Regarding the 'difference' between 'mental' and 'physical' time travel, I would like to quote from the Swetasvatara Upanishad (from THE UPANISHADS: BREATH OF THE ETERNAL, translated by Swami Prabhavananda and Frederick Manchester): "Time, space, law, chance, matter, primal energy, intelligence--none of these, nor a combination of these, can be the final cause of the universe, for they are also effects, and exist to serve the soul...The seers, absorbed in contemplation, saw within themselves the ultimate reality, the self-luminous being, the one God, who dwells as the self-conscious poser in all creatures. He is One without a second. Deep within all beings he dwells, hidden from sight by the coverings of the gunas--sattwa, rajas, and tamas. He presides over all time, space, and all apparent causes...Mind and matter, master and servant--both have existed from beginningless time. The Maya which unites them has also existed from beginningless time. When all three--mind, matter, and Maya--are known as one with Brahman, then is it realized that the Self is infinite and has no part in action. Then it is revealed that the Self is all." This, at least to me, shows that Consciousness and Reality are One, so any change in an effect (say space-time) is a change in Consciousness, and appropriate changes in Consciousness produces changes in space-time. Thus it would seem that any alleged difference between 'physical' and 'mental' time travel is itself an illusion....AUM.