What if a meteor hit us now? What happens after that?

One small enough to destroy a small country is enough to destroy the world.

What do you think happens to all the rock that was inside the crater before the crater was formed?
It doesn't just disappear, it's violently thrown out of the crater, some of it all the way into space where it rains back down on the earth, creating hundreds or thousands of smaller craters, it's called "ejecta"

Now, when all of this ejecta is thrown back to Earth and generates a lot of heat as it moves through the atmosphere, that heat has to go somewhere, so it warms the surrounding air raising atmospheric temperature. But, it's not the only thing doing so, remember all of those smaller craters?

Each impact releases enough energy to create a small firestorm, you now have thousands of small fires burning for thousands of miles from the initial impact. These will be the largest and most violent forest fires in recorded history. They will warm the atmosphere and release billions of tons of soot, this will be a problem in a few weeks.

As the fires consume everything and burn out things begin to cool down. The water boiled off from plants, rivers, and streams begins to condense into clouds and then rain. Acid rain falls across the world, poisoning areas that were lucky enough to survive the first few days. People, crops, and livestock start to die off in areas that were previously survivable. This lasts for a few weeks while the soot in the upper atmosphere cools the planet.

It continues cooling the planet until we enter a state of impact winter, which is the same as volcanic winter or nuclear winter but with a different mechanism behind it.

Depending on how big the impact and firestorms were, this could last between decades to centuries, then things start to return to normal.

If any humans survive at this point, we'll probably be starting over from the bronze age.

Not one big enough to cause another great extinction, but small enough to just turn a whole small country and parts of neighboring ones into a huge crater.

...That's a global extinction level event right there. The Chicxulub crater is about 120 miles in diameter, and and 12 miles deep. That's the meteor that resulted in the die-off of all the dinosaurs. To put that in perspective, Slovenia--which is a pretty small country, geographically and culturally speaking--is about 70 miles north to south, and 140 miles east to west. An meteor that turned most of Slovenia into a crater, and parts of Croatia and Austria would also end up causing the same kind of global extinction that was caused 66M years ago. The resulting explosion from that kind of impact would immediately wipe out around 1/4 or Europe from the pressure wave. The vaporized rock would fill the atmosphere, and cause an immediate ice age; you could expect to see global famines due to crop failures, and an immediate drop in global temperatures of >3C.

Any meteor that turns an entire country (aside from countries like The Vatican, Monaco, etc.) into a crater is going to cause a global extinction event.

It depends on how small the country is.

The Vatican? Italy is pretty hosed for a while and there will be a lot of devastation in the areas.

A crater the size of any small country or large city is going to have massive worldwide weather impacts. the one 65 million years ago has a crater about the size of Belgium. Luxemburg is like 1/10th the area and 1/10 of the damage that wiped out the vast majority of life is going to wipe out a very significant chunk of life. Depending on where it hit, it would most likely cause mass die offs downwind for sure and probably drop the world average temps for years.

I'll bet there is a website that calculates this stuff, but I don't time to check one out at the moment.

I don't think anyone would care about rebuilding a crater while the rest of the world collapses.

Depending on the countries destroyed, the Internet might suck a whole lot more.

There will not be an evacuation, since we don't usually know space rocks are coming. It has only happened a couple of times we've seen a rock before it hits the Earth (with all of them being small and burning up in the atmosphere). One time I got an alert because the thing was coming down near me (and I'm a total nerd being subscribed to such a thing), I went outside and looked up and even though it was clouding I saw a big shooting star.

We've mapped a lot of stuff in the solar system, so we can be fairly sure anything big coming near Earth isn't going to hit in the coming decades. But there can always be something we miss, something large enough to take out a city. We are getting better at spotting it, but lead times are hours not days or weeks.

If you are talking about evacuating a city, that's a tall order in a couple of days in the best conditions. Evacuating an entire country (small country, say 15-25 million people), I don't know if that's even possible, that's never been done.

After everything is said and done, recovery will take years. Something that big will cause a mini ice age with lower temperatures for a couple of years, this wrecks food production around the world. We've learned the last 10 years how vulnerable our logistical processes are. Something like a big meteor impact will be much much worse. https://en.wikipedia.org/wiki/Little_Ice_Age

Because it takes say 20-30 years to get to some kind of recovery, most people will have to live somewhere else and get rooted there in that time. But knowing humans, we will probably claw back the land. Look at Hiroshima for example, completely wasted, now a beautiful city. Something on the scale of an entire country has never been done, but it can be done. New people would settle the land during the recovery, but most likely the original culture and ethnicity gets diluted and maybe lost with people spreading out.

Depending on what exactly happens there will be less refugees than say for example a big war. If a big city is hit directly, it can easily kill everyone in the city, comparable to a nuclear strike. It hard to say, because if the meteor is big enough to destroy the entire country, that's an ELE. Most likely there's something that destroys like a city and the rest of the country will have issues with the fallout, but that's manageable.

It also really depends on where the strike hits, if it's a country like Australia with densely populated cities and a whole lot of nothing, a strike can kill a lot of people and leave the country relatively unaffected or even hit and kill nearly nobody. If the strike is in for example Luxembourg, the country simply stops existing and every inhabitant is dead.

It's an interesting question and would require a sophisticated model. As others have pointed out, the size, velocity, and density of the object and the amount of warning time are all critical variables. The target location is also a critical variable. Some countries have friendly neighbors who would want to help. Other countries have hostile neighbors. Some countries have a culture and infrastructure that would have a chance of executing a swift and semi-orderly evacuation. Many would not. Many populations would panic and there would be mass chaos.

This would be a fascinating thing to train an AI on to see what sorts of answers/hallucinations it comes up with. Apply for a grant and get on it!

A very very very big explosion

Probably depends on how much aid the country get's to rebuild. I assume most people would want to go back if that was an option. But if that's not a viable one, they will get refugee status elsewhere and settle there.

https://youtu.be/-9NMt42il4Q

There is a country expected to be submerged in the near future. They are trying to aquire some new space for thier country to exist. I imagine similar if there were enough survivors.