Lonelygirl15

[Xrynaem]

[Luv2Luvem]

[horcruxes]

[Xrynaem]

[Danielle]

i think i hate this thread.
yeap
_________________
<DTayl> actually i'm the bad sister
<DTayl> i drink, i stay out too late, i swear, i'm mean, i spend too much money and i got a tattoo
<DTayl> Laura turned 9
<DTayl> i'm the bad sister

[Luv2Luvem]

[ladron121]

[Danielle]

ooooh lad ftw.
_________________
<DTayl> actually i'm the bad sister
<DTayl> i drink, i stay out too late, i swear, i'm mean, i spend too much money and i got a tattoo
<DTayl> Laura turned 9
<DTayl> i'm the bad sister

[Xrynaem]

[ladron121]

ITS A FLAME THREAD NOW!!!

SOME Operator CLOSE IT BEFORE FEELINGS ARE REALLY HURT!!!

[mourningbelle]

A covert operation is a military or political activity performed in secrecy that would break specific laws or compromise policy in another country. Covert operations almost always illegal in the target state and are sometimes in violation of the laws of the enacting country.

Covert operations employed in situations where openly operating against a target would be politically or diplomatically risky, or jeopardize the mission's success. In the case of enemies, there may be issues regarding military strength, treaties, laws, moral principles, or aversion to negative media attention. Operations may be directed at allies and friends to secure their support or to influence their policy against an enemy. Covert operations differ from espionage by attempting to influence events in another country rather than gathering information about it.

The best-known organizations specializing in covert operations today are the Central Intelligence Agency and the U.S. Department of Defense (The Pentagon), but covert operations have been employed by many national and sub-national governments and other organizations for centuries, with or without a formal intelligence agency. They are an established and often controversial component of foreign policy throughout the world. The equivalent Soviet terminology would be "active measures".

Law enforcement agencies also use covert operations to infiltrate suspected criminal organizations.

---

Aphids, also known as greenfly, blackfly or plant lice, are minute plant-feeding insects in the superfamily Aphidoidea in the homopterous division of the order Hemiptera. Recent classification within the Hemiptera has changed the old term 'Homoptera' to two suborders: Sternorryncha (aphids, whiteflies, scales, psyllids...) and Auchenorryncha (cicadas, leafhoppers, treehoppers, planthoppers...) with the suborder: Heteroptera containing a large group of insects known as the 'true-bugs'; gnat bugs, pond skaters, shore bugs, toad bugs, water boatmen, backswimmers, etc.

About 4,000 species of aphids are known, classified in 10 families; of these, around 250 species are serious pests for agriculture and forestry as well as an annoyance for gardeners. They vary in size from 1-10 mm long.

Important natural enemies include the predatory ladybirds/ladybugs/ladybeetles (Coleoptera: Coccinellidae), hoverfly larvae (Diptera: Syrphidae), and lacewings (Neuroptera: Chrysopidae), and entomopathogenic fungi like Lecanicillium lecanii and the Entomophthorales.

Aphids are distributed world-wide, but they are most common in temperate zones. It is possible for aphids to migrate great distances (mainly through passive dispersal riding on winds) depending on the weather patterns; for example, the lettuce aphid spreading from New Zealand to Tasmania.[1] They have also been spread by human transportation of infested plant materials.
_________________
Dust on the window
The sun's darkened angle
Write your initials with mine
At this time tomorrow
I'll be just one day closer
One sunset further behind

[shifty]

Olongapo City is an urbanized city in the province of Zambales, Philippines. According to the 2000 census, it has a population of 194,260 people in 43,107 households. The name Olongapo is derived from the phrase "Ulo ng Apo", which means "head of the chief" in Tagalog.

Olongapo was originally governed as a part of the United States naval reservation. It was relinquished to the Philippine government and converted into a municipality on December 7 1959. Six years later Olongapo was reconverted to a chartered city on June 1 1966. Olongapo City administers itself autonomously from Zambales province. Adjacent to the city is the Subic Bay Freeport Zone, which until 1992 was a United States naval base.

[mourningbelle]

A tachyon (from the Greek ταχύς (takhús), meaning "swift, fast") is any hypothetical particle that travels at superluminal velocity. The first description of tachyons is attributed to German physicist Arnold Sommerfeld, but it was George Sudarshan[1][2] and Gerald Feinberg[3] (who originally coined the term) in the 1960s who advanced a theoretical framework for their study. Tachyons have recurred in a variety of contexts, such as string theory. In the language of special relativity, a tachyon is a particle with space-like four-momentum and imaginary proper time. A tachyon is constrained to the space-like portion of the energy-momentum graph. Therefore, it can never slow to light speed or below. The existence of tachyons has not been shown.

