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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Yes that is basically what an orbit is the sideways motion of the Earth means as it falls towards the Sun it keeps on missing.
Yes, it is, and all other planets too. And the Sun is in a free fall relative to the rest of the galaxy.
Actually we find ourselves roughly 1,5cm farther away from the sun each year. So instead of falling towards the sun we actually drift away.
The reason for this is that the sun loses mass. And this slight loss of mass results in a loss of gravitational pull. And thus we drift away.
https://www.forbes.com/sites/startswithabang/2019/01/03/earth-is-drifting-away-from-the-sun-and-so-are-all-the-planets/?sh=4b75f2e6f7d3
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.
Drop a baseball from your hand and it’s in free fall. Now drop it again but this time give it a little push away from you. The ball is now in free fall but it now moved a bit away from you. Repeat this again but now push it harder away from you. The ball will still be in free fall but it will be even farther away from you when it hits the floor.
Now, if the earth was perfectly flat the ball will always hit the floor no matter how hard you trow it away from you (i.e. the vertical movement is independent from the horizontal). But earth is not flat so the floor ‘curves down’ so as you throw it harder away from you it will take a bit longer to reach the ground each time.
There will eventually be a push strong enough that the ball will always be falling since it matches exactly the curvature of the earth. In other words, the ball will be forever in ‘free fall’. You may also know this as ‘orbiting’.
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