Possible to be exposed to Radiation from the Sun and Cosmic Rays

   University of California Berkeley    1.   

   A new study suggests that Earth’s magnetic field could take just 100 years to flip - and there’s evidence it could happen again in a couple of thousand years.

   We think of north and south as being pretty constant, but the Earth’s magnetic field has flipped many times throughout the planet’s history, generally without causing huge catastrophes.

   The Earth’s magnetic field is dipole, like that of a magnet, which means it has two opposite poles. Usually this magnetic field maintains the same intensity for thousands to million of years, but for unknown reasons, it occasionally weakens and reverses direction, a process that scientists previously thought took thousands of years.

   But now scientists have discovered that the last magnetic reversal happened 786,000 years ago, and it actually occurred very quickly, within around 100 years. This means north and south could swap positions in the span of a human lifetime, which is pretty crazy to think about.

   The international study was led by scientists at the University of California Berkeley in the US, and examined sediment layers in an ancient lake in the Sulmona basin east of Rome, Italy. The results are published in Geophysical Journal International.

   “It’s amazing how rapidly we see that reversal,” said Courtney Sprain, a University of California Berkeley graduate student, who co-authored the study, in a press release. 
   “The paleomagnetic data are very well done. This is one of the best records we have so far of what happens during a reversal and how quickly these reversals can happen.”

   The sediment that the team studied was deposited over a 10,000-year period by volcanic eruptions in the region. The magnetic field direction at the time affected how the ash settled at the bottom of the ancient lake, which means that the scientists have a clear record of which way north and south were pointing, and when things changed.

   The results show that not only did the flip occur a lot quicker than we previously thought, it was also preceded by a period of magnetic instability that lasted around 6,000 years.

   “What’s incredible is that you go from reverse polarity to a field that is normal with essentially nothing in between, which means it had to have happened very quickly, probably in less than 100 years,” said Paul Renne, co-author of the study, in a press release. 
  “We don’t know whether the next reversal will occur as suddenly as this one did, but we also don’t know that it won’t.”

   It’s an important breakthrough, because new evidence suggests the Earth’s magnetic field is currently decreasing 10 times faster than normal, leading some geophysicists to predict a flip of north and south within a few thousands years.

   That’s not necessarily as bad as it sounds - there are no documented catastrophes associated with past reversals. But there would be some major issues - for starters, the pole flip could wreak havoc on our electrical grid, and could possibly even take it down altogether.

   And because the Earth’s magnetic field protects us from radiation from the Sun and cosmic rays, the reduction of the magnetic field before the reversal could lead to increased rates of cancer.

   The danger would be even greater if the flip was preceded by long periods of unstable magnetic behaviour - which occurred in the latest pole flip. The truth is, however, we know very little about what the effect of a pole reversal would be, but it's time we started to find out, and this new data will help us better understand the process.

“We should be thinking more about what the biologic effects would be,” said Renne.
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Source:

   University of California Berkeley    2

   Imagine the world waking up one morning to discover that all compasses
   pointed south instead of north.

   It’s not as bizarre as it sounds. Earth’s magnetic field has flipped – though not overnight – many times throughout the planet’s history. Its dipole magnetic field, like that of a bar magnet, remains about the same intensity for thousands to millions of years, but for incompletely known reasons it occasionally weakens and, presumably over a few thousand years, reverses direction.

   Now, a new study by a team of scientists from Italy, France, Columbia University and the University of California, Berkeley, demonstrates that the last magnetic reversal 786,000 years ago actually happened very quickly, in less than 100 years – roughly a human lifetime.

   “It’s amazing how rapidly we see that reversal,” said UC Berkeley graduate student Courtney Sprain. “The paleomagnetic data are very well done. This is one of the best records we have so far of what happens during a reversal and how quickly these reversals can happen.”

   Sprain and Paul Renne, director of the Berkeley Geochronology Center and a UC Berkeley professor-in- residence of earth and planetary science, are coauthors of the study, which will be published in the November issue of Geophysical Journal International and is now available online.

   Flip could affect electrical grid, cancer rates

   The discovery comes as new evidence indicates that the intensity of Earth’s magnetic field is decreasing 10 times faster than normal, leading some geophysicists to predict a reversal within a few thousand years.

