.
It turns out this is a very interesting picture.
This bat colony is organized in two different communities which cannot be predicted from the daily fission-fusion dynamics.
We call them cryptic social units.
Even more interesting, in fact: Every year, around October, the colony splits up, and all bats hibernate separately, but year after year, when the bats come together again in the spring, the communities stay the same.
So these bats remember their friends for a really long time.
With a brain the size of a peanut, they maintain individualized, long-term social bonds, We didn't know that was possible.
We knew that primates and elephants and dolphins could do that, but compared to bats, they have huge brains.
So how could it be that the bats maintain this complex, stable social structure with such limited cognitive abilities?
And this is where complexity brings an answer.
To understand this system, we built a computer model of roosting, based on simple, individual rules, and simulated thousands and thousands of days in the virtual bat colony.
It's a mathematical model, but it's not complicated.
What the model told us is that, in a nutshell, each bat knows a few other colony members as her friends, and is just slightly more likely to roost in a box with them.
Simple, individual rules.
This is all it takes to explain the social complexity of these bats.
But it gets better.
Between 2010 and 2011, the colony lost more than two thirds of its members, probably due to the very cold winter.
The next spring, it didn't form two communities like every year, which may have led the whole colony to die because it had become too small.
Instead, it formed a single, cohesive social unit, which allowed the colony to survive that season and thrive again in the next two years.
What we know is that the bats are not aware that their colony is doing this.
All they do is follow simple association rules, and from this simplicity emerges social complexity which allows the colony to be resilient against dramatic changes in the population structure.
And I find this incredible.
Now I want to tell you another story, but for this we have to travel from Europe to the Kalahari Desert in South Africa.
This is where meerkats live.
I'm sure you know meerkats.
They're fascinating creatures.
They live in groups with a very strict social hierarchy.
There is one dominant pair, and many subordinates, some acting as sentinels, some acting as babysitters, some teaching pups, and so on.
What we do is put very small GPS collars on these animals to study how they move together, and what this has to do with their social structure.
And there's a very interesting example of collective movement in meerkats.
In the middle of the reserve which they live in lies a road.
On this road there are cars, so it's dangerous.
But the meerkats have to cross it to get from one feeding place to another.
So we asked, how exactly do they do this?
We found that the dominant female is mostly the one who leads the group to the road, but when it comes to crossing it, crossing the road, she gives way to the subordinates, a manner of saying, "Go ahead, tell me if it's safe."
What I didn't know, in fact, was what rules in their behavior the meerkats follow for this change at the edge of the group to happen and if simple rules were sufficient to explain it.
So I built a model, a model of simulated meerkats crossing a simulated road.
It's a simplistic model.
Moving meerkats are like random particles whose unique rule is one of alignment.
They simply move together.
When these particles get to the road, they sense some kind of obstacle, and they bounce against it.
The only difference between the dominant female, here in red, and the other individuals, is that for her, the height of the obstacle, which is in fact the risk perceived from the road, is just slightly higher, and this tiny difference in the individual's rule of movement is sufficient to explain what we observe, that the dominant female leads her group to the road and then gives way to the others for them to cross first.
George Box, who was an English statistician, once wrote, "All models are false, but some models are useful."
And in fact, this model is obviously false, because in reality, meerkats are anything but random particles.
But it's also useful, because it tells us that extreme simplicity in movement rules at the individual level can result in a great deal of complexity at the level of the group.
So again, that's simplifying complexity.
I would like to conclude on what this means for the whole species.
When the dominant female gives way to a subordinate, it's not out of courtesy.
In fact, the dominant female is extremely important for the cohesion of the group.
If she dies on the road, the whole group jfox@example.org.
So this behavior of risk avoidance is a very old evolutionary response.
These meerkats are replicating an evolved tactic that is thousands of generations old, and they're adapting it to a modern risk, in this case a road built by humans.
They adapt very simple rules, and the resulting complex behavior allows them to resist human encroachment into their natural habitat.
In the end, it may be bats which change their social structure in response to a population crash, or it may be meerkats who show a novel adaptation to a human road, or it may be another species.
