It's six o'clock in the morning, pitch black outside.
My 14-year-old son is fast asleep in his bed, sleeping the reckless, deep sleep of a teenager.
I flip on the light and physically shake the poor boy awake, because I know that, like ripping off a Band-Aid, it's better to get it over with quickly.
(Laughter) I have a friend who yells "Fire!" just to rouse her sleeping teen.
And another who got so fed up that she had to dump cold water on her son's head just to get him out of bed.
Sound brutal ...
but perhaps familiar?
Every morning I ask myself, "How can I -- knowing what I know and doing what I do for a living -- be doing this to my own son?"
You see, I'm a sleep researcher.
(Laughter) So I know far too much about sleep and the consequences of sleep loss.
I know that I'm depriving my son of the sleep he desperately needs as a rapidly growing teenager.
I also know that by waking him up hours before his natural biological clock tells him he's ready, I'm literally robbing him of his dreams -- the type of sleep most associated with learning, memory consolidation and emotional processing.
But it's not just my kid that's being deprived of sleep.
Sleep deprivation among American teenagers is an epidemic.
Only about one in 10 gets the eight to 10 hours of sleep per night recommended by sleep scientists and pediatricians.
Now, if you're thinking to yourself, "Phew, we're doing good, my kid's getting eight hours," remember, eight hours is the minimum recommendation.
You're barely passing.
Eight hours is kind of like getting a C on your report card.
There are many factors contributing to this epidemic, but a major factor preventing teens from getting the sleep they need is actually a matter of public policy.
Not hormones, social lives or Snapchat.
Across the country, many schools are starting around 7:30am or earlier, despite the fact that major medical organizations recommend that middle and high school start no earlier than 8:30am.
These early start policies have a direct effect on how much -- or really how little sleep American teenagers are getting.
They're also pitting teenagers and their parents in a fundamentally unwinnable fight against their own bodies.
Around the time of puberty, teenagers experience a delay in their biological clock, which determines when we feel most awake and when we feel most sleepy.
This is driven in part by a shift in the release of the hormone melatonin.
Teenagers' bodies wait to start releasing melatonin until around 11pm, which is two hours later than what we see in adults or younger children.
This means that waking a teenager up at 6am is the biological equivalent of waking an adult mmeyers@example.net.
On the unfortunate days when I have to wake up at 4am, I'm a zombie.
Functionally useless.
I can't think straight, I'm irritable, and I probably shouldn't be driving a car.
But this is how many American teenagers feel every single school day.
In fact, many of the, shall we say, unpleasant characteristics that we chalk up to being a teenager -- moodiness, irritability, laziness, depression -- could be a product of chronic sleep deprivation.
For many teens battling chronic sleep loss, their go-to strategy to compensate is consuming large quantities of caffeine in the form of venti frappuccinos, or energy drinks and shots.
So essentially, we've got an entire population of tired but wired youth.
Advocates of sleep-friendly start times know that adolescence is a period of dramatic brain development, particularly in the parts of the brain that are responsible for those higher order thinking processes, including reasoning, problem-solving and good judgment.
In other words, the very type of brain activity that's responsible for reining in those impulsive and often risky behaviors that are so characteristic of adolescence and that are so terrifying to us parents of teenagers.
They know that like the rest of us, when teenagers don't get the sleep they need, their brains, their bodies and behaviors suffer with both immediate and lasting effects.
They can't concentrate, their attention plummets and many will even show behavioral signs that mimic ADHD.
But the consequences of teen sleep loss go well beyond the classroom, sadly contributing to many of the mental health problems that skyrocket during adolescence, including substance use, depression and suicide.
In our work with teens from LA Unified School District, we found that teens with sleep problems were 55 percent more likely to have used alcohol in the past month.
In another study with over 30,000 high school students, they found that for each hour of lost sleep, there was a 38 percent increase in feeling sad or hopeless, and a 58 percent increase in teen suicide attempts.