   Though a magnetic reversal is a major planet-wide event driven by convection in Earth’s iron core, there are no documented catastrophes associated with past reversals, despite much searching in the geologic and biologic record. Today, however, such a reversal could potentially wreak havoc with our electrical grid, generating currents that might take it down.

   And since Earth’s magnetic field protects life from energetic particles from the sun and cosmic rays, both of which can cause genetic mutations, a weakening or temporary loss of the field before a permanent reversal could increase cancer rates. The danger to life would be even greater if flips were preceded by long periods of unstable magnetic behavior.

   “We should be thinking more about what the biologic effects would be,” Renne said.

Dating ash deposits from windward volcanoes

   The new finding is based on measurements of the magnetic field alignment in layers of ancient lake sediments now exposed in the Sulmona basin of the Apennine Mountains east of Rome, Italy. The lake sediments are interbedded with ash layers erupted from the Roman volcanic province, a large area of volcanoes upwind of the former lake that includes periodically erupting volcanoes near Sabatini, Vesuvius and the Alban Hills.

   Italian researchers led by Leonardo Sagnotti of Rome’s National Institute of Geophysics and Volcanology measured the magnetic field directions frozen into the sediments as they accumulated at the bottom of the ancient lake.

   Sprain and Renne used argon-argon dating, a method widely used to determine the ages of rocks, whether they’re thousands or billions of years old, to determine the age of ash layers above and below the sediment layer recording the last reversal. These dates were confirmed by their colleague and former UC Berkeley postdoctoral fellow Sebastien Nomade of the Laboratory of Environmental and Climate Sciences in Gif-Sur-Yvette, France.

   Because the lake sediments were deposited at a high and steady rate over a 10,000-year period, the team was able to interpolate the date of the layer showing the magnetic reversal, called the Matuyama-Brunhes transition, at approximately 786,000 years ago. This date is far more precise than that from previous studies, which placed the reversal between 770,000 and 795,000 years ago.

The ‘north pole’ — that is, the direction of magnetic north — was reversed
a million years ago. This map shows how, starting about 789,000 years ago,
the north pole wandered around Antarctica for several thousand years
before flipping 786,000 years ago to the orientation we know today,
with the pole somewhere in the Arctic.

   “What’s incredible is that you go from reverse polarity to a field that is normal with essentially nothing in between, which means it had to have happened very quickly, probably in less than 100 years,” said Renne. “We don’t know whether the next reversal will occur as suddenly as this one did, but we also don’t know that it won’t.”

    Unstable magnetic field preceded 180-degree flip

  Whether or not the new finding spells trouble for modern civilization, it likely will help researchers understand how and why Earth’s magnetic field episodically reverses polarity, Renne said.

Left to right, Biaggio Giaccio, Gianluca Sotilli,
Courtney Sprain and Sebastien Nomade sitting next to
an outcrop in the Sulmona basin of the Apennine Mountains
that contains the Matuyama-Brunhes magnetic reversal.
A layer of volcanic ash interbedded with the lake sediments
can be seen above their heads. Sotilli and Sprain are pointing
to the sediment layer in which the magnetic reversal occurred.
(Photo by Paul Renne)

   The magnetic record the Italian-led team obtained shows that the sudden 180-degree flip of the field was preceded by a period of instability that spanned more than 6,000 years. The instability included two intervals of low magnetic field strength that lasted about 2,000 years each. Rapid changes in field orientations may have occurred within the first interval of low strength. The full magnetic polarity reversal – that is, the final and very rapid flip to what the field is today – happened toward the end of the most recent interval of low field strength.

   Renne is continuing his collaboration with the Italian-French team to correlate the lake record with past climate change.

    Renne and Sprain’s work at the Berkeley Geochronology Center was supported by the Ann and Gordon Getty Foundation.

______________________________________  No 35

source

   i s o s. . .  

Xenophon, 10.000 Greeks in Mesopotamia withou supplies

                                                      

   Anabasis - Katabasis 
One of the great adventures in human history.

    This story recounts the conflict between the two Persian brothers on the claim the throne of the powerful at that time Persian Empire and the adventures of ten thousand Greek mercenaries who fought on the side of Cyrus, the younger brother of two.

