why are lunar rocks used to determine the age of a earth.
They aren't. Lunar rocks are dated to figure out when the moon was molten and new. Same thing on Earth. Those tell us the age of the universe. Both indicate about 4-5 billion years old.
Lunar rocks are not used to determine the age of Earth. Instead, they are used to determine the age of the Moon. However, by studying the age of the Moon, scientists can gather important information about the history of our own planet.
The age of the Moon is estimated using a technique called radiometric dating, specifically using isotopes of the element uranium. Radiometric dating relies on the known decay rates of certain isotopes, which allows scientists to determine the age of a rock sample.
When rocks on the Moon formed, they contained certain amounts of uranium isotopes. Over time, some of these isotopes decay into other isotopes at a known rate. By measuring the ratio of parent isotopes (like uranium) to daughter isotopes (the decay products), scientists can calculate the amount of time that has passed since the rock solidified.
By studying lunar rocks brought back from the Apollo missions, scientists have estimated that the Moon is about 4.5 billion years old. This age provides important insights into the early history of our solar system, as the Moon is thought to have formed shortly after the birth of the Sun and the Earth.
In summary, lunar rocks are not used directly to determine the age of Earth, but rather to gain knowledge about the age of the Moon, which in turn helps scientists understand the age and formation of our own planet.