The Best Australian Science Writing 2012 (5 page)

But as no word came, the countdown was again stopped, at the T minus five minute mark. There it held. Finally, with time running out, NASA engineers received a call saying the glitch was resolved. They resumed the countdown, and at exactly 4.53:24 pm – with just three seconds to spare –
Discovery
blasted off.

When the engines ignited, there was a blinding flash and the whole structure began edging upwards. At first it seemed to gently hover above the launch pad. This was an illusion; it was actually rapidly accelerating, and within a split second was punching through the air, riding an eye-searing waterfall of white-hot flame as it tore into the clear blue sky.

I'd waited for decades to see it, and had watched countless shuttle launches on TV, but still, my mind found it hard to accept
what I was seeing. A building 19 storeys high was rising effortlessly into the air, trailed by billowing clouds of superheated steam that raced away in all directions. The plume of flame spewing from the solid rocket boosters was incredibly bright – almost like looking at the Sun. Nothing had prepared me for that.

And the sound. It's hard to describe: a rumbling growl so low it reaches into your stomach, with a resonant thundering of pops and bangs that quickly overwhelms the cheering, whooping and rapid-fire camera shutters going off around you. There is a moment – 50 or so seconds in – when the sound is completely overwhelming, seemingly on top of you, and silence descends on the crowd.

My pulse was racing and I found myself watching openmouthed. It did not close again until two minutes into the flight, when the shuttle had ditched its twin solid rocket boosters 48.7km above us. Curling clouds of steam marked its trajectory, and the orbiter – its engines now burning fuel from the attached external tank – was a tiny white speck in the deep blue sky that, eventually, vanished. My senses told me something very large and very powerful had growled to life nearby, done something incredible, and all I could do was stare after it, transfixed.

It had been a remarkable show.
Discovery
was on its way, and its engines would continue firing for another six minutes before the tank was drained and fell away, to burn up on re-entry. It would loop the Earth several times over the next two days, working its way through complicated orbital dynamics, before gently docking with the International Space Station.

‘The shuttle program … has given us a lot … and it has taught us what is needed for the routine access to space,' Andy Thomas, the Australian-born NASA astronaut who flew aboard
Discovery
in three of his five flights, told me in an email. ‘But that has come at a significant cost, both financial and human.

‘We now recognise that the shuttle technology, while brilliant
in what it can do, is very fragile, costly to maintain and unforgiving to mistakes. So it is time to retire it and move on.'

History

Relics

Neutrinos and the speed of light … not so fast

Jonathan Carroll

The bartender says, ‘We don't serve your kind in here' …

A faster-than-light neutrino walks into a bar.

* * * * *

The media is champing at the bit to proclaim a discovery of faster-than-light travel by a subatomic particle known as a neutrino, with some going as far as claiming ‘Einstein was wrong: relativity theory busted.' Startling stuff. If it's true, then time travel – the stuff of science fiction – may be for real. The scientists responsible for the experiment and analysis let slip that they have some preliminary data that suggests that these particles travel faster than light, but they seem to be the only ones
not
jumping to conclusions just yet. The team at the Oscillation Project with Emulsion-tRacking Apparatus (OPERA) in Gran Sasso, Italy – a laboratory sheltered from cosmic rays 1.4km beneath Gran Sasso, the highest peak of the Apennines – regularly detects neutrinos emitted from the Large Hadron Collider (LHC) in Switzerland, 730km away. Neutrinos, which are electrically neutral subatomic particles, are indifferent to the presence of trivial things such as
Earth and zip through without so much as a passing interest. Owing to their small mass they should do so at approximately the speed of light (
c
), the speed light travels in a vacuum, known quite well to be 299,792,458 metres per second.

Using GPS timing and position data, the OPERA team claims to know the distance between the point at which neutrinos are emitted from the LHC and the point at which they are detected in Italy to a precision that allows them to predict the neutrino's arrival time to within 10 nanoseconds (a nanosecond being a billionth of a second).

What they claim to have found, though, is neutrinos arriving 60 nanoseconds (0.00000006 seconds) early. If accurate, this would be a six standard-deviation result – enough to convince physicists that something is genuinely awry. The scientists concerned have released the findings to the scientific community in the hope that, if something has been overlooked, it will be picked up by their peers. The peer-review process is usually quite efficient at eliminating likely sources of error, and in this case there are plenty of possibilities. But on the face of it, it seems the OPERA team has been very careful.

There's the issue of knowing the exact positions of the source and detector to within the quoted uncertainty – keeping in mind that in the extra 60 nanoseconds the neutrinos are supposedly travelling, they will cover a total of 18 metres. This means knowing those two positions – and the geodesic distance between them (the ‘straight' line they follow is actually a straight line in curved space thanks to General Relativity and the mass of the Earth) – to within 3 metres out of 730,000 metres. Though traditional civilian-grade GPS has an accuracy of about 15 metres, the OPERA experiment used the top-of-the-range technology known as ‘carrier phase tracking', which offers better than 1 centimetre accuracy over 730,000 metres. However, it still requires the GPS antenna to be above ground, so one also needs to take into
account the timing for signals to travel along wires to the underground experiments. For this purpose, the OPERA scientists also made use of a cesium atomic clock. Overall, the accuracy they achieved was 20 centimetres out of 730,000 metres – well within the required range.

