HEAPOW: Extremely High Energy Extragalactic... (2010 Aug 30)

[bystander]

HEAPOW: The Extremely High Energy Extragalactic Sky (2010 Aug 30)

Supermassive black holes (monsters with masses a billion times that of the sun crammed into a space smaller than the orbit of Neptune) at the nuclei of some galaxies produce some of the most amazing celestial fireworks we can observe. They feed on gas, dust, stars (and planets?) and they swallow immense amounts of matter while at the same time generating powerful particle beams shining through the Universe for millions of lightyears. The energies involved are enormous - and of course astronomers would like to know how enormous. Ground-based telescopes like the High Energy Stereoscopic System (HESS), the Very Energetic Radiation Imaging Telescope Array System (VERITAS) and the MAGIC telescope have helped probe the upper limit of the highest energy emission produced by supermassive accreting black holes in galactic nuclei. These telescopes use the atmosphere itself as a giant detector to determine the location of sources of ultra-high energy radiation. An ultra-high energy photon emitted by a supermassive black hole may travel for many millions of years through nearly empty space, finally hitting the earth's atmosphere. When this happens the photon explodes in a cascade of energetic charged particles. These charged particles actually move faster than light can move through the atmosphere, and as they do so they produce a bluish glow which can be detected by a large telescope. Telescopes like HESS, MAGIC and VERITAS can spot these blue flashes and correlate their positions with the positions of distant galaxies. The chart above shows the rapid recent growth in the number of galaxies which produce this ultra high energy radiation due to the increasing availability of ultra-high energy telescopes. The inset shows an artist's conception of a supermassive black hole, its accretion disk and the inner part of its jet of high energy particles.

Active Galactic Nuclei and gamma rays - B Giebels, F Aharonian, H Sol

• arXiv.org > astro-ph > arXiv:1005.2330 > 13 May 2010

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[Beyond]

HEAPOW: The Extremely High Energy Extragalactic Sky (2010 Aug 30)

... An ultra-high energy photon emitted by a supermassive black hole may travel for many millions of years through nearly empty space, finally hitting the earth's atmosphere. When this happens the photon explodes in a cascade of energetic charged particles. These charged particles actually move faster than light can move through the atmosphere, and as they do so they produce a bluish glow which can be detected by a large telescope. ...

See?? it is possible to travel faster than the speed of light. So there is still a glimmer of hope for Star Trek to become a reality - even if THAT glimmer can only be seen through something more powerful than an Electron microscope.

[bystander]

See?? it is possible to travel faster than the speed of light. So there is still a glimmer of hope for Star Trek to become a reality - even if THAT glimmer can only be seen through something more powerful than an Electron microscope.

These charged particles actually move faster than light can move through the atmosphere

[Chris Peterson]

See?? it is possible to travel faster than the speed of light. So there is still a glimmer of hope for Star Trek to become a reality - even if THAT glimmer can only be seen through something more powerful than an Electron microscope.

At the risk of sounding like a broken record: THERE IS NOTHING IN PHYSICS THAT SAYS SOMETHING CAN'T GO FASTER THAN LIGHT. What you cannot do is to convey information faster than c. Again, c is NOT the speed of light. It is a universal constant, and it happens that light travels at c in a vacuum.

In this case, the emitted particles are moving faster than the velocity of light in our atmosphere. When a charged particle moves through an insulating medium faster than the speed of light in that medium Cherenkov radiation is emitted. This is the familiar blue light seen coming from the water around small nuclear reactors.

[Beyond]

See?? it is possible to travel faster than the speed of light. So there is still a glimmer of hope for Star Trek to become a reality - even if THAT glimmer can only be seen through something more powerful than an Electron microscope.

At the risk of sounding like a broken record: THERE IS NOTHING IN PHYSICS THAT SAYS SOMETHING CAN'T GO FASTER THAN LIGHT. What you cannot do is to convey information faster than c. Again, c is NOT the speed of light. It is a universal constant, and it happens that light travels at c in a vacuum.

In this case, the emitted particles are moving faster than the velocity of light in our atmosphere. When a charged particle moves through an insulating medium faster than the speed of light in that medium Cherenkov radiation is emitted. This is the familiar blue light seen coming from the water around small nuclear reactors.

At the risk of sounding a bit dumb, are you saying that a charged particle can not transmit information at all, or just not when IT is going faster than c ?

