I’ve gotta be driftin’ along

27/06/2014

All_together_now

[Posted  by Nigel's family.  The additional texts mentioned by Nigel below will be added in the next few days.  Please check back for these updates. If, Gentle Reader, you have a particular memory of Nigel to share, please comment on this post.]

… as Pete Seeger sang, in ‘So Long, It’s Been Good To Know You.’ Cancer experts have given me a short time to live. We all have to die of something, and I’ve had a particularly exciting life, so I’m not at all worried about it. What’s more, after 60 years together, my wife Lizzie and I have recently celebrated our Diamond Wedding, with our wonderful family pictured above, and even received a personal message from Queen Elizabeth.

Until today, this blog has been largely idle since 2012, when Lizzie had a stroke and I became her full-time carer. Apart from dealing with comments and warding off spam, I’ve added nothing since a post in April 2012 about Henrik Svensmark’s paper on supernovae and life. By the way, Lizzie did explanatory diagrams for that post.

Then I started writing a book based on Henrik’s paper, to be called Supernova! But lack of time has prevented me from finishing it, even though Lizzie is now much better.

So I’m going to start a new part of the blog, Would-be Books, containing what parts of the book already written, chapter by chapter as new posts. The plural comes about because, when Supernova!was finished, I meant to write another book called The Physics of Love. Now I hope to add at least an outline of that book too. We’ll see, anyway. Watch this space.

Meanwhile, to all of you who have read and commented on my blog, and still visit it daily, let me offer a big Thank-you.

My family will take over as webmasters to deal with incoming comments, obituaries, etc.

 


Memorial meeting: advance notice

26/09/2014

Nigel Calder

1931-2014

Memorial meeting

Royal Astronomical Society

Burlington House

Piccadilly

London W1J OBQ

Tuesday 2 December 2014 at 4pm

Followed by an informal reception 5-6pm

 

An hour-long programme of talks celebrating the life and work of the science writer Nigel Calder will take place on 2 December, which would have been Nigel’s 83rd birthday. Speakers are to be confirmed but will include his co-writer and friend Professor Henrik Svensmark.
Details of how to request a seat will be given here (http://calderup.wordpress.com) on 11 November.


Obituaries and other notices

28/06/2014

 


Newspaper announcements: Nigel Calder (1931-2014)

28/06/2014

CALDER, NIGEL DAVID RITCHIE, science writer, died peacefully at home on 25 June 2014, aged 82, after a wonderful life. Most beloved and devoted husband to his true love, Lizzie, for 60 years. Adored and brilliant dad to Sarah, Penny, Simon, Jonathan and Kate. Steadfast and loving father-in-law to Nick, Charlotte, Jacqui and Giuseppe. Proud and amused grandfather of Hannah, Nicholas, Robbie, Daisy, Poppy, David and Izzy.
Funeral Friday 4 July 2014 at 2pm at St Paul’s Methodist Church, Crawley RH10 8ER, all welcome, followed by a private cremation. Wearing of black not necessary. No flowers please; donations if desired to The Dystonia Society or RNLI, c/o The Martins Funeral Directors, Crawley RH11 9BA, 01293 552345 to whom all enquiries should be made.
Memorial gathering to be held later this year.

With minor variations, the above announcement will appear in The Times and The Telegraph, on Monday 30 June 2014.

 


A stellar revision of the story of life

24/04/2012

Climate Change: News and Comments and The Svensmark Hypothesis

Svensmark’s Cosmic Jackpot

Visible to the naked eye as the Seven Sisters, the Pleiades are the most famous of many surviving clusters of stars that formed together at the same time. The Pleiades were born during the time of the dinosaurs, and the most massive of the siblings would have exploded over a period of 40 million years. Their supernova remnants generated cosmic rays. From the catalogue of known star clusters, Henrik Svensmark has calculated the variation in cosmic rays over the past 500 million years, without needing to know the precise shape of the Milky Way Galaxy. Armed with that astronomical history, he digs deep into the histories of the climate and of life on Earth. Image ESA/NASA/Hubble

