Comparing the mass and luminosity of the Sun to those of other stars, it appears that the Solar System cannot be much older than those rocks.
Calcium-aluminium-rich inclusions—the oldest known solid constituents within meteorites that are formed within the Solar System—are 4.567 billion years old, giving an age for the Solar System and an upper limit for the age of Earth.
Some isotopes have very long half-lives, measured in billions or even trillions of years.
Others have extremely short half-lives, measured in tenths or hundredths of a second.
For teaching and sharing purposes, readers are advised to supplement these historic articles with more up-to-date ones suggested in the Related Articles and Further Reading below.It is hypothesised that the accretion of Earth began soon after the formation of the calcium-aluminium-rich inclusions and the meteorites.Because the exact amount of time this accretion process took is not yet known, and the predictions from different accretion models range from a few million up to about 100 million years, the exact age of Earth is difficult to determine.Since 1955 the estimate for the age of the Earth has been based on the assumption that certain meteorite lead isotope ratios are equivalent to the primordial lead isotope ratios on Earth.In 1972 this assumption was shown to be highly questionable.I found several good sources, but none that seemed both complete enough to stand alone and simple enough for a nongeologist to understand them.Thus this essay, which is my attempt at producing such a source.Despite this, the momentum gained in the two decades prior to 1972 has made 4.5 b.y.a popularly accepted “universal constant” even though the foundations on which it was based have been virtually removed.They then gather the radioactive, or M side up M&Ms, put them back in the container, and then pour them out again. and continue this process until all M&Ms are stable, or M side down.During each trial, students record the number of radioactive parent isotopes and record this in a data table.