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Another election day in the US is rapidly approaching (Tuesday, Nov. 8-mark your calendars!). So for no reason in particular, we're resurfacing our close examination of the Dunning-Kruger effect from May 25, 2012.

In 1999 a pair of researchers published a paper called "Unskilled and Unaware of It: How Difficulties in Recognizing One's Own Incompetence Lead to Inflated Self-Assessments (PDF)." David Dunning and Justin Kruger (both at Cornell University's Department of Psychology at the time) conducted a series of four studies showing that, in certain cases, people who are very bad at something think they are actually pretty good. They showed that to assess your own expertise at something, you need to have a certain amount of expertise already.

Remember the 2008 election campaign? The financial markets were going crazy, and banks that were "too big to fail" were bailed out by the government. Smug EU officials proclaimed that all was well within the EU-even while they were bailing out a number of financial institutions. Fast forward to 2012, and the EU is looking at hard times. Greece can't pay its debt. Italy can, but the markets don't trust it to be able to. Spain and Portugal are teetering around like toddlers just waiting for the market to give them one good push. Members of the public are behaving like teenagers, screaming "F**k you," while flipping the bird. The markets are reacting like drunk parents, and the resulting bruises are going to take a while to heal.

In all of this, uninformed idiots blame the Greeks for being lazy, the Germans for being too strict, and everyone but themselves. Newspapers, blogs, and television are filled with wise commentary hailing the return of the gold standard, the breakup of the Euro, or any number of sensible and not-so-sensible ideas. How are we to parse all this information? Do any of these people know what they are talking about? And if anyone does, how can we know which ones to listen to? The research of Dunning and Kruger may well tell us there is no way to figure out the answers to any of these questions. That is kind of scary.

It has been more than 10 years since Dunning and Kruger published their work. I suspect it has become required reading in psychology courses. It's also a paper that has important implications for learning and communication, so what has happened since? Have the results held up? Are they universal? And what can we do to avoid falling victim to our own inabilities?

"The paper gave voice to an observation that people make about their peers, but that they don't know how to express," Dunning said.

This paper has become a cult classic. It is well-written-humor interspersed with robust data, and conclusions that are discussed in a thorough and accessible way. I wondered if Dunning knew that this paper would become such a classic, and when I spoke with him he responded quite to the contrary. "I frankly thought the paper would never be published," Dunning said. "It really doesn't fit the usual structure of a modern-day research psychology finding. A wise editor who got it and good reviewers showed me wrong there. I am struck just with how long and how much this idea has gone viral in so many areas."

Clearly, the paper struck a chord with many people outside of the field of psychology. "I presume the paper gave voice to an observation that people make about their peers but that they don't know how to express," Dunning responded. If you have not read the paper already, I recommend doing so.

Unfortunately, in those places ruled by the smug and complacent, a classic paper has become a weapon. The findings of Dunning and Kruger are being reduced to "Stupid people are so stupid that they don't know they are stupid." Rather bluntly, Dunning himself said, "The presence of the Dunning-Kruger effect, as it's been come to be called, is that one should pause to worry about one's own certainty, not the certainty of others." And that humorously suggests the Dunning-Kruger effect is now a candidate to become a second Godwin's law.

Like Dunning, I do not take such a dim view of humanity. In fact, Dunning-Kruger and follow-up papers give us cause for hope. They show that people are not usually irredeemably stupid. You can teach people to accurately self-evaluate-though, in their specific examples, this also involved teaching them the very skill they were trying to evaluate.

Context is everything

It is important to realize that the Dunning-Kruger paper was not such a shocking finding. It was, for instance, already known that seemingly everyone evaluates themselves as above average in everything. Are you a better driver than average? Certainly am. How do you rate your ability at math? Oh, a little better than average. How about mountain climbing? Well, I've climbed the local hill a couple of times. I bet Kilimanjaro can't be much more difficult.

A large pile of research on various groups of people, covering various skill sets, indicates that in the face of all evidence, humans are irredeemably optimistic about their own abilities. That is, by itself, not such a bad thing. The ugly side shows up when we also realize that the norm must be maintained. Studies show that we do this by considering that everyone else is much worse. Being clueless about your own abilities is one thing. Misjudging other's abilities is relatively more serious.

