The man who moved Mt Sinai

By subjecting the Bible to the academic rigour that has made him one of the UK's leading materials scientists, Colin Humphreys replotted the route of Exodus. He tells Harriet Swain what happens when science meets religion.

He was watching dawn break on Mount Sinai, surrounded by tourists singing hymns, when Colin Humphreys asked the simple question that began his epic quest. This was the highlight of a nine-day package tour to Petra and the Sinai peninsula, but Humphreys began to wonder why they were there. "I looked around me and thought, 'why this mountain?'," he says.

Not that Humphreys, a committed Christian, is averse to hymn singing. But as professor of materials science at the University of Cambridge, he is used to asking questions and finding solutions. For him, the discovery that Mount Sinai was not a strikingly isolated peak posed a problem. Moreover, it was surrounded by land so barren that it was hard to imagine how the thousands of Israelites led out of Egypt by Moses could have survived there for a year, as the Bible says. Humphreys could not leave this puzzle alone.

The result is The Miracles of Exodus, written for a popular audience in spare evenings and researched on holidays with his wife. It picks apart the mysteries of the Book of Exodus to provide scientific explanations for everything from the ten plagues and the parting of the Red Sea to the sudden appearance of manna, which kept the Israelites going on their journey to the holy mountain.

The Miracles of Exodus is an odd book. While its style, subject matter and insistence that the Old Testament text is "remarkably accurate and coherent" will appeal principally to Christian readers, its emphasis is on scientific explanation rather than faith. Indeed, Humphreys originally planned to write a series of academic articles rather than a popular book and deliberately tried to put his faith aside in writing it. This approach has already prompted some opposition from fundamentalists in the US, where the book is selling well. One radio interviewer felt that miracles were by definition not natural events and was scathing about Humphreys' suggestion that the first Egyptian plague involved the River Nile changing colour because of red algae rather than literally turning to blood.

Yet, at the same time, Humphreys has antagonised academics. He says that those who have read the book have been much more positive than those asked to comment without seeing it. But he can hardly be surprised that biblical scholars may find it irritating. "What I find really exciting is that if my findings and conclusions are correctI we will be overturning many of the beliefs of modern biblical scholarship," he writes.

He argues that the reason experts have so far got it wrong is that they have failed to look hard enough at the available evidence and are too willing to believe that the Bible is inaccurate. "I think biblical scholars have slipped up," he says, suggesting that their individual specialisms are too narrow to allow them to see the big picture or to question traditional translations and assumptions.

As a scientist, Humphreys has always chosen to take a broad view. He says that his original focus, X-ray refraction and electron microscopy, naturally offered opportunities to look into other areas. He then branched out into electronic materials, and his research now ranges from ultra-high-temperature alloys to electron and ion-beam lithography, including cutting grooves in silicon small enough to contain a single molecule of DNA.

Humphreys' latest big thing is the semiconductor gallium nitride, which has already led to the development of bulbs for traffic lights that will last ten years, rather than six months as at present. Lasers made from the material could soon be used to help detect early-stage cancer and allow entire music collections to be stored on a single disc. It could also make more powerful transistors to increase the range of mobile phones and could be a key component of the next generation of wireless computers and printers.

The idea of the "everlasting light bulb" has brought Humphreys much publicity, and as he talks about gallium nitride with fluency and enthusiasm it is easy to see why he has become so involved with promoting public understanding of science. This work began at Oxford with talks to schools and led eventually to his appointment as fellow of public understanding at the Institute of Physics.

"I think it is important to explain things to the public," he says.

"Writing this book is almost part of working on the public understanding of science because it is showing people that science is also useful in explaining what has happened in the past."

Much of his book is persuasive, including its key finding - that Mount Sinai is in Saudi Arabia, not the Sinai peninsula. He presents a cogently argued case, based not only on a redrawn route for the Exodus but also on the theory that the mountain of God must have been an active volcano. This, he suggests, explains the pillar of cloud that led the Israelites by day and pillar of fire by night. The claim is extremely sensitive, however - and not simply in terms of annoying biblical scholars and tourist managers.

Plans for a TV documentary exploring this idea have had to be dropped because the suggestion that the Israelites occupied Saudi Arabian soil proved too political.

But the book also offers scientific explanations of the ten plagues of Egypt. According to Humphreys, most of these plagues were linked. Algae turned the Nile the colour of blood and caused fish to die, which led to the plague of frogs seeking alternatives to their fish diet. The hailstorm that formed the seventh plague blew in the locusts, which laid eggs in the damp sandy soil, reducing food supplies and forcing families to feed their favoured first-born with what was left - damp, contaminated grain that killed them.

Some of Humphreys' explanations are more compelling than others. Natural gas from the ground or a volcanic vent may explain the burning bush, but could "wind setdown" really have forced the Red Sea back enough to allow the Israelites to cross without blowing them over? His efforts to explain, however, are rigorous, and his determination to offer solutions cannot be doubted.

It is not the first time Humphreys has turned his academic skills to religion. He had an article published in the science journal Nature on the date of the crucifixion, after discovering in his daughter's Ladybird book of "Great Men of History" that Jesus Christ was the only great man listed with question marks over his dates of birth and death. And he has continued to seek solutions to religious questions since childhood.

He was brought up in a Christian family, and his father, an engineer who tested ball bearings, was a creationist. As a schoolboy, he found creationist literature persuasive and recalls giving several biology teachers a hard time until he eventually decided that evolution was probably more likely. "Whether you are a scientist or not, you should first look for a natural mechanism," Humphreys says. "As a Christian, I believe that God is the overall creator, but I believe the universe probably started with a big bang, and I think God will work with the creation He has set up."

Nevertheless, when he started his physics degree at Imperial College London, he abandoned Christianity for about a year before eventually coming round to reading the gospels in a new light. Humphreys concluded that the whole thing was invented, or that Jesus was mad, or that the stories must be true. He believes there is a case to be made for the first two alternatives, and has great respect for scientists such as Richard Dawkins who vehemently deny the existence of God. But after weighing the arguments, he thinks the idea that the gospels are factual is the most plausible.

Moreover, while he is no fundamentalist and concedes that not every word of the Bible is scientifically true, "for the Bible to be true is pretty important".

For him, the most compelling argument for God's existence is the beauty of how the world works. "If you are working at a problem and come up with a solution that is very elegant, you almost know it's true. It is consistent with a creator that likes elegance."

He is already thinking about his next book, in which he will again turn a scientific eye to events in the Bible. This time it will be about the last week in the life of Jesus. "If you look at the gospel accounts, there are a number of contradictions that are pretty astonishing," he says. "I think I can sort it out."

The Miracles of Exodus will be published by Continuum Books on July 3 (£16.99).