Temat 2: MOTION

Experimentss how that the properties of Galilean time and space are xtracted from the environment both by children and animals. This xtraction has been confirmed for cats, dogs, rats, mice, ants and fish, among others. They all find the same results. First of all, motion is change of position with time. This description is illustrated by rapidly flipping the lower left corners of this book, starting at page 224. Each page simulates an instant of time, and the only change that takes place during motion is in the position of the object, say a stone, represented by the dark spot. The other variations from one picture to the next, which are due to the imperfections of printing techniques, can be taken to simulate the inevitable measurement errors. Stating that ‘motion’ is the change of position with time is neither an explanation nor a definition, since both the concepts of time and position are deduced frommotion itself. It is only a description of motion. Still, the statement is useful, because it allows for high precision, as we will find out by exploring gravitation and electrodynamics. After all, precision is our guiding principle during this promenade.Therefore the detailed description of changes in position has a special name: it is called kinematics. The idea of change of positions implies that the object can be followed during its motion. This is not obvious; in the section on quantum theory we will find examples where this is impossible. But in everyday life, objects can always be tracked.The set of all positions taken by an object over time forms its path or trajectory.The origin of this concept is evident when one watches fireworks or again the flip film in the lower left corners (starting at page 224). In everyday life, animals and humans agree on the Euclidean properties of velocity, space and time. In particular, this implies that a trajectory can be described by specifying three numbers, three coordinates (x, y, z) – one for each dimension – as continuous functions of time t. This is usually written as x = x(t) = (x(t), y(t), z(t))