[Chris Peterson]

At the risk of sounding a bit dumb, are you saying that a charged particle can not transmit information at all, or just not when IT is going faster than c ?

No particle, charged or otherwise, can go faster than c. So any particle that does transmit information will be going at or below c.

[Henning Makholm]

At the risk of sounding a bit dumb, are you saying that a charged particle can not transmit information at all, or just not when IT is going faster than c ?

No. He's saying that light sometimes goes slower than c.

Light in the atmosphere is one such example. It travels very slightly slower than c. This leaves room for information to be transmitted faster than light, yet still slower than c.

When the speed of light differs from c, the upper limit of information transfer is c, not lightspeed.

[Chris Peterson]

No. He's saying that light sometimes goes slower than c.

Good thing, too, or else none of our refractive optics would work. No binoculars or telescope lenses, no cameras, no fiber optics, no eyeglasses. The list is endless.

[Beyond]

At the risk of sounding a bit dumb, are you saying that a charged particle can not transmit information at all, or just not when IT is going faster than c ?

No. He's saying that light sometimes goes slower than c.

Light in the atmosphere is one such example. It travels very slightly slower than c. This leaves room for information to be transmitted faster than light, yet still slower than c.

When the speed of light differs from c, the upper limit of information transfer is c, not lightspeed.

Thanks! Now i got it!! The problem is trying to hold on to it. It's kinda like all that other "stuff" that one learns in school, if you never use it, it works it's way back into those deep dark recesses of the mind where you never go and sometimes even exceeds the depths of forgetfulness.

[neufer]

<<When light propagates through a material, it travels slower than the vacuum speed. This is a change in the phase velocity {} of the light and is manifested in physical effects such as refraction. This reduction in speed is quantified by the ratio between c and the phase velocity. This ratio is called the refractive index of the material.

Slow light is a dramatic reduction in the group velocity {} of light, not the phase velocity. Slow light effects are not due to abnormally large refractive indices. If the dispersion relation of the refractive index is such that the index changes rapidly over a small range of frequencies, then the group velocity might be very low, thousands or millions of times less than c, even though the index of refraction is still a typical value (between 1.5 and 3.5 for glasses and semiconductors).

Researchers at the Rowland Institute for Science slowed light to 38 miles per hour in 1999, and researchers at UC Berkeley slowed the speed of light traveling through a semiconductor to 21600 miles per hour in 2004. This was in an effort to develop computers that will use only a fraction of the energy of today's machines.

Slow light could be used to greatly reduce noise, which could allow all types of information to be transmitted more efficiently. Also, optical switches controlled by slow light could cut power requirements a million-fold compared to switches now operating everything from telephone equipment to supercomputers. Slowing light could lead to a more orderly traffic flow in networks. Meanwhile, slow light can be used to build interferometers that are far more sensitive to frequency shift as compared to conventional interferometers. This property can be used to build better, smaller frequency sensor and compact high resolution spectrometers.

Slow glass is a fictional material in Bob Shaw's novel Other Days, Other Eyes (1972). The glass, which delays the passage of light by years or decades, is used to construct windows, called scenedows, that enable city dwellers, submariners and prisoners to watch "live" countryside scenes. "Slow glass" is a material where the delay light takes in passing through the glass is attributed to photons passing "...through a spiral tunnel coiled outside the radius of capture of each atom in the glass.">>

[Guest]

See?? it is possible to travel faster than the speed of light. So there is still a glimmer of hope for Star Trek to become a reality - even if THAT glimmer can only be seen through something more powerful than an Electron microscope.

If you didn't know it, you could be forgiven for not understanding that The Speed Of Light can be slowed down, By numerous things. The Speed of Light is constant, In (empty {Vacuum} Space). But Light is not constant, it can be slowed down to zero. or close to. I wonder what else, out there, slows it down Huh? I am told Nothing. Funny how a transparent nothing, gravitationally superior, Dark Matter causes lensing. But don,t worry, it does not slow it down, I think.

tc

[bystander]

If you didn't know it, you could be forgiven for not understanding that The Speed Of Light can be slowed down, By numerous things. The Speed of Light is constant, In (empty {Vacuum} Space). But Light is not constant, it can be slowed down to zero. or close to. I wonder what else, out there, slows it down Huh? I am told Nothing. Funny how a transparent nothing, gravitationally superior, Dark Matter causes lensing. But don,t worry, it does not slow it down, I think.

c is constant and it happens to be the speed of electromagnetic radiation (light) in a vacuum. The speed of EMR in any other medium is slower than c (i.e. variable). The speed of light is not constant, c is.

