Philae comes in to land on 67P/Churyumov-Gerasimenko. It reached the comet using carefully calculated forces of attraction. Image: 2014 European Space Agency/Getty
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Wandering in the heavens: how mathematics explains Saturn’s rings

Ian Stewart shows how maths is changing cosmology, and explains why the best way to reach a comet near Mars is to go round the back of the sun.

The Enūma Anu Enlil, a series of 70 clay tablets, was found in the ruins of King Ashurbanipal’s library in Nineveh (on the eastern bank of the River Tigris, opposite modern-day Mosul in Iraq). The name means “in the days of Anu and Enlil”; Anu was the sky god, Enlil the wind god. The tablets, which date as far back as 1950BC, list 7,000 omens from Babylonian astrology: “If the moon can be seen on the first day, the land will be happy.” But tablet 63 is different: it gives the times when Venus first became visible, or disappeared, over a 21-year period. This Venus tablet of Ammisaduqa is the earliest known record of planetary observations.

The Babylonians were expert astronomers who produced star catalogues and tables of eclipses, planetary motion and changes in the length of day. They were also capable mathematicians, with a number system much like ours, but using base 60 rather than ten. They could solve quadratic equations and calculate the diagonal of a square with precision, and they applied their mathematical skills to the heavens. In those days, mathematics and astronomy were part and parcel of astrology and religion, and the whole package was intimately bound up with agriculture through the progression of the seasons.

The torch of astronomy passed by way of ancient Greece to India. In 6th-century India, mathematics was a sub-branch of astronomy, and astronomy still played second fiddle to reading omens in the stars. The Arab world made further advances in our understanding of the cosmos, and kept the ancient knowledge alive until Europe once more turned its attentions to the science of the heavens.

In 1601 Johannes Kepler became imperial mathematician to the Holy Roman emperor Rudolf II. Casting the emperor’s horoscope paid the bills, and it also left time for serious mathematics and astronomy. Kepler had inherited accurate observations of Mars from his former master Tycho Brahe, and from these he extracted three mathematical patterns, his laws of planetary motion. By then, thanks to Nicolaus Copernicus, it was known – though still controversial, to say the least – that the planets revolve round the sun, not the Earth. Their orbits were thought to be combinations of circles, but Kepler’s calculations showed that planets move in ellipses. His other two laws govern how quickly the planet moves and how long it takes to go round the sun.

In his epic Mathematical Principles of Natural Philosophy of 1687, Isaac Newton built on Kepler’s laws and deduced his law of universal gravitation: every body in the universe attracts every other body with a force that obeys a specific mathematical rule. These forces determine how moons, planets and stars move. Newton’s book paved the way to a rational scientific understanding of nature based on precise mathematical laws, and opened up the metaphor of the clockwork universe.

One of the great tests of Newtonian gravitation was Edmond Halley’s prediction about a comet. In ancient times comets, bright bodies with long curved tails that seemed to appear from nowhere, were seen as omens of disaster. From old records, Halley realised one particular comet was a repeat visitor, with an elliptical orbit that took it near the Earth every 76 years. He predicted its next return in 1758. By then Halley was dead, but his prediction proved correct.

Even today, Newton’s law remains vital to astronomy and space exploration; Einstein’s later refinements are seldom needed. A topical example concerns another comet, rejoicing in the name 67P/Churyumov-Gerasimenko, which takes about six and a half years to orbit the sun. In 2004 the European Space Agency (ESA) launched the Rosetta probe to visit the comet and find out what it looked like and what it was made of. Famously, it resembled a rubber duck: two round lumps joined by a narrow neck. On 12 November 2014 a small capsule, Philae, landed on the head of the duck, which was 480 million kilometres from Earth and travelling at over 50,000 kilometres per hour. Unfortunately Philae bounced and ended up on its side, but even so it had sent back vital and unprecedented data.

It’s worth visiting the ESA’s “Where is Rosetta?” web page to see an animation of the astonishing route the probe took. It wasn’t direct. The probe began by moving towards the sun, even though the comet was far outside the orbit of Mars, and moving away. Rosetta’s orbit swung past the sun, returned close to the Earth, and was flung outwards to an encounter with Mars. It then swung back to meet the Earth for a second time, then back beyond Mars’s orbit. By now the comet was on the far side of the sun and closer to it than Rosetta was. A third encounter with Earth flung the probe outwards again, chasing the comet as it now sped away from the sun. Finally, Rosetta made its rendezvous with destiny.

