What happens on a building site before the first floor goes up?
Before building a skyscraper, engineers drill test holes to learn what the soil and rock are like. Then crews dig a giant hole and haul away the dirt. Next, they build the foundation. Many towers stand on huge concrete columns called piles that reach deep into the ground, so the weight of the tower is held safely. Only after this hidden work can the building start to rise.
Why do tall buildings have a steel skeleton?
A skyscraper's strength comes from a frame of steel columns and beams, like a skeleton. The frame carries the weight of the floors, walls, and people down to the foundation. Steel is strong and can bend a little without breaking, which helps in wind. The walls hang from the frame, so they can be thin and light.
When was the first skyscraper built?
Many people call the Home Insurance Building in Chicago, finished in 1885 with ten stories, the first skyscraper. It used a frame of iron and steel, which let buildings grow much taller than thick brick walls could. Safe elevators, invented earlier, made people willing to use tall buildings. Soon cities across the world were reaching up.
How tall is the tallest building in the world?
The Burj Khalifa in Dubai is the tallest building in the world. It is 2,717 feet tall, with 163 floors, about twice as tall as the Empire State Building in New York. It tapers as it rises, and from the top you can see for many miles. Engineers had to design it carefully for wind and for very hot weather.
How does a tower crane grow taller as the building grows?
A tower crane stands on a tall mast. To climb higher, a special frame slips around the mast, lifts the top section of the crane, and lets workers slide a new piece of mast into the gap. The crane then rests on its taller mast. A counterweight at the back balances the load being lifted at the front. Operators work from a cab or by remote.
How does concrete get to the top of a tall building?
Concrete is brought by trucks with spinning drums that keep it mixed so it will not harden. At the building, a powerful pump pushes it through steel pipes all the way up, sometimes hundreds of feet. Workers pour it into frames called forms and let it harden around steel bars. At the Burj Khalifa, concrete was pumped to nearly 2,000 feet.
Why can a skyscraper have walls made mostly of glass?
In a skyscraper, the steel frame holds the weight, so the outer walls do not have to. The glass panels simply hang from the frame like curtains, which is why they are called curtain walls. The glass can have thin coatings and layers of air to keep heat in or out. Big windows let in daylight and give people great views.
How does the golden ball inside Taipei 101 keep the tower steady?
Some tall buildings sway a little in strong winds. Taipei 101 in Taiwan has a huge golden steel ball, about 18 feet wide and weighing about 660 tons, hanging from cables inside the tower. When wind pushes the building one way, the ball swings the other way and cancels part of the motion. Giant shock absorbers slow the ball. This kind of weight is called a tuned mass damper. Visitors can see it.
Why do skyscrapers have metal rods on top?
Tall buildings are likely to be hit by lightning. A metal rod at the top, called a lightning rod, gives lightning a safe path. Thick cables connect it to the ground, so the electricity flows around the building and into the earth. Benjamin Franklin invented the lightning rod in the 1700s. The Empire State Building is struck about twenty times a year.
How do elevator brakes and floor sensors keep riders safe?
An elevator has several safety systems. A speed governor watches how fast the car moves, and if the car goes too fast, safety clamps squeeze the steel rails along the shaft and stop it. Sensors and a computer track which floor you are on and stop the car at the right place. Door sensors stop the doors from closing on people. Inspectors check elevators regularly.
How do tall buildings stay safe from fire?
Tall buildings have many layers of fire safety. Sprinklers spray water when heat is detected, and alarms warn people. Steel is covered with a fireproof coating, because steel gets weak when very hot. Fire doors and strong stairwells give people a safe way to leave. People should use the stairs, not the elevators, in a fire. Practicing fire drills helps everyone know what to do.
What makes the CN Tower in Toronto so special?
The CN Tower was finished in 1976 and stands 1,815 feet tall. For over 30 years it was the tallest free-standing structure in the world. It is used for TV and radio signals, and visitors can ride a glass elevator to see the city. It has a glass floor, and the tower is hit by lightning about 75 times a year.
How do window washers reach the 60th floor?
Window washers ride on platforms that hang from cables attached to a rig on the roof. They wear safety harnesses connected to strong anchor points. Some buildings have tracks and machines that move up and down the glass. Washers clean with soapy water and squeegees. They do not work when it is windy or stormy, because safety comes first.
What makes a skyscraper green?
A green skyscraper is designed to use less energy and water. It might have special windows that block heat, sensors that turn off lights when no one is in a room, and sunshades. Some collect rainwater to flush toilets and water plants. Rooftop solar panels and gardens help, too. These ideas save money and are kinder to the environment.
What gear keeps skyscraper builders safe up high?
Workers wear hard hats, bright vests, strong boots, and safety harnesses clipped to secure points. Edges have railings and nets, and tools are tied so they cannot drop. Cranes use signals and radios so everyone knows what is happening. Work stops in high winds or lightning. Careful planning and training mean that safety comes first on a building site.
What is on the roof of a skyscraper?
A skyscraper roof is crowded with equipment. There are machines for elevators, big fans and cooling units for air conditioning, antennas for radio and phones, and sometimes water tanks. There may be a rig for window washers, lightning rods, and red lights to warn airplanes. Some roofs have gardens, solar panels, or a helicopter landing area.
What do architects and engineers each do?
An architect designs how a building looks and works, such as where rooms, windows, and doors go. Structural engineers figure out how strong the beams and columns must be to hold everything up. Other engineers plan the heating, cooling, electricity, and water. Builders put the plan into action. Together, they make a building that is useful, beautiful, and safe.
Why is it so windy at the foot of a tall building?
When wind hits a tall wall, it cannot go through, so some goes up and some is pushed down toward the street. The air also speeds up as it squeezes around corners and between buildings. This can make strong gusts in plazas. Architects test models in wind tunnels, and add trees, canopies, and curved shapes to calm the wind.
Why are some skyscrapers rounded, tapered, or twisted?
