Kirchhoff's law of thermal radiation rarefied material such as air, or transparent material, through which observations can be made. The interface is not a material body and can neither emit nor absorb. It is a mathematical surface belonging jointly to the two media that touch it. It is the site of refraction of radiation that penetrates it and of reflection of radiation that does not. As such it obeys the Helmholtz reciprocity principle. The opaque body is considered to have a material interior that absorbs all and scatters or transmits none of the radiation that reaches it through refraction at the interface. In this sense
A Sound of Thunder changes in the future is a representation of the butterfly effect, and used as an example of how to consider chaos theory and the physics of time travel. A Sound of Thunder "A Sound of Thunder" is a science fiction short story by Ray Bradbury, first published in "Collier's" magazine in the June 28, 1952, issue and Bradbury's collection "The Golden Apples of the Sun" in 1953. In the year 2055, time travel has become a practical reality, and the company Time Safari Inc. offers wealthy adventurers the chance to travel back in time to hunt extinct species such as