AP - A tiny speck of zircon crystal that is barely visible to the eye is believed to be the oldest known piece of Earth at about 4.4 billion years old. For the first time ever, the public will have a chance to see the particle Saturday at the University of Wisconsin-Madison, where researchers in 2001 made the breakthrough discovery that the early Earth was much cooler than previously believed based on analysis of the crystal.{br}{br}View the Entire Article{br}