It was the year of the Watergate hearings, Ireland's entry into the EEC and Carly Simon's 'You're So Vain'. But perhaps the most significant event of 1973 occurred on April 3 on an anonymous street corner in New York City.
Amid the bustle and grime of 1970s Manhattan, a 44-year-old held a large brick-shaped device to his ear and started talking. The man was Dr Martin Cooper and, using the prototype Motorola DynaTAC, he was making the world's first mobile-phone call. At no point in the conversation is he believed to have said: "Speak up, I'm on the bus."
"As I walked down the street while talking on the phone, sophisticated New Yorkers gaped at the sight of someone actually moving around while making a phone call," he recalled.
In his hour of triumph, Cooper couldn't resist tweaking a rival's nose.
"I was calling Joe Engel, who was my antagonist, my counterpart at AT&T, which at the time was the biggest company in the world. We [Motorola] were a little company in Chicago. They considered us to be a flea on an elephant. I said 'Joel, this is Marty. I'm calling you from a cell phone, a real, handheld, portable cell phone'. There was silence at the other end. I suspect he was grinding his teeth."
Regulatory and technological headaches meant another decade would elapse before the Motorola 'brick' entered widespread use. It was a formidable device, nine inches tall with 30 circuit boards and a 10-hour battery life.
"The first cell phone model weighed over one kilo and you could only talk for 20 minutes before the battery ran out," said Cooper. "Which is just as well because you would not be able to hold it up for much longer."
From such unpromising beginnings, the mobile has become the defining technology of the modern age. There are now estimated to be a greater number of cellular devices – some seven billion – in existence than people on the planet. It is the invention that has penetrated every corner of the world, every crevice of humanity. On its 40th birthday then, here are some fascinating mobile phone facts of which you might not be aware.
1 Your mobile may be bad for your nerves. Being permanently plugged into the internet via our phones increases anxiety and causes difficulty for people trying to interact with the world around them, experts fear.
"When you switch tasks, it requires attention. Paying attention to what you're doing and who you are with and turning your phone off and enjoying being with your friends is much better for you than constantly checking your phone and checking emails," Professor Paul Dolan of the London School of Economic told a conference recently.
2 The first photograph snapped using a mobile phone was taken on June 11, 1997. Phillipe Kahn took a picture from the maternity ward where his daughter Sophie was born.
"I wanted to create a 21st-Century version of a Polaroid picture," said Kahn, credited with bringing the camera-phone into widespread use.
3Early mobile phones retailed for upwards of $3,000. The price of handsets has plummeted ever since. Still, there will always be individuals who enjoy splashing out. It was with these in mind that the €8m 'Diamond Rose' iPhone 4 (left) was created by UK designer Stuart Hughes. Setting the bling factor to kill, the Diamond Rose is inlaid with 500 diamonds, a 53-diamond 'rose gold' Apple logo and, for the home button, a 7.4-carat pink diamond. Lovely, but probably not what you want to be playing Angry Birds on while taking the Luas.
4 Apple's iPhone is generally assumed to be the bestselling phone ever. In fact, it is beaten to number two by Nokia's 'candybar' shaped N1100, unveiled in 2003. Some 250 million have been purchased and in 2009 demand for the ageing handset jumped amid (false) rumours that it could intercept third-party calls.
5 The world's toughest phone, as certified by the Guinness Book of Records, is the Sonim XP3300 Force, which remained operational after a fall of 84ft on to concrete. It can also be submerged up to two metres in water.
6 The text message was invented by German Friedhelm Hillebrand in 1985. Initially, he confined message length to 160 characters, deeming roughly two lines of text sufficient for everyday use. Generally, this limit no longer applies.
7 Ireland is a nation of incessant texters. Still, we are thoroughly eclipsed by the Philippines. Widely acknowledged as the "text capital of the world", some 1.4 billion texts are sent there each day.
8 Smartphones may have killed off mp3 players such as the iPod. But it was as recently as 2001 that the first phone with music-playing capacity debuted. Siemens' SL45 delivered a none too shabby five hours of playback with each charge. If it didn't quite kickstart a revolution it may be because of its puny 32-megabyte storage, enough for an entire 30 minutes of music.
9 The growing popularity of mobile phones created early headaches for emergency services. At one stage some 70pc of 911 calls to police or firefighters in parts of the United States were attributed to 'phantom calls', ie calls made accidentally from the owner's pocket. One difficulty was that many American handsets auto-dialled 911 if two numbers were held down at once. The design flaw has since been addressed.
10Apple boss Steve Jobs usually receives the credit, but the first true smartphone was launched by a rival in 1993. 'Simon' was part-designed by IBM and featured a primitive touch-screen. You could send emails or make notes using an address book and calendar.
Only 2,000 were built and, retailing at €900, did not exactly fly off shelves. They've since come down in price somewhat: you can buy one on eBay for around €700.