[swainy (tc)]

If you didn't know it, you could be forgiven for not understanding that The Speed Of Light can be slowed down, By numerous things. The Speed of Light is constant, In (empty {Vacuum} Space). But Light is not constant, it can be slowed down to zero. or close to. I wonder what else, out there, slows it down Huh? I am told Nothing. Funny how a transparent nothing, gravitationally superior, Dark Matter causes lensing. But don,t worry, it does not slow it down, I think.

c is constant and it happens to be the speed of electromagnetic radiation (light) in a vacuum. The speed of EMR in any other medium is slower than c (i.e. variable). The speed of light is not constant, c is.

But Is The Medium Constant?

tc

[neufer]

c is constant and it happens to be the speed of electromagnetic radiation (light) in a vacuum. The speed of EMR in any other medium is slower than c (i.e. variable). The speed of light is not constant, c is.

But Is The Medium Constant?

It is if the Medium is water (n=1.33).

The nuclear reactor core of a Triga research reactor. Cherenkov radiation from the fuel rods is clearly visible. Ordinary water provides quite enough protection from the radiation of the core.

---

<<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. In the Pierre Auger Observatory and other similar projects tanks filled with water observe the Cherenkov radiation caused by muons, electrons and positrons of particle showers which are caused by cosmic rays.

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.>>

--------------------------------------------

PAC man

<<Pavel Alekseyevich Cherenkov (Павел Алексеевич Черенков, 1904–1990) was a Soviet physicist who shared the Nobel Prize in physics in 1958 with Ilya Frank and Igor Tamm for the discovery of Cherenkov radiation made in 1934. He graduated from the Department of Physics and Mathematics of Voronezh State University in 1928, in 1930 he took a post as a senior researcher in the Lebedev Institute of Physics. That same year he married Maria Putintseva, daughter of A.M. Putintsev, a Professor of Russian Literature.

In 1934, while working under S.I. Vavilov, Cherenkov observed the emission of blue light from a bottle of water subjected to radioactive bombardment. This phenomenon, associated with charged atomic particles moving at velocities greater than the speed of light in the local medium, proved to be of great importance in subsequent experimental work in nuclear physics, and for the study of cosmic rays. Eponymously, it was dubbed the Cherenkov effect, as was the Cherenkov detector, which has become a standard piece of equipment in atomic research for observing the existence and velocity of high-speed particles. The device was installed in Sputnik 3. Pavel Cherenkov also shared in the development and construction of electron accelerators and in the investigations of photo-nuclear and photo-meson reactions.>>

[bystander]

But Is The Medium Constant?

Does it matter? If the medium changes, the speed of the EMR moving through it changes.

[swainy (tc)]

But Is The Medium Constant?

Does it matter? If the medium changes, the speed of the EMR moving through it changes.

How? Does not really Matter, Any medium densities, in the whole universe, From Gas, To Dark matter, There is A lot of miles to explore, (Never) We can,t. really can,t be sure can we ? You tell me.

tc

[geckzilla]

Swain, I don't think you really understand how to communicate with English as a written language. How can you ever expect to understand relatively complex concepts if your language comprehension is impaired?

[neufer]

Swain, I don't think you really understand how to communicate with English as a written language.

Tokelau Islands with Swains Island to the south.

---

<<Swains Island is the 4^th & smallest island in the Tokelau chain (along with Fakaofo, Nukunonu & Atafu atolls). Swains Is. is an unincorporated unorganized territory of the United States administered by American Samoa. Owned by the Jennings family and used as a copra plantation, Swains Island has a population of 37 Tokelauans, all located in the village of Taulaga on the island's west side, who harvest the island's coconuts. Swains' village council consists of all men of sound mind over the age of twenty-four( but only five men fall into this category). In February 2005, Cyclone Percy struck the island, causing widespread damage and virtually destroying the village of Taulaga, as well as the old Jennings estate. Fortunately, only seven people were on the island at the time.

