Hi. Upon doing some research I’ve stumbled on this site. As someone very ignorant about the mechanics of the universe, I wonder if I could ask a very random question here. I am a writer, currently working on the premise of a novel which must adhere to the following brief: the story must be set on an ‘alternative’ Earth, one that, at some point, has gone down a different ‘trouser-leg of time’. Anything can be different, from a small subtle difference in Earth’s history, to a large, very evident one. The scenario I would like to build on is that Earth (being the same in every other aspect) has formed with a large set of extremely deep trenches (a massive fault zone) running in a very broken but also distinguishable line around its entire circumference. Visually, this would look like a line around the entire Earth. The novel is set in the present day. My question is, could there be any combination of factors, or any situation at all that would result in a planet (not necessarily Earth) being very slowly torn in two – either through external forces e.g. two opposing gravitational pulls, or by internal forces splitting the planet in half, gradually, over time. My mind has thrown up a couple of scenarios that are probably very unfeasible: I have read that a constantly fluctuating gravitational pull can cause a planet to distort again and again, creating friction and heat within the planet. Could this rising heat possibly contribute to a gradually expanding Earth, and therefore a growing fault line? Could a planet break into two halves because of this (assuming it has some sort of integral weakness) or would the break-up of Earth be an all-round affair, with it generally exploding over time? (Like WASP-12b). Or if there was a very large planet orbiting in tandem with the Earth, having a gravitational pull the opposite direction of the Sun’s, could this contribute to a slow pulling-apart, which might be most obvious in the equatorial or pole-to-pole trench growing larger? As you can see, I’m flailing around in a dark cupboard. Basically I need a scenario in which the planet is being pulled in two over a long period of time, hopefully a scenario that is at least a tiny bit credible. (The point is that the duality of human nature is reflected in this physical metaphor).