Re: But but...
Awww crap I'm gonna bite (wish me luck folks).
Since I've done radiodating of geological samples I might be speaking with a small amount of (slightly hung over) authority, or I could be part of the evil cabal of earth scientists who are hoping to become infinitely rich by telling people the world is really, really, really old (and very cool - apart from the hot bits obviously).
The age of the Earth isn't solely derived from U->Pb dating (although that was the first method tried). The relative volatility of lead is a real problem with older samples which are likely to have been metamorphosed since original crystallisation. Instead the range of dates for the formation of the Earth is based on various dating methods including Pb -> Pb, Sm -> Nd, Rb -> Sr and Re -> Os, all of which come in around 4.51 - 4.68 Gya with a typical range of +/- 0.15Gy.
Pb -> Pb dates are referenced against a geochron which was taken from meteoritic dates of IIRC three stony meteorites of different compositions and two iron meteorites. If you want detail look up the Holmes-Houtermans method for Pb -> Pb dating. Basic chemistry tells us that the iron-nickel troilite alloy of iron meteorites is depleted in uranium so it will not contain radiogenic lead derived from uranium decay. So the ratios of lead isotopes in iron meteorites are those of the primeval solar system.
C-14 in diamonds? If you're talking about the Baumgardner and RATE work, it has been heavily criticised for not following proper procedures in handling carbon isotopes. Anomalous radiocarbon readings are occasionally found in studies of carbonates, but the fact the vast majority of geological samples do not show radiocarbon forces us to conclude that the problem is either with instrumentation or with the way samples are prepared for analysis.
Ocean salinity? Really? Seriously? You're still using that one. Look Edmond Halley didn't know how evaporite deposits form or how widespread they are. T. Mellard Reade, John Joly and George Becker didn't know about plate tectonics - they didn't know that ocean waters (containing salt) are in intimate contact with magma at mid-ocean ridges; that a volume of water equivalent to the entire ocean passes through the oceanic crust every 10 million years; or that salt water is subducted into the Mantle in ocean plates and sediments.
In short, a lot of science has happened.