On 6th August 1945, the citizens of Hiroshima, Japan were waking up and preparing for their daily routines. About six miles above them, the crew of the Enola Gay B-29 Superfortress prepared to drop the first atomic bomb to be used in active warfare. The bomb – 'Little Boy' – fell at 8.16am, the time shown on the watches recovered from the area obliterated by the blast, their former wearers vaporised, the time of their extinguishing forever frozen. Hiroshima ceased to exist.

"My God, what have we done? How many did we kill?" co-pilot Captain Robert Lewis wrote. On that day, 80,000 men, women and children were killed instantly, this figure rising to over 130,000 (more than the total population of Cambridge) in the succeeding weeks and months.

One might have imagined that such an unspeakable impact would quickly lead to an agreement never again to use such force. And yet, instead, the world descended into a fierce era of nuclear proliferation and atomic sabre-rattling, humanity coming closer to wiping itself out than it ever did in the Second World War. Indeed, it was the nuclear threat in part that motivated Frank Drake, in his eponymous equation, to set the time L for the probable lifetime of our civilisation at a disappointing 10,000 years.

Seven decades after the Hiroshima and Nagasaki strikes, nuclear weapons are still being debated – a particularly radioactive political football. Everywhere we look, nuclear weapons are still relevant. They were discussed at the first US presidential debate, they are a constant concern with North Korea, and an important ‘nuclear bluff’ has been called almost as I write, wherein Pakistan had pledged to defend terrorist cells (which India recently attacked) on the disputed Indian border with nuclear force if necessary.

It is easy to forget the magnitude of what is being discussed by these politicians. The recipe for this particular blend of humanity’s self-eradication is decisively short: detonate any one of the 15,000 warheads on Earth today in a populated area, sprinkle in a few retaliatory strikes and, hey presto, we have ourselves one fresh nuclear holocaust (nice and toasty).

It is often said that we live in a crazy world, and indeed we do: the threat is MAD – mutually assured destruction. If one side launches nukes, the other does too and everyone dies. Just nine countries have a supposed nuclear capability today: the UK, France, the USA, Russia, China, India, Pakistan and North Korea. Not one of these nations is willing to unilaterally disarm, and there are no major anti-nuclear crisis talks being called. No one seems concerned. And yet the human race is still one button-press away from potential extinction.

The threat of nuclear war is today almost something we think of as being completely in the past. There is a vision that things have de-escalated from something like the Cuban Missile Crisis to the situation today, where there is no risk of nuclear weapons being fired. Or at least, no one thinks about what would happen if they were anymore.

But a Chatham House report from two years ago lists 13 instances since 1962 when nuclear weapons were nearly used, purposefully or accidentally. The report notes that "individual decision-making, often in disobedience of protocol and political guidance, has on several occasions saved the day". All too often it has fallen to the action of one cool-headed individual to prevent an incident. Add to that the risk of extremist groups (who are not deterred by the threat of a nuclear strike) getting their hands on a weapon of this calibre and you have a real and present danger.

Astrophysicist Carl Sagan once said: “The nuclear arms race is like two sworn enemies standing waist deep in gasoline, one with three matches, the other with five.” Today there are more than two people in the gasoline, each one is holding more matches and they are either staring at one another suspiciously or don’t know what to think of each other.

The nukes haven’t gone anywhere: we have just got tired of being worried about them. The legacy left by the use of nuclear weapons has led to a general consensus that their use is unthinkable today, and yet no one is willing to give up their ability to do the unthinkable.

In the same way so many of us in the younger generation are concerned about climate change, perhaps we should be concerned about the small cohort of people with access to doomsday buttons, be they for us or against us. The finer points of how to get rid of nuclear weapons is one for the politicians, but whether disarmament is unilateral, multilateral or something else, we should at least be disarming.

Perhaps humanity has indeed survived its closest brush with nuclear extinction, but perhaps we are merely living in the eye of the storm. Our post-nuclear civilisation is still at risk of becoming simply ‘post-civilisation’, and that is something worth sorting out.