From a special relativity perspective a tachyon is a particle with space-like four-momentum. There are two equivalent approaches to handling their kinematics:

* Require that all the same formulae that apply to regular slower-than-light particles ("bradyons") also apply to tachyons. In particular the energy-momentum relation:



where p is the relativistic momentum of the bradyon and m is its rest mass still holds, along with the formula for the total energy of a particle:



which is interpreted to mean that the total energy of a particle (bradyon or tachyon) contains a contribution from the rest mass (the "rest mass-energy") and a contribution from the body's motion, the kinetic energy.
However the energy equation has, when v is larger than c', an "imaginary" denominator, since the value inside the square root is negative. Since the total energy must be real then the numerator must also be imaginary, i.e. the rest mass m must be imaginary, since a pure imaginary number divided by another pure imaginary number is a real number.

* An equivalent way of describing tachyons with real masses is to adapt Einstein's energy-momentum relation to read:



With this approach the energy equation becomes:



And we avoid any necessity for imaginary masses, sidestepping the problem of interpreting exactly what a complex-valued mass may physically mean.

Both approaches are equivalent mathematically and have the same physical consequences. One curious effect is that, unlike ordinary particles, the speed of a tachyon increases as its energy decreases. (For ordinary bradyonic matter, E increases with increasing velocity, becoming arbitrarily large as v approaches c, the speed of light.) Therefore, just as bradyons are forbidden to break the light-speed barrier, so too are tachyons forbidden from slowing down to below light speed 'c', since to reach the barrier from either above or below requires infinite energy.

Quantising tachyons shows that they must be spinless particles which obey Fermi-Dirac statistics, i,e. tachyons are scalar fermions, a combination which is not permitted for ordinary particles.[3] They also must be created and annihilated in pairs.

The existence of such particles would pose intriguing problems in modern physics. For example, taking the formalisms of electromagnetic radiation and supposing a tachyon had an electric charge—as there is no reason to suppose a priori that tachyons must be either neutral or charged— then a charged tachyon must lose energy as Cherenkov radiation— just as ordinary charged particles do when they exceed the local speed of light in a medium. A charged tachyon travelling in a vacuum therefore undergoes a constant proper time acceleration and, by necessity, its worldline forms a hyperbola in spacetime. However, as we have seen, reducing a tachyon's energy increases its speed, so that the hyperbola formed is of two oppositely charged tachyons with opposite momenta (same magnitude, opposite sign) which annihilate each other when they simultaneously reach infinite velocity. (At infinite velocity tachyons have no energy and finite momentum, so no conservation laws are violated in their mutual annihilation. The time of annihilation is frame dependent.) Even an electrically neutral tachyon would be expected to lose energy via gravitational Cherenkov radiation, since it has a gravitational mass, and therefore increase in velocity as it travels, as described above.

Some modern presentations of tachyon theory have demonstrated the possibility of a tachyon with a real mass. In 1973, Philip Crough and Roger Clay reported a superluminal particle apparently produced in a cosmic ray shower (an observation which has not been confirmed or repeated) [1]. This possibility has prompted some to propose that each particle in space has its own relative timeline, allowing particles to travel back in time without violating causality. Under this model, such a particle would be a "tachyon" by virtue of its apparent superluminal velocity, even though its rest mass is a real number.

Tachyons appear in many works of fiction. It has been used as a standby mechanism upon which many science fiction authors rely to establish faster-than-light communication, with or without reference to causality issues. The word "tachyon" has become widely recognized to such an extent that it can impart a science-fictional "sound" even if the subject in question has no particular relation to superluminal travel (compare positronic brain). Tachyon Publications, a science fiction and fantasy publishing company has produced over 40 titles since their inception in 1995, including works by such well known authors as Peter S. Beagle, Tim Powers, and Michael Swanwick.



Tachyon visualization. Since that object moves faster than the speed of light we can not see it approaching. Only after a tachyon has passed nearby, we could see two images of the tachyon, appearing and departing in opposite directions. The black line is the shock wave of Cherenkov radiation. It is shown only in one moment at time.


_________________
Dust on the window
The sun's darkened angle
Write your initials with mine
At this time tomorrow
I'll be just one day closer
One sunset further behind

[ladron121]

Cherenkov radiation (also spelled Cerenkov, scientific transliteration: Čerenkov) is electromagnetic radiation emitted when a charged particle passes through an insulator at a speed greater than the speed of light in that medium. The characteristic "blue glow" of nuclear reactors is due to Cherenkov radiation. It is named after Soviet scientist Pavel Alekseyevich Cherenkov, the 1958 Nobel Prize winner who was the first to rigorously characterize it.

While relativity holds that the speed of light in a vacuum is a universal constant (c), the speed of light in a material may be significantly less than c. For example, the speed of light in water is only 0.75c. Matter can be accelerated beyond this speed during nuclear reactions and in particle accelerators. Cherenkov radiation results when a charged particle, most commonly an electron, exceeds the speed of light in a dielectric (electrically insulating) medium through which it passes.

