Total immersion means that the sensory experience feels so real, that we forget it is a virtual-artificial environment and begin to interact with it as we would naturally in the real world. In a virtual reality environment, a completely synthetic world may or may not mimic the properties of a real-world environment. This means that the virtual reality environment may simulate an everyday setting (e.g. walking around the streets of London), or may exceed the bounds of physical reality by creating a world in which the physical laws governing gravity, time and material properties no longer hold (e.g. shooting space aliens on a foreign gravity-less planet).