Every day, a sea of decisions stretches before us.
Some are small and unimportant, but others have a larger impact on our lives.
For example, which politician should I vote for?
Should I try the latest diet craze?
Or will email make me a millionaire?
We're bombarded with so many decisions that it's impossible to make a perfect choice every time.
But there are many ways to improve our chances, and one particularly effective technique is critical thinking.
This is a way of approaching a question that allows us to carefully deconstruct a situation, reveal its hidden issues, such as bias and manipulation, and make the best decision.
If the critical part sounds negative that's because in a way it is.
Rather than choosing an answer because it feels right, a person who uses critical thinking subjects all available options to scrutiny and skepticism.
Using the tools at their disposal, they'll eliminate everything but the most useful and reliable information.
There are many different ways of approaching critical thinking, but here's one five-step process that may help you solve any number of problems.
One: formulate your question.
In other words, know what you're looking for.
This isn't always as straightforward as it sounds.
For example, if you're deciding whether to try out the newest diet craze, your reasons for doing so may be obscured by other factors, like claims that you'll see results in just two weeks.
But if you approach the situation with a clear view of what you're actually trying to accomplish by dieting, whether that's weight loss, better nutrition, or having more energy, that'll equip you to sift through this information critically, find what you're looking for, and decide whether the new fad really suits your needs.
Two: gather your information.
There's lots of it out there, so having a clear idea of your question will help you determine what's relevant.
If you're trying to decide on a diet to improve your nutrition, you may ask an expert for their advice, or seek other people's testimonies.
Information gathering helps you weigh different options, moving you closer to a decision that meets your goal.
Three: apply the information, something you do by asking critical questions.
Facing a decision, ask yourself, "What concepts are at work?"
"What assumptions exist?"
"Is my interpretation of the information logically sound?"
For example, in an email that promises you millions, you should consider, "What is shaping my approach to this situation?"
"Do I assume the sender is telling the truth?"
"Based on the evidence, is it logical to assume I'll win any money?"
Four: consider the implications.
Imagine it's election time, and you've selected a political candidate based on their promise to make it cheaper for drivers to fill up on gas.
At first glance, that seems great.
But what about the long-term environmental effects?
If gasoline use is less restricted by cost, this could also cause a huge surge in air pollution, an unintended consequence that's important to think about.
Five: explore other points of view.
Ask yourself why so many people are drawn to the policies of the opposing political candidate.
Even if you disagree with everything that candidate says, exploring the full spectrum of viewpoints might explain why some policies that don't seem valid to you appeal to others.
This will allow you to explore alternatives, evaluate your own choices, and ultimately help you make more informed decisions.
This five-step process is just one tool, and it certainly won't eradicate difficult decisions from our lives.
But it can help us increase the number of positive choices we make.
Critical thinking can give us the tools to sift through a sea of information and find what we're looking for.
And if enough of us use it, it has the power to make the world a more reasonable place.
As the story goes, the legendary marksman William Tell was forced into a cruel challenge by a corrupt lord.
William's son was to be executed unless William could shoot an apple off his head.
William succeeded, but let's imagine two variations on the tale.
In the first variation, the lord hires a bandit to steal William's trusty crossbow, so he is forced to borrow an inferior one from a peasant.
However, the borrowed crossbow isn't adjusted perfectly, and William finds that his practice shots cluster in a tight spread beneath the bullseye.
Fortunately, he has time to correct for it before it's too late.
Variation two: William begins to doubt his skills in the long hours before the challenge and his hand develops a tremor.
His practice shots still cluster around the apple but in a random pattern.
Occasionally, he hits the apple, but with the wobble, there is no guarantee of a bullseye.
He must settle his nervous hand and restore the certainty in his aim to save his son.
At the heart of these variations are two terms often used interchangeably: accuracy and precision.
The distinction between the two is actually critical for many scientific endeavours.
Accuracy involves how close you come to the correct result.
Your accuracy improves with tools that are calibrated correctly and that you're well-trained on.
Precision, on the other hand, is how consistently you can get that result using the same method.
Your precision improves with more finely incremented tools that require less estimation.
The story of the stolen crossbow was one of precision without accuracy.
William got the same wrong result each time he fired.
The variation with the shaky hand was one of accuracy without precision.
William's bolts clustered around the correct result, but without certainty of a bullseye for any given shot.
You can probably get away with low accuracy or low precision in everyday tasks.
But engineers and researchers often require accuracy on microscopic levels with a high certainty of being right every time.
Factories and labs increase precision through better equipment and more detailed procedures.
These improvements can be expensive, so managers must decide what the acceptable uncertainty for each project is.
However, investments in precision can take us beyond what was previously possible, even as far as Mars.
It may surprise you that NASA does not know exactly where their probes are going to touch down on another planet.
Predicting where they will land requires extensive calculations fed by measurements that don't always have a precise answer.
How does the Martian atmosphere's density change at different elevations?
What angle will the probe hit the atmosphere at?
What will be the speed of the probe upon entry?
Computer simulators run thousands of different landing scenarios, mixing and matching values for all of the variables.
