Sugar soap Sugar soap Sugar soap, as typically found in Commonwealth countries, is a cleaning material of variable composition sold for use on surfaces affected by greasy or tarry deposits which are not easily removed with routine domestic cleaning materials. Its name arises from the fact that, when in dry powder form, it resembles table sugar. The solution is alkaline and its uses include cleaning paintwork in preparation for repainting. The precise ingredients and their proportions (and consequentially what hazards, if any, are associated) vary between manufacturers and suppliers but are now generally found listed in the Material Safety Data Sheets found
Proper time arc length of world lines in four-dimensional spacetime. From the mathematical point of view, coordinate time is assumed to be predefined and we require an expression for proper time as a function of coordinate time. From the experimental point of view, proper time is what is measured experimentally and then coordinate time is calculated from the proper time of some inertial clocks. Proper time can only be defined for timelike paths through spacetime which allow for the construction of an accompanying set of physical rulers and clocks. The same formalism for spacelike paths leads to a measurement of proper distance