THE LATEST FROM SPACE SCIENCE AND RESEARCH (A)

A)Ames Team to Use Robots, Humans to Study Impact Sites and Volcanoes Selected to Join New Virtual Research Institute

One day, human activity will extend across the solar system. Scientists believe this will  expand our understanding of Earth and the universe in which we live. A team of researchers, led by NASA’s Ames Research Center in Moffett Field, Calif., seeks to study what volcanoes and impact sites on Earth can tell us about the early evolution of the solar system and unique characteristics and features of our moon, the moons of Mars and asteroids.

The Ames project dubbed “FINESSE,” which stands for Field Investigations to Enable Solar System Science and Exploration, was selected to join a new NASA virtual institute that will focus on questions concerning space science and human space exploration. The team was selected to participate by NASA’s Solar System Exploration Research Virtual Institute (SSERVI), which is based at Ames.

FINESSE will study the formation of volcanoes, evolution of magma chambers, and the mechanics and chronology of cratering from impacts, as well as the evolution and entrapment of volatile chemicals. The team also will find samples on Earth to study the geology and chemistry of sites that have melted due to impacts.

“The goal of our research is to gain knowledge and prepare for the strategic human and robotic exploration of our moon, the moons of Mars and near-Earth asteroids,” said Jennifer Heldmann, principal investigator of the FINESSE project at Ames. “Our science program is infused with leading edge exploration concepts to help us better understand the effects of volcanism and impacts as dominant planetary processes on these bodies, and to understand which exploration concepts of operations and capabilities enable and enhance science findings.”

The philosophy behind the creation of SSERVI is that science and exploration complement each other. The late Mike Wargo, formerly NASA’s chief exploration scientist, succinctly captured the essence of the Institute saying, “Exploration enables science, and science enables exploration.”

The FINESSE team, composed of a world-class team of astronauts, scientists, and operations, robotics and exploration experts, will perform science-driven field exploration at two strategically chosen field sites. The team will simluate both robotic and human exploration missions at the Craters of the Moon National Monument and Preserve in Idaho and at the West Clearwater Lake Impact Structure in northern Canada.

Craters of the Moon lava field is a striking area of recent volcanic activity within Idaho’s Snake River Plain.

Image Credit: NASA Earth Observatory image by Robert Simmon

“These sites have been chosen to address scientific questions pertaining to volcanism and impact science, respectively, and are geologic analogs to other bodies in our solar system,” said Darlene Lim, deputy principal investigator of the FINESSE team at Ames and the SETI Institute in Mountain View, Calif. “These volcanic and impact records are a valuable source of first-hand knowledge about volcanic landform formation and modification, as well as the structure and character of impact craters, and can better our understanding of these processes throughout our solar system.”

For example, the formation of craters from impacts by meteoroids, referred to as “impact cratering,” is the dominant geological process on the moon, asteroids and moons of Mars. By understanding the origin and location of impact sites, the history of impact bombardment in the inner solar system, the formation of complex impact craters, and the effects of shock on planetary materials, we can understand the processes that shape the moon, asteroids and moons of Mars.

Volcanism is another geologic process that has significantly shaped the surface of planetary bodies. The team will study the processes, features and rock types related to volcanic eruptions, as well as the formation of volcanoes, lava tubes and flows and deposits of volcanic rocks.

Once in the field, the team will simulate work with the same mission contraints as if they were on the surface of our moon, an asteroid or the moons of Mars. One way to simulate the complexities of missions on other planetary bodies is to build in actual latencies and constraints for communications and bandwidth between a crew on the moon, an asteroid and ground control on Earth.

“These mission constraints help us evaluate strategically selected concepts of operations and capabilities with respect to their anticipated value for future human-robotic scientific exploration,” said Heldmann. “Specifically, understanding the robustness of our communications and planning capabilities is key to understanding how to maximize science return while conducting human-robotic missions.”

The FINESSE team now will begin to prepare for the rigors of the field with site selection workshops and a series of operational readiness tests. Team training sessions will develop mission-specific flight rules and operational protocols.

Ames' David Blake using the Terra instrument

The Terra in-situ portable miniaturized X-ray diffraction instrument, used to identify minerals.

Image Credit: NASA

The field program will begin at Craters of the Moon National Monument and Preserve in Idaho and includes a robotic mission involving NASA’s K-Rex planetary rover and a set of Unmanned Aerial Vehicles (UAVs). The K-Rex rover, developed by the NASA Ames Intelligent Robotics Group, will simulate a robot on the surface of the moon or other body, while the UAVs will simulate orbiting spacecraft. The team also will use the Terra in-situ portable X-ray diffraction (XRD) system instrument. Terra is a miniaturized laboratory for identifying minerals and is a spin-off of the Ames-developed Chemistry and Mineralogy (CheMin) instrument onboard the Curiosity mission that landed on Mars in August 2012.

“We will use these platforms to conduct science research and to help us select areas of interest for follow up during a coordinated human-robotic mission in the subsequent years,” said Anthony Colaprete, deputy principal investigator of the FINESSE team at Ames.

The team also will travel to the West Clearwater Lake Impact Structure to conduct a human mission to study this unique impact crater site. Finesse fieldwork will focus on exploration techniques and simultaneously aim to maximize science return.

“When we say ‘science return’ we mean our ability to study geological features that will enable us to definitively answer questions about fundamental planetary science processes,” said Colaprete. “We also will evaluate how robots – working before, in parallel, or after humans – might increase the science return from future exploration missions.”

“We look forward to collaborative scientific discoveries from these teams,” said Jim Green, director of the Planetary Science Division of NASA’s Science Mission Directorate in Washington. “These results will be vital to NASA successfully conducting the ambitious activities of exploring the solar system with robots and humans.”


Rachel Hoover
Ames Research Center, Moffett Field, Calif.

SOURCE NASA.GOV

 

B)Superconductivity in orbit: Scientists find new path to loss-free electricity

Superconductivity in orbit: Scientists find new path to loss-free electricity

These images show the distribution of the valence electrons in the samples explored by the Brookhaven Lab collaboration — both feature a central iron layer sandwiched between arsenic atoms. The tiny red clouds (more electrons) in the undoped sample on the left (BaFe2As2) reveal the weak charge quadrupole of the iron atom, while the blue clouds (fewer electrons) around the outer arsenic ions show weak polarization. The superconducting sample on the right (doped with cobalt atoms), however, exhibits a strong quadrupole in the center and the pronounced polarization of the arsenic atoms, as evidenced by the large, red balloons. Credit: Brookhaven National Lab

(Phys.org) —Armed with just the right atomic arrangements, superconductors allow electricity to flow without loss and radically enhance energy generation, delivery, and storage. Scientists tweak these superconductor recipes by swapping out elements or manipulating the valence electrons in an atom’s outermost orbital shell to strike the perfect conductive balance. Most high-temperature superconductors contain atoms with only one orbital impacting performance—but what about mixing those elements with more complex configurations?

Now, researchers at the U.S. Department of Energy’s Brookhaven National Laboratory have combined atoms with multiple orbitals and precisely pinned down their electron distributions. Using advanced electron diffraction techniques, the scientists discovered that orbital fluctuations in iron-based compounds induce strongly coupled polarizations that can enhance electron pairing—the essential mechanism behind superconductivity. The study, set to publish soon in the journal Physical Review Letters, provides a breakthrough method for exploring and improving superconductivity in a wide range of new materials.

“For the first time, we obtained direct experimental evidence of the subtle changes in electron orbitals by comparing an unaltered, non-superconducting material with its doped, superconducting twin,” said Brookhaven Lab physicist and project leader Yimei Zhu.

While the effect of doping the multi-orbital barium iron arsenic—customizing its crucial outer electron count by adding cobalt—mirrors the emergence of high-temperature superconductivity in simpler systems, the mechanism itself may be entirely different.

“Now superconductor theory can incorporate proof of strong coupling between iron and arsenic in these dense electron cloud interactions,” said Brookhaven Lab physicist and study coauthor Weiguo Yin. “This unexpected discovery brings together both orbital fluctuation theory and the 50-year-old ‘excitonic’ theory for high-temperature superconductivity, opening a new frontier for condensed matter physics.”

