#10 - What Drives Evolution?
What Drives Evolution? You've heard it before: Natural selection is accepted by scientists as the main engine driving the array of organisms and their complex features. It is one of the most well tested theories in science.
But is evolution via natural selection the only explanation for complex organisms?
"I think one of the greatest mysteries in biology at the moment is whether natural selection is the only process capable of generating organismal complexity," said Massimo Pigliucci of the Department of Ecology and Evolution at Stony Brook University in New York, "or whether there are other properties of matter that also come into play. I suspect the latter will turn out to be true."
#9 - What Happens Inside an Earthquake?
We were surprised this one made the initial list, then surprised again when it got voted into the Top 10 by you. But it is odd that we don't know what's going on right here on our home planet, right under our feet.
Experts can explain exactly where a quake started and what type of fault is involved and maybe even predict how long aftershocks will last. But they are quite unsure of what happens inside the planet during a quake. The nature and behavior of the forces that keep faults from moving and then suddenly fail are still unknown.
"The problem of frictional sliding in earthquakes is one of the most fundamental problems in all of Earth science," said Caltech geophysicist Tom Heaton. "It has been a 30-year mystery story of figuring out the basic physics of the earthquake problem."
#8 - Who Are You?
The nature of consciousness has long baffled psychologists and cognitive scientists. Part of the answer, however, is surprisingly simple: Most of what drives what we do is embedded in neural networks not readily accessible by conscious thought, said Joseph LeDoux, a neuroscientist at New York University.
"The intuitive everyday idea about the sense of self and its control over behavior is as incorrect as the idea that the earth is flat," Morsella agreed. Although we think of ourselves as independent agents, we're not. Everything we do is influenced by unconscious processes and our environment, he added.
The leap to figuring out how we make conscious decisions, and what gives us each a mind of our own and a soul, well ... only No.
#7 - How Did Life Arise on Earth?
We expected this to be voted higher. But some votes for No. 2 on the list might have been split from this one.
Early evidence for simple, microbial life on Earth dates back more than 3 billion years. How it arose, nobody knows. Ideas range from chemical reactions around seafloor heat vents to reactions in rock.
"Many theories of the origin of life have been proposed, but since it's hard to prove or disprove them, no fully accepted theory exists," said Diana Northup, a cave biologist at the University of New Mexico.
#6 - How Does the Brain Work?
Some readers argued that we have a good handle on this. Well, sure, a lot more is known than was the case just a few decades ago. But with billions of neurons, each with thousands of connections, this is a tough nut to crack.
"We all think we understand the brain--at least our own--through our experiences. But our own subjective experience is a very poor guide to how the brain works," said Scott Huettel of the Center for Cognitive Neuroscience at Duke University.
Among the enigmas: "We do not yet have a good way to study how groups of neurons form functional networks when we learn, remember, or do anything else, including seeing, hearing moving, loving," said said Norman Weinberger, a neuroscientist at the University of California, Irvine. "If we understand the brain, we will understand both its capacities and its limits for thought, emotions, reasoning, love and every other aspect of human life."
#5 - Where is the Rest of the Universe?
It stinks when try to study something and most of it isn't there. So it is with the universe.
"I call it the dark side of the universe," said Michael Turner, a cosmologist at the University of Chicago, referring to the great mysteries of dark matter and dark energy.
In fact, only 4 percent of the matter and energy in the universe has been found. The other 96 percent remains elusive, but scientists are looking in the farthest reaches of space and deepest depths of Earth to solve the two dark riddles.
#4 - What Causes Gravity?
You'd think this down-to-earth concept would be well understood. Heck, Newton figured it out long ago, right?
Nope. Gravity is the weakest of all known forces in the universe, and the standard mode of physics does not explain how it works. Theorists think it might involve tiny, massless particles called gravitons that emanate gravitational fields.
"Gravity is completely different from the other forces described by the standard model," said Mark Jackson, a theoretical physicist at Fermilab in Illinois. "When you do some calculations about small gravitational interactions, you get stupid answers. The math simply doesn't work."
#3 - Is There a Theory of Everything?
Only a smart bunch of readers would vote this up so high. This stuff is really, really complex. Here goes the short version:
Physicists have a good "standard model" that carves the known universe into particles to describe everything from magnetism to what atoms are made of and how they remain stable. The standard model views particles as infinitesimal points, some of which carry basic forces.
Two glaring problems with the standard model: It fails to include gravity, and it becomes gibberish at high energies.
If a theory can be designed (some say it'll never happen) to withstand the incredible energies of the early universe as well as incorporate gravity, then a universal theory of physics could become a reality, researchers figure.
#2 - Does Alien Life Exist?
Life is everywhere. At least on this planet. So it's logical to assume it might be everywhere in the universe, too. But so far we've only thoroughly examined one world, so the sample size is a bit small.
We know now that the ingredients for life are widely distributed. And we know there are solar systems strikingly like ours our there. "We are here, made of stardust. Therefore, it is at least possible that there are others," said Jill Tarter, director of the Center for SETI Research in California.
And there ought to be some smart life out there, too. "Mankind has achieved scientific-technological civilization only in the last 200 years or so, out of about 4.5 billion years of life on Earth," said Frank Wilczek, a Nobel-Prize winning physicist at MIT. "So it seems we ought to expect there to be many scientific-technological civilizations that have had many millions, or even billions, of years to develop."
#1 - How Did the Universe Begin?
Yes, the clear winner in our minds, and in your votes. Simply put: "All other mysteries lie downstream of this question," said Ann Druyan, the author and widow of astronomer Carl Sagan. "It matters to me because I am human and do not like not knowing."
Yes, theory holds that it all started with the Big Bang 13.7 billion years ago, with everything starting in a space smaller than the period at the end of this sentence. In the blink of an eye, it all grew to cosmic scales in by a process called inflation. Problem is, while this predicts a lot of what's seen today, it can't be directly tested.
"Inflation is an extremely powerful theory, and yet we still have no idea what caused inflation--or whether it is even the correct theory, although it works extremely well," said Eric Agol, an astrophysicist at the University of Washington.