If there was a nuclear war that decimated the world's population, what would the world be like after it? I've heard of nuclear winters and radiation sicknesses and such, but I don't really have a good picture of what would happen, and i'm suddenly curious. Can people explain/direct me to information please?
Nuclear war would be more devastating in global economic terms than in immediate loss of life. You'd count on big parts of the world being mostly unchanged. Every (current) nuclear player is in the northern hemisphere and wind patterns would keep fallout from the north from ever reaching the south at any dangerous level. In fact, fallout in lethal doses can only travel so far. It can contaminate food and livestock at great distances, but if your choice is cancer in a decade or starvation now, most people will choose to eat.
In the immediate area of attacks, you'll have an area that will be uninhabitable for awhile (measured in years or at most, decades), but radiactive elements decay, that's what they do. Surrounding these areas, for some distance downwind, you'll have areas that will have suffered little from the blast, but took fallout. Fallout is hard to see and experience until it's too late. It's just dust from material burned by the blast and carried on the wind until it setles to earth. The more material vaporized by the blast (this is basically depedent on how close the bomb was detonated to the ground), the more fallout. These areas would be quickly abandoned as people figured out their situation and fled. Most would probably wander into the wilderness and there die of radiation poisoning they've already received anyway if not starvation or complications from exposure later. Basically, more would die in the months following the attacks due to radiation and the panic it creates than would die in the actual attacks.
After about three or four months, even areas hard hit by fallout will be fairly safe to reoccupy. However, the fallout will still be there and it will still contaminate nearly everything. If the food was exposed to radiation, it's probably still safe to eat, the problem is moreso eating food with particles of fallout on it. These particles could enter your body and stay there, pumping out gamma radiation until they've decayed fully, which may be well after you've died even a natural death. Dust masks would be popular fashion accessories among survivors. Remember: crops in the field were dusted and would be unsafe, but grain in silos, granted it wasn't exposed to the air would be fine.
The attacks will cause untold amounts of environmental damage. Fires will rage within the cities and their outskirts and no one will be there to put them out. The blasts could also hit things like oil refineries and chemical plants which will likewise burn and could have a deadly impact on survivors too. Smoke and dust in the upper atmosphere may cool the planet briefly, but a long-lasting nuclear winter is unlikely. Every year, volcanoes pour tons of material in the atmosphere and hardly make a dent in the climate. Man can't do in one day what a volcano can over the course of a year.
The places that are hardest hit will be determined by the war. It all depends who strikes first and how the counterattack is planned. Since both sides have early warning systems, they may choose to simply attack the economics of the target country, knowing full well that they won't be able to hit the missiles in their silos before they launch. Each side will want to hit airports where their respective bombers could land.
In any event, electricity is going to be the first thing to go. The electromagnetic pulse from a nuclear blast anywhere near a power grid will overload it. Modern electronics will likewise be hit by this pulse and they're likely to fail also. The end result is a total blackout: no electricity, no communications. After the attacks, the means of repairing the grid will be out of service for some time. Depending on how close they are, power lines will be damaged just by the heat of the blast and power poles will be knocked over. Even with generators, your fuel supply will be severely interupted. If your generator depends on electronic fuel injection, the electronics may be fried by the blast even if it's far enough away to physically survive.
On that note, modern automobiles use electronic fuel injection and the components within this system are subject to EMP. The same will hold true for locomotives and even modern aircraft may be unusable due to electronics damage. On the upside, older autos will work just fine. The downside is that these are less fuel efficient and fuel supplies will be very limited.
Houses that are even some distance from the blast may lose some or all of their windows. Boarded up windows will be a common sight, and since people can't simply go buy boards anymore, they'll use whatever they can find. If your house lacks a fireplace, you may have a hard time with winter heating. There may be no gas, no electricity, and no running water for years to come.
This brings up another problem: buying things will be next to impossible. Credit cards won't work. Cash might, but it might not depending on who you're working with. Trade goods will, but what will you trade? How will you eat? Can you garden enough to feed yourself and your family for years on end? This is when the real die-off starts. Those that survived the initial attack and the fallout are now living without electricity, without running water, and increasingly without food. People will get sick and die because they're malnourished and no more medicine is being produced. People will continue to get sick from radiation as they eat contaminated food out of desperation. Without clean water, it's hard to decontaminate food. Vermin will overtake food stocks without the production of pesticides. People will starve.
International help may come, but they'll be dealing with problems all their own. Even as this aid arrives, will it be enough? There will be problems in transporting it and keeping it viable to distribute.
Rebuilding will be difficult with an ailing workforce. The entire infrastructure will need repairs and many of the skilled workers we previously had will now be dead.
On the plus side, there will be a labor shortage thanks to the famine, so nearly everyone will be employed. If only by the UN for your daily MRE.
So yeah, nuclear war is bad.