The atoll is somewhat unusual, featuring an unbroken circle of land enclosing a freshwater lagoon cut off from the sea. Recent U.S. Coast Guard visitors to Swains described its lagoon as "brackish" and a source for the plentiful numbers of mosquitoes which plague the island. In April 2007, a member of an amateur radio expedition confirmed that the lagoon water was fit only for bathing and washing, and that fresh water seemed to be in rather short supply on the island at the time. (Due to its remoteness, Swains Island is considered a separate amateur radio "entity" and several visits have been made by ham operators.) According to a United States Department of the Interior description of Swains Island, drinking water on Swains is derived entirely from rainfall collected in two large mahogany tanks near the island's copra shed.

Pedro Fernandes de Queirós, a Portuguese navigator sailing for Spain, is believed to have been the first European explorer to have discovered Swains Island on 2 March 1606. Later, there was an expedition from Fakaofo to the island. The male inhabitants of the island either fled or were killed by the invaders, while the women were taken back to Fakaofo. The subsequent infertility of the island, attributed to a curse placed on it by its last chief, led to the failure of the Fakaofoan settlement there. Captain William L. Hudson of the American ship Peacock visited the atoll in 1841, at the request of Commodore Charles Wilkes, but was unable to land due to stormy weather. Finding the island was not at the position reported by de Queirós, Hudson concluded that the whaling captain W.C. Swains who had alerted them to the island had discovered it, and he renamed it "Swains Island">>

-----------------------------------------------------------

• ____ King Henry VI, Part iii Act 2, Scene 5
  
  KING HENRY VI: Here on this molehill will I sit me down.
  . O God! methinks it were a happy life,
  . To be no better than a homely swain;
  . To sit upon a hill, as I do now,
  . To carve out dials quaintly, point by point,
  . Thereby to see the minutes how they run,
  . How many make the hour full complete;
  . How many hours bring about the day;
  . How many days will finish up the year;
  . How many years a mortal man may live.

[Beyond]

Swainy, perhaps this will help.
C represents the maximum speed of light in the low density of space. It is the fastest speed that light travels that man knows of. That's why it is called c.
Any other medium that light travels through slows it down so that light is now traveling slower than its fastest possible speed - c. That means that it is possible to travel faster than light when light is traveling slower than it's fastest possible speed, but at the same time it is not possible to travel faster than the fastest speed of light which is - c.

It sounds impossible to be able to travel faster than the speed of light with out going faster than the speed of light unless you understand that you are dealing with 2 different refferences. c - being the fastest possible speed of light and the actual slowed down speed of light that happens when light goes through a denser medium than space.

Sometimes when WE are being "dense" headed and light hits us and gets slowed down to almost a stop, that is referred to as being "dim-witted."
Don't ask me how i know that

[bystander]

How? Does not really Matter, Any medium densities, in the whole universe, From Gas, To Dark matter, There is A lot of miles to explore, (Never) We can,t. really can,t be sure can we ? You tell me.

'Slow light' on a chip holds promise for optical communications
PhysOrg | Optics & Photonics | 05 Sept 2010

A tiny optical device built into a silicon chip has achieved the slowest light propagation on a chip to date, reducing the speed of light by a factor of 1,200 in a study reported in Nature Photonics (published online September 5 and in the November print issue).

Slow light on a chip via atomic quantum state control - Bin Wu et al

• Nature Photonics (online 05 Sept 2010) DOI: 10.1038/nphoton.2010.211

[neufer]

C represents the maximum speed of light in the low density of space.
It is the fastest speed that light travels that man knows of. That's why it is called c.

Why is c the symbol for the speed of light?

"As for c, that is the speed of light in vacuum, and if you ask why c,
the answer is that it is the initial letter of celeritas, the Latin word meaning speed."
- Isaac Asimov in "C for Celeritas (1959)"

Celerity, n. [L. celeritas, from celer swiftm speedy:
sf. F. célérité.] Rapidity of motion; quickness; swiftness.

"Time, with all its celerity, moves slowly to him
whose whole employment is to watch its flight." - Johnson.

<<Although c is now the universal symbol for the speed of light, the most common symbol in the nineteenth century was an upper-case V which Maxwell had started using in 1865. That was the notation adopted by Einstein for his first few papers on relativity from 1905. The origins of the letter c being used for the speed of light can be traced back to a paper of 1856 by Weber and Kohlrausch. They defined and measured a quantity denoted by c that they used in an electrodynamics force law equation. It became known as Weber's constant and was later shown to have a theoretical value equal to the speed of light times the square root of two. In 1894 Paul Drude modified the usage of Weber's constant so that the letter c became the symbol for the speed of electrodynamic waves. In optics Drude continued to follow Maxwell in using an upper-case V for the speed of light. Progressively the c notation was used for the speed of light in all contexts as it was picked up by Max Planck, Hendrik Lorentz and other influential physicists. By 1907 when Einstein switched from V to c in his papers, it had become the standard symbol for the speed of light in vacuum for electrodynamics, optics, thermodynamics and relativity.