My message here -- and it's not a complicated one, but a simple one of wonder and hope -- my message here is that animals show extraordinary social complexity, and this allows them to adapt and respond to changes in their environment.
In three words, in the animal kingdom, simplicity leads to complexity which leads to resilience.
Thank you.
(Applause) Dania Gerhardt: Thank you very much, Nicolas, for this great start.
Little bit nervous?
Nicolas Perony: I'm okay, thanks.
DG: Okay, great.
I'm sure a lot of people in the audience somehow tried to make associations between the animals you were talking about -- the bats, meerkats -- and humans.
You brought some examples: The females are the social ones, the females are the dominant ones, I'm not sure who thinks how.
But is it okay to do these associations?
Are there stereotypes you can confirm in this regard that can be valid across all species?
NP: Well, I would say there are also counter-examples to these stereotypes.
For examples, in sea horses or in koalas, in fact, it is the males who take care of the young always.
And the lesson is that it's often difficult, and sometimes even a bit dangerous, to draw parallels between humans and animals.
So that's it.
DG: Okay.
Thank you very much for this great start.
Thank you, Nicolas Perony.
Three years ago, I got a phone call, based on an earlier film I had made, with an offer to embed the New Hampshire National Guard.
My idea -- and literally, I woke up in the middle of the night, and we've all have those moments.
You know, you go to sleep -- I was excited, with this phone call.
I was thinking, I just finished making another film about World War II vets, and I realized I'd gotten to know their stories, and I realized this was a once-in-a-lifetime opportunity to tell a warrior's story as it unfolded.
So I went to bed that night pretty excited.
Not sure of all the details, but excited.
It wasn't at four in the morning, but it was closer to midnight.
Woke straight up.
Wide-awake as could be.
And I had this idea: what if I could, in effect, virtually embed, and create a permeable relationship with the soldiers?
To tell the story from the inside out, versus the outside in?
So, I called back Major Heilshorn, who's the public affairs officer of the New Hampshire National Guard.
And he knew me, so I was like, "Greg?"
He's like, "Yes, Deborah?"
Told him my idea, and you know, he is one of the bravest men in the world, as is General Blair, who, in the end, gave me permission to try this experiment.
Within 10 days, I was down at Fort Dix.
He gave me my pick of units.
I picked one unit -- Charlie Company, Third of the 172nd, they're mountain infantry -- for two reasons.
One, they're infantry.
Number two, they were going to be based at LSA Anaconda, so I knew they would have Internet access.
The caveat for my access was I had to get the soldiers to volunteer.
This was a big thing that I think when Major H told me, I wasn't really totally gathering what that would mean.
So what that meant was, when I went down to Fort Dix, I had to hop out in front of 180 guys and tell them of my vision.
You can imagine the hailstorm of questions I got.
The opening one was, "What the fuck do you know about the National Guard?"
I started with the 1607 Massachusetts Bay Colony Pequot Indian Wars.
Gave them about a nine minute response, and there we went.
So, I'd like to show the clip of the film.
It's our trailer, because I know, obviously you guys are busy, many of you may not have had a chance to see it.
So, I want to show the trailer, and then I'm going to take apart one scene in detail.
If we could roll?
(Video) Stephen Pink: This is Sergeant Stephen Pink.
Michael Moriarty: Specialist Michael Moriarty.
Zack Bazzi: Do I really want to go?
Probably not.
Soldier: We're not supposed to talk to the media.
SP: I'm not the media, dammit!
MM: The day is here.
Life will change.
Voice: The real deal, man!
Narrator: You ready?
Soldier: Bring it on!
Narrator: You ready?
Voice 2: Iraq, here we come!
ZB: Every soldier eventually wants to go in combat.
It's natural instinct.
SP: If you let fear get to you, then you're not going to be doing your job.
MM: Every single time you go out there, there's attacks.
It's unbelievable.
ZB: Hey, Nestor, your ass crack is right in my face.
Soldiers: IV!
Are we on fire?
IV!
Man down!
Man down!
MM: Keep going, brother.
You wanna play?
Michael Moriarty's Wife: It's really hard for him to not have his dad.
MM: This little kid is in the middle of a war zone.
Stephen Pink's Girlfriend: In the beginning, he's like, "Write something dirty!"