Today the Royal Astronomical Society in London publishes (online) Henrik Svensmark’s latest paper entitled “Evidence of nearby supernovae affecting life on Earth”. After years of effort Svensmark shows how the variable frequency of stellar explosions not far from our planet has ruled over the changing fortunes of living things throughout the past half billion years. Appearing in Monthly Notices of the Royal Astronomical Society, It’s a giant of a paper, with 22 figures, 30 equations and about 15,000 words. See the RAS press release athttp://www.ras.org.uk/news-and-press/219-news-2012/2117-did-exploding-stars-help-life-on-earth-to-thrive

By taking me back to when I reported the victory of the pioneers of plate tectonics in their battle against the most eminent geophysicists of the day, it makes me feel 40 years younger. Shredding the textbooks, Tuzo Wilson, Dan McKenzie and Jason Morgan merrily explained earthquakes, volcanoes, mountain-building, and even the varying depth of the ocean, simply by the drift of fragments of the lithosphere in various directions around the globe.

In Svensmark’s new paper an equally concise theory, that cosmic rays from exploded stars cool the world by increasing the cloud cover, leads to amazing explanations, not least for why evolution sometimes was rampant and sometimes faltered. In both senses of the word, this is a stellar revision of the story of life.

Here are the main results:

The long-term diversity of life in the sea depends on the sea-level set by plate tectonics and the local supernova rate set by the astrophysics, and on virtually nothing else.

The long-term primary productivity of life in the sea – the net growth of photosynthetic microbes – depends on the supernova rate, and on virtually nothing else.

Exceptionally close supernovae account for short-lived falls in sea-level during the past 500 million years, long-known to geophysicists but never convincingly explained..

As the geological and astronomical records converge, the match between climate and supernova rates gets better and better, with high rates bringing icy times.

Presented with due caution as well as with consideration for the feelings of experts in several fields of research, a story unfolds in which everything meshes like well-made clockwork. Anyone who wishes to pooh-pooh any piece of it by saying “correlation is not necessarily causality” should offer some other mega-theory that says why several mutually supportive coincidences arise between events in our galactic neighbourhood and living conditions on the Earth.

An amusing point is that Svensmark stands the currently popular carbon dioxide story on its head. Some geoscientists want to blame the drastic alternations of hot and icy conditions during the past 500 million years on increases and decreases in carbon dioxide, which they explain in intricate ways. For Svensmark, the changes driven by the stars govern the amount of carbon dioxide in the air. Climate and life control CO2, not the other way around.

By implication, supernovae also determine the amount of oxygen available for animals like you and me to breathe. So the inherently simple cosmic-ray/cloud hypothesis now has far-reaching consequences, which I’ve tried to sum up in this diagram.

Cosmic rays in action. The main findings in the new Svensmark paper concern the uppermost stellar band, the green band of living things and, on the right, atmospheric chemistry. Although solar modulation of galactic cosmic rays is important to us on short timescales, its effects are smaller and briefer than the major long-term changes controlled by the rate of formation of big stars in our vicinity, and their self-destruction as supernovae. Although copyrighted, this figure may be reproduced with due acknowledgement in the context of Henrik Svensmark's work.

By way of explanation

The text of “Evidence of nearby supernovae affecting life on Earth” is available via  ftp://ftp2.space.dtu.dk/pub/Svensmark/MNRAS_Svensmark2012.pdf The paper is highly technical, as befits a professional journal, so to non-expert eyes even the illustrations may be a little puzzling. So I’ve enlisted the aid of Liz Calder to explain the way one of the most striking graphs, Svensmark’s Figure 20, was put together. That graph shows how, over the past 440 million years, the changing rates of supernova explosions relatively close to the Earth have strongly influenced the biodiversity of marine invertebrate animals, from trilobites of ancient times to lobsters of today. Svensmark’s published caption ends: “Evidently marine biodiversity is largely explained by a combination of sea-level and astrophysical activity.” To follow his argument you need to see how Figure 20 draws on information in Figure 19. That tells of the total diversity of the sea creatures in the fossil record, fluctuating between times of rapid evolution and times of recession.