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Revisiting why incompetents think they're awesome

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Another election day in the US is rapidly approaching (Tuesday, Nov. 8-mark your calendars!). So for no reason in particular, we're resurfacing our close examination of the Dunning-Kruger effect from May 25, 2012. In 1999 a pair of researchers published a paper called "Unskilled and Unaware of It: How Difficulties in Recognizing One's Own Incompetence Lead to Inflated Self-Assessments (PDF)."

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At five-foot-six and 270 pounds, the bank robber was impossible to miss. On April 19, 1995, he hit two Pittsburgh banks in broad daylight. Security cameras picked up good images of his face - he wore no mask - and showed him holding a gun to the teller. Police made sure the footage was broadcast on the local eleven o'clock news. A tip came in within minutes, and just after midnight, the police were knocking on the suspect's door in McKeesport. Identified as McArthur Wheeler, he was incredulous. "But I wore the juice," hesaid.

Wheeler told police he rubbed lemon juice on his face to make it invisible to security cameras. Detectives concluded he was not delusional, not on drugs - just incrediblymistaken.

Wheeler knew that lemon juice is used as an invisible ink. Logically, then, lemon juice would make his face invisible to cameras. He tested this out before the heists, putting juice on his face and snapping a selfie with a Polaroid camera. There was no face in the photo! (Police never figured that out. Most likely Wheeler was no more competent as a photographer than he was as a bank robber.) Wheeler reported one problem with his scheme: The lemon juice stung his eyes so badly that he could barelysee.

Wheeler went to jail and into the annals of the world's dumbest criminals. It was such a feature, in the 1996 World Almanac, that brought Wheeler's story to the attention of David Dunning, a Cornell psychology professor. He saw in this tale of dim-witted woe something universal. Those most lacking in knowledge and skills are least able to appreciate that lack. This observation would eventually become known as the Dunning-Krugereffect.

Dunning and a graduate student, Justin Kruger, embarked on series of experiments testing this premise. They quizzed undergraduate psychology students on grammar, logic, and jokes, then asked the students to estimate their scores and also estimate how well they did relative to others (on a percentile basis). The students who scored lowest had greatly exaggerated notions of how well they did. Dunning had expected that, but not the magnitude of the effect. His first reaction to the results was "Wow." Those who scored near the bottom estimated that their skills were superior to two-thirds of the otherstudents.

Later research went far beyond the university. For one experiment, Dunning and Kruger recruited gun hobbyists at a trapshooting and skeet-shooting competition. Volunteers took a ten-question gun safety and knowledge quiz adapted from one published by the National Rifle Association. Again, the gun owners who knew the least about firearm safety wildly overestimated theirknowledge.

Like most rules, this one has exceptions. "One need not look far," Dunning and Kruger wrote, "to find individuals with an impressive understanding of the strategies and techniques of basketball, for instance, yet who could not 'dunk' to save their lives. (These people are called coaches.)" But of course coaches understand their own physical limitations. Similarly, "most people have no trouble identifying their inability to translate Slovenian proverbs, reconstruct a V-8 engine, or diagnose acute disseminatedencephalomyelitis."

The Dunning-Kruger effect requires a minimal degree of knowledge and experience in the area about which you are ignorant (and ignorant of your ignorance). Drivers, as a group, are subject to the effect - bad drivers usually think they're good drivers - but those who have never learned how to drive areexempt.

Since Dunning and Kruger first published their results in the 1999 paper "Unskilled and Unaware of It: How Difficulties in Recognizing One's Own Incompetence Lead to Inflated Self-Assessments," the effect named for them has become a meme. It strikes a universal chord: As Dunning put it, the overconfident airhead "is someone we've all met." Actor John Cleese concisely explains the Dunning-Kruger effect in a much-shared YouTube video: "If you're very, very stupid, how can you possibly realize that you're very, very stupid? You'd have to be relatively intelligent to realize how stupid you are ... And this explains not just Hollywood but almost the entirety of Fox News." But the 1999 paper makes clear the authors' opinion that the first place to look for a Dunning-Kruger ignoramus is in themirror.

