Familiar to us as the black substance in charred wood, as diamonds, and the graphite in “lead” pencils, carbon comes in several forms, or isotopes.One rare form has atoms that are 14 times as heavy as hydrogen atoms: carbon-14, or C ratio gets smaller.
Another pertinent thing that's also ignored, minimized, or scoffed at are the numerous other scientific methods of dating the earth, solar system, and or universe that yield much younger ages than 500 million years (max). When a rock crystallises, the crystals of the minerals in the rock often enclose minute grains of other minerals which contain uranium and thorium.
This is an important topic, for evolutionists want the history of earth to span long ages in the hopes that this will make the origin and evolution of life more likely.
Yes, an understanding of dating methods is important, but we should keep in mind that whether or not these dating methods are accurate, really has no direct relation to whether evolution has ever occurred or could occur. Evolution can only occur by a sequence of, first, production of matter from nothing, or origin of matter.
So, we have a “clock” which starts ticking the moment something dies.
Obviously, this works only for things which were once living.