He, or I, returned.
"Do you know my theory of the Ripple Effect?"
Considering the effects of actions as ripples on surface water, eventually they disappear, and thereafter time continues as if that action had never taken place?
"Yes, that's it."
Consequently, providing our actions are minimal, we travellers can be accommodated by time's stream.
And two of us, together, simultaneously?
"Matter cannot exist simultaneously in two places. But our physical makeup, the molecules, our structure, changes over time, therefore given time there's nothing to prevent us both existing here and now."
As this proves.
We smiled. "As this proves."