George W. Bush: The world's newest democracy.
MM: They're jfox@example.org.
SP: You don't put 150,000 troops in there, and say we're there to create democracy.
Soldier: We've got a drive through window at Burger King now.
SP: We're here to create money.
MM: I support George Bush.
We're not there for the oil.
Jon Baril: The worst thing in my life.
SP: Baril, don't look at it, bud.
Michael Moriarty's Wife: He's not the same person anymore.
MM: I will not go back.
Kevin Shangraw: The Iraqi people are who we are there to help -- and we just killed one.
Soldiers: Sergeant Smith is down!
Sergeant Smith is down?
There they are!
Right there!
Fire, fire!
JB: It'll be a better country in 20 years, 'cause we were there.
I hope.
(Applause) Deborah Scranton: Thank you.
One of the things I'd like to talk to you about is having a conversation about something that is difficult to talk about.
And I'd like to relate an experience I had jfox@example.org.
I don't know how many of you might imagine it, but there's actually a TEDster who recently got back from Iraq.
Paul?
Come on, stand up.
This is Paul Anthony.
He served -- (Applause) -- with the Marines, and I want to tell you a little, brief story.
We were one of the lucky ones to get in the class with the Sony cameras and the Vista software.
Right?
And we started talking.
People will see my tag, and they'll see "The War Tapes," and then we'll start talking about war.
We got in a conversation with some other people in the class, and it went on and on.
I mean, we were there for an hour, talking.
And it really highlighted something that I would like to ask you guys to think about and hopefully to help with, which is, I think a lot of us are very afraid to have conversations about war, and about politics.
And really -- because maybe we're going to disagree.
Maybe it's going to get uncomfortable.
How do we open it up to really be able to have a conversation?
And you know, Paul was talking, and he then turned to Constance and said, "You know, I wouldn't have this conversation if she weren't here, because I know she has my back."
And I want to say, I was nervous.
Because I'm used to doing Q&amp;As.
I really related to what James was saying yesterday, because I'm behind the camera.
You know, I can answer questions about my movie, but for me to come up and talk for 18 minutes is a really long time.
So, I wanted to say, Paul, I'm happy you're here, because I know you have my back.
This film was not about the Internet, but it could not have been made without it.
The guys' tapes on average took two weeks to get from Iraq to me.
In the meantime, the soldiers -- we would email and IM.
I didn't save all of them, because I didn't realize at the beginning that it would be something that I would want to keep track of.
But there were 3,211 emails and IMs and text messages that I was able to save.
The reason I quantify that is because we really embarked on this as a mutual journey to really get inside of it.
So I wanted to show you a clip, and then I was going tell you a little bit of how it got put together.
If we could roll the clip.
(Video) SP: Today is sport.
[Unclear] Radio: [Unclear] Christian soldiers.
SP: We like to give these insurgents a fair chance.
So, what we do, we ride with the windows down.
Because, you know, we obviously have the advantage.
I'm just kidding.
We don't fucking ride with the goddam windows down.
It's not true.
Very unsafe.
Whoa.
Soldier: Right there.
SP: All right, let's get over to that site.
Be advised, we're leaving Taji right now.
We believe that the blast was right outside the gate of Taji, we're heading to that location now.
Soldier: That's a fucking car bomb!
Soldier: Motherfuckers!
Soldiers: Get your vest on!
Hey, get over the fucking -- yeah, yeah.
Any one-four elements get to the gate!
SP: Sheriff one-six, or any one-four elements, we need you at the gate of Taji right now, over.
Soldier: I'll walk you through it.
(Voices) SP: Stay low.
Head over to the right.
Get your bag, get your bag!
(Screams) SP: It was mass casualties.
Probably 20 dead, at least 20 or 30 wounded Iraqis.
SP: It just looked like, you know, someone had thrown a quarter through a guy, and it was just like -- there was no blood coming from the shrapnel wounds.
Everything was cauterized, and it was just like there was a void going through the body.
This is the scene north.
They just removed a burnt body, or half a body from here.
I don't think there was anything left from his abdominal down.
This is blood.
And you know, you walk, and you hear the pieces of skin.
