** Watch Radiation up close

****Cost:** $30

Time: 10 Minutes
Safe | | | | |

You can pick up a spinthariscope for $30 from Or make your own with a zinc sulfide screen ($10 on eBay) and commonly available radioactive items.

  1. Hold an antistatic brush behind the screen [left]. It sends out alpha radiation strong enough to produce a visible glow.
  2. Look at vintage orange Fiestaware plates in a totally dark room with a magnifying glass to see flashes one at a time.

In 1903 there was nothing to watch on TV because there was no TV, and meeting girls was no easier than it is today. But one device solved both problems . . . sort of.

The Crookes spinthariscope, invented that year, is a small tube with a lens at one end and a zinc sulfide screen at the other. Just above the screen is a tiny speck of radium mounted on a needle. If you look into one, you’ll witness a seething, swirling light show of individual atoms going out in a blaze of glory (more entertaining than most things on TV today, I’d say). Each decaying radium atom sends out a high-energy alpha particle, which slams into zinc sulfide crystals. This triggers a process that eventually releases photons, creating visible flashes.

These atoms are so small, it would take the energy from four trillion of them to raise the temperature of a teaspoon of water by one degree. The fact that you can see the flash from a single atom decaying is nothing short of amazing. Your eyes must be totally dark-adapted, which means sitting in a pitch-black room for at least 10 minutes. If you were a dashing young man of science in 1903 and you brought one of these scopes to a dinner party, you would have been rude not to invite the ladies to sit next to you in a dark room. This might account for some of the early popularity of the device.

In 1947 you could get a Lone Ranger Atomic Bomb spinthariscope ring for 15 cents and a Kix cereal box top; the same toy recently cost me $200 on eBay. But modern spinthariscopes (made with safe radioactive ores) are available, and they really do work-provided, of course, that you sit in a dark room for 10 minutes first. Do with that opportunity what you will.

A THOUSAND POINTS OF LIGHT: A Mathematica-generated computer simulation of what you see inside a spinthariscope. The phenomenon is so faint, it´s nearly impossible to photograph.

For more Gray Matter, click here.

ACHTUNG! Theodore Gray is trained in lab safety. Don’t try this at home. Visit for more on Gray’s scientific pursuits.