Final answer:
If a baseball is thrown out in space, it would continue moving indefinitely at a constant speed in the same direction because there is no air resistance to slow it down. This perpetual motion is due to the lack of friction in the vacuum of space, which is different from conditions on Earth where gravity and friction quickly stop moving objects.
Step-by-step explanation:
If you threw a baseball out in space, the idea of it stopping doesn't apply in the same way it does on Earth due to the absence of atmospheric friction which slows objects down here. In space, particularly the space between the stars known as interstellar space where matter is exceedingly sparse, an object will continue to move indefinitely unless acted upon by another force. This is due to one of Newton's laws of motion, which states that an object in motion will stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force.
So, in the vacuum of space, assuming no other forces like gravity from nearby celestial bodies or resistance from interstellar gas, the baseball would keep moving perpetually at constant speed in the direction you threw it. This concept is very different from what we experience on Earth where friction and gravity quickly stop a thrown ball.
Astronauts on the International Space Station (ISS) experience a microgravity environment where objects, once given a push, move in straight lines at constant speeds because of free fall. This is analogous to our scenario with a baseball in space, except that on the ISS, the space station and everything inside it are in free fall together, circling the Earth.