There are 32 “space vehicles” orbiting our planet twice a day, in six orbital planes, at an altitude of 12,600 miles. The GPS receiver on my bike, a Garmin Edge 800, sights between four and six of them and uses the angles of inclination to plot the co-ordinates of my position to within 20 metres.

In 1957 the Soviet Union launched its Sputnik satellite, causing fear and uncertainty in the United States. It led to the formation of NASA, the start of the “Space Race” and the passing of the National Defense Act, allocating millions of dollars to train mathematicians and linguists.

In a cafeteria at Johns Hopkins University, the day after the launch, two young physicists in their late twenties, Bill Guier and George Weiffenbach, realised to their surprise that no-one there was monitoring the Sputnik transmissions. So they decided to see if they could hang a wire from the aerial of a nearby radio station and listen in to Sputnik.

Sputnik was transmitting on a frequency that could be read as an auditory signal. The two scientists realised they could determine its location, speed and direction from the slope of the so-called Doppler effect, the slight change in a frequency that depends on whether an object is approaching or receding.

Their team leader was impressed. He gave them access to the huge Univac 1200F computer, with its 5200 vacuum tubes, to see if they could build a reliable model to achieve this.

A little while later, Frank McClure, their deputy director, called them in, shut the door and asked them if they could invert the solution, i.e. determine the station position from the orbit data. He just said, “Do an error analysis and let me know the answer ASAP”.

McClure took their results and, with his friend Dick Kershner, wrote up, over a weekend, the design essentials of a Transit Navigation System: multiple orbiting satellites radiating stable frequencies to earth-based receivers enabling the accurate plotting of location coordinates.

McClure and Kershner knew the importance of this. McClure was spending time at the Navy’s Special Projects office which was developing the Polaris nuclear submarine. At the height of the Cold War America’s “nuclear triad” consisted of submarine-launched ballistic missiles (SLBMs), strategic bombers and intercontinental ballistic missiles (ICBMs).

Accurate determination of the SLBM launch position was a “force multiplier”. Aiming the weapon required a precise knowledge of your own position. Mobile launchers were a key part of the deterrence strategy. Only a mobile launcher could avoid a “first strike” and be certain of delivering a devastating retaliation.

The Global Positioning System or GPS was kept secret for many years.

Then, in 1985, Korean airlines flight KAL 007 was shot down having strayed into Soviet airspace. All 269 passengers and crew were killed.

The following year Ronald Reagan ordered that the GPS system should be made public for civilian navigation. By 1999, when the last satellite was launched, the cost of the programme was estimated to have reached $5 billion.

In 1984, Gary Burrell, then working for avionics manufacturer King Radio, recruited Min Khao from defence contractor Magnavox. In 1989 they set up a firm together in Lenaxa, Texas, to build navigation devices.

The US army was their first customer. Their first civilian product was a marine guidance panel costing $2500. It was an instant success. To meet the demand Min Khao set up a manufacturing facility in Taiwan.

Another early success was a handheld device used by soldiers serving in Kuwait and Saudi Arabia in the 1991 Gulf War. I have seen pictures of it. It’s not so different from the device attached to the handlebars of my mountain bike today.

The mountain bike rattles and judders down stony gullies. Then I pedal up to a sandy hilltop. From there I can look down on a wide semi-circular bay.

At the head of the bay is a huge structure of concrete domes and rectangles. It is a nuclear power station.

The reading lamp on my desk as I finish this post is powered by energy generated when a uranium atom is bombarded by neutrons that smash its nucleus in two.