Moreover, the velocity of light that must be exceeded is the phase velocity rather than the group velocity. The phase velocity can be altered dramatically by employing a periodic medium, and in that case one can even achieve Cherenkov radiation with no minimum particle velocity — a phenomenon known as the Smith-Purcell effect. In a more complex periodic medium, such as a photonic crystal, one can also obtain a variety of other anomalous Cherenkov effects, such as radiation in a backwards direction (whereas ordinary Cherenkov radiation forms an acute angle with the particle velocity).

As a charged particle travels, it disrupts the local electromagnetic field (EM) in its medium. Electrons in the atoms of the medium will be displaced and polarized by the passing EM field of a charged particle. Photons are emitted as an insulator's electrons restore themselves to equilibrium after the disruption has passed. (In a conductor, the EM disruption can be restored without emitting a photon.) In normal circumstances, these photons destructively interfere with each other and no radiation is detected. However, when the disruption travels faster than the photons themselves travel, the photons constructively interfere and intensify the observed radiation.

A common analogy is the sonic boom of a supersonic aircraft or bullet. The sound waves generated by the supersonic body do not move fast enough to get out of the way of the body itself. Hence, the waves "stack up" and form a shock front. Similarly, a speed boat generates a large bow shock because it travels faster than waves can move on the surface of the water.

In the same way, a superluminal charged particle generates a photonic shockwave as it travels through an insulator.

In the figure, v is the velocity of the particle (red arrow), β; is v/c, n is the refractive index of the medium. The blue arrows are photons. So:\cos\theta=\frac1{n\beta}

Characteristics

Intuitively, the overall intensity of Cherenkov radiation is proportional to the velocity of the inciting charged particle and to the number of such particles. Unlike fluorescence or emission spectra that have characteristic spectral peaks, Cherenkov radiation is continuous. The relative intensity of one frequency is proportional to the frequency. That is, higher frequencies (shorter wavelengths) are more intense in Cherenkov radiation. This is why visible Cherenkov radiation is observed to be brilliant blue. In fact, most Cherenkov radiation is in the ultraviolet spectrum - it is only with sufficiently accelerated charges that it even becomes visible; the sensitivity of the human eye peaks at green, and is very low in the violet portion of the spectrum.

There is a cut-off frequency for which the equation above cannot be satisfied. Since the refractive index is a function of frequency (and hence wavelength), the intensity doesn't continue increasing at ever shorter wavelengths even for ultra-relativistic particles (where v/c approaches 1). At X-Ray frequencies, the refractive index becomes less than unity and hence no X-Ray emission (or shorter wavelength emissions such as gamma rays) would be observed. However, X-rays can be generated at special energies corresponding to core electronic transitions in a material, as the index of refraction is often greater than 1 at these energies.

As in sonic booms and bow shocks, the angle of the shock cone is inversely related to the velocity of the disruption. Hence, observed angles of incidence can be used to compute the direction and speed of a Cherenkov radiation-producing charge.

Uses

Nuclear reactors

Cherenkov radiation is used to detect high-energy charged particles. In pool-type nuclear reactors, the intensity of Cherenkov radiation is related to the frequency of the fission events that produce high-energy electrons, and hence is a measure of the intensity of the reaction. Cherenkov radiation is also used to characterize the remaining radioactivity of spent fuel rods.

Astrophysics experiments

When a high-energy cosmic ray interacts with the Earth's atmosphere, it may produce an electron-positron pair with enormous velocities. The Cherenkov radiation from these charged particles is used to determine the source and intensity of the cosmic ray, which is used for example in the Imaging Atmospheric Cherenkov Technique (IACT), by experiments such as VERITAS, H.E.S.S., and MAGIC. Similar methods are used in very large neutrino detectors, such as the Super-Kamiokande, the Sudbury Neutrino Observatory (SNO) and IceCube.

Cherenkov radiation can also be used to determine properties of high-energy astronomical objects that emit gamma rays, such as supernova remnants and blazars. This is done by projects such as STACEE, a gamma ray detector in New Mexico.

Particle physics experiments

Cherenkov radiation is commonly used in experimental particle physics for particle identification. One could measure (or put limits on) the velocity of an electrically charged elementary particle by the properties of the Cherenkov light it emits in a certain medium. If the momentum of the particle is measured independently, one could compute the mass of the particle by its momentum and velocity (see Four-momentum), and hence identify the particle.

The simplest type of particle identification device based on Cherenkov radiation technique is the threshold counter, which gives an answer on whether the velocity of a charged particle of lower or higher than a certain value by looking on whether this particle does or does not emit Cherenkov light in a certain medium. Knowing particle momentum, one can separate particles lighter than a certain threshold from those heavier that the threshold.

