Gravitation is a force that claims that all objects on Earth and in space are attracted to one another. The gravitational force exerted on an object is proportional to its mass; the greater the mass of an object, the greater the gravitational force exerted on it by other objects. All visible items, such as a pen, eraser, planets, mobile phone, watch, and refrigerator, are attracted to one other in some way. With the Electromagnetic Force and the Nuclear Force, gravity is one of the non-contact forces.
A satellite is an object that orbits the sun, the earth, or any other massive body. When it comes to satellites, there are two basic categories of classification: natural and man-made.
Planets, moons, and comets are examples of natural satellites. There are 67 natural satellites orbiting Jupiter. The moon, the earth’s only permanent natural satellite, is responsible for the sea’s tides. Other objects (such as asteroids) can occasionally reach the earth’s orbit and serve as natural satellites for a period of time.
Earth satellite, sometimes known as artificial satellite, is a man-made object that has been sent into a temporary or permanent orbit around the Earth. This sort of spacecraft can be crewed or uncrewed, with the latter being the more prevalent.
Sir Isaac Newton proposed the idea of an artificial satellite in orbital flight in his work Philosophiae Naturalis Principia Mathematica (1687). He pointed out that a cannonball fired at a high enough velocity from a mountaintop in a direction parallel to the horizon would travel the whole circumference of the Earth before dropping. Although gravitational force would lead the object to fall toward the Earth’s surface, its momentum would compel it to descend in a curved route. Greater velocity would propel it into a stable orbit similar to that of the Moon, or it would steer it away from Earth entirely.
The International Space Station (ISS) was launched into orbit in 1998 and is the world’s largest space station. It is a habitable artificial satellite that can occasionally be seen in the night sky if the sky is clear. Among its many functions are those of a laboratory, an observatory, and a landing base for potential expeditions.
A moon is only defined as an earth’s natural satellite by the International Astronomical Union (IAU), which determines the definition of astronomical terminology such as planet, star, and so on. That isn’t to say that every natural satellite is a moon. (In fact, according to one definition of a planet, our Moon is also a planet.)
The Soviet Union launched Sputnik 1, the first Earth satellite, on October 4, 1957, nearly three centuries after Newton developed his idea. Every 96 minutes, Sputnik circled the Earth, and its simple radio signal was picked up by scientists and radio operators all across the world. Three months later, the United States launched Explorer 1, its first satellite into orbit (January 31, 1958). Explorer was equipped to detect radiation and detected the innermost of the two Van Allen radiation belts, a zone of electrically charged solar particles that surrounds Earth, although being much smaller than Sputnik.
More than 5,000 Earth satellites have been orbited by more than 70 different nations since these initial efforts. More than 2,000 satellites are in orbit as of 2017, the majority of which are from Russia or the United States. The satellites range in size and design from minuscule “picosatellites” weighing less than a kilogramme to the International Space Station, a space laboratory with a mass of more than 400 tonnes that houses six humans. They serve a wide range of purposes. Scientific satellites are primarily used to collect data on the Earth’s surface and atmosphere, as well as to conduct astronomical studies.
Weather satellites send images of cloud patterns and measurements of other meteorological conditions to aid in weather forecasting, while communications satellites relay phone calls, radio and television programmes, and data transfers between remote regions of the globe. Crews of oceangoing vessels and aeroplanes can use navigation satellites to identify their craft’s location in all types of weather. Some satellites are specifically designed for military purposes, such as reconnaissance and surveillance.
Communications satellites, on the other hand, are typically put in an equatorial orbit, allowing them to circle the world’s most heavily inhabited areas from west to east. Furthermore, the communications satellites that make up a network or system are almost always launched at a distance of 22,300 miles (35,890 kilometres) above Earth.
Satellites can be launched into a variety of orbits. The function of the spacecraft plays a big role in deciding which course to take. For example, most weather and reconnaissance satellites are launched into a polar orbit, in which the Earth’s polar axis is a line on the orbital plane. Because polar-orbiting satellites spin with the Earth, they pass over its whole surface in a short amount of time, providing complete worldwide coverage.
In the most common sense, a natural satellite is an astronomical body that circles a planet, dwarf planet, or tiny solar system body (or sometimes another natural satellite). Natural satellites are commonly referred to as moons, a term derived from Earth’s Moon. There are six planetary satellite systems in the Solar System, totaling 207 known natural satellites.
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