This age is determined using several methods, including:

* Radiometric dating of lunar samples: Scientists analyze the decay of radioactive isotopes in rocks brought back from the Moon by Apollo missions. This gives a very precise age for the lunar surface.

* Comparing the Moon's composition to meteorites: The Moon's composition is very similar to certain meteorites, which provides clues about its formation.

* Modeling the formation of the Moon: Scientists use computer simulations to understand how the Moon formed, and these models suggest an age consistent with the other evidence.

The age of the Moon is very close to the age of the Earth, which is estimated to be around 4.54 billion years old. This suggests that the Moon formed very early in the history of the solar system.