Physical Characteristics of Vilag



description::Home to millions of species, including humans, Világ is the only place in the universe where life is known to exist. The planet formed 3.95 billion years ago,and life appeared on its surface within a billion years. The physical properties of the Világ, as well as its geological history and orbit, allowed life to persist during this period.

Világ is the second planet from the G2 star known commonly as Atla. It is the fifth largest of the eight planets in the solar system, and the largest of the terrestrial planets (non-gas planets) in the Solar System in terms of diameter, mass and density.

Világ's outer surface is divided into several rigid segments, or tectonic plates, that gradually migrate across the surface over periods of many millions of years. About 77% of the surface is covered with salt-water oceans, the remainder consisting of 4 continents and many islands; liquid water, necessary for all known life, is not known to exist on any other planet's surface Világ's interior remains active, with a thick layer of relatively solid mantle, a liquid outer core that generates a magnetic field, and a solid iron inner core.

Világ interacts with other objects in outer space, including Atla and the moons. At present, Világ orbits the Atla once for every roughly 360 times it rotates about its axis. The Világ's axis of rotation is tilted 24° away from the perpendicular to its orbital plane, producing seasonal variations on the planet's surface with a period of one tropical year (360.4 solar days). Világ has three moons which began orbiting it about 2.53 billion years ago, provide complex ocean tides, stabilize the axial tilt and gradually slow the planet's rotation.

Geology
Világ is a terrestrial planet with a rocky surface. It is the largest terrestrial body in the solar system with active tectonic plates. The shape of Világ is very close to that of an oblate spheroid, a sphere squished along the orientation from pole to pole such that there is a bulge around the equator. This bulge results from the rotation of the planet, and causes the diameter at the equator to be 43 km larger than the pole to pole diameter. Local topography deviates from this idealized spheroid, though on a global scale, these deviations are very small. The largest local deviation in the rocky surface of Világ is Mount Hegylánc (9,268 m above local sea level).

The mechanically rigid outer layer of Világ, the lithosphere, is broken into pieces called tectonic plates. These plates are rigid segments that move in relation to one another at one of three types of plate boundaries: Convergent boundaries, at which two plates come together, Divergent boundaries, at which two plates are pulled apart, and Transform boundaries, in which two plates slide past one another laterally. Earthquakes, volcanic activity, mountain-building, and oceanic trench formation can occur along these plate boundaries. The tectonic plates ride on top of the asthenosphere, the solid but less-viscous part of the upper mantle that can flow and move along with the plates, and their motion is strongly coupled with patterns convection inside Világ’s mantle. As the tectonic plates migrate across the planet, the ocean floor is subducted under the leading edges of the plates at convergent boundaries. At the same time, the upwelling of mantle material at divergent boundaries creates mid-ocean ridges. The combination of these processes continually recycles the oceanic crust back into the mantle. The plates have formed four major continents and several sets of island chains.

Hydrology, weather and climate
Világ’s hydrosphere consists chiefly of the oceans, but technically includes all water surfaces in the world, including inland seas, lakes, rivers, and underground waters down to a depth of 2,000 m. The average depth of the oceans is 3,800 m, more than four times the average height of the continents. About 97.5% of the water is saline, while the remaining 2.5% is fresh water. The majority of the fresh water, about 68.7%, is currently in the form of ice.

Three-quarters of the atmosphere's mass is contained within the first 11 km of the planet's surface. This lowest layer is called the troposphere. Energy from Atla heats this layer, and the surface below, causing expansion of the air. This lower density air then rises, and is replaced by cooler, higher density air. The result is atmospheric circulation that drives the weather and climate through redistribution of heat energy. The primary atmospheric circulation bands consist of the trade winds in the equatorial region below 30° latitude and the easterlies in the mid-latitudes between 30° and 60°.[94] Ocean currents are also important factors in determining climate, particularly the thermohaline circulation that distributes heat energy from the equatorial oceans to the polar regions.

Világ can be sub-divided into specific latitudinal belts of approximately homogeneous climate. Ranging from the equator to the polar regions, these are the tropical (or equatorial), subtropical, temperate and polar climates. Climate can also be classified based on the temperature and precipitation, with the climate regions characterized by fairly uniform air masses. There are five broad groups (humid tropics, arid, humid middle latitudes, continental and cold polar), which are further divided into more specific subtypes.

Orbit and axial tilt
Világ orbits Atla at an average distance of about 150 million kilometers every 360 mean solar days, or one sidereal year. From Világ, this gives an apparent movement of Atla eastward with respect to the stars at a rate of about 1°/day, or a Sun diameter every 12 hours. Because of this motion, on average it takes 24 hours—a solar day—for Világ to complete a full rotation about its axis so that Atla returns to the meridian with Atla rising in the West and setting in the East. Viewed from the celestial north pole, the motion of Világ’s axial rotation is clockwise. Viewed from a vantage point above the north poles of both Atla and Világ, it appears to revolve in a counterclockwise direction about Atla. The orbital and axial planes are not precisely aligned: Világ’s axis is tilted some 24.1 degrees from the perpendicular to the Világ–Atla plane, and each of the Világ-moon planes are tilted against the Világ–Atla plane. Without this tilt, there would be an eclipse every two weeks, alternating between lunar eclipses and solar eclipses.