I know that happened to me with mathematics. All through grade school, and even into college, I found math to be one of my easiest subjects. I never had to struggle to understand it, and got high grades without honestly trying all that hard.
Then I hit Calculus 3.
I use the word "hit" deliberately, because it felt like running into a brick wall. I think the problem was that this was the point where I stopped being able to visualize what was going on, and without that concrete sense of why things worked the way they did, it turned into memorization and application of a set of what appeared to be randomly-applied rules, a technique that only worked when I remembered them accurately. I lost the intuitiveness of my earlier experience. It returned to some extent when I took Differential Equations (partly due to a stupendous teacher), but I went from there to Vector Calculus, and it was all over.
That was the moment I decided that I am a Bear Of Very Little Brain, and the effect of the experience (combined with a similar unfortunate roadblock in Classical Mechanics) convinced me that a career as a physicist was not in the cards.
That feeling came back to me full-force when I ran across a paper in the journal Physical Review D entitled "Dark Energy from Topology Change Induced by Microscopic Gauss-Bonnet Wormholes," by Stylianos A. Tsilioukas, Emmanuel N. Saridakis, and Charalampos Tzerefos, of the University of Thessaly. Even reading the abstract left me with an expression rather like the one my puppy has when I try to explain a concept to him that is simply beyond his comprehension, like why he shouldn't eat my gym socks. You can tell he's trying to understand, he clearly wants to understand, but it's just not getting through.
But as far as the paper goes, at least I can tell that the idea is really cool, so I'm going to attempt to tell you about it. If there are any physics boffins in the studio audience who want to correct my misapprehensions or misstatements, please feel free to let me know in the comments.
About seventy percent of the mass/energy content of the universe is something called dark energy. (It's entirely unrelated to dark matter; the potential confusion between the two has led to a push to rename it vacuum energy.) Dark energy is a bit of a placeholder name anyhow, given that we don't really know what it is; all we see is its effect, which is the measured increasing expansion rate of the universe.
The current best guess about its nature is that dark energy is a property of space itself (i.e., not something that space contains, but an inherent characteristic of the fabric of spacetime). This energy manifests as a repulsive force, but because it's intrinsic, it doesn't dilute as space expands, the way a cloud might dissipate into air; its content per unit volume remains constant, so as space expands, the total amount of dark energy in the universe increases, resulting in a steady acceleration of the expansion rate. At the moment, at least on the local level, gravity is still stronger than the expansion, so we're safe enough; but eventually (we're talking a long way in the future) space will have expanded so much that dark energy will overwhelm all other forces, and matter itself will be torn to shreds.
But despite this, we still have no idea what causes it, or even what it really is.
The Tsilioukas et al. paper -- once again, as far as I can understand it -- proposes a solution to that.
On the smallest scales, spacetime seems to be a "quantum foam" -- a roiling, bubbling ferment of virtual particles and antiparticles, constantly being created and destroyed. That these virtual particles are real has been demonstrated experimentally, despite their existing for such a short time that most physicists would question even using the word "existing" as a descriptor. So these incredibly quick fluctuations in spacetime -- even in a complete vacuum -- can have a discernible effect despite the fact that detecting the particles themselves is theoretically impossible.
What Tsilikouas et al. suggest is that there's a feature of the quantum foam that, described mathematically, is basically a network of tiny wormholes -- tunnels through spacetime connecting two separate points. They're (1) as quick to appear and vanish as the aforementioned virtual particles, and (2) extremely submicroscopic, so don't get your hopes up about visiting Deep Space Nine any time soon.
The mathematics of these wormholes is described by a principle from topology called the Gauss-Bonnet theorem, named after mathematicians Carl Friederich Gauss and Pierre Ossian Bonnet (no relation), and when you include a Gauss-Bonnet term in the equations of General Relativity, you get something that seems to act just like the observed effects of dark energy.
So the runaway expansion of the universe might be due to tiny wormholes forming from the quantum foam of the vacuum -- and those minuscule fluctuations in spacetime add up to seventy percent of the total mass/energy content of the universe.
Like I said, it's not like I'm any more qualified to analyze whether they're on to something than Jethro is to explain why chewing up my gym socks makes him a Very Bad Puppy. And it must be said that these theoretical models sometimes run into the sad truth from Thomas Henry Huxley, that "the great tragedy of science is the slaying of a beautiful hypothesis by an ugly fact."
But given that up till now, dark energy has been nothing more than a mysterious, undetectable, unanalyzable something that nevertheless outweighs all other kinds of matter and energy put together -- a rather embarrassing situation for physicists to find themselves in -- the new explanation seems to be a significant step in the right direction.
At least to a Bear Of Very Little Brain.
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