Dark Energy

Like most people, I don’t know a whole lot about physics. I took a physics course as an undergraduate, learned the material well enough to earn an A, and then promptly forgot pretty much everything. I remember a few basic principles. For instance, I remember that force = mass x acceleration and that the total amount of energy in a closed system remains constant over time. Pretty good for an English major, huh? Still, I’m disappointed that I didn’t work to retain more of what I’d learned because I find physics super fascinating, though maybe not for the same reasons that physicists find physics fascinating. I’m not drawn to physics so much because I want to understand the mechanics of the universe (although this is certainly intriguing) as because it is an especially rich source of metaphors.

A pretty commonplace example of what I’m talking about is entropy. The second law of thermodynamics states that thermal energy (i.e., heat) always flows from areas of higher temperature to areas of lower temperature. For example, when I add ice cubes to a cup of warm water, the warm water seeps into the ice cubes and causes them to melt. As this happens, the water molecules inside the ice cubes become less organized and begin to move around more freely. As I understand it, entropy describes this movement from order to chaos. Admittedly, this is probably grossly simplistic if not just plain old wrong. I am, after all, an English major. But anyway, my point is that entropy is often used metaphorically by people to explain why the kitchen is a mess two hours after they cleaned it or why their husband doesn’t look as appealing as he did ten years ago. Metaphorically speaking, entropy simply means that things fall apart.

Lately I’ve been tripping out about dark energy. Again, what I’m about to say is going to be at least rudimentary if not totally wrong, but this is my blog and I’ll be a schlemiel if I want to. In physics class, I learned that space is malleable and can be bent and warped by objects within it. For instance, the mass of our sun creates a dent in the space around it, which is what keeps the planets in our solar system in orbit. Basically, the earth is slowly falling into the sun. This is what we call gravity.

(FYI: This is where I’m probably going to really start messing things up)

For a long time, it seemed like the only kind of gravity at work in the universe was this “pulling” kind, which raised the question, what’s to keep the universe from collapsing in on itself? So Einstein did a whole bunch of fancy math and came up with something called the cosmological constant, which (I think) suggests that empty space contains just the right amount of energy to counteract the gravitational pull produced by all the matter in the universe. Anyhow, the end result of all this math was a static universe that neither expands nor contracts but remains the same size.

But then this guy named Hubble figured out that space is actually expanding outward. To make a long story short, this outward expansion was eventually attributed to a massive explosion, which later came to be known as the Big Bang. Before the Big Bang, all the energy in the universe was concentrated in a singularity of infinite density and infinite temperature. After the Big Bang, all of the stuff in the universe expanded outward rapidly, becoming significantly less dense and a lot less hot. The force of this explosion was sufficient to counteract the gravitational pull of the matter within the universe and keep it moving outward. According to this theory, one of two things would ultimately happen: either the gravitational pull produced by all the matter in the universe would eventually exceed the force of the explosion and the universe would contract back in on itself, or the universe would continue to expand until all the bodies were so far apart that they were no longer affected by one another’s gravitational pull. In this second version of events, the speed of the universe’s expansion would eventually slow down and the bodies within the universe would just kinda drift apart, getting colder and colder as they lost thermal energy.

But then, scientists figured out that the speed at which the universe is expanding is actually increasing. This doesn’t make any sense. Remember entropy? The force of an explosion – even a really, really big explosion – should actually decrease as energy is lost in waste heat. Unless more energy is added. So here’s where dark energy comes in. Apparently, Einstein once speculated that there was another, counterbalancing force in the universe – a push to counteract the pull of gravity – but he abandoned this idea because he couldn’t figure out what this force might be. Well now, around one hundred years later, physicists have decided this repelling force exists and they are calling it “dark energy.”

The fascinating thing about dark energy is that, as of yet, no one has actually observed it. It is, as Columbia professor Brian Greene describes it, “a diffuse, invisible energy permeating space.” So as far as I can tell, dark energy is just the name that physicists have given to a force they don’t yet understand but whose effects they’ve been able to measure and observe.

I really, really like this. And now that I’ve finished delivering my primitive and probably totally erroneous lesson on physics, I get to tell you why I like it so much. Yippee!

To begin with, the term “dark energy” is itself evocative. It bespeaks of mystery, the unknown, things that lie outside the ken of human understanding. And then the idea that something we cannot see or touch or even be sure actually exists is instrumental in determining both the shape and the fate of the universe is just fantastically beautiful. I like to think that, like the fabric of the universe, the fabric of our own lives is also shaped by something like dark energy. I’m not talking about Freudian subconscious type stuff here, although dark energy would probably work as a metaphor for this, too. I’m talking about things that never happened but that nevertheless help determine who we are and what we will become. Things like missed opportunities and unrealized possibilities. Forgotten dreams, absent fathers, undeclared loves, unborn children, roads not taken, things we wish we’d said but didn’t. Things that aren’t and that never were, but that still exert gravitational force and affect the space around and within us. Resentments and regrets and secret sorrows and suppressed fantasies. Things that motivate us to make decisions and act in ways that don’t make sense to other people because the impetuses for our decisions and behaviors can’t be seen by others.

To my mind, dark energy blurs the distinction between what is real and what is not. I like to believe that within and around and beneath what we think of as “empirical reality” are things that can’t be observed by even the highest-tech gadgetry. Things that remain apart from our understanding but are nevertheless part of our existence. A shadow world overlying our own world. This may be because I read too much fiction and have all sorts of escapist tendencies, but whatever. I really believe that sometimes we can only make sense of things by acknowledging the existence – or at least the possibility – of things that do not make sense.