***

There is now an active field of research into how the internet is changing what we learn and remember. In a 2011 experiment helmed by Daniel Wegner of Harvard, volunteers were presented with a list of 40 trivia facts - short, pithy statements such as "An ostrich's eye is bigger than its brain." Each person was instructed to type all 40 statements into a computer. Half the volunteers were told to remember the facts. The other half weren't. Also, half were informed that their work would be stored on the computer. The other half were told that it would be erased immediately after the task'scompletion.

The volunteers were later given a quiz on the facts they'd typed. Those instructed to remember the information scored no better than those who hadn't been told to do so. But those who believed that their work would be erased scored much better compared to those who believed it would be saved. This was true whether they were trying to remember the facts ornot.

The conscious mind exercises little choice in remembering and forgetting. Nobody decides to forget a client's name or to remember forever the lyrics of a detested pop tune. It justhappens.

The Harvard experiment's results are consistent with a pragmatic system of memory. It is impossible to remember everything. The brain must constantly be doing triage on memories, without conscious intervention. And apparently it recognizes that there is less need to stock our minds with information that can be readily retrieved. (It may be a very long time before you need to know how big an ostrich's eyeball is.) So facts are more often forgotten when people believe the facts will be archived. This phenomenon has earned a name - the Google effect - describing the automatic forgetting of information that can be foundonline.

If you take the Google effect to the point of absurdity, selfies would cause amnesia. But a 2013 study conducted by Linda Henkel of Fairfield University pointed in that direction. Henkel noticed that visitors to art museums are obsessed with taking cell-phone shots of artworks and often are less interested in looking at the art itself. So she performed an experiment at Fairfield University's Bellarmine Museum of Art. Undergraduates took a docent tour in which they were directed to view specific artworks. Some were instructed to photograph the art, and others were simply told to take note of it. The next day both groups were quizzed on their knowledge of the artworks. The visitors who snapped pictures were less able to identify works and to recall visualdetails.

Our unconscious curators of memory must be aware of how quickly and easily any needed fact can be called up. This implies that our broadband networks have created a new regime of learning and memory, one in which facts are less likely to be retained and are more quickly forgotten. In a few years, we'll probably all be wearing devices that shoot a 24-7 video stream of our lives. Will social media make amnesiacs of usall?

Uploaded keystrokes are just one of many ways we have of storing information outside our brains. Long before our virtual social networks, we shared memory, knowledge, and expertise among our real social networks. I'm not a foodie, but I have friends who can recommend interesting new restaurants. I don't know doctors, but I have a general practitioner who can recommend a specialist. We get by in the world, not by knowing everything but by knowingpeople.

Distributed memory can counteract misinformation - to a degree, anyway. Surveys have shown that most people think antibiotics will fight viruses. Wrong. But as Dan M. Kahan of Yale points out, it hardly matters. "Most people" are not going to self-prescribe azithromycin. The important thing is to know that it's a good idea to go to a doctor when we're sick and to follow that doctor'sinstructions.

The Google effect is another adaptation to distributed memory. The cloud is a friend who happens to know everything. It's always available, provides the answer in seconds, and never gets upset with dumb questions. It's little wonder we depend on it to the point of absurdity. Economist Seth Stephens-Davidowitz noted that the third-most-common Google search containing the phrase "my penis" is "How big is my penis?" You'd think a ruler would have a betteranswer.

***

Most - more than 50 percent - of millennials can't name anyone who shot a president or discovered a planet; they don't know the ancient city celebrated for its hanging gardens, the one destroyed by Mount Vesuvius, or the emperor said to have fiddled while Rome burned; and most millennials can't name the single word uttered by the raven in Edgar Allan Poe'spoem.

The conventional reaction to such reports is a blend of shock and amusement. It's terrible how little young people/ordinary citizens know - right? It's worth asking how we know it's so terrible and whether it's terrible atall.

Ignorance can be rational. Economist Anthony Downs made that claim in the 1950s. He meant that there are many situations in which the effort needed to acquire knowledge outweighs the advantage of having it. Maybe you got your diploma and a high-paying job without ever learning about that poem with the raven in it. Why learn itnow?