Weighing all the possibilities, the computer spits out the potential area of impact in the form of a landing ellipse.
In 1976, the landing ellipse for the Mars Viking Lander was 62 x 174 miles, nearly the area of New Jersey.
With such a limitation, NASA had to ignore many interesting but risky landing areas.
Since then, new information about the Martian atmosphere, improved spacecraft technology, and more powerful computer simulations have drastically reduced uncertainty.
In 2012, the landing ellipse for the Curiosity Lander was only 4 miles wide by 12 miles long, an area more than 200 times smaller than Viking's.
This allowed NASA to target a specific spot in Gale Crater, a previously un-landable area of high scientific interest.
While we ultimately strive for accuracy, precision reflects our certainty of reliably achieving it.
With these two principles in mind, we can shoot for the stars and be confident of hitting them every time.
There's an ancient and universal concept that words have power, that spells exist, and that if we could only pronounce the right words, then -- whoosh! -- you know, an avalanche would come and wipe out the hobbits, right?
So this is a very attractive idea, because we're very lazy, like the Sorcerer's Apprentice, or the world's greatest computer programmer.
This idea has a lot of traction with us.
We love the idea that words, when pronounced, are little more than pure information, but they evoke physical action in the real world that helps us do work.
So, of course, with lots of programmable computers and robots around, this is an easy thing to picture.
How many of you know what I'm talking about?
Raise your right hand.
How many don't know what I'm talking about?
Raise your left hand.
So that's great.
So that was too easy.
You guys have very insecure computers, OK?
So now the thing is, this is a different kind of spell.
This is a computer program made of zeros and ones.
It can be pronounced on a computer, does something like this.
The important thing is we can write it in a high-level language.
A computer magician can write this thing.
It can be compiled into zeros and ones and pronounced by a computer.
And that's what makes computers powerful, these high-level languages that can be compiled.
And so, I'm here to tell you, you don't need a computer to actually have a spell.
In fact, what you can do at the molecular level is that if you encode information -- you encode a spell or program as molecules -- then physics can actually directly interpret that information and run a program.
It's what happens in proteins.
When this amino-acid sequence gets pronounced as atoms, these little letters are sticky for each other.
It collapses into a three-dimensional shape that turns it into a nanomachine that actually cuts DNA.
The interesting thing is that if you change the sequence, you change the three-dimensional folding.
You get, now, a DNA stapler, instead.
These are the kind of molecular programs we want to be able to write.
The problem is, we don't know the machine language of proteins or have a compiler for proteins.
So I've joined a growing band of people that try to make molecular spells using DNA.
We use DNA because it's cheaper, it's easier to handle, it's something we understand really well -- so well, in fact, that we think we can actually write programming languages for DNA and have molecular compilers.
So then, we think we can do that.
One of my first questions doing this was: How can you make an arbitrary shape or pattern out of DNA?
I decided to use a type of DNA origami, where you take a long strand of DNA and fold it into whatever shape or pattern you might want.
So here's a shape.
I actually spent about a year in my home in my underwear, coding, like Linus [Torvalds], in that picture before.
This program takes a shape and spits out 250 DNA sequences.
These short DNA sequences are what are going to fold the long strand into this shape that we want to make.
So you send an e-mail with these sequences in it to a company, and the company pronounces them on a DNA synthesizer, a machine about the size of a photocopier.
And they take your e-mail, and every letter in your e-mail, they replace with a 30-atom cluster -- one for each letter, A, T, C and G in DNA.
They string them up in the right sequence, and then they send them back to you via FedEx.
So you get 250 of these in the mail in little tubes.
I mix them together, add a little bit of salt water, and then add this long strand I was telling you about, that I've stolen from a virus.
And then what happens is, you heat this whole thing up to about boiling.
You cool it down to room temperature, and as you do, those short strands do the following thing: each one of them binds that long strand in one place, and then has a second half that binds that long strand in a distant place, and brings those two parts of the long strand close together so they stick together.
So the net effect of all 250 of these strands is to fold the long strand into the shape you're looking for.
It'll approximate that shape.
We do this for real, in the test tube.
In each little drop of water, you get 50 billion of these guys.
With a microscope, you can see them on a surface.
The neat thing is if you change the sequence and change the spell, just change the sequence of the staples, you can make a molecule that looks like this.
And, you know, he likes to hang out with his buddies.
A lot of them are actually pretty good.
If you change the spell again, you change the sequence again, you get really nice, 130-nanometer triangles.
If you do it again, you can get arbitrary patterns.
So on a rectangle, you can paint patterns of North and South America, or the words, "DNA."
So that's DNA origami.
That's one way.
There are many ways of casting molecular spells using DNA.
What we really want to do in the end is learn how to program self-assembly so we can build anything, right?
We want to be able to build technological artifacts that are maybe good for the world.
We want to learn how to build biological artifacts, like people and whales and trees.
And if it's the case that we can reach that level of complexity, if our ability to program molecules gets to be that good, then that will truly be magic.
Thank you very much.
(Applause)