Kelvin was foremost among the small group of British scientists who helped to lay the foundations of modern physics. His work covered may areas of physics, and he was said to have more letters after his name than anyone else in the Commonwealth, since he received numerous honorary degrees from European Universities who recognized the value of his work. He was a very committed Christian, certainly more religious than the average for his era. Interestingly, his fellow physicists George Gabriel Stokes (1819-1903) and James Clerk Maxwell (1831-1879) were also men of deep Christian commitment, in an era when many were nominal, apathetic, or anti-Christian... Lord Kelvin was an Old Earth creationist, who estimated the Earth's age to be somewhere between 20 million and 100 million years, with an upper limit at 500 million years based on cooling rates (a low estimate due to his lack of knowledge about radiogenic heating).From: Raymond J. Seeger, "Kelvin, Humble Christian" in The Journal of the American Scientific Affiliation, 37 (June 1985): 99-101 (http://www.asa3.org/ASA/PSCF/1985/JASA6-85Seeger.html; viewed 26 September 2005):
[Source:] H. and T. Sharlin, Lord Kelvin, Dynamic Victorian (1995)
Although William Thomson (1824-1907) was born in Belfast, he became Scottish when his father James became Professor of Mathematics at the University of Glasgow...
Scotland was never in favor of godless education; it insisted that it be based on the Bible. Kelvin liked neither secularism nor denominationalism in schools. To be sure, he had been brought up in the established Church of Scotland. As an undergraduate at Cambridge he subscribed to the 39 Anglican Articles, and upon becoming a Glasgow Professor did so to the Church of Scotland. He attended the University Chapel regularly. At Largs he attended the Free Church, where the minister was the brother of his deeply religious first wife. He was, however, not a rigid Sabbatarian; nor was he wont to parade his religious views. Nevertheless, in his customary first lecture in the "Introductory Course of Natural Philosophy" he said, "We feel that the power of investigating the laws established by the Creator for maintaining the harmony and permanence of His works is the noblest privilege which He has granted to our intellectual state." He concluded: "As the depth of our insight into the wonderful works of God increases, the stronger are our feelings of awe and veneration in contemplating them and in endeavoring to approach their Author ... So will he [the earnest student] by his studies and successive acquirements be led through nature up to nature's God." In 1871 he ended his British Association presidential address: "Overpoweringly strong proofs of intelligent and benevolent design lie all around us and if ever perplexities, whether metaphysical or scientific, turn us away from them for a time, they come back upon us with irresistible force, showing to us our nature, the influence of free will, and teaching us that all living beings depend on one ever-acting Creator and Ruler" (in line with William Paley's "Natural Theology"). "His close study of the phenomena of nature, his constant discovery of new marvels, seemed to bring him near and nearer to God, and he could never understand anyone treating science with any other feeling than reverence." "The deeper he delved into Science and the more he studied its mysteries, the greater his veneration for the Maker of it all." "We only know God in His works, but we are forced by science to admit and to believe with absolute confidence in a Directive Power-in an influence other than physical, or dynamical, or electrical forces," he claimed.
Although he was a biological evolutionist, he was not a universal evolutionist; he saw life as a thing apart from the physical forces it controlled (and requiring in itself a creative act.) He concluded his 1897 address to the Victoria Institute, "We must pause, face to face with the mystery and miracle of the creation of living creatures." He believed that evolution per se could not explain the great mystery of nature and creation.
Kelvin accepted the Scottish antipathy to a godless education and their insistence upon instruction in the Bible. He reverenced the Bible and studied it diligently. From 1903 till his death he was President of Largs and Fairlie Auxiliary of the National Bible Society of Scotland. He always began his college lecture with prayer, viz., the Church of England third Collect for Grace. His favorite prayer was: "Lighten our darkness, we beseech thee, 0 Lord!"
Kelvin was a Christian, a follower of Christ, rather than a mere churchman, a contributor to a church. He never expressed disapproval of the Unitarianism of some of his nephews and nieces. His tolerance is further shown in his remarks about the death of the self-styled agnostic Thomas Henry Huxley in his annual report (1895) as President of the Royal Society: "If religion means strenuousness in doing right and trying to do right, who has earned the title of a religious man better than Huxley?"
In her book on Kelvin the Man (1925) Agnes Gardner King, daughter of his sister Elizabeth, concluded, "Kelvin had walked through life a humble Christian."