The contemporary world regards knowledge with ambivalence. We admire learning and retain the view that it is a desirable end in itself. But our more entitled side sees learning as a means to an end - to social advancement, wealth, power, something. We are suspicious of education that lacks an ulterior motive; we click on listicles entitled "8 College Degrees With the Worst Return onInvestment."

Ours is the golden age of rational - and rationalized - ignorance. Information is being produced, devalued, and made obsolete at a prodigious rate. Every day the culture changes beneath our feet. It is harder than ever to keep up or even to be sure that keeping up matters anymore. We are left speculating about how important it is to stay current on the Middle East, contemporary novels, local politics, wearable technology, and college basketball. A friend recently wondered aloud whether it was okay to not know anything about Game of Thrones. The observation that you can look up any needed bit of information dodges the issue. You can't Google a point ofview.

The poorly informed don't necessarily know less. They just know different things. A gamer who spends all his free time playing video games will have an encyclopedic understanding of those games. He is ill-informed only by arbitrary standards of what's important. Not everyone agrees that there is a fixed set of facts that all should know. But absent such a set, the concept of being well-informed becomes a hopelessly relativeone.

Today's mediascape does not provide much guidance. It encourages us to create personal, solipsistic filters over information, making it unprecedentedly easy to gorge on news of favorite celebrities, shows, teams, political ideologies, and tech toys. This leaves less time and attention for everything else. The great risk isn't that the internet is making us less informed or even misinformed. It's that it may be making us meta-ignorant - less cognizant of what we don'tknow.

Adapted from Head in the Cloud: Why Knowing Things Still Matters When Facts Are So Easy to Look Up by William Poundstone. Copyright © 2016 by William Poundstone.

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The Internet Isn't Making Us Dumber - It's Making Us More 'Meta-Ignorant'

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At five-foot-six and 270 pounds, the bank robber was impossible to miss. On April 19, 1995, he hit two Pittsburgh banks in broad daylight. Security cameras picked up good images of his face - he wore no mask - and showed him holding a gun to the teller.

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“The more I learn, the more I realize how much I don't know.” A. Einstein

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“The more I learn, the more I realize how much I don't know.” A. Einstein

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In the field of psychology, the Dunning-Kruger effect is a cognitive bias in which people of low ability have illusory superiority and mistakenly assess their cognitive ability as greater than it is. The cognitive bias of illusory superiority comes from the inability of low-ability people to recognize their lack of ability; without the self-awareness of metacognition, low-ability people cannot objectively evaluate their actual competence or incompetence.

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"The problem with the world is that the stupid are cocksure and the intelligent are full of doubt."                                         B. Russell

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"The problem with the world is that the stupid are cocksure and the intelligent are full of doubt."                                         B. Russell

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Pat is a programmer at a large software company. At best, he's a middling performer; his code is a mess (initializing variables that are never used, using variable names no one else understands, etc.), he takes longer than he should, and he doesn't even remember his own code months later.

But Pat's poor coding skills aren't his most annoying attribute. What frustrates his manager the most is that Pat is absolutely convinced that he's a great programmer. Last month was Pat's performance review, and after receiving a low score from his manager, Pat incredulously argued:

"I'm one of the best programmers in this department! What kind of rating scale are you even using if someone with my talent can get a low score? There's no way that your performance review form is accurately assessing my abilities. Or maybe you're just assessing a bunch of stuff that has nothing to do with actually being a programmer!"

If you've ever dealt with someone whose performance stinks, and they're not only clueless that their performance stinks but they're confident that their performance is good, you likely saw the Dunning-Kruger Effect in action.

Coined in 1999 by then-Cornell psychologists David Dunning and Justin Kruger, the eponymous Dunning-Kruger Effect is a cognitive bias whereby people who are incompetent at something are unable to recognize their own incompetence. And not only do they fail to recognize their incompetence, they're also likely to feel confident that they actually are competent.

Pat's programming skills need a lot of improvement. If Pat saw his deficiencies, he would be able to fix them, he wouldn't fight constructive criticism of his coding, and, frankly, he wouldn't be so frustrating to deal with.

