“YOU ARE AWASH IN WAVES OF SPACETIME”
KATIE MACK — ASTROPHYSICS
EVERY MORNING SEEMS to bring news of a new medical danger. Some health scares fizzle fast, but others look like they will never run out of fuel. How can we make sense of them without turning into quivering neurotics?
With baby boomers pushing 70, dementia scares are becoming more common. Take recent warnings about mercury in fish. People are eating more fish to ward off heart disease. But could mercury trigger brain changes that lead to dementia? To check it out, researchers at Rush University Medical Centre in Chicago studied the brain tissue of deceased elderly people to look for a link between mercury levels and brain plaques, a sign of Alzheimer’s disease. The good news: they found no link. Even better, a paper in the Journal of the American Medical Association in February 2016 showed eating fish reduced brain plaques in people whose Apoe4 gene put them at high risk.
Another dementia scare grabbed headlines in February, when German researchers found a link to commonly prescribed heartburn medications. The drugs are called proton pump inhibitors, or PPIS. (Their generic names end in prazole – omeprazole and esomeprazole are two examples.) At first glance, the results look disturbing. But, as with any scare, level-headed questions need to be answered before people with heartburn succumb to panic. First, does it make biological sense that PPIS could cause dementia? Maybe. But there should be a dose-response effect: the higher the dose or the longer a person takes the drugs, the more likely the onset of dementia. No one has shown that is the case. There are also alternative explanations for the link. For example, people who have heartburn and take PPIS tend to be older, fatter and are more likely to smoke than people who don’t take these drugs. Those factors may put them at risk of dementia – not the drugs themselves.
The case demonstrates the classic danger of assuming that events that are correlated – taking PPIS and developing dementia – are causally related. Other health scares flourish when there is not even a clear correlation. For example, take the fears of a link between mobile phones and brain cancer. That radiation emitted from phones could be zapping our brains sounds plausible. But the story fizzles out when you examine the evidence. We know the dates when mobile phones came on the market and have ample data on usage patterns. If phones raise brain cancer rates, there’s been enough time for the dial to have shifted. It hasn’t. Reviews of studies looking for a link between mobile phones and brain tumours also show different results depending on the methodologies used. So the science is inconsistent. There is no basis to even start to assess a dose effect. These days people are more likely to be texting, taking photos or using ear buds than clutching their phones to their heads, further complicating the data. Another question is whether it is biologically plausible for mobile phones to cause cellular damage: in contrast to X-rays, the wavelengths mobile phones emit are too weak to trigger cancer.
My point here? It’s not that we should ignore the possible risks of mercury pollution, overuse of PPIS or mobile phones. But these cases demonstrate how people can bark up the wrong tree. Why worry about unproven scenarios that might, at best, account for tiny risks, when the greatest proven risks are obesity, alcohol and being a couch potato – which are all preventable.
Research by psychologists such as Nobel laureate Daniel Kahneman and his late colleague Amos Tversky suggests that we happily swim in a sea of risk – for instance we seldom think twice about getting into a car despite the staggering number of injuries and deaths they cause. Yet for many folks, flying sends the fear barometer off-scale though it’s a far safer way to travel. Our emotional response tends to be heightened if we feel we have no control over our exposure, or if a giant conglomerate profits from the activity.
We will never be rid of scares. Nor should we, because sometimes they do uncover a real threat. But as Kahneman suggests in his book Thinking, Fast and Slow, we need to slow down and consider what matters more rationally.
WE SELDOM THINK TWICE ABOUT GETTING INTO A CAR DESPITE THE STAGGERING NUMBER OF INJURIES AND DEATHS THEY CAUSE.
Warning: scare stories need to be taken with a grain of salt.
Prepare for the unveiling of the invisible Universe.
YOU MAY THINK YOU ARE sitting still, peacefully reading this column. In fact you are awash in waves of spacetime that periodically stretch you and squeeze you this way and that. Born in distant cosmic cataclysms, these waves travel through the Universe like ripples on a pond.
On September 14 last year we caught our first glimpse of one: a ripple emitted more than a billion years ago by the merging of two massive black holes. Historic though this was, that signal, recorded in the impossibly tiny motions of mirrors in the Laser Interferometer Gravitational-wave Observatory (LIGO) experiment, was merely the beginning.
Just as light’s electromagnetic spectrum stretches from high-energy gamma rays to languid radio signals, gravitational waves also span the range from high to low frequencies. And just as we have telescopes tuned to pick up the entire electromagnetic spectrum, so too tools are being developed to span the gravitational wave spectrum and usher in the era of gravitational wave astronomy.