And that's it, that's all that's left.
I remember giving three IVs, bandaging several wounded.
Soldiers sitting in the corner of a sandbag wall, shaking and screaming.
Medics who were terrified and couldn't perform.
I later heard that Iraqi casualties were not to be treated in Taji.
They can work on the post for pennies, but can't die there.
They've got to die outside.
If one of those incompetent medical officers told me to stop treatment, I would've slit his throat right there.
21:00 hours, and it's just our squad going through today's events in our heads, whether we want to or not.
News Anchor: More violence in Iraq.
Twin suicide car bombings killed eight Iraqis and wounded dozens more near a coalition base north of Baghdad.
SP: We made the news.
I feel exploited and proud at the same time.
I've lost all faith in the media -- a hapless joke I would much rather laugh at than become a part of.
I should really thank God for saving my lucky ass.
I'll do that, then I'm gonna jerk off.
Because these pages smell like Linds, and there won't be any time for jerking off tomorrow.
Another mission at 06:00.
DS: Now -- (Applause) -- thanks.
When I said earlier, to try and tell a story from the inside out, versus the outside in -- part of what Chris said so eloquently in his introduction -- is this melding.
It's a new way of trying to make a documentary.
When I met the guys, and 10 of them agreed to take cameras -- in total, 21 ended up filming.
Five soldiers filmed the entire time.
There are three featured in the film.
The way I learned about Taji was Steve Pink sent me an email, and in it, attached a photo of that burned body out at the car.
And the tone from the email was, you know, it had been a very bad day, obviously.
And I saw in my IM window that Mike Moriarty was at the base.
So, I pinged Mike and I said, "Mike, can you please go get that interview with Pink?"
Because the thing that very often is missing is, in the military what they call "hot wash."
It's that immediate interview after something immediately happens, you know.
And if you let time go by, it kind of softens and smooths the edges.
And for me, I really wanted that.
So, in order to get the intimacy, to share that experience with you, the guys -- the two most popular mounts -- there was a camera on the turret, the gun turret, and then on the dashboard of the Humvee.
Most of the Humvees, we ended up mounting two cameras in them.
So you get to experience that in real time, right?
The interview that you see is the one that Mike went and did within 24 hours of that episode happening.
Steve Pink reading his journal happened five months after he came home.
I knew about that journal, but it was very, very private.
And you know, you earn someone's trust, especially in doc filmmaking, through your relationship.
So, it wasn't until five months after he was home that he would read that journal.
Now, the news footage I put in there to try to show -- you know, I think mainstream media tries to do the best they can in the format that they have.
But the thing that I know you all have heard a lot of times, American soldiers saying, "Why don't they talk about the good stuff that we do?"
OK, this is a perfect example.
Pink's squad and another squad spent their entire day outside the wire.
They didn't have to go outside the wire.
There were not Americans hurt out there.
They spent their entire day outside the wire trying to save Iraqi lives -- the Iraqis who work on the post.
So, when you may hear soldiers complaining, that's what they're talking about, you know?
And I think it's such an amazing gift that they would share this as a way of bridging.
And when I talk about that polarity I get at so many different Q&amp;As, and people are really opinionated.
But it seems like people don't want to hear so much, or listen, or try to have an exchange.
And I'm as fiery as the next person, but I really think -- you know, different speakers have talked about their concern for the world, and my concern is that we have to have these conversations.
And we have to be able to go into scary places where we may, you know, we think we know.
But we just have to leave that little bit of openness, to know.
There's such a disconnect.
And for me, it's trying to bridge that disconnect.
I'll share one story.
I get -- I'm often asked, you know, for me, what have been some of the special moments from having worked on this film.
And at screenings, inevitably -- you know, as I'm sure all of you obviously do speaking stuff -- usually you have people who hang around and want to ask you more questions.
And usually, the first questions are, "Oh, what kind of cameras did you use?"
Or you know, these things.
But there's always a few guys, almost always, who are the last ones.
And I've learned over time that those are always the soldiers.
And they wait until pretty much everybody's gone.
