Gaze at the Aurora Borealis: Never mind the grizzly bears, the glaciers and the tundra. The best reason to go north (to Alaska, the Yukon or anywhere else above about 60 degrees latitude) is to see the Northern Lights. Try to imagine the most colorful, textured sunset you've ever seen, then send it swirling and pulsing across an otherwise clear and starry sky. Maybe add some faint outlines of mountains on the horizon and a hooting gray owl for ambience. But even more fabulous, in its own way, is the physics. Your planet is being buffeted by solar wind—particles of protons and electrons that the sun spews into space. Some of the charged particles get sucked into the earth's magnetic field and flow toward the pole until they collide with our atmosphere. Then, voilà: the aurora borealis (or aurora australis, if you happen to be at the bottom of the Southern Hemisphere).