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Editor's note: In Thursday's programme Melvyn Bragg and his guests discussed Comets. As always the programme is available to listen to online or to download and keep - AI.

Comet (In Our Time)


Happy New Year!  Most of mine was spent in Cumbria where it rained, and when it wasn't raining it was pouring, and when it wasn't pouring there was a blizzard.  And, of course, we had a terrific time!

Nothing better than storming around Buttermere or trying to get up Skiddaw when the wind is determined to push you backwards.

I learned a new word this morning: panspermia, which is the notion that life is everywhere in the Universe.  This pushes back the origin of life on Earth as being the origin of Life.  It was much embraced by those who wanted to push the origins of life back further and further, so it ended in a point which could be called God.  Certainly, when I made the intervention about Fred Hoyle I was thinking about that, although I was not thinking about God.  Nor, I think, did Hoyle, although he respected the best of religion.  I knew him and I remember him at one stage talking about extraordinary individuals who could not be analysed in terms of their earthly existence and they included Jesus Christ and Mozart.

There was a brisk discussion afterwards as to what there was out there which could be called life.  I was told there were not bacteria in space, but there were a great number of minerals in meteorites and therefore the argument would be: if there were minerals which could lead to physics, and heat which could lead to chemistry, and chemistry which could lead to biology, what would prevent there being life in the comets which hit this planet before it properly became this planet?  "What is life, then?" said Don and we moved on.

Yesterday I was doing some filming on William Tyndale in and around St Paul's Cathedral.  We walked up to St Paul's, unaware of the fact (were you?) that it was Plough Wednesday.  Outside St Paul's were some massive combine harvesters, painted in wonderfully bright nursery colours.  There were real sheep and real lambs and real geese and hens around too (and to plump out the numbers there were cardboard cutouts of cattle and hens and geese and ducks).  They didn't seem to be freezing as we were.  After filming a little outside St Paul's and then for longer than anybody intended on the Millennium Bridge where we practically froze to death, went back to do some evening shooting at St Paul’s and I walked straight into Choral Evensong in aid of the Addington Fund who were "bringing the countryside to the city".  To walk into St Paul's with that choir in full throat, at Evensong, on a winter evening, was quite extraordinary.

At present, busyness is all.  I'm coming to the end of the filming of Tyndale and beginning a film on the 'real' Mary Magdalene - starting with portraits in the National Gallery on Tuesday evening and then off to Israel at the end of next week for six or seven days.  There's so much to catch up on really, especially about the Culture series, but it'll have to wait because that's quite enough for Ingrid for today.

Best wishes

Melvyn Bragg


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  • Comment number 2. Posted by John Thompson

    on 20 Jan 2013 01:22

    Melvyn nearly fell into the creationist/Von Daniken theory of life’s origin not on our planet but in the universe.It came from outer space!This was knocked down as it rightly should be as lazy-minded thinking.Instead we got the more reasonable assumption that water and minerals came on the asteroids and comets in the early formation of the Solar System as some of the building blocks of life,which were joined to what was already here. We got some excellent scientific thinking from the gathered illumini.The analogy of the comets as the rubbish tip of the formation of the early Solar System,the discarded building material of the creation of the construction of the planets,was masterly and superb.Like Heidegger and Sartre comets and asteroids are closer to each other than 1st thought,icy rocks or rocky bits of ice. The mysteries of comets,where they come from,how they orbit,what they’re made of,how far they travel,how long they last,when they’ll come again,was all methodically covered.The brilliance of Halley’s prediction was a pivotal moment in man’s intellectual history.Between Mars and Jupiter we get the Asteroid Belt,an orbit of planetary rock than never became planets,though some have moons.

