"And yet it's just as plausible that the moon landings, like this circumnavigation of Africa, could have simply been a momentary flex of a civilisation at the height of its powers, not to be repeated for thousands of years."
These seem predictably rare events to me. There are very fiew individuals that afford to engage in such endeavors and the odds of succeeding are acting both as deterrent and physical limiting factor to any attempt. The fact that happened is an exception. Not until the odds improve and a strong enough incentive changes things. The incentive for Moon landing has been political. Once achieved, it dissipated, and there isn't much sense for it to be repeated until a new motivating factor will appear.
Addition: Diolkos, considering the cost and efficiency of how it could have been operated and maintained back in the antiquity, was clearly an artifact that could work only for short distances, where the gains were significant enough to justify it, and there was little sense for it to be constructed on the scale that rails were later constructed.
These seem predictably rare events to me. There are very fiew individuals that afford to engage in such endeavors and the odds of succeeding are acting both as deterrent and physical limiting factor to any attempt. The fact that happened is an exception. Not until the odds improve and a strong enough incentive changes things. The incentive for Moon landing has been political. Once achieved, it dissipated, and there isn't much sense for it to be repeated until a new motivating factor will appear.
Addition: Diolkos, considering the cost and efficiency of how it could have been operated and maintained back in the antiquity, was clearly an artifact that could work only for short distances, where the gains were significant enough to justify it, and there was little sense for it to be constructed on the scale that rails were later constructed.