The count is by genera, which are groups of similar animals. Here it’s shown freehand by Liz in Sketch A. Sketch B is from another part of Figure 19, telling how the long-term global sea-level changed during the same period. The broad correspondence isn’t surprising because a high sea-level floods continental margins and gives the marine invertebrates more extensive and varied habitats. But it obviously isn’t the whole story. For a start, there’s a conspicuous spike in diversity about 270 million years ago that contradicts the declining sea-level. Svensmark knew that there was a strong peak in the supernova rate around that time. So he looked to see what would happen to the wiggles over the whole 440 million years if he “normalized” the biodiversity to remove the influence of sea-level. That simple operation is shown in Sketch C, where the 270-million-year spike becomes broader and taller. Sketch D shows Svensmark’s reckoning of the changing rates of nearby supernovae during the same period. Let me stress that these are all freehand sketches to explain the operations, not to convey the data. In the published paper, the graphs as in C and D are drawn precisely and superimposed for comparison.

This is Svensmark's Figure 20, with axes re-labelled with simpler words for the RAS press release. Biodiversity (the normalized marine invertebrate genera count) is in blue, with vertical bars indicating possible errors. The supernova rates are in black.

There are many fascinating particulars that I might use to illustrate the significance of Svensmark’s findings. To choose the Gorgon’s story that follows is not entirely arbitrary, because this brings in another of those top results, about supernovae and bio-productivity.

The great dying at the end of the Permian

Out of breath, poor gorgon? Gasping for some supernovae? Named after scary creatures of Greek myth, the Gorgonopsia of the Late Permian Period included this fossil species Sauroctonus progressus, 3 metres long. Like many of its therapsid cousins, near relatives of our own ancestors, it died out during the Permo-Triassic Event. Source: http://en.wikipedia.org/wiki/Gorgonopsia

Luckiest among our ancestors was a mammal-like reptile, or therapsid, that scraped through the Permo-Triassic Event, the worst catastrophe in the history of animal life. The climax was 251 million years ago at the end of the Permian Period. Nearly all animal species in the sea went extinct, along with most on land. The event ended the era of “old life”, the Palaeozoic, and ushered in the Mesozoic Era, when our ancestors would become small mammals trying to keep clear of the dinosaurs. So what put to death our previously flourishing Gorgon-faced cousins of the Late Permian? According to Henrik Svensmark, the Galaxy let the reptiles down.

Forget old suggestions (by myself included) that the impact of a comet or asteroid was to blame, like the one that did for the dinosaurs at the end of the Mesozoic. The greatest dying was less sudden than that. Similarly the impressive evidence for an eruption 250 million years ago – a flood basalt event that smothered Siberia with noxious volcanic rocks covering an area half the size of Australia – tells of only a belated regional coup de grâce. It’s more to the point that oxygen was in short supply – geologists speak of a “superanoxic ocean”. And there was far more carbon dioxide in the air than there is now.

Well there you go,” some people will say. “We told you CO2 is bad for you.” That, of course, overlooks the fact that the notorious gas keeps us alive. The recently increased CO2 shares with the plant breeders the credit for feeding the growing human population. Plants and photosynthetic microbes covet CO2 to grow. So in the late Permian its high concentration was a symptom of a big shortfall in life’s productivity, due to few supernovae, ice-free conditions, and a lack of weather to circulate the nutrients. And as photosynthesis is also badly needed to turn H2O into O2, the doomed animals were left gasping for oxygen, with little more than half of what we’re lucky to breathe today.

