In the world that I'm building, life on Earth has gotten pretty unbearable for some. My first thoughts are over-population, pollution, war, etc. A company/government comes along and tells you and your family that they have the ability to resettle you, not to a new location, but to a fresh "new" Earth. They would do this by sending you back in time to an alternative Earth (no cause and effect relationship to cause paradoxes) where the travel was geographically fixed to a specific time.
The issue that most people would have, in my opinion, is that it is a one-way trip, with zero feedback to indicate if people arrived successfully or what was waiting for them. The company claims they were instructed by a message from a long lost civilization who accomplished something similar, but met an unfortunate fate early on (example: Atlantis).
Kind of reminds me of the television show, Terra Nova, but I'm putting a different kind of twist to the time travel portion.
How bad would things have to be for people to volunteer to be part of this program, given that they have no concrete evidence of their safety?