What to do in a Crap Sack World? Conventional wisdom says that when Earth That Used To Be Better starts going downhill, it's time to hop aboard an ISO Standard Human Spaceship and depart for all points celestial. But in the Time Travellers Paradise scenario, perhaps because it is recognized that not All Planets Are Earth Like, it seems more practical to stick to Earth but explore a different dimension of spacetime.

This is Time Travel not as vacation, but as The Migration, going back in time to start Settling The Frontier on a more resource-rich Earth, and to build a true Arcadia there. Rather than Set Right What Once Went Wrong, the protagonists decide in this case to deliberately become Trapped In The Past to when things *were* right.

To avoid a Temporal Paradox, these stories may be set in the deep past when Everythings Better With Dinosaurs and other giants roamed the Earth, so as not to mess with human history, and/or in an Alternate Universe that approximates the Earth's past. Because of the logistical difficulties of transporting a whole population back, the mechanism is more often a Time Portal than a Time Machine.

Examples:

• Mastodonia (Clifford D. Simak)
• Terra Nova (TV)
• Conquistador (S. M. Stirling)
• Dresden Codak (webcomic)
• All Our Yesterdays (Star Trek)
• The Girl from Tomorrow (TV)
• Hawksbill Station (Robert Silverberg)
• Saga of Pliocene Exile (Julian May)