There are a few observations we can immediately make about ‘Newtonian relativity’. First of all, we emphasize that Newton himself was only concerned with the physics of moving objects (i.e. mechanics), and said nothing about other physical laws, such as electromagnetism. A consistent physical theory of electromagnetism had not been formulated at Newton’s time. Second, it is to be noted that the definition above begs the question somewhat: What does ‘constant speed’ mean, if there is no such thing as absolute motion? Constant speed with respect to what? We will address this somewhat as we go on, and in fact it will play a big role in later posts. For now, we simply say that we ‘instinctively’ can tell the difference between, for instance, driving down the road at a constant speed and slamming on the brakes of the car.