Presuming for now all the possible sources of error are accounted for, what would this result mean? Time-travel seems to be the go-to topic when faster-than-light particles are mentioned, but don't hold out hope for a TARDIS just yet.

If a particle is able to travel faster than
c
, a few odd things happen. Critically, it breaks
special relativity
, which states that there's an absolute speed limit – the speed at which massless particles travel – that doesn't depend on relative motion. One practical aspect of special relativity is that the concept of ‘simultaneity' – two things happening at the same time – is frame-dependent. If two events occur at the same time but at different locations, say flashing a torch, then depending on how you are travelling relative to each of those events, you may see them occurring at different times. For instance, if you are accelerating relative to one then you will see it occur later, as if time is slowed.

Now let's have a machine that turns on two torches at the same time. If the first of those is a normal torch and the second emits faster-than-light luminous particles, then from a distance you might think that the second torch was turned on first because you saw it first, even if you aren't moving relatively – it's as if it was turned on in the past. So the particles can appear to travel back in time (hence the backwards ordering of the joke about the neutrino entering a bar) … but there's still no method of accelerating a cyborg killing machine to super-luminal speeds.

Is the latest potential finding an isolated incident? Apparently not. In 2007 the MINOS experiment, located in the US and with a similar source-detector distance to the CERN-OPERA path, observed the same thing, albeit with a smaller significance
(1.8 standard deviations – not enough to get excited about) and a larger error (allowing for neutrinos travelling exactly at
c
). Measurements of arrival times of photons and neutrinos from supernova SN1987a in 1987 provided a much better agreement with the speed of light, but those neutrinos were of a much lower energy. The possibility remains that the velocity of a neutrino depends on its energy. Somewhat less rigid explanations include neutrinos taking ‘shortcuts' through extra dimensions. Undoubtedly many more possible explanations will arise if all conventional sources of error are excluded.

The much more likely scenario is that the analysis has overlooked some seemingly insignificant but critical aspect, and that re-analysis will lead to a very good agreement with the speed of light.

Should that be the case, the follow-up press release will no doubt refer to the ‘Phantom of the OPERA'.

Postscript: 1 May 2012

For every complex phenomenon there is an explanation which is simple, concise, and wrong. The OPERA faster-than-light neutrino article generated a flurry of explanations, both online and within the scientific community, claiming to resolve the problem via strange new mechanisms. In the end, a loose coupling in the GPS wires mentioned in the above article was found to be responsible for the apparent velocity increase.

Even though the OPERA team was agnostic to sources of error, and announced their findings expecting that they would be proven wrong, the fallout has been dramatic. The two OPERA scientists in charge of the collaborative experiment, spokesperson Antonio Ereditato and physics coordinator Dario Autiero, resigned from their posts following a vote of ‘no confidence'. The timing of the signal travelling between the surface GPS and the underground detector was measured originally by Autiero in
2008, but was not rechecked recently. Doing so would likely have implicated the loose connection and forced a re-evaluation of the spurious data before making it public.

Since then, the ICARUS experiment (also based at Gran Sasso) has confirmed the neutrino speed as matching the speed of light to very high precision, a confirmation that would have also prevented the premature publication of the OPERA results.

The widely varying mechanisms invoked to explain how neutrinos could travel faster than light will no doubt be shelved until the next anomaly. In an ideal world the vanishing of such a discrepancy would serve as a constraint on wacky theories, but in reality the goal posts are too often moved to suit specific purposes. Experimental errors are an ever-present ‘unknown' in any facility, and events like this should leave us even more impressed with the enormous precision and sensitivity of experimental efforts like the LHC.

More importantly, we should continue to suspect horses, not zebras, when we hear hooves.

Strange physics

Travel

Blank canvas

Corey Butler

Walking up to the flowering mallee growing in the red dirt of South Australia's Bon Bon Station Reserve, I was so amazed by the amassed hum of thousands of native bees that I didn't notice the brightly coloured beetle perched on one of the flowers.

When the insect did finally catch my eye, I took a quick snap of its shiny shell before returning my focus to the bees flocking around on the small tree (
Eucalyptus socialis
).

It wasn't until I returned that night to the shed where the team of scientists and naturalists were based, and showed entomologist Andy Young the picture of my ‘cute beetle', that realisation hit us: I'd come face to face with a new species of beetle. And let it go. He looked at me as if I'd won the lottery, but lost the ticket.

In my defence, I had tagged along as an observer, to document the week-long biodiversity field trip arranged by Bush Heritage Australia, a non-profit organisation seeking to protect flora, fauna and habitats.

* * * * *

Dubbed a ‘biodiversity blitz', it was a large-scale effort to collect and classify as many species as possible. No one had asked me to keep an eye out for new beetle species.