Atomic Jungle Gym

Imagine a child playing inside a jungle gym, weaving through holes in the multicolored metal matrix in much the same way that electricity flows through materials. This particular kid happens to be wearing a powerful magnetic belt that repels the metal bars as she climbs. This causes the jungle gym’s grid-like structure to transform into an open tunnel, allowing the child to slide along effortlessly. The real bonus, however, is that this action attracts any nearby belt-wearing children, who can then blaze through that perfect path.

 

 

C)What are the chances that a particle collider’s strangelets will destroy the Earth?

RHIC

A gold-ion collision in the STAR detector at RHIC. Critics argue that no matter how small the risks of the RHIC program, they are still worth an investigation. Credit: Brookhaven National Laboratory

(Phys.org) —At the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) in Long Island, New York, scientists study high-speed ion collisions that reveal what the universe may have looked like moments after the Big Bang. RHIC is the second-highest-energy heavy-ion collider in the world, after the Large Hadron Collider (LHC), and currently the only operating particle collider in the US.

Even before RHIC began operating in 2000, some people worried that the unprecedented experiment would pose risks of potentially catastrophic scenarios. Some of the concerns included the creation of a black hole or production of strange matter that could result in the destruction of the Earth, possibly within seconds.

In 1999, before the collider opened, the media attention on the subject prompted BNL to form a committee of scientists to investigate the probability of such catastrophic scenarios. A few months later, the committee concluded that RHIC was safe.

RHIC has now been running for nearly 15 years, and scientists have used it to make many fascinating discoveries, such as that of a quark-gluon plasma with a temperature of 4 trillion K. This liquid-like substance is unlike any kind of normal matter and recreates the conditions that existed during the first seconds of the universe.

But due to budget cuts, in 2013 a government advisory panel recommended shutting down RHIC in the coming years as funding is put toward other projects. The US Consolidated Appropriations Act of 2014, passed just a few weeks ago, includes a provision for the establishment of a nine-member commission to evaluate the cost-effectiveness of all of the US national labs, including RHIC. It’s called the Commission to Review the Effectiveness of the National Energy Laboratories.

According to Eric E. Johnson, Associate Professor of Law at the University of North Dakota, and Michael Baram, Professor Emeritus at Boston University Law School, this may also be a good time to reevaluate the safety risks at RHIC. They have written an  opinion piece on the subject that is posted at International Business Times.

Johnson and Baram are calling for the new commission to look into the risks of RHIC destroying the Earth in addition to evaluating the financial aspects. A large part of the motivation for their appeal is because of the ongoing upgrades to RHIC. The collider is  preparing for its 14th run, where it will be operating at 18 times the luminosity for which it was originally designed. The high luminosity will enable scientists to conduct more detailed studies of the quark-gluon plasma’s properties and investigate how it transitions into the normal matter that we see in the universe today.

Another area that Johnson and Baram argue begs some scrutiny is that RHIC is now running at lower energies than in the past. Somewhat counterintuitively, lower energies may pose a higher risk than higher energies. In the original risk assessment report in 1999, the scientists stated that “Elementary theoretical considerations suggest that the most dangerous type of collision is that at considerably lower energy than RHIC.” That assessment referenced RHIC’s original design energy of 100 GeV. Over the years, lower-energy experiments were performed, and the 2014 run will include three weeks at 7.3 GeV.

Johnson and Baram are concerned that these changes might increase the possibility that the collider will generate strangelets, hypothetical particles consisting of up, down, and strange quarks. Some hypotheses suggest that strangelet production could ignite a chain reaction converting everything into strange matter.

In their opinion piece, Johnson and Baram quote Sir Martin Rees, Astronomer Royal of the United Kingdom, who stated that the Earth would then become “an inert hyperdense sphere about one hundred metres across.”

Along with other critics concerned with safety, Johnson and Baram are concerned that the original risk assessment in 1999 was biased because all of the committee members were either planning to participate in RHIC experiments or had a deep interest in the RHIC’s data. The diversity of the new commission may allow it to overcome that problem.

Since the new commission will reflect a broad range of expertise in science, engineering, management, and finance, Johnson and Baram think that “this gathering of talent is a unique opportunity to ensure the RHIC gets the rigorous, independent risk analysis it has long warranted.”

“The luminosity upgrade, along with other evolutions of the RHIC program—including running collisions at different energies—suggests that the question of risk needs a fresh look,” Johnson told Phys.org. “For example, one of the reassurances given in the original safety report in 1999 was that the RHIC would run at a relatively high energy that would make strangelet formation less likely. But now the RHIC is being run at much lower energies. So, a re-evaluation is in order.

“Bottom line, I can’t say whether or not the RHIC program is so risky that it should be shut down. But I do think it’s clear that the original safety assessment lacked independence and that it is now woefully outdated. The Commission to Review the Effectiveness of the National Energy Laboratories is an opportunity to look at the issue in a fair and complete way.”

In the end, the dilemma raises the question of whether and how to perform unbiased low-probability, high-impact risk assessment for large science experiments—and whether it’s possible to achieve this feat in a way that satisfies everyone.

SOURCE  http://phys.org

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Ραδιόφωνο; Τέσλα και όχι Μαρκόνι

Στις 13 Φεβρουαρίου του 2014 γιορτάζεται η Παγκόσμια Ημέρα Ραδιοφώνου, ενός μέσου μαζικής επικοινωνίας που εδώ κι ένα σχεδόν αιώνα έχει διαμορφώσει καθοριστικά την κοινωνία, την οικονομία και τον ανθρώπινο πολιτισμό. Το ραδιόφωνο έκανε, κατά κοινή ομολογία, τον πλανήτη μας «μικρότερο», φέρνοντας τους ανθρώπους πιο κοντά, ενώ ταυτόχρονα διεύρυνε τους ορίζοντες τους, μεταδίδοντας πληροφορίες και ιδέες σε όλα τα μήκη και τα πλάτη του πλανήτη, πολύ πριν από την τηλεόραση και το διαδίκτυο.

Ακόμη και σήμερα το ραδιόφωνο αποτελεί κυρίαρχο μέσο μαζικής ενημέρωσης, ειδικά στις φτωχότερες χώρες του πλανήτη, όπου η θέση των γυναικών είναι υποδεέστερη, όπως επισημαίνει στο σχετικό μήνυμά του ο γενικός γραμματέας του ΟΗΕ: «Η Παγκόσμια Ημέρα Ραδιοφώνου αναγνωρίζει τον μοναδικό ρόλο και την επιρροή ενός μέσου που προσεγγίζει το μεγαλύτερο κοινό παγκοσμίως. Η φετινός εορτασμός υπογραμμίζει την ανάγκη για την ύπαρξη ραδιοφωνικών σταθμών παντού στον κόσμο, με στόχο την προώθηση της φωνής των γυναικών και την ενίσχυση του ρόλου τους στους ίδιους τους ραδιοφωνικούς σταθμούς. Τα ραδιοκύματα συχνά καθυστερούν όταν πρόκειται για την ισότητα των φύλων. Η φωνή των των γυναικών δεν έχει ακουστεί αρκετά, μπροστά ή και πίσω από το μικρόφωνο. Δεν υπάρχουν αρκετές ραδιοφωνικές εκπομπές με θέμα τις γυναίκες και τα κορίτσια. Οι γυναίκες αποτελούν μόνο το ένα τέταρτο των μελών των Διοικητικών Συμβουλίων των Επιχειρήσεων Μέσων Ενημέρωσης στον κόσμο. Ενθαρρύνω τους ραδιοφωνικούς σταθμούς να δίνουν τον λόγο στις γυναίκες τόσο στο προσωπικό τους, όσο και στο ακροατήριό τους. Αυτή είναι μια ευκαιρία για όλους. Ας γιορτάσουμε την Παγκόσμια Ημέρα Ραδιοφώνου χαιρετίζοντας τις γυναίκες στο ραδιόφωνο σήμερα και κάνοντας ό,τι καλύτερο για την γαλούχηση των φωνών του αύριο».

