On a typical day at school, endless hours are spent learning the answers to questions, but right now, we'll do the opposite.
We're going to focus on questions where you can't learn the answers because they're unknown.
I used to puzzle about a lot of things as a boy, for example: What would it feel like to be a dog?
Do fish feel pain?
How about insects?
Was the Big Bang just an accident?
And is there a God?
And if so, how are we so sure that it's a He and not a She?
Why do so many innocent people and animals suffer terrible things?
Is there really a plan for my life?
Is the future yet to be written, or is it already written and we just can't see it?
But then, do I have free will?
I mean, who am I anyway?
Am I just a biological machine?
But then, why am I conscious?
What is consciousness?
Will robots become conscious one day?
I mean, I kind of assumed that some day I would be told the answers to all these questions.
Someone must know, right?
Guess what?
No one knows.
Most of those questions puzzle me more now than ever.
But diving into them is exciting because it takes you to the edge of knowledge, and you never know what you'll find there.
So, two questions that no one on Earth knows the answer to.
(Music) [How many universes are there?]
Sometimes when I'm on a long plane flight, I gaze out at all those mountains and deserts and try to get my head around how vast our Earth is.
And then I remember that there's an object we see every day that would literally fit one million Earths inside it: the Sun.
It seems impossibly big.
But in the great scheme of things, it's a pinprick, one of about 400 billion stars in the Milky Way galaxy, which you can see on a clear night as a pale white mist stretched across the sky.
And it gets worse.
There are maybe 100 billion galaxies detectable by our telescopes.
So if each star was the size of a single grain of sand, just the Milky Way has enough stars to fill a 30-foot by 30-foot stretch of beach three feet deep with sand.
And the entire Earth doesn't have enough beaches to represent the stars in the overall universe.
Such a beach would continue for literally hundreds of millions of miles.
Holy Stephen Hawking, that is a lot of stars.
But he and other physicists now believe in a reality that is unimaginably bigger still.
I mean, first of all, the 100 billion galaxies within range of our telescopes are probably a minuscule fraction of the total.
Space itself is expanding at an accelerating pace.
The vast majority of the galaxies are separating from us so fast that light from them may never reach us.
Still, our physical reality here on Earth is intimately connected to those distant, invisible galaxies.
We can think of them as part of our universe.
They make up a single, giant edifice obeying the same physical laws and all made from the same types of atoms, electrons, protons, quarks, neutrinos, that make up you and me.
However, recent theories in physics, including one called string theory, are now telling us there could be countless other universes built on different types of particles, with different properties, obeying different laws.
Most of these universes could never support life, and might flash in and out of existence in a nanosecond.
But nonetheless, combined, they make up a vast multiverse of possible universes in up to 11 dimensions, featuring wonders beyond our wildest imagination.
The leading version of string theory predicts a multiverse made up of 10 to the 500 universes.
That's a one followed by 500 zeros, a number so vast that if every atom in our observable universe had its own universe, and all of the atoms in all those universes each had their own universe, and you repeated that for two more cycles, you'd still be at a tiny fraction of the total, namely, one trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillionth.
(Laughter) But even that number is minuscule compared to another number: infinity.
Some physicists think the space-time continuum is literally infinite and that it contains an infinite number of so-called pocket universes with varying properties.
How's your brain doing?
Quantum theory adds a whole new wrinkle.
I mean, the theory's been proven true beyond all doubt, but interpreting it is baffling, and some physicists think you can only un-baffle it if you imagine that huge numbers of parallel universes are being spawned every moment, and many of these universes would actually be very like the world we're in, would include multiple copies of you.
In one such universe, you'd graduate with honors and marry the person of your dreams, and in another, not so much.
Well, there are still some scientists who would say, hogwash.
The only meaningful answer to the question of how many universes there are is one.
Only one universe.
And a few philosophers and mystics might argue that even our own universe is an illusion.
So, as you can see, right now there is no agreement on this question, not even close.
All we know is the answer is somewhere between zero and infinity.
Well, I guess we know one other thing.
This is a pretty cool time to be studying physics.
We just might be undergoing the biggest paradigm shift in knowledge that humanity has ever seen.
(Music) [Why can't we see evidence of alien life?]
Somewhere out there in that vast universe there must surely be countless other planets teeming with life.
But why don't we see any evidence of it?
Well, this is the famous question asked by Enrico Fermi in 1950: Where is everybody?