Wind swirling around a tall building can make it wiggle. A shape that changes with height, like a tapering tower or one with a twist, confuses the swirls so that they don't line up and push in rhythm. Rounded corners also make wind flow more smoothly. The Burj Khalifa has a stepped, Y-shaped design for this reason, and it is also pretty to look at.
Can a skyscraper be made of wood?
Yes. Engineers glue layers of wood together crosswise to make mass timber, such as cross-laminated timber, which is strong and fire-resistant because the outer layer chars and protects the inside. Mass timber stores carbon and can be built quickly. A student residence at the University of British Columbia, finished in 2017, is 18 stories tall and built with wood.
How are old buildings taken down safely?
When a building is no longer needed, crews plan carefully. They remove materials that could be harmful, then take the building apart piece by piece from the top using machines or by hand. Most of the concrete, steel, glass, and wood can be sorted and recycled. Experts set up fences and sprays to keep dust and noise low. It is the building process played backward.
How do builders make sure a tall building is straight?
Builders check every column with tools. An old method uses a plumb bob, which is a weight on a string that hangs straight down because of gravity. Today they use laser levels and surveying instruments that measure to a fraction of an inch, and GPS to check the whole tower. A building may lean very slightly in wind, but it swings back.
How do engineers know how much weight a floor can hold?
Engineers calculate the weight of the building itself, plus people, furniture, and equipment, and then multiply it by a safety factor so the floor is much stronger than it needs to be. Signs in libraries and storage rooms tell you the maximum weight. Floors are made of strong concrete and steel. Testing in labs checks the numbers.
How do big buildings stay warm in winter and cool in summer?
Big buildings have heating and cooling systems with boilers, chillers, ducts, and fans. Air is heated or cooled in machines and sent through ducts to every room. Sensors and thermostats adjust the temperature in different zones. Filters clean the air. Smart controls and good insulation save energy. Some systems recover heat from the air leaving the building.
How do computers help design a building before it is built?
Architects and engineers use computers to make a 3D model of a building, showing every beam, pipe, and wire. They can test how sunlight falls, how wind moves, and how people would walk through it. The software finds mistakes, like pipes that would bump into beams, before anything is built. Some teams even take virtual reality tours.
How do traffic lights know when cars are waiting?
Many intersections have a loop of wire buried in the pavement. A small electric current runs through it, and when a car sits on top, the metal changes the loop’s magnetic field, which tells the light’s computer that a vehicle is waiting. Other lights use cameras or radar. This lets the signal change when needed instead of using a fixed timer. Engineers also time lights along a street so cars at the speed limit meet green after green.
Why do crossing guards hold up a big STOP sign?
Crossing guards help children and other walkers cross busy streets near schools. A guard steps into the road only when it is safe and holds up a big STOP sign so drivers can see the signal from far away. Drivers must stay stopped until the guard and everyone crossing have left the road. Guards wear bright vests so they can be seen in any weather.
Why are stop signs red octagons?
A stop sign needs to be spotted fast, even from far away or from behind. No other sign has eight sides, so the octagon shape is unique, and the red color means stop or danger. Because of its shape, you can recognize it even when snow covers its face. Different shapes mean different things: triangles warn about yielding, diamonds warn of hazards, and rectangles give information.
How do road builders make a road layer by layer?
A road starts with leveled, packed soil. On top go layers of crushed stone that spread out the weight of traffic and let water drain away. Finally, workers lay hot asphalt or pour concrete on the top. The road is slightly higher in the middle, so rain runs off to the sides. Big machines like graders, pavers, and rollers do the work.
Why are some roads black and some light gray?
Black roads are made from asphalt, which is a sticky black material from oil mixed with stones. It is quick to lay, bendy, and quiet to drive on. Light gray roads are made of concrete, a mix of cement, sand, and gravel. Concrete is hard and long-lasting but can crack and thump at joints. Each is chosen to fit the job, climate, and cost.
How do potholes form each winter and spring?
Water seeps into small cracks in the road. When it freezes at night, it turns to ice and expands, making the crack bigger. When the ice melts, a gap is left under the pavement. Then cars and trucks drive over the weak spot and break off pieces. After several freezes and thaws, a hole appears. Crews fill potholes with fresh asphalt.
Why do roads have painted lines, and what do solid and dashed lines mean?
Painted lines tell drivers where each lane is and which way traffic goes. In Canada and the United States, yellow lines separate traffic going in opposite directions, and white lines separate lanes going the same way. A dashed line means drivers may pass or change lanes when it is safe, and a solid line means stay in your lane. Crews repaint lines often because tires and snowplows wear them away.
How do speed bumps make cars slow down?
A speed bump makes a car's wheels go up and over a little hill. If the car goes fast, the bump jolts the car and everyone inside, so drivers slow down to stay comfortable. Going slowly means a smooth ride. Slower speeds give drivers more time to notice children, pets, and people crossing. They are used near schools and parks.
Why do roundabouts help traffic flow?
In a roundabout, cars go around a circle in one direction and yield to traffic already in it. Because all vehicles enter at a gentle angle and slow down, the crashes that do happen tend to be less serious than at crossings. Traffic keeps moving without waiting for red lights, which also saves fuel. Roundabouts need space, so they don't fit everywhere.
Why do traffic jams sometimes happen even without an accident?
A jam can start when one driver taps the brakes. The next driver brakes a little harder, and the next even harder. The slowdown moves backward along the road as a wave, even after the first driver has sped up again. Scientists have seen this wave in experiments with cars on a circular track. Leaving space and driving smoothly can help.
How does a phone know how slow the traffic is?
A phone uses signals from satellites to find where it is. When many phones in cars are moving slowly on the same road, the map app can see that the road is crowded and color it red. It uses this to suggest faster routes. The information is combined, and the app can learn the usual patterns of busy times.
Why do some cities have lanes just for buses?
A bus carries many more people than a car, so it makes sense to keep it moving. A bus-only lane lets buses skip past traffic jams, so trips are faster and more reliable. More people choose the bus, which means fewer cars on the road. A single bus can take the place of dozens of cars.
Why do some city vehicles hang on wires above the street?
