One way to test them would be to have them transit the Atlantic in a smallish sailboat. I've been told by folks who've done it that its really a stressor and you shouldn't ever do it with people you are not absolutely sure of.

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"The beauty of that discussion of averages is that you don't have to be an expert in Apollo or in photography in order to see where this time study "analysis" breaks down. You just have to be, well...not an idiot." -JayUtah