Imagine some Cosmic Force, natural or supernatural, breaks the Earth from its orbit around the Sun. It travels vertically upward in relation to the Solar System plane, and it is in no danger of colliding with another cosmic body. It continues along this trajectory with no signs of stopping, until it leaves the Solar System and becomes a wandering planet without a sun to shepherd it, an exoplanet, wandering the infinite void between the stars alone.
Could humanity find a way to survive this scenario without the warming light of the Sun?Could some part of humanity survive on the warmth, energy, and light of other fuels, maybe in massive underground warrens? How long till all traditional fossil fuels run out? Could we even manage to survive long enough to acquire them? What if we had a decade of forewarning? A century?
What types of planets or animals would we try to save to sustain ourselves? Could we obtain some sort of extremophile bacteria which derives its energy from sources other than the sun, and modify it in some way to make it edible or useful?
What would the effects be? How extreme would the cold (maybe better to think of it as a lack of any heat) How long till the oceans freeze all the way through? Would the force of the freeze crack the Crust all the way to the Mantle? What other extreme physical effects would happen? Would all weather on the planet end without a sun to cause disparate seasons of warmth and cooling?