   When Cyrus was killed in a battle, the bulk of its army, which consisted of Persian soldiers, joined the army of his brother and together the two armies attacked the Greeks.
   Xenophon was a junior officer who assumed command of Greek warriors after the death of their leaders and fighting continuously succeeded in returning home.

Route of  Cyrus,  Xenophon and the Ten Thousand.

Anabasis  (Xenophon)

    Anabasis ("An Ascent"/"Going Up") is the most famous work, in seven books, of the Greek professional soldier and writer Xenophon.
   The journey it narrates is his best known accomplishment and "one of the great adventures in human history," as Will Durant expressed the common assessment.
   Xenophon accompanied the Ten Thousand, a large army of Greek mercenaries hired by Cyrus the Younger, who intended to seize the throne of Persia from his brother, Artaxerxes II.
   Though Cyrus' mixed army fought to a tactical victory at Cunaxa in Babylon (401 BC), Cyrus himself was killed in the battle, rendering the actions of the Greeks irrelevant and the expedition a failure.

   Stranded deep in enemy territory, the Spartan general Clearchus and the other Greek senior officers were subsequently killed or captured by treachery on the part of the Persian satrap Tissaphernes. 
   Xenophon, one of three remaining leaders elected by the soldiers, played an instrumental role in encouraging the Greek army of 10,000 to march north across foodless deserts and snow-filled mountain passes towards the Black Sea and the comparative security of its Greek shoreline cities. 

   Now abandoned in northern Mesopotamia, without supplies other than what they could obtain by force or diplomacy, the 10,000 had to fight their way northwards through Corduene and Armenia, making ad hoc decisions about their leadership, tactics, provender and destiny, while the King's army and hostile natives constantly barred their way and attacked their flanks.
   Ultimately this "marching republic" managed to reach the shores of the Black Sea at Trabzon (Trebizond), a destination they greeted with their famous cry of joyous exultation on the mountain of Theches (now Madur) in Surmene : "thálatta, thálatta", "the sea, the sea!".
   "The sea" meant that they were at last among Greek cities, but it was not the end of their journey, which included a period fighting for Seuthes II of Thrace, and ended with their recruitment into the army of the Spartan general Thibron. Xenophon related this story in Anabasis in a simple and direct manner.

Route of Cyrus the Younger, 

Xenophon and the Ten Thousand.

    The Greek term anabasis referred to an expedition from a coastline into the interior of a country. The term katabasis referred to a trip from the interior to the coast. 
   While the journey of Cyrus himself is indeed an anabasis from Ionia on the eastern coast of the Aegean Sea to the interior of Asia Minor and Mesopotamia, most of Xenophon's narrative is taken up with the return march of Xenophon and the Ten Thousand from the interior of Babylon to the coast of the Black Sea.

   Socrates makes a cameo appearance when Xenophon asks whether he ought to accompany the expedition. 
   The short episode demonstrates the reverence of Socrates for the Oracle of Delphi.

   Xenophon's account of the exploit resounded through Greece, where, two generations later, some surmise, it may have inspired Philip of Macedon to believe that a lean and disciplined Hellene army might be relied upon to defeat a Persian army many times its size.

   Besides military history, the Anabasis has found use as a tool for the teaching of classical philosophy; the principles of leadership and government exhibited by the army can be seen as exemplifying Socratic philosophy.

   Traditionally Anabasis is one of the first unabridged texts studied by students of classical Greek because of its clear and unadorned style; similar to Caesar's Commentarii de Bello Gallico for Latin students. 
   Perhaps not coincidentally, they are both autobiographical tales of military adventure told in the third person.
   Xenophon's book inspired Anabasis Alexandri, by the Greek historian Arrian (86 – after 146 AD), about Alexander the Great (336–323 BC)

