An analysis of changes to global ecosystems has revealed that almost nowhere is untouched by the influence of humanity, with ...

A few years later, in 1907, he reasoned that since he knew the rate at which uranium breaks down (its half-life), he could use ... ore -- and by extension, the earth's crust -- had existed.

The discovery of radioactivity allowed scientists to develop new methods of determining Earth's age ... understand the mechanism of radioactive half-life and how it helps determine age by ...

Look at this point on the graph in relation to the y-axis. You will see that the counts per minute have halved in two days. This means that it has a half-life of two days.