The Knowledge

Buildings crumble and nature reclaims our urban spaces, including our stores of knowledge like this New Jersey library.

Over a number of years, accumulating leaf litter and other vegetative matter from this pioneering burst of growth decays to an organic humus and mixes with the windblown dust and grit of deteriorating concrete and bricks to create a genuine urban soil. Papers and other detritus billowing out of broken office windows will collect in the streets below and add to this composting layer. A thickening carpet of dirt will smother the roads, pavements, parking lots and open spaces of towns and cities, allowing a succession of larger trees to take root. Away from the tarmacked streets and paved squares, the cities’ grassy parks and the surrounding countryside will rapidly return to woodland. In just a decade or two, elder thickets and birch trees will have become firmly established, maturing to dense woods of spruce, larch and chestnut by the end of the first century after the apocalypse.

And while nature is busy reclaiming the environment, our buildings will crumble and decay among the growing forests. As vegetation returns and fills the streets with wood and drifts of windblown leaves, mingling with the rubbish cascading from broken windows, piles of perfect kindling will collect in the streets and the chance of raging urban forest fires increases. Tinder accumulated against the side of a building and ignited by a summer lightning storm, or perhaps sunlight focused through broken glass, is all that’s needed to unleash devastating wildfires that spread along the streets and burn up the inside of high-rises.

A modern city wouldn’t be razed to the ground like London in 1666 or Chicago in 1871, the fire ripping rapidly from one wooden building to the next and leaping across the narrow streets, but blazes spreading unopposed by firefighters would still be devastating. Gas lingering in underground pipes and throughout buildings would explode, with fuel left in tanks of vehicles abandoned in the streets adding to the intensity of the inferno. Dotted throughout populated areas are bombs waiting to go off when a blaze sweeps through: petrol stations, chemical depots, and the vats of highly volatile and flammable solvents in dry-cleaners’. Perhaps one of the most poignant sights for the post-apocalyptic survivors would be the burning of the old cities, thick columns of choking black smoke towering above the landscape and turning the sky blood red at night. After a passing blaze, the brick, concrete and steel matrix of contemporary buildings would be all that is left – charred skeletons once their combustible internal viscera have been gutted.

Fire will wreak devastation across great areas of the deserted cities, but it is water that will eventually bring certain destruction for all our carefully constructed buildings. The first winter after the apocalypse will see a spate of burst frozen water pipes, which will disgorge inside buildings during the following thaw. Rain will blow in through missing or broken windows, trickle down among dislodged roofing tiles and overflow from blocked gutters and drains. Peeled paint from window and door frames will allow moisture to soak in, rotting wood and corroding metal until the whole frame falls out of the wall. The wooden structures – floorboards, joists and roof supports – will also soak up moisture and rot, while the bolts, screws and nails holding the components together rust.

Concrete, bricks and the mortar smeared between them are subject to temperature swings, soaked with water trickling down from blocked gutters and pulverised by the relentless pulsing of freeze–thaw at high latitudes. In warmer climates, insects such as termites and woodworm will join forces with fungi to eat away at the wooden components of buildings. Before too long, wooden beams will decay and yield, causing floors to fall through and roofs to collapse, and eventually the walls themselves bow outwards then topple. The majority of our houses or apartment blocks will last, at most, a hundred years.

Our metal bridges will corrode and weaken as the paint peels off, allowing water to seep in. The death knell for many bridges, though, is likely to be windblown detritus collecting in the expansion gaps, breathing spaces designed to allow the materials to swell in the summer heat. Once clogged, the bridge will strain against itself, shearing off corroding bolts until the whole structure gives way. Within a century or two, many bridges will have collapsed into the water below, the lines of rubble and debris at the feet of the still-standing pillars forming a series of weirs in the river.

The steel-reinforced concrete of many modern buildings is a marvellous construction material, but although more resistant than wood, it is by no means impervious to decay. The ultimate cause of its deterioration is ironically the source of its great mechanical strength. The steel reinforcing bars (rebars) are cocooned from the elements by the concrete surrounding them, but as mildly acidic rainwater soaks through, and humic acids released by rotting vegetation seep into the concrete foundations, the embedded steel begins to rust inside the structures. The final blow for this modern construction technique is the fact that steel expands as it rusts, rupturing the concrete from the inside, leaving even more surface exposed to moisture and so accelerating the endgame. These rebars are the weak point of modern construction – and unreinforced concrete will prove more durable in the long run: the dome of the Pantheon in Rome is still going strong after two thousand years.

