Mobile phones would stop working — even for emergency calls. As for the emergency services themselves, not only will they have trouble finding where they need to go but communication will be snarled up as the GPS timing system is used to allow more than one conversation on their radio frequency. If power station clocks got out of sync, it could blow up their transformers, crippling electricity supplies that could be out for years before they are repaired. If that happened, said an alarming U.S. National Academy of Sciences study, drinking water would dry up as pumps failed and perishable foods and medicines would be lost because of a lack of refrigeration. ‘I’ve seen U.S. Air Force academic studies saying it wouldn’t be too long before you would have civil unrest as the populace began to lose faith in government,’ says Mr Goward of the consequences of a GPS meltdown. One would hope the military — which uses its own GPS frequency — would be on hand. A UK expert said the effects of a GPS breakdown on defence are so sensitive he couldn’t talk about them. Mr Goward is not convinced by U.S. military claims that they could still operate without GPS. Leaving aside the immediate effect on navigation and the accuracy of precision weapons, he predicts that after a few days, armed forces would be severely hit by logistical problems as everything from their phone calls to their fuel supplies petered out. ‘Then what’s the military going to do? It’s down to however many bullets they have in their pockets and how far they can fire them,’ he says. Paradoxically, scientists regret that the January 26 incident wasn’t more severe — it might have roused governments out of complacency. The U.S. government has been dithering over introducing a non-satellite back-up system, called eLoran, since 2008. But as the Royal Academy of Engineering warned five years ago, GPS is so useful and cheap to build into equipment ‘we have become almost blindly reliant on the data they give us’. As so often with new technology that offers us so much convenience, we let it take over our lives at our peril.

you most probably didn’t notice, but the world almost ground to a halt one morning 11 months ago.

It was January 26, and the problem was first picked up in the early hours by members of the U.S. Air Force Space Command at a base in Colorado.

Something had gone wrong during the decommissioning of SVN23, one of the global positioning satellites (GPS) orbiting the Earth — something that appeared infinitesimally small but was actually hugely significant.Due to what appears to have been human error by a U.S. Air Force serviceman as they replaced the oldest satellite with a new one, the latter was uploaded with the wrong time. 

It was out by just 13.7 micro-seconds, or 3.7 millionths of a second. 

That is not so much the blink of an eye but a tiny fraction of the blink of an eye.

But, as this ‘anomaly’ spread to 15 of the 31 satellites in the GPS network, it was long enough to throw electronic networks and communications systems back on Earth into disarray for the next 12 hours.

The balloon went up in companies across the globe as engineers were dragged out of their beds to fix the problem before it spun out of control and international telecommunication systems went down.

Ripples were felt across the world — in North America, emergency services radio equipment stopped working, electrical power grids were disrupted and the BBC was unable to broadcast digital radio programmes in some areas for up to two days.

Yet it could have been much, much worse. 

Experts fear that what the Royal Academy of Engineering has called Britain’s ‘dangerous dependence’ on GPS will lead to a truly apocalyptic disaster when it fails completely.

With the system ubiquitous in computer networks, financial systems, transport, agriculture, broadcasting and emergency services, a satellite blackout could plunge the world into chaos, upsetting everything from the precision docking of an oil tanker to the delivery of £50 from a cash machine.

To understand how Armageddon really could be only a few microseconds away, one must first understand that GPS — which stand for Global Positioning System, and is best known as the satnav system in our cars — is about much more than telling us when we’ve missed a turning. GPS is really about time, not maps.

It was launched by the U.S. Air Force in the late Seventies to provide an accurate bomb and missile targeting system. 

The U.S. government later allowed civilians to use it for free, although it still costs the Air Force $1 billion a year to maintain.

The GPS system depends on a network of 31 satellites circling the Earth twice a day, each moving in a very precise orbit. 

Each satellite is fitted with a clutch of incredibly precise clocks which keep time with the others.

They continually broadcast their time and position to Earth where a GPS receiver can work out its position to within a few feet from the minute differences in each signal’s arrival time.

GPS receivers used to be expensive but there’s now one in every smartphone. It’s a brilliant navigating tool even if it makes us lazy — many of us will never pore over a paper map again.

But it’s also a phenomenally accurate time-keeper, which is why it is found in pretty much every electronic system imaginable, and certainly any system that relies on a precise, synchronised timing signal.

That would include the financial sector that needs to put ‘time stamps’ on every transaction from a cash withdrawal to a high-speed stock market trade.

Then there are mobile phone networks that rely on GPS to keep transmitter towers synchronised so calls can be passed between them, and electrical power grids that need to time the delivery of energy on overloaded networks precisely.

It’s easy to see how a catastrophic failure of GPS could spell disaster for us. And there are plenty of reasons it could happen.

Sabotage is a strong possibility, thanks in large part to the extreme weakness of GPS signals. 

The London Stock Exchange is affected for up to ten minutes every day by blockages to the GPS signal which can disrupt the time stamps that identify when each trade is made.

