I stood on the bridge
in the late afternoon sunshine. It was close to high tide. Looking west, the river seemed disturbed, rippling with small waves and turbulence, a ceaseless pattern of dark shapes and brightly lit crests.
But when I looked east, the same river seemed becalmed, almost glassy in its stillness.
It was several minutes before I understood. Looking west, I could see the wave-shadows thrown by the low sun; but when I looked east, the shadows were invisible. West, the small surface movements were exaggerated; east, they were flattened into nothingness.
I recalled a visit to Loch Ness. The Loch is long and thin, running SSW to NNE. It is banked on both sides by sharp hills. The prevailing wind comes from the south west, and echoes and bounces along the valley, creating longitudinal waves on the surface of the Loch, waves that come and go, appear and disappear, occasionally joining with other waves in long tendrils that look remarkably like... like a Loch Ness monster.
How easily our eyes are tricked! More accurately - how easily our minds are tricked. Our eyes simply detect: our minds do all the work. And the work is: safety or danger? Eat or run? Millions upon millions of years of evolution, the pattern recognition systems in our brains the ever-more-sophisticated difference between survival and death.
They must - surely! - be pretty good at their job. Every day I avoid collisions with dangerous objects. Every day for millenia my forebears did the same.
And yet - they are unreliable. I looked one way and the way was smooth. I looked the other and it was choppy. I looked across a narrow lake and saw the back of an immense aquatic sauropod.
So how do I know what to believe? How many of my perceptions are, in fact, illusions? And, in turn, how many of the things I think are simply erroneous? Perhaps most importantly: how would I tell the difference?
I think it's time to go. I could be wrong, of course, but I leave the bridge all the same.
But when I looked east, the same river seemed becalmed, almost glassy in its stillness.
It was several minutes before I understood. Looking west, I could see the wave-shadows thrown by the low sun; but when I looked east, the shadows were invisible. West, the small surface movements were exaggerated; east, they were flattened into nothingness.
I recalled a visit to Loch Ness. The Loch is long and thin, running SSW to NNE. It is banked on both sides by sharp hills. The prevailing wind comes from the south west, and echoes and bounces along the valley, creating longitudinal waves on the surface of the Loch, waves that come and go, appear and disappear, occasionally joining with other waves in long tendrils that look remarkably like... like a Loch Ness monster.
How easily our eyes are tricked! More accurately - how easily our minds are tricked. Our eyes simply detect: our minds do all the work. And the work is: safety or danger? Eat or run? Millions upon millions of years of evolution, the pattern recognition systems in our brains the ever-more-sophisticated difference between survival and death.
They must - surely! - be pretty good at their job. Every day I avoid collisions with dangerous objects. Every day for millenia my forebears did the same.
And yet - they are unreliable. I looked one way and the way was smooth. I looked the other and it was choppy. I looked across a narrow lake and saw the back of an immense aquatic sauropod.
So how do I know what to believe? How many of my perceptions are, in fact, illusions? And, in turn, how many of the things I think are simply erroneous? Perhaps most importantly: how would I tell the difference?
I think it's time to go. I could be wrong, of course, but I leave the bridge all the same.
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