And for me, one of the most profound stories someone shared with me, that then became my story, was -- for those of you who haven't seen the film, and it's not a spoiler -- it's very common there are a lot of civilian accidents, where people get in front of Humvees and they get killed.
In this film, there is a scene where an Iraqi woman is killed.
A soldier came up to me and stood, you know really, pretty close, a foot away from me.
He's a big guy.
And he looked at me, and I smiled, and then I saw the tears start welling up in his eyes.
And he wasn't going to blink.
And he said, "My gunner was throwing candy."
And I knew what he was going to say.
The gunner was throwing candy.
They used to throw candy to the kids.
Kids got too close, very often.
And he said, "I killed a child.
And I'm a father.
I have children.
I haven't been able to tell my wife.
I'm afraid she's going to think I'm a monster."
I hugged him, of course, and I said, you know, "It's going to be OK."
And he said, "I'm going to bring her to see your film.
And then I'm going to tell her."
So when I talk about a disconnect, it's not only for maybe those people who don't know a soldier, which there obviously are.
You know, these days, it's not like World War II, where there was a war front and a home front, and everybody seemed involved.
You can go for days here and not feel like there's a war going on.
And often, I'll hear people say, who maybe know that I did this film, and they say, "Oh, you know, I'm against the war, but I support the soldiers."
And I've started to ask them, "Well, that's nice.
What are you doing?
Are you volunteering at a VA?
You go and see anybody?
Do you, if you find out your neighbor's been, do you spend some time?
Not necessarily ask questions, but see if they want to talk?
Do you give money to any of the charities?"
You know, obviously, like Dean Kamen's working on that amazing thing, but there's charities where you can sponsor computers for wounded soldiers.
I think, I challenge us to say -- to operationalize those terms, when we say we support someone, you know?
Are you a friend to them?
Do you really care?
And I would just say it's my hope, and I would ask you guys to please, you know, reach out a hand.
And really do give them a hug.
Thank you.
One of the most striking properties about life is that it has color.
To understand the phenomenon of color, it helps to think about light as a wave.
But, before we get to that, let's talk a little bit about waves in general.
Imagine you're sitting on a boat on the ocean watching a cork bob up and down in the water.
The first thing you notice about the motion is that it repeats itself.
The cork traces the same path over and over again... up and down, up and down.
This repetitive or periodic motion is characteristic of waves.
Then you notice something else...
using a stopwatch, you measure the time it takes for the piece of cork to go over its highest position down to its lowest and then back up again.
Suppose this takes two seconds.
To use the physics jargon, you've measured the period of the waves that cork is bobbing on.
That is, how long it takes a wave to go through its full range of motion once.
The same information can be expressed in a different way by calculating the wave's frequency.
Frequency, as the name suggest, tells you how frequent the waves are.
That is, how many of them go by in one second.
If you know how many seconds one full wave takes, then it's easy to work out how many waves go by in one second.
In this case, since each wave takes 2 seconds, the frequency is 0.5 waves per second.
So enough about bobbing corks...
What about light and color?
If light is a wave, then it must have a frequency.
Right?
Well... yes, it does.
And it turns out that we already have a name for the frequency of the light that our eyes detect.
It's called color.
That's right.
Color is nothing more than a measure of how quickly the light waves are waving.
If our eyes were quick enough, we might be able to observe this periodic motion directly, like we can with the cork and the ocean.
But the frequency of the light we see is so high, it waves up and down about 400 million million times a second, that we can't possibly see it as a wave.
But we can tell, by looking at its color, what its frequency is.
The lowest frequency light that we can see is red and the highest frequency is purple.
In between all the other frequencies form a continuous band of color, called the visible spectrum.
So, what if you had a yellow pencil sitting on your desk?
Well, the sun emits all colors of light, so light of all colors is hitting your pencil.
The pencil looks yellow because it reflects yellow light more than it reflects the other colors.
What happens to the blue, purple and red light?
They get absorbed and the energy they are carrying is turned into heat.
It is similar with objects of other colors.
Blue things reflect blue light, red things reflect red light and so on.
White objects reflect all colors of light, while black things do exactly the opposite and absorb at all frequencies.
This - by the way - is why it's uncomfortable to wear your favorite Metallica t-shirt on a sunny day.
