What's the strongest force in the universe?
Some people will say gravity. But that would be wrong. Gravity, physicists say, is intrinsically puny and gets its overwhelming oomph only from the fact that everything, even energy, contributes to it. Which isn't much consolation, admittedly, when you drop, say, your trusty college edition of the complete annotated works of William Shakespeare on your foot.
An astronomer a few years back said that jealousy was the strongest force in the universe.
Now we're getting closer.
I'd like to convince you, at the possible cost of my reputation as a cold-eyed observer of cosmic affairs, that it is love.
I learned this from a squirrel, some years ago, when I was living up in New York's Hudson Valley. An Eastern gray squirrel, Sciurus carolinensis, to be precise. She was sitting on the corner of the roof in the rain, bedraggled and sopping wet, staring at me with holy fire in her little dark brown eyes.
This was on the third day of a siege of what had started as a nuisance and was now terror.
It had begun with an occasional scratching sound in the bedroom ceiling. Our first thought was mice in the crawl space running under the peak of the roof. But the only access was through vents at either end. Sure enough, when we went outside and looked up there was a hole in the vent. Some animal had chewed its way in.
It was the home of my girlfriend Catherine. She had built it only a few years before, slaving through the summers and weekends to do all the finish work with her own hands. She rightly felt violated.
We sent an SOS to her brother, who is a builder, and he came over with a 25-foot ladder, climbed up and announced that there was a nest of ripped-up fiberglass inside.
He nailed a new vent into place and went home.
And so we woke up the next day to the sound of chewing. The vent was just over the window and there was a squirrel spitting splinters as she tried to get in. We had nailed her babies inside.
We went out and threw stones at her. She retreated to a nearby tree and sat there squawking at us.
Maybe she will give up, we told ourselves, in a moment I'm still ashamed of.
She didn't. I went outside and stood in the rain looking up at the roof. The squirrel glared back down accusingly. I didn't have the heart to throw another stone at her.
"She's eating my house," Catherine said, giving me a look not unlike the squirrel's.
I slunk off and found a listing for animal trappers in the yellow pages. A tall guy I immediately nicknamed Daniel Boone showed up the next morning in a fur hat and knee-length boots. He climbed up the house with a long-handled net and quickly emerged with six baby squirrels. He set them in a trap in the woods near the house. They were spitting and growling.
He said, "Don't put your hand in," and went off for coffee.
As soon as he was gone, the mother emerged from the woods. She scurried up the ladder into the house and then back out even faster, and ran through the woods up and down trees looking for her babies, winding up in the trap amid a renewed chorus of squawking.
Daniel Boone came back and took them away, he said, to new home in the woods on the other side of the Hudson. I have no reason to doubt his word.
We had to replace some clapboards and nail wire over the vent to prevent a recurrence of the invasion, and that was the end of it, sort of.
That squirrel's glare still haunts me. Especially now that I'm a parent myself.
In October, David Gross, a newly minted Nobel Prize physicist, wondered if science would one day be able to measure the onset of consciousness in an infant.
He likened that shift to what physicists call a "phase change," a microscopic adjustment that makes a macroscopic difference, as when water freezes to ice, or the atoms in a magnet line up.
But I wonder if we could measure the onset of love. Surely that is a phase change, too, a physical shifting of the internal firmament.
Now you might say I have some nerve imputing feelings as ethereal and high-flown as love to a toothy spitting pile of fur and bone with a brain the size of a walnut _ rats with bushy tails, as squirrels are often called out in the unromantic countryside. Surely this is just another example of the egregious anthropomorphizing that makes us identify emotionally with animals, robots, the Mars rovers, our cars.
But tell me you've never been taken in by a smile. Human love, biochemists say, is a sort of oxytocin drunk, an addiction to the hormones our partners, real or desired, release in us.
We anthropomorphize ourselves, in other words. Why not a squirrel?
As far as I know, we are both testimony to the marvelous possibilities inherent in the assembly of myriads of atoms. Richard Feynman, the iconoclastic Caltech physicist, once said that if he could pass one piece of knowledge on to future generations, it would be that everything is made of atoms. He meant not to diminish "everything," but rather to ennoble and make us appreciate the talent of atoms.
In another twist on the subject of love and physics, three-quarters of a century ago, Erwin Schrodinger, an Austrian physicist, went off to a Swiss resort with a mysterious woman friend, and came back with an equation that describes matter as a wave spreading throughout all space. Schrodinger's equation is now the basis of quantum mechanics, which is the foundation of modern physics.
In principle, physicists like to say, Schrodinger's equation explains all of chemistry and thus all of life, including squirrels.
But when they say it, they mean it as a joke. The equation hasn't been solved except by numerical approximations for anything more complicated than a hydrogen atom _ one proton and one electron. As for life, Joel Cohen, a population biologist at Rockefeller University, wrote an essay in the online journal Public Library of Science Biology that entirely new realms of mathematics would be needed to cope with the complexity of the living world, but I think he's being optimistic.
As a glance at any morning's headlines will tell you, we understand next to nothing.
Or as the refrain to Albert Einstein's Dreams by Naked to the World put it:
Just because I'm Albert Einstein doesn't
mean I understand
The ever-expanding universe between a
woman and a man.
If I knew, or had half a clue, I'd be much
more famous than I am.
So I'm willing to believe in squirrel love. As for human love, I used to wonder if I had it in me to chew down a house. Until my wife, Nancy, and I adopted our daughter, Mira.
A baby sitter, whom we did not know well, disappeared with her for a few hours, and I rampaged through every store and playground on the Upper West Side only to have them show up back at the apartment on time wondering what all the fuss was about.
So now I know.