LIGO, with its mirrors placed four kilometres apart, can pick up the highfrequency end – it’s optimised for waves whose crests pass by at 10 to a 1,000 times per second, that is 10 to 1,000 Hz. Waves in this frequency can be generated by a pair of fast-circling neutron stars or a relatively small pair of black holes on the brink of merging. Humans can hear soundwaves in this frequency range, which is why the quick-rising waveform that LIGO detected is referred to as a “chirp”. An even higher-frequency gravitational wave would be generated by a supernova (an exploding star) and would also be detectable at the very upper range of LIGO’S sensitivity.
But the ripples that make up the constant low hum of spacetime occur at lower frequencies. Some are generated by non-merging binary systems, many of which reside in our own galactic backyard. Pairs of neutron stars and white dwarfs circling at a leisurely pace produce gravitational waves from once a second to once in several hours. These frequencies are too low, and thus their wavelengths too long, to be detected with LIGO. To pick up longer wavelengths, longer arms are needed: ELISA, with mirrors a million kilometres apart, will be up to the task. This space-based version of LIGO, with a set of mirrors orbiting the Sun in a triangular configuration, is set to be launched in 2034.
Such a space-based instrument could also detect mergers between supermassive black holes, which produce lower frequencies than the merely massive black holes recently detected by LIGO. Since every large galaxy (including our own) seems to host a supermassive black hole in its centre, picking up this kind of signal will allow us to watch galaxies grow by consuming one another in the distant Universe.
At even lower frequencies of one crest per 10s of years, we may be able to detect the most massive of supermassive black holes as they orbit each other before merging, giving us even more insight into the growth of galaxies. To do this, we let the Universe build our instrument for us: a pulsar timing array. A pulsar is a collapsed, fast-spinning star that, like a cosmic lighthouse, emits regular pulses with each rotation. Their rotation is so regular that their pulses are the most accurate clocks in the Universe. By stretching and shrinking the space between pulsars and Earth, low frequency gravitational waves can change pulse arrival times. So in theory when these clocks lose their timing, that’s the hallmark of a gravitational wave.
These pulsar timing arrays should also allow us to pick up primordial gravitational waves left over from the Big Bang. They are still permeating the cosmos as ultra-long, ultra-low-frequency waves in spacetime, stretched out by the expansion of the Universe. In 2014, a microwave telescope called BICEP2 seemed to find swirly traces of these waves imprinted in the left-over radiation from the Big Bang. These swirls turned out to be dominated by Milky Way dust. But the waves might still be hidden there, waiting for our experiments to do a better job of teasing them out.
Our exploration of the invisible Universe with gravitational wave astronomy is only beginning, but its future looks bright.
A SPACE- BASED INSTRUMENT COULD ALSO DETECT MERGERS BETWEEN SUPERMASSIVE BLACK HOLES.
“TOMORROW CAN BE a wonderful age. Our scientists today are opening the doors … to achievements that will benefit our children and generations to come.” So proclaimed Walt Disney in 1955 when he launched Tomorrowland amidst friendly robots and rocket backpacks.
Disney’s timing was auspicious. That same year the polio vaccine put an end to the scourge that paralysed or killed half a million people each year. We also got the atomic clock (paving the way to GPS satellites) and Velcro. A year later came videotape, the hard disk and the national nuclear power grid. Two years later, Sputnik was launched. Could robots be far behind?
The 21st century is not shaping up to be quite as sunny as the one imagined at Tomorrowland. The latest worry is that robots who are smarter and stronger than us might take over the world if we don’t watch out.
It’s not just luddites who worry. The latest angst comes from some of the most technologically savvy men on the planet. At last year’s World Economic Forum at Davos, so concerned were Spacex and Tesla founder Elon Musk, Peter Thiel of Paypal and other Silicon Valley entrepreneurs that they personally committed $1 billion to funding “Open AI” a new non-profit company that proclaims Artificial Intelligence should remain “an extension of individual human wills”. They were supported by astrophysicist Stephen Hawking who has expressed concern that “the development of full artificial intelligence could spell the end of the human race”. Bill Gates also told startled reporters: “I am in the camp that is concerned about super intelligence.”
If Bill Gates is worried, shouldn’t we all be? And given the level of concern, how adequate is the response? To find out, I looked up some of the institutions that share Hawking’s concern about the potential dangers of AI. They are the Cambridge Centre for the Study of Existential Risk, the Future of Humanity Institute, the Machine Intelligence Research Institute and the Future of Life Institute. All of these impressively named bodies are linked – the same people are on the boards, and they are funded by the same people.
It is good that such boards exist, but most of the researchers and board members are older white men. There are nine women in total, out of 120 people at all the institutes, as well as one Asian man (at the Future of Humanity Institute) and one person of colour (actor Morgan Freeman at the Future of Life Institute Science Board).