Why such a complicated route? The ESA didn’t just point its rocket at the comet and blast off. That would have required far too much fuel, and by the time it got there the comet would have been somewhere else. Instead, Rosetta performed a carefully choreographed cosmic dance, tugged by the combined gravitational forces of the sun, the Earth, Mars and other relevant bodies. Its route was designed for fuel efficiency; the price paid was that it took Rosetta ten years to get to its destination. Each close fly-by with Earth and Mars gave the probe a free boost as it borrowed energy from the planet. An occasional small burst from four thrusters kept the craft on track. And every kilometre of the trip was governed by Newton’s law of gravity.

Complex trajectories such as this one have now become standard in many unmanned space missions. They originated in mathematical studies of chaotic dynamics in the motion of three gravitating bodies, and go back to pioneering work by Edward Belbruno at the Jet Propulsion Laboratory in California in 1990. He realised that these techniques could put a Japanese probe, Hiten, into lunar orbit after a failure of its parent craft, even though there was hardly any fuel available.

Mathematics has always enjoyed a close relationship with astronomy; not just in the technology of space missions but in understanding planets, stars, galaxies – even the entire universe. How, for example, did the solar system form? We can’t go back to take a look, so we have to do some celestial archaeology, inferring what happened from the evidence that remains. Our main tool is mathematical modelling, which lets us test whether hypothetical scenarios make sense.

When Galileo first spied Saturn in 1610, he took it to be a trinity of planets. Image: Nasa/Eyevine

Observations and theoretical astrophysics tell us that the sun came into being about 4.8 billion years ago, and the planets of the solar system formed at much the same time. Everything condensed out of the solar nebula, a huge cloud of gas – mainly hydrogen and helium, the two commonest elements in the universe. The cloud was about 65 light years across, 15 times the distance to the nearest star today. One fragment, about four light years across, gave rise to the solar system; other fragments became other stars – many of which, we now know, have their own planets. As our fragment collapsed under its own gravitational field, most of the gas collected at the centre, where enormous pressures ignited nuclear reactions to create the sun. Much of the remaining gas clumped into smaller, but still gigantic, bodies: the planets. The rest either got swept away or remains as various items of clutter – asteroids; centaurs (small bodies with characteristics of both comets and asteroids); Kuiper Belt objects, in the debris field beyond Neptune; comets in the Oort Cloud, which is a quarter of the way to the next-nearest star.

This scenario, minus the nuclear physics, was first proposed in the 18th century, but fell out of favour in the 20th because it seemed not to account for the sun’s low angular momentum (a measure of how much rotation it has, taking into account its mass and speed) compared to that of the planets. But in the 1980s astronomers observed gas clouds round young stars, and mathematical modelling of the collapsing clouds showed plausible, and very dramatic, mechanisms that fitted the observations.

According to these ideas, the early solar system was very different from the sedate one we see today. The planets formed not as single clumps, but by a chaotic process of accretion. For the first 100,000 years, slowly growing “planetesimals” swept up gas and dust, and created circular rings in the nebula by clearing out gaps between them. Each gap was littered with millions of these tiny bodies. At that point the planetesimals ran out of new matter to sweep up, but there were so many of them that they kept bumping into each other. Some broke up, but others merged; the mergers won and planets built up, piece by tiny piece.

Late in 2014 dramatic evidence for this process was found: an image of a proto-planetary disc around the young star HL Tau, 450 light years away in the Taurus
constellation. This image showed concentric bright rings of gas, with dark rings in between. The dark rings are almost cer­tainly caused by nascent planets sweeping up dust and gas.

Until very recently, astronomers thought that once the solar system came into being it was very stable: the planets trundled ponderously along preordained orbits and nothing much changed. No longer: it is now thought that the larger worlds – the gas giants Jupiter and Saturn and the ice giants Uranus and Neptune – first appeared outside the “frost line” where water freezes, but subsequently reorganised each other in a lengthy gravitational tug of war.