Streetcars and trolley buses run on electricity from overhead wires. A pole or a frame on the roof, called a pantograph, touches the wire and brings electric current down to the motor. For streetcars, the current returns through the rails. Toronto has one of the largest streetcar systems in North America. The wires keep the vehicle from needing a big battery or engine. Stay far away from overhead wires.
Why do you feel wind in a subway station before the train comes?
A train moving in a tunnel pushes a column of air ahead of it, like a piston in a bicycle pump. The air has nowhere to go but through the tunnel and out into the station, so you feel a breeze or gust before the train arrives. When the train leaves, it pulls air along after it. Stand back from the platform edge.
How does an escalator work?
An escalator is a long staircase on a loop. Its steps are linked to a pair of chains, driven around by a motor. At the top and bottom, the steps flatten out, so you step on and off easily. The handrail moves at the same speed. Stand in the middle, hold on, keep your shoes tied, and keep your hands and clothing away from the sides.
Why do bike lanes keep cyclists safer?
A bike lane gives cyclists their own space away from fast-moving cars. Painted lanes help, and protected lanes with barriers or curbs help even more. When drivers and cyclists know where to be, there are fewer surprises. Bike riders should wear helmets, use lights at night, and use hand signals. More bike lanes also mean more people can choose to ride.
How do ambulances and fire trucks get through busy traffic?
Emergency vehicles use loud sirens and flashing lights to tell drivers to make way. When you hear a siren, pull to the right and stop if you can safely do so. Some cities have special systems that turn traffic lights green for approaching emergency vehicles. Trained drivers practice navigating through traffic safely. Making space can help someone who needs help fast.
Why does crossing at the corner and looking both ways work?
A moving car needs time and distance to stop. It first travels while the driver reacts, and then keeps rolling while the brakes work. If a car goes twice as fast, it takes about four times as far to stop. That's why cars cannot stop suddenly. Use crosswalks, stop at the curb, look and listen, and wait until drivers see you.
Why do different countries drive on different sides of the road?
Long ago, travelers on horseback and in wagons chose sides for their own reasons. Over time, countries made rules to keep everyone safe. Canada, the United States, and many other countries drive on the right. About a third of people live in countries that drive on the left, such as the United Kingdom and Japan. Cars are built to fit the rule.
How do street names and house numbers help people find places?
Streets with names or numbers, and houses with numbers, make a map you can read. Often, numbers go up as you move farther along the street, and odd numbers are on one side with even numbers on the other. This pattern helps delivery drivers, visitors, and emergency crews find the right door quickly. A clear number on your house can save time.
Why do some cities have ferries?
Where water cuts a city in two, a ferry can carry people and cars across without needing an expensive bridge or tunnel. Boats float because they push away water equal to their weight, so even big ferries stay up. Toronto's ferries take people to the Toronto Islands. Ferries are important in places like Vancouver and Halifax, too.
How do parking garages stack so many cars?
A parking garage stacks many levels of flat floors, connected by ramps, so many cars can fit in a small footprint. Ramps may spiral or run back and forth. Sensors above each space can detect whether a car is there and light up green or red, guiding drivers to open spots. Walls and ceilings are strong concrete. Take care to stay near the adults in garages.
Why are more city buses powered by electricity?
An electric bus runs on a big battery and a quiet motor. It has no tailpipe, so it makes cleaner air on busy streets. It can also use its brakes to put some energy back into the battery. Buses are charged at night or at stops using special plugs. Because city buses stop and start a lot, electric motors work well for them.
How do traffic engineers count cars?
Engineers use rubber tubes laid across the road that sense each axle as a wheel rolls over it. Cameras and computers can recognize vehicles, and loops in the pavement sense cars passing. The counts show where roads are busy at different times and help plan traffic lights and new lanes. You can count too: sit safely on a sidewalk with a grown-up and make tally marks.
Why do highway ramps curve in big loops?
Highways go fast, so ramps and curves need to be gentle. A loop ramp lets a driver turn off or onto a highway without crossing other lanes or stopping. Shapes called cloverleaf and diamond interchanges let cars change roads on different levels. The curve is tilted a little, or banked, so cars stay on the road. Engineers plan them carefully for safety and flow.
How does water travel through a city's pipes to your tap?
Treated water leaves the treatment plant through huge pipes called water mains buried under the streets. They branch into smaller pipes that run along every block, and a thin service pipe connects each building. Pumps and tall tanks keep the water under pressure so that it flows when you turn on a faucet. Valves let crews shut off sections for repairs.
Why do water mains sometimes break?
Water pipes can last a very long time, but not forever. They can rust, get old, or be pushed by moving soil. Very cold weather can make the ground freeze and shift, putting stress on pipes. When a main breaks, water bubbles out of the ground and may flood a street. Crews shut off nearby valves, dig down, and repair the pipe.
How do fire hydrants work?
A fire hydrant is a handy tap connected to the city's water main. Firefighters attach a hose with a special wrench and open a valve, and strong water pressure from the pipe sends water through. Hydrants have caps on their outlets, and the colored tops can tell firefighters how much water flows. Never open a hydrant yourself, and keep snow cleared away so that it is easy to find.
Why are manhole covers round?
A round cover cannot fall through its own hole, no matter how you turn it, because a circle has the same width in every direction. A square one could slip through diagonally. Manhole covers are heavy iron, sometimes 100 pounds or more, so they stay put under traffic. Workers use special hooks to lift them. Never try to open one.
Why does steam sometimes rise from street grates?
In some cities, underground steam pipes carry heat to buildings, and steam can escape through cracks and openings. Warm underground air meeting cold winter air can also form clouds, just like your breath on a cold day. The steam looks spooky, but it is only water vapor. Crews keep an eye on it, and people should stay away from hot grates.
How do city workers look inside a sewer pipe?
Sewer pipes are underground, so crews send in small robots that roll through the pipes on wheels or tracks. A camera and bright light on the robot send live video to a screen above ground. Workers watch for cracks, tree roots, and clogs, and then decide what to repair. People go into sewers only with special training, air monitors, and safety gear, and nobody should ever open a manhole cover.