The greatest threat to high-rises, though, is waterlogged foundations caused by unmaintained drainage, blocked sewers or recurrent floods, particularly among cities built along the banks of a river. Their supports will corrode and degrade, or subside into the ground to create a listing skyscraper far more ominous than the Leaning Tower of Pisa, before inevitably collapsing. The raining debris will further damage surrounding edifices, or the buildings may even topple over into neighbouring monoliths like giant dominoes, until only a few remain spiking above a skyline of trees. Few of our great high-rise buildings can be expected to be still standing after a few centuries.

Within just a generation or two the urban geography will have become unrecognisable. Opportunistic seedlings have become saplings have become full-blown trees. City streets and boulevards have been replaced by dense corridors of forest crammed into the artificial canyons between high-rise buildings, themselves now grossly dilapidated and trailing vegetation from gaping windows like vertical ecosystems. Nature has reclaimed the urban jungle. Over time, the jagged piles of rubble from collapsed buildings will themselves become softened by the accumulation of decomposing plant matter forming soil – hillocks of dirt sprouting trees, until even the tumbled remains of once-soaring skyscrapers are buried and hidden by verdant growth.

Away from the cities, fleets of ghost ships drift across the oceans, occasionally carried by the vagaries of wind and currents to ground themselves on a coastline, slicing open their bellies to bleed noxious slicks of fuel oil or releasing their load of containers on to the ocean currents like dandelion seeds in the wind. But perhaps the most spectacular shipwreck, if anyone happens to be in the right place at the right time to watch it, will be the return of one of humanity’s most ambitious constructions.

The International Space Station is a giant 100-metre-wide edifice built over fourteen years in low Earth orbit: an impressive assemblage of pressurised modules, spindly struts, and dragonfly wings of solar panels. Although it soars 400 kilometres above our heads, the space station is not quite beyond the wispy upper reaches of the atmosphere, which exerts an imperceptibly slight but unrelenting drag on the sprawling structure. This saps the space station’s orbital energy so that it spirals steadily towards the ground, and it needs to be repeatedly boosted back up with rocket thrusters. With the demise of the astronauts, or lack of fuel, the space station will relentlessly drop about 2 kilometres every month. Before long, it would be hauled down into a fiery plunge through the air, ending in a streak of light and fireball like an artificial shooting star.

THE POST-APOCALYPTIC CLIMATE

The gradual decay of our cities and towns is not the only transforming process that survivors will witness.

Since the Industrial Revolution and the exploitation of first coal and then natural gas and oil humanity has been fervently burrowing underground to dig up the buried chemical energy accumulated from times past. These fossil fuels, readily combustible dollops of carbon, are the decayed remains of ancient forests and marine organisms: chemical energy derived from the trapping of sunlight that shone on the Earth aeons ago. This carbon originally came from the atmosphere, but the problem is that we are burning the stores so quickly that a few hundred million years’ worth of fixed carbon have been released back into the atmosphere in just over a hundred years, pumped out of our smokestacks and car exhausts. This is far, far faster than the planetary system can reabsorb the liberated carbon dioxide, and there is about 40 per cent more of the gas in the air today than at the beginning of the eighteenth century. One effect of this elevated carbon dioxide level is that more of the sun’s warmth is trapped by the Earth’s atmosphere through the greenhouse effect, leading to global warming. This in turn will cause a rise in sea levels and the disruption of weather patterns worldwide, creating more frequent, heavier monsoon floods in some areas and droughts in others, with severe repercussions for agriculture.

With the collapse of technological civilisation emissions from industry, intensive agriculture and transport would cease overnight, and pollution from the small surviving population would drop to practically zero in the immediate aftermath. But even if emissions were to stop tomorrow, the world would continue to respond for the next few centuries to the vast amount of carbon dioxide our civilisation has already belched out. We are currently in a lag phase, as the planet reacts to the sudden hard shove we have given to its equilibrium.

The post-apocalyptic world is likely to experience a rise in sea level of several metres over the following centuries from momentum already built up in the system. The effects could be much worse if the warming has knock-on consequences, such as the thawing of methane-laden permafrost or widespread melting of glaciers. Whilst carbon dioxide levels will decline after the apocalypse, they will plateau at a substantially elevated value and not return to their pre-industrial state for many tens of thousands of years. So over the timescale of our, or any following civilisation, this forced cranking-up of the planet’s thermostat is essentially permanent and our current carefree lifestyle will leave a long, dark legacy for those inhabiting the world after us. The consequences for survivors already struggling to support themselves is that as the climate and weather patterns continue to change over the generations, once-fertile cropland may be ruined by drought, low-lying regions become flooded and tropical diseases become more prevalent. Shifts in local climate have caused abrupt collapses of civilisations in our history and the ongoing global changes may well frustrate the recovery of a fragile post-apocalyptic society.

