Why do we think Pluto and Eris may be half-finished planets? The evidence comes mainly from computer simulations of planet formation carried out at such institutions as the Southwest Research Institute, in Boulder, Colorado. They demonstrate that Earth-sized objects could, indeed, have formed in the outer regions of the Solar System. Why the process stopped is a mystery. But if Pluto really is a half-built planet, a close look at it would give us a unique opportunity to see planet formation in freeze-frame, providing real insights into the process.
What was obviously needed was a robotic space mission to Pluto. But there’s a catch – and it’s not just the extreme distance involved. Pluto’s elongated orbit means the energy it receives from the Sun falls by a factor of three as it moves from perihelion (its closest point to the Sun) to aphelion (its furthest point) in its 248-year orbit. Perihelion occurred in September 1989, so by early in the 21st century the planet was already well on its way towards the zone in which its thin atmosphere will simply freeze onto its surface. And there was already evidence of seasonal changes in Hubble Space Telescope observations of Pluto’s surface markings. The sooner we could get to Pluto, the more informative and interesting it would be.
Towards a new horizon
On 19 January 2006, a long-cherished dream came true. A Plutobound robotic spacecraft called New Horizons was successfully fired from Cape Canaveral in Florida, using the Lamborghini of launch vehicles – an Atlas V rocket with some serious go-faster accessories. If we were going to start travelling to Pluto in 2006 on a timescale that would give us the best chance of investigating its atmosphere, we needed to get there as quickly as possible – and New Horizons broke all the records, leaving Earth at the highest launch speed ever achieved. It crossed the Moon’s orbit in only nine hours and whizzed by Jupiter after little more than a year, the close encounter with the giant planet increasing its speed to a remarkable 23 kilometres per second. After years of planning –and a few false starts – humankind was at last on its way to Pluto.
The reliability of orbital mechanics means we can predict with pinpoint accuracy when New Horizons will reach Pluto. It will fly by the frozen world at 11.47 Greenwich Mean Time on 14 July 2015, passing Charon 14 minutes later. Because of its speed (the close approach will take place at nearly 14 kilometres per second) there is no possibility of New Horizons being diverted into orbit around Pluto, so the 0.5-tonne spacecraft bristles with sensors to take full advantage of its brief encounter. They include spectrometers to analyse the barcode of information locked up in Pluto’s rainbow spectrum, subatomic particle detectors, a long-range camera and an instrument named the Venetia Burney Student Dust Counter, which will provide valuable information on the levels of interplanetary dust in the outer Solar System. The fly-by should allow detailed mapping of Pluto and Charon, as well as collection of telltale data on their surface and atmospheric composition. Alongside all the high-tech robotic sensing equipment, New Horizons also carries a poignant reminder of its place in human history. On board is a container carrying 28 grams of the ashes of Pluto’s discoverer, Clyde Tombaugh, who died in 1997.
It’s hard to overstate the importance of New Horizons, since our first-hand knowledge of Pluto and its environment is so sparse. The results could be the most surprising of any deepspace mission yet, notwithstanding the extraordinary discoveries about Saturn and its moons that have been made by the highly successful Cassini mission since it reached the planet in July 2004. But with New Horizons going on to target selected Kuiper Belt objects after its Pluto fly-by – and then escaping from the Solar System altogether – the excitement of new discoveries may continue well into the century.
Controversially, New Horizons carries 10.9 kilograms of radioactive plutonium dioxide to provide thermoelectric power for its onboard instruments. There is little alternative to this, given that the intensity of sunlight at Pluto’s distance is only one-1000th of that which we receive on Earth, rendering solar panels useless. But you won’t be surprised to hear that this was not the only controversy surrounding the Pluto mission.
Dwarfed by controversy
Just seven months after New Horizons was launched, the IAU held its much-vaunted General Assembly in Prague. Its latest planet definition committee had agreed on a draft specification of what constitutes a planet, and this was receiving substantial press coverage. To be a planet, the committee suggested, a celestial object needed to be in orbit around a star and large enough for its own gravity to pull it into a spherical shape (a condition technically known as ‘hydrostatic equilibrium’). This definition significantly extended the inventory of planets in the Solar System, since both Eris and the largest asteroid, Ceres, qualified. Moreover, there would be a significant likelihood of more to come as the exploration of the Solar System’s twilight zone revealed further Eris-like objects.
Shut away from the glare of the waiting media, the membership of the IAU met on the General Assembly’s final day to vote on the recommendation. But an intense debate yielded a revised definition subtly different from the committee’s in that it included an additional criterion. To be a planet, went the revised version, a celestial object also had to be the dominant object in its neighbourhood, having cleared away smaller debris either by absorbing it (as the Earth does with thousands of tonnes of meteoritic dust per year) or by ejecting it through gravitational forces. Any object that hadn’t done this, despite meeting the spherical shape criterion, would be termed a ‘dwarf planet’ rather than a ‘planet’. What that meant in practice was that an object in the main Asteroid Belt, between Mars and Jupiter, or in the Kuiper Belt could not be a planet.
