Bob Berman's Strange Universe: It wasn't there
March 2010: Gaining lessons and humility from astronomy's illusions.
January 25, 2010
|You know the old Hughes Mearns poem, "As I was going up the stair, I met a man who wasn't there ..."|
Astronomers study objects we assume are really there. But sometimes they're not. A few months ago we mentioned rainbows, which stirred some controversy. Are they there? Sort of. A rainbow is nothing but a group of light rays converging on your eyes. It has no solidity. It cannot cast a shadow.
But its colors are real, right? Well, colors are pulses of magnetism and electricity. By themselves they have no visual properties. When nobody's looking, neither Mars nor a rainbow has color. Rather, we animals respond to the invisible electromagnetic stimulation; our retinas and brains conjure the experience of spectral colors. They're not out there on their own.
Solids are the same. Our fingers perceive the push of electrical repulsive forces when we touch a stone. We regard it as solid because we can't penetrate the rock or see through it. But we never contact a solid. Rather, we feel energy fields.
Telescopes transport us beyond our local illusions to reveal new, larger ones. Is the Sun really a yellow star out there, as textbooks claim? Not at all. Astronauts report it's as white as snow. The lemony color we ground-dwellers perceive is merely some of its blue light scattered through our atmosphere to give us our blue sky. The remaining dominant colors, green and red, combine into yellow — an atmospheric artifact.
What about red giants? Are they red? Look at Betelgeuse. It's yellow-orange. Nobody has ever observed a red giant star that is actually red. And the low, enormous Moon: Is this "Moon illusion" caused by our atmosphere enlarging it, as many believe? Nope. Appearances notwithstanding, the Moon is measurably smaller when it's on the horizon because it's then farthest from you.
Wow, there goes a meteor across the sky — except you never saw it. Nobody can see something the size of an apple seed at a distance of 70 miles. What you really saw was the hot glowing air surrounding the particle.
Look at the beautiful Orion Nebula (M42) using SLOOH, which is a live, public way to see the true colors of deep space. (Disclosure: I'm involved with that online observatory.) Because SLOOH neither enhances nor fakes M42's colors, it's what astronauts would see if they could travel the 1,500 light-years and stare it in the face. Right? Not really.
The list of celestial sure-bets that weren't there is endless.
|A nebula that looks gray through a backyard telescope would appear the same in person. Reason: As you approach the gas cloud, it spreads out and diffuses so that the intensity per square degree barely budges. Your retina continues to employ its low-light, black-and-white vision. Galaxies and nebulae will never show their magazine colors to visitors. So are the colors there or not? Your call.|
Astronomers have a long history of imagining all sorts of things that weren't there. William Herschel, discoverer of Uranus, believed that beneath the Sun's supposed luminous clouds lies a protective layer. Below it, humanoid creatures frolic on the Sun's pastoral surface.
The brilliant Harlow Shapley spoke for many astronomers when he argued in 1920 that external galaxies do not exist. All those spirals, he insisted, are just small clouds of nearby gas.
Strange Neptune motion made scientists search for a massive Planet X for half a century. But Pluto, found later, wasn't it. Planet X was imaginary. Neptune's seeming irregularities were a mistake.
In 340 b.c., Heraclides said that our planet spins. The idea was dismissed for nearly 2,000 years. "If Earth rotated," idiots argued, "a person jumping up would land in a different spot."
The list of celestial sure-bets that weren't there is endless. Nineteenth-century astronomers declared nebulae to be made of an unearthly substance called nebulium. Ten generations of scientists insisted space is filled with ether. People envisioned Venus as a comfortable place. And until just a dozen years ago, every astronomer knew the universe's expansion was slowing down.
Nor is high IQ any armor against error. Aristotle called Earth the center of the universe. Newton believed in alchemy. Kepler in astrology. Einstein wrongly dismissed the spooky realities of particle entanglement. Hawking said time could travel backward, and then changed his mind as if to demonstrate the process.
As science grows at an awesome pace, some claim we'll soon find a "Theory of Everything." More likely, knowledge will advance in spurts and detours. Error and illusion will continue to be part of human experience. And our children will grow up to find that some of today's sacred certainties have vanished like the ether.