only if physicalobject 3 is observed to have acceleration x. Thereis a 1-1 correspondence of the acceleration magnitude of a system in relationto the distant stars with inertial forces experienced in it. Assuming thedistant stars have nothing to do with the behaviour of local physical systems, (3.a)seems meaningful even without a referential. To make it compatible with (1.a)and (1.b) define invisible absolute space to be the physical object to be the referentialto which all movement should be referred. Since the definition of movementtaken on (1) requires observation, there should be a way to see absolutespace in an indirect way. Now (2.a) can also make sense if movement refers toabsolute space, but empirical experience says it does not (galilean/lorentzianinvariance). Remark: this procedure of defining absolute space is naturalbecause the earth was taken to be the ultimate referential for centuries, sostatement like that of (2.a) were very frequently said without major concerns.Once the earth was found to be moving, absolute space came to save the day. Thatcould be a historical mistake, however. Relational solution: Deny the invisible absolute space since itcannot be observed directly (positivist reasoning). And since the referentialused to measure the so called absolute acceleration was that of the distantstars, create a physical theory that generates inertial forces from therelative motion between the physical object and the distant stars (or moreprecisely, the bulk of matter of the universe). This is a piece of Mach's idea.From these ideas, one can constructa whole new physics that takes this relational solution. Then there should be amechanism for the generation of inertia from the bulk of matter of theuniverse. Also, all that matters are shapes, since they are all directlyobservable information that remains. The relational solution concerning timegoes in a similar fashion. 4) (4.a)= ''n seconds have passed''(4.b): (4.a) is a truesentence if and only if n seconds are observed to have passed Now,once again, we need to define what empirical experience corresponds to''observing n seconds have passed''. Assuming we can map successive shapes ofthe universe to the real numbers (parameterize curves in shape space), we mustfind such a parameter that can be measured from observable data in shape spaceand which can make motions seem correlated by some specific law, so that ''nseconds have passed'' can have any useful meaning. Let's call this theclock parameterization. We can then state that ''n seconds have passed'' means''the clock parameterization is observed to indicate n''. The relational conception of motion becomesextremely compelling once we take as criteria of meaning of statement aboutmotion and time the observation of the behaviour of physical objects. Forexample, take a look again at the construction of meaning of the statementsabove:(1.a) is a true sentence if and only if and only if physical object 1 is observed to have velocity x with respect to physical object 2.(4.a) is a true sentence if and only if n seconds are observed to have passed Wecan see that once we take observation as a fundamental ingredient of themeaning of statements about the physical world, the relational approach seemsto express all its power and purpose. The constraint of meaning