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1 However, some of the longer-term ramifications of the Black Death were beneficial to society: a cultural silver lining to the cloud that was the Great Dying. With the ensuing labour shortage, serfs who survived the mass depopulation were able to slip their bond to the Lord of the Manor, helping break the oppressive feudal system and ushering in a much more egalitarian social structure and market-orientated economy.

2

The Grace Period

‘Thus we never see the true state of our condition till it is illustrated to us by its contraries, nor know how to value what we enjoy, but by the want of it.’

Robinson Crusoe, Daniel Defoe

AFTER A PLANE crash in a remote area, your main priorities for survival would be shelter, water and food. The same requirements are paramount after the crash of civilisation around you. While it’s possible to survive for several weeks without food, and a few days without drinking water, if you’re caught outside in an inclement climate you can die of exposure within a matter of hours. As the SAS survival expert John ‘Lofty’ Wiseman told me, ‘If you’re still on your feet after the big bang you are a survivor. But how long you continue to survive is down to your knowledge and what you do.’ For our purposes we’ll assume that, like more than 99 per cent of people, including myself, you’re not a prepper and have not stockpiled food and water, fortified your home or made any other prior arrangements for the end of the world.

So during the crucial buffer period before you’re forced to start producing things anew, what remnants could you scavenge to ensure your survival? What would you want to look out for when beachcombing the detritus left by the receding technological tide?

SHELTER

In the situation we’ve imagined (loss of people, but no massive destruction of the stuff that surrounds us), you’re not likely to lack shelter: there will be no shortage of abandoned buildings in the immediate aftermath. It would be well worth it, though, to embark immediately on a scavenging foray to a camping store to get yourself some new attire. The dress code for the end of the world is pragmatic: loose hard-wearing trousers, layers of warm tops, and a decent waterproof jacket will keep you comfortable while spending a lot more time in the open or in unheated buildings. Sturdy hiking boots may not look very glamorous, but in a post-apocalyptic world you really don’t want to lose your footing and break an ankle. Over the first few years, the best place to forage for clothing that has not yet been destroyed by insects or the penetrating damp would be large shopping centres. It’s a long way into the deep interior of a mall, and goods there are safe from the elements.

Warm clothes aside, it’s fire that will ensure your survival. Fire has had a fundamental role in human history, protecting against the cold, providing light, cooking food to render it more digestible and pathogen-free, and smelting metals. Immediately after the collapse you won’t need wilderness survival skills like rubbing sticks together to ignite tinder. There will be plentiful boxes of matches in corner shops and homes, and disposable gas lighters will continue to work for years.

If you can’t find matches or lighters, there are less conventional methods for starting a fire using scavenged materials. If it’s a bright day, sunlight can be concentrated into a hot focus using a magnifying glass, a pair of glasses,¹ or even the curved base of a drinks can that has been polished with a square of chocolate or dab of toothpaste. Sparks can be generated by touching together jump leads attached to an abandoned car battery, and wire wool scavenged from a kitchen cupboard will ignite spontaneously when it is rubbed against the terminals of a 9-volt battery liberated from a smoke detector. There will be an abundance of excellent tinder lying around deserted human habitations, such as cotton, wool, cloth or paper, especially if you douse it in a makeshift fire accelerant like Vaseline, hairspray, paint thinner or simply a drop of petrol. And you won’t struggle to find fuel to burn, even in an urban environment. Populated areas are packed with combustible materials, from furniture and wooden fittings to garden shrubs, that can be thrown on a fire for heat and cooking.

The issue is not starting a fire or keeping it going, but where to make it. The vast majority of recently built houses and apartments have no working fireplace. If need be, you can safely contain a fire within a metal bin or bring a barbecue indoors, or if the apartment has a concrete floor you could rip away a patch of carpet and light a fire directly on the concrete. You’ll need to allow the smoke and fumes to escape through a slightly opened window (especially if you’re forced to resort to combusting synthetic fabrics or furniture foam). But your best bet would be to try to find an older cottage or farmhouse which is appropriately equipped to be heated by fires rather than radiators – this is one of the major incentives to abandon the cities as quickly as possible, as we’ll see in a while.