In the early solar system, the giants were closer together and millions of planetesimals roamed the outer regions. Today the order of the giants, outwards from the sun, is Jupiter, Saturn, Uranus, Neptune. But in one likely scenario it was originally Jupiter, Neptune, Uranus, Saturn. When the solar system was about 600 million years old, this cosy arrangement came to an end. All of the planets’ orbital periods were slowly changing, and Jupiter and Saturn wandered into a 2:1 resonance – Saturn’s “year” became twice that of Jupiter. Repeated alignments of these two worlds then pushed Neptune and Uranus outwards, with Neptune overtaking Uranus. This disturbed the planetesimals, making them fall towards the sun. Chaos erupted in the solar system as planetesimals played celestial pinball among the planets. The giant planets moved out, and the planetesimals moved in. Eventually the planetesimals took on Jupiter, whose huge mass was decisive. Some were flung out of the solar system altogether, while the rest went into long, thin orbits stretching out to vast distances. After that, it mostly settled down.

These theories are not idle speculation. They are supported by huge computer calculations of the solar system’s dynamics over billions of years, carried out in particular by the research groups of Jack Wisdom of the Massachusetts Institute of Technology and Jacques Laskar of CNRS, the French national centre for scientific research. Some cunning mathematics is required even to set up these simulations: the deep structure of the laws of motion must not be disturbed by the unavoidable numerical approximations that occur. This structure includes the laws of conservation of energy and angular momentum, whose totals cannot change. Amazingly, the planetary migrations not only keep these quantities in balance, but happen because they balance.

Another playground for mathematicians and astronomers investigating Newtonian gravitation is the rings of Saturn. The most distant of the planets known to the ancients, Saturn is about 1.3 billion kilometres from Earth. In 1610, when Galileo looked at Saturn through his telescope, he sent his fellows a Latin anagram: smaismrmilmepoetaleumibunenugttauiras. This was a standard way to preannounce a discovery without giving it away. Kepler deciphered it as reading – in translation – “Be greeted, double knob, offspring of Mars,” and thought Galileo was claiming Mars had two moons (as Kepler had predicted, and rightly so). But Galileo later explained that his anagram actually meant: “I have observed the most distant of planets to have a triple form.” That is, Saturn consists of three bodies.

So much for anagrams.

Galileo’s image of the planet was blurred. Using a better telescope, the Dutch mathematician Christiaan Huygens realised that the middle body was the planet and the others were parts of a gigantic system of rings. Mathematics proves – contrary to an early suggestion by the French scholar Pierre-Simon Laplace – that the rings cannot be solid. In fact, they are made up of ice particles, ranging in size from fine dust to lumps ten metres across. There are several current theories for the rings’ formation: the break-up of a moon, or perhaps leftovers from Saturn’s own primordial nebula. Mathematics is being used to try to find out which explanation, if any, is correct.

Mathematical studies also explain many puzzling features of Saturn’s rings. For one thing, the rings are dense in some regions, but so thin in others that at first sight there seem to be gaps. Some of these gaps come from resonances between the rings and the periods of Saturn’s 62 moons, which can systematically disturb gas in orbits related to that of the moon itself. Other gaps are organised by “shepherd moons” that hustle out any sheepish moonlet that strays into the gap. When the spacecraft Voyager 1 flew past in 1980, some rings appeared to be braided. We now know that they are kinked and lumpy, another subtle consequence of Newtonian gravity in this complex system.

Mathematics has illuminated many other cosmic puzzles: the formation of Earth’s moon, the future of the solar system, the formation and dynamics of galaxies – even the origin of the universe itself in the Big Bang. In ancient India, mathematics was a sub-branch of astronomy. Today, if anything, it is the other way round. Mathematicians are making discoveries and inventing methods; astronomers and cosmologists are making ever greater use of the latest mathematical tools and concepts to advance this utterly fascinating subject. Mathematical thinking teaches us more about humanity’s place in the universe. And it helps us to seek out new places.

Ian Stewart is an emeritus professor of mathematics at the University of Warwick

This article first appeared in the 19 December 2014 issue of the New Statesman, Christmas Issue 2014

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Losing Momentum: how Jeremy Corbyn’s support group ran out of steam

Tom Watson says it is destroying Labour. Its supporters say it is a vital force for change. Our correspondent spent six months following the movement, and asks: what is the truth about Momentum?

1. The Bus

 The bus to the Momentum conference in Liverpool leaves at seven on a Sunday morning in late September from Euston Station, and the whole journey feels like a parody of a neoliberal play about the failings of socialism. We depart an hour late because activists have overslept and we cannot go without them. As we wait we discuss whether Jeremy Corbyn will be re-elected leader of the Labour Party this very day. One man says not; a young, jolly girl with blonde hair cries: “Don’t say that on Jezmas!” She is joking, at least about “Jezmas”.

