⦁ If that same astronaut did not have a tether to stop them from moving, what would happen? For how long?
If an astronaut in space does not have a tether to stop them from moving, they would continue to move in a straight line with the same velocity and direction they had before. This is due to the absence of any external force acting on them to change their motion.
According to Newton's first law of motion, an object in motion will stay in motion with the same velocity and direction unless acted upon by an external force. In the vacuum of space, there is no air resistance or friction to slow down or stop the astronaut's motion.
Without a tether, the astronaut's velocity and direction would remain constant until acted upon by another force. If they are far away from any significant gravitational fields or other objects, they would likely continue to move in their straight line trajectory indefinitely or until another force, such as gravity from a nearby planet or moon, or the thrust from a spacecraft, acts upon them.
Therefore, the astronaut's motion would be perpetual, moving at a constant velocity and direction until influenced by external forces or until they are able to exert their own propulsion to change their course.