Sunday, August 26, 2007

Electron microscopes

Electron microscopes, which use beams of electrons as a substitute of light, are designed for very high magnification usage. Electrons, which have a much smaller wavelength than visible light, allow a much higher resolution. The main limitation of the electron beam is that it must pass through a vacuum as air molecules would otherwise scatter the beam.

Sunday, August 19, 2007

Persian orange

The Persian orange, grown-up widely in southern Europe after its introduction to Italy in the 11th century, was bitter. Sweet oranges bring to Europe in the 15th century from India by Portuguese traders, rapidly displaced the bitter, and are now the most common variety of orange cultivated. The sweet orange will grow to different sizes and colors according to local conditions, most commonly with ten carpel’s, or segments, inside.

Sunday, August 12, 2007


A solstice occur twice a year, whenever Earth's axis tilts the most toward or away from the Sun, causing the Sun to be farthest north or south at noon. The name is derivative from Latin sol (sun) and sistere (to stand still), because at the solstice, the Sun stands still in declination, that is, its movement north or south is minimal. The term solstice can also be used in a wider sense as the date (day) that such a passage happens. The solstices, together with the equinoxes, are related to the seasons. In some languages they are considered to start or separate the seasons; in others they are considered to be center points.

Friday, August 03, 2007

Pedestrian crossings

Pedestrians must often traverse from one side of a road to the other, and in doing so may come into the way of vehicles traveling on the road. In many places pedestrians are completely left to look after themselves, that is, they must observe the road and cross when they can see that no traffic will threaten them. Busier cities usually provide pedestrian crossings, which are strips of the road where pedestrians are expected to traverse.