A man walks up. “Trots?” he says, calmly. He is joking, too; and I wonder if he says it because the idea of Momentum is more exciting to outsiders than the reality, and he knows it; there is an awful pleasure in being misunderstood. Momentum was formed in late 2015 to build on Corbyn’s initial victory in the Labour leadership election, and it is perceived as a ragtag army of placard-waving Trots, newly engaged clicktivists and Corbyn fanatics.

We leave, and learn on the M1 that, in some terrible metaphor, the coach is broken and cannot drive at more than 20mph. So we wait for another coach at a service station slightly beyond Luton. “Sabotage,” says one man. He is joking, too. We get off; another man offers me his vegan bread and we discuss Karl Marx.

A new coach arrives and I listen to the others discuss Jeremy Corbyn’s problems. No one talks about his polling, because that is depressing and unnecessary for their purpose – which, here, is dreaming. They talk about Corbyn as addicts talk about a drug. Nothing can touch him, and nothing is ever his fault. “There are problems with the press office,” says one. “Perhaps he needs better PAs?” says another.

One man thinks there will be a non-specific revolution: “I hope it won’t be violent,” he frets. “There have been violent revolutions in the past.” “I stuck it out during Blair and it was worth it,” says another. “They’ve had their go.” “We don’t need them [the Blairites],” says a third. “If new members come in, it will sort itself out,” says a fourth.

I have heard this before. Momentum supporters have told me that Labour does not need floating voters, who are somehow tainted because they dare to float. This seems to me a kind of madness. I do not know how the Labour Party will win a general election in a parliamentary democracy without floating voters; and I don’t think these people do, either.

But this is a coach of believers. Say you are not sure that Corbyn can win a general election and they scowl at you. That you are in total agreement with them is assumed, because this is the solidarity bus; and if you are in total agreement with them they are the sweetest people in the world.

That is why I do not tell them that I am a journalist. I am afraid to, and this fear baffles me. I have gone everywhere as a journalist but with these, my fellow-travellers on the left, I am scared to say it; and that, too, frightens me. MSM, they might call me – mainstream media. What it really means is: collaborator.

The man beside me has been ill. He talks sweetly about the potential renewal of society under Corbyn’s Labour as a metaphor for his own recovery, and this moves him; he has not been involved in politics until now. I like this man very much, until I mention the Jewish Labour MP Luciana Berger and the anti-Semitism she has suffered from Corbyn supporters and others; and he says, simply, that she has been employed by the state of Israel. He says nothing else about her, as if there were nothing else to say.

We listen to the results of the leadership election on the radio; we should be in Liverpool at the Black-E community centre to celebrate, but the solidarity bus is late. Corbyn thanks his supporters. “You’re welcome, Jeremy,” says a woman in the front row, as if he were on the coach. She nods emphatically, and repeats it to the man who isn’t there: “You’re welcome, Jeremy.”

In Liverpool, some of the passengers sleep on the floor at a community centre. The venue has been hired for that purpose: this is Momentum’s commitment to opening up politics to the non-connected, the previously non-engaged, and the outsiders who will attend their conference in a deconsecrated church, even as the official Labour conference convenes a mile away. But never mind that: this is the one that matters, and it is called The World Transformed.

 

2. The Conference

Later that day, outside the Black-E, a man comes up to me. Are you happy, he asks, which is a normal question here. These are, at least partly, the politics of feelings: we must do feelings, because the Tories, apparently, don’t. I say I’m worried about marginal seats, specifically that Jeremy – he is always Jeremy, the use of his Christian name is a symbol of his goodness, his accessibility and his singularity – cannot win them.

“The polls aren’t his fault,” the man says, “it’s [Labour] people briefing the Tories that he is unelectable.” I do not think it’s that simple but it’s easy to feel like an idiot – or a monster – here, where there is such conviction. As if there is something that only you, the unconvinced, have missed: that Jeremy, given the right light, hat or PA, could lead a socialist revolution in a country where 13 million people watched Downton Abbey.

But the man does say something interesting which I hope is true. “This is not about Jeremy, not really,” he says. “It is about what he represents.” He means Momentum can survive without him.

There is a square hall with trade union banners and a shop that sells Poems for Jeremy Corbyn, as well as a Corbyn-themed colouring book. When I am finally outed as a journalist, and made to wear a vast red badge that says PRESS, I attempt to buy one. “That’s all journalists are interested in,” the proprietor says angrily. That is one of our moral stains, apparently: a disproportionate (and sinister) interest in colouring books.

