Thursday, March 29, 2007

Major ice ages

There have been at least four main ice ages in the Earth's past.

The earliest hypothesized ice age is believed to have occurred around 2.7 to 2.3 billion years ago through the early Proterozoic Age.

Main article: Snowball Earth.

The most primitive well-documented ice age, and probably the most harsh of the last 1 billion years, occurred from 800 to 600 million years ago and it has been suggested that it formed a Snowball Earth in which permanent sea ice extensive to or very near the equator. It has been not compulsory that the end of this ice age was responsible for the subsequent Cambrian Explosion, though this theory is current and contentious.

The timing of ice ages all through geologic history is in part prohibited by the position of the continental plates on the surface of the Earth. When landmasses are determined near the Polar Regions, there is an increased chance for snow and ice to build up. Small changes in solar energy can tip the balance between summers in which the winter snow mass completely melts and summers in which the winter snow persists until the following winter. Due to the positions of Greenland, Antarctica, and the northern portions of Europe, Asia, and North America in Polar Regions, the Earth today is considered prone to ice age glaciations.

Proof for ice ages comes in a variety of forms, including rock scouring and scratching, glacial moraines, drumlins, valley cutting, and the deposition of till or tillites and glacial erratic. Successive glaciations be inclined to distort and erase the geological proof, making it difficult to interpret. It took some time for the current theory to be worked out. Analyses of ice cores and ocean sediment cores unmistakably show the record of glacial and interglacial over the past few million years.

Sunday, March 25, 2007

Banksia

Banksia is a genus of around 80 species in the plant family Proteaceae. They are native to Australia, occurring in all but the most arid areas. Easily recognized by their characteristic flower spikes and fruiting "cones", Banksia are a well-known Australian wildflower and a popular garden plant. They grow in forms varying from prostrate woody shrubs to trees up to 25 metres tall. They are normally known as Banksias or Australian Honeysuckle Trees.
Banksias grow as trees or woody shrubs. The largest trees, the Coast Banksia, B. integrifolia, and the River Banksia, B. seminuda, often grow over 15 metres tall, and may be up to 25 metres tall. Banksia species that grow as shrubs are typically erect, but there are some species that are prostrate, with branches that grow on or below the soil.
The leaves of Banksia vary greatly among species. Sizes vary from the narrow, 1–1½ centimetre long leaves of the Heath-leaved Banksia, B. ericifolia, to the very large leaves of the Bull Banksia, B. grandis, which may be up to 45 centimetres long. The leaves of most species have serrated edges, but a few, such as B. integrifolia, do not. Leaves are usually arranged along the branches in irregular spirals, but in some species they are crowded together in whorls.
Banksias are most without difficulty recognised by their characteristic flower spike, and the woody fruiting structures that appear after flowering. The flower spike consists of a central woody axis with a furry coating; it is usually held erect, but hangs down in a few species. This axis is enclosed in tightly-packed pairs of flowers, which are attached to the axis at right angles. A single flower spike may have over a thousand flowers.

Tuesday, March 20, 2007

Studio cameras

Most studio cameras stand on the floor, regularly with pneumatic or hydraulic mechanisms to adjust the height, and are typically on wheels. Any video camera when used along with other video cameras in a studio setup is controlled by a device well-known as CCU (camera control unit), to which they are linked via a Triax or Multicore cable. The camera control unit along with other equipments is installed in the production control room often documented as Gallery of the television studio. When used outside a studio, they are often on tracks. Initial models used analog technology, but digital models are becoming more common. Some studio cameras are light and small enough to be taken off the pedestal and used on a cameraman's shoulder, but they still have no recorder of their own and are cable-bound.

Wednesday, March 14, 2007

Haze

Haze is an atmospheric occurrence where dust, smoke and other pollutant particles obscure the usual clarity of the sky. It occurs when dust and smoke particles build up in relatively dry air. When weather conditions block the dispersal of smoke and other pollutants they concentrate and form a generally low-hanging shroud that impairs visibility and may become a respiratory health threat. Dense haze caused by industrial pollution is also known as smog.
Sources for haze particles include farming (ploughing in dry weather), traffic, industry, forest fires and peat field fire.
Seen from afar (e.g. approaching airplane), haze is brownish, while mist is more blueish-grey. While haze is formed in somewhat dryish air, in more humid air mist is formed, and the haze particles can even act as condensation nuclei for the mist droplets.

Friday, March 09, 2007

Mirror

A mirror is an object whose surface has good specular reflection; that is, it is smooth sufficient to form an image. The most common type of mirror is the plane mirror, which has a flat surface. Curved mirrors are also used, to produce magnified or demagnified images or focus light.
The most common use of mirrors is for personal hygiene. However, mirrors are also used in scientific apparatus such as telescopes and lasers, as well as industrial machinery. Most mirrors are designed for visible light, however, mirrors intended for other wavelengths of electromagnetic radiation are also used, particularly in optical instruments.

Monday, March 05, 2007

The Leaning Tower of Pisa

The Leaning Tower of Pisa (Italian: Torre pendente di Pisa) or simply The Tower of Pisa (La Torre di Pisa) is the campanile, or self-supporting bell tower, of the cathedral of the Italian city of Pisa. It is situated behind the Cathedral and it is the third structure in Pisa's Campo dei Miracoli (field of Miracles).
Although planned to stand vertically, the tower began leaning to the southeast soon after the onset of construction in 1173 due to a poorly laid foundation and loose substrate that has permitted the foundation to shift.
The height of the tower is 55.86 m (183.27 ft) from the ground on the lowest side and 56.70 m (186.02 ft) on the highest side. The width of the walls at the base is 4.09 m (13.42 ft) and at the top 2.48 m (8.14 ft). Its weight is estimated at 14,500 tonnes. The tower has 294 steps.
The Tower of Pisa was a work of art, performed in three stages over a period of about 174 years. Construction of the first floor of the white marble campanile began on August 9, 1173, a period of military success and prosperity. This first floor is enclosed by pillars with classical capitals, leaning against blind arches. Today, it is still unscarred from centuries of weather and age.

Thursday, March 01, 2007

Mobile

A mobile or cellular telephone is a long-range, transferable electronic device for personal telecommunications over long distances. In addition to the standard voice function of a telephone, current mobile phones can support many additional services such as SMS for text messaging, email, packet switching for access to the Internet, and MMS for sending and receiving photos and video. Most current mobile phones attach to a cellular network of base stations (cell sites), which is in turn interconnected to the public switched telephone network (PSTN) (the exception are satellite phones).
Mobile phones are not distinct from cordless telephones, which usually operate only within a limited range of a specific base station. In principle, the term mobile phone includes such devices as satellite phones and pre-cellular mobile phones such as those operating via MTS which do not have a cellular network, whereas the linked term cell(ular) phone does not. In practice, the two terms are used almost interchangeably.