So here is one of my reservations. Open AI may seek to be “an extension of individual human wills”. But whose wills are represented? One of the women who is not on these boards is bioethicist Justine Cassell. She notes that most concern about the robot takeover comes from supercompetitive power-hungry men whose expertise is quite far from the AI field.
She wonders if they are afraid of robots made in their own image. But there is another narrative. A movement called UBI – Universal Basic Income – once advocated by socialists, is now embraced by Silicon Valley entrepreneurs. They look forward to a future where intelligent machines not only power the economy, they do all the dangerous and mindnumbing jobs, leaving humans the time for leisurely and creative pursuits.
We need to design artificial intelligence with a full understanding of what is at stake. In Cassell’s words “since we make the robots, we can make the future”. We are moral agents, not helpless observers.
AI is our collective brainchild. And it takes a village to raise this powerful, smart and growing kid. Rules will be needed, and curfews set. But too much fear blinds us to the possibilities that intelligent machines may allow – a future where jobs of drudgery, mechanical complexity, and danger are no longer a part of human existence. We need an inclusive discussion to find the right parenting balance.
And as Cassell reminds us, unlike human children, with these kids you can always pull the plug.
WE NEED TO DESIGN ARTIFICIAL INTELLIGENCE WITH A FULL UNDERSTANDING OF WHAT IS AT STAKE.
We need to set boundaries and rules on artificial intelligence.
EVERY TIME SCIENTISTS DEVELOP A BETTER ... MEASUREMENT INSTRUMENT, IT PROVIDES NEW INSIGHTS.
Gravitatioonal waves give us an exciting new way to view the Universe.
IF YOU WERE A GAMBLER you would wonder at the extraordinary conflux of events. After eight years in development, Advanced LIGO began its search for gravitational waves in September last year. One hour later, it recorded the definitive detection of gravitational waves.
Another coincidence: it happened 100 years after the publication of Albert Einstein’s Theory of General Relativity, which predicted the waves in the first place. But it was more than luck, it was brilliant science and engineering, and that day, Thursday 11 February 2016, will be forever etched on my mind.
There have been other major discoveries in physics and confirmations of predictions in my lifetime – black holes, dark matter, dark energy and the Higgs Boson, for example.
I pay homage to them all, but somehow they crept up on me without the fanfare of the gravitational waves event, the crescendo of which lasted just one tenth of a second, the moment when two massive black holes collided, manifested as a single oscillating blip on a computer screen.
There are three reasons for my excitement. First, gravitational waves are the final prediction to be verified from Einstein’s theory. Every other one has been proven again and again with ever increasing accuracy.
General Relativity offered a new explanation of gravity. Rather than being a force as Newton viewed it, it was a distortion in the fabric of space-time. With this final piece of evidence, the theory now appears rock solid and – bizarre as it seems – will forever be an accurate descriptor of physics from the molecular to the cosmological scale.
In December 1999, Time magazine named Albert Einstein the Person of the Century. To me, he is the Person of the Millennium.
Second, and best of all, there is the promise of more to come. Modern astronomy started when Galileo picked up an optical telescope in the early 1600s. It wasn’t until the 1930s that the radio telescope was invented and eventually used to discover pulsars, quasars and the cosmic microwave background radiation. That’s it – two types of telescope. Until now.
Gravitational waves were discovered with two LIGO detectors in the United States – not enough to determine the direction the gravitational waves came from. But in future, three or more LIGO detectors will constitute a gravitationalwave telescope, giving us a third routine way to observe the Universe.
Every time scientists develop a better microscope or measurement instrument, it provides new insights. LIGO will be no exception; there will be many more discoveries in the coming years.
Third, as an engineer I marvel at the LIGO instrumentation.
Einstein did not think that we would be able to build instruments sufficiently sensitive to detect gravitational waves. Even 10 years ago it seemed impossible. But that did not daunt the physicists, engineers and mathematicians in the LIGO team.
They built a giant detector in which laser beams bounce between the mirrors at each end of two intersecting, vacuum tunnels, each four kilometres long. Changes in the length of the tunnels, as gravitational waves shimmy through, are measured by the way the laser beams interfere with each other.
The detected length change was less than a thousandth of the width of a proton – so infinitesimal it is difficult to conceive. If we imagine that the tunnels of LIGO run the length from here to the nearest star system, Alpha Centauri, 4.4 light years away, it would be like measuring fluctuations across that distance to less than the width of a single human hair.
Future generations will look back on the timeline of human history and see the bright mark etched on Thursday 11 February 2016. They will have incredible new tools at their disposal and fantastic new knowledge. I have no doubt their zeal to continue pushing back the frontiers of the Universe will remain undiminished.