And if that's not enough, teens who skip out on sleep are at increased risk for a host of physical health problems that plague our country, including obesity, heart disease and diabetes.
Then there's the risk of putting a sleep-deprived teen, with a newly minted driver's license, behind the wheel.
Studies have shown that getting five hours or less of sleep per night is the equivalent of driving with a blood alcohol content above the legal limit.
Advocates of sleep-friendly start times, and researchers in this area, have produced tremendous science showing the tremendous benefits of later start times.
The findings are unequivocal, and as a sleep scientist, I rarely get to speak with that kind of certainty.
Teens from districts with later start times get more sleep.
To the naysayers who may think that if schools start later, teens will just stay up later, the truth is, their bedtimes stay the same, but their wake-up times get extended, resulting in more sleep.
They're more likely to show up for school; school absences dropped by 25 percent in one district.
And they're less likely to drop out.
Not surprisingly, they do better academically.
So this has real implications for reducing the achievement gap.
Standardized test scores in math and reading go up by two to three percentage points.
That's as powerful as reducing class sizes by one-third fewer students, or replacing a so-so teacher in the classroom with a truly outstanding one.
Their mental and physical health improves, and even their families are happier.
I mean, who wouldn't enjoy a little more pleasantness from our teens, and a little less crankiness?
Even their communities are safer because car crash rates go down -- a 70 percent reduction in one district.
Given these tremendous benefits, you might think, well, this is a no-brainer, right?
So why have we as a society failed to heed this call?
Often the argument against later start times goes something like this: "Why should we delay start times for teenagers?
We need to toughen them up so they're ready for the real world!"
But that's like saying to the parent of a two-year-old, "Don't let Johnny nap, or he won't be ready for kindergarten."
(Laughter) Delaying start times also presents many logistical challenges.
Not just for students and their families, but for communities as a whole.
Updating bus routes, increased transportation costs, impact on sports, care before or after school.
These are the same concerns that come up in district after district, time and again around the country as school start times are debated.
And they're legitimate concerns, but these are problems we have to work through.
They are not valid excuses for failing to do the right thing for our children, which is to start middle and high schools no earlier than 8:30am.
And in districts around the country, big and small, who have made this change, they found that these fears are often unfounded and far outweighed by the tremendous benefits for student health and performance, and our collective public safety.
So tomorrow morning, when coincidentally we get to set our clocks back by an hour and you get that delicious extra hour of sleep, and the day seems a little longer, and a little more full of hope, think about the tremendous power of sleep.
And think about what a gift it would be for our children to be able to wake up naturally, in harmony with their own biology.
Thank you, and pleasant dreams.
I'm sure that, throughout the 100,000-odd years of our species' existence and even before, our ancestors looked up at the night sky and wondered what stars are -- wondering, therefore, how to explain what they saw in terms of things unseen.
OK, so, most people only wondered that occasionally, like today, in breaks from whatever normally preoccupied them.
But what normally preoccupied them also involved yearning to know.
They wished they knew how to prevent their food supply from sometimes failing, and how they could rest when they were tired without risking starvation, be warmer, cooler, safer, in less pain.
I bet those prehistoric cave artists would have loved to know how to draw better.
(Laughter) In every aspect of their lives, they wished for progress, just as we do.
But they failed, almost completely, to make any.
They didn't know how to.
Discoveries like fire happened so rarely that, from an individual's point of view, the world never improved.
Nothing new was learned.
The first clue to the origin of starlight happened as recently as 1899: radioactivity.
And within 40 years, physicists discovered the whole explanation, expressed, as usual, in elegant symbols.
But never mind the symbols.
Think how many discoveries they represent.
Nuclei and nuclear reactions, of course.
But isotopes, particles of electricity, antimatter, neutrinos, the conversion of mass to energy -- that's E=mc2 -- gamma rays, transmutation.