What happens at a wastewater treatment plant?
Water from sinks, showers, and toilets flows through sewers to a treatment plant. First, screens catch large objects. Then the water sits in tanks, where solids sink. Tiny microbes eat the leftover waste while air is bubbled through. Finally, the water is disinfected, often with ultraviolet light or chlorine, before it is released to a river or lake, much cleaner than when it arrived.
Why do some sewers overflow when it rains hard?
In some older parts of cities, one pipe carries both rainwater and household wastewater. When a storm brings lots of rain, the pipe can fill up faster than the treatment plant can handle. Extra water may overflow into a river or lake. Cities are building big storage tanks and tunnels, separating pipes, and adding rain gardens and green roofs to soak up rain.
Why are some city wires buried while others hang on poles?
Wires on poles are cheaper to build and easy to fix, but they are exposed to wind, ice, and falling branches. Buried wires are protected from storms and don't clutter the view. However, digging costs a lot, and it can take longer to find and repair a problem. Cities use both, depending on the place.
What are the big green boxes at street corners?
These boxes hold equipment for the city's electric, phone, internet, or traffic-signal systems. They protect electronics from rain and snow and keep people safe from live wires. Some contain computers that control the traffic lights. Never climb on, open, or touch them. In many places, artists paint colorful pictures on them to brighten up the neighborhood.
How does a cell tower pass your phone call along?
A cell phone is a small radio. When you make a call, it sends signals to the nearest cell tower, which has antennas that talk to many phones at once. The tower passes your call along through cables, often fiber, to the next place it needs to go. As you travel, your call hands off from tower to tower. Cities need many towers because each one covers only a small area.
Why is a strong smell added to the gas that heats our homes?
Natural gas has no smell at all, and it can be dangerous if it leaks. So companies add a harmless chemical with a strong odor, often described as rotten eggs, so that people notice a leak right away. If you ever smell it at home, tell a grown-up and go outside. Do not turn lights on or off, and call for help from outside.
Why do towns have water towers?
A water tower is a big tank on tall legs that holds water high above the town. The height makes pressure, because the weight of the water pushes it down through the pipes. It works without extra pumps. The tank also stores water for busy times, such as mornings and evenings. Pumps fill it at night when demand is low.
How does a skyscraper push tap water up hundreds of feet?
The city's pressure alone can only push water up a few stories. In tall buildings, powerful pumps in the basement push water up to the higher floors. Some buildings pump water to tanks on the roof and let gravity feed the floors below. Buildings are divided into zones so that the pressure is never too high at the bottom.
How does cold water from Lake Ontario cool Toronto's downtown buildings?
Pipes reach about three miles out into the lake and draw up very cold water from deep down, near 39 degrees Fahrenheit. In downtown buildings, this cold water passes through heat exchangers that cool the air-conditioning system's own water, then goes on to the city's drinking water supply. The two waters do not mix. It saves a great deal of electricity.
How does a 911 call get help to the right place?
When you dial 911 in Canada, your call goes to an emergency call center. A trained dispatcher answers, asks what is wrong and where you are, and sends police, firefighters, or an ambulance. Phones often help share your location. Stay calm, speak clearly, and know your address. Only call 911 for real emergencies.
How do hospitals keep running during a power outage?
Hospitals have backup generators that start within seconds when the power fails, using fuel stored on site. Some equipment also uses batteries, called uninterruptible power supplies, to bridge the gap. Backup power keeps lights, machines, and heating running so patients stay safe. Other important places, such as water plants and phone systems, have backup power too.
What is under a city street?
Under a city street lie many hidden layers. Large sewer pipes are often deepest, with water mains above them. Electric cables, telephone and fiber lines, and gas pipes lie nearer the surface. In some cities, subway tunnels and steam pipes share the space. Each system has its own depth and location. Maps and markings tell workers what is where.
How do crews fix pipes without digging up the whole street?
Instead of digging a long trench, crews can dig small holes at each end of a pipe. They can then pull a flexible liner through the old pipe and harden it into a new pipe inside, like a sleeve. Another way is horizontal drilling, which pushes a new pipe underground through a drilled path. These tricks save time and keep roads open.
Why are old city pipes replaced with new materials?
Old pipes, made of cast iron, clay, or lead, can rust, crack, or leak after many decades. New pipes made of plastic, ductile iron, or concrete resist rust and last longer. Replacing old pipes keeps water clean and prevents leaks and breaks. Cities do it a few streets at a time because it is big, careful work.
How does a water meter count how much water you use?
A water meter sits on the pipe entering a building. Moving water spins a small disc or wheel inside it, and each turn means a certain amount of water has passed. Gears turn the numbers on a dial. Newer meters use sound waves or send data by radio. The water company uses the numbers to calculate the water bill.
What are the big orange balls on some power lines?
Those balls are markers that make power lines easier to see for low-flying airplanes and helicopters. They are bright orange or white so pilots can spot the wires from far away. Some lines also have spirals or flappers that help birds see them. These simple devices help keep both pilots and birds safe. Stay far away from power lines, and never fly a kite or climb a tree near them.
Why do wires sag between poles?
Wires hang in a gentle curve because of their own weight, and they are installed with some slack on purpose. In hot weather, metal expands and the wires sag more. In cold weather, the metal shrinks and they pull tighter. Ice and wind can add weight and tug. Designers leave enough slack so that wires won't snap in winter.
Why don't drains make your bathroom smell like the sewer?
Under each sink is a U-shaped pipe called a trap that always holds a little water. This water plug blocks smelly sewer gas from coming back up. Small vent pipes, often poking through the roof, let air into the drains so that they flow smoothly and the water in the trap does not get sucked out. If a drain is unused for months, the water can dry up.
How do pumps push water uphill?
Many city pumps have a spinning part called an impeller with curved blades. As it whirls, it flings water outward, which creates pressure that pushes water through the pipe. Pumps run on electric motors and are used in water systems, sewers, and buildings. A pump cannot pull water up more than about 34 feet by suction alone, so it is usually placed to push.
