http://creation.com/trial-balloons-geochronology "A curious complication emerged in the late 1940s—the earth became twice as old as the universe. The age of the universe is another trial balloon—calculated from the Hubble constant, assuming the big-bang history. Edwin Hubble (1889–1953) had such standing that no-one seriously questioned his value for the constant. So the problem was blamed on radioactive dating. Some astronomers even suggested that the radioactive decay rate had changed with time. But the astronomers eventually gave in. In the 1950s new measurements of the Hubble constant made the universe safely older than the earth. Clearly, ages are not objective scientific measurements but based on assumptions and beliefs. . . . Clair Patterson (1922–1995) is the man credited with dating the currently accepted age of the earth. But there is an ironic twist. Patterson did not use earth rocks. He used meteorites! That’s because, by Patterson’s time, it was widely believed that the earth had accumulated from particles and rocks called ‘planetesimals’, and that meteorites were junk left over from the earth’s formation. The age Patterson calculated was 4.55 billion years, plus or minus 70 million years.He also produced a graph of the composition of lead from four meteorites and lead from modern ocean-floor sediment. Because the ocean-floor sample plotted on the same line as the meteorites, Patterson argued that they all formed from the same cosmic material. Prominent geologists, such as Arthur Holmes, were not happy. To use iron meteorites, they claimed, was wrong. How can we know that the earth and the meteorites formed at the same time? How can we know they are both from the same material? We can’t. Even so, the number Patterson calculated in 1956 is still accepted today and universally quoted. His trial balloon is still floating. Yet, as more ocean floor sediments have been analyzed, it has been found that they do not all fall on the straight line but plot all over the place. Furthermore, geologists are now saying the lead isotopes of the earth have been reset by the formation of the earth’s core, which means Patterson used the wrong history for the earth. In spite of these and other problems, long-age scientists are still happy to work with 4.55 billion years. Actually, any number between 3 billion and 7 billion years would probably be okay for them, so 4.55 billion is a happy choice—and it looks precise and authoritative. It is large enough for the geologists and small enough for the astronomers. Everyone has plenty of time to work with, so there is nothing to gain by changing the number."