Οι πρωτοπόροι των ραδιοκυμάτων

Δύσκολα μπορούμε να φανταστούμε σήμερα τον κόσμο, που δονείται από τις ραδιοφωνικές εκπομπές, βυθισμένο στη σιωπή των ερτζιανών κυμάτων.Κι όμως αυτό συνέβαινε πριν από μόλις 130 χρόνια, όταν μια ομάδα πρωτοπόρων, επιστημόνων κι εφευρετών, άνοιξε το δρόμο για την αξιοποίηση του ηλεκτρομαγνητικού φάσματος. Πρώτος ήταν ο Χάινριχ Ρ. Χερτζ, που από το 1886 ως το 1888, απέδειξε με μια σειρά από πειράματα την πρακτική εφαρμογή της θεωρίας των ηλεκτρομαγνητικών κυμάτων του Μάξγουελ. Προς τιμήν του τα κύματα αυτά ονομάστηκαν από τότε Ερτζιανά.

Ακολούθησε το Σερβο-αμερικανός εφευρέτης κι επιστήμονας Νίκολα Τέσλα (1856-1943), ο οποίος το 1891 παρουσίασε στο κοινό την πρώτη ασύρματη μετάδοση της ενέργειας, που ήταν τότε γνωστή ως «Φαινόμενο Τέσλα».
Το 1893 ο Τέσλα άρχισε να ερευνά, να πειραματίζεται ασταμάτητα πάνω στα ραδιοκύματα και, τελικά, να περιγράφει λεπτομερειακά τις βασικές αρχές της ραδιεκπομπής.  Σε μια σειρά από διαλέξεις και επιδείξεις στο Σεντ Λούις του Μιζούρι και στο Ινστιτούτο Φραγκλίνου στη Φιλαδέλφεια, ο Τέσλα απέδειξε πως ήταν εφικτή μια ραδιομετάδοση. Έτσι γεννήθηκε το ραδιόφωνο!

Την περίοδο που ο Τέσλα ήταν έτοιμος να κάνει το μεγάλο άλμα και να υλοποιήσει την πρώτη φάση του σχεδίου του, που αφορούσε την κατασκευή μεγάλων ραδιοπομπών και ραδιοδεκτών, συνέβη ένα πολύ δυσάρεστο γεγονός. Στις 13 Μαρτίου του 1895 μια ύποπτη πυρκαγιά, πιθανόν εμπρησμός εκ μέρους των συνεργατών του Έντισον, κατέστρεψε το εργαστήριο του στη Νέα Υόρκη και μαζί του σημειώσεις, σχέδια, μοντέλα ραδιοαυτόματων συσκευών, ταλαντωτών, επαγωγικών κινητήρων καθώς και ολόκληρο το πολύτιμο τεχνικό του αρχείο. Όμως ο Τέσλα δεν το έβαλε κάτω και, με τη βοήθεια της ισχυρής του μνήμης, άρχισε να σχεδιάζει από την αρχή τα πάντα.
Radio Tesla

Το 1896 ο Τέσλα συνέχισε στο νέο του εργαστήριο τα πειράματα του πάνω στα ρεύματα υψηλής συχνότητας και στη ραδιοεπικοινωνία. Τότε συνέλαβε και την ιδέα του Παγκόσμιου Συστήματος (World System) μετάδοσης πληροφοριών και ενέργειας, που θα στοίχειωνε τη σκέψη του για τις επόμενες δεκαετίες. Την άνοιξη του 1897, σ’ έναν πρόχειρο πειραματικό σταθμό έξω από τη Νέα Υόρκη, ο εφευρέτης κατόρθωσε να εκπέμψει ραδιοσήματα σε απόσταση 40 χιλιομέτρων. Τότε κατοχύρωσε και το βασικό σχέδιο ραδιοτεχνικής, το οποίο και εκμεταλλεύτηκε στη συνέχεια ο Γουλιέλμο Μαρκόνι προκειμένου να κατασκευάσει το πρώτο ραδιόφωνο:μια εφεύρεση που δικαιωματικά ανήκει στον Τέσλα.

Στις αρχές του 1898 ο Τέσλα πραγματοποίησε στην προβλήτα του λιμανιού της Νέας Υόρκης μια πετυχημένη δοκιμή ενός μοντέλου τηλεκατευθυνόμενου πλοιαρίου. Εκεί συνέρευσε μεγάλο πλήθος, που έκπληκτο παρακολούθησε τον εφευρέτη να κάνειεπίδειξη του τηλεκατευθυνόμενου πλοιαρίου του και να εξηγεί τις αρχές της ρομποτικής και του αυτοματισμού.

Από τον Μάιο του 1899 μέχρι τις αρχές του 1900 ο Τέσλα πραγματοποίησε μια σειρά από εντυπωσιακά πειράματα στο Κολοράντο Σπρινγκς σε υψόμετρο 2.200 μέτρων πάνω στην ασύρματη μεταφορά της ενέργειας. Αυτή η γνώση ήταν απαραίτητη στον Σερβο-αμερικανό εφευρέτη προκειμένου να υλοποιήσει το Παγκόσμιο Σύστημα μεταφοράς σημάτων και ενέργειας, που οραματιζόταν.  Ανάμεσα στα πρώτα πράγματα, που έκανε ο εφευρέτης μόλις επέστρεψε στη Νέα Υόρκη, ήταν και να κατοχυρώσει τις νέες του ευρεσιτεχνίες για τις ραδιοεπικοινωνίες και την ασύρματη μεταφορά ενέργειας, οι οποίες βασίστηκαν στα πειράματα του στο Κολοράντο Σπρινγκς.
«O Μαρκόνι χρησιμοποιεί 17 ευρεσιτεχνίες μου»

Παράλληλα, με αρχική χρηματοδότηση του μεγαλοτραπεζίτη Τζ. Π. Μόργκαν, άρχισε να κατασκευάζει στο Γουόρντεκλιφ του Λονγκ Άιλαντ έναν γιγαντιαίο πύργο, που θα λειτουργούσε ως ο πρώτος παγκοσμίως μεταδότης ραδιοσημάτων και ενέργειας. Ενώ οι εργασίες κατασκευής του πρώτου παγκόσμιου ραδιοσταθμού συνεχιζόταν, έφθασε στ’ αυτιά του Τέσλα μια μοιραία είδηση: ο παγκόσμιος τύπος διατυμπάνιζε το γεγονός ότι στις 12 Δεκέμβρη του 1901 ο Ιταλός Γκουλιέλμο Μαρκόνι είχε κατορθώσει να στείλει το γράμμα S από τη μια πλευρά του Ατλαντικού στην άλλη. Συγκεκριμένα ο Μαρκόνι εξέπεμψε ραδιοκύματα από το νότιο άκρο της Αγγλίας, χρησιμοποιώντας ένα αερόστατο για ν’ ανυψώσει την κεραία όσο το δυνατόν ψηλότερα και τα σήματα αυτά ελήφθησαν στη Νέα Γη.

Για τον Τέσλα αυτή η είδηση ήταν μια δυσάρεστη έκπληξη. Ο χρηματοδότης του Τζ. Π. Μόργκαν ξαφνιάστηκε από το γεγονός ότι ο Μαρκόνι τα κατάφερε χωρίς να κατασκευάσει κάτι που να έμοιαζε με τον τεράστιο και πολυδάπανο πύργο του Τέσλα κι αποφάσισε να του κόψει τις χορηγίες. Αναμφίβολα όμως όλοι οι ξαφνικοί θαυμαστές του Μαρκόνι δεν γνώριζαν ότι ο Ιταλός εφευρέτης είχε χρησιμοποιήσει την υπ’ αριθμόν 645 576 βασική ραδιοφωνική πατέντα του Τέσλα, την οποία είχε καταθέσει προς έγκριση το 1897 και πήρε την κατοχύρωση μόλις στις 20/3/1900.

Αφού Τέσλα έμαθε τις λεπτομέρειες από τον ηλεκτρομηχανικό Χ. Ότις Ποντ, που ήταν παρόν όταν ο Μαρκόνι έστειλε το πρώτο του σήμα, στο τέλος είπε: «Ο Μαρκόνι είναι καλό παιδί, ας συνεχίσει. Χρησιμοποιεί όμως 17 δικές μου ευρεσιτεχνίες». Ο Τέσλα  ήταν δικαιολογημένα πολύ θυμωμένος γι’ αυτή την πρωτοφανή κλοπή κι άρχισε να μιλά για συνωμοτικά σχέδια και μεθόδους «Βοργίων και Μεδίκων», που χρησιμοποιήθηκαν για να εμποδίσουν τα σχέδια του. Μάταια ωστόσο προσπάθησε να εξηγήσει ότι σ’ αυτόν άνηκαν τα πρωτοτόκια της ραδιοεπικοινωνίας.

