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Mon March 17, 2014
Is That Someone's House? What Astronauts Can See Looking Down
Originally published on Wed March 5, 2014 11:41 am
It's nighttime. You are hovering high off the planet looking down. Things are happening. Strange, beautiful, wonderful things.
For example, as night falls in the new world, North America seems stage-lit, it's so bright with street lights, traffic lights, window lights. South America has bigger patches of dark and seems quieter. But then, as you zero in on air traffic, planes start to move.
A string of planes pulls away from the North American East Coast as if being sipped through a straw; they head for Europe. They're overnight flights to London, Paris, Frankfurt — cities which, at that hour, 11 p.m. (EST), you can't see on our map. Everybody's asleep over there. But wait a beat, and with morning Europe turns incandescent; every patch of Britain, France, Italy suddenly buzzes with airplanes.
Wait another beat and America fills in, first on the East Coast (you can see the seashore, etched by waking aircraft); then there are planes everywhere, our national silhouette emerges. In Australia, planes stay mostly east. The middle of Australia stays inky dark. No planes there. Siberia's dark. Central Africa's dark. But there are surprises. Every night Argentina sends an arrow of light across the Atlantic to Spain. There are mysterious patches of light in the Pacific off Korea. So many puzzles, waiting to be explained.
Take a look. This video compresses a day on Earth — starting at 8 p.m. (EST) — into a little more than a minute:
That's a global view. Now let's burrow down for the spicy details. In 2002 or 2003, American astronaut Don Pettit figured out a way to snap still images of nighttime cities, even as the International Space Station was moving at about 17,500 miles per hour. He (and other astronauts) then took high-resolution pictures that show that, from a distance of 250 miles or so, you can still see single highways at night, like this one below, connecting Jiddah, Saudi Arabia (on the left) with Mecca (on the right). Millions of pilgrims travel this road during the Hajj each year. It's roughly 10 lanes wide, five in each direction — not that broad, but dazzlingly well lit.
The brightest spot on Earth, Pettit guesses, is in Las Vegas, the famous "Strip'" — with lights so strong, astronauts could make out specific beams of green, blue and red (which you can see here).
What about single homes? Any of them visible from space? Well, I know of one that pops out because it's unlit. Take a look at this nighttime picture of Tokyo:
Looking down from space, Tokyo glows blue-green. That's because street lights in Japan are gas discharge lamps that use vaporized mercury to produce light. Blue-green is mercury's color. So cities up and down Japan twinkle blue-green.
But the cool thing is, smack-dab in the center of Tokyo, alongside a string of bright, bright lights, you'll see a curiously empty spot (if you don't, hit the "revealed" tab below the picture, and we'll highlight it for you). That's a single residence, the palace of Japan's Emperor Akihito and his family. The royals don't want to live in a blaze of light, nobody would. So their home (basically a large, protected park downtown) is darker than everything around it — which is what makes it one of the rare personal properties visible from outer space.
What's Old? What's New?
You can learn a lot from streetlights. Sao Paolo, Brazil, for example, glows blue-green too, but mainly in one part of town. That's the older section, built when mercury vapor lights were in vogue. These days, city planners are moving to sodium vapor, which glows slightly orange, so from outer space the colors tell you which part of town is new, and which old.
There are other ways to spot newness. Older cities have zigzag streets, souks, slums, crazy-quilt patterns, oddly shaped parks. Newer places are more regular. Denver, for example, has a seriously rectilinear, boxy-looking street pattern that aligns due north/south and east/west. You can almost feel someone designing it.
But what designed this? The top of this segmented image is the southern tip of South Korea — it's where Korea meets the sea. The lights at the bottom are part of Japan. In between is ocean. No land, so what are those strange little dots in the middle? Those little specks of light that seem to be gathered in flocks?
They are fishing boats, says Pettit. I checked and discovered that the fishing fleets shine powerful xenon lights onto the ocean surface to attract squid. While those lights are aimed downward, they reflect upward — way, way, upward — 250 miles high. Which makes squid fishing perhaps the most conspicuous form of food gathering in the world.
Ah, the things you learn in the dark — looking down.
Astronaut Don Pettit spent more than 176 days in space. He lived aboard the International Space Station for 5½ months in 2002 and 2003, and later prepared and narrated a video of city shots from space, which he calls "a world tour." You can watch it here.