Conspiracy theorists claim that UFOs are visiting all the time and the reports are just being covered up, but honestly, they aren't very convincing.
But that leaves a real riddle.
In the past year, the Kepler space observatory has found hundreds of planets just around nearby stars.
And if you extrapolate that data, it looks like there could be half a trillion planets just in our own galaxy.
If any one in 10,000 has conditions that might support a form of life, that's still 50 million possible life-harboring planets right here in the Milky Way.
So here's the riddle: our Earth didn't form until about nine billion years after the Big Bang.
Countless other planets in our galaxy should have formed earlier, and given life a chance to get underway billions, or certainly many millions of years earlier than happened on Earth.
If just a few of them had spawned intelligent life and started creating technologies, those technologies would have had millions of years to grow in complexity and power.
On Earth, we've seen how dramatically technology can accelerate in just 100 years.
In millions of years, an intelligent alien civilization could easily have spread out across the galaxy, perhaps creating giant energy-harvesting artifacts or fleets of colonizing spaceships or glorious works of art that fill the night sky.
At the very least, you'd think they'd be revealing their presence, deliberately or otherwise, through electromagnetic signals of one kind or another.
And yet we see no convincing evidence of any of it.
Why?
Well, there are numerous possible answers, some of them quite dark.
Maybe a single, superintelligent civilization has indeed taken over the galaxy and has imposed strict radio silence because it's paranoid of any potential competitors.
It's just sitting there ready to obliterate anything that becomes a threat.
Or maybe they're not that intelligent, or perhaps the evolution of an intelligence capable of creating sophisticated technology is far rarer than we've assumed.
After all, it's only happened once on Earth in four billion years.
Maybe even that was incredibly lucky.
Maybe we are the first such civilization in our galaxy.
Or, perhaps civilization carries with it the seeds of its own destruction through the inability to control the technologies it creates.
But there are numerous more hopeful answers.
For a start, we're not looking that hard, and we're spending a pitiful amount of money on it.
Only a tiny fraction of the stars in our galaxy have really been looked at closely for signs of interesting signals.
And perhaps we're not looking the right way.
Maybe as civilizations develop, they quickly discover communication technologies far more sophisticated and useful than electromagnetic waves.
Maybe all the action takes place inside the mysterious recently discovered dark matter, or dark energy, that appear to account for most of the universe's mass.
Or, maybe we're looking at the wrong scale.
Perhaps intelligent civilizations come to realize that life is ultimately just complex patterns of information interacting with each other in a beautiful way, and that that can happen more efficiently at a small scale.
So, just as on Earth, clunky stereo systems have shrunk to beautiful, tiny iPods, maybe intelligent life itself, in order to reduce its footprint on the environment, has turned itself microscopic.
So the Solar System might be teeming with aliens, and we're just not noticing them.
Maybe the very ideas in our heads are a form of alien life.
Well, okay, that's a crazy thought.
The aliens made me say it.
But it is cool that ideas do seem to have a life all of their own and that they outlive their creators.
Maybe biological life is just a passing phase.
Well, within the next 15 years, we could start seeing real spectroscopic information from promising nearby planets that will reveal just how life-friendly they might be.
And meanwhile, SETI, the Search for Extraterrestrial Intelligence, is now releasing its data to the public so that millions of citizen scientists, maybe including you, can bring the power of the crowd to join the search.
And here on Earth, amazing experiments are being done to try to create life from scratch, life that might be very different from the DNA forms we know.
All of this will help us understand whether the universe is teeming with life or whether, indeed, it's just us.
Either answer, in its own way, is awe-inspiring, because even if we are alone, the fact that we think and dream and ask these questions might yet turn out to be one of the most important facts about the universe.
And I have one more piece of good news for you.
The quest for knowledge and understanding never gets dull.
It doesn't.
It's actually the opposite.
The more you know, the more amazing the world seems.
And it's the crazy possibilities, the unanswered questions, that pull us forward.
So stay curious.
So, a little while ago, members of my family had three bits of minor surgery, about a half hour each, and we got three sets of bills.
For the first one, the anesthesia bill alone was 2,000 dollars; the second one, 2,000 dollars; the third one, 6,000 dollars.
So I'm a journalist.
I'm like, what's up with that?
I found out that I was actually, for the expensive one, being charged 1,419 dollars for a generic anti-nausea drug that I could buy online for two dollars and forty-nine cents.
I had a long and unsatisfactory argument with the hospital, the insurer and my employer.
Everybody agreed that this was totally fine.