WATER

After shelter and protection from the elements, the second priority on your checklist is to secure clean drinking water. Before the municipal water supply runs dry you should fill your bath and sinks to the brim with water, as well as any clean buckets or even strong polythene rubbish bags. These emergency water stores should be covered to keep them free from detritus and to block the light that allows algal growth. Bottled water can be scavenged from supermarkets and water coolers in office buildings. Other reservoirs of water you’ll be able to drain include hotel and gym swimming pools, as well as the hot-water tanks in any large building. In time, you’ll come to rely on water sources you’d normally have turned your nose up at. Every survivor will need at least 3 litres of clean water every day, and more in hot climates or with exertion. Keep in mind that this is for rehydration alone and does not include water necessary for cooking and washing.

Water that doesn’t come from a sealed bottle must be purified. A sure-fire method for sterilising water to remove pathogens is to bring it to a rolling boil for a few minutes (although this offers no protection against chemical contamination). This is very time-consuming, however, and will rapidly eat through stocks of fuel. A more practical, longer-term solution for purifying larger volumes of water, once you have settled down after the event, relies on a combination of filtration and disinfection. A rudimentary but perfectly adequate system for filtering out particles in murky lake or river water uses a tall receptacle like a plastic bucket, steel drum or even a well-cleaned bin. Punch some small holes in the bottom, and cover with a layer of charcoal, either lifted from a hardware store or created yourself using the instructions here. Alternate layers of fine sand and gravel on top of the charcoal. Pour the water into your receptacle, and as it drains through, it will be effectively filtered of most particulate matter.

The first option for disinfecting this filtered water to eliminate waterborne pathogens is to use dedicated water purification treatments, such as iodine tablets or crystals available from camping shops. If you can’t find any, there are some surprising alternatives that will also work perfectly well, such as chlorine-based bleaches formulated for household cleaning. Just a few drops of a 5 per cent liquid bleach solution that has sodium hypochlorite listed as the main active ingredient will disinfect a litre of water in an hour. But carefully check the label to ensure that the product doesn’t also contain additives like perfumes or colorants that may be poisonous. A single bottle of bleach found under a kitchen sink can purify around 500 gallons of water – almost two years’ supply for one person.

Products used for chlorinating swimming pools, scavenged from the storeroom of a gym or wholesaler, can also be used at a weaker dilution to disinfect drinking water. A single teaspoon of this calcium hypochlorite powder is enough to disinfect 200 gallons of water (but again, be careful it doesn’t contain antifungal agents or clarifier additives). Later on, once all the readily available chlorinating agents are gone, you’ll need to create your own from scratch using seawater and chalk as raw materials, as we’ll see in Chapter 10.

Plastic bottles can be used not just for storing water, but for sterilising it as well. Solar water disinfection, or SODIS, employs only sunlight and transparent bottles, and is recommended by the World Health Organization for decentralised water treatment in developing nations – a perfect low-tech option for the post-apocalyptic world. Tear the labels off clear plastic bottles – but don’t use bottles bigger than 2 litres as the crucial part of the sun’s rays won’t be able to penetrate all the way through – fill with the water to be disinfected, and lay them down outside in full sunlight. The ultraviolet component of the sun’s rays is very damaging to microorganisms, and if the water warms up to above 50°C this deactivating effect is greatly enhanced. A good system is to lean a sheet of corrugated iron angled to the sun and stack the water bottles in the grooves. Painting the sheet black helps the heat sterilisation effect.

However, glass and some plastics, such as PVC, block out the UV rays. Check the bottom of the plastic bottle: most are now manufactured with a recycling symbol and you want those marked with a _{, which indicates that they are made of PET. If the water is too murky for the sunlight to penetrate, you’ll need to filter it first. In bright, direct sun, this method can disinfect water in around six hours, but if it is cloudy it’s best to leave it for a couple of days.}

FOOD

How long will you be able to continue dining out on the leftovers of our civilisation? The expiry date on modern packaging is only a guideline and often underestimates deterioration by a safe margin. So how long would different food types actually remain edible? Some products will last more or less indefinitely, including salt, soy sauce, vinegar and sugar (as long as it stays dry), and we’ll see in Chapter 4 how these substances can be used to preserve food.