Unfortunately, we know from the more than 10,000 people who've taken the online quiz "How Do You React To Constructive Criticism?" that only 39% of employees handle constructive criticism by systematically dissecting every step leading up to the thing they just got criticized for. They don't freak out or fight the feedback, instead, they want to understand and correct the underlying issues. Now, it's not guaranteed that the other 61% are ensconced in Dunning-Kruger, but it's worth being concerned that they may receive feedback similarly to Pat.

The irony of the Dunning-Kruger Effect is that, Professor Dunning notes, "the knowledge and intelligence that are required to be good at a task are often the same qualities needed to recognize that one is not good at that task-and if one lacks such knowledge and intelligence, one remains ignorant that one is not good at that task."

The 1999 paper that launched the Dunning-Kruger Effect was called "Unskilled and unaware of it: how difficulties in recognizing one's own incompetence lead to inflated self-assessments." Across 4 studies, Professor Dunning and his team administered tests of humor, grammar, and logic. And they found that participants scoring in the bottom quartile grossly overestimated their test performance and ability. For example, in one of the studies, Cornell undergrads took a 20-item grammar test. After completing the test, the students estimated how their ability to "identify grammatically correct standard English" compared with others. And as you might expect, the lowest scoring students grossly overestimated their abilities. Those who scored at the 10th percentile (i.e. they scored higher than only 10% of others) rated their grammar abilities at the 67th percentile. In essence, their actual grammar ability was really poor, but they thought they were in the top third of people.

And it's not just college kids; you can find examples of the Dunning-Kruger Effect everywhere. One study of high-tech firms discovered that 32-42% of software engineers rated their skills as being in the top 5% of their companies. A nationwide survey found that 21% of Americans believe that it's 'very likely' or 'fairly likely' that they'll become millionaires within the next 10 years. Drivers consistently rate themselves above average. Medical technicians overestimate their knowledge in real-world lab procedures. In a classic study of faculty at the University of Nebraska, 68% rated themselves in the top 25% for teaching ability, and more than 90% rated themselves above average (which I'm sure you'll notice is mathematically impossible).

Now, this isn't hopeless. I recently spoke with Professor Dunning, who now teaches at the University of Michigan, and he told me that one of the problems in many organizations is that many people are underperforming simply because they don't know that they could be doing better or what really great performance looks like. It's not that they're necessarily being defensive, rather they just lack the knowledge. In fact, he told me that research subjects were willing to criticize their own previous poor skills once they were trained up and could see the difference between their previous poor performance and their new improved performance.

In "Fewer Than Half Of Employees Know If They're Doing A Good Job," more than 30,000 employees answered dozens of workplace questions, including "I know whether my performance is where it should be." And frighteningly, only 29% of employees say they "always" know whether their performance is where it should be. Meanwhile, a whopping 36% say they "Never" or "Rarely" know. Perhaps before we blame our employees for being so susceptible to the Dunning-Kruger Effect, we ought to look at our leadership skills and ask if we've fomented, or at least aided, this particular cognitive bias.

In upcoming articles, I'll be sharing more of my conversation with Professor Dunning, including how to give people feedback about their performance, given the constraints of the Dunning-Kruger Effect. And I'll also be sharing how you hire people who are less likely to fall prey to the Dunning-Kruger Effect. But in the meantime, let me share a thought from Confucius that gives us all advice for avoiding, or at least mitigating, this cognitive bias: "Real knowledge is to know the extent of one's ignorance."
Mark Murphy is the author of Truth At Work: The Science Of Delivering Tough Messages, Hiring For Attitude and Hundred Percenters.

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The Dunning-Kruger Effect Shows Why Some People Think They're Great Even When Their Work Is Terrible

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Pat is a programmer at a large software company. At best, he's a middling performer; his code is a mess (initializing variables that are never used, using variable names no one else understands, etc.), he takes longer than he should, and he doesn't even remember his own code months later.

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The Elegant Universe:  String theory   'Documentary HD'

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In the second hour of "The Elegant Universe," a three-hour miniseries with physicist Brian Greene, delve into the nuts, bolts, and outright nuttiness of string theory.