Why do raccoons do so well in cities?
Raccoons are curious and eat almost anything, from fruit to insects to leftovers. Cities give them food in garbage and pet bowls, and places to sleep in trees, sheds, chimneys, and attics. There are few big predators, and winters in the city are often milder. Most raccoons are active at night. Never feed or touch a raccoon, and keep trash bins latched.
Why do coyotes live in some cities?
Coyotes are adaptable animals that eat mice, rabbits, fruit, and sometimes leftovers. City parks, ravines, and golf courses give them places to hide, and there are few big predators to worry them. Most coyotes are shy and stay away from people. If you see one, give it plenty of space, do not feed it, and tell a grown-up.
Why do peregrine falcons nest on skyscrapers?
Peregrine falcons naturally nest on high cliff ledges. A skyscraper's ledge looks just like a cliff to them, and the city has lots of pigeons to eat. Many cities, including Toronto, have falcon nest boxes on tall buildings, and people watch them on webcams. These birds were once rare, and seeing them back is good news for nature.
Why are there so many pigeons in cities?
City pigeons are descended from rock doves, which nest on cliffs. Building ledges are like cliffs, and people drop food crumbs, so pigeons thrive. They have been living with people for thousands of years. Pigeons are smart and can learn to recognize people and landmarks. Feeding them in big groups causes crowding and messes, so it is best to let them find natural food.
How do common nighthawks nest on city rooftops?
Common nighthawks are birds that catch flying insects at dusk. They used to nest on bare ground in open areas, and flat gravel roofs are similar. A mother lays her camouflaged eggs right on the gravel with no nest. You may hear the booming sound of males diving through the air in summer evenings. Nighthawks are listed as a species at risk in Canada.
Why do city birds sing at a higher pitch?
In noisy cities, low rumbles from traffic can drown out deep bird songs. Scientists found that some birds, such as great tits and song sparrows, sing higher or louder in the city so that other birds can hear them. Some even sing at different times of day. Birds adapt to the soundscape around them.
How did crows in Japan learn to use traffic lights to crack nuts?
In Sendai, Japan, scientists saw crows using a clever trick. A crow would drop a walnut on the road in front of cars that had stopped at a red light. After the cars drove over it and cracked the shell, the crow waited until the crossing light turned green for walkers. Then it hopped down to eat the nut safely. Crows solve puzzles and use tools.
Why do Canada geese stay in city parks all year?
Many Canada geese now live in parks and golf courses year-round. Short, soft grass is easy for them to eat, ponds give safety, and few predators bother them. Because food is available, some geese no longer fly south. Geese can be protective of their nests and chicks, so keep a safe distance and do not feed them.
What tiny creatures live on a city sidewalk?
A sidewalk may seem empty, but there is a lot of life in its cracks. Ants build nests under paving stones and follow scent trails for food. Tiny springtails, mites, and sow bugs hide in damp corners, and spiders spin webs in sheltered spots. Moss and small weeds grow in cracks. Scientists have found surprising numbers of species in a single block.
Why do rats live near people, and how can we keep them away?
Rats live where there is food, water, and shelter, and people often provide all three by accident. Open trash, spilled food, and clutter give them homes. Rats are very smart and good at climbing and squeezing through small holes. The best way to discourage them is to keep trash sealed, clean up food, and close up gaps in buildings.
What should you do if you meet a wild animal in the city?
Stay calm and give the animal plenty of space. Watch from a distance and never try to touch, feed, or chase it. Back away slowly, and keep pets on leashes. Tell a grown-up about the animal. Wild animals can scratch or bite if they are frightened, and feeding them teaches them to depend on people, which is not safe for them.
What is a green roof, and how does it help?
A green roof is a roof covered with plants. Under the plants are layers of soil, a drainage layer, a root barrier, and a waterproof sheet. The plants soak up rain, so less water rushes into storm drains, and they keep the building cooler in summer and warmer in winter. A green roof also gives bees, butterflies, and birds a place to live.
Why do cities plant trees along streets?
Street trees give shade, which can make a sidewalk many degrees cooler on a hot day. Leaves catch dust and soak up rain so storm drains do not overflow. Trees give homes to birds and insects, make streets quieter, and are nice to look at. Many people say neighborhoods with trees feel happier. A tree is a helper that never takes a day off.
How do trees survive in tiny squares of dirt in the sidewalk?
City trees have a tough life. They have little room for roots, the soil is often packed hard, and salt from winter roads can harm them. Planners now use special loose soil under the pavement and long planting strips. Mulch and water help. Many cities have crews who water and prune young trees. A tree with room for roots grows better and lives longer.
Why do cities plant many different kinds of trees?
If a street has only one kind of tree, one pest or disease can wipe out them all. In Ontario, a beetle called the emerald ash borer killed millions of ash trees, leaving some streets bare. Planting a mix of species means some trees will survive any problem. Different trees also give homes to different animals and provide color in different seasons.
Why do some cities turn empty lots into community gardens?
Neighbors can grow vegetables, herbs, and flowers on land that would otherwise sit empty. Fresh food is healthy, and working together builds friendships. Many community gardens use raised beds with clean soil. Kids learn where food comes from, and gardens give bees and butterflies a place to visit. Gardens also soak up rain and make the neighborhood greener.
Why do cities need parks?
Parks give people places to play, run, and relax. They also help the environment, because grass and trees soak up rain, cool the air, and give homes to animals. A park can be a place to see birds, watch seasons change, or meet friends. Toronto's High Park has woods, ponds, and a rare oak savanna. Parks are good for body and mind.
Why does Toronto have so many hidden forest valleys?
Toronto sits on soft soil left behind by glaciers. Rivers such as the Don and the Humber have carved deep valleys called ravines into this soil over thousands of years. Because the steep slopes were hard to build on, many were left wild and became forests. Today the ravines cover about a sixth of the city and are home to foxes, owls, and wildflowers.
How can plants grow up the side of a building?
