Welcome to Planet Tech. This section includes information on the geology, planetary physics and life-forms (if
present) on a variety of planets. Which planet would you like to visit today Earthling?
|Star System: more coming soon ...
What is a planet?
There has much controversy on Earth about what the single word 'planet' really means. Originally the term planet
meant 'wanderer' and applied to any light that moved across the night sky in a regular way that did not match the
background motions of the stars, and so it included the Moon and the Sun. The seven known planets to the
ancients were the Sun, Moon, Mercury, Venus, Mars, Jupiter and Saturn. Later more were discovered, and the
Sun was found to be a star, the Moon to orbit the Earth and the Earth to be a planet. Thus the list of planets came
to include: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. Pluto has since been
dropped according to a very awkward and artificial re-definition of the word 'planet' and re-designated a 'dwarf
planet', which is not a planet, allegedly, by some grammatical feet that defies all logic. (Even though a giant planet
is still a planet). Furthermore, a number of the satellites of the planets are planets in every respect, including size,
accept that they primarily orbit other planets and only secondarily orbit the Sun.
Bot prefers a more natural system of classification. Anything smaller than about 500 km in diameter tends to be
irregular in shape and can be considered a very separate category of objects. Objects with a minimum diameter
above 1000 km are certainly planets in the natural sense of the word - they are spheroid and have a rich
geological history and probably share similar formation mechanisms (accretion from the primary proto-stellar
disc). Objects between 500 and 1000 km radius, but which appear spherical, are possibly produced by slightly
different mechanisms (such as accretion around a captured comet nucleus) and so can be considered planetoids
or dwarf planets. The term 'dwarf planet' is no more precise than the term 'giant planet', but may be used for small
planet-sized bodies, especially when they fall into the 'grey' area between 500 and 1000 km. 'Planets' that are
satellites of other larger planets are essentially secondary planets. Planets that orbit planets that orbit larger
planets are tertiary planets, etc. No definition can be exact without exact knowledge, but science perhaps ought to
adopt terms that appear most natural according to known science.
There is an argument for dropping the word 'planet' altogether since it has been so politically abused that it is
almost obsolete. Given the lack of scientific basis for exact definitions, each should use the terms as they prefer,
until proof and reason dictate otherwise. Bot's natural classification system is more in line with that in common
usage by the Intergalactic Astronomical Union (IAU).
|Life-supporting Planet Types