Reflection nebulae reflect light from nearby stars.
Dark nebulae do not emit light or reflect light. They block the light from stars that are far away.
Planetary nebulae are quite common, because they are produced by red giant stars late in their lives. These stars usually become white dwarfs, leaving behind an expanding ball of ionized gas, which we see as a roughly circular bright nebula.
A supernova occurs when a high-mass star reaches the end of its life. When nuclear fusion in the core of the star stops, the star collapses and explodes . The expanding shell of gas forms a supernova remnant. The Crab nebula is a supernova remnant which probably exploded in 1054 AD. Light and X-ray emission from supernova remnants comes from ionized gas. There is a huge amount of radio emission called synchrotron emission. This emission originates from high-velocity electrons oscillating in magnetic fields.
Database schema
In computer science a "schema" or database schema describes the structure of a database in a formal language that is supported by the database management system. Using the database schema, it is possible to create a blueprint of the database. This blueprint will not contain any data. The database schema uses logical formulas to create integrity constraints. It is not possible to insert data into the database that violates these integrity constraints. All contraints use the same language.
There are different kinds of database schemas:
Ideally, a database schema should have the following properties:
Ernst Haeckel
Ernst Heinrich Philipp August Haeckel (16 February 1834 – 9 August 1919) was an influential German zoologist, naturalist, and artist. He was also a philosopher and physician, but in those fields he is not regarded as particularly notable. He was an atheist. He left the Lutheran church in 1910. He is regarded as a pioneer of eugenics and Nazi eugenics in Germany.
Haekel was professor of comparative anatomy at the University of Jena, where he worked for 47 years, from 1862 to 1909. Haekel discovered, described and named thousands of new species, mapped a tree of life relating all life forms. He coined many terms in biology, including "ecology", "phylum", "phylogeny", "stem cell", and the kingdom "Protista." Haeckel promoted and popularised Charles Darwin's work in Germany and developed the controversial recapitulation theory ("ontogeny recapitulates phylogeny"). This clained that an individual organism's biological development, or ontogeny, parallels and summarises its species' evolutionary development.
The published artwork of Haeckel includes over 100 detailed, multi-colour illustrations of animals and sea creatures. As a philosopher, Ernst Haeckel wrote "Die Welträtsel" (1895–1899, "The Riddle of the Universe", 1901), and "Freedom in Science and Teaching" to support teaching evolution.
Haeckel was a member of the nationalist and antisemitic Pan-German League (German: "Altdeutscher Verband") and of the peace organization Verband für internationale Verständigung.
Haekel wrote many books, some of them in multi-volumes. Among the most notable are:
Lunar eclipse
A lunar eclipse is an astronomical phenomenon. It happens when the moon passes through the shadow of the Earth which can only occur during a full moon. Lunar eclipses happen about twice a year, unlike total solar eclipses that are sometimes more than a year apart. They can be seen from a much larger portion of the Earth compared to solar eclipses. Lunar eclipses can last for a few hours, but total solar eclipses last only a few minutes.
During a lunar eclipse, the Moon looks red-brown. It may be thought that the Moon is completely black because of the Earth's shadow, but no. The reddish-brown color is because some of the Sun's light bends through the Earth's atmosphere and shines on the Moon. Refraction is greater for red light rays than for others, so red is what strikes the Moon.
Like solar eclipses, there are different types of lunar eclipses. There are total eclipses, where the moon passes completely through Earth's shadow and all of the moon appears reddish-brown. A partial eclipse occurs when only part of the moon passes through Earth's shadow and so only part of the moon appears reddish-brown.
Lunar eclipses are safe to view with just your eyes and also with telescopes.
Max Weber
Maximilian Carl Emil Weber (pronounced: maks ˈveːbɐ) (21 April 1864 – 14 June 1920) was a German political economist and sociologist who was considered one of the founders of the modern study of sociology and public administration. He began his career at the University of Berlin, and later worked at Freiburg University, University of Heidelberg, University of Vienna and University of Munich. He had influence on German politics of his time, because he was an advisor to Germany's at the Treaty of Versailles and to the commission that drafted the Weimar Constitution.
Weber is known for his work in the sociology of religion. His most famous work is his essay "The Protestant Ethic and the Spirit of Capitalism".
He disagreed with Karl Marx' view that class structure was the way to view how society worked. He believed that human values affected how people acted throughout history.
Weimar Constitution
The Constitution of the German Reich (German: "Die Verfassung des Deutschen Reiches"), usually known as the Weimar Constitution ("Weimarer Verfassung") was the constitution that governed the Weimar Republic (1919-1933). The constitution technically remained in effect during the Third Reich from 1933 to 1945.
The German state's official name was "Deutsches Reich" until the adoption of the 1949 constitution.
Following the end of World War I, a German National Assembly gathered in the town of Weimar, in the state of Thuringia, in January 1919 to write a constitution for the "Reich". The nation was to be a democratic federal republic, governed by a president and parliament.
The constitution was drafted by the lawyer and liberal politician "Hugo Preuss", who was then state secretary in the Ministry of the Interior and later became Minister of the Interior.
Guitar Hero III Mobile
Guitar Hero III Mobile is a music video game for mobile phones. It was made by MachineWorks Northwest LLC and sold by Hands-On Mobile. It is the newest game in the "Guitar Hero" series, and was released on December 20, 2007, in North America for people using Verizon Wireless.
"Guitar Hero III Mobile" was programmed by Robinson Technologies (shortened to RTSoft), with help from MachineWorks Northwest LLC. The graphics for the game were made by Anthem Game Group.
Playing "Guitar Hero III Mobile" is similar to playing other games in the "Guitar Hero" series. "Mobile" uses 3 frets instead of 5. Each column of numbered keys on a phone's keypad is a fret. The numbered keys used are "1", "4", and "7" for green notes, "2", "5", and "8" for red notes, and "3", "6", and "9" for yellow notes. Once the note(s) reach the bottom, the player must play the note(s) by pressing or holding down the number key(s) in order to score points. Players can turn on Star Power to get more points by the "*" (star) button on the keypad or the "OK" button in the center of the directional pad.
"Guitar Hero III Mobile" has 15 songs to play from "Guitar Hero II" and "". Every month, more songs can be downloaded.
Avicenna
Avicenna ( 980 – 1037) was a Persian polymath and the most important doctor and Islamic philosopher of his time.
He wrote about 450 works on a wide range of subjects, and about 240 have survived, including 150 on philosophy and 40 on medicine.
His most famous works are "The Book of Healing" – a philosophical and scientific encyclopedia, and "The Canon of Medicine" – a medical encyclopedia.
He is also known as Ibn Sīnā and Pour Sina () which means "Son of Sina" in English. His full name in Arabic is (). In English, he is usually called "Avicenna" (), his Latinized name.