Αυτή ήταν και η αρχή μιας σειράς από δικαστικές διαμάχες του Τέσλα με το Μαρκόνι σχετικά με τις κλεμμένες ευρεσιτεχνίες του πρώτου, που κράτησαν ως το 1904 με αποφάσεις που ευνοούσαν τον Μαρκόνι, άσχετα αν ο Ιταλός εφευρέτης βασίστηκε ως κυρίως τις ευρεσιτεχνίες των άλλων πρωτοπόρων και ειδικά του Τέσλα. Έτσι η εφεύρεση του ραδιοφώνου κατοχυρώθηκε αρχικά στον Γουλιέλμο Μαρκόνι. Σύντομα οι πάντες έμαθαν πως ο Ιταλός εφευρέτης ήταν ο «πατέρας του ραδιοφώνου», ενώ ο Τέσλα, που είχε οράματα για την Ελεύθερη Ενέργεια, άρχισε σταδιακά να περιθωριοποιείται και να αγνοείται. Το όνομα του Τέσλα κόντεψε σχεδόν να διαγραφεί από κάθε λεωφόρο της γνώσης και λίγο έλειψε να θαφτεί στο απέραντο νεκροταφείο των αγνώστων της ιστορίας. Και θα συμβεί κάτι τέτοιο, αν το έργο και οι ιδέες του Τέσλα δεν ήταν τόσο πρωτοποριακές και μεγαλειώδεις, ώστε να είναι αδύνατον να συγκαλυφθούν εντελώς.
H δικαίωση από το Ανώτατο Δικαστήριο των ΗΠΑ

Τελικά, κι ενώ όλος ο κόσμος συνέχισε να πιστεύει πως ο Μαρκόνι ήταν ο εφευρέτης του ραδιοφώνου, το 1943, λίγους μήνες μετά τον θάνατο του Τέσλα, το Ανώτατο Δικαστήριο των ΗΠΑ αποφάσισε να αποκαταστήσει τον Σερβο-αμερικανό εφευρέτη και αποφάνθηκε πως ο Τέσλα ήταν ο πραγματικός εφευρέτης του ραδιοφώνου. Η απόφαση του Ανωτάτου Δικαστηρίου δεν έλαβε υπόψιν της το γεγονός πως ο Μαρκόνι πέτυχε όντως να εκπέμψει το πρώτο διαμορφωμένο ραδιοσήμα, αλλά το γεγονός πως το κατάφερε αυτό χρησιμοποιώντας έναν συνδυασμό από προϋπάρχουσες πατέντες του Τέσλα με ελάχιστες βελτιώσεις.

Μπορεί το Ανώτατο Δικαστήριο των ΗΠΑ να αναγνώρισε με απόφαση του ότι ο Μαρκόνι δεν ήταν ο πραγματικός εφευρέτης του ραδιοφώνου, αλλά τα σχολικά και ιστορικά βιβλία συνεχίζουν να τον αναφέρουν ως τέτοιο. Μέχρι πρόσφατα οι ασυρματιστές του ναυτικού ονομάζονταν «Μαρκόνηδες» και όχι «Τεσλιανοί», όπως θα ήταν το σωστό. Ακόμη και σήμερα οι περισσότεροι άνθρωποι πιστεύουν πως ο Μαρκόνι είναι ο «πατέρας» του ραδιοφώνου και όχι ο Τέσλα. Κι αυτό δυστυχώς δε συμβαίνει μόνον στη περίπτωση του ραδιοφώνου, αλλά και σε πολλές άλλες εφευρέσεις, ευρεσιτεχνίες (είχε συνολικά 700) και ιδέες του Τέσλα, που άλλαξαν τον κόσμο μας. Όπως αναφέρει χαρακτηριστικά και ο Max E. Valentinuzzi στο άρθρο του Nikola Tesla: Was He So Much Resisted and Forgotten, στο Engineering in Medicine and Biology Magazine (1998) «Πέρασα όλα μου τα χρόνια στη σχολή των ηλεκτρολόγων μηχανολόγων (1951-1956) χωρίς ν’ ακούσω το όνομα του Νίκολα Τέσλα, ακόμη και σ’ εκείνα τα μαθήματα που σαφώς αναφέρονται σε μηχανές εναλλασσόμενου ρεύματος ή σε μεταφορά ενέργειας ή σε ασύρματη επικοινωνία (ραδιόφωνο). Ξόδεψα αρκετό καιρό σε μια ιδιωτική εταιρεία τηλεπικοινωνιών, θυγατρική εταιρεία της RCA, όπου είχα την ευκαιρία να γνωρίσω αρκετά σημαντικούς και έμπειρους ανθρώπους. Ποτέ, σε τόσες πολλές διαλέξεις, συναντήσεις και συζητήσεις που είχα, δεν αναφέρθηκε πουθενά ο Τέσλα. Πάντως θυμάμαι καλά ονόματα λιγότερο σημαντικών πρωτοπόρων στο χώρο του ηλεκτρισμού. Αρκετοί συνάδελφοι και παλιοί συμφοιτητές μου είχαν παρόμοιες εμπειρίες. Ο Τέσλα ήταν ανύπαρκτος».

Ο Γιώργος Στάμκος είναι συγγραφέας, βιογράφος του Νίκολα Τέσλα και δημιουργός του περιοδικού Ζενίθ

PAGAN TVXS.GR
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BLACK HOLES:TRAVELLING TO ANOTHER UNI-VERSE

Stephen Hawking’s new research: ‘There are no black holes’

 

An artist's impression of a black hole

Exactly 40 years after famed theoretical physicist Stephen Hawking brought event horizons and black holes into the public eye, he is now claiming that black holes don’t actually exist. Instead of all-consuming event horizons and black holes which nothing can escape from, Hawking now proposes that there are “apparent horizons” which suck in matter and energy — but only temporarily, before eventually releasing them again.

To be clear, Hawking isn’t proposing that black holes don’t exist — just that black holes, as we’ve understood them for the last 40 years or so (thanks to work done by Hawking and others), don’t exist. The current understanding is that black holes are surrounded by an event horizon — a boundary in spacetime which only allow matter and energy to pass through one way, towards the black hole. It is, in other words, the point of no return. This is why black holes appear black — energy can’t escape, and so they produce no light and no heat. In thermodynamics terms, a black hole is a perfect black body — an object that absorbs all energy and radiation.

The problem with this theory, though, is that it’s based on general relativity. In recent years, as our understanding of quantum theory has improved, numerous conflicts have arisen, especially in places where both theories apply — such as black holes and event horizons. Basically, quantum mechanics has a big issue with the idea that event horizons completely and utterly destroy information — a big no-no in the world of quantum. Hawking’s new proposal tries to ameliorate this conflict between the two theories. (Read: Wormholes are just quantum entangled black holes, says new research.)

The Event Horizon's "gravity drive"

The Event Horizon’s “gravity drive.” I wonder if the film will have to be renamed Apparent Horizon…

In a short research paper (see below) called “Information Preservation and Weather Forecasting for Black Holes,” Hawking proposes that black holes are instead enveloped by an apparent horizon. Basically, instead of an event horizon that blocks everything absolutely, an apparent horizon suspends matter and energy from trying to escape — and when it does escape, due to the wild fluctuations within a black hole and its apparent horizon, the energy would be released in a garbled form. Hawking likens these fluctuations to weather on Earth: “It will be like weather forecasting on Earth. That is unitary, but chaotic, so there is e ffective information loss. One can’t predict the weather more than a few days in advance.” (Unitarity is the part of quantum theory that strongly disapproves of event horizons being a point of no return.)

The research paper concludes: “The absence of event horizons mean that there are no black holes — in the sense of regimes from which light can’t escape to infi nity. There are however apparent horizons which persist for a period of time.” (Read: NASA’s Swift discovers 100,000 super-massive black holes, in its spare time.)