A living wall or green wall is a wall covered with plants. The plants grow in panels that hold soil or special fabric, and a hidden system of pipes waters them. Plants on walls can cool buildings, soak up noise, and brighten a street. Some are inside, in places like airports and malls. Gardeners must take care of the plants as they would any garden.
Why do some parking lots let rainwater soak through?
Regular pavement is waterproof, so rain runs off into drains. Permeable pavement is made with porous material or pavers with gaps in between, so water drains through to a layer of stone and soil below. This reduces puddles, floods, and pollution washed into streams, and it recharges groundwater. It's a way to give rain a place to go.
Why can lichens tell scientists about a city's air?
Lichens soak up water and air straight through their surfaces, with no roots or thick skin to filter them. That makes them sensitive to pollution. Some lichens disappear where the air has a lot of pollutants, while others can live in dirty air. By counting the kinds of lichens on tree trunks, scientists can judge how healthy the air is. More kinds usually means cleaner air.
How do animals cross busy roads safely?
Roads can block animals from finding food and mates. Wildlife crossings, like bridges covered with plants and tunnels underneath highways, give animals safe paths. In Banff National Park, fences guide elk and deer to crossings, and studies show that collisions with animals dropped by more than 80 percent. In cities, small tunnels help frogs and turtles.
Why are some city lawns turning into wildflower meadows?
Mowed grass uses water, fuel, and time, but it does not give much food to wildlife. Wildflower meadows have flowers that feed bees and butterflies, and grasses that give seeds to birds. Their deep roots soak up rain and need less mowing. A meadow can look messy at first, but it is full of life. Some towns set aside strips of land to grow wild.
How can you find the age of a city tree?
The best way is to count the rings in a cut stump, since a tree adds one ring each year, but never cut a living tree. For a living tree, you can measure around the trunk at about chest height and divide by about three to estimate its width. Foresters have charts that estimate age from width for each species. Big old trees are precious.
How can you be a city nature detective?
Anyone can study nature in a city. Keep a notebook and write down what you see: birds, insects, plants, and animal tracks. Take photos and use an app with a grown-up to share them, so scientists can use your observations. Programs like eBird, iNaturalist, and the Great Backyard Bird Count collect data from many people. Your sightings help real scientists.
How does bright night light change the lives of birds and insects?
Many animals use natural light to tell day from night. Migrating birds steer by stars and the Moon, so bright buildings can lure them off course and make them circle until they are tired. Insects swarm around lamps instead of feeding or finding mates. Fireflies can't see each other's flashes. Turning off extra lights helps wildlife find its way again.
What are "lights out" programs for migrating birds?
During spring and fall, billions of birds migrate at night. Bright lit-up towers can confuse them and cause them to collide with glass. In Toronto, a group called FLAP asks building owners to switch off unneeded lights from midnight until dawn during migration. Birds find their way better, and the buildings save energy too. Many cities have joined.
Why are cities switching to LED streetlights with warmer colors?
LED streetlights use about half the electricity of older lamps and last much longer, so cities save money. Because they can be aimed downward, they waste less light into the sky. Cooler, bluer light makes more glare and bothers animals and sleep more, so many cities now choose warmer, amber-toned LEDs. Smart design means lighting where it is needed.
How do smart streetlights know when to dim?
Smart streetlights have sensors that notice motion, daylight, and traffic. When nobody is around late at night, the lights can dim to save energy and then brighten when someone approaches. They can also be controlled from a computer, which reports when a bulb needs repair. Careful use of light saves energy and keeps streets safe.
Why are cities so noisy?
Cities have many sounds: cars, buses, trains, planes, construction, sirens, music, and people talking. Sound bounces off tall buildings and pavement, so it stays loud between buildings. Hard surfaces reflect noise, while soft things like grass and trees soak up some. Cities try to reduce noise to help people sleep, learn, and feel calm.
Why do cities have quiet hours and noise rules?
Loud noise at night can wake people up, and sleep is important for growing and learning. That is why many cities have noise rules, called bylaws, that limit things like construction, leaf blowers, and loud music during late-night and early-morning hours. Quiet zones near hospitals and schools help patients rest and students think. Emergency work, like fixing a broken water pipe, can be allowed at any hour.
How do walls along highways block noise?
A noise barrier is a tall, thick wall that stands between a road and nearby homes. Sound travels in straight lines, so the wall blocks the direct path, and some sound is absorbed or reflected back. The sound that does reach the homes is quieter. Walls work best when they are tall and without gaps. Earth mounds with trees can also help.
How do thick windows keep city noise out?
Sound is a vibration, and glass vibrates when sound hits it. Double and triple windows have two or three panes with a gap of air or gas between, and the panes are often different thicknesses. The vibrations lose energy as they pass from one pane to the next. Tight seals matter too, since sound sneaks through tiny gaps. That's why closing a window makes a room quieter.
What is a soundscape, and how can you listen to one?
A soundscape is all the sounds of a place together, such as birds, wind, footsteps, traffic, and music. Scientists record soundscapes to learn about the health of a place. You can take a sound walk with a grown-up. Walk slowly and listen for different kinds of sounds. If you want to close your eyes to listen better, stop and stand still first, away from the street.
What is smog?
The word smog comes from smoke and fog. Today it mostly means a haze of ozone and tiny particles. Ground-level ozone forms when sunlight reacts with gases from vehicles and factories. Smog is thickest on hot, sunny, still days and can make it harder to breathe. Cleaner cars, better fuels, and rules for factories have helped reduce it in many cities.
Where does city air pollution come from?
The main sources are vehicles, heating buildings, power plants, factories, construction dust, and wood smoke. Some pollution is made of gases, and some is tiny particles, called fine particles, about thirty times thinner than a hair. People breathing them can have a cough or tired lungs. Using fewer vehicles and cleaner energy helps keep air healthy.
How do scientists measure the quality of the air?
Air-monitoring stations pull air through instruments that count tiny particles and measure gases such as ozone. In Canada, the numbers are combined into the Air Quality Health Index, a scale from 1 to 10 or more. Low numbers mean clean air, and high numbers mean people should take it easy outdoors. Checking the index helps you plan your day.
