May the force not be with you: Sandra Bullock goes for a spacewalk in Gravity. Photo: Warner Bros
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In search of the notorious Big G: why we still know so little about gravity

Gravity is pathetic and so is our understanding of it.

Gravity is pathetic. The Oscar statuette, for instance, has a mass of 3.85 kilograms but it is pulled down to earth by a force so weak that you can buy a £2.99 fridge magnet that can beat it. It’s shameful that the gravitational pull of the entire earth can be overcome by a cheap piece of magnetised steel.

Gravity is by far the weakest of the fundamental forces of nature (the fridge magnet puts the far stronger electromagnetic force to work). It is so weak that its strength is proving difficult to measure accurately. In late February, while Alfonso Cuarón, the director of the sci-fi film Gravity, was on tenterhooks waiting for the Oscars result, the world’s experts on gravity assembled just outside Milton Keynes in an attempt to sort out this most embarrassing problem.

Numbers such as the strength of gravity, the speed of light and the charge on an electron are known to physicists as the “fundamental constants”. They are in some ways the sticking plaster of physics. We can explain the origin of most things but we know the values of the fundamental constants only by measuring them – there is no way to work them out from a theory.

These days, most are very well defined – but not gravity. It is the only fundamental constant for which our uncertainty over its value has got worse over the years.

The gravitational constant is sometimes known as “Big G”. This differentiates it from “little g”, which describes how fast things accelerate towards Planet Earth when free to fall. The first accurate measurement of Big G was made in 1798. Henry Cavendish used a torsion balance, a device in which two lead weights are attached to the ends of a metal bar. The bar hangs horizontally by a metal wire attached to its midpoint. Cavendish then brought other weights close to one of the lead weights and measured how much the gravitational attraction between the weights twisted the wire. From that measurement, he calculated the strength of gravity.

Cavendish’s accuracy was five parts in 1,000. Over 200 years later, our accuracy stands at roughly one part in 10,000. Given that modern measurements use lasers and electronic devices and Cavendish used a mirror and a candle, it hardly counts as a great improvement.

What’s worse is that our measurements of Big G are getting less accurate. The latest measurement, reported at the end of last year, reduced the overall value by 66 parts per million but the uncertainty
of the value increased from 100 parts per million to 120 parts per million.

The measurement was taken by Terry Quinn, emeritus director of the International Bureau of Weights and Measures in Paris. At its meeting in February, he argued that it was time researchers admitted that everyone must be making some basic errors in their method and that they should give up on making any more unilateral measurements.

The experts now agree that future experiments seeking the value of Big G will be done in big collaborations, with the proposals for equipment and methodology being scrutinised by everyone in advance to minimise the chance of further embarrassment.

It will, they say, mimic the way that researchers worked together to find the Higgs boson. That gave us the secret of mass: the hope is that if the physicists all pull together, they can finally work out exactly what size of force brings that mass down to earth.

Michael Brooks holds a PhD in quantum physics. He writes a weekly science column for the New Statesman, and his most recent book is At the Edge of Uncertainty: 11 Discoveries Taking Science by Surprise.

This article first appeared in the 05 March 2014 issue of the New Statesman, Putin's power game

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The science and technology committee debacle shows how we're failing women in tech

It would be funny if it wasn’t so depressing.

Five days after Theresa May announced, in her first Prime Minister’s Questions after the summer recess, that she was "particularly keen to address the stereotype about women in engineering", an all-male parliamentary science and technology committee was announced. You would laugh if it wasn’t all so depressing.

It was only later, after a fierce backlash against the selection, that Conservative MP Vicky Ford was also appointed to the committee. I don’t need to say that having only one female voice represents more than an oversight: it’s simply unacceptable. And as if to rub salt into the wound, at the time of writing, Ford has still not been added to the committee list on parliament's website.

To the credit of Norman Lamb, the Liberal Democrat MP who was elected chair of the committee in July, he said that he didn't "see how we can proceed without women". "It sends out a dreadful message at a time when we need to convince far more girls to pursue Stem [Science, Technology, Engineering and Mathematics] subjects," he added. But as many people have pointed out already, it’s the parties who nominate members, and that’s partly why this scenario is worrying. The nominations are a representation of those who represent us.

Government policy has so far completely failed to tap into the huge pool of talented women we have in this country – and there are still not enough women in parliament overall.

Women cannot be considered an afterthought, and in the case of the science and technology committee they have quite clearly been treated as such. While Ford will be a loud and clear voice on the committee, one person alone can’t address the major failings of government policy in improving conditions for women in science and technology.

Study after study has shown why it is essential for the UK economy that women participate in the labour force. And in Stem, where there is undeniably a strong anti-female bias and yet a high demand for people with specialist skills, it is even more pressing.

According to data from the Women’s Engineering Society, 16 per cent of UK Stem undergraduates are female. That statistic illustrates two things. First, that there is clearly a huge problem that begins early in the lives of British women, and that this leads to woefully low female representation on Stem university courses. Secondly, unless our society dramatically changes the way it thinks about women and Stem, and thereby encourages girls to pursue these subjects and careers, we have no hope of addressing the massive shortage in graduates with technical skills.

It’s quite ironic that the Commons science and technology committee recently published a report stating that the digital skills gap was costing the UK economy £63bn a year in lost GDP.

Read more: Why does the science and technology committee have no women – and a climate sceptic?

Female representation in Stem industries wasn’t addressed at all in the government’s Brexit position paper on science, nor was it dealt with in any real depth in the digital strategy paper released in April. In fact, in the 16-page Brexit position paper, the words "women", "female" and "diversity" did not appear once. And now, with the appointment of the nearly all-male committee, it isn't hard to see why.

Many social issues still affect women, not only in Stem industries but in the workplace more broadly. From the difficulties facing mothers returning to work after having children, to the systemic pay inequality that women face across most sectors, it is clear that there is still a vast amount of work to be done by this government.

The committee does not represent the scientific community in the UK, and is fundamentally lacking in the diversity of thought and experience necessary to effectively scrutinise government policy. It leads you to wonder which century we’re living in. Quite simply, this represents a total failure of democracy.

Pip Wilson is a tech entrepreneur, angel investor and CEO of amicable