It’s worth noting that Hawking’s new paper is just two pages long, contains no calculations, and hasn’t yet passed peer review. It does seem to do what it set out to achieve, though. Complex problems don’t necessarily have complex solutions. Speaking to Nature, Hawking had a little more to say about the matter, too: “There is no escape from a black hole in classical theory,” Hawking said. “[Quantum theory, however] enables energy and information to escape from a black hole.” To fully explain the process, though, the theoretical physicist admits that we’re still looking for a theory that ties up gravity with the other universal constants — a theory that , Hawking says, “remains a mystery.”

By Sebastian Anthony on January 27, 2014 at 9:48 am

 

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source  http://www.extremetech.com/ , http://arxiv.org/

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ARCHAIA HELLEENIKEE TECHNOLOGIA (1)

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(SYNECHIZETAI)

EUCHARISTOOMEN EPEIE PANOPEA

πηγη  καθημερινη

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R–e-peated EVOLUTION

What is evolution?

In its original sense, evolution meant “unrolling”, as if a papyrus scroll were being unrolled to reveal its contents. We may talk about the “evolution” of many things, from an individual’s lifetime to the evolution of the universe. In the most general sense, evolution means “change”.

Biologists are very specific about the kinds of processes that qualify as “evolution” in the biological sense. Biological evolution is genetic change in a population over time. Populations and individuals change in many ways, but only some changes are evolution.

Here’s a list of seven things about evolution. It’s not comprehensive but it hits on several important issues that help to understand how evolutionary biologists think about the process of evolutionary change.

  1. Evolution is change in a population. Individuals change during their lifetimes, even day to day. Those changes are not biological evolution, although they may be products of evolution in past populations. Likewise, a forest may change over time, as some kinds of trees proliferate and others disappear. Those changes in community structure are not themselves biological evolution, although they may influence the evolution of the populations of trees composing the forest.

  2. Evolution is genetic change. Many kinds of phenotypic changes don’t involve evolution. For example, many human populations have markedly increased in lifespan during the last 100 years, mostly as a result of improvements in nutrition and reductions in disease. Those changes are important and highly visible, but they are not biological evolution. Physical characteristics and behaviors can only evolve if they have some genetic contribution to their variation in the population — that is, if they are heritable.

  3. Many kinds of genetic changes are important to evolution.Mutations happen when a DNA sequence is not replicated perfectly. A sequence may undergo a mutation to a single nucleotide, small sequences of nucleotides can be inserted or deleted, large parts of chromosomes can be duplicated or transposed into other chromosomes. Some plant populations have undergone duplications or triplications of their entire genomes. These patterns of genetic change can have a wide range of effects on the physical form and behavior of organisms, or may have no effects at all. But all of them follow the same mathematical principles as they change in frequency within populations.

  4. Evolution can be non-random. Populations of organisms cannot grow in numbers indefinitely, so that individuals that successfully reproduce will have their genes increase in proportion over time. Among the genes carried by such successful individuals may be some that actually cause them to survive or reproduce, because they fit the environment better. The survival and proliferation of such genes is not a matter of chance; it is a result of their value in the environment. This process is called natural selection, and it is the reason why populations come to have forms and behaviors that are well-suited to their environments.

  5. Evolution can be random, too. Many genetic changes are invisible and make no difference to the organisms. Many changes that do make a noticeable difference to the organisms’ form or behavior nevertheless still do not change the chance of reproducing. Even individuals with the best genes still have a strong random component to their reproduction, and in sexual organisms genes assort randomly into sperm and egg cells. As a result, even when an individual has a beneficial gene that increases the chance of reproducing, that valuable gene still is very likely to disappear quickly after it first appears in the population. Genetic drift is strongest when populations are small or genes rare, but it is there all the time. Random chance has a continual role in evolutionary change.

  6. Populations evolve all the time. No population can stay static for long. Reproduction is not uniform, and no organism replicates DNA perfectly. The genome of the simplest bacterium has thousands of nucleotides, ours has billions. Keeping these sequences constant, generation after generation, is a task no population has ever managed to do. Genetic variation is constantly introduced into populations by mutation and immigration, rare genetic variations are constantly disappearing when individuals who carry them don’t pass them on, and occasionally rare genes become common — whether by natural selection or genetic drift. If a population’s physical form remains the same for a long time, we have a good reason to suspect that natural selection is working to oppose random changes.

  7. Evolutionary theory has changed a lot since Darwin’s day.Charles Darwin recognized several key insights about biological evolution, including the process of natural selection, the tree-like pattern of relationships among species, and the potential for significant changes when processes act through small, incremental steps across geological timescales. But we know a lot more now than Darwin knew. We understand the molecular basis of genetic changes, and many of the ways that the features of organisms can be affected by genetic and environmental change. We have learned much about the limits of evolution, the alternative patterns of change caused by environments, and the importance of randomness. We now know much about the changing pace of evolution, seeing it as a dynamic process that can happen in fits and starts.

Evolution is the most powerful idea in biology, organizing our knowledge about the history and diversity of life. We understand our own origins using the same tools that we use for organisms across the tree of life, from the simplest bacteria to the largest whales.

 

Neandertal self-medication

Karen Hardy and colleagues (2013) have a brief paper in a recent issue of Antiquity putting into context their recent finding about possible medicinal plant use by Neandertals. In 2012, this team of authors reported on their examination of the dental calculus of the El Sidrón Neandertals. They found some evidence for plant food consumption, in line with results from other Neandertal sites. But additionally they found chemical traces of other interesting things:

  1. Evidence of oil shale or bitumen. Bitumen was used by Neandertals at other sites as an adhesive for hafting stone points onto wooden spears or handles. That evidence came from the stone points themselves, so it is possible that bitumen was used more widely as an adhesive or preservative in contexts that do not persist as long in the archaeological record.

  2. Alkyl phenols and polynuclear aromatic hydrocarbons consistent with exposure to wood smoke or smoked food.

  3. Chemical residues consistent with consumption of yarrow and chamomile, including bitter-tasting and appetite-suppressing compounds.

  4. A very low level of proteins and absence of lipid components suggested that the diet of these individuals was protein-poor during the time they were forming calculus.

They reinforced conclusions about cooking plant foods by Neandertals, based on both the chemical evidence and the examination of starch granules embedded in the calculus:

Using mass spectrometry, we have identified the ingestion of cooked carbohydrates in the calculus of two adults, one adult in particular having apparently eaten several different carbohydrate-rich foods. The evidence for cooked carbohydrates is confirmed both by the cracked/roasted starch granules observed microscopically and the molecular evidence for cooking and exposure to wood smoke or smoked food in the form of methyl esters, phenols, and polynuclear aromatic hydrocarbons (notably pyrene and fluoranthene) found in the dental calculus.

 

The more intriguing observation was the yarrow and chamomile consumption. Hardy and colleagues considered it likely that these plants were used for medicinal purposes by the Neandertals. They discuss the botanical qualities of these plants briefly in their current paper (2013):

Yarrow is a flowering plant in the Asteraceae family, common across temperate regions. It was used as a vegetable in the Middle Ages, notably as a component of soup, but has an extended history of medicinal use, in particular as an astringent (Chandler et al. 1982). Camomile tea is well-known today as an aid for stomach complaints and nervousness, though there is little record of it as a food. Bioactive constituents are linked to antimicrobial and anti-inflammatory properties (McKay & Blumberg 2006), while its ability to assist with general anxiety disorder has been demonstrated (Jay et al. 2009).

 

Laura Buck and Chris Stringer (2013) suggested an alternative explanation for the yarrow and chamomile. They note that arctic peoples often eat the stomach contents of animals they eat, which comprises one of the major sources of plant foods in their diet. In such cases, the plants are not necessarily those most palatable or digestible by humans.

We are not, of course, proposing that Neanderthals would not have eaten plant foods, nor are we discounting the possibility of Neanderthal self-medication. However we suggest that, given the evidence for widespread consumption of stomach contents in recent human groups, and the likely benefits of a rich source of vitamin C and carbohydrates (to say nothing of the possible cultural or social reasons for chyme consumption) this behaviour should be taken into account as a possible source of plant foods, including ‘medicinal’ ones, in the archaeological and fossil record.

