I learnt that ISS is always in a free fall due to Earths gravity. Since ISS orbits the Earth, does this mean Earth is in a free fall due to the sun because Earth orbits the Sun?
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Free fall is a concept dependent on gravity – the earth is moving in one direction and won’t be stopped because it’s in space (since it has inertia) and once it fell within the gravitational range of the sun, it started to be pulled in towards the sun. This combination of moving forward while also being pulled inwards towards an object results in a circular movement we term an orbit. Since it’s stabilised in that position, it’s essentially a stable orbit. Just like the moon is a chunk of rock moving through the sky, but happens to be within the area of sky earth’s gravity has an influence on, so is being pulled in as it moves across, and ends up in a circular orbit.
The idea of ‘free fall’ relies on a concept of up and down that doesn’t exist on that sort of scale. It’s just whether things are near large enough objects that they get pulled into the gravitational field.
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