The International Date Line (IDL) is an imaginary line on the surface of the Earth, established by the International Meridian Conference of 1884, that runs from the north to the south pole and demarcates one calendar day from the next. It passes through the middle of the Pacific Ocean, roughly following the 180° longitude but it deviates to pass around some territories and island groups. The IDL is on the opposite side of the Earth to the Prime Meridian. The Prime Meridian is used to define Universal Time and is the meridian from which all other time zones are calculated. Time zones to...

A palindrome is a word, phrase, number, or other sequence of symbols or elements, whose meaning may be interpreted the same way in either forward or reverse direction. Famous examples include "Amore, Roma", "A man, a plan, a canal: Panama" and "No 'x' in 'Nixon'". Composing literature in palindromes is an example of constrained writing. The word "palindrome" was coined from the Greek roots ' (; "again") and ' (; "way, direction") by the English writer Ben Jonson in the 17th century. The Greek phrase to describe the phenomenon is ' (; "crab inscription"), or simply karkinoi (; "crabs"),...

The Father-Thing is a 1954 science fiction short story by Philip K. Dick. The story, written from a child's point of view, concerns the replacement of a boy's father by a replicated version. Only the child sees the difference and has to recruit other children to help him reveal the truth. The story is typical of Dick's short stories of the period, and also reminiscent of some of the short fiction of Ray Bradbury. The premise was widely used in fiction of the time. Works like Who Goes There? and, most famously Invasion of the Body Snatchers, especially popular in the 1950s, expressed the...

Un ser vivo u organismo es un conjunto estructural material de organización compleja, en la que intervienen sistemas de comunicación molecular que lo relacionan internamente y con el medio ambiente en un intercambio de materia y energía de una forma ordenada, teniendo la capacidad de desempeñar las funciones básicas de la vida que son la nutrición, la relación y la reproducción, de tal manera que los seres vivos actúan y funcionan por sí mismos sin perder su nivel estructural hasta su muerte. La materia que compone los seres vivos está formada en un 95% por cuatro elementos (bioelementos...