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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Disney didn’t buy Twitter — partly because it can't master the Bare Necessities

Walt Disney Co. has decided against bidding for the social network.

Hakuna Matata. What a wonderful phrase. It means no worries for the rest of your – @simba DIE U STUPID LION UR SONG IS SHIT.

That was a short representation of one the alleged reasons why Walt Disney Co. opted out of bidding for Twitter last night. Despite hiring two investment banks to help them weigh up a deal, Disney have dropped out of the running partly because – according to Bloomberg – of the social networks’s reputation for bullying and harassment, as well as its falling profits. Individuals close to Disney management allegedly told the business news website that Twitter did not fit well for the company, which, after all, is more famous for feel-good anthropomorphic animals than angry, anonymous eggs. 

Those who mistakenly believe Twitter is a happy place where ev’rybody wants to be a cat might need an explanation. Despite the apparent abundance of cat gifs, Twitter can be a violent and angry social network – a report last year stated that 88 per cent of the abusive mentions on social media happen on the site. Twitter has long struggled to stop abuse overwhelming discussion on the social network. This has fed the perception among some of its 300 million users that tackling abuse is a low priority, with efforts at reducing trolling overshadowed by the release of new features such as increased message length and curated news feeds known as Moments. Because of this, the site has become seen as – in one former employee’s words – “a honeypot for assholes.” Oh, bother.


Earlier this year, Ghostbusters star Leslie Jones was bombarded with racist tweets upon the film's release, forcing her to leave the site for a few weeks. "Twitter I understand you got free speech I get it. But there has to be some guidelines," she wrote. The company did take action in the wake of the Jones case, permanently banning the prominent right-wing journalist and notorious troll, Milo Yiannopoulos, from the site for his role in fanning the flames of the abuse. But, while Google has set up a new company, Jigsaw, to make the internet a safer place, Instagram regularly bans offensive hashtags and Facebook has devoted time to constantly updating its anti-harassment tools (most recently making it easier to report revenge porn), Twitter’s trolling problem continues.

Even Twitter's former top employees have criticised the company's efforts. In a leaked memo from 2015, then-CEO Dick Costolo said: "We suck at dealing with abuse and trolls on the platform and we've sucked at it for years." Earlier this year, the current CEO Jack Dorsey admitted Twitter "must do better" at dealing with abuse. Salesforce, another potential buyer, have also allegedly been put off by the site's reputation. "The haters reduce the value of the company... I know that Salesforce was very concerned about this notion," reported CNBC's Jim Cramer

Neither company has declared publicly that Twitter's abuse problem dettered them from the sale, but could the loss of this latest suitor push them to take the problem more seriously? Having some sort of pre-emptive anti-harassment tool has become the bare necessities of running a successful social network, but Twitter still waits for users to report abuse and then, frequently, tells them that the abusive content actually didn’t violate their rules. 

It is not too late for Twitter to turn itself around, as many of its users are still loyal despite the abuse. With one successful attempt to tackle harassment, a resurgence for the site could be just around the riverbend. In the words of the wise Rafiki: "Oh yes, the past can hurt. But from the way I see it, you can either run from it, or... learn from it."