If humans were to become extinct, what would the Earth look like a year later? - Essie, age 11, Michigan
Have you ever wondered what the world would be like if everyone suddenly disappeared?
What would happen to all our stuff? What would happen to our homes, our schools, our neighborhoods, our cities? Who would feed the dog? Who would mow the lawn? Although it's a common theme in movies, TV shows, and books, the end of humanity is still something strange to think about.
But as an associate professor of urban design-that is, someone who helps towns and cities plan what their communities will look like-it's sometimes my job to think about these kinds of prospects.
So much silence
If people just disappeared from the world, and you could come back to Earth a year later to see what had happened, the first thing you would notice wouldn't be your eyes.
It would be with your ears.
The world would be silent. And you would realize how much noise people make. Our buildings are noisy. Our cars make noise. Our heaven is noisy. All that noise would stop.
You would notice it again. After a year without people, the sky would be bluer, the sky clearer. The wind and the rain would scrub the surface of the earth clean; all the smog and dust that humans create would be gone.
Home sweet home
Imagine that first year when your home would be unencumbered by anyone.
Go into your house - and hope you're not thirsty, because there would be no water coming out of your taps. Water systems require constant pumping. If there is no one at the public water supply to manage the machines that pump water, then there is no water.
But the water that was in the pipes when everyone disappeared would still be there when the first winter arrived - so with the first cold snap, the frigid air would freeze and burst the water in the pipes.
There would be no electricity. Power plants would stop working because no one would monitor them and maintain the fuel supply. So your house would be dark, without lights, TV, phones or computers.
Your house would be dusty. In fact, there is dust in the air all the time, but we don't notice it because our air conditioning systems and heaters blow air around. And as you walk through the rooms of your home, dust also continues to move. But once all that stops, the air in your house would be still and dust would settle everywhere.
The grass in your yard would grow - and grow and grow until it became so long and limp that it wouldn't grow anymore. New weeds would appear, and they would be everywhere.
Many plants you have never seen before would take root in your garden. Every time a tree drops a seed, a small sapling can grow. There would be no one to pull it out or cut it down.
You would notice a lot more insects buzzing around. Remember that people tend to do whatever they can to get rid of bugs. They spray the air and ground with insect spray. They remove insect habitat. They placed screens on the windows. And if that doesn't work, they beat them down.
Without people doing all these things, the bugs would come back. They would have free rein over the world again.
On the street where you live
In your neighborhood, critters wandered around, watching and wondering.
First the little ones: mice, marmots, raccoons, skunks, foxes and beavers. The latter may surprise you, but North America was once rich in beavers.
Larger animals would come later: deer, coyotes and the occasional bear. Not in the first year maybe, but eventually.
Without electric light, the rhythm of the natural world would return. The only light would come from the sun, moon and stars. The nocturnal creatures would feel good if they had their dark skies back.
Fires would occur regularly. Lightning can strike a tree or field and set bushes on fire, or strike houses and buildings. Without people to put them out, those fires would continue until they burned themselves out.
Around your city
After just a year, the concrete - roads, highways, bridges and buildings - would look much the same.
If you came back, say, ten years later, cracks would have appeared, with little plants wiggling through them. This happens because the Earth is constantly moving. With this movement comes pressure, and with this pressure comes cracks. Eventually the roads would crack so much that they looked like broken glass, and trees would even grow through them.
Bridges with metal legs slowly rust. The beams and bolts that hold the bridges up would also rust. But the large concrete bridges and highways, also made of concrete, would last for centuries.
The dams and dikes that humans built on the world's rivers and streams would erode. Farms would revert to nature. The plants we eat would start to disappear. Not much corn, potatoes or tomatoes anymore.
Farm animals are said to be easy prey for bears, coyotes, wolves and panthers. And pets? The cats would become feral - that is, they would become wild, although many would be preyed upon by larger animals. Most dogs wouldn't survive either.
Like ancient Rome
A thousand years from now, the world you remember would still be vaguely recognizable. Some things would remain; it would depend on the materials they are made of, the climate they are in, and just plain luck. An apartment building here, a movie theater there, or a crumbling shopping center would be monuments to a lost civilization. The Roman Empire collapsed over 1,500 years ago, yet you can still see some remnants of it even today.
If nothing else, the sudden disappearance of humans from the world would reveal something about the way we treat the Earth. It would also show us that the world we have today cannot survive without us and that we cannot survive if we do not care about it. To keep it functioning, civilization - like everything else - requires constant maintenance.
Hello, curious children! Do you have a question that you would like an expert to answer? Ask an adult to send your question to CuriousKidsUS@theconversation.com. Tell us your name, age and the city where you live. And since curiosity knows no age limit - adults, let us know what you're wondering too. We won't be able to answer all questions, but we will do our best. This article is republished from The Conversation, an independent nonprofit organization providing facts and trusted analysis to help you understand our complex world. It was written by: Carlton Basmajian, Iowa State University Read more: Carlton Basmajian does not work for, consult with, own shares in, or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.