Other staples of our diet won’t fare so well on the shelves of deserted supermarkets. Most of the fresh fruit and vegetables will have wilted and rotted within weeks, but tubers will persist much longer since they evolved to store energy over winter for the plant. Potatoes, cassava and yams all have a good chance of lasting over six months if they’re in a cool, dry and dark place.

Cheese and other treats on the delicatessen counter will be mouldy within weeks, and after a matter of months the butcher’s unpackaged meat joints will have decomposed to leave only the odd T-bone or rack of ribs. Eggs are surprisingly resilient and can remain edible for over a month without refrigeration.

Fresh milk will be spoiled within a week or so but UHT packs will last years, and powdered milk even longer. Since it’s the fat content of dried foodstuffs that often spoils first as it undergoes rancidification, fat-free powdered milk remains potable the longest. Lard and butter will spoil quickly within the defunct refrigerators, and cooking oils will also turn rancid over time. (Once unfit for human consumption, their lipid content can still be used to make soap or biodiesel, as we’ll see later on.)

White wheat flour will keep for only a few years, but longer than wholemeal flour, which, due to its much higher oil content, goes rancid quickly. Flour products such as dried pasta will also last a few years. The nutritional content survives far better if the grains have not been cracked or ground (which exposes the inner germ to moisture and oxygen), so unmilled wholewheat grains remain good for decades. Likewise, whole maize grains will remain nutritious for around ten years, but this persistence time drops to just two or three years for cornmeal. Dried rice keeps well for between five and ten years.

All of this assumes that the surviving food is in conditions that favour preservation: cool and dry. This isn’t an unreasonable expectation for the interior of a large supermarket in a temperate region, but if you’re living in a hot humid climate, food will begin to decay rapidly as soon as the grid goes down and air conditioners rumble into silence. After the refrigerators and freezers fail, the pungent aroma of putrefying food will attract many non-human foragers: rats and insects, as well as packs of dogs and other former pets now growing increasingly hungry. Even well-packaged food is likely to succumb to the onslaught of teeth and claws, so the food resources available to the survivors may be limited less by expiry dates than by pests – as were the granaries of the earliest civilisations.

By far the largest reserve of preserved sustenance, however, will be the rows upon rows of canned food that fill the supermarket shelves. Not only will the armoured packaging resist the post-apocalyptic plagues of vermin and insects, but the heat treatment during the canning process is exceptionally good at protecting their contents against microbial spoilage from within. Although the printed ‘best before’ date is often only two years in the future, many canned products will keep for several decades, if not more than a century after the fall of the civilisation that produced them. Rust or dents on the can itself do not necessarily mean that the contents are compromised, as long as there are no signs of leakage or bulging.

So if you were a survivor with an entire supermarket to yourself, how long could you subsist on its contents? Your best strategy would be to consume perishable goods for the first few weeks, and then turn to the dried pasta and rice, as well as the more resilient tuber vegetables, before finally resorting to the most reliable reserve of tinned produce. Assuming also that you are careful to keep a balanced diet with the necessary intake of vitamins and fibre (the health supplements aisle will help you here), your body will need 2–3,000 calories a day, depending on your size, gender and how active you are. A single average-sized supermarket should be able to sustain you for around 55 years – 63 if you eat the canned cat and dog food as well.

This calculation naturally scales up, from a single individual with a supermarket at his or her disposal to the surviving population of a cataclysm surrounded by the preserved sustenance of a whole nation, from small corner shops to enormous distribution warehouses. The UK Department for Environment, Food and Rural Affairs (DEFRA) estimated in 2010 that there was a national stock reserve of 11.8 days of ‘ambient slow-moving groceries’ (non-perishable, unfrozen produce like rice, dried pasta and cans). With an apocalyptic population crash this would equate to as much as fifty years’ supply for a surviving community of around ten thousand people. Thus a community large enough to rapidly reboot technological civilisation should have sufficient breathing space to reinstate agriculture and grow its own food.

FUEL

Another key consumable of modern life, and one that will remain crucial for transport, agriculture and running generators during the rebuilding, is the availability of fuel. There will be huge reserves of petrol and diesel fuel for the surviving population. The fuel tanks of the almost 30 million cars in the UK – as well as the motorcycles, buses and trucks – offer a scattered repository that can be tapped into. Petrol can be scavenged from abandoned cars by siphoning out of the tank, or even more simply by hammering a screwdriver into the tank to drain it into a waiting receptacle. The underground storage tanks of petrol stations also collectively hold a vast reserve. Without power, the forecourt pumps won’t work but it wouldn’t take much to jury-rig a pump with a 5-metre pipe to drain them. Each petrol station holds a subterranean lake of fuel of typically around 30,000 gallons, enough for an average family car to drive over a million miles along post-apocalyptic roads.

