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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Doing a Radiohead: how to disappear online

The band has performed an online Houdini in advance of its ninth album – but it’s harder than it looks. 

At the beginning of May, the band Radiohead’s web presence – well, its Twitter, Facebook, and website, at least – went offline.

Lead singer Thom Yorke has repeatedly criticised streaming, and the future of online music in general, and it's clear that his opinion fed into this month's decision to reject social media in favour of sending individual cards to the band's fans in the post. 

However, it’s also a clever publicity stunt in the run up to the rumoured release of the band's ninth album, since it plays into a growing paranoia around the lives we live online, and quite how permanent they are. In reality, though, Radiohead has done a pretty terrible job of disappearing from the internet. Its Facebook and Twitter accounts still exist, and widely available caching services actually mean you can still see Radiohead.com if you so wish. 

These are the steps you’d need to take to really disappear from the internet (and never be found).

Delete your acccounts

Radiohead may have deleted its posts on Facebook and Twitter, but its accounts – and, therefore user data – still exist on the sites. If this was a serious move away from an online presence, as opposed to a stunt, you’d want to delete your account entirely.

The site justdelete.me rates sites according to how easy they make it to delete your data. If you only hold accounts with “easy” rated sites, like Airbnb, Goodreads and Google, you’ll be able to delete your account through what justdelete.me calls a “simple process”. JustDelete.me also links you directly to the (sometimes difficult-to-find) account deletion pages.

Failing that, delete what you can

If, however, you’re a member of sites that don’t allow you to delete your account like Blogger, Couchsurfing or Wordpress, you may be stuck with your account for good. However, you should at least be able to delete posts and any biographical information on your profile.

If this bothers you, but you want to create an account with these sites, Justdelete.me also offers a “fake identity generator” which spits out fake names and other details to use in the signup process.

Go to Google

Search results are the hardest thing to erase, especially if they’re on sites which published your details without your permission. However, thanks to the European Commission “Right to be forgotten” ruling in 2014, you can now ask that certain search results be deleted using this online form.  

Ditch your smartphone

Smartphones tend to track your location and communicate with app and web servers constantly. For true privacy, you’d want to either disconnect your phone from all accounts (including iCloud or Google) or else get a basic phone which does not connect to the internet.

Give out your passwords

The artist Mark Farid decided in October 2015 to live without a digital footprint until April 2016, but was aghast when he realised quite how often our data is collected by our devices. As a result, he decided to live without bank accounts, use a phone without internet connectivity, and use an unregistered Oyster.

When I saw him speak at an event just before his off-grid experiment was due to begin, he announced that he would also be handing out the passwords to all his online accounts to the public. The kind of “bad data” which randomly hacked accounts would show would actually make him less traceable than a radio silence – a bit like how words written over other words mask them more than simply erasing them or scribbling on them would.

Accept that it probably won’t work

Even if you managed all this, the likelihood is that some of your daily activities would still leave a trace online. Most jobs require internet activity, if not an internet presence. Bank accounts are, let's face it, fairly necessary. And even Radiohead will, I’m willing to bet, reappear on the internet soon after their album arrives.

Barbara Speed is a technology and digital culture writer at the New Statesman and a staff writer at CityMetric.