When the vote on this revised definition took place it was passed with an overwhelming majority. It was adopted by the IAU as Resolution 5A of the Prague General Assembly. Thus, on 24 August 2006, the world was given, for the first time, a formal definition of a planet – and it did not include Pluto. The former ninth planet, along with Ceres, Eris and two other Kuiper Belt objects, Haumea and Makemake, had become a dwarf planet.
If there had been any doubt about the public’s interest in what constitutes a planet it was quickly dispelled by the outcry that followed. The headline I liked best appeared in a Newcastle (New South Wales) article: ‘Pluto dumped by the übernerds of Prague’. Not just the nerds, mark you, but the ‘übernerds’. Similar sentiments echoed around the world, especially in the USA, from where the former ninth planet had been discovered. There, protest marches were held in some cities.
It was a long time before the outrage subsided, and even then it didn’t do so before three US states had attempted to introduce legislation to reinstate Pluto as a planet. Only one of them, Illinois, succeeded, demonstrating that if you don’t like a scientific outcome you can always legislate to overturn it. Significantly, Illinois was the state in which Clyde Tombaugh was born. And on the lunatic fringe there are still conspiracy theory websites that point to the fact that the IAU’s decision was taken on the final day of its General Assembly, when only one-sixth of the attending membership was still present (producing 424 votes). They cry foul, citing rogue scientists and vested interests. They also conveniently ignore the fact that at the IAU’s next General Assembly, held in Rio de Janeiro in 2009, there was no change of heart on the issue.
One consistent voice of reason in the debate has been that of Alan Stern, formerly of the Southwest Research Institute. Stern is principal investigator with New Horizons, and you have to have some sympathy for his view. When his spacecraft was launched, it was on its way to a planet – but now it isn’t. Stern has criticised the IAU’s resolution, calling it ‘an awful definition; it’s sloppy science and it would never pass peer review’. He cites the fact that several of the Solar System’s planets, including the Earth and Jupiter, have not entirely cleared their neighbourhood of debris and therefore do not strictly meet the new criteria for planethood. Perhaps in deference to this view, the IAU executive committee announced a new type of celestial object in June 2008 – the ‘plutoid’, w
hich is basically a dwarf planet in an orbit beyond Neptune. Currently, Eris, Pluto, Makemake and Haumea are the only known plutoids, but it is very likely that, as observations improve, other Kuiper Belt objects will turn out to be spherical and therefore qualify. The plutoid’s definition, too, has been widely criticised, but this time because the term sounds too much like an unpleasant skin complaint.
My own view is that, while I agree the IAU’s definition of a planet is not perfect, it’s a lot better than what we had before – which was essentially nothing. The reclassification of Pluto shows science in action, as researchers come to terms with new information and act appropriately upon it. To have done otherwise would have been to deny what nature is telling us.
Classification
Cast out
Explosive
Many-worlds quantum mechanics vs earth-based grease monkeys
gareth roi jones
Quantum mechanics
(those most dizzyingly complex
of celestial craftsman)
allow small particles
(electrons, atoms, & whatnots) to exist
in a ‘superposition of states’
in opposition to what we observe
in our ‘real’ daily earth-based life
where things are in one state or another
a coin is either heads or tails after flipping
not both
a car is either moving or stationary
not both
a bill is either reasonably priced for the services rendered
or from a qualified mechanic
not both
Schrödinger disliked this superposition notion
& posited the paradox of the entangled cat
callously trapped, unobserved, in a sealed steel chamber
alongside a potentially broken flask of hydrocyanic acid
both dead & alive at the same time
challenging the counter-intuitiveness
of the mathematics behind quantum states
in a classic case of reductio ad absurdum
(however, his position on exorbitant repair bills is, sadly, not recorded)
the only moral I can draw is this:
where possible don’t get a real grease monkey to fix your car
always go for an Austrian physicist
Dead and alive
Paradox
The vagina dialogues
Cordelia Fine
In every healthy young man the instinct of sex is present, controlled or allowed to run riot according to his strength of self-control and elevation of mind. Some young women possess it in as great, and in rare cases even a greater degree; but in the majority of healthy women before marriage it lies in a more or less dormant condition, and occasionally is altogether absent. – Margaret Stephens, Women & Marriage: A Handbook (1910)
My nine-year-old son recently found the DVD case for a documentary that explores positive celebrations of female sexuality in India, Cuba, China and Uganda. He read out the title, The Sunny Side of Sex, then asked me: ‘Is there a stormy side too?’
‘Oh, yes,’ I replied.
When Rebecca Jordan-Young, a socio-medical scientist at Columbia University, interviewed psychobiological researchers of sex differences, she was repeatedly told that ‘masculine and feminine sexuality are simply “common-sense” ideas’. As one scientist told her: ‘Most people … don’t have any problem understanding that male sexuality is different from female sexuality. It’s a no-brainer’.
