How feasible is such a planet? Can the planet still be dense enough to be rocky and not gaseous?
I mean 2x the geometric surface area (whether it's land or ocean). i.e. The radius is some multiple of Earth's such that the surface area is double of Earth's. But the surface gravity is roughly 1g.Or did you mean a same mass planet with much bigger continents? Other than increasing very arid land area and decreasing open water area, it would "work". Assuming everything else is Earthlike - whatever that is.
How deep would the ocean be compared to real-life Earth? And is it downright impossible to have continents, or just very unlikely? What about a few islands or one small continent?Surface gravity is proportional to mass/radius2, surface area is proportional to radius2. Double the surface are and you need mass to increase by a factor 4, but the volume increases by a factor 8. That means half the density. Difficult to do with rock. An ocean world would work. A rocky core, then a thick layer of (high pressure) ice and a global ocean. Not very Earth-like, however.
~200 km before you reach the ice, even more before you reach rock, islands or continents don't work. If some intelligence is involved then you can make floating islands of arbitrary size.How deep would the ocean be compared to real-life Earth? And is it downright impossible to have continents, or just very unlikely? What about a few islands or one small continent?
I'm not sure if that would work naturally, but artificially: Sure.Couldn't a solar system form in a low iron space? Silicon and carbon are the main ingredients of many an asteroid. Form the planets without heavy metals and the mass of a larger planet could equal half the density of the smaller planets with iron cores.
As an example, take Silverberg's Majipoor. It's much larger than Earth, and its density is lower, and it's crust is metal-poor. And that's all the geology we get.I always come back to the main response that it's sci-fi and most readers won't know about the mechanics of mass vs. surface area vs. gravity, they'll just take it as written.
From what I'm looking up, that thing has 10x the radius of Earth. My planet would be like, what, 1.4 Earth radius or something?As an example, take Silverberg's Majipoor. It's much larger than Earth
This has been something I'm thinking about. The planet in my story is a planet colonized by human civilization, but it was a planet that was inhabited by another far more advanced alien civilization that has since abandoned the planet. I've been thinking that the planet it self is either highly modified, or nearly entirely artificial, and it's properties would indeed be bewildering for the human civilization that has took it over.Competing pet theories could be forwarded, argued over, etc. . . a case where mystery and doubt could actually add to the novel's believability, in fact. Not having all the answers has always been part of the human condition, after all. That being so, there's no reason why the future - even an advanced spacefaring one - should be exempt from this shortfall. Whatever else the future holds, you can be darn sure puzzlement will have a place in it.
How would the apparatus generating the magnetic field be situated? Would it be a structure inside the core, throughout the surface, or something in orbit of the planet? Or all the above?Artificial planet-scale magnetic fields are no problem in science fiction as long as something (can be robots) takes care of maintenance.