Wednesday, July 29, 2009

Skipping Stones


As a Christian who also happens to be a physics professor, I often encounter religious people who are antagonistic toward science and scientists who are antagonistic toward religion. This always saddens me a bit, as this conflict doesn't seem at all necessary to me. This short story expresses some of my thoughts on the subject.

Skipping Stones

One day, many years ago, he had obtained perfection, and since then he had not stopped failing to reclaim it. Everything had been just so – the wind, the surface of the water, the stone – and he had squeezed out of that moment all that it could give. With two-dozen skips, the stone had crossed the pond. Now he was lucky if he could get four before it sank. It was always so close though. Maybe if the stone had been slightly smoother, if his finger had not stuck and made it tilt in that funny way, or if he had just flung it with a little more force.

It was this seeming attainability of perfection that made skipping stones so therapeutic. After every failure he was sure he knew exactly what needed to be done to make the next throw perfect so that his ultimate goal was perpetually just seconds away. Perhaps this goal was a frivolous one, but a frivolous goal was better than an unobtainable one or, worse, a nonexistent one.

This was in every way different from his day at work, which he was trying to forget. Eight hours of his life had been spent debugging a program that he was not even sure was the one to blame for the problem. By the time he had retreated to his car to face an hour of stand-still traffic, he had made no measurable progress. Even if he had, it would have been of little consolation to him as his project involved ten other programmers and he had only the vaguest understanding of its overall purpose.

Why did he subject himself to this mundane work? So he could have money to pay for food and shelter. He needed these to live. And what did he do with this life for which he toiled so hard? He spent most of it working at a mundane job that brought him no pleasure.

What if he had a more fulfilling career? What if he was curing incurable diseases, or bringing peace to lands where war had reigned for centuries? The best he could hope for was to preserve the lives of others who were simply living to preserve their own lives. There was no way to break the cycle. Life must be preserved for life's sake, but no one seemed to have a clear idea why.

Perhaps that was why men had invented God. It was comforting to think that there was some purpose to life, even if no one living it was clear as to what it was. That did not matter, as long as some divine power out there knew. But science had proven that God was nothing more than an invention. How could one claim the universe was guided by some omnipotent will when every particle in it was blindly following a systematic set of physical laws? There could be no purpose in that. Sure, all those laws were not yet fully understood, but everything indicated that they existed. Maybe even in his lifetime some genius would write down those magical equations that governed every action that had ever taken place and every action that would ever be. Where was the divine will in that?

As he skipped another stone his mind drifted away from these dark thoughts to his college physics class. He thought about how his body converted chemical energy into the energy of motion, causing first his arm to move and then the stone. As the stone flew through the air it imparted some of its energy to the air molecules, causing them to scatter in random directions. Likewise, each impact with the water caused even more of its energy to dissipate until it no longer had enough to carry on forward. Then it would sink, continuing to send water molecules flying away and losing ever more energy in the process. Whatever energy was left as it reached the pond's floor would be lost to the mud. The disordered swirlings of air and water currents would be all that was left of the once well-ordered energy that had been stored in his body.

Another lecture from that class suddenly came to mind. He recalled a talk on the symmetries of the universe – in particular that the laws of physics were the same whether time ran forward or backward. Well there was some minor exception, something involving the weak force, but that had no relevance to everyday interactions. So if someone were to film him skipping those stones and play it back in reverse, what would he see?

A stone, stuck in the mud beneath the pond's surface, would spontaneously dislodge itself and shoot upward through the water. Picking up speed as it traveled, it would finally shoot into the air and skip back across the water and into his hand. How could that not violate the laws of physics?

What was happening on a molecular level? At first there would be nothing strange – the stone would be sitting on the pond's floor and the molecules in the mud would be vibrating randomly as always. Except now their vibrations would not be completely random. At some instant, by some extraordinary coincidence, they would all push upward on the stone at the same time. Likewise, as the stone started moving upward, the random currents of the water would somehow conspire to all push up on the stone until it was flung back into the air. It would skip back across the pond, but unlike in the forward-time scenario, it would gain energy with each bounce. Ripples would spontaneously coalesce from the pond's smooth surface and converge on the stone, accelerating it onward. Finally, it would fly up into his hand, causing the muscles in his arm and the ambient heat to work together in just such a way to trigger chemical reactions that would store energy in his body for future use.

This series of events would be impossibly improbable, and yet at no instant would any law of physics be violated. Each individual molecule would be blindly following those laws with no greater purpose in mind, and yet they would all be working together to bring order from chaos.


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