The density of the aluminium was calculated by a human and this is not natural but can be due to errors in the calibration of the scale for measuring the weight or taking readings from the measuring cylinder.
Random errors are natural errors. Random errors in experimental measurements are caused by unknown and unpredictable changes in the experiment. Systematic errors are due to imprecision or problems with instruments.
Francisco Redi must use 1)a covered, unrefrigerated meat and 2) an uncovered, refrigerated meat to experiment and test his hypothesis that maggots came from flies rather than from meat.