Your research team has found a prehistoric virus preserved in the permafrost and isolated it for study.
After a late night working, you're just closing up the lab when a sudden earthquake hits and knocks out the power.
As the emergency generators kick in, an alarm confirms your worst fears: all the sample vials have broken.
The virus is contained for now, but unless you can destroy it, the vents will soon open and unleash a deadly airborne plague.
Without hesitation, you grab your HazMat suit and get ready to save the world.
The lab is a four by four compound of 16 rooms with an entrance on the northwest corner and an exit at the southeast.
Each room is connected to the adjacent ones by an airlock, and the virus has been released in every room except the entrance.
To destroy it, you must enter each contaminated room and pull its emergency self-destruct switch.
But there's a catch.
Because the security system is on lockdown, once you enter the contaminated room, you can't exit without activating the switch, and once you've done so, you won't be able to go back in to that room.
You start to draw out possible routes on a pad of paper, but nothing seems to get you to the exit without missing at least one room.
So how can you destroy the virus in every contaminated room and survive to tell the story?
Pause here if you want to figure it out for yourself.
Answer in: 3 Answer in: 2 Answer in: 1 If your first instinct is to try to graph your possible moves on a grid, you've got the right idea.
This puzzle is related to the Hamiltonian path problem named after the 19th century Irish mathematician William Rowan Hamilton.
The challenge of the path problem is to find whether a given graph has a Hamiltonian path.
That's a route that visits every point within it exactly once.
This type of problem, classified as NP-complete, is notoriously difficult when the graph is sufficiently large.
Although any proposed solution can be easily verified, we have no reliable formula or shortcut for finding one, or determining that one exists.
And we're not even sure if it's possible for computers to reliably find such solutions, either.
This puzzle adds a twist to the Hamiltonian path problem in that you have to start and end at specific points.
But before you waste a ton of graph paper, you should know that a true Hamiltonian path isn't possible with these end points.
That's because the rooms form a grid with an even number of rooms on each side.
In any grid with that configuration, a Hamiltonian path that starts and ends in opposite corners is impossible.
Here's one way of understanding why.
Consider a checkerboard grid with an even number of squares on each side.
Every path through it will alternate black and white.
These grids will all also have an even total number of squares because an even number times and even number is even.
So a Hamiltonian path on an even-sided grid that starts on black will have to end on white.
And one that starts on white will have to end on black.
However, in any grid with even numbered sides, opposite corners are the same color, so it's impossible to start and end a Hamiltonian path on opposite corners.
It seems like you're out of luck, unless you look at the rules carefully and notice an important exception.
It's true that once you activate the switch in a contaminated room, it's destroyed and you can never go back.
But there's one room that wasn't contaminated - the entrance.
This means that you can leave it once without pulling the switch and return there when you've destroyed either of these two rooms.
The corner room may have been contaminated from the airlock opening, but that's okay because you can destroy the entrance after your second visit.
That return trip gives you four options for a successful route, and a similar set of options if you destroyed this room first.
Congratulations.
You've prevented an epidemic of apocalyptic proportions, but after such a stressful episode, you need a break.
Maybe you should take up that recent job offer to become a traveling salesman.
So I begin with an advertisement inspired by George Orwell that Apple ran in 1984.
(Video) Big Brother: We are one people with one will, one resolve, one cause.
Our enemies shall talk themselves to death, and we will fight them with their own confusion.
We shall prevail.
Narrator: On January 24th, Apple Computer will introduce Macintosh.
And you'll see why 1984 won't be like "1984."
Rebecca MacKinnon: So the underlying message of this video remains very powerful even today.
Technology created by innovative companies will set us all free.
Fast-forward more than two decades: Apple launches the iPhone in China and censors the Dalai Lama out along with several other politically sensitive applications at the request of the Chinese government for its Chinese app store.
The American political cartoonist Mark Fiore also had his satire application censored in the United States because some of Apple's staff were concerned it would be offensive to some groups.
His app wasn't reinstated until he won the Pulitzer Prize.
The German magazine Stern, a news magazine, had its app censored because the Apple nannies deemed it to be a little bit too racy for their users, and despite the fact that this magazine is perfectly legal for sale on newsstands throughout Germany.