Experts believe the problem is caused by nothing more than delivery drivers passing by the building fitted with a GPS jammer to stop their boss monitoring their movements. 

Such dashboard jammers — illegal to use in the UK but, bizarrely, not to buy — cost just £50 and pose a growing security threat.

Ports have been unintentionally closed down by criminals using jammers to stop the authorities tracing GPS tags fitted to stolen goods.

It’s feared that bigger versions could be used to knock out the GPS signal to a city, or if used at sea, cause havoc in shipping lanes. 

North Korea uses large jammers on lorries to throw its weight around and block GPS signals to South Korea for days at a time.

Defence chiefs are also braced for the possibility of an attack in space on key satellite infrastructure. 

Russia has deployed ‘kamikaze’ satellites called Kosmos 2499, designed to destroy their U.S. counterparts, while China’s ‘Shiyan’ satellite has a grappling arm that can snatch hardware out of orbit. 

General John Hyten, head of U.S. Strategic Command, recently told CNN that the U.S. was ‘developing capabilities’ to defend the country from these threats.

Natural events could prove even more devastating. 

Flying space debris can take out satellites — which are getting smaller and lighter as technology improves — and solar flares (eruptions of high-energy radiation from the sun) have already disabled satellites, burning into them in the same way that bright light can damage a retina.

The biggest catastrophe would be a solar superstorm producing huge clouds of plasma (a sort of electrified gas) travelling at millions of miles per hour. The most famous hit in 1859, dubbed the ‘Carrington event’ after a British astronomer, induced electrical currents in telegraph wires that were so strong they set alight some of the telegraph offices.

A study by the Royal Academy of Engineering warned the UK must brace itself for another inevitable superstorm. Indeed, we almost got one in 2012 when a billion-ton cloud of electrified gases erupted from the Sun at 6,000,000mph. If it had occurred nine days earlier — one third of the period of time it takes the Sun to rotate fully — it would have hit the Earth, as it would have been sitting in the line of fire

And if the GPS satellites were suddenly wiped out, what would happen? The results would be ‘pretty horrific’, Dana Goward, a navigation and timing policy expert who advises the U.S. government, tells me. ‘It’s a single point of failure for the modern world.’ GPS, he says, has become this ‘invisible utility that undergirds everything’.

Professor Charles Curry, from the British timing company Chronos, says that January 26 was a ‘lucky escape’. 

He adds: ‘Some of us in the industry have been preaching Jeremiah-like for years about this. Something will go horribly wrong and if we are not ready for it, we are going to get caught out.’

Scientists believe that if the GPS system were destroyed, the major change people would notice immediately will be on navigation — every mode of transport will slow down and become much more dangerous.

On the roads, drivers won’t be able to find their way around so easily and traffic lights — also reliant on GPS — will stop synchronising with each other. 

As with ships, planes incorporate GPS into many cockpit features and instruments.

When a commercial plane recently flew through a test area where the U.S. military had jammed the GPS system, it started to roll uncontrollably and nearly crashed as its navigation system misinterpreted its location in the sky.

Although many of the systems that use GPS have back-up clocks, these vary in terms of accuracy. And so, as more time passes, these clocks will become still more out of sync with each other — and chaos will reign.

Cash machines — unable to tell if there are funds in an account because its computer system is using an infinitesimally different time — could stop giving out money.

Mobile phones would stop working — even for emergency calls. 

As for the emergency services themselves, not only will they have trouble finding where they need to go but communication will be snarled up as the GPS timing system is used to allow more than one conversation on their radio frequency.

If power station clocks got out of sync, it could blow up their transformers, crippling electricity supplies that could be out for years before they are repaired. If that happened, said an alarming U.S. National Academy of Sciences study, drinking water would dry up as pumps failed and perishable foods and medicines would be lost because of a lack of refrigeration.

‘I’ve seen U.S. Air Force academic studies saying it wouldn’t be too long before you would have civil unrest as the populace began to lose faith in government,’ says Mr Goward of the consequences of a GPS meltdown.

One would hope the military — which uses its own GPS frequency — would be on hand. 

A UK expert said the effects of a GPS breakdown on defence are so sensitive he couldn’t talk about them.

Mr Goward is not convinced by U.S. military claims that they could still operate without GPS.

Leaving aside the immediate effect on navigation and the accuracy of precision weapons, he predicts that after a few days, armed forces would be severely hit by logistical problems as everything from their phone calls to their fuel supplies petered out. 

‘Then what’s the military going to do? It’s down to however many bullets they have in their pockets and how far they can fire them,’ he says.

Paradoxically, scientists regret that the January 26 incident wasn’t more severe — it might have roused governments out of complacency.

The U.S. government has been dithering over introducing a non-satellite back-up system, called eLoran, since 2008. 

But as the Royal Academy of Engineering warned five years ago, GPS is so useful and cheap to build into equipment ‘we have become almost blindly reliant on the data they give us’.

As so often with new technology that offers us so much convenience, we let it take over our lives at our peril.