We laugh. We blush. We kiss. But why? What, evolutionarily speaking, are the advantages of swapping germs with someone when a sloppy smackeroo is hardly integral to propagating the species? We travel on a smallish stone that orbits a yellow dwarf of a star on the edge of one of billions of galaxies in the universe. Where did all these galaxies come from? Our bodies and minds respond to the fake-out that happens when sugar pills are substituted for medicine. What makes the so-called placebo effect work?

Never mind the enduring mysteries surrounding cancer and other incurable diseases, or the enigma of the disappearing contents of your sock drawer. Scientists remain daunted by some of the most basic questions regarding human behavior, the cosmos, and the building blocks of life.

The list of what science doesn’t know is voluminous. Unraveling 14 billion years of natural history—the machinations of the universe, of cells, molecules, atoms, quarks, of why animals and humans do what they do—in the few short centuries that humanity has hashed out and honed the scientific method is a task that slogs along at its own cautious pace. Despite endless questioning, layer upon layer of observations, and long lab hours, science continues to be mocked by nature—or at least made to toss and turn at night. Here are six “problems” that have science stumped.

What makes up 95 percent of the universe?

The answer to the most basic of questions—what’s out there?—has been undergoing constant revision for millennia. Aristotle thought all could be explained by the quartet of earth, air, fire, and water. During the past century or two, various discoverers of the smallest of things—atoms, electrons, quarks, and other subatomic particles—posited that these tiny bits of matter made up each iota of the Great Beyond, and Earth, too.

It turns out that atoms and other particles we know and understand only make up about 5 percent of the whole shebang. Decades ago, astrophysicists who had attempted to “weigh” all the matter and energy in the universe knew that their calculations added up to an impossibly large figure, given that most of space is, well, space. How to explain it?

In 1998, an international team of researchers, including Harvard postdoc Adam Riess, now a Johns Hopkins professor of physics and astronomy, investigated the light emanating from exploding stars billions of years old. Riess found that those stars were racing away—a sign not only that the universe is expanding, as Edwin Hubble had posited in 1929, but that it is moving outward faster and faster all the time. The underlying cause impelling everything in the universe to accelerate apart is now called dark energy, a kind of antigravity that weightlessly takes up space.

“Dark energy could be nothing more than how much nothing weighs,” says Chuck Bennett, a professor of physics and astronomy at Johns Hopkins. It could also be the “cosmological constant,” a quantity put forth by Albert Einstein to serve as a counterweight to gravity. We now know that Einstein’s reasoning for introducing this alleged constant was wrong, but the cosmological constant, with a different value than Einstein’s, is the current favorite candidate for dark energy. We also know that dark energy accounts for about 74 percent of the universe.

Subsequent telescope studies led by Bennett that focused on cosmic microwave background radiation, remnants of light that date from the Big Bang, confirmed the existence of another “dark” entity that coyly suffuses the universe with strange bits of stuff. Called dark matter, it is unresponsive to light and radiation and not made of atoms. It accounts for about 21 percent of the universe’s energy density. Dark matter contains mass, which will lead to its being detected, measured more accurately, and characterized. Thousands of scientists, including a few dozen from Johns Hopkins, are smashing specks of matter together at unprecedented energies in a subterranean supercollider in Switzerland to see if they can create and detect dark matter. Others are trying to detect it as it passes through old mine shafts in Minnesota.

“We’ll see some amazing developments that help us explain dark matter, possibly in three to five years,” predicts Jonathan Bagger, vice provost for graduate and postdoctoral programs at Johns Hopkins and a professor of physics and astronomy. “The roof will blow off of science as we discover dark matter on Earth underground.”

But there’s still the infinite issue of what’s going on outside that roof. “We really don’t have much of a handle on dark energy,” concedes Bagger. Which means we still won’t know what constitutes about three-quarters of everything we “know.”

Why do we need sleep?

 

Ask anybody who has worked a double shift or spent the night cramming for an exam—a night without sleep is like a day without air. Humans crumble without eight or so hours of nightly shut-eye. When our sleep is regularly disrupted, we become much more sensitive to pain. Our organs and central nervous system become much less efficient. If we’re limited to four hours of sleep, our white blood cells create high levels of inflammation that lead to disease. If we log four hours of snooze time for each of six consecutive nights, we’ll develop insulin resistance, a condition that can lead to weight gain and, eventually, diabetes. Our mood suffers; only clinically depressed people improve their condition by sleeping less. It’s even worse for an insomniac rat, whose inability to maintain its immune system, metabolism, and body temperature proves fatal.

It’s nearly universal throughout zoology—all critters, save shrews and a few plants, need to sleep, hibernate, or otherwise shut down. But why?

Two prevailing theories argue that sleep either restores the energy we need to thrive, or it helps us adapt to threats. Both concepts turn on the idea that evolution made us sleep for a reason, which seems like a convenient fact to relay to your boss on the days you show up late. “Sleep leaves us vulnerable to predators in the wild. It’s a potentially dangerous state,” says Michael Smith, associate professor of psychiatry and behavioral medicine at Johns Hopkins. “So, evolutionarily, it had to serve important functions.”

Smith, who studies the link between sleep deprivation and pain, sees value in both theories. “It may be a fine-tuning system for the organism. It’s restorative,” he says. Some researchers testing that hypothesis search for a vital chemical or substance in the body that is either fully synthesized or broken down only during sleep. Others are looking for evidence that pathways in the brain could conceivably get the rest and recharging they need to fully function during the energy-consuming hours of the day.

But there’s evidence to counter that—and that’s where the adaptive theory comes into play. During rapid eye movement (REM) sleep, neurons in the brain fire as if we’re awake. The brain is far from rest, churning out the detailed dreams we tend to remember. Certain types of memories are stored and consolidated during REM sleep—it’s not for nothing, apparently, that we’re told we’ll make a better decision after sleeping on it. “REM might have something to do with wiring our nervous system when we’re very young, including when we’re fetuses,” adds Smith. All of which would help an emerging intelligent species adapt and survive better.

An adaptive mechanism aided by sleep could help make our brains better at learning and retaining things. But not everyone buys all of that. Having enough juice in the tank to make it through the next day might have more to do with it. “It may all come down to energy,” says Samer Hattar, an associate professor of biology at the Krieger School of Arts and Sciences. Hattar has studied sleep and circadian rhythms in various species for 18 years. “Whenever there is a limit on energy—the sun to make it and oxygen to fuel functions—animals tend to shut down. That fits with our ideas about circadian rhythms and why we developed them. It’s important to maximize the time when you can gather energy.” Bats, for example, sleep more than 20 hours a day, saving energy for the few hours of the day when the insects they feed on are out and about.

Hattar doesn’t believe the sleep-is-dangerous hype, either. Animals that aren’t moving are less likely to draw the attention of predators, he says. Sleep can be a form of hiding. “Sleep can be advantageous because when you don’t need to get energy, you can shut down and conserve what you have,” he says.

In addition to debating reasons for why we sleep, scientists still kick around how we regulate the amount of sleep we get and how the lack of it ties into the development of diseases. But science has only investigated sleep intensively for about 60 years—nowhere near long enough to figure out exactly why we spend one-third of our lives dead to the world.

http://magazine.jhu.edu/