   The cry of Xenophon's soldiers when they meet the sea is mentioned by the narrator of Jules Verne's Journey to the Center of the Earth, when their expedition discovers an underground ocean.
   The famous cry provides the title of the Booker Prize-winning novel by Iris Murdoch, The Sea, the Sea.
   The cry of Xenophon's soldiers is mentioned by Buck Mulligan in James Joyce's novel Ulysses, "Ah, Dedalus, the Greeks!  
   I must teach you. You must read them in the original. Thalatta! Thalatta! She is our great sweet mother."
   Andre Norton's 1955 science fiction novel Star Guard appears to have been the first speculative fiction transliteration of the Anabasis theme, in which a body of human mercenaries hired out of a future Terra to fight in a dynastic war among autochthons on a distant planet are betrayed in much the same way as were the Hellenic mercenaries of Xenophon's account, and left leaderless to negotiate and battle their way across hostile country to safety.
   Themes from the Anabasis were used in Sol Yurick's novel The Warriors, which was later adapted into a 1979 cult movie of the same name, and finally a Rockstar Games video game in 2005.   Each re-imagining relocates Xenophon's narrative to the gang scene of New York.

   Paul Davies' novella Grace: 
   A Story (Toronto: ECW Press, 1996) is a fantasy that details the progress of Xenophon's army through Armenia to Trabzon.

Michael Curtis Ford's 2001 novel The Ten Thousand is a fictional account of this group's exploits.

Harold Coyle's 1993 novel The Ten Thousand shows the bulk of the US Forces in modern Europe fighting their way across and out of Germany, instead of laying down their weapons, after the Germans steal nuclear weapons that are being removed from Ukraine. The operational concept for the novel was based on Xenophon's account of the Ten Thousand.

   The 1996 David Drake novel The Forlorn Hope draws on the March of the Ten Thousand for its inspiration, as well as the 1996 novel Redliners, though the enemy of the second novel is an adaptive jungle environment somewhat derivative of Harry Harrison's Deathworld stories.

   Shane Brennan's In the Tracks of the Ten Thousand: A Journey on Foot through Turkey, Syria and Iraq (London: Robert Hale, 2005) is an account of his 2000 journey to re-trace the steps of the Ten Thousand.
   Paul Kearney's 2008 novel The Ten Thousand is directly based on the historical events but transplants the action to a fictional fantasy world named Kuf, where ten thousand Macht mercenaries are hired to fight on the behalf of a prince trying to usurp the throne of the Assurian Empire. When he dies in battle, the Macht have to march home overland through hostile territory.
   Valerio Massimo Manfredi's 2008 novel "The Lost Army" is a fictional account of Xenophon's march with the Ten Thousand.
   John Ringo's 2008 novel "The Last Centurion" involves a similar anabasis from the Persian Gulf to the Black Sea, by US Army troops abandoned in Iran during a global catastrophe.
   John Ringo and David Weber's "March Upcountry" series is a military SF story involving the march of a prince and his bodyguards across a hostile planet in order to return to their home world.
   The 2005 Parkway Drive song "Anasasis (Xenophontis)", from the album Killing with a Smile, is a reference to the Anabasis text.
   The 2006 Military science fiction series The Lost Fleet, by John G. Hemry (writing as Jack Campbell) combines the structure of the Anabasis with the myth of the King in the mountain. 
   In the series, a space fleet is led home by a commander retrieved from hibernation, a hundred years after a battle that made him a revered historical and mythical figure.
   In 2011 Eric Baudelaire made an installation with 66 minutes of film and 9 screenprints for the MACBA in Bacelona and published the text to go with them with the title "The ANABASIS of May and Fusako Shigenobu, Masao Adachi, and 27 years without images"
   T.E. Lawrence (Lawrence of Arabia) was said to have read Anabasis during the 1916 Arab Revolt and that it influenced both his leadership during that time and his writing of The Seven Pillars of Wisdom.

______________     No 34 

  ISOS... 

The Roman Empire or Rome... fell at 476 A.D

 

Rome 476 A.D 

The historians wrote many years later: 

In the late fourth century, the Roman Empire crumbled after a nearly 500-year run as the world’s greatest superpower.

Historians have blamed the collapse on hundreds of different factors ranging from military failures and crippling taxation to natural disasters and even climate change. 

Still others argue that the Roman Empire didn’t really fall in 476 A.D., since its eastern half continued for another thousand years in the form of the Byzantine Empire. While just how—and when—the Empire fell remains a subject of ongoing debate, certain theories have emerged as the most popular explanations for Western Rome’s decline and disintegration. Read on to discover eight reasons why one of history’s most legendary empires finally came crashing down.

