A Daily Walk With DietPower
Walking is the best exercise for weight loss. And the things you see!
I found this gasoline rainbow on Judith Drive. I'm sure you've seen this phenomenon yourself, and if you're a curious person (I pray you are), you've probably wondered what causes it.
It's difficult to explain and usually involves diagrams, but I think I can make it clear in words.
if I'm wrong.) Once you understand it, other color phenomena will begin to make sense, too.
A few drops of gasoline fell on wet pavement. Since gasoline is lighter than water, the gasoline floated. Because gravity tried to pull all the gasoline to the same level, it spread out. It stopped spreading when the tightness of its skin finally balanced the force of gravity. The resulting film was incredibly thin, because gasoline is even waterier than water.
Nevertheless, the middle of the film was thicker than the edge, because the skin tightness kept the film mound-shaped by a few millionths of an inch. And that's why the film makes a rainbow.
(Pay attention, now. We're getting to the good part.)
Some of the light waves hitting the film pass through and bounce off the bottom, but when they come back out they are canceled by other waves arriving behind them. Whether a wave is canceled or not depends on its wavelength (color) and the thickness of the film. In the middle of the film pictured above, long red waves are canceled, letting the remaining short blue waves dominate. That's why the middle looks blue. Farther out, as the film grows thinner and thinner, shorter and shorter waves are canceled, letting longer and longer waves dominate. That's why the color gradually changes from blue to violet to red to orange as you travel toward the edge.
In short, a gasoline rainbow performs the same selective filtering of colors as a rainbow in the sky. The main differences are that the medium is gasoline instead of water and the colors are filtered by interference instead of bending.
And of course there's no pot of gold at the end.
There. That wasn't so bad, was it?
About this page: Precisely at noon each day, I step out of my office for a 3.5-mile walk around my Connecticut neighborhood. I carry a Panasonic Lumix DMC-TX5 pocket camera with a Leica 10x optical zoom lens. My object is to make an interesting photograph of at least one thing that is different that day. I post the results here, hoping they will inspire you and your friends to walk, too. —Terry Dunkle, DietPower founder and CEO.
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All My Yesterdays
Friday, May 1: The Duck and the Bashful Maiden
Thursday, April 30: A Poison Ivy Sandwich
Wednesday, April 29: The Very Picture of Spring
Tuesday, April 28: A Busy Bumblebee
Monday, April 27: Electric Pink
Sunday, April 26: Saturday Night Special
Saturday, April 25: An Old Oak Falls
Friday, April 24: How an Ant Sees a Daffodil
Thursday, April 23: The Nameless Brook
Wednesday, April 22: Weeding Time
Tuesday, April 21: Wet Apple Buds
Monday, April 20: Mr. Allen and the Crew Team
Sunday, April 19: Bloodroot II
Saturday, April 18: Green Jellybeans
Friday, April 17: Bloodroot
Thursday, April 16: Skunk Cabbage III
Wednesday, April 15: Find the Critter
Tuesday, April 14: Blessing of the Animals
Monday, April 13: The Crow Who Said "Wow!"
Sunday, April 12: A Quirky Church
Saturday, April 11: Self-Portrait in a Pothole
Friday, April 10: Easter flowers
Thursday, April 9: Dumb as a Squirrel
Wednesday, April 8: April Snow
Tuesday, April 7: Egg Trees, Connecticut Style
Monday, April 6: I Carry My Lunch
Sunday, April 5: A Tree in Spring
Saturday, April 4: Pigs with Drivers Licenses
Friday, April 3: Forsythia
Thursday, April 2: Skunk Cabbage II
Wednesday, April 1: Mystery of the Hanging Shoes
Tuesday, March 31: Downy Woodpecker
Monday, March 30: 300-Year-Old House
Sunday, March 29: The Broken Fence
Saturday, March 28: "You're Such a Delight"
Friday, March 27: Skunk Cabbage
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