Earlier this year, prompted by a few short talks on cosmology which I had given to his confirmation class, my parish priest asked me to preach a sermon. Although my university education was in mathematics and theology, Fr William always thinks of me as a physicist, and put me down to preach on Advent Sunday, on the subject of 'The Last Things'. It's an Advent tradition to spend the four sundays before Christmas preaching on The Four Last Things, namely heaven, hell, death, and judgement. But I was asked to preach on eschatology in physics, and so I have done my best to draw a topical theological point while talking about the heat death. The sermon, preached three weeks ago, was generally well-received. One member of the congregation cornered me privately and criticised my sermon for not according with the day's gospel. For reference, the day's readings were Isaiah 2:1-5, Psalm 122, Romans 13:11-14, and Matthew 24:36-44. Since putting this text in my Livejournal, I've had a few comments that I appear to have skimped on the laws of thermodynamics. I'll concede that I quite deliberately skim over a proper definition of entropy, and consequently appear to fudge conservation of energy somewhat. Given the time constraint, and the audience of non-scientists, something had to give, I'm afraid.

May I speak in the name of the Father, and of the Son, and of the Holy Spirit. Amen.

As some of you may know, I work with museums. Specifically, I maintain the official list of Accredited Museums, which spans the whole UK. Our museums hold a wide variety of remarkable artefacts. The Victoria and Albert Museum has up-to-the-minute fashions, such as Manolo Blahnik shoes. The British Museum, just the other end of Drury Lane from here, holds Sennacherib's Prism, an Assyrian account of the war with the Kingdom of Judah described in Isaiah 37. At some 2 500 years old, that's pretty ancient. The dinosaur skeletons at the Natural History Museum are older by far, about forty thousand times as old. But the oldest of all - as far as I know - is a rock, also in the Natural History Museum, from the oldest part of the earth's crust. At four billion years old, it's ten times as old as even the oldest dinosaurs. But the universe itself - outer space, if you will - is three or four times as old as that.

Ever since the moment misleadingly known as the Big Bang, the universe has been winding down like a great clock. If we think of the watch-spring as fully wound at the instant of the Big Bang, then the universe has been losing available energy ever since, just as the energy stored in the tension of the watch-spring is released as the watch runs down. In this process of winding down, the universe has given rise to everything we see - the sun and stars, rocks and dinosaurs, Sennacherib's Prism and Manolo Blahnik's shoes. But the development of all these things necessarily involves waste: along with their beautiful light, the stars lose heat into the void of space. Those dinosaur skeletons took sixty or more years of growth and effort to produce, and now the flesh they supported has vanished, eaten or rotted away in the depths of prehistory. The lost effort forms the tick and tock of our cosmic clock.

When the watch has run down, we cannot call back the energy that was contained in the spring. It has all gone into turning the hands, and as a by-product, making the tick-tock sound. Likewise, after two and a half millennia or more, all that Sennacherib and his host have to show for their efforts is that clay prism in the museum. The Assyrian cohorts, horses and riders, have all melted like snow. So too, no doubt, will Manolo Blahnik and all his works pass away - perhaps to the relief of back-pain experts. The action, and the energy, of all these past events are lost, and the same natural processes which brought those things into being will destroy them.

The sun and the earth are subject to these processes too, and as the cosmic clock ticks onward, their time will eventually run out. Some five billion years into the future, when all that we see now will be as old and long-gone as the world of that rock at the Natural History Museum is to us, the earth's story comes to an end. The sun, having lost so much heat that it cannot hold itself together, will bloat up and destroy the earth, before dying itself. At this point, the cosmic clock is still ticking regularly, and the natural laws will drive other stars and planets for a long time to come. But in the end, unimaginable aeons hence, all the stars will be burned out, and the spring will finally have wound down. All energy spent, the universe will settle into a sort of eternal cold soup. Without the universal flow of energy, time itself shall be no more.

This view of the universe is informed by modern physics. But the idea that creation is in a state of long-term decay was well-known to the biblical writers. 'All things come to an end,' says the Psalmist. Isaiah speaks of the people withering like grass. We hear this idea again in this morning's Advent Prose, referring to desolation and the frailty of the people, like dead leaves. Saint Paul tells us that 'Where there are prophets, they shall fail, and where there is knowledge, it will vanish.' But he goes on, as all these writers do, to speak of faith, hope, and love, the gifts of the Spirit. In the famous passage from Job we heard two weeks ago, which also speaks of the decay of physical things, Job says that 'though worms destroy this body, yet ... I shall see God.' Hope in the salvation of God overcomes decay, both in the Old and New Testaments. In the Hebrew scriptures, the perishability of earthly things is always contrasted with the eternal Law of the Most High. In the New Testament, this eternal nature is extended to the followers of Jesus, the fulfiller of the Law.

Rather than trying to defeat the decay of the world, we as Christians are encouraged to put away earthly things and look to heavenly and everlasting ones. The corruption of moth and rust is inevitable, but this should not concern us. Religious faith transcends time and space, reaching out to that which is not merely beyond, but utterly different to them. You cannot bottle faith, or put it in a museum case with the church vestments displayed as historical curiosities at the Victoria and Albert Museum. Acts of Christian love are an outpouring into the fragile world of God's eternal love for us. In Jesus, we see the perfect example of a life lived for others, and which although subject to mortality, is not defeated by it.

The universe will, as I have said, eventually slow down and stop. It's very far removed from the cataclysmic images, religious and secular, which we normally associated with the end of the world. But what about the last days spoken of in all today's readings? This is not a question of physics. Saint Augustine maintained that time began with the universe, with nothing 'before' the first moment. God's eternal existence is beyond, rather than merely beforehand. Physicist Stephen Hawking, in describing the Big Bang as the edge of the universe, similarly suggests that 'before' is meaningless. So too the day when all nations shall come to stand before God is not a future date, a superstitious Rapture, but a state of being. Paul describes how at the last trumpet, our corruptible natures must put on what is incorruptible. Salvation is to be transformed into something which this universe cannot sustain or comprehend. Ultimately, our hope must be to be with God and like God, beyond the corruptible universe, where time shall indeed be no more.

In this season of Advent, let us look not for the signs of doom and catastrophe which popular mythology associates with the coming day of God. Instead let us all try to find ways to show those around us the nature of the eternal, loving Lord, whose day is now and for ever. Amen.