Blueshift

A blueshift is any decrease in wavelength, with a corresponding increase in frequency, of an electromagnetic wave; the opposite effect is referred to as redshift. In visible light, this shifts the color from the red end of the spectrum to the blue end.

Doppler blueshift

Doppler blueshift is caused by movement of a source towards the observer. The term applies to any decrease in wavelength and increase in frequency caused by relative motion, even outside the visible spectrum. Only objects moving at near-relativistic speeds toward the observer are noticeably bluer to the naked eye, but the wavelength of any reflected or emitted photon or other particle is shortened in the direction of travel.

Doppler blueshift is used in astronomy to determine relative motion:

Half-Life 2

Half-Life 2 (stylized as HλLF-LIFE²) is a first-person shooter video game and the sequel to Half-Life (1998). Developed by Valve Corporation, it was released on November 16, 2004, following a five-year $40 million development, during which a substantial part of the project was leaked and distributed on the Internet. The game was developed alongside Valve's Steam software. It introduced the Source game engine and, because of Steam, was the first single-player video game to require online product activation.

Some years after the events of Half-Life, protagonist Gordon Freeman is woken by the enigmatic G-Man to find the world has been taken over by the alien Combine. Joined by allies including resistance fighter Alyx Vance, Gordon searches for a way to free humanity using a variety of weapons, including the object-manipulating gravity gun.

Like its predecessor, Half-Life 2 received critical acclaim. It was praised for its advanced physics, animation, sound, AI, graphics, and narrative. The game won 39 "Game of the Year" awards and the title of "Game Of The Decade" at the 2012 Spike Video Game Awards. Over 6.5 million copies of Half-Life 2 were sold at retail by December 3, 2008, (not including Steam sales); as of February 9, 2011, Half-Life 2 had sold over 12 million copies. Half-Life 2 is considered one of the greatest video games of all time.

Half-life (disambiguation)

Half-life is a mathematical and scientific description of exponential or gradual decay.

Half-life may also refer to:

Black operation

A black operation or black op is a covert operation by a government, a government agency, or a military organization. This can include activities by private companies or groups. Key features of a black operation are that it is secret and it is not attributable to the organization carrying it out. The main difference between a black operation and one that is merely secret is that a black operation involves a significant degree of deception, to conceal who is behind it or to make it appear that some other entity is responsible ("false flag" operations).

A single such activity may be called a "black bag operation"; that term is primarily used for covert or clandestine surreptitious entries into structures to obtain information for human intelligence operations. Such operations are known to have been carried out by the FBI, the Central Intelligence Agency,Mossad, MI6, ISI (Pakistan), RAW, MSS, and the intelligence services of other nations.

Etymology

"Black" may be used as a generic term for any government activity that is hidden or secret. For example, some activities by military and intel agencies are funded by a classified "black budget," of which the details, and sometimes even the total, are hidden from the public and from most congressional oversight.

Modern warfare

Modern warfare is warfare using the concepts, methods, and military technology that have come into use during and after World War II and the Korean War. The concepts and methods have assumed more complex forms of the 19th- and early-20th-century antecedents, largely due to the widespread use of highly advanced information technology, and combatants must modernize constantly to preserve their battle worthiness. Although total war was thought to be the form of international conflicts from the experience of the French Revolutionary Wars to World War II, the term no longer describes warfare in which a belligerent use all of its resources to destroy the enemy's organized ability to engage in war. The practice of total war which had been in use for over a century, as a form of war policy, has been changed dramatically with greater awareness of tactical, operational, and strategic battle information.

War in modern times has been the inclusion of civilians and civilian infrastructure as targets in destroying the enemy's ability to engage in war. The targeting of civilians developed from two distinct theories. The first theory was that if enough civilians were killed, factories could not function. The second theory was that if civilians were killed, the enemy would be so demoralized that it would have no ability to wage further war. However, UNICEF reports that civilian fatalities are down from 20 percent prior to 1900 AD to less than 5 percent of fatalities in the wars beginning in the 1990s.