With the Archbishop of Canterbury, Rowan Williams, providing one of the star turns on the first day of this year's Hay Festival, God was appropriately never far away from the opening talks in the Cambridge lecture series, either.

It shows that science and the Bible are not in conflict. We have actually used them to work hand in hand.

Professor Sir Colin Humphreys

At least, his son wasn't, as the increasingly popular University of Cambridge strand of talks - now in its third year - opened with Professor Sir Colin Humphreys' fascinating new analysis of the events of Holy Week, which conclude that Jesus' Last Supper was on the Wednesday, and not the Thursday before his death.

Humphreys' study has been the subject of much debate, not least on this website, since it was published in April. His talk at Hay, however, emphasised its truly polymathic nature, which takes into account matters astronomical, theological, historical and mathematical, as well as detailed working knowledge of the Bible. All this from a materials scientist who, as he confessed, is pretty busy with his day job. He has been plugging away at the Last Supper problem in the evenings and at weekends since the 1980s.

The discussion also demonstrated how critical the foundational part of the study is. Fusing Biblical records, historical evidence with astronomical calculations, Humphreys and his Oxford colleague, Graham Waddington, successfully identified the precise date and timing of the crucifixion, which they state took place at 3pm on Friday, 3 April, AD33. This research was originally and deliberately published in the journal Nature to widespread acclaim from an array of scientific reviewers.

The new study, published in the book The Mystery Of The Last Supper, addresses the contradiction of the Gospels regarding the timing of that momentous meal. The synoptic Gospels, Matthew, Mark and Luke, all state that this was a Passover meal but John says it was not. There are other problems too - the fact that the Wednesday of Holy Week is not mentioned in the Bible when every other day is, the fact that a logistically impossible series of events had to happen between a Thursday arrest and a Friday crucifixion, and the fact that the involvement of the Jewish court - the Sanhedrin - in this context, would have been illegal under Jewish law.

As is already well-documented, the solution is that Jesus was using a different calendar; not the standard Jewish calendar adopted during the Babylonian exile, but an earlier version used by Moses, which dated back to the Exodus in Egypt. Just some of the records Humphreys used to reach his verdict included ancient Chinese and Babylonian materials to calculate changes in the Earth's rotation, Egyptian calendrical information and the accounts left us by the Jewish historian Josephus. If he is correct, his analysis leaves the Gospels in remarkable agreement on the point on which they were supposed to be divided most. "It also shows that science and the Bible are not in conflict," Humphreys argues. "We have actually used them to work hand in hand."

From Jesus, the subject matter expanded to a consideration of creation itself - and indeed of the expanding universe, presented by Professor John Barrow from the Department of Applied Mathematics and Theoretical Physics. This mind-boggling romp through the history of what we think we might know about the universe started in 1915, when Einstein's new theory of gravity made it possible to describe what the universe might actually be like.

Ever since, scientists have been striving to take what Barrow appropriately calls a "God's eye view" of the history of everything. Each time a new solution to Einstein's equations is found, a new universe is essentially imagined. To early, brilliant, but comparatively monolithic theories about an exponentially expanding universe or universes infinite in volume with beginnings and ends, research in the 1930s added the possibility that the universe's expansion might slow down and then accelerate again.

An array of universes have since been proposed - included distorting, rotating, magnetic and turbulent versions. Scientists have also been able to look back to the Big Bang and the early, intensely hot universe that first emerged. The process of expansion appears to have taken place at consistent rates in every direction to an extraordinarily high degree of precision, but small irregularities appeared as the acceleration differed, and these, it is believed, are the origins of galaxies and the life within our own.

Alongside this they have built up a picture of a far more complex geography and history to the universe than previously thought. "The question did the universe have a beginning now has a much more nuanced answer," Barrow says. "Our bit did, but we can now theorise about a multiverse that need have had no beginning at all."

The modern picture of this complicated 13.7 billion year history can really therefore only be applied to the (in itself huge) area we occupy. From an apparent beginning, this expanded rather slowly before undergoing a surge of expansion, then decelerating and cooling. During this period stars and galaxies started to form, and acceleration then increased again preventing the further aggregation of galaxies.

All of this has been bothering scientists for a lot longer than since 1915, of course. Opening his discussion of "Five Books That Changed The World", historian of science Simon Mitton pointed out that astronomy began with the Mesopotamians. Not that any of them got a look in as far as his list of five critical books was concerned - instead the all-time countdown credited Ptolemy, Copernicus, Newton and, rather unfairly it might be argued, Galileo twice.

Mitton admitted that he needed longer than his allotted hour to enthuse adequately about Galileo's contribution to human knowledge. As it turns out, he needs the best part of one to talk about Ptolemy and Copernicus as well, with the result that Newton's chosen book, his Principia Mathematica suffered from a time shortage at the end. Still, this is a book festival, and most people are like that.

In fact, each of Mitton's texts was epic in its own right. Writing in AD 140, Ptolemy's ambition was not only to summarise the astronomical knowledge of the time, but to improve the mathematical measurements involved for the sake of future prediction. His Almagest contains 13 books and - contrary to popular belief that misconceptions about the planet's shape persisted until the early modern era - featured a "proof that the Earth is spherical". The final five chapters offered a geometrical model of the solar system. Ptolemy had a catalogue of 1,022 stars and gave 48 constellations their names in his systematic study of them. The Almagest became the standard textbook on astronomy until the 16th century.

The story of Copernicus, who bucked the trend by proposing a heliocentric model of our solar system, remains inspiring even today. Unlike everyone else on the list, he developed his theories without academic colleagues while working as a canon in a part of the Kingdom of Poland miles from any recognised centre of learning. His 1543 work, De Revolutionibus, in Mitton's view: "Truly marks the beginning of the scientific revolution. It was also incredibly daring, because people had said for centuries that the Earth could not be in motion, because we would all fall off."

Copernicus, contrary to popular belief, never got in trouble with the Church for his views on a heliocentric planetary system. Galileo, whose groundbreaking use of a telescope to observe the heavens began to endorse Copernican theory in about 1609, was famously a different story. World-changing book three was the first record of his findings, the "Starry Message" in which he was able to describe the Milky Way properly for the first time. This, he claimed, would among other things "free us from many wordy debates" by philosophers. His observations of Jupiter and its moons were even more exciting, confirming Copernican theory. This was what led to trouble.

By 1613, Galileo was on trial for promoting Copernicanism. His response was to agree not to do so, which he managed to keep up for two decades. In 1632, he finally gave in to temptation with his Dialogo, which thinly disguised his views in the form of a three-way discussion between himself and - who else - Ptolemy and Copernicus. Galileo was tried and sentenced to house arrest for the rest of his life. Despite Mitton's claims that he was a talented marketer of his work, you have to question his judgement.

And so to Newton - by which time there was only time to make the single most important point about the Principia beyond its laying out of a mathematical form of the law of gravity. This is the universal law of gravitation, which states that every object in the universe is gravitationally attracting every other object. "From Copernicus starting modern science, Newton took it to a point where it was understood the natural world had physical laws that were perceptible," Mitton said. His laws still provide the basis for flying spacecraft today.

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