 

Hardy and colleagues (2013) do not directly react to this argument (which may have emerged after submission of the article), but they do note that the El Sidrón Neandertals lived during a time of relatively mild climate when plant foods would have been easily available in the immediate surroundings. The evidence for cooked starch granules and paucity of protein further suggest that the plants were selected and used by the Neandertals rather than opportunistically consumed as part of herbivore stomach contents.

But these possibilities are not mutually exclusive, either. From my point of view, one of the most likely ways that Neandertals may have accomplished the gelatinization of starches is by cooking grains and other plants inside of animal bladders, including the stomach.

We may also consider that both yarrow and chamomile are used for dying fabrics, so it is not impossible that the Neandertals were processing them as pigments by chewing them. They are already known to have used red earth pigments and black manganese pigments.

Hardy and colleagues finish their 2013 paper by considering what self-medication would mean for our understanding of Neandertal behavior:

Though all primates (and other animals) have varying levels of enzymes which make us more or less tolerant of certain toxins, there are plants which are poisonous to all; in order to survive, hominins needed to know which plants not to eat and how and when to eat those plants they selected. The use of edible bitter tasting plants by the Neanderthals of El Sidrón suggests their knowledge was sufficiently refined to use plants with confidence even when their bitter taste warned of potential toxicity. This demonstrates that their knowledge of plants was at least equal to today’s higher primates; with their additional linguistic and technological abilities it may have been far more elaborate. Rather than contradicting the extensive evidence for consumption of meat, the evidence for the use of plants adds a rich new dimension to our developing knowledge of Neanderthal life. We can never know for sure why yarrow and camomile were ingested at El Sidrón, but we propose that the evidence for self-medication offers the most convincing behavioural context.

 

An aside: I know there are anthropologists who will take in this evidence of interesting Neandertal behavior and argue they had a specific “module” in their mind that facilitated naturalistic knowledge, while simultaneously arguing they lacked some crucial “module” enabling modern human social behavior.

That’s special pleading. We do not need to hypothesize that Neandertals had a multicameral mind to explain that their cultures were different from ours. Cultures do not weigh every kind of activity or knowledge equally or enable them to be learned equally easily.

References:

Buck, L. T., & Stringer, C. B. (2013). Having the stomach for it: a contribution to Neanderthal diets?. Quaternary Science Reviews. (in press)doi:10.1016/j.quascirev.2013.09.003

Hardy, K., Buckley, S., & Huffman, M. (2013). Neanderthal self-medication in context. Antiquity 87 (2013): 873–878. URL: http://antiquity.ac.uk/ant/087/ant0870873.htm

Hardy, K., Buckley, S., Collins, M. J., Estalrrich, A., Brothwell, D., Copeland, L., … & Rosas, A. (2012). Neanderthal medics? Evidence for food, cooking, and medicinal plants entrapped in dental calculus. Naturwissenschaften, 99(8), 617-626.

SOURCE  http://johnhawks.net/

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ΕΡΑΤΟΣΘΕΝΗΣ Ο ΚΥΡΗΝΑΙΟΣ

Υπό   Ευαγγέλου Σταμάτη μέλους της Διεθνούς
Ακαδημίας της Ιστορίας των Επιστήμων.

Ο  Ερατοσθένης  εγεννήθη  περί  το  290  π.  Χ.  εις  την  αποικίαν  της  Βορείου Αφρικής  Κυρήνην,  απέθανε  δε  εις  την  Αλεξάνδρειαν  περί  το  έτος  203  π.  Χ.
Εγκύκλιον μόρφωσιν και αρχάς της φιλοσοφίας έλαβεν εις την πατρίδα του, όπου είχε  διδασκαλον τον Λυσανίαν. Ακολούθως μετεβη εις τας Αθήνας όπου παρηκολούθησε μαθήματα  εις  την  Ακαδημίαν  του  Πλάτωνος,  εις  την  οποίαν  εδίδασκον,  μεταξύ άλλων, ο Αρκεσίλαος και ο Κράτης. Παρηκολούθησεν όμως μαθήματα και πλησίον
του στωικού Αρίστωνος. Εις ηλικίαν 40 ετών προσεκλήθη εις την Αλεξανδρειαν, υπό του  Βασιλέως  Πτολεμαίου  του  Γ,  και  ανέλαβε  την  μόρφωσιν  του  διαδόχου  του θρόνου,  του  μετέπειτα  βασιλέως  της  Αιγύπτου  Πτολεμαίου  του  Δ’  Προς  τούτοις ανετέθη  εις  ούτον  και  η  διεύθυνσις  του  εκεί  Πανεπιστημίου  και  της  περίφημου Βιβλιοθήκης  (του  Μουσείου,  ως  ελέγετο  τότε).

Λόγω  τον  δεσμών          του  προς  τους βασιλείς είχε πολλούς εχθρούς. Αναφέρεται, ότι ο Αθηναίος φιλόσοφος Πολέμων, εις
μίαν  πραγματείαν  του,  είχε  γράψει  «Περί  της  Αθήμησιν  Ερατοσθένους  επιδημίας»,
θεωρήσας  την  παρομονήν  του  Ερατοσθένους  εις  τας  Αθήνας,  ως  επιδημίαν.  Οι  εν
Αλεξάνδρεια άσπονδοι φίλοι του, του είχον προσάψει το παρωνύμιον «Ερατοσθένης
ο  Β  ή  ο  δεύτερος».  Και  τούτο  δια  τον  εξής  λόγον:  Ο  Δημόκριτος,  επειδή  ήτο
διάσημος  εις  1)  τα  Φυσικά  2)  τα  Ηθικά,  3)  τα  Μαθηματικά,  4)  τους  Εγκυκλίους
λόγους  και  5)  τας  Τέχνας  (δηλ.  την  Τεχνικήν)  εκαλείτο  πένταθλος.  Και  ο
Ερατοσθένης όμως ήτο πολύπλευρον πνεύμα, χωρίς όμως να αναγνωρίζουν την αξίαν
του,  οι  φθονούντες  αυτόν  αντίπαλοι  του.  Ωνόμαζον  λοιπόν  αυτόν  «Πένταθλος  Β’,
δηλαδή  Δημόκριτος  δεύτερος  ή  δεύτερος  Πλάτων».  Τα  επιστημονικά  όμως
επιτεύγματα  του  Ερατοσθένους  αποδεικνύουν,  ότι  πράγματι  ούτος  ήτο  μέγας
επιστήμων  και  ότι  οι  αντίπαλοι  αυτού  δεν  είχον  δίκαιον.

