When travelling in a car at a constant speed, we do not feel the car’s forward motion as our bodies are travelling at exactly the same speed as the vehicle. We become aware of the vehicle’s movement if it accelerates or decelerates, because our bodies are suddenly travelling at a different speed to our surroundings.
Although our galaxy is travelling at 190 miles (300 kilometres) per second, so are we. As the galaxy’s speed is not accelerating or decelerating by any noticeable amount, we are not aware of the motion.
Nathaniel Marten, Science Museum