Quantum particles exist and don't exist. Space is likely a moldable fabric. Dark matter is invisible, yet it binds the entire universe. And our universe, created from an explosion 13.8 billion years ago, is infinitely expanding into something. Or, maybe nothing.
Unless you're a trained physicist, at least one of those statements probably hurts your brain.
We experience a sort of cognitive dissonance when attempting to comprehend the vastness of such unimaginable, complex concepts. But theoretical physicists think about, and even conjure, these ideas all day, every day.
How do they do it?
According to new research, published Monday in the journal npj Science of Learning, physicists' brains grapple with counterintuitive theories by automatically categorizing things as either "measurable" or "immeasurable."
"Most of the things we encounter every day, like a rock, a lake, a flower, you can say, 'Well it's about the size of my fist... but the concepts that physicists think about don't have that property," said Marcel Just, a psychologist at Carnegie Mellon University and first author of the study.
To study exactly how physicists' brains work, Just and fellow researchers gave 10 Carnegie Mellon physics faculty members -- with differing specialties and language backgrounds -- a ledger of physics concepts. Then, they used fMRI (functional magnetic resonance imaging) scans to examine the subjects' brain activity as the individuals went down the list.
In contrast to normal MRIs, which help with anatomical studies, functional MRIs can detect brain activity based on fluctuations in blood flow, glucose and oxygen.
Turns out, each physicist's brain organizes concepts within the field into two groups. The researchers were just left to figure out how to label each group.
"I looked at the list, and said well, 'What do concepts like potential energy, torque, acceleration, wavelength, frequency ... have in common? At the other end of the same scale, there are things like dark matter; duality; cosmology; multiverse," explained co-author Reinhard A. Schumacher, a particle physicist at Carnegie Mellon University.
The average person might lump Schumacher's descriptions on the latter end of the spectrum as mind-bending and inexplicable, but the most important connecting factor, he realized, is that they're immeasurable.
In the brain scans, these concepts didn't indicate activity of what he calls "extent," loosely referring to placing tangible restrictions on something.
Physicists' brains, the team concluded, automatically discern between abstract items, like quantum physics, and comprehensible, measurable items like velocity and frequency.
Basically, the stuff that provokes a sense of perplexity in us non-physicists doesn't elicit thoughts of "extent" for them. That's probably why they can think about those things with relative ease, whereas we begin worrying about scale.
Physicists' powers come from brain evolution
Speaking from experience, Schumacher says considering abstract physics ideas as a student can be very different from conceiving them as a longtime physicist.
"I think there's a sense that as physicists grow older, the concepts kind of crystallize in the mind, and you end up using them in a more efficient way," Schumacher said.
"The more you use these ideas, the more they become like old friends."
The brain scans also support that assertion. Not only did the team test faculty brain activity, they also looked at physics students' brains.
"In the old physicists who have been doing it for years," Schumacher said, "it's like the brain is more efficient. It doesn't have to light up as much, because you're going right for the thing right away."
Additionally, Just noted the professors "had more right hemisphere activation, suggesting that they had a greater number of sort of distantly associated concepts."
While a physics student might relate velocity to acceleration, it seems the professors were relating velocity to much more niche subjects activated by remote locations of the brain. Velocity of the universe's expansion, perhaps?
Accommodating new ideas isn't just for physicists
Just emphasizes how evolution of the brain to accommodate new, abstract ideas happens to all of us. Perhaps only theoretical physicists can easily comprehend duality or a multiverse, but people working in other fields, of course, ponder complex ideas of their own.
Chemists, for instance, have to visualize unseen orbital structures of atoms and bond configurations only drawn in textbooks. And the general public, over time, has adapted to inventions like iPhones and the cloud. Think about it. We can comprehend the cloud, which is pretty bizarre.
Imagine traveling back in time to the 1700s and explaining to someone the workings of an invisible data storage mine. They'd probably feel the way we do when we picture the quantum domain -- we'd be the "physicists" to them.
"We have this understanding now," explained Schumacher. "Even if you develop some new scientific concept, we can more or less predict what the brain is going to do with it."
For instance, during the exercise, when asked to think about oscillations, Just said some subject's brains activated sections relating to rhythmic activity. The organ had basically repurposed areas used in ancient times for general rhythms, like maybe music, to allow for modern physics concepts.
"The idea of sine waves is just a couple hundred years old," Just said. "But people have been looking at ripples on a pond forever."
Just also suggests it could become possible to actively help the brain repurpose itself, harnessing its ability to adapt. If we allow children to expand their minds through education by introducing abstract concepts sooner and more rigorously, he says, maybe one day they can readily imagine things the way scientists do.
Even further down the road, he says the findings could inform studies of mental health -- how does the brain's organizational and adaptation capabilities operate while in distress?
"I think it's the most fascinating question in the world," Just remarked. "'What is the essence of human brains? How can we make them healthier; think better?"