Όλα  τα  έργα  του
απωλέσθησαν  εκτός  ολίγων  αποσπασμάτων  μνημονευομένων  υπό  μεταγενεστέρων
συγγραφέων.  Μεταξύ  αυτών  αναφέρονται:  1)  Φιλολογικά  «Περί  της  αρχαίας
κωμωδίας  κλπ.»  2)  Σκευσγραφικα  (πραγματολογικόν  λεξικόν),  3)  Περί Αρχιτεκτονικής, 4) Γραμματικά, 5) Μαθηματικά, 6)  Αστρονομικά, 7) Γεωγραφικά.
Εις  τα Μαθηματικά  συγγράμματα  του  Ερατοσθένους  μνημονεύεται  πραγματεία
αυτού  υπό  τον  τίτλον  «Πλατωνικός∙  εις  την  οποίαν  λέγεται,  ότι  περιελαμβάνετο  η2 περιγραφή  συσκευής  διά  της  οποίας  ελύετο  το  πρόβλημα  του  διπλασιασμού  του
κύβου  (το  δήλιον  πρόβλημα)  και  ήτις  εκαλείτο  «μεσόλαβον»,  επειδή  δια  αυτής
ελαχβάνοντο αι δύο μέσοι ανάλογοι προς λύσιν του δηλίου προβλήματος. Πιθανόν η
πραγματεία Πλατωνικός θα ήτο και φιλοσοφικού περιεχόμενο».
Διά το μεσολάβον και την δι αυτού λύσιν του δηλίου προβλήματος λαμβάνομεν
πληροφορίας  παρά  του  σχολιαστού  έργων  του  Αρχιμήδους  Ευτοκίου  (6ος  αιών).
(Αρχιμήδους Άπαντα, τόμος 3ος, υπό I. L. Heimberg Λειψία 1915, σελ. 88—97). Το
μεσόλαβον  ήτο  εκ χαλκού,  προσηρμοσμένον δε  εις  την  στήλην,  εις  την  οποίαν  ήτο
και  επίγραμμα  αφιέρωσεως  τούτου  εις  τον  βασιλέα  Πτολεμαίον.  Εν  μεταφράσει  το
επίγραμμα έχει ως έξης :
«Εάν  ω  αγαθέ,  θέλης  να  έπιτυχης  διπλάσιον  κύβον από  ένα  μικρόν  ή  θελης  να
μετασχηματίσης  με  κοψμόν  τρόπον  κάθε  άλλο  στερεόν  τμήμα, τούτο  είναι  στο χέρι
σου»  και  θα  δυνηθής  να  μέτρησης  και  μάνδραν  ή  λάκκον  ή  ευρύ  κύτος  κοίλου
φρέατος,  εάν  εύρη: δύο  μέσους  αναλόγους∙ αφού  συμπεριλάβης  εντός δύο  κανόνων
ουνδρομείς,  των  οποίων  αι  τομαί  να  συγκλίνουν  προς  τα  άκρα  των  τερμάτων  των.
Μηδέ  να  ζητής  να  επιτυχής  τούτο  με  τα  δυσμήχανα  έργα  των  κυλίνδρων  του
Αρχύτου,  μηδέ να θέλης  να  το  εύρης  με  τας  τρεις  εκείνος  γραμμάς  του Μεναίχμου
τας  σχηματιζόμενας  διά  κωνικών  τομών,  μηδέ  εάν  κατασκευάζεται  υπό  του  θείου
Ευδόξου  είδος  τι  καμπύλων  γραμμών.  Διότι  με  αυτήν  την  συσκευήν  δύνασαι,
αναχωρών  από  μικράν  αρχήν  να  εύρης  μυριάδας  μέσων  ανάλογων  εύκολωτερον.
Είσαι  ευδαίμων,  Πτολεμαίε,  διότι  απολαύων  με  το  παιδί  σου  τας  νεανικάς
διασκεδάσεις, ου ο ίδιος εχάρισες εις αυτό όλα όσα είναι αγαπητά εις τας Μούσας και
εις τους βασιλείς∙ εις ό,τι δε αφορά εις το μέλλον, ουράνιε Ζεύ, μακάρι το παιδί σου
να δεχθή από το χέρι σου και να σκήπτρα. Και αυτά μεν ας γίνουν έτσι, είθε δε όποιος
βλέπει  το  ανάθημα  αυτό  να  λέγη,  ότι  τούτο  είναι  έργον  του  Ερατοσθένους  του
Κυρηναίου.
Το μεσόλαβον του Ερατοσθένους και η λύσις του δηλίου προβλήματος.
Εις το ορθογώνιον μεταλλικόν πλαίσιον ΑΕΘΚ δύνανται να διολισθαίνουν τα εκ
μετάλλου ή ξύλου ορθογώνια τρίγωνα ΑΛΖ, ΑΙΗ, ΙΚΘ. Λαμβάνομεν την ΑΕ, ως την
μεγαλυτέραν  των  δύο  δοθεισών  ευθειών,  μεταξύ  των  όποιων  πρέπει  να
παρεμβάλλωμεν  δύο  μέσας  ανάλογους  και  την  ΔΘ, ως  την  μικροτέραν,  η  όποια  να
είναι το ήμισυ της μεγαλυτέρας και να παριστά την πλευράν του δοθέντος κύβου. Το
πρώτον τρίγωνον το διατηρούμεν ακίνητον (σχ. 1).

image

3
Το  δεύτερον  και  τρίτον  τρίγωνα  τα  κινούμεν  προς  τ’  αριστερά,  μέχρις  ότου
επιτύχωμεν, ώστε η τομή της υποτεινούσης  του δευτέρου τρίγωνου μετά της καθέτου
ΛΖ του πρώτο» τρίγωνου, και η τομή της υποτεινούσης ΙΘ του τρίτου τρίγωνου μετά
της  καθέτου  ΙΗ  του  δευτέρου  τριγώνου,  το  μέσον  Δ  της  καθέτου  ΚΘ  του  τρίτου
τρίγωνου,  και  το  σημείον  Α  να  ευρίσκονται  επί  της  αυτής  ευθείας  ΑΒΓΔ  και  να
λάβωμεν  το  δεύτερον  σχήμα.  Τότε  το  πρόβλημα  ελύθη  και  η  εύθετα  ΓΗ  είναι  η
ζητουμένη πλευρά του διπλασίου κύβου, όταν η πλευρά του δοθέντος κύβου είναι η
ΔΘ∙  έχομεν  δε  παρεμβάλει  μεταξύ  των  δοθεισών  ευθειών  ΑΕ,  ΔΘ,  δυο  μέσος
ανάλογους τας ΒΖ, ΓΗ.

Απόδειξις: Προεκτείνομεν την ΑΔ μέχρις ότου αύτη συνάντηση την προέκτασιν
της ΕΘ εις τι σημείον Κ. Ένεκα των παραλλήλων ΒΖ, ΓΗ λαμβάνομεν:
ΑΚ: ΚΒ  =  Ε Κ: ΚΖ.4
Ένεκα των παραλλήλων ΑΖ. ΒΗ λαμβάνομεν:
ΑΚ:ΚΒ = ΖΚ:ΚΗ.
Είναι άρα:     ΑΚ:ΚΒ = ΕΚ:ΚΖ = ΖΚ:ΚΗ.  (1).
Ένεκα τον παραλλήλων ΒΖ, ΓΗ λαμβόνομεν:
ΒΚ:ΚΓ = ΖΚ:ΚΗ. Ένεκα των παραλλήλων ΒΗ, ΓΘ λαμθάνομεν:
ΒΚ:ΚΓ = ΗΚ:ΚΘ.
Είναι άρα:  Β Κ : Κ Γ =  ΖΚ:ΚΗ = ΗΚ:ΚΘ,  (2).
Εκ της (1) είναι :
ΕΚ:ΚΖ = ΖΚ:ΚΗ∙
εν ω εκ της (2) είναι:
ΖΚ:ΚΗ = ΗΚ: ΚΘ.
Είναι άρα  ΕΚ: ΚΖ = ΖΚ: ΚΗ ­ ΗΚ :ΚΘ.      (3),
Αλλά  ΕΚ:ΚΖ = ΑΕ:ΒΖ
ΖΚ:ΚΗ = ΒΖ:ΓΗ ΗΚ:ΚΘ = ΓΗ:ΔΘ.
Εκ τούτων, αντικαθιστώντας εις την (1) λαμβάνομεν:
ΑΒ:ΒΖ = ΒΖ : ΓΗ = ΓΗ: ΔΘ.
ήτοι αι ζητούμεναι δύο μέσαι ανάλογοι είναι αι ΒΖ, ΓΗ. Εάν καλέσωμεν:
ΑΕ = β = 2α,   ΒΖ = y,  ΓΗ= x,   Δθ = α,
έχομεν την ζητούμενην σχέσιν  x = 3 2 , κατά την αναγωγήν του Ιπποκράτους του Χίου.
Άλλο  μαθηματικόν  έργον  του Ερατοσθένους  μνημονεύει  ο  Πάππος (βιβλ.  7 σελ.
636. 24, F. Hultich) το περί μεσοτήτων, εις το οποίον εγίνετο διεύρυνσις των τριών
μεσοτήτων,  της  αριθμητικής,  της  γεωμετρικής  και  της  αρμονικής,  αι  οποίοι  είχον
μελετηθή υπό των Πυθαγορείων και αναφέρονται υπό του Πλάτωνος. Άλλαι πληροφορίαι
περί του θέματος τούτου θέν περιεσώθησαν.
Εντύπωσιν μεγάλην είχε κάμει κατά την αρχαιότητα∙ ή επινόησις του Ερατοσθένους
προς  εύρεστν  των  πρώτων  αριθμόν,  ή  όποια  διεσώθη  υπό  το  όνομα  Κόσκινον  του
Ερατοσθένους  (Νικόμαχου, Αριθμητική Εισαγωγή 1, 13 σελ. 29, Hoche). Δεν διεσώθη
όμως, εις ποίαν πραγματείαν του Ερατοσθένους περιλαμβάνεται το Κόσκινον. Η μέθοδος  αύτη είναι η εξής:
Αναγράφομεν  όλους  τους  περιττούς  αριθμούς  αρχίζοντες  από  3.  Κατόπιν
διαγράφομεν όλα  τα  πολλαπλάσια  του  τρία,  κατόπιν όλα  το  πολλαπλάσια του  πέντε, και γενικώς τα πολλαπλάσια του επομένου μη διαγεγραμμένου αριθμού:

