Some elements are common. Some elements are glamorous or dangerous. And then there are some elements with great PR. Krypton is one of those. When it's not the home planet of the man of steel, krypton has — or rather had — a very specific use.
Ah, pity the poor element krypton. It's totally overshadowed by its fictional counterpart. Though, to be fair, the element isn't exactly trying to call attention to itself. It's a colorless, odorless, tasteless, inert gas. It has a few uses. It is in the flashbulbs of cameras, since it can take the sudden intense heat. It's in fluorescent light bulbs, too. But that's hardly glamorous.
No, krypton's one shining moment of scientific relevance came when people were trying pin down the length of a meter. As science has gotten both more precise and multigenerational, the need to ensure that today's meter is the same as the meter a hundred years ago or a thousand years from now has become more and more intense. Both practically and ideologically, people had to come up with constants in order to measure the meter. For a while, it was a fraction of the distance between the north pole and the equator for a certain line of longitude. That wasn't even close to accurate enough. Template meters were made. Helpful, but not eternal.
At around this time, lasers were coming on the scene, and good old krypton, with its imperturbable inertness, was a good gaseous medium to put in them. They emitted a specific wavelength of light, and when scientists watched the lasers cross the lab and hit targets with wonderful accuracy, they finally believed they had found something eternal enough. The wavelength of a specific isotope of krypton, Krypton-86, would define the meter. Earth and krypton were linked, as the meter was established as 1,650,763.73 times the 605.78 wavelength of light emitted by Krypton-86.
Alas, the tribute was not to last. Eventually scientists decided that an even better constant was the speed of light. The meter is no longer being more closely defined. It's a set fraction of the speed of light, and the speed of light is being revised to greater and greater degrees of accuracy.
And to think, the meter was almost superheroically poetic.
Image: Images of Elements