Why can smoke from faraway wildfires reach a city?
Big wildfires send smoke high into the air, where strong winds can carry it for hundreds or even thousands of miles. In 2023, smoke from Canadian fires turned skies orange in New York City. The tiny particles in smoke can bother eyes and lungs. On smoky days, stay inside with windows closed, use air filters if you have them, and check the air quality.
How does a garbage truck squeeze in so much trash?
A garbage truck has a strong hydraulic arm that lifts bins and dumps them into the back. Inside, a big metal plate called a packer blade pushes the trash forward against the wall and squeezes it into a smaller space. Liquid pressure in cylinders gives it great power. Compacting lets the truck carry much more on each trip.
Why do aluminum cans jump off a belt at the recycling plant?
At a recycling plant, items ride along a conveyor belt. Giant magnets lift out steel cans, but aluminum is not magnetic. So the plant uses a fast-spinning magnet at the end of the belt. It creates swirling electric currents inside each aluminum can, and those currents make the can act like a magnet that is pushed away. The cans leap forward into their own bin, while paper and glass fall straight down.
What is a modern landfill like?
A modern landfill is a carefully engineered site, not just a dump. It starts with a thick liner of clay and plastic to keep liquids from soaking into the ground. Trash is spread, squashed, and covered with soil each day. Pipes collect the liquid that drains through the trash and the gas, called methane, which can be burned to make electricity. After closing, many landfills become parks.
Why can't everything go in the blue bin?
Recycling works best when the items are clean and the right type. Greasy pizza boxes, food-covered containers, and plastic bags can spoil other paper or jam machines. Some plastics have no buyers. Cities have rules that list what is accepted, so check your local guide. Rinsing containers and keeping bins free of the wrong things helps recycling work.
How does a city turn green-bin scraps into compost and energy?
Trucks bring green-bin scraps to a processing plant. Workers and machines pull out bags and plastic, and then the scraps go into huge sealed tanks called digesters. With no air inside, tiny microbes break down the food and give off a gas called biogas, which can be used for heat or to fuel trucks. What is left is cured into compost that can enrich soil.
Why does a plastic bottle left outside last for hundreds of years?
Plastic is made from long chains of molecules that bacteria and fungi do not know how to eat. In sunlight and weather, plastic breaks into smaller and smaller pieces, but the pieces don't disappear. They become tiny bits called microplastics. That is why it is best to reuse plastic, recycle it, and never litter. Picking up litter helps keep parks and streams clean.
How do street sweepers clean the road?
A street sweeper has round brushes underneath that spin and sweep dirt toward the middle. A conveyor or vacuum lifts the debris into a storage bin. Sprays of water keep dust from rising. Sweepers keep litter, sand, and leaves out of the storm drains and rivers. They often work at night or early in the morning when there is less traffic.
How do snowplows and salt trucks clear the road?
A snowplow has a big angled blade that pushes snow to the side. Many also spread salt or sand from the back. Crews watch the weather and plan routes with GPS so they can clear major roads first. Small plows clear sidewalks and bike paths. Stay far away from plows, since the drivers might not see you, and never play in the snow piles.
Why is too much road salt a problem?
When snow melts, salty water washes into storm drains, streams, lakes, and soil. Too much salt can harm fish, trees, and drinking water. It can also rust cars and bridges and make a dog’s paws sore. Cities use the right amounts, spray salty water before storms, or mix in sand. Shoveling early helps use less salt. Some places have tried beet juice to help salt work better.
What should happen to old phones and computers?
Old electronics, called e-waste, contain valuable metals like copper and gold, and some materials that should not end up in a landfill. Many places have special drop-off events or stores that collect them for recycling or repair. Never throw batteries in the trash, since they can start fires. Giving working devices to someone who needs them is the best choice.
How can a neighborhood make less trash?
Neighbors can share and repair instead of buying new. Some towns have repair cafés where volunteers fix toys and clothes, and libraries that lend tools. People bring cloth bags, compost food, and swap clothes. The idea is to reduce first, then reuse, then recycle. Less trash means less to carry, bury, or burn.
Why does a school bus flash its lights and swing out a stop sign?
A school bus uses its lights to warn other drivers that children are getting on or off. Yellow or amber lights flash first, which means get ready to stop. When the bus stops, red lights flash and a stop sign swings out from the side. Drivers must stop and stay stopped, and in many places they must stop from both directions. Never walk in front of a bus without the driver seeing you.
What did the very first cities look like?
About 10,000 years ago, people began farming and could grow more food than they needed. Villages grew into towns with houses packed close together. One early town, Çatalhöyük in present-day Turkey, had homes entered from the roof. About 5,000 years ago, Uruk in Mesopotamia had tens of thousands of people, markets, and one of the first kinds of writing, used to keep records.
How did ancient Romans bring water to their cities?
The Romans built aqueducts, which were long channels that carried water from springs and rivers far away. They sloped very gently downhill so gravity could do the work, and tall stone arches carried them across valleys. Some are still standing. Water arrived at public fountains and baths. Engineers needed careful measuring skills to keep the slope just right.
How did elevators and cars change the way cities grew?
Before elevators and steel frames, buildings were rarely taller than about six stories because people had to climb stairs. After elevators, cities grew upward. Later, when cars became common, roads became wider and people could live farther from work, so cities spread outward into suburbs. Subways, buses, and trains helped people travel in crowded places.
Why do some cities have a grid of streets and others wind around?
A grid is easy to plan, easy to map, and easy to divide into building lots, so many cities, like Toronto and Chicago, use it. Winding streets often grew from old paths, hills, rivers, and coastlines in places like old European towns. Grids make it simple to find your way, while curves can slow cars and add charm. Each pattern has good points.
What do city planners do?
City planners think about how a city can grow in a healthy way. They study maps, population numbers, traffic, parks, and land. They help decide where homes, shops, schools, and roads should go, and plan for the next 20 or 30 years. Planners also listen to what many different neighbors need. It is like putting together a giant puzzle.