I go to the Black Lives Matter event. A woman talks about the experience of black students in universities and the impact of austerity on the black community. Another woman tells us that her five-year-old son wishes he was white; we listen while she cries. I go to the feminism meeting and change my mind about the legalisation of prostitution after a woman’s testimony about reporting an assault, and then being assaulted again by a police officer because of her legal status. Then I hear a former miner tell a room how the police nearly killed him on a picket line, and then arrested him.

This, to me, a veteran of party conferences, is extraordinary, although it shouldn’t be, and the fact that I am surprised is shameful. Momentum is full of the kinds of ­people you never see at political events: that is, the people politics is for. Women, members of minority communities (but not Zionist Jews, naturally), the disabled: all are treated with exaggerated courtesy, as if the Black-E had established a mirror world of its choosing, where everything outside is inverted.

When Corbyn arrives he does not orate: he ruminates. “We are not going to cascade poverty from generation to generation,” he says. “We are here to transform society and the world.” I applaud his sentiment; I share it. I just wish I could believe he can deliver it outside, in the other world. So I veer ­between hope and fury; between the certainty that they will achieve nothing but an eternal Conservative government, and the ever-nagging truth that makes me stay: what else is there?

There is a rally on Monday night. Momentum members discuss the “purges” of socialist and communist-leaning members from Labour for comments they made on social media, and whether détente is possible. A nurse asks: “How do we know that ‘wipe the slate clean’ means the same for us as it does for them? How on Earth can we trust the likes of Hilary Benn who dresses himself up in the rhetoric of socialism to justify bombing Syria? The plotters who took the olive branch offered by Jeremy to stab him in the back with another chicken coup?” I am not sure where she is going with that gag, or if it is even a gag.

The next man to speak had been at the Labour party conference earlier in the day; he saw Len McCluskey, John McDonnell and Clive Lewis on the platform. “Don’t be pessimistic, folks,” he cries. “On the floor of conference today we owned the party. Progress [the centrist Labour pressure group] are the weirdos now. We own the party!”

A man from Hammersmith and Fulham Momentum is next. “The national committee of Momentum was not elected by conference,” he says. “It’s a committee meeting knocked up behind closed doors by leading people on the left, including our two heroes.” He means Jeremy Corbyn and John McDonnell. This is explicit heresy, and the chair interrupts him: “Stan, Stan . . .” “I’m winding up!” he says. “We need a central committee of Momentum elected by conference,” he says, and sits down.

The following day Corbyn speaks in the hall in front of golden balloons that spell out S-H-E-E-P. It may be another gag, but who can tell, from his face? This is his commitment to not doing politics the recognisable way. He is the man who walks by himself, towards balloons that say S-H-E-E-P. (They are advertising the band that will follow him. They are called, and dressed as, sheep.) The nobility of it, you could say. Or the idiocy. He mocks the mockers of Momentum: is it, he was asked by the mainstream media, full of extremists and entryists? “I’m not controlling any of it,” he says calmly, and in this calmness is all the Twitter-borne aggression that people complain of when they talk about Momentum, for he enables it with his self-satisfied smile. “It’s not my way to try and control the way people do things. I want people to come together.” He laughs, because no one can touch him, and nothing is ever his fault.

I meet many principled people in Liverpool whose testimony convinces me, and I didn’t need convincing, that austerity is a national disaster. I meet only one person who thinks that Momentum should take over the Labour Party. The maddest suggestion I hear is that all media should be state-controlled so that they won’t be rude about a future Corbyn government and any tribute colouring books.

 

3. The HQ

Momentum HQ is in the TSSA transport and travel union building by Euston Station in London. I meet Jon Lansman, Tony Benn’s former fixer and the founder of Momentum, in a basement room in October. Lansman, who read economics at Cambridge, lived on the fringes of Labour for 30 years before volunteering for Corbyn’s campaign for the leadership.

The terms are these: I can ask whatever I want, but afterwards James Schneider, the 29-year-old national organiser (who has since left to work for Corbyn’s press team), will decide what I can and cannot print. ­Momentum HQ wants control of the message; with all the talk of entryism and infighting reported in the mainstream media, the movement needs it.

