Edward Davis

After graduating in physics from the University of Birmingham and undertaking PhD research at the University of Reading, Professor Davis has held positions at the University of Illinois, the Xerox Corporation (USA), the Cavendish Laboratory Cambridge and the University of Leicester.  He currently holds the title of Distinguished Research Fellow in the Department of Materials Science and Metallurgy, University of Cambridge.

His research interests have been in solid-state physics, particularly semiconductors, amorphous materials and glasses.  In retirement, he has been investigating and lecturing on the work of the Victorian scientist and Nobel Laureate Lord Rayleigh, in addition to helping with the preservation of Rayleigh’s original laboratories around which he regularly conducts tours. 
Professor Davis has served as Chairman of the History of Physics Group of the Institute of Physics and is currently Chairman of an International Advisory Committee responsible for organising a series of conferences on the history of physics.  He has authored or co-authored 7 books and over 200 papers. He is Editor-in-Chief of the Philosophical Magazine – a physics journal first published in 1798.

Dating of the Earth

Early estimates of the age of the Earth were based on events recorded in the Old Testament on the assumption it was formed at the same time as the birth of Adam.  The age thus calculated, about 6,000 years, was not questioned until 1863 when William Thomson, later Lord Kelvin, calculated the time it would take for an initially molten Earth to cool to its present state.  Thomson’s best estimate, based on the measured temperature gradient below the Earth’s surface, was 20 million years.  Geologists were sceptical of this figure because it did not allow sufficient time for the known fossil record to have developed.  In 1904, Lord Rutherford, using a radioactive dating method, determined that a specimen of pitch blende was 700 million years old.  Although modern radioactive dating methods are very reliable and accurate, the problem is finding rocks on the Earth’s surface that have not been recycled over geological timescales.  Nevertheless, small undisturbed zircon crystals dating from 4.4 million years ago have been discovered and inferences from recycled sedimentary rocks place the age of the Earth as 4.56 billion years, which agrees with the dates of meteorites and rocks brought back from the moon.