yes, one carbon-14 atom isn't very old, however thousands of these atoms add up to thousands of years, and because eventually all carbon-14 atoms in an organism decay eventually, its only effective for defining ages less than about 60,000 years
another method is to measure the radioactivity of fossils, that decompose at a known rate (this known rate is referred to as a half life and varies among radioactive atoms) and the amount of radioactive atoms are left (carbon-14 is the most commonly measured atom and it's half life is 5730 years.)
it is, because certain planets have ice and there are far away exoplanets with similar conditions to earth, it just took billions of years for the earth to form, and in genesis we KNOW adam and eve are created alongside all other animals, as well as the earth, which would contradict the fact that there are fossils and rock formations millions of years old
