At its heart theoretical physics deals with Big Questions, from black holes to quantum mechanics to the Big Bang. In a recent article on NPR, Marcelo Gleiser, a professor of physics and astronomy at Dartmouth College, presented his list of the top challenges faced by theoretical physicists today.
- Dark Energy: In 1998 astronomers discovered that the universe is expanding faster than expected. What’s causing this cosmic speed up? One answer is dark energy, which is estimated to make up about 70 percent of the universe.
- Dark Matter: There’s more to galaxies than meets the eye. Surrounding these celestial bodies is an unknown kind of matter—named dark matter—that isn’t made up of either electrons or protons. Scientists estimate that dark matter makes up about 25 percent of the universe (leaving 5 percent for ordinary matter).
- Quantum Mechanics: This branch of physics describes how atoms and subatomic particles act—often in very strange ways. At a mathematical level, quantum mechanics works well, but scientists don’t always know how to explain all that math in words and images that the rest of us can wrap our heads around.
- Gravity: Some physicists wonder if gravity still belongs in the same category as electromagnetism and the strong and weak nuclear forces, all of which work on “stuff” in the universe. Unlike those, gravity affects the fabric of spacetime itself, which puts it in a class of its own.
- Black Holes: Resulting from the collapse of large stars, black holes continue to puzzle physicists. Although gravity is thought to be infinitely strong at the core—known as a singularity—black holes still emit radiation. Physicists aren’t quite certain how this loss of information occurs and what it means for gravity and quantum mechanics.
While theoretical physicists ponder these grand cosmic problems, other scientists continue to study classical physics — anything from fluid mechanics to understanding why dragonflies fly so well. No doubt some people would prefer to leave this branch of physics in the past — favoring quantum weirdness and strange relativity phenomena — but at the non-cosmic scale of our everyday world of airplanes and buildings, classical physics still functions quite well and it is still utterly amazing. And when you look at the problems tackled by both classical and modern physicists, you can’t help but see it they way Einstein put it: “Contemplate the mystery of conscious life perpetuating itself through all eternity, to reflect upon the marvelous structure of the universe which we can dimly perceive, and to try humbly to comprehend even an infinitesimal part of the intelligence manifested in nature.”