When Svensmark comments briefly on the Permo-Triassic Event in his new paper,Evidence of nearby supernovae affecting life on Earth,” he does so in the context of the finding that high rates of nearby supernovae promote life’s productivity by chilling the planet, and so improving the circulation of nutrients needed by the photosynthetic organisms.Here’s a sketch from Figure 22 in the paper, simplified to make it easier to read. Heavy carbon, 13C, is an indicator of how much photosynthesis was going on. Plumb in the middle is a downward pointing green dagger that marks the Permo-Triassic Event. And in the local supernova rate (black curve) Svensmark notes that the Late Permian saw the largest fall in the local supernova rate seen in the past 500 million years. This was when the Solar System had left the hyperactive Norma Arm of the Milky Way Galaxy behind it and entered the quiet space beyond. “Fatal consequences would ensue for marine life,” Svensmark writes, “if a rapid warming led to nutrient exhaustion … occurring too quickly for species to adapt.”

One size doesn’t fit all, and a fuller story of Late Permian biodiversity becomes subtler and even more persuasive. About 6 million years before the culminating mass extinction of 251 million years ago, a lesser one occurred at the end of the Guadalupian stage. This earlier extinction was linked with a brief resurgence in the supernova rate and a global cooling that interrupted the mid-Permian warming. In contrast with the end of the Permian, bio-productivity was high. The chief victims of this die-off were warm-water creatures including gigantic bivalves and rugose corals.

Why it’s tagged as “astrobiology”

So what, you may wonder, is the most life-enhancing supernova rate? Without wanting to sound like Voltaire’s Dr Pangloss, it’s probably not very far from the average rate for the past few hundred million years, nor very different from what we have now. Biodiversity and bio-productivity are both generous at present.

Svensmark has commented (not in the paper itself) on a closely related question – where’s the best place to live in the Galaxy?

Too many supernovae can threaten life with extinction. Although they came before the time range of the present paper, very severe episodes called Snowball Earth have been blamed on bursts of rapid star formation. I’ve tagged the paper as ‘Astrobiology’ because we may be very lucky in our location in the Galaxy. Other regions may be inhospitable for advanced forms of life because of too many supernovae or too few.”

Astronomers searching for life elsewhere speak of a Goldilocks Zone in planetary systems. A planet fit for life should be neither too near to nor too far from the parent star. We’re there in the Solar System, sure enough. We may also be in a similar Goldilocks Zone of the Milky Way, and other galaxies with too many or too few supernovae may be unfit for life. Add to that the huge planetary collision that created the Earth’s disproportionately large Moon and provided the orbital stability and active geology on which life relies, and you may suspect that, astronomically at least, Dr Pangloss was right — “Everything is for the best in the best of all possible worlds.”

Don’t fret about the diehards

If this blog has sometimes seemed too cocky about the Svensmark hypothesis, it’s because I’ve known what was in the pipeline, from theories, observations and experiments, long before publication. Since 1996 the hypothesis has brought new successes year by year and has resisted umpteen attempts to falsify it.

New additions at the level of microphysics include a previously unknown reaction of sulphuric acid, as in a recent preprint. On a vastly different scale, Svensmark’s present supernova paper gives us better knowledge of the shape of the Milky Way Galaxy.

A mark of a good hypothesis is that it looks better and better as time passes. With the triumph of plate tectonics, diehard opponents were left redfaced and blustering. In 1960 you’d not get a job in an American geology department if you believed in continental drift, but by 1970 you’d not get the job if you didn’t. That’s what a paradigm shift means in practice and it will happen sometime soon with cosmic rays in climate physics.

Plate tectonics was never much of a political issue, except in the Communist bloc. There, the immobility of continents was doctrinally imposed by the Soviet Academy of Sciences. An analagous diehard doctrine in climate physics went global two decades ago, when the Intergovernmental Panel on Climate Change was conceived to insist that natural causes of climate change are minor compared with human impacts.

Don’t fret about the diehards. The glory of empirical science is this: no matter how many years, decades, or sometimes centuries it may take, in the end the story will come out right.