What is a zoning map?
A zoning map shows what kinds of buildings are allowed in each part of a city, such as homes, shops, offices, factories, or parks. It helps keep noisy or smelly places away from bedrooms and makes sure there is room for everything. Some zones mix homes and shops so people can walk to stores. Planners adjust the map as the city changes.
How do planners decide where a new school or park should go?
Planners count how many families and children live nearby and look at the distances people would need to walk. A common goal is to place parks and schools within a short walk, about ten minutes, for most families. They also check whether the roads are safe and whether there is enough land. They ask neighbors for their ideas too.
What is population density?
Population density tells how many people live in a certain area, such as per square mile or square kilometer. Dense places, like downtown Toronto, have many people in a small area. Toronto has about 4,000 people per square kilometer, while all of Canada averages only about four. Dense neighborhoods can share buses, shops, and pipes more easily.
How do map layers help planners?
Planners use computer mapping, called GIS. Each layer of the map shows one kind of information: roads, pipes, trees, parks, flood zones, or buildings. By stacking layers, planners can see where problems and opportunities lie. For example, they can find areas far from parks or places likely to flood. Maps help them make wise choices.
What is the difference between a city growing up and growing out?
When a city grows outward, it uses more land, so houses, roads, and pipes spread farther apart. This can mean longer trips and more driving. When it grows upward, with taller buildings, more people live close to shops and transit, using less land. Most cities do a mix. Planners try to balance parks, farms, and homes.
Why do cities protect old buildings?
Old buildings tell the story of a city and make it special. Their materials and craftsmanship are often beautiful, and reusing them saves resources. Cities can protect them with heritage rules and find new uses for them. In Toronto, old factory buildings in the Distillery District now hold shops and studios. A city with history feels like a place with memories.
How do cities get ready for heavy storms and floods?
Cities build bigger storm pipes, ponds that store extra water, and pumps to move it away. Underground tanks hold extra water, and some streets are designed to hold water briefly. Weather forecasts give warnings so crews can prepare. Walls or barriers protect low areas. The aim is to give the rain somewhere to go that is not your basement.
What helps a city stay cool during a heat wave?
Shade trees, parks, and light-colored roofs keep cities cooler. Cities open cooling centers in libraries and community centers, set up water fountains, and run splash pads. People can drink water, rest in the shade, and check on neighbors. Warm nights are hard for people, so cooling matters. Planning for heat helps everyone.
What makes a city a good place for kids?
A kid-friendly city has safe sidewalks and crossings, parks and playgrounds, libraries, bike paths, and places to meet friends. Slow traffic near schools, shade, and clean air make playing outdoors easier. Planners sometimes ask children for ideas, because kids notice things grown-ups miss. Walking and playing outside help bodies and minds grow strong.
What is a smart city?
A smart city uses sensors and computers to help things run better. Sensors can count traffic, find water leaks, track free parking spots, or warn of floods. Apps share bus arrival times. The information helps workers fix problems faster and plan better. Cities also need to keep people's personal information private and safe.
How do bike-share systems work?
In a bike-share system, you can borrow a bike from a station, ride it to another station, and lock it back. You usually unlock it with a card or an app. A computer tracks which bikes are where. Workers move bikes from busy stations to empty ones, and check brakes and tires. Always wear a helmet and follow the traffic rules.
How can kids help design their city?
Many cities invite kids to share their ideas. Children build models, draw maps, or make suggestions about parks and streets. A program called Block by Block lets young people design public spaces in the game Minecraft, and planners have used their ideas. Kids know what they need and what is missing. Everyone can help make a better city.
How do planners test a city design before it's built?
Computers can simulate how people and cars would move, how sunlight and shadow would fall, or how a flood would flow through the streets. Planners can change a plan and run the test again at no cost. Small models and virtual reality also help them imagine the place. Testing first means mistakes are found early, when they are easy to fix.
Why do some cities leave a ring of green land around them?
A greenbelt is a ring of protected farms, forests, and wetlands around a city. It stops the city from spreading forever, keeps farmland and nature close to people, and protects rivers and drinking water. It also gives people nearby places to hike or picnic. Ottawa has one, and Ontario protects a huge Greenbelt around the Toronto region. Protected land helps wildlife and cleans the air.
Why do neighborhoods in the same city feel so different?
Each neighborhood grows from its own history, buildings, and people. Streets might be lined with old houses, tall apartments, or shops, and different groups bring their foods, languages, music, and festivals. Hills, rivers, and parks shape each area as well. These differences are what make a big city interesting to explore.
Why do cities have public art?
Murals, statues, mosaics, and light displays make streets friendlier and tell a community's stories. Public art can brighten a plain wall or turn a utility box into a masterpiece. Artists use paints and materials that must stand up to sun, rain, and snow. Art gives people a reason to stop, look, and talk to each other.
How do cities make streets easier for everyone to use?
Good city design helps people with different needs. Curb cuts are sloped sidewalk edges, first made for wheelchairs, that also help strollers, carts, and bikes. Bumpy tiles warn people with low vision about crossings, and talking signals help them cross. Ramps, wide doors, and elevators make buildings open to all. This is called universal design, because it works for everybody.
Why do so many people in cities live in apartments?
In a crowded city, land is limited and expensive. Apartments stack homes on top of each other so that more families can live close to work, schools, and shops. Shared walls and floors keep buildings warmer, because there is less outer wall exposed to the cold. Many people can share the same elevator, heating system, and water pipes.
How will today's kids shape the cities of tomorrow?
The cities of the future will be built, run, and improved by people who are kids today. They will invent cleaner transport, smarter buildings, and new ways to share water and energy. Learning about science, math, and nature helps. Even now, you can notice problems in your city and imagine ways to fix them.
How do all the city systems fit together like one giant machine?
A city works because many systems connect. Buildings need water and power, streets need lights and signs, and trash trucks and sewers keep things clean. Parks and trees support wildlife and cool the air, while planners and workers keep everything going. When one part changes, it affects the others. A city is a living puzzle that people keep solving together.