That ancient dream that had always eluded the alchemists was achieved through these same theories that explained starlight and other ancient mysteries and new, unexpected phenomena.
That all that, discovered in 40 years, had not been in the previous hundred thousand was not for lack of thinking about stars and all those other urgent problems they had.
They even arrived at answers, such as myths, that dominated their lives, yet bore almost no resemblance to the truth.
The tragedy of that protracted stagnation isn't sufficiently recognized, I think.
These were people with brains of essentially the same design that eventually did discover all those things.
But that ability to make progress remained almost unused, until the event that revolutionized the human condition and changed the universe.
Or so we should hope, because that event was the scientific revolution, ever since which our knowledge of the physical world and of how to adapt it to our wishes has been growing relentlessly.
Now, what had changed?
What were people now doing for the first time that made that difference between stagnation and rapid, open-ended discovery?
How to make that difference is surely the most important universal truth that it's possible to know.
And worryingly, there's no consensus about what it is.
So, I'll tell you.
(Laughter) But I'll have to backtrack a little first.
Before the scientific revolution, they believed that everything important, knowable, was already known, enshrined in ancient writings, institutions and in some genuinely useful rules of thumb -- which were, however, entrenched as dogmas, along with many falsehoods.
So, they believed that knowledge came from authorities that actually knew very little.
And therefore, progress depended on learning how to reject the authority of learned men, the priests, traditions and rulers, which is why the scientific revolution had to have a wider context: the Enlightenment, a revolution in how people sought knowledge, trying not to rely on authority.
"Take no one's word for it."
But that can't be what made the difference.
Authorities had been rejected before, many times.
And that rarely, if ever, caused anything like the scientific revolution.
At the time, what they thought distinguished science was a radical idea about things unseen, known as empiricism -- all knowledge derives from the senses.
Well, we've seen that that can't be true.
It did help by promoting observation and experiment.
But, from the outset, it was obvious that there was something horribly wrong with it.
Knowledge comes from the senses?
In what language?
Certainly not the language of mathematics, in which, Galileo rightly said, the book of nature is written.
Look at the world.
You don't see equations carved on the mountainsides.
If you did, it would be because people had carved them.
By the way, why don't we do that?
(Laughter) What's wrong with us?
(Laughter) Empiricism is inadequate because, well, scientific theories explain the seen in terms of the unseen.
And the unseen, you have to admit, doesn't come to us through the senses.
We don't see those nuclear reactions in stars.
We don't see the origin of species.
We don't see the curvature of space-time, and other universes.
But we know about those things.
How?
Well, the classic empiricist answer is induction -- the unseen resembles the seen.
But it doesn't.
You know what the clinching evidence was that space-time is curved?
It was a photograph -- not of space-time, but of an eclipse, with a dot there rather than there.
And the evidence for evolution?
Some rocks and some finches.
And parallel universes?
Again: dots there rather than there, on a screen.
What we see in all these cases bears no resemblance to the reality that we conclude is responsible -- only a long chain of theoretical reasoning and interpretation connects them.
"Ah!" say creationists.
"So you admit it's all interpretation.
No one's ever seen evolution.
We see rocks.
You have your interpretation.
We have ours.
Yours comes from guesswork; ours, from the Bible."
But what creationist and empiricists both ignore is that, in that sense, no one's ever seen a Bible either, that the eye only detects light, which we don't perceive.
Brains only detect nerve impulses.
And they don't perceive even those as what they really are, namely electrical crackles.
So we perceive nothing as what it really is.
Our connection to reality is never just perception.
It's always, as Karl Popper put it, theory-laden.
Scientific knowledge isn't derived from anything.
Like all knowledge, it's conjectural, guesswork, tested by observation, not derived from it.
So, were testable conjectures the great innovation that opened the intellectual prison gates?
No, contrary to what's usually said, testability is common in myths and all sorts of other irrational modes of thinking.
Any crank claiming the sun will go out next Tuesday has got a testable prediction.
