Orbits: travelling around — Astronomy, 4–6
An orbit is the repeated path one space object takes around another. Astronomy, 4–6 years.
A path around
An orbit is a journey around another object in space. The object does not simply fly away; it keeps following a curved path, again and again. Earth follows an orbit around the Sun, and the Moon follows an orbit around Earth.
Why do things stay in orbit?
Space objects are pulled by gravity, but they are also moving forwards. Gravity bends their path towards the bigger object, while their movement keeps them from falling straight in. People use the idea of an orbit to predict where a planet or spacecraft will be later.
Earth’s trip around the Sun
Imagine one bead for Earth and a large ball for the Sun. Put the bead on a curved track around the ball, then move it until it reaches its starting place again. Earth takes about 365 days to complete one orbit, which is why we count about 365 days in a year.
It is not a fixed track
A model often shows an orbit as a painted line, so it can seem that an invisible rail holds the planet there. That is a reasonable mistake because a line makes the path easy to see. In space there is no rail; gravity and movement together keep the object on its repeated path.
Predicting space journeys
Engineers use orbits when they send a spacecraft towards another world. They choose its speed and direction so gravity can bend its path in the right way. The same idea helps keep communication and weather satellites travelling around Earth instead of drifting away.
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