Knots, Mixed martial arts, Satellites, Soil, LPG, Mining. Find out about the inner workings and origins of the things that pique your curiosity. Knots: A knot is a way of interlacing, entwining, or looping a linear material such as a rope, cord, or string, and drawn tight into a knob to fasten or bind it with another material. Mixed Martial Arts: Mixed martial arts or MMA is a full-contact combat sport that uses techniques from other combat sports and martial arts Satellites: A satellite is an artificial object that is placed into the orbit of the earth for various purposes. Memory: Memory is a person's ability to encode, store, and retain information and past experiences in the brain. Soil: It is the brown dirt that makes up most of the ground. Soil is a natural body which is a mixture of minerals, organic matter, gases, liquids, and organisms. LPG: Liquefied petroleum gas or LPG is flammable mixtures of hydrocarbon gases, which are also referred to as propane or butane. Mining: Mining is the process of extracting valuable minerals from deposits on earth, which are of economic interest to the miner.