Yet, argues Jordan-Young in her recent book Brain Storm, ‘from this side of the sexual revolutions of the 20th century, it is easy to lose track of just how much has changed, and how rapidly’. As she shows, only 30 or 40 years ago scientists categorised so many sexual behaviours as distinctly masculine – the initiation of sex, intense physical desire, masturbation, erotic dreams, arousal to narratives – that it was hardly an exaggeration to say that ‘sexuality itself was seen as a masculine trait’. The psychobiologists’ account of normal female sexual feelings and behaviour all but rendered ‘female sexuality’ an oxymoron. Female sexual imagination was restricted to ‘wedding fantasies’ (presumably not of an ‘Ooh, Reverend!’ variety). As for tens of millions of women finding sexual titillation in Fifty Shades of Grey, to the psychobiologists of the time, this would have indicated an epidemic of abnormal sexuality on a catastrophic scale.
A 1968 scientific report captures the romanticism, passivity, emotionality and exclusivity ascribed to female sexuality. Women, the authors assumed, don’t experience anything so crude as genital arousal ‘such as might lead to masturbation in the absence of a partner’, but rather a ‘sentimental arousal … which leads to romantic longing for the loved one alone and which will, in his absence, require waiting for his return’.
The researchers were exploring the idea that testosterone permanently ‘masculinises’ the brain in utero, resulting in ‘male’ and ‘female’ brains with distinct sexualities (as well as divergent interests and skills). However, the ‘common-sense’ notions of the feminine and masculine sexualities that testosterone differences might explain shifted, presumably in belated response to changes in attitudes and behaviour sparked by the 1960s sexual revolution. From the 1980s onwards, elements of bodily desire and agency – like genital arousal and libido – became common-sense features in scientific models of human, rather than male, sexuality. Yet the changes went unremarked by the researchers, who didn’t draw attention to, or most likely even notice, the fact that the male and female sexualities supposedly explained by in utero testosterone had significantly changed. This meant that the psychobiologists ‘reinforced the notion that “masculine” and “feminine” sexuality are universal, timeless constructs and created the illusion of a seamless line of evidence supporting human sexuality as hardwired by hormones’.
* * * * *
The X-rated gender gap remains today and, as with the gaps in, say, science, politics, business or child care, many claim that it’s an inevitable consequence of essentially different male and female natures. Evolutionary psychology has provided one well-known explanation. Because females bear the substantial biological costs of nutrient-rich eggs, gestation, birth and lactation, their reproductive potential is mostly constrained by access to the material resources and support they need to rear a relatively limited number of young. Women therefore do best if their mating strategy is to seek a good provider within a committed relationship. This strategy can work for men, too, but unlike women they can score reproductive wins in casual sexual encounters, from which they walk away having invested only a little time, some pleasurable effort and a mere teaspoonful or so of sperm. And so, this kind of account claims, men evolved a sexual nature more powerful, persistent and promiscuous than that of women.
Although the majority of gender differences in sexual behaviour and attitudes are small, the exceptions seem broadly consistent with received ideas. For example, women report sexual desires that are, on average, less frequent and insistent, and they are approximately twice as likely as men to report that they take little interest or find little pleasure in sex. This difference is prominently illustrated on the cover of sex therapist Bettina Arndt’s book The Sex Diaries. A man sits with folded arms at the leftmost edge of a bed and looks with frustration at the stop sign held by his female partner, who is positioned far right and wears an expression of beleaguered irritation. It’s an instantly understandable visual reference to the ‘fragile, feeble female libido’ that is such a poor match for his ‘constant sparking sexual energy’. An early diary entry by one of Arndt’s volunteers, Nadia, a married mother aged 41, captures it concisely: ‘My sex drive is zero and I really only do it for him’.
Women also report engaging less often in sexual activities that are largely bereft of emotional intimacy, such as masturbation, pornography use and casual sex. But although this is consistent with the idea that emotional context is more important for women, enjoying sexual pleasure for its own sake is stigmatised for fem
ales, and this may lead to under-reporting. For example, women who thought they were attached to a lie detector admitted to significantly more masturbation and pornography use than did women who weren’t hooked up to the bogus machine, and who thought their responses might be seen by someone else. (Similarly, that men apparently engage in more casual sex with women than women do with men is a longstanding mathematical mystery, the solution to which may well also lie in creative self-reporting.)
So thoroughly relationship-embedded is female sexuality often thought to be that hopeful heterosexual partners are advised by sex therapists that ‘foreplay is everything that happens in the twenty-four hours preceding penile insertion’, according to Louann Brizendine, author of The Female Brain. True, one can’t help but think this might be a helpful perspective for those performing at absolute rock-bottom. In The Sex Diaries, for example, Nadia’s husband describes, in the very same diary entry, both Nadia’s discovery that he has been masturbating to pornography in his truck when he hands over his semen-soiled jumper for her to wash – a gesture difficult to rival as the antithesis of romance – and his irritation at her lack of sexual interest in him. (Interestingly, when Nadia’s husband goes away, with the help of a vibrator her sex drive accelerates rapidly from ‘zero’.)
The Best Australian Science Writing 2013 Page 13