There is a civil war between Jon Lansman and the Alliance for Workers’ Liberty (AWL) and other far-left factions, which, I am told, “wish to organise in an outdated manner out of step with the majority of Momentum members”. Some of the Momentum leadership believe that the AWL and its allies want to use Momentum to found a new party to the left of Labour. Jill Mountford, then a member of Momentum’s steering committee, has been expelled from Labour for being a member of the AWL. It screams across the blogs and on Facebook; more parody. We don’t talk about that – Schneider calls it “Kremlinology”. It is a problem, yes, but it is not insurmountable. We talk about the future, and the past.

So, Lansman. I look at him. The right considers him an evil Bennite wizard to be feared and mocked; the far left, a Stalinist, which seems unfair. It must be exhausting. I see a tired, middle-aged man attending perhaps his fifteenth meeting in a day. His hair is unruly. He wears a T-shirt.

The last Labour government, he says, did one thing and said another: “Wanting a liberal immigration policy while talking tough about refugees and migrants. Having a strong welfare policy and generous tax credits while talking about ‘strivers’ and ‘scroungers’ unfortunately shifted opinion the wrong way.”

It also alienated the party membership: “Their approach was based on ensuring that everyone was on-message with high levels of control.” It was an “authoritarian structure even in the PLP [Parliamentary Labour Party]. Even in the cabinet. It killed off the enthusiasm of the membership. They never published the figures in 2009 because it dropped below 100,000. We’ve now got 600,000.” (The membership has since dropped to roughly 528,000.)

And the strategy? “If you have hundreds of thousands of people having millions of conversations with people in communities and workplaces you can change opinion,” he says. “That’s the great advantage of ­having a mass movement. And if we can change the Labour Party’s attitude to its members and see them as a resource – not a threat or inconvenience.”

That, then, is the strategy: street by street and house by house. “We can’t win on the back of only the poorest and only the most disadvantaged,” he says. “We have to win the votes of skilled workers and plenty of middle-class people, too – but they are all suffering from some aspects of Tory misrule.”

I ask about polling because, at the time, a Times/YouGov poll has Labour on 27 per cent to the Tories’ 41 per cent. He doesn’t mind. “It was,” he says, “always going to be a very hard battle to win the next election. I think everyone across the party will privately admit that.” He doesn’t think that if Yvette Cooper or Andy Burnham were leader they would be polling any better.

Upstairs the office is full of activists. They are young, rational and convincing (although, after the Copeland by-election on 23 February, I will wonder if they are only really convincing themselves). They talk about their membership of 20,000, and 150 local groups, and 600,000 Labour Party members, and the breadth of age and background of the volunteers – from teenagers to people in their eighties. One of them – Ray Madron, 84 – paints his hatred of Tony Blair like a portrait in the air. He has a ­marvellously posh voice. Most of all, they talk about the wounds of austerity. Where, they want to know, is the anger? They are searching for it.

Emma Rees, a national organiser, speaks in the calm, precise tones of the schoolteacher she once was. “A lot of people are sick and tired of the status quo, of politics as usual, and I think trying to do things differently is hard because there isn’t a road map and it’s not clear exactly what you’re supposed to do,” she says. She adds: “It is a coalition of different sorts of people and holding all those people together can sometimes be a challenge.”

Is she alluding to entryism? One activist, who asks not to be named, says: “I don’t want to insult anyone, but if you rounded up all the members of the Socialist Workers Party [SWP] and the Socialist Party and any other ultra-left sect, you could probably fit them in one room. Momentum has 20,000 members.”

The SWP were outside at The World Transformed in Liverpool, I say, like an ambivalent picket line. “Well,” James Schneider says pointedly, “they were outside.”

Momentum, Emma Rees says, “is seeking to help the Labour Party become that transformative party that will get into government but doesn’t fall back on that tried and failed way of winning elections”.

They tell me this repeatedly, and it is true: no one knows what will work. “The people who criticised us don’t have any route to electability, either,” says Joe Todd, who organises events for Momentum. He is a tall, bespectacled man with a kindly, open face.

“They lost two elections before Jeremy Corbyn. It’s obvious we need to do something differently,” he says. “Politics feels distant for most people: it doesn’t seem to offer any hope for real change.

“The left has been timid and negative. More and more people are talking about how we can transform society, and how these transformations link to people’s everyday experience. Build a movement like that,” Todd says, and his eyes swell, “and all the old rules of politics – the centre ground, swing constituencies to a certain extent – are blown out of the water.”

