Flight

Things can move through the air.

This is called flight. Many living things fly. Birds, bats, and bugs use wings to move.

Some animals just glide. They do not use power to climb.

Some things float in the air.

Balloons and airships use a special force. This force helps them stay up. They do not need to move to fly.

Machines can fly too.

Airplanes use wings to lift up. Some machines use engines for power. Rockets can even fly into space.

Flying can be very fast. Some planes go faster than sound. This makes a loud boom. It can be a big surprise!

Flight is a busy world. It is fun to watch things soar.

Flight is moving through the air or space.

Many living things use flight to move. Birds, bats, and insects are the only animals with powered flight. This means they use power to climb.

Other animals just glide. Gliding is when they move without using power to go up. Some fish can even glide for 45 seconds!

Some things fly by floating. We call this buoyant flight. An airship or a balloon uses buoyancy to stay up. This works because the craft is lighter than the air around it.

Machines can fly too. An airplane uses an airfoil to fly. An airfoil is a special wing shape. It creates lift as air flows across it. Most planes also need thrust to move forward. Thrust is the power that pushes the craft through the air. Rockets use thrust to reach space. Spaceflight is a special kind of flight through the vacuum of space.

Flight is the motion of an object through the air or the vacuum of space. It is a way to move without touching any ground or planetary surface.

There are many different ways to achieve this motion. Some things fly by using buoyancy, which is a force that helps them float. Others use aerodynamic lift, which happens when they move through the air. Some objects move through ballistic flight, which relies on momentum and gravity.

Understanding flight helps us learn how birds move and how humans build rockets.

To understand how things fly, we can look at how different forces work. An aerostat, like a balloon, uses buoyancy to stay up. This happens because the craft has a lower density than the air around it.

Most other things, called aerodynes, must create lift to overcome their weight. An airplane uses an airfoil, which is a specially shaped wing, to create this lift. As air flows across the wing, it creates a force that pushes the plane up.

To move forward, the plane needs propulsive thrust. This thrust can come from spinning propellers or jet engines.

Living things have found many clever ways to fly throughout history. Insects were the first group of animals to evolve flight.

Later, birds, bats, and even some dinosaurs learned to fly. Bats are the only mammals that can stay in level flight. Many other animals, like flying squirrels, only use gliding. Gliding is when an animal moves through the air without using power to climb.

Some fish can even glide for 45 seconds to escape predators.

Humans have studied flight for a long time to build better machines. George Cayley studied flight scientifically during the first half of the 1800s. Later, Otto Lilienthal made over 200 gliding flights to understand how wings work.

The Wright brothers then used this knowledge to make the first controlled, powered flights. In the 20th century, scientists like Robert H. Goddard helped make spaceflight possible.

Yuri Gagarin became the first person to fly in an orbital spacecraft in 1961.

Today, flight connects us to the sky and the stars. We use airplanes to travel across the world quickly. Some planes fly at supersonic speeds, which is faster than the speed of sound.

This speed can even create a loud sonic boom on the ground. We also use rockets to reach space for science and communication.

Spaceflight allows us to use satellites to talk to people far away. From a tiny insect to a huge rocket, flight is an amazing part of our world.

Flight is the motion of an object through an atmosphere or the vacuum of space. This movement occurs without any contact with a planetary surface. It is a fundamental concept in both biology and engineering. Scientists study flight to understand how animals move and how machines travel. This field is divided into several specialized areas of study. Aeronautics focuses on vehicles traveling through the atmosphere. Astronautics is the study of vehicles traveling through space. Ballistics is the study of how projectiles fly.

To understand how things stay in the air, we must look at the forces involved. For an aerostat, the primary force is buoyancy. An aerostat is a system that stays aloft using buoyancy to match the density of the surrounding air. These include free balloons, airships, and moored balloons. The main part of an aerostat is the envelope. This is a lightweight skin that holds a lifting gas. Because the gas is lighter than the air, the craft floats without needing lateral movement.

Most other flying objects are called aerodynes. An aerodyne is heavier than the air it displaces. To stay up, an aerodyne must generate aerodynamic lift. This requires lateral movement through the air mass. Lift is the component of aerodynamic force that acts perpendicular to the flow of air. To move forward, an aerodyne needs propulsive thrust. This thrust overcomes drag, which is the resistance caused by air friction. For steady flight, thrust, lift, drag, and weight must all be balanced.

Aerodynamic flight can be unpowered or powered. Gliding is a form of unpowered flight where an object moves without generating its own thrust. Some animals, like the flying squirrel, use gliding to move between trees. Other animals, like raptors or man-made sailplanes, use soaring to climb by exploiting rising air. Powered flight requires a constant source of propulsion to climb and maintain speed. Most birds and all modern aircraft rely on powered flight to function effectively.

In the natural world, flight has evolved in many different ways. Insects were the first group of animals to evolve flight. Their wings may have evolved from structures that once served as gills. Among vertebrates, birds, bats, and extinct pterosaurs all developed flight. Bats are unique as the only mammals capable of sustained level flight. Many other animals use specialized body parts to glide instead. Flying fish use enlarged fins to glide for as long as 45 seconds.

Human history is filled with attempts to master the sky. Early cultures used stones, spears, boomerangs, and kites. In the 19th century, George Cayley began studying flight scientifically. Otto Lilienthal later performed over 200 gliding flights to gain scientific understanding. The Wright brothers built upon this work to achieve the first controlled, manned, powered flights. The 20th century brought the era of spaceflight. Researchers like Konstantin Tsiolkovsky and Robert H. Goddard provided the necessary breakthroughs. Yuri Gagarin became the first person to complete an orbital spaceflight in 1961.

Modern technology allows for extreme speeds and distances. Supersonic flight occurs when a vehicle travels faster than the speed of sound. This process creates shock waves that result in a loud sonic boom. Hypersonic flight is even faster and involves very high speeds. At these speeds, the heat from air compression causes chemical changes in the air. This type of flight is common during the reentry of spacecraft. Spaceflight uses rockets to provide the thrust needed to overcome Earth's gravity.