Quantum computing forges ahead

08/03/2012

Updating Magic Universe

So what’s a Majorana fermion then?

A news item in today’s Nature reminds me that last week it was all happening with quantum computing at a meeting of the American Physical Society. IBM announced a breakthrough in the technology, predicting practical computers of unimaginable power within 10 or 15 years. And in Nature Eugenie Samuel Reich discusses what seems to be a discovery of cosmic importance by a team in Delft, announced at the APS meeting. I’ll sum up two strands of progress in a brief update.

In Magic Universe the last section of the story called “BITS AND QUBITS: the digital world and its quantum shadow looming” reads so far:

Towards quantum computers

For a second revolution in information technology, the experts looked to the spooky behaviour of electrons and atoms known in quantum theory. By 2002 physicists in Australia had made the equivalent of Shannon’s relays of 65 years earlier, but now the switches offered not binary bits, but qubits, pronounced cue-bits. They raised hopes that the first quantum computers might be operating before the first decade of the new century was out.

   Whereas electric relays, and their electronic successors in microchips, provide the simple on/off, true/false, 1/0 options expressed as bits of information, the qubits in the corresponding quantum devices will have many possible states. In theory it is possible to make an extremely fast computer by exploiting ambiguities that are present all the time, in quantum theory.

   If you’re not sure whether an electron in an atom is in one possible energy state, or in the next higher energy state permitted by the physical laws, then it can be considered to be both states at once. In computing terms it represents both 1 and 0 at the same time. Two such ambiguities give you four numbers, 00, 01, 10 and 11, which are the binary-number equivalents of good old 0, 1, 2 and 3. Three ambiguities give eight numbers, and so on, until with fifty you have a million billion numbers represented simultaneously in the quantum computer. In theory the machine can compute with all of them at the same time.

   Such quantum spookiness spooks the spooks. The world’s secret services are still engaged in the centuries-old contest between code-makers and code-breakers. There are new concepts called quantum one-time pads for a supposedly unbreakable cipher, but some experts suspect that a powerful enough quantum computer could crack anything. Who knows what developments may be going on behind the scenes, like the secret work on digital computing by Alan Turing at Bletchley Park in England during the Second World War?

   The Australians were up-front about their intentions. They simply wanted to beat the rest of the world in developing a practical machine, for the sake of the commercial payoff it would bring. The Centre for Quantum Computer Technology was founded in January 2000, with federal funding, and with participating teams in the Universities of New South Wales, Queensland and Melbourne.

   The striking thing was the confidence of project members about what they were attempting. A widespread opinion at the start of the 20th Century held that quantum computing was beyond practical reach for the time being. It was seen as requiring exquisite delicacy in construction and operation, with the ever-present danger that the slightest external interference or mismanagement could cause the whole multiply parallel computation to cave in, like a mistimed soufflé.

   The qubit switches developed in Australia consist of phosphorus atoms implanted in silicon using a high-energy beam aimed with high precision. Phosphorus atoms can sustain a particular state of charge for longer than most atoms, thereby reducing the risk of the soufflé effect. A pair of phosphorus atoms, together with a transistor for reading out their state, constitutes one qubit. Unveiling the first example at a meeting in London, Robert Clark of New South Wales said, ‘This was thought to be impossible just a few years ago.’

Update March 2012 – subject to confirmation of the Majorana fermion

Ten years later, when many others had joined in a prolonged experimental quest for quantum computing, IBM researchers at Yorktown Height s claimed to be within sight of a practical device within 10 or 15 years. Dogging all the experimenters was a problem called decoherence  – would the qbits survive long enough to be checked for possible errors?

In 2012 Matthias Steffen of IBM told a reporter, “In 1999, coherence times were about 1 nanosecond.  Last year, coherence times were achieved for as long as 1 to 4 microseconds. With [our] new techniques, we’ve achieved coherence times of 10 to 100 microseconds. We need to improve that by a factor of 10 to 100 before we’re at the threshold [where] we want to be. But considering that in the past ten years we’ve increased coherence times by a factor of 10,000, I’m not scared.”

