Johannes Kepler was a German mathematician and astronomer who formulated three laws of planetary motion in the early 17th century. These laws describe the motion of planets around the Sun and are based on observations made by Tycho Brahe.
1- The first law, also known as the law of elliptical orbits, states that the orbit of a planet around the Sun is an ellipse, with the Sun at one of the two foci. This means that the distance between the planet and the Sun varies as the planet moves in its orbit.
2- The second law, also known as the law of equal areas, states that the line connecting the planet to the Sun sweeps out equal areas in equal amounts of time. This means that the planet moves faster when it is closer to the Sun and slower when it is farther away.
3- The third law, also known as the law of harmonic motion, states that the square of the period of a planet's orbit is proportional to the cube of its average distance from the Sun. This means that the farther a planet is from the Sun, the longer it takes to complete one orbit.
A satellite is an object that orbits around a planet or other celestial body. The motion of a satellite is determined by the gravitational force of the planet or body it is orbiting. The satellite is constantly falling towards the planet due to gravity, but it is also moving horizontally, which keeps it from crashing into the surface. This combination of falling and horizontal motion is what creates the orbit.
Weightlessness, also known as zero gravity, is the state of being weightless or having very little weight. It is experienced by objects in orbit around a celestial body, such as a planet or moon. In this environment, objects do not experience the normal force of gravity that they would on the surface of the body. This can create the sensation of weightlessness for objects and humans inside a spacecraft or on a space station. Weightlessness can also occur in other situations, such as during freefall or in an aircraft following a parabolic trajectory.