The wider issue is how well that fuel persists. Diesel is more stable than petrol, but even within a year reactions with oxygen would begin to form a gummy sediment that clogs the filters in engines, and accumulated water from condensation would permit microbial growth. If well protected and filtered before use, stored fuel might still be good after a decade or so before you’d need to start finding ways to reprocess it for continued use.

Motor vehicles themselves can be kept rolling as components wear out and fail by cannibalising replacements from other automobiles, or improvising. Cuba offers a good contemporary example of this. The 1962 US embargo abruptly isolated the island from imports of American technology or machine components. Many of the cars still on the road today are classic models, nicknamed Yank Tanks, dating back to before this cut-off. The only reason these vehicles are still working fifty years later is the ingenuity of Cuban mechanics, who improvise repairs or harvest replacement components from other cars ‘parted out’. These repairmen are forced to be increasingly ingenious as the pool of working parts steadily diminishes: a pattern that will certainly be repeated on a larger scale during the grace period following the collapse of civilisation.

Whilst fuel stocks and cannibalised parts will keep cars, planes and boats going for a while, the modern GPS navigation devices we have become so reliant upon will malfunction surprisingly quickly after the satellites lose the regular uplink from their command centre. The positional accuracy will drop to about half a kilometre within a fortnight of the cataclysm, around ten kilometres within six months, and the system will be utterly useless within just a few years as the satellites drift out of their precisely coordinated orbits.

MEDICINE

Medical supplies will be yet another crucial foraging target in the aftermath. Ensuring access to classes of pharmaceuticals like analgesics, anti-inflammatories, antidiarrhoeals and antibiotics will help keep you and your companions comfortable and healthy. Deserted hospitals, clinics and pharmacies are not the only repositories of vital drugs – you should also look in pet shops and vet practices. Antibiotics marketed for farm and pet animals, and even for aquarium fish, are exactly the same as for humans and should not be overlooked.

Other everyday items are also worth gathering as they can be re-appropriated for medical uses. One of the earliest uses of superglue (cyanoacrylate adhesive) was for rapidly closing wounds of US soldiers during the Vietnam war. This application would become very important again in preventing life-threatening infections in a post-apocalyptic world if there is no immediate access to sterilised suturing needles and threads. First thoroughly wash out the wound and cleanse it with antiseptic, perhaps purified ethanol which you have distilled yourself (see here). Then pull the lips of the wound together, administer the superglue only along the surface to bridge the gap and hold it closed.

The main concern, however, will be how long a stash of medications will last before they expire. In the early 1980s, the US Department of Defense found itself sitting on a $1 billion stockpile of drugs that were about to exceed the printed expiry date, and the prospect of having to replace that reserve every two to three years. It commissioned a study by the Food and Drug Administration to test over a hundred different medicines to see how long each one remained effective. Astonishingly, about 90 per cent of the drugs tested were still effective beyond their supposed expiry date, and in many cases their actual persistence was substantially longer. The antibiotic ciprofloxacin was still good after a decade. A more recent study found that the antiviral drugs amantadine and rimantadine remained stable after twenty-five years of storage, and theophylline tablets, prescribed for respiratory diseases like COPD or asthma, still exhibited 90 per cent stability more than three decades later. On the whole, it is estimated that most drugs will still be largely effective several years beyond the expiry date given by the pharmaceutical company, even if the sealed packaging has been opened. And with modern blister packs, which protect each individual pill from degradation by moisture and oxidation from the air until the moment it is needed, the persistence could be substantially longer. So if you’re facing a potentially life-threatening infection you’ll almost certainly take your chances with a pack of antibiotics, even long expired. Although the potency of a pharmaceutical will decline as the active ingredient in the tablet chemically degrades, there’s no great risk that it will harm you.

WHY YOU SHOULD LEAVE THE CITIES

You might think that the worst thing about any city is the other people: dense swarms pouring along the streets or jostling each other on to the subway, immersed in the roaring soundscape of traffic, car horns and sirens. After a catastrophic depopulation the silent tranquillity of a deserted metropolis would be pretty eerie at first, but might become very pleasant. Yet although the dead cities will be phenomenal resources for scavenging the materials needed for rebuilding, it’s unlikely you’ll be able to continue living there.