If you are in a spaceship with no windows and are coasting along at 100mph or 1000mph or 298,000,000m/s (not accelerating or braking), you are in an inertial frame of reference. There is no test you can do to tell if the spaceship is actually moving or not. Physic is fascinating. https://video.nostr.build/056f2427f8571ff6ccb282dd0143fed1537edd023801f6d31788406f4b31161e.mp4