Momentum sends me, with a young volunteer as chaperone, to a rally in Chester in October to watch activists try to muster support for local hospitals. They set up a stall in the centre of the shopping district, with its mad dissonance of coffee shops and medieval houses. From what I can see, people – yet far too few people – listen politely to the speeches about austerity and sign up for more information; but I can hear the hum of internal dissent when an activist, who asks not to be named, tells me he will work for the local Labour MP to be deselected. (The official Momentum line on deselection is, quite rightly, that it is a matter for local parties.)

We will not know what matters – is it effective? – until the general election, because no one knows what will work.

 

4. The Fallout

Now comes the result of the by-election in Copeland in the north-west of England, and the first time since 1982 that a ruling government has taken a seat from the opposition in a by-election. Momentum canvassed enthusiastically (they sent 85 carloads of activists to the constituency) but they failed, and pronounce themselves “devastated”. The whispers – this time of a “soft” coup against Corbyn – begin again.

Rees describes calls for Jeremy Corbyn to resign as “misguided. Labour’s decline long pre-dates Corbyn’s leadership.”

This produces a furious response from Luke Akehurst, a former London Labour ­councillor in Hackney, on labourlist.org. He insists that Labour’s decline has accelerated under Corbyn; that even though Rees says that “Labour has been haemorrhaging votes in election after election in Copeland since 1997”, the majority increased in 2005 and the number of votes rose in 2010, despite an adverse boundary change. “This,” he writes, “was a seat where the Labour vote was remarkably stable at between 16,750 and 19,699 in every general election between 2001 and 2015, then fell off a cliff to 11,601, a third of it going AWOL, last Thursday.”

And he adds that “‘85 carloads of Mom­entum activists’ going to Copeland is just increasing the party’s ability to record whose votes it has lost”.

But still they plan, and believe, even if no one knows what will work; surely there is some antidote to Mayism, if they search every street in the UK? Momentum’s national conference, which was repeatedly postponed, is now definitively scheduled for 25 March. Stan who complained about a democratic deficit within Momentum at The World Transformed got his way. So did Lansman. In January the steering committee voted to dissolve Momentum’s structures and introduce a constitution, after consulting the membership. A new national co-ordinating group has been elected, and met for the first time on 11 March – although, inevitably, a group called Momentum Grassroots held a rival meeting that very day.

I go to the Euston offices for a final briefing. There, two young women – Sophie and Georgie, and that will make those who think in parodies laugh – tell me that, in future, only members of the Labour Party will be allowed to join Momentum, and existing members must join Labour by 1 July. Those expelled from Labour “may be deemed to have resigned from Momentum after 1 July” – but they will have a right to a hearing.

More details of the plan are exposed when, a week later, a recording of Jon Lansman’s speech to a Momentum meeting in Richmond on 1 March is leaked to the Observer. Lansman told the Richmond branch that Momentum members must hold positions within the Labour Party to ensure that Corbyn’s successor – they are now talking about a successor – is to their liking. He also said that, should Len McCluskey be re-elected as general secretary of Unite, the union would formally affiliate to Momentum.

Tom Watson, the deputy leader of the party, was furious when he found out, calling it “a private agreement to fund a political faction that is apparently planning to take control of the Labour Party, as well as organise in the GMB and Unison”.

There was then, I am told, “a short but stormy discussion at the away day at Unison” on Monday 20 March, where the inner circle of John McDonnell, Diane Abbott and Emily Thornberry “laid into” Watson, but Shami Chakrabarti made the peace; I would have liked to see that. Watson then released a bland joint statement with Corbyn which mentioned “a robust and constructive discussion about the challenges and opportunities ahead”.

Jon Lansman, of course, is more interesting. “This is a non-story,” he tells me. “Momentum is encouraging members to get active in the party, to support socialist policies and rule changes that would make Labour a more grass-roots and democratic party, and to campaign for Labour victories. There is nothing scandalous and sinister about that.” On the Labour right, Progress, he notes, does exactly the same thing. “Half a million members could be the key to our success,” he says. “They can take our message to millions. But they want to shape policy, too. I wouldn’t call giving them a greater say ‘taking over the party’” – and this is surely unanswerable – “it’s theirs to start with.”

Correction: This article originally named Luke Akehurst as a Labour councillor. Akehurst stood down in 2014.

This article first appeared in the 23 March 2017 issue of the New Statesman, Trump's permanent revolution