The most advanced type of a detector is the RICH, or Ring imaging Cherenkov detector, developed in 1980s. In a RICH detector a cone of Cherenkov light is produced when a high speed charged particle traverses a suitable gaseous medium, often called radiator. This light cone is detected on a position sensitive planar photon detector, which allows reconstructing a ring or disc, the radius of which is a measure for the Cherenkov emission angle. Both focusing and proximity-focusing detectors are in use. In a focusing RICH detector the photons are collected by a spherical mirror and focused onto the photon detector placed at the focal plane. The result is a circle with a radius independent of the emission point along the particle track. This scheme is suitable for low refractive index radiators, i.e. gases, due to the larger radiator length needed to create enough photons. In the more compact proximity-focusing design a thin radiator volume emits a cone of Cherenkov light which traverses a small distance – the proximity gap – and is detected on the photon detector plane. The image is a ring of light the radius of which is defined by the Cherenkov emission angle and the proximity gap. The ring thickness is determined by the thickness of the radiator. An example of a proximity gap RICH detector is the High Momentum Particle IDentification (HMPID), a detector currently under construction for ALICE (A Large Ion Collider Experiment), one of the six experiments at the LHC (Large Hadron Collider) at CERN.

[shifty]

Black holes are predictions of Albert Einstein's theory of general relativity. There are many known solutions to the Einstein field equations which describe black holes, and they are also thought to be an inevitable part of the evolution of any star of a certain size. In particular, they occur in the Schwarzschild metric, one of the earliest and simplest solutions to Einstein's equations, found by Karl Schwarzschild in 1915. This solution describes the curvature of spacetime in the vicinity of a static and spherically symmetric object, where the metric is,


where is a standard element of solid angle.

According to general relativity, a gravitating object will collapse into a black hole if its radius is smaller than a characteristic distance, known as the Schwarzschild radius. (Indeed, Buchdahl's theorem in general relativity shows that in the case of a perfect fluid model of a compact object, the true lower limit is somewhat larger than the Schwarzschild radius.) Below this radius, spacetime is so strongly curved that any light ray emitted in this region, regardless of the direction in which it is emitted, will travel towards the centre of the system. Because relativity forbids anything from traveling faster than light, anything below the Schwarzschild radius – including the constituent particles of the gravitating object – will collapse into the centre. A gravitational singularity, a region of theoretically infinite density, forms at this point. Because not even light can escape from within the Schwarzschild radius, a classical black hole would truly appear black.

The Schwarzschild radius is given by



where G is the gravitational constant, m is the mass of the object, and c is the speed of light. For an object with the mass of the Earth, the Schwarzschild radius is a mere 9 millimeters — about the size of a marble.

The mean density inside the Schwarzschild radius decreases as the mass of the black hole increases, so while an earth-mass black hole would have a density of 2 × 1030 kg/m3, a supermassive black hole of 109 solar masses has a density of around 20 kg/m3, less than water! The mean density is given by



Since the Earth has a mean radius of 6371 km, its volume would have to be reduced 4 × 1026 times to collapse into a black hole. For an object with the mass of the Sun, the Schwarzschild radius is approximately 3 km, much smaller than the Sun's current radius of about 696,000 km. It is also significantly smaller than the radius to which the Sun will ultimately shrink after exhausting its nuclear fuel, which is several thousand kilometers. More massive stars can collapse into black holes at the end of their lifetimes.

The formula also implies that any object with a given mean density is a black hole if its radius is large enough. The same formula applies for white holes as well. For example, if the visible universe has a mean density equal to the critical density, then it is a white hole, since its singularity is in the past and not in the future as should be for a black hole.

More general black holes are also predicted by other solutions to Einstein's equations, such as the Kerr metric for a rotating black hole, which possesses a ring singularity. Then we have the Reissner-Nordström metric for charged black holes. Last the Kerr-Newman metric is for the case of a charged and rotating black hole.

There is also the Black Hole Entropy formula:



Where A is the area of the event horizon of the black hole, \hbar is Dirac's constant (the "reduced Planck constant"), k is the Boltzmann constant, G is the gravitational constant, c is the speed of light and S is the entropy.

A convenient length scale to measure black hole processes is the "gravitational radius", which is equal to



When expressed in terms of this length scale, many phenomena appear at integer radii. For example, the radius of a Schwarzschild black hole is two gravitational radii and the radius of a maximally rotating Kerr black hole is one gravitational radius. The location of the light circularization radius around a Schwarzschild black hole (where light may orbit the hole in an unstable circular orbit) is 3rG. The location of the marginally stable orbit, thought to be close to the inner edge of an accretion disk, is at 6rG for a Schwarzschild black hole.