A satellite, often called an artificial satellite, is a machine put in orbit around the Earth. They are used in many different areas, including communication, broadcasting, espionage, and meteorology.
A satellite is technically defined as any object that orbits a planet. This can include natural satellites, but normally refers to artificial satellites. Natural satellites are rocky bodies that orbit planets or minor planets. An artificial satellite is something made by humans and launched into orbit. The first person to think mathematically about the possibility of putting an artificial object into orbit was Isaac Newton. He wrote about his ideas in his work A Treatise of the System of the World. He proposed a thought experiment known as Newton’s Cannon. Newton imagined firing a cannon from the top of a mountain so tall that the cannonball would never hit the ground and would continually fall around the Earth.
The first artificial satellite was launched in 1957 by the Soviet Union. The satellite was called Sputnik 1. Sputnik consisted of a polished metal sphere with four radio antennas. The satellite sent out radio pulses that were easily detected on Earth. Sputnik 2 was launched a month later and contained the first living passenger. Laika was a stray dog found on the streets of Moscow and became the first animal to orbit the Earth. She died in space and she is remembered by a statue which was erected outside the Russian cosmonaut training facility. Now there are thousands of satellites orbiting the Earth, some are put there by governmental bodies, others are owned by private companies.
Satellites are now essential for a range of different functions in the modern world. The shape and size of the satellite depend on the purpose of the satellite. The largest artificial satellite is the International Space Station (ISS). The ISS is now home to astronauts who are carrying out a range of experiments in microgravity.
Satellites have revolutionized many areas of science and engineering. Astronomical satellites, like the Hubble Space Telescope, are used for observing the universe and taking data in space. There are also satellites which take measurements and observe Earth. These have been particularly useful for environmental monitoring and weather forecasting. Satellites are also crucial for modern day communication systems including mobile phones and the internet. Some satellites are used to determine the location of objects on the Earth’s surface. These satellite systems can be used for navigational systems on ships and planes, but are also used on smartphones.
There have been also missions involving satellites orbiting other planets. These have been fundamental in increasing our knowledge and understanding of other planets in our solar system. These satellites carry out similar work to some Earth-orbiting satellites by imaging the surface and analyzing the atmosphere.