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BEYOND THE SUSSET CLICHE

Seen any good sunsets lately?

Ken Sassen, a research professor in meteorology at the University of Utah, has been seeing a lot of them. But unlike me and you, he knows why."It's been a very dirty year," he explains, "a very dirty year. Mount Pinatubo erupted in the Philippines in 1991, shooting sulfur particles into the stratosphere. The winds then pushed the haze particles to the poles and all of a sudden, great sunsets for us!"

And a lot goes into a great sunset. The bright red ones, says Sassen, are because of the size of the particles in the air. The Earth's atmosphere can only support a certain size particle, so we get a lot of reds and yellows. The blue light gets filtered out along the way and the high clouds head for red.

"Actually, it's possible to get any color sunset you want," says Sassen. "It all depends on what stays suspended in the sky. On Earth, floating particles are the size to give us reds."

Could there be purple and lavender sunsets on other planets?

"Sure."

Green sunsets?

"Yes."

Chartreuse and pomegranate sunsets?

No comment.

Mars, being the "red planet" has red sunsets. But then Mars has red everything - from skies to river beds. Down here on Earth, however, we can take some special pride in our "designer red" variety. And Sassen says we can expect to be seeing more and better ones in the future.

"There are going to be more eruptions injecting ash into the stratosphere," says Sassen. "And with volcano ash, the horizon can often glow for a full hour after the sun itself has set."

And what about that old saying, "Red sails in morning, sailors take warning. Red sails at night, sailor's delight."

"It's just bull," Sassen says. "But it makes for interesting folklore."

One thing that isn't just folklore, however, is that the hot, toasty sunsets are going to make for a hotter, toastier earth. Scientists have used laser beams to study volcanic eruptions and sunsets and have found that all those brilliantly beautiful particles in the sky are probably going to warm the earth by about one degree.