However, they assumed that the Sun was only glowing from the heat of its gravitational contraction.
The process of solar nuclear fusion was not yet known to science.
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.
It is also difficult to determine the exact age of the oldest rocks on Earth, exposed at the surface, as they are aggregates of minerals of possibly different ages.
material and is consistent with the radiometric ages of the oldest-known terrestrial and lunar samples.