Hiding Objects

A multidirectional `perfect paraxial’ cloak using four lenses. From a continuous range of viewing angles, the hand remains cloaked, and the grids seen through the device match the background on the wall (about 2 m away), in color, spacing, shifts, and magnification. // photo by J. Adam Fenster / University of Rochester

‘Cloaking’ device uses ordinary lenses 
to hide objects across range of angles

Inspired perhaps by Harry Potter’s invisibility cloak, scientists have recently developed several ways—some simple and some involving new technologies—to hide objects from view. The latest effort, developed at the University of Rochester, not only overcomes some of the limitations of previous devices, but it uses inexpensive, readily available materials in a novel configuration.

Doctoral student Joseph Choi is pictured
with a a multidirectional `perfect paraxial’
cloak using 4 lenses.

In order to both cloak an object and leave the background undisturbed, the researchers determined the lens type and power needed, as well as the precise distance to separate the four lenses.

To test their device, they placed the cloaked object in front of a grid background.

As they looked through the lenses and changed their viewing angle by moving from side to side, the grid shifted accordingly as if the cloaking device was not there.

There was no discontinuity in the grid lines behind the cloaked object, compared to the background, and the grid sizes (magnification) matched.

The Rochester Cloak can be scaled up as large as the size of the lenses, allowing fairly large objects to be cloaked. And, unlike some other devices, it’s broadband so it works for the whole visible spectrum of light, rather than only for specific frequencies.

Their simple configuration improves on other cloaking devices, but it’s not perfect. “This cloak bends light and sends it through the center of the device, so the on-axis region cannot be blocked or cloaked,” said Choi. This means that the cloaked region is shaped like a doughnut. He added that they have slightly more complicated designs that solve the problem. Also, the cloak has edge effects, but these can be reduced when sufficiently large lenses are used.

In a new paper submitted to the journal Optics Express and available on arXiv.org, Howell and Choi provide a mathematical formalism for this type of cloaking that can work for angles up to 15 degrees, or more. They use a technique called ABCD matrices that describes how light bends when going through lenses, mirrors, or other optical elements.

While their device is not quite like Harry Potter’s invisibility cloak, Howell had some thoughts about potential applications, including using cloaking to effectively let a surgeon “look through his hands to what he is actually operating on,” he said. The same principles could be applied to a truck to allow drivers to see through blind spots on their vehicles.

Howell became interested in creating simple cloaking devices with off-the-shelf materials while working on a holiday project with his children. Together with his 14 year-old son and Choi, he recently published a paper about some of the possibilities, and also demonstrated simple cloaking with mirrors, like magicians would use, in a brief video.
To build your own Rochester Cloak, follow these simple steps:

For their demonstration cloak,
the researchers used 50mm achromatic doublets with focal lengths f1 = 200mm and f2 = 75mm

Purchase 2 sets of 2 lenses with different focal lengths f1 and f2 (4 lenses total, 2 with f1 focal length, and 2 with f2 focal length)
Separate the first 2 lenses by the sum of their focal lengths (So f1 lens is the first lens, f2 is the 2nd lens, and they are separated by t1= f1+ f2).
Do the same in Step 2 for the other two lenses.
Separate the two sets by t2=2 f2 (f1+ f2) / (f1— f2) apart, so that the two f2 lenses are t2 apart.


NOTES:
Achromatic lenses provide best image quality.
Fresnel lenses can be used to reduce the total length (2t1+t2)
Smaller total length should reduce edge effects and increase the range of angles.
For an easier, but less ideal, cloak, you can try the 3 lens cloak in the paper.

Setup of the multidirectional `perfect paraxial’ cloak as seen from the side. Laser shows the paths that light rays travel through the system, showing regions that can be used for cloaking an object. // photo by J. Adam Fenster / University of Rochester
Tags: featured-post, Institute of Optics, John Howell, research finding, School of Arts and Sciences
Category: Featured

___________________     No 32

Contact Author(s)

David Barnstone

585.276.6264

 dbarnsto@ur.rochester.edu

  i s o s . . .