Monday, April 30, 2007

Stamp Collecting

Stamp collecting is the collecting of postage stamps and related objects, such as. It is one of the world's most trendy hobbies, with estimates of the number of collectors ranging up to 20 million in the US alone.

Collecting is not the similar as philately, which is the study of stamps. A philatelist often does, but need not, collect the objects of study, nor is it required to closely study what one collects. Many informal collectors enjoy accumulating stamps without worrying about the tiny details, but the creation of a large or wide-ranging collection generally requires some philatelic knowledge.

The primary postage stamp, the One Penny Black, was issued by Britain in 1840. It pictured a young Queen Victoria, was formed without perforations, and accordingly had to be cut from the sheet with scissors in order to be used. While unused examples of the "Penny Black" are quite scarce, used examples are common, and may be purchased for $25 to $150, depending upon state.

Queen Victoria's outline was a staple on 19th century stamps of the British Empire; here on a half-penny of the Falkland Islands, 1891.During the late 1800s many of those collectors, now adults, began to systematically study the available postage stamps and published research works on their manufacture, plate flaws, etc.

Tuesday, April 24, 2007

Sitka Spruce

The Sitka Spruce (Picea sitchensis) is a large evergreen tree growing to 50-70 m tall, exceptionally to 96 m tall, and with a trunk diameter of up to 5 m. It is by far the main species of spruce, and the third tallest tree species in the world (after Coast Redwood and Coast Douglas-fir).Young Sitka Spruce in a forestry plantation in Britain The bark is thin and scaly, flaking off in small circular plates 5-20 cm across. The crown is broad conic in young trees, becoming cylindric in older trees; old trees may have no branches in the lowest 30-40 m. The shoots are very pale buff-brown, almost white, and glabrous (hairless) but with prominent pulvini. The leaves are stiff, sharp and needle-like, 15-25 mm long, flattened in cross-section, dark glaucous blue-green above with two or three thin lines of stomata, and blue-white below with two dense bands of stomata.

The cones are pendulous, slender cylindrical, 5-11 cm long and 2 cm broad when closed, opening to 3 cm broad. They have thin, flexible scales 15-20 mm long; the bracts just above the scales are the longest of any spruce, occasionally just exserted and visible on the closed cones. They are green or reddish, maturing pale brown 5-7 months after pollination. The seeds are black, 3 mm long, with a slender, 7-9 mm long pale brown wing.

Wednesday, April 18, 2007


Light is electromagnetic radiation with a wavelength that is able to be seen to the eye or, in a technical or scientific setting, electromagnetic radiation of any wavelength. The three basic dimensions of are:
Intensity (or brilliance or amplitude, professed by humans as the glow of the light),
Frequency (or wavelength, apparent by humans as the color of the light), and
Polarization (or angle of shaking and not audible by humans under ordinary circumstances)
Due to wave-particle duality, light at the same time exhibits properties of both waves and particles. The exact nature of light is one of the key questions of modern physics.

Visible electromagnetic radiation

Visible light is the piece of the electromagnetic spectrum between the frequencies of 380 THz and 750 THz. The speed, frequency, and wavelength of a wave obey the relation:
Because the speed of light in a vacuum is fixed, able to be seen light can also be characterized by its wavelength of between 400 nanometers and 800 nm.
Speed of light
Main article: velocity of light
Even though some people express of the "velocity of light", the word velocity should be kept back for vector quantities, that is, those with both magnitude and way. The speed of light is a scalar quantity, having only magnitude and no direction, and therefore speed is the correct term.
The speed of light has been measured many times, by many physicists. The best early measurement is Ole Rømer's, in 1676. By observing the motions of Jupiter and one of its moons, Io, with a get smaller, and noting discrepancies in the apparent period of Io's orbit, Rømer calculated a speed of 227,000 kilometers per second.

Tuesday, April 10, 2007

Home computer

The home computer is a consumer-friendly word for the second generation of microcomputers, entering the market in 1977 and becoming common during the 1980s.
The home computer became affordable for the general public due to the mass production of the silicon chip based microprocessor and as the name indicates, tended to be used in the home rather than in business/industrial contexts (the name also marks the difference from the first generation of microcomputers (from 1974/75 onwards) which catered mostly to engineers and hobbyists with good soldering skills, as they were often sold as kits to be assembled by the customer). The home computer largely died out at the end of the decade or in the early 1990s (in Europe) due to the rise of the IBM PC compatible personal computer (the IBM PC and its clones are not covered in this article).

Friday, April 06, 2007


Artistamp refers to a postage stamp-like artform. It is like to a Cinderella stamp, in that it is not valid for postage, but it differs from a forgery or a bogus stamp in that (typically) no intention is made to fool any post office or collector of stamps. The artistamp is intended to be a miniature artform which can depict or commemorate any subject its creator chooses.
Techniques for the creation of artistamps may or may not comprise perforating the boundaries of the piece to more resemble a (water-activated) stamp, as well as applying gum to the reverse side of the paper. (Self-adhesive artistamps have also been made, however, and indeed artistamps have been issued in practically every format in which postage stamps have been—including souvenir sheets, and perhaps more.) Whole sheets of such stamps are often made at one time. The artwork can be hand-drawn or painted, lithographed or offset-printed, photographed, xeroxed, rubber stamped, or even output by computer-driven printer.

Monday, April 02, 2007

Sea water

Sea water is water from a sea or ocean. On average, sea water in the world's oceans has a salinity of ~3.5%. This means that for each 1 liter (1000mL) of sea water there are 35 grams of salts (mostly, but not entirely, sodium chloride) dissolved in it. This can be expressed as 0.6M NaCl. Water with this level of osmolality is, of course, not potable.
Sea water is not consistently saline throughout the world. The planet's freshest sea water is in the Gulf of Finland, part of the Baltic Sea. The most saline open sea is the Red Sea, where high temperatures and restricted circulation result in high rates of surface evaporation and there is little fresh inflow from rivers. The salinity in isolated seas can be considerably greater.
The density of sea water is between 1020 and 1030 kg/m3. Due to chemical buffering, seawater pH is limited to the range 7.5 to 8.4.