    The fact that man can discover more about the universe through non-manned space probes seems clear with things like STARDUST and DEEPSPACE 1 and the ROSETTA MISSION and the Voyager explorations. Since comets contain materials from the time when the Solar System was formed, comets are regarded by scientists as frozen time capsules, with the potential to reveal important information about the early history of our planet and others.The space satellites have found that some of the dust particles formed at very high temperatures and must have formed close to the Sun and some of this material formed close to the Sun must have been thrown outwards beyond the snowline.This got amalgamated with the ice that formed the comets.We learned of the turbulence of the whole disc that formed the planets. Comets are called 'dirty ice-balls', whereas asteroids, or minor planets, are ‘rocks in space’. The size of asteroids typically ranges from a metre to several hundred kilometres across. One of the main differences is that asteroids do not contain ‘volatiles’ (substances that ‘sublimate’ i.e. they pass directly from the solid to the gaseous state when heated) or other frozen material. Therefore asteroids do not develop a tail when they approach the Sun. The comet’s tail is due to the frozen gas vaporizing and dragging small dust grains with it into the surrounding space. In this way the comet’s atmosphere, the ‘coma’ is formed and evolves, and the ion and dust tails form. There is evidence that some asteroids are ‘dead comets’, comets that have lost their volatile materials after many approaches to the Sun.Comets come from the Oort Cloud at the edge of the Solar System,jarred into activity by the gravitational pull of the Solar System of our own Sun and other stars,which cause perturbations with the surrounding interstellar space, which may push comets into the inner part of the Solar System where they get captured by Jupiter.This produces the short-period comets(like Halley’s) that orbit more frequently. Jupiter can change the energy of an object,hence its orbit.

    We have a problem wondering where all the oceans come from on Earth.You don’t expect on rocky inner planets vast quantities of water,usually to be all boiled off by the Sun’s heat.The water on the Earth has got to have been added since.Comets are 80% water.Bombardment by comets is a source.Water is a volatile molecule and came later in the Earth’s formation history. Bombardment was more intense in the early Solar System.Only Earth of the inner planets has retained an atmosphere and has water.Hartley2 comet came from the Kuiper Belt.It has a different water chemistry than those with isotopes of heavy hydrogen(deuterium) from the Oort Cloud. Before the Late Heavy Bombardment the Earth was a barren rock.This may have been caused by the violent gravitational pull of Saturn and Jupiter.Afterwards Earth supported the oceans which became the source of life.However we still need to test this hypothesis as further satellite investigation using probes and lasers could show that comet water to be different than Earth water.Only by looking at the stuff of comets,the pristine materials unchanged by the Earth’s atmosphere, will we know the truth.Then we can look at how interstellar material came into the Solar nebula.

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  • Comment number 1. Posted by jbwhite

    on 18 Jan 2013 15:34

    See you are preparing a programme about the real Mary Magdalene. Hope you make a reference to the unreal Mary Magdalene whose sarcophagus is at St Maximin, in the Var, not far from Marseilles, and whose last refuge was in the nearby Ste Baume area, in a cave high up on Mt Pilon. There is a stream leading down from the cave, whose origins were her tears. Ste Baume was a celebrated pilgrimage place in the Middle Ages, and still is today. A stone on the climb up to the sanctuary notes that Henry II made a pilgrimage there (perhaps after the Becket episode). Here is the Wikipaedia reference to the St Maximin church: The founding tradition held that relics of Mary Magdalene were preserved here, and not at Vézelay,[2] and that she, her brother Lazarus, and Maximin, a 3rd-century martyr who was now added to earlier lists of the Seventy Disciples, fled the Holy Land by a miraculous boat with neither rudder nor sail[3] and landed at Saintes-Maries-de-la-Mer, in the Camargue near Arles. She then came to Marseille and converted the local people. Later in life, according to the founding legend, she retired to a cave in the Sainte-Baume mountains. She was buried in Saint-Maximin, which was not a place of pilgrimage in early times, though there is a Gallo-Roman crypt under the basilica. Sarcophagi are shown, of St Maximin, Ste. Marcelle, Ste. Suzanne and St. Sidoine (Sidonius) as well as the reliquary, which is said to hold the remains of Mary Magdalene. Good luck with your hunt!

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