Pardon me if this seems like an incredibly naive question. Perhaps the question could also be rephrased as such: "Why do the laws of classical mechanics hold true with earth as a frame of reference?" A quick google search turned up the usual answer: the earth rotates at a constant speed. Regardless of what speed the earth is rotating at doesn't the fact that it is rotating/changing velocity mean that objects on the surface of the earth are constantly accelerating? If so then why don't we feel the earth's rotation and why is Newton's second law valid? Isn't it no longer an inertial frame of reference if the earth is accelerating.