Sunday, December 13, 2009

The Sun

The Sun is a star of spectral classification G2:
Diameter: 1,392,000 km 1.392×106 km.
Mass: 1.989e30 kg 1.988 435×1030 kg
Temperature: 5800 K (surface); 13,600,000 K (core)
Mean distance from Earth: 149.6×106 km
The Sun is the largest object in the solar system and contains more than 99.8% of the total mass of the Solar System. About 74% of the Sun's mass is hydrogen, 25% is helium, and the rest is made up of trace quantities of heavier elements. This proportion changes slowly over time as the Sun converts hydrogen to helium in its core in a nuclear fusion; the Sun is in a state of hydrostatic balance, neither contracting nor expanding over time. Conditions at the Sun's core (approximately the inner 25% of its radius) are extreme. The temperature is 15.6 million Kelvin and the pressure is 250 billion atmospheres. At the center of the core the Sun's density is more than 150 times that of water.
The Sun's energy output (3.86e33 ergs/second or 386 billion megawatts) is produced by nuclear fusion reactions. Each second about 700,000,000 tons of hydrogen are converted to about 695,000,000 tons of helium and 5,000,000 tons (=3.86e33 ergs) of energy in the form of gamma rays. As it travels out toward the surface, the energy is continuously absorbed and re-emitted at lower and lower temperatures so that by the time it reaches the surface, it is primarily visible light. For the last 20% of the way to the surface the energy is carried more by convection than by radiation.
Energy from the Sun—in the form of insolation from sunlight—supports almost all life on Earth via photosynthesis, and is the main factor of the Earth's climate and weather.
Observed from Earth, the path of the Sun across the sky varies throughout the year. In the ancient world, interventions in the landscape were means to interpret celestial events by observation of the setting and rising of the Sun. The meaning of visual observations often went beyond their perceptional value to gain a metaphysical and religious interpretation, becoming source for myths and rituals. In ancient cosmologies the perceived landscape became an image of the universe. The Sun was personified in many mythologies: the Greeks called it Helios and the Romans called it Sol.

In the contemporary world we constantly witness the disconnection between nature and the built environment. Recent cosmological theories have revealed themselves as mathematical equations abstracted from the physical relations with the world. This disconnection from nature has often led to disastrous consequences in the environment. In the more recent decades, attention on environmentally sensitive and sustainable design has emerged. Sustainability requires reconnecting the lost connection with nature and the Sun which makes life on Earth possible. Sun Geometries arises as a contemporary expression of our connection with land and sky. Its connection with the Sun is manifested in its shape and by its materials: photovoltaic panels collecting solar energy. It brings awareness of where we are in space and time: its section is sloped at an angle parallel to the latitude of its location pointing to the North Star while casting shadows to tell us the time of the day and day of the year.