Weber apparently meant c to stand for "constant" in his force law, but there is evidence that physicists such as Lorentz and Einstein were accustomed to a common convention that c could be used as a variable for velocity. This usage can be traced back to the classic Latin texts in which c stood for "celeritas" meaning "speed". The uncommon English word "celerity" is still used when referring to the speed of wave propagation in fluids. The same Latin root is found in more familiar words such as acceleration.

Although the c symbol was adapted from Weber's constant, it was probably thought appropriate for it to represent the velocity of light later on because of this Latin interpretation. So history provides an ambiguous answer to the question "Why is c the symbol for the speed of light?", and it is reasonable to think of c as standing for either "constant" or "celeritas".>>

• --------------------------------------------
  
  
  . King Henry V Act 3, Prologue
  
  Chorus: Thus with imagined wing our swift scene flies
  . In motion of no less *CELERITY*
  . Than that of thought.
  
  . Troilus and Cressida Act 1, Scene 3
  
  NESTOR: And, in the publication, make no strain,
  . But that Achilles, were his brain as barren
  . As banks of Libya,--though, Apollo knows,
  . 'Tis dry enough,--will, with great speed of judgment,
  . Ay, with *CELERITY*, find Hector's purpose
  . Pointing on him.
  .............................................
  . Measure for Measure Act 4, Scene 2
  
  DUKE VINCENTIO: This is his pardon, purchased by such sin
  . For which the pardoner himself is in.
  . Hence hath offence his quick *CELERITY*,
  . When it is born in high authority:
  . When vice makes mercy, mercy's so extended,
  . That for the fault's love is the offender friended.
  . Now, sir, what news?
  
  . Act 5, Scene 1
  
  DUKE VINCENTIO: And you may marvel why I obscured myself,
  . Labouring to save his life, and would not rather
  . Make rash remonstrance of my hidden power
  . Than let him so be lost. O most kind maid,
  . It was the swift *CELERITY* of his death,
  . Which I did think with slower foot came on,
  . That brain'd my purpose.
  .............................................
  . Antony and Cleopatra Act 1, Scene 2
  
  DOMITIUS ENOBARBUS: I do think there is
  . mettle in death, which commits some loving act upon
  . her, she hath such a *CELERITY* in dying.
  
  . Act 3, Scene 7
  
  CLEOPATRA. *CELERITY* is never more admired
  . Than by the negligent.
  --------------------------------------------

[Beyond]

The celerity of going off topic in these forums is only exceded by the celerity of the postings of the afore-mentioned celerics.

[swainy (tc)]

http://asterisk.apod.com/vie ... 96#p131396


Nice try, Beyond. No Byte. Huh . 2.9 billion, @ Light speed Huh? Just another 11 billion Light years of Unknown space/time, to go I Guess. Like You said, must be my physical density , Not the Universe.

tc

[swainy (tc)]

Swain, I don't think you really understand how to communicate with English as a written language. How can you ever expect to understand relatively complex concepts if your language comprehension is impaired?

I would answer that if, my impaired comprehension In the complexity of the English language. Did not fool me into believing, that you said something, that my impaired comprehension, was that complex, that I, may not understand my own answer. In the understanding, that at some point I May have problems understanding My Own complex impaired comprehension, of My very complex brilliant answer. I Must however decline, On the principle I may spout something that nobody understands. And there, we are back where we started.



tc

[Beyond]

http://asterisk.apod.com/vie ... 31&t=20879


Nice try, Beyond. No Byte. Huh . 2.9 billion, @ Light speed Huh? Just another 11 billion Light years of Unknown space/time, to go I Guess. Like You said, must be my physical density , Not the Universe.

tc

Sorry, swainy, i just don't get it. I might just be having one of those dense as a rock moments, cause what you just said escapes me, except that i remember in one of my posts somewhere i said something like "we can all be a little dense at times." But i do not remember pointing my short stubby finger at you and singling you out as being dense.