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Are protons unstable?
In case you're worried that the protons you're made of will disintegrate, transforming you into a puddle of elementary particles and free energy, don't sweat it. Various observations and experiments show that protons must be stable for at least a billion trillion trillion years. However, many physicists believe that if the three atomic forces are really just different manifestations of a single unified field, the alchemical, supermassive bosons described above will materialize out of quarks every now and then, causing quarks, and the protons they compose, to degenerate.

At first glance, you'd be forgiven for thinking these physicists had experienced some sort of mental decay on the grounds that tiny quarks are unlikely to give birth to behemoth bosons weighing more than 10,000,000,000,000,000 times themselves. But there's something called the Heisenberg uncertainty principle, which states that you can never know both the momentum and the position of a particle at the same time, and it indirectly allows for such an outrageous proposition. Therefore, it's possible for a massive boson to pop out of a quark making up a proton for a very short time and cause that proton to decay.
Question 9
What is gravity?
Next there's the matter of gravity, the odd force out when it comes to small particles and the energy that holds them together. When Einstein improved on Newton's theory, he extended the concept of gravity by taking into account both extremely large gravitational fields and objects moving at velocities close to the speed of light. These extensions lead to the famous concepts of relativity and space-time. But Einstein's theories do not pay any attention to quantum mechanics, the realm of the extremely small, because gravitational forces are negligible at small scales, and discrete packets of gravity, unlike discrete packets of energy that hold atoms together, have never been experimentally observed.

Nonetheless, there are extreme conditions in nature in which gravity is compelled to get up close and personal with the small stuff. For example, near the heart of a black hole, where huge amounts of matter are squeezed into quantum spaces, gravitational forces become very powerful at tiny distances. The same must have been true in the dense primordial universe around the time of the Big Bang.

Physicist Stephen Hawking identified a specific problem about black holes that requires a bridging of quantum mechanics and gravity before we can have a unified theory of anything. According to Hawking, the assertion that nothing, even light, can escape from a black hole is not strictly true. Weak thermal energy does radiate from around black holes. Hawking theorized that this energy is born when particle-antiparticle pairs materialize from the vacuum in the vicinity of a black hole. Before the matter-antimatter particles can recombine and annihilate each other, one that may be slightly closer to the black hole will be sucked in, while the other that is slightly farther away escapes as heat. This release does not connect in any obvious way to the states of matter and energy that were earlier sucked into that black hole and therefore violates a law of quantum physics stipulating that all events must be traceable to previous events. New theories may be needed to explain this problem.
Question 10
Are there additional dimensions?
Wondering about the real nature of gravity leads eventually to wondering whether there are more than the four dimensions we can easily observe. To get to that place, we might first wonder if nature is, in fact, schizophrenic: Should we accept that there are two kinds of forces that operate over two different scales-gravity for big scales like galaxies, the other three forces for the tiny world of atoms? Poppycock, say unified theory proponents-there must be a way to connect the three atomic-scale forces with gravity. Maybe, but it won't be easy. In the first place, gravity is odd. Einstein's general theory of relativity says gravity isn't so much a force as it is an inherent property of space and time. Accordingly, Earth orbits the sun not because it is attracted by gravity but because it has been caught in a big dimple in space-time caused by the sun and spins around inside this dimple like a fast-moving marble caught in a large bowl. Second, gravity, as far as we have been able to detect, is a continuous phenomenon, whereas all the other forces of nature come in discrete packets.

All this leads us to the string theorists and their explanation for gravity, which includes other dimensions. The original string-theory model of the universe combines gravity with the other three forces in a complex 11-dimensional world. In that world-our world-seven of the dimensions are wrapped up on themselves in unimaginably small regions that escape our notice. One way to get your mind around these extra dimensions is to visualize a single strand of a spiderweb. To the naked eye, the filament appears to be one dimensional, but at high magnification it resolves into an object with considerable width, breadth, and depth. String theorists argue that we can't see extra dimensions because we lack instruments powerful enough to resolve them.

