The beauty of Krypton 81 is that this decaying process takes a really long time, which is helpful when trying to figure out how old something is. Scientists can use carbon dating to date how old an artifact is by measuring how much of the isotope Carbon-14 (found in all humans) is left in it. Carbon-14 has a half-life of 5,730 years, meaning that by the time 5,730 years have passed, an object like a fallen tree or a bone will have half the Carbon-14 it started with. That's great for relatively recent things, but is only useful for a few tens of thousands of years. Krypton-81 on the other hand has a half-life of 229,000 years.