When the portals came, the world changed.
In their millions, barely visible to the eye, they appeared simultaneously across every border. Some were in the air, some were on land, some were underwater. Many were found stuck halfway in the ground, some were even underneath it. All had roughly the same shape and appearance, a spherical tear forming a transparent rupture in the air, and each portal linked to another somewhere on the planet, seemingly at random. One on the ground might lead to the edge of the atmosphere, another in a street during the day could take you to the top of a skyscraper at night in another part of the world.
Millions of people were killed and injured on the 15/3/2019. Firstly, despite not visibly leading anywhere, the pressure difference on either side of the portals when they popped into existence meant anything nearby was either violently sucked through as if into a vaccuum or exploded outwards. A bus in London and several vehicles, whilst not immediately destroyed, were pulled through a twenty-meter rupture that opened up on a busy junction. The portal lead to another a few meters off of a peak in the Andes, where the UK residents were shot out with force over a glacier. Only one survived, who days later somehow managed to make it down to a village below, miraculously contending not only with the below-zero conditions and rough terrain but also other holes that had opened up around the side of the mountain.
Busy cities found themselves brought to an immediate standstill. Thousands of American citizens were killed by a large portal that opened up in central New York, bringing with it a massive explosion of deep ocean water. Several buildings were toppled by the force and many survivors found themselves in the swirling waters of the bay, where several smaller fissures had formed whirlpools.
Some were lucky to escape, most were drowned or sucked under to either die or find themselves coughing up water on a lonely pacific reef island.
Airline pilots suddenly found themselves struggling to control planes as portals opened up in the sky. The gulf stream was broken up in several places, forming massive eddies across the globe. Whilst many died as planes fell out of the sky or were sucked literally into the oceans and rocks below, one Airbus A30 pilot managed to land despite flying immediate into a portal in Argentina on its arrival and being flung into the upper atmosphere somewhere above Canada. That he didn't manage to collide with further portals, which fortunately for many pilots had a physical presence on radar, was considered a miracle.
The immediate change was geographic. Different climates, pressures, and atmospheres all being slammed together, without rhyme or reason. lead to biblical flooding and chaotic weather patterns. This wasn't to settle for many years to come. Towns and villages disappeared or were destroyed and all major cities were left in disarray. In some parts of the globe, even topography was changed. One rural area in China was completely wiped out as Saharan sand poured through in vast quantities, leaving a hole in eastern Morocco. Whereas a vast swathe of Australian desert was covered in snow overnight from a portal in a remote part of Alaska.
Some countries were fortunate enough to initially survive with some form of governence intact. Usually these were in places where the infrastructure was still running, where power stations were still working and communication lines miraculously not cut off. The portals only existed in the bounds of the earths atmosphere, so satellites were still working. However despite this, global telecommunications was for a period of weeks brought to a near-standstill as huge electromagnetic storms washed over both hemispheres.
By some outrageous fortune, the internet managed to stay functional for many places. Initially some thought that it was saved by undersea cables being laid below a line where the portals seemed to cease. It was also pure luck that the American servers keeping it running hadn't been affected by a blackout.
However, national, let alone international governance, was proving near enough impossible. Many cities descended into chaos as humans fought for survival beyond the initial impact of the portals. Smaller, regional governance was hanging by a thread in areas across the globe where communcations were intact and through this many pulled together. Some were lucky enough to have contact with central government. Several South American countries reliant on less high-tech forms of communication and more prepared for natural disasters were the first. The Chinese were the first superpower to manage to put together some kind of order, closely followed by the States.
Yet on top of the immediate impact on locals, there was also the problem of disparate communities suddenly being thrown together. As an example, a group of indiginous Philipino tribesmen found themselves wandering around the chaos streets of Krakow. Fortunately they were taken in by the withered local authorities before they came to any harm. Elsewhere a regiment of North Korean troops on an armed exercise outside of Pyonyang were collectively dumped outside a central Tokyo police station resulting in a standoff where many were killed.
Yet even as people were being brought together, the atmospheric changes the portals brought began to wreak further havoc. Massive storms and tornadoes came down globally as pressure fronts changed and many millions more were killed. The weather couldn't normalise, wind patterns irrevocably changed, bringing north and south together. It would eventually settle into pattern but global temperatures rose for several years before reaching a plateau. As the ice caps shrunk further and glaciers formed elsewhere, there was more flooding.
But as if nature working against humanity wasn't enough, there were further clashes as ideologies came together. China, Russia and the US, even though many areas within each were quickly developing stable social structures, couldn't stop bloody battles for resources that broke out around various interconnected portals. It was considered fortunate that all-out war was near-enough impossible and doubly so that many countries weren't as nuclear capable as had been previously made out. The worst hit were areas where religious ideologies came crashing head to head.
The portals, it must be noted, didn't bring about the apocalypse. Many areas of the globe were brought underwater and some places became a general no-go, but life on earth somehow clung on, even if many species of plant and animal life were to be made extinct.
After the decades of disease and death, those societies that had organised themselves through the years globally finally managed to cope with the initial catastrophic changes. Efforts were made by groups of organised scientists in the more functional areas of human society to figure out solutions to the continuing crisis. A back-to-basics approach was figured out and self-sustenance was one of them. Portals started to be mapped. To begin with this itself brought problems of organisation and, again, violent confrontation. Some parts of humanity started to block portals off from others, in others new alliances were forged. A great population movement began into areas less affected by the ruptures. Humanity begun anew its battle with itself, only now the borders were less invisible lines on a map and more invisible shapes in the sky.
As you would expect, eventually there came the question of what brought the portals. The question of whether it was a cruel intelligence, or a natural occurence - or maybe final proof of the existence of some spiritual entity. The portals became the subject of intense scientific and theological scrutiny. Whilst their cause was never categorically discovered, eventually a portal in the Causcaus was settled on as a clue.
Like many other fissures, there were local tales told of people and animals that had wandered in and had never come out, so it had been avoided on the assumption that death had awaited in some form on the other side. However, one day a man, driven to suicide by the death of his wife, somehow managed to get past the men guarding it and run into the portal. As he disappeared, a guard pulled his hand and forced him back down to the ground.
Before he died, skin red raw and gasping for air, his last word was - "...beautiful."
A team of scientists, arriving days later, sent through a robotic exploration vehicle similar to those used many years ago prior on Mars, bringing back pictures of an alien vista beyond. There lay a flat, rocky plane, massive organic forms silhouetted on a twisted horizon reached into a swirling green sky that crackled with lightning. When they turned the device back to view the portal itself, it was shown to be held in place by a black device, that on testing was revealed to be made out of some forged metal alloy. It stood against thousands of others that spread out to either side for what seemed like miles.
Further tests showed that the device was keeping the poisoned atmosphere of the world beyond out from ours. Yet before anything else could be deduced, the robot seemed to short something on the mysterious creation and the portal blinked out, along with every other portal on the planet.
In the years of ensuing chaos caused as they snapped shut, the alien portal was forgotten. But the portals themselves became forever embedded in the Earth's history, changing what we knew and understood about the universe forever.