[What you refer to as "fearmongering nightmare dreams" is the accurate explanation of the future. Whatever you want to call it, I want an example a child who's been scared by, for example, the statement: "In billions of years, the sun will run out of nuclear fuel and begin to expand into a red giant. It will shed its outer layers until finally collapsing into a white dwarf.]

"They talk of all suns burning out, and everything falling in a black hole, galaxies colliding, in a cosmic roller derby, and death and despair and dark hopelessness at every turn. Any child that has heard, or been taught about heaven wonders how all this fits in with it. How am I supposed to live forever and the sun and moon and stars last forever, and our city last forever, when these guys claim we are all gooing to crash and burn??"