Consider the ancient Greek myth explaining seasons.
Hades, god of the underworld, kidnaps Persephone, the goddess of spring, and negotiates a forced marriage contract, requiring her to return regularly, and lets her go.
And each year, she is magically compelled to return.
And her mother, Demeter, goddess of the earth, is sad, and makes it cold and barren.
That myth is testable.
If winter is caused by Demeter's sadness, then it must happen everywhere on earth simultaneously.
So if the ancient Greeks had only known that Australia is at its warmest when Demeter is at her saddest ...
(Laughter) they'd have known that their theory is false.
(Laughter) So, what was wrong with that myth and with all prescientific thinking?
And what, then, made that momentous difference?
I think there's one thing you have to care about and that implies testability, the scientific method, the Enlightenment and everything.
And here's the crucial thing: there is such a thing as a defect in a story.
I don't just mean a logical defect.
I mean a bad explanation.
What does that mean?
Well, an explanation is an assertion about what's there, unseen, that accounts for what's seen; because the explanatory role of Persephone's marriage contract could be played equally well by infinitely many other ad hoc entities.
Why a marriage contract and not any other reason for regular annual action?
Here's one: Persephone wasn't released.
She escaped, and returns every spring to take revenge on Hades, with her spring powers.
She cools his domain with spring air, venting heat up to the surface, creating summer.
That accounts for the same phenomena as the original myth.
It's equally testable.
Yet what it asserts about reality is, in many ways, the opposite.
And that's possible because the details of the original myth are unrelated to seasons, except via the myth itself.
This easy variability is the sign of a bad explanation, because, without a functional reason to prefer one of countless variants, advocating one of them in preference to the others is irrational.
So, for the essence of what makes the difference to enable progress, seek good explanations, the ones that can't be easily varied, while still explaining the phenomena.
Now our current explanation of seasons is that the Earth's axis is tilted like that, so each hemisphere tilts towards the sun for half the year, and away for the other half.
[Not to scale!]
Better put that up.
(Laughter) That's a good explanation: hard to vary, because every detail plays a functional role.
For instance, we know, independently of seasons, that surfaces tilted away from radiant heat are heated less, and that a spinning sphere, in space, points in a constant direction.
And the tilt also explains the sun's angle of elevation at different times of year, and predicts that the seasons will be out of phase in the two hemispheres.
If they'd been observed in phase, the theory would have been refuted.
But now, the fact that it's also a good explanation, hard to vary, makes the crucial difference.
If the ancient Greeks had found out about seasons in Australia, they could have easily varied their myth to predict that.
For instance, when Demeter's upset, she banishes heat from her vicinity into the other hemisphere, where it makes summer.
So, being proved wrong by observation and changing their theory accordingly still wouldn't have got the ancient Greeks one jot closer to understanding seasons, because their explanation was bad -- easy to vary.
And it's only when an explanation is good that it even matters whether it's testable.
If the axis-tilt theory had been refuted, its defenders would have had nowhere to go.
No easily implemented change could make that tilt cause the same seasons in both hemispheres.
The search for hard-to-vary explanations is the origin of all progress.
It's the basic regulating principle of the Enlightenment.
So, in science, two false approaches blight progress.
One's well-known: untestable theories.
But the more important one is explanationless theories.
Whenever you're told that some existing statistical trend will continue but you aren't given a hard-to-vary account of what causes that trend, you're being told a wizard did it.
When you are told that carrots have human rights because they share half our genes, but not how gene percentages confer rights -- wizard.
When someone announces that the nature-nurture debate has been settled because there's evidence that a given percentage of our political opinions are genetically inherited, but they don't explain how genes cause opinions, they've settled nothing.
They're saying that our opinions are caused by wizards, and presumably, so are their own.
(Laughter) That the truth consists of hard-to-vary assertions about reality is the most important fact about the physical world.
It's a fact that is itself unseen, yet impossible to vary.
Thank you.
(Applause)