Many independent lines of scientific evidence show that the
Earth and Universe are billions of years old. Current
measurements yield an age of about 4.6 billion years for the
Earth and about 14 billion years for the Universe. How ages are
measured The age of the Earth is measured by studies of
radioactive elements. Radioactive elements are unstable and
"parent" atoms decay into other "daughter" elements at a steady
rate. For example, through a series of steps, atoms of uranium
decay into atoms of lead. By measuring the abundance of "parent"
and "daughter" atoms in rock samples and knowing the decay rate,
geologists can calculate the age of the rock. Using several
different sets of parent and daughter elements, geologists have
measured the age of a variety of rocks, including terrestrial
and lunar rocks as well as meteorites, which originate primarily
from asteroids. The results consistently indicate an age of
about 4.6 billion years for the Earth. The age of the Universe
is measured in several ways. One metho