clear advantage over the bulky, exorbitantly expensive space missions of the past, which have been a bottleneck to space exploration. ... It will not need huge quantities of rocket fuel; it will be bred and programmed to 'eat' ice and hydrocarbons found in the rings surrounding the outer planets". As a noted author of essays on the possibilities of science in the future, Dyson's theories, such as the Dyson sphere and the Dyson tree, have become popular in the scientific and science fiction communities. The more whimsically named "Astrochicken" has not achieved this same level of fame. See also Bioship Grey goo Intergalactic travel Interstellar travel Panspermia Self-replicating machine Space colonization Von Neumann probe References Artificial life Robotics concepts Hypothetical spacecraft Freeman Dyson Thought experiments in physics Self-replicating machines