Radioisotope decay rates are renowned for constancy under normal conditions, so this assumption appears reasonable.But two observations and two clues omitted from physics textbook discussions of radiodating show that these radioisotope “clocks” are broken.First, scientists have observed that radioactive isotope (radioisotope) decay rates do fluctuate, including Th-228, Rn-22, and Si-32.
The solar estimate was based on the idea that the energy supply for the solar radioactive flux is gravitational contraction.
These two independent and agreeing dating methods for of the age of two primary members of the solar system formed a strong case for the correctness of his answer within the scientific community.
As one answer to his critics, Kelvin produced a completely independent estimate -- this time for the age of the Sun.
His result was in close agreement with his estimate of the age of the earth.
Billions of years’ worth of uranium decay (at today’s rates) must have occurred within polonium’s lifetime of hundreds of days.
This could only occur if radiodecay was once much faster.
but nobody yet knows the exact cause of the acceleration.
Trapped helium and short-lived polonium radiohalos present in granite suggest that radiodecay rates were once much higher than they are today.
Finally in 1976, it was discovered that the earth is "really" 4.6 billion years old… The answer of 25 million years deduced by Kelvin was not received favorably by geologists.