We may never see these extra dimensions directly, but we may be able to detect evidence of their existence with the instruments of astronomers and particle physicists.
Question 11
How did the universe begin?
If all four forces of nature are really a single force that takes on different complexions at temperatures below several million degrees, then the unimaginably hot and dense universe that existed at the Big Bang must have been a place where distinctions between gravity, strong force, particles, and antiparticles had no meaning. Einstein's theories of matter and space-time, which depend upon more familiar benchmarks, cannot explain what caused the hot primordial pinpoint of the universe to inflate into the universe we see today. We don't even know why the universe is full of matter. According to current physics ideas, energy in the early universe should have produced an equal mix of matter and antimatter, which would later annihilate each other. Some mysterious and very helpful mechanism tipped the scales in favor of matter, leaving enough to produce galaxies full of stars.

Fortunately, the primordial universe left behind a few clues. One is the cosmic microwave background radiation, the afterglow of the Big Bang. For several decades now, that weak radiation measured the same wherever astronomers looked at the edges of the universe. Astronomers believed such uniformity meant that the Big Bang commenced with an inflation of space-time that unfolded faster than the speed of light.

More recent careful observation, however, shows that the cosmic background radiation is not perfectly uniform. There are minuscule variations from one small patch of space to another that are randomly distributed. Could random quantum fluctuations in the density of the early universe have left this fingerprint? Very possibly, says Michael Turner, chairman of the astrophysics department at the University of Chicago and chairman of the committee that came up with these 11 questions. Turner and many other cosmologists now believe the lumps of the universe-vast stretches of void punctuated by galaxies and galactic clusters-are probably vastly magnified versions of quantum fluctuations of the original, subatomic-size universe.

And that is just the sort of marriage of the infinite and the infinitesimal that has particle physicists cozying up to astronomers these days, and why all 11 of these mysteries might soon be explained by one idea.

How Did We Get Here?

Astronomers cannot see all the way back in time to the origin of the universe, but by drawing on lots of clues and theory, they can imagine how everything began.

Their model starts with the entire universe as a very hot dot, much smaller than the diameter of an atom. The dot began to expand faster than the speed of light, an expansion called the Big Bang. Cosmologists are still arguing about the exact mechanism that may have set this event in motion. From there on out, however, they are in remarkable agreement about what happened. As the baby universe expanded, it cooled the various forms of matter and antimatter it contained, such as quarks and leptons, along with their antimatter twins, antiquarks and antileptons. These particles promptly smashed into and annihilated one another, leaving behind a small residue of matter and a lot of energy. The universe continued to cool down until the few quarks that survived could latch together into protons and neutrons, which in turn formed the nuclei of hydrogen, helium, deuterium, and lithium. For 300,000 years, this soup stayed too hot for electrons to bind to the nuclei and form complete atoms. But once temperatures dropped enough, the same hydrogen, helium, deuterium, and lithium atoms that are around today formed, ready to start a long journey into becoming dust, planets, stars, galaxies, and lawyers.

Gravity-the weakest of the forces but the only one that acts cumulatively across long distances-gradually took control, gathering gas and dust into massive globs that collapsed in on themselves until fusion reactions were ignited and the first stars were born. At much larger scales, gravity pulled together huge regions of denser-than-average gas. These evolved into clusters of galaxies, each one brimming with billions of stars.

Over the eons fusion reactions inside stars transformed hydrogen and helium into other atomic nuclei, including carbon, the basis for all life on Earth.

The most massive stars sometimes exploded in energetic supernovas that produced even heavier elements, up to and including iron. Where the heaviest elements, such as uranium and lead, came from still remains something of a mystery.
-E. H.

The Particle Data Group of Lawrence Berkeley National Laboratory has an excellent particle physics primer: particleadventure.org/particleadventure/index.html.

Read the full National Research Council report on the 11 biggest questions: www.nationalacademies.org/bpa/reports/cpu/index.html.

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The 11 Greatest Unanswered Questions of Physics

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Are protons unstable? In case you're worried that the protons you're made of will disintegrate, transforming you into a puddle of elementary particles and free energy, don't sweat it. Various observations and experiments show that protons must be stable for at least a billion trillion trillion years.