Assertion 2.7: If the Earth were as old as science says, uranium decay would have put more helium in the atmosphere than we find.
Analysis:
The extra helium, like normal helium and hydrogen, is light enough to escape the atmosphere into space. Thus, helium quantities in the earth give no evidence at all for the age of the earth, and we must look elsewhere -- to sediment deposition rates or radiometric dating, for instance -- to establish that age. (Berra 1990:127)
References
Berra TM. 1990. Evolution and the Myth of Creation. Oxford: Oxford University Press.