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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Which companies are making driverless cars, and what are their competing visions for the future?

An increasing number of tech giants are populating the driverless car market. Where do each of them stand on ambition, innovation, and safety?

The driverless car has metamorphosed from a superfluous autonomous machine to the vehicle of choice for tech giants hoping to boast their technical prowess and visionary thinking.

The name of the Silicon Valley game has always been innovation, and the chance to merge quadruped hardware with self-regulating software has offered companies a new way to reinvent themselves and their visions. A new means by which to edge each other out in a race to the top of a Fritz Lang-style global metropolis, whose technocratic ruler would be the company capable of aligning their driverless transportation dreams with those of the public.

Racing quite literally out of the blocks in this race to showcase its driverless vehicles has been Uber. Having already expanded its operations as a taxi service from the streets of San Francisco to more than 300 countries worldwide, Uber went and pushed out its sample line of driverless cars in Pittsburgh last week.

Uber CEO Travis Kalanick has previously stated that the need for the company to delve into driverless cars is “basically existential”, which explains why Uber seems to be so keen to come out with a working model first. It’s a vision that seeks to cut the cost of ride-hailing by slashing the cost of human drivers, and hopes to offer a safer alternative for passengers who must place an unwarranted trust in a driver they’ve never met to shuttle them safely to their destinations.

Uber’s driverless cars are designed with Volvo, and currently require technicians at hand for potential intervention, but aims to phase these out. It has had the distinct advantage of analysing data from all the road miles made by Uber drivers so far. If Uber has its way, car ownership could be a thing of the past. Speaking to Reuters, an Uber spokesperson confirmed this, saying: “Our goal is to replace private car ownership.”

There are a number of issues at hand with Uber’s approach. The fleet of cars displayed in Pittsburgh was in fact not a fleet – there was a grand total of four for viewing, making it impossible to visualise how a fully-fledged system would work.

A more pressing issue is Uber’s timeframe: in comparison to other companies in the market, Uber is aiming for mass-market spread within a few years – far too soon according to experts who think that safety measures will be compromised, and adherence to future regulations avoided, as a result. Uber currently lacks an ethics committee, creating a grey area in determining what happens if one of these cars is involved in an accident.

Perhaps demonstrating even greater ambition, given its sheer dominance over the market, is Google. Taking on the challenge of autonomy and safety on busy city streets, Google seems to be well-equipped given its unrivalled mapping data.

First revealed in 2010, Google’s self-driving car project is expected to come into service sometime in the 2020s. Accidents and traffic could be a thing of the past, they say. Chris Urmson, who headed the project until recently, believes that these cars will work based on a positive feedback system, one which allows them to improve the more they are put into practice. As one car learns, every car will learn. Shared data means the rate of improvement for Google’s driverless cars will be exponential.

Showing no sign of a slow-up in its ambitions, Apple, a company which has found a way into the psyche of its acolytes, is thought to be getting involved in the cars of the future too. Links have been made between Apple and McLaren, with a £1.2bn acquisition rumoured. It would come as no surprise if Apple did this; its greatest successes came in convincing consumers that they needed their products, and a possible iCar could do the same.

A tamer approach to driverless cars is coming from the companies who identify themselves as automotive ones as opposed to tech ones. Tesla has led the pack with its driver-assist technology. Its Model S is “designed to get better over time”, using a “unique combination of cameras, radar, ultrasonic sensors and data to automatically steer down the highway, change lanes, and adjust speed in response to traffic”.

Following the first death of a person in an autopilot mode Tesla Model S car in May this year, the media and consumers were quick to issue warnings over the safety of the Tesla autopilot mode. Though Tesla CEO Elon Musk was quick to offer his condolences to the family of Joshua Brown, the driver who crashed in the vehicle in Florida, he was firm in his insistence that Tesla was not to blame. Musk explained that this was the first documented death of a person in a Tesla on autopilot mode after an accumulative total of 130 million miles driven by its customers, whereas “among all vehicles in the US, there is a fatality every 94 million miles”.

When put into perspective, it’s clear to see how a paranoid hysteria surrounds the rolling out of driverless vehicles. Safety has always been one of the key proponents for their use; by removing the risk of human error, we are able to create a safer road environment, as highlighted by Musk.

Earlier this year, Ford launched Ford Smart Mobility – its start-up-styled initiative designed to encourage ride sharing. By creating a small subset team to work on the technology, Ford is safeguarding itself from unforeseeable failures with driverless cars by maintaining its production of normal ones. Its cars have had elements of automation introduced incrementally, such as implanted sensors that enable these cars to park themselves. Ford hopes to have some sort of ride-sharing service in action by 2021.

BMW, Volvo and Audi are taking the cautious road too. BMW is making use of GPS to chart safe routes for its cars. In comparison to Google’s mapping, BMW’s system seems much more primitive, suggesting that the pace of development is dictated by accessibility to technology beyond vehicles. Volvo focuses on safety too and hopes that Volvo cars will be involved in no accidents by 2020 due to automation.

As we enter a market in which the top tech companies will be meeting at crossroads in their driverless cars, competing visions and levels of ambition will create a new relationship of trust between consumers and driverless car producers. There is no doubt that driverless cars will be here to stay, our roads one day teeming with passengers who get to relax on the roads. Taking your hands off the wheel will eventually become the norm, but don’t expect to be free-wheeling worldwide for a while yet.