But it got me thinking, and the more I talked to people, the more I realized: nobody has any idea what stuff costs in health care.
Not before, during or after that procedure or test do you have any idea what it's going to cost.
It's only months later that you get an "explanation of benefits" that explains exactly nothing.
So this came back to me a little while later.
I had volunteered for a buyout from the New York Times, where I had worked for more than 20 years as a journalist.
I was looking for my next act.
It turned out that next act was to build a company telling people what stuff costs in health care.
I won a "Shark Tank"-type pitch contest to do just that.
Health costs ate up almost 18 percent of our gross domestic product last year, but nobody has any idea what stuff costs.
But what if we did know?
So we started out small.
We called doctors and hospitals and asked them what they would accept as a cash payment for simple procedures.
Some people were helpful.
A lot of people hung up on us.
Some people were just plain rude.
They said, "We don't know," or, "Our lawyers won't let us tell you that," though we did get a lot of information.
We found, for example, that here in the New York area, you could get an echocardiogram for 200 dollars in Brooklyn or for 2,150 dollars in Manhattan, just a few miles away.
New Orleans, the same simple blood test, 19 dollars over here, 522 dollars just a few blocks away.
San Francisco, the same MRI, 475 dollars or 6,221 dollars just 25 miles away.
These pricing variations existed for all the procedures and all the cities that we surveyed.
Then we started to ask people to tell us their health bills.
In partnership with public radio station WNYC here in New York, we asked women to tell us the prices of their mammograms.
People told us nobody would do that, that it was too personal.
But in the space of three weeks, 400 women told us about their prices.
Then we started to make it easier for people to share their data into our online searchable database.
It's sort of like a mash-up of Kayak.com and the Waze traffic app for health care.
(Laughter) We call it a community-created guide to health costs.
Our survey and crowdsourcing work grew into partnerships with top newsrooms nationwide -- in New Orleans, Philadelphia, San Francisco, Los Angeles, Miami and other places.
We used the data to tell stories about people who were suffering and how to avoid that suffering, to avoid that "gotcha" bill.
A woman in New Orleans saved nearly 4,000 dollars using our data.
A San Francisco contributor saved nearly 1,300 dollars by putting away his insurance card and paying cash.
There are a lot of people who are going to in-network hospitals and getting out-of-network bills.
And then there was the hospital that continued to bill a dead man.
We learned that thousands of people wanted to tell us their prices.
They want to learn what stuff costs, find out how to argue a bill, help us solve this problem that's hurting them and their friends and families.
We talked to people who had to sell a car to pay a health bill, go into bankruptcy, skip a treatment because of the cost.
Imagine if you could afford the diagnosis but not the cure.
We set off a huge conversation about costs involving doctors and hospitals, yes, but also their patients, or as we like to call them, people.
(Laughter) We changed policy.
A consumer protection bill that had been stalled in the Louisiana legislature for 10 years passed after we launched.
Let's face it: this huge, slow-rolling public health crisis is a national emergency.
And I don't think government's going to help us out anytime soon.
But what if the answer was really simple: make all the prices public all the time.
Would our individual bills go down?
Our health premiums?
Be really clear about this: this is a United States problem.
In most of the rest of the developed world, sick people don't have to worry about money.
It's also true that price transparency will not solve every problem.
There will still be expensive treatments, huge friction from our insurance system.
There will still be fraud and a massive problem with overtreatment and overdiagnosis.
And not everything is shoppable.
Not everybody wants the cheapest appendectomy or the cheapest cancer care.
But when we talk about these clear effects, we're looking at a real issue that's actually very simple.
When we first started calling for prices, we actually felt like we were going to be arrested.
It seemed kind of transgressive to talk about medicine and health care in the same breath, and yet it became liberating, because we found not only data but also good and honest people out there in the system who want to help folks get the care they need at a price they can afford.
And it got easier to ask.
So I'll leave you with some questions.
What if we all knew what stuff cost in health care in advance?
What if, every time you Googled for an MRI, you got drop-downs telling you where to buy and for how much, the way you do when you Google for a laser printer?
What if all of the time and energy and money that's spent hiding prices was squeezed out of the system?
What if each one of us could pick the $19 test every time instead of the $522 one?
Would our individual bills go down?
Our premiums?
I don't know, but if you don't ask, you'll never know.
And you might save a ton of money.
And I've got to think that a lot of us and the system itself would be a lot healthier.
Thank you.
(Applause)