Then it would be a matter of scaling up from devices handling one or two qbits to an array with, say, 250 qubits., That would contain more ordinary bits of information than there are atoms in the entire universe and it would be capable of performing millions of computations simultaneously. No existing code could withstand its probing, which probably explains why the US Army funded IBM’s work.

Ettore Majorana - CERN image

A by-product of quantum computing research was the discovery of a new particle in the cosmos. In 1937  the Italian physicist Ettore Majorana adapted a theory by the British Paul Dirac to predict a particle that is its own antiparticle – a very strange item indeed! It would be electrically neutral and exhibit peculiar behaviour.

A team led by Leo Kouwenhoven at Delft University of Technology in the Netherland, tested experimentally a suggestion from 2010 about how to create a pair of these particles. At a very low temperature and in a magnetic field, you touch a superconductor with an extremely fine semiconducting wire. As the signature of the presence of “Majorana fermions”, confirmed by the experimental team, the resistance in the wire becomes very low at zero voltage.

The Majorana particle opened a new route to quantum computing, because of its special ability to remember if it swaps places with a sibling. It was expected to be particularly resistant to the decoherence that plagued other techniques. So the Delft discovery promised a new research industry.

References

Steffen quoted by Alex Knapp in Forbes 28 February 2012 http://www.forbes.com/sites/alexknapp/2012/02/28/ibm-paves-the-way-towards-scalable-quantum-computing/

IBM Press Release 28 February 2012 http://www-03.ibm.com/press/us/en/pressrelease/36901.wss

Nature News 8 March 2012: http://www.nature.com/news/a-solid-case-for-majorana-fermions-1.10174

Nature News 28 Feb 2012 http://www.nature.com/news/quest-for-quirky-quantum-particles-may-have-struck-gold-1.10124

“A suggestion from 2010”: paper by Lutchyn et al. in PRL available at arXiv:1002.4033v2


Climate Physics 101

03/03/2012

Climate change: news and comments

Sorry folks, cosmic rays really are in charge

 

On this blog and others, most comments about my previous post “Yet another trick of cosmic rays” have been friendly. Thank you. But some people still want to dismiss all the meticulous experimental, observational and theoretical work of Henrik Svensmark and his colleagues in the Danish National Space Institute by saying there is simply no link between cosmic rays and the climate.

Having written two books on the subject, and still engaged with it, I could in rebuttal flood this post with evidence of many kinds, on time scales from days to millennia or longer. I’ll content myself with just one pair of graphs spanning 50 years. They’re from a 2007 report by Svensmark and the Institute’s director, Eigil Friis-Christensen, and they’re based on a European Space Agency project called ISAC. The carbon dioxide boys and girls would die for a match of cause and effect of this quality.

Cosmic ray intensity is in red and upside down, so that 1991 was a minimum, not a maximum. Fewer cosmic rays mean a warmer world, and the cosmic rays vary with the solar cycle. The blue curve shows the global mean temperature of the mid-troposphere as measured with balloons and collated by the UK Met Office (HadAT2).

In the upper panel the temperatures roughly follow the solar cycle. The match is much better when well-known effects of other natural disturbances (El Niño, North Atlantic Oscillation, big volcanoes) are removed, together with an upward trend of 0.14 deg. C per decade. The trend may be partly due to man-made greenhouse gases, but the magnitude of their contribution is debatable.

From 2000 to 2011 mid-tropospheric temperatures have remained pretty level, like those of the surface, despite the continuing increase in the gases – in “flat” contradiction to the warming predicted by the Intergovernmental Panel on Climate Change. Meanwhile the Sun is lazy, cosmic ray counts are high and the oceans are cooling.

Reference

Svensmark, H. and Friis-Christensen, E., “Reply to Lockwood and Fröhlich The persistent role of the Sun in climate forcing”, Danish National Space Center Scientific Report 3/2007.


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