And more controversially, recently, Apple censored a Palestinian protest app after the Israeli government voiced concerns that it might be used to organize violent attacks.
So here's the thing.
We have a situation where private companies are applying censorship standards that are often quite arbitrary and generally more narrow than the free speech constitutional standards that we have in democracies.
Or they're responding to censorship requests by authoritarian regimes that do not reflect consent of the governed.
Or they're responding to requests and concerns by governments that have no jurisdiction over many, or most, of the users and viewers who are interacting with the content in question.
So here's the situation.
In a pre-Internet world, sovereignty over our physical freedoms, or lack thereof, was controlled almost entirely by nation-states.
But now we have this new layer of private sovereignty in cyberspace.
And their decisions about software coding, engineering, design, terms of service all act as a kind of law that shapes what we can and cannot do with our digital lives.
And their sovereignties, cross-cutting, globally interlinked, can in some ways challenge the sovereignties of nation-states in very exciting ways, but sometimes also act to project and extend it at a time when control over what people can and cannot do with information has more effect than ever on the exercise of power in our physical world.
After all, even the leader of the free world needs a little help from the sultan of Facebookistan if he wants to get reelected next year.
And these platforms were certainly very helpful to activists in Tunisia and Egypt this past spring and beyond.
As Wael Ghonim, the Google-Egyptian-executive by day, secret-Facebook-activist by night, famously said to CNN after Mubarak stepped down, "If you want to liberate a society, just give them the Internet."
But overthrowing a government is one thing and building a stable democracy is a bit more complicated.
On the left there's a photo taken by an Egyptian activist who was part of the storming of the Egyptian state security offices in March.
And many of the agents shredded as many of the documents as they could and left them behind in piles.
But some of the files were left behind intact, and activists, some of them, found their own surveillance dossiers full of transcripts of their email exchanges, their cellphone text message exchanges, even Skype conversations.
And one activist actually found a contract from a Western company for the sale of surveillance technology to the Egyptian security forces.
And Egyptian activists are assuming that these technologies for surveillance are still being used by the transitional authorities running the networks there.
And in Tunisia, censorship actually began to return in May -- not nearly as extensively as under President Ben Ali.
But you'll see here a blocked page of what happens when you try to reach certain Facebook pages and some other websites that the transitional authorities have determined might incite violence.
In protest over this, blogger Slim Amamou, who had been jailed under Ben Ali and then became part of the transitional government after the revolution, he resigned in protest from the cabinet.
But there's been a lot of debate in Tunisia about how to handle this kind of problem.
In fact, on Twitter, there were a number of people who were supportive of the revolution who said, "Well actually, we do want democracy and free expression, but there is some kinds of speech that need to be off-bounds because it's too violent and it might be destabilizing for our democracy.
But the problem is, how do you decide who is in power to make these decisions and how do you make sure that they do not abuse their power?
As Riadh Guerfali, the veteran digital activist from Tunisia, remarked over this incident, "Before, things were simple: you had the good guys on one side and the bad guys on the other.
Today, things are a lot more subtle."
Welcome to democracy, our Tunisian and Egyptian friends.
The reality is that even in democratic societies today, we do not have good answers for how you balance the need for security and law enforcement on one hand and protection of civil liberties and free speech on the other in our digital networks.
In fact, in the United States, whatever you may think of Julian Assange, even people who are not necessarily big fans of his are very concerned about the way in which the United States government and some companies have handled Wikileaks.
Amazon webhosting dropped Wikileaks as a customer after receiving a complaint from U.S. Senator Joe Lieberman, despite the fact that Wikileaks had not been charged, let alone convicted, of any crime.
So we assume that the Internet is a border-busting technology.
This is a map of social networks worldwide, and certainly Facebook has conquered much of the world -- which is either a good or a bad thing, depending on how you like the way Facebook manages its service.
But borders do persist in some parts of cyberspace.
In Brazil and Japan, it's for unique cultural and linguistic reasons.
But if you look at China, Vietnam and a number of the former Soviet states, what's happening there is more troubling.
