Invisible Time Travellers

It all seems very cosy when the model Time Machine, resting on a small octagonal table in front of the Time Traveller's fireplace - with two legs of the table on the hearthrug - begins its interminable but invisible voyage through time. However, if narrative coherence is to be salvaged, then some rationale other than that offered by the Time Traveller must be found. What can make a material object simultaneously undetectable and time dilated? Whatever the explanation, it can equally apply to Jack Havig and his fellow mutants in Poul Anderson's There Will Be Time. The chronokinetic force that operates in the Time Machine is also present in their brains. However, the Time Traveller's future comprises civilizational advance followed by human devolution whereas Havig's future contains the War of Judgment, the Maurai Federation and, later, the Star Masters - who are an acceptable alternative to the Danellians.