Emrén, A. T. (2012), Towards Practical Definitions of Life,
At first sight, a system is living if it has the ability to reproduce itself. Such simple definitions can easily be shown to fail. Thus, in certain environments, even molecules as simple as Iodine can copy themselves. One could also state that a mule is living, but cannot reproduce. One could also imagine an intelligent organism that does not need to reproduce, because its life has no limit.
Here we will first identify something that certainly is dead, and something that certainly is living. The thermodynamical state "heat death", definitely represents true death. This is a state in which entropy is as high as possible.
On the other hand, a system like a human, that is is able to reproduce, is conscious and has a free will, definitely is living. Somewhere between those extremes, there is a fuzzy boarder. Its position depends upon the purpose for which it is drawn.
Examples of purposes requiring definitions, are the search for properties of the universe required for life to be possible, or in a hospital decide in a hospital if a patient is living or dead.
Börjesson, K. S., and Emrén, A. T. (1997), PASSIPHIC: A Program for Solubility Calculations Involving Pure Minerals and Solid Solutions. Computers & Geosciences acceptedBörjesson, K. S., Emrén, A. T., and Albinsson, Y. (1997), A thermodynamic model for the long term stability of cement. Submitted Börjesson, K. S., Emrén, A. T., and Ekberg, C. (1997), A thermodynamic model for the calcium silicate hydrate gel, modelled as a non-ideal binary solid solution.. Cement and Concrete Research 27, 1649-1657 Emrén, A. T., (1997) Chemical Modelling Studies on the Impact of Small Scale Mineralogical Changes on Radionuclide Migration. . In Geotrap 1997 (NEA Geotrap(97) Ekberg, C., Emrén, A. T. and Samuelsson, A., (1997) The Effect of Mineral Variability on the Solubility of some Actinides. In Mat. Res. Soc. Symp. Proc. (ed 465, 735 Ekberg, C., and Emrén, A. T., (1998) Conceptual uncertainties in solubility calculations in groundwater systems: A calculation exercise.. In Samo 98 Emrén, A. T. (1998), CRACKER a Program Coupling Inhomogeneous Chemistry and Transport. Computers & Geosciences, accepted Emrén, A. T. (1998) Modelling of groundwater chemistry at Äspö Hard Rock Laboratory (SITE-94). SKI Report 96:32, under preparation Emrén, A.T. (1998), Modelling ground waters from Äspö, Sweden, with the CRACKER program. Applied Geochemistry