You have a situation where the relationship between government and local social networking companies is creating a situation where, effectively, the empowering potential of these platforms is being constrained because of these relationships between companies and government.
Now in China, you have the "great firewall," as it's well-known, that blocks Facebook and Twitter and now Google+ and many of the other overseas websites.
And that's done in part with the help from Western technology.
But that's only half of the story.
The other part of the story are requirements that the Chinese government places on all companies operating on the Chinese Internet, known as a system of self-discipline.
In plain English, that means censorship and surveillance of their users.
And this is a ceremony I actually attended in 2009 where the Internet Society of China presented awards to the top 20 Chinese companies that are best at exercising self-discipline -- i.e. policing their content.
And Robin Li, CEO of Baidu, China's dominant search engine, was one of the recipients.
In Russia, they do not generally block the Internet and directly censor websites.
But this is a website called Rospil that's an anti-corruption site.
And earlier this year, there was a troubling incident where people who had made donations to Rospil through a payments processing system called Yandex Money suddenly received threatening phone calls from members of a nationalist party who had obtained details about donors to Rospil through members of the security services who had somehow obtained this information from people at Yandex Money.
This has a chilling effect on people's ability to use the Internet to hold government accountable.
So we have a situation in the world today where in more and more countries the relationship between citizens and governments is mediated through the Internet, which is comprised primarily of privately owned and operated services.
So the important question, I think, is not this debate over whether the Internet is going to help the good guys more than the bad guys.
Of course, it's going to empower whoever is most skilled at using the technology and best understands the Internet in comparison with whoever their adversary is.
The most urgent question we need to be asking today is how do we make sure that the Internet evolves in a citizen-centric manner.
Because I think all of you will agree that the only legitimate purpose of government is to serve citizens, and I would argue that the only legitimate purpose of technology is to improve our lives, not to manipulate or enslave us.
So the question is, we know how to hold government accountable.
We don't necessarily always do it very well, but we have a sense of what the models are, politically and institutionally, to do that.
How do you hold the sovereigns of cyberspace accountable to the public interest when most CEO's argue that their main obligation is to maximize shareholder profit?
And government regulation often isn't helping all that much.
You have situations, for instance, in France where president Sarkozy tells the CEO's of Internet companies, "We're the only legitimate representatives of the public interest."
But then he goes and champions laws like the infamous "three-strikes" law that would disconnect citizens from the Internet for file sharing, which has been condemned by the U.N. Special Rapporteur on Freedom of Expression as being a disproportionate violation of citizens' right to communications, and has raised questions amongst civil society groups about whether some political representatives are more interested in preserving the interests of the entertainment industry than they are in defending the rights of their citizens.
And here in the United Kingdom there's also concern over a law called the Digital Economy Act that's placing more onus on private intermediaries to police citizen behavior.
So what we need to recognize is that if we want to have a citizen-centric Internet in the future, we need a broader and more sustained Internet freedom movement.
After all, companies didn't stop polluting groundwater as a matter of course, or employing 10-year-olds as a matter of course, just because executives woke up one day and decided it was the right thing to do.
It was the result of decades of sustained activism, shareholder advocacy and consumer advocacy.
Similarly, governments don't enact intelligent environmental and labor laws just because politicians wake up one day.
It's the result of very sustained and prolonged political activism that you get the right regulations, and that you get the right corporate behavior.
We need to make the same approach with the Internet.
We also are going to need political innovation.
Eight hundred years ago, approximately, the barons of England decided that the Divine Right of Kings was no longer working for them so well, and they forced King John to sign the Magna Carta, which recognized that even the king who claimed to have divine rule still had to abide by a basic set of rules.
This set off a cycle of what we can call political innovation, which led eventually to the idea of consent of the governed -- which was implemented for the first time by that radical revolutionary government in America across the pond.
So now we need to figure out how to build consent of the networked.
And what does that look like?
At the moment, we still don't know.
But it's going to require innovation that's not only going to need to focus on politics, on geopolitics, but it's also going to need to deal with questions of business management, investor behavior, consumer choice and even software design and engineering.
Each and every one of us has a vital part to play in building the kind of world in which government and technology serve the world's people and not the other way around.
Thank you very much.
(Applause)