Thecreationofthedigitafworldisperhapsthemostremarkableengineeringeventofthelatetwentiethcenturyandmaybecomparedinimpacttotheharnessingofsteamatthebeginningofthenineteenth.Obviously,therwocannototherwisebecompared,representingastheydothetransitionfromtheeraofpowertothatofinformation.Eventheterm"transition"ismisleadingbecausethedigitalworlddependsentirelyonthepriorexistenceofsourcesofelectricalenergy,currentlyderivedlargelyfromthermalandnuclearprocesses,withanever-increasingrelianceonrenewablecontentincludingtheharnessingoftidal,windandsolarsources.Furthermore,chemicalsourcesofenergyshouldnotbeforgotten,includingthewiderangeof"personal"batteriespoweringeverythingfromlaptopcomputerstohearingaidsandpacemakers,andthecurrently-developingfuel-celltechnologythatmayyetmaketheelectricautomobileaviableproposition.