Many world-builders who build science-fiction worlds worry about one simple question: How hard is your science-fiction world? Most people are just baffled by this question, but the answer is very simple. The hardness of a science-fiction world is defined by how close it is to reality. This means that the harder the world is, the less liberties it takes with scientific theories and new technologies. Moh’s scale of science-fiction hardness is an excellent tool to see how realistic one’s science is. Without further ado, this is Moh’s scale of science-fiction hardness. Each level is represented by a number and a material to illustrate the concept better. 0 - Diamond: It works because it exists. While this level does not describe a science-fiction world, it is a part of the scale. It describes a world that matches reality as we know it perfectly, and it takes absolutely no liberties. Fiction that takes place on this level is usually called realistic or mainstream fiction. 5 - Ruby: It works because it is based on already existing ideas. The first science-fiction level of the scale, this level is quite close to reality. This level is often characterised by the large amounts of research that goes into it. No known physical laws are broken or altered and nearly every piece of technology behaves as it would in real life. 4 - Steel: It works because it is based on extrapolations. Science fiction that is based on extrapolation of already existing theories or technologies goes here, with the occasional new theory or idea. Faster than light travel is usually a possibility on this level of the scale and some liberties are taken with physical laws. 3 - Gold: It works because it is based on a new idea. On this level of the scale, the author usually comes up with one or more new, internally consistent theory that has some scientific basis. They could also come up with new elements as an explanation for some technologies, but everything works according to certain laws that are consistent. Larger liberties are taken with physical laws, but they are still there and the new ideas are treated as science. 2 - Lead: It works because it sounds like it works. Even more ideas are incorporated into the universe, but they are still internally consistent. The story and the characters encounter technologies and inventions based on these new ideas very frequently. The laws of physics take a backseat and more often than not, the new ideas overshadow them completely. 1 - Water: It just works. Science, physical laws and sometimes even internal consistency are thrown out of the window. Technology just works and the audience is expected to accept it regardless of how ridiculous it sounds. Note that a high level of technology is not necessary for such technologies to exist. Note that the scale does not represent how much explanation is given on the workings of any technology. Even the hardest of science-fiction can have little to no explanation on how its technology works as long as it fits the requirements stated by Moh’s scale.