3  5  7  9  11  13  15  17  19  21  … 

3  5  7  —  11  13  —  17  19  —  …
(Νικόμαχου  Αριθ. Είσαγ.  33,  16:  «οι  μεν  ουν  μηδαμως μετρηθεντες,  αλλά  διαφυγόντες   τούτο πρωτοί είσι και ασυνθετοι, ώς υπό κοσκινού διακριθέντες…».
Και  αστρονομικόν  έργον  είχε γράφει  ο Ερατοσθένης, το οποίον όμως δεν έσωθη.
Σπουδαιοτάτη είναι η «αναμέτρησις της γης» υπό του Ερατοσθένους, η μέτρησις δηλαδή
της περιμέτρου της γης θεωρούμενης σφαιρικής.
Περί τούτου παρέχει πληροφορίας ο Κλεομήδης  (Κυκλική θεωρία μετέωρων, 1.  10
σελ. 94. 24). Τη βοήθεια του βασιλέως Πτολεμαίου, όστις έθεσεν εις την διάθεσιν τού
Ερατοσθένους  το  Σώμα  των  βηματιστών,  προς  μέτρησιν  αποστάσεων,  ο  Ερατοσθένης  εμέτρησε  την  απόστασιν  Συήνης  (σημερινού  Ασσουάν)  —  Αλεξανδρείας  και  εύρεν  υτήν 5000 στάδια αναχωρήσας από την σκέψιν ότι Αλεξάνδρεια — Συήνη ευρίσκονται
επί του αυτού μεσημβρινού.
Είχε  βεβαιωθή  προηγουμένως  υπό  του  Ερατοσβένους  (διά  διανοίξεως  μικρού
φρέατος,  κληρωθέντος  κατά  το  ήμισυ  βάθος  δι’  ύδατος)  ότι  αι  ακτίνες  του  ήλιου
προσέπιπτον εν Συήνη κατακορύφως  κατά την  μεγαλυτέραν ημέραν  του  έτους,  την  21  Ιουνίου.  Κατά  την  αυτήν  ημέραν  αι  ακτίνες  του  ηλίου,  εις  την  Αλεξάνδρειαν,
έσχημότιζον  μετά  της  κατακόρυφου  του  τόκου  γωνίαν  ίσην  προς  το  1/50  της
περιφερείας κύκλου. Ο Ερατοσθένης έκαμεν ακολούθως την απλήν σκέψιν ότι, αφού
εις  το  1/50  της περιμέτρου  αντιστοιχούν  5000  στάδια,  εις  τα  50/50   πόσα στάδια θα  αντιστοιχούν  και  εύρε  250000 στάδια.  Κατ’ άλλας  πληροφορίας  είχε  εύρει  252.000  στάδια. Δεν  είναι  ακριβές  το  μήκος  του  σταδίου  εις  μέτρα  με  το  οποίον  έκαμε  τους   υπολογισμούς  του ο Ερατοσθένης. Το στάδιον  της Ελληνιστικής αποχής ήτο ίσον με   157,5 μέτρα. Συμφώνως προς το μήκος του  σταδίου  τούτου  το  μήκος  της  περιμέτρου
της γης ευρεθείσης 252000 στάδια είναι ίσον μπρος 39.690 χιλιόμετρα.

Αι   μέτρησης των   νεωτέρων  φέρουν  τούτο  ίσον  προς  40000  χιλιόμετρα  περίπου.  Η  μέτρησις  της  περιμέτρου  της γης υπό  του Ερατοσθένους  έχει προκαλέσει  τον γεννικόν θαυμασμόν  διά την πρωτοτυPείαν και την απλότητα της. Και περί της οκταετηρίδος είχεν ασχοληθή ο  Ερατοσθένης (περί διορθώσεως του ημερολογίου διά της παρεμβολής μετά πάροδον 9 ετών  ήμερων τίνων» χωρίς όμως να  έχωμεν επί τούτου συγκεκριμένας πληροφορίας.
Αλλά  και  εις  την  θεωρίαν  της  μουσικής  είχε  διακριθή  ο  Ερατοσθένης,  ως
συνάγεται, εκ των ελαχίστων διασωθεισών πληροφοριών μεταγενεστέρων ανγγραφέων.6
Ήτο  σύγχρονος  και  φίλος  του  Αρχιμήδους,  ο  οποίος  τον  είχεν  εις  μεγάλαν
εκτίμησιν.  Ο  Αρχιμήδης  είχεν  αφιερώσει  εις  τον  Ερατοσθένην  την  σπουδαιοτάτην
εργασίαν  του,  την  φέρουσαν  τον  τίτλον  «Αρχιμήδους  Περί  των  μηχανικών
θεωρημάτων προς Ερατοσθένην έφοδος» ( = μέθοδος), την ανευρεσείσαν μόλις κατά το
1906  εις  την  βιβλιοθήκην  του  εν  Κωνσταντινούπολη  Μετοχίου  του  Παναγίου  Τάφου.  Γράφει  λοιπόν  εκεί  ο  Αρχιμήδης  «…  βλέπων  δε  σε, ως  έχω  ήδη  είπει,  σπουδαίον  και  αξιολόγως προεξάρχοντα  κατά  την φιλοσοφίαν  και  έχοντα  τιμήσει  την  μαθηματικήν  έρευναν κατά την περίστασιν, έκρινα ορθόν να σου εκθέσω εις το αυτό βιβλίον και να
καθορίσω μέθοδόν  τινά, η οποία θα  σου  επιτρέπη να λαμβάνης  αφορμάς  ώστε  να  δύνασαι  μερικάς προτάσεις να τας εξετάξης διά της μηχανικής».
Αλλά και το περίφημον βοεικόν πρόβλημα του, ο Αρχιμήδης το απέστειλεν εις τους
εν Αλεξανδρεία φίλους του  δια  του  Ερατοσθένους, ως  φαίνεται  εκ  της  επιγραφής  του  προβλήματος, η οποία έχει ως έξης:

Πρόβλημα
Όπερ  Αρχιμήδης  εν  επιγράμμασιν  ευρών  τοίς  εν  Αλιεξανδρεία  περί  ταύτα
πρατματευομένοις  ζητείν  απέστηλεν  εν  τη  προς  τον  Ερατοσθένην  τον  Κυρηναίον
Επιστολή.  (Ιδέ  Άρχιμήδους  Άπαντα,  τόμος  Β’.  Αθήναι  1973,  σελίς  468,  υπό  Ευ.  Ι.
Σταμάτη, έκδοσις Τεχνικού Επιμελητηρίου της Ελλάδος).
Κατά  τους  νεωτέρους,  (Amchor)  ο  εις  εκ  των  αγνώστων  του  προβλήματος,  όταν
ευρεθή  θα  κατέχη  πολλάς  σελίδας  ψηφίων,  και  διά  να  γραφούν  τα  ψηφία  των  8
άγνωστων χρειάζεται τόμος 660 σελίδων, όπου έκαστη σελίς  θα  έχη  50  στίχους  με  50  ψηφία έκαστον!

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ARITHMETICS – ΑΡΙΘΜΗΤΙΚΑ – АРИТМИТИКА

The origin of numbers. Counting without numbers. “Natural” number systems.
Introduction

It is often said that the essential tools for life are reading, writing and arithmetic. While this may not have been true for most people until very recently in history, it is certainly true for science. A moment’s reflection will also show that the most basic of the three tools is arithmetic: Writing may allow the science-priests to hand on their knowledge to future generations, who can absorb it through reading; but without the means of quantification the best science does not make much progress. The need to be quantitative varies of course from discipline to discipline, but even an essentially descriptive science such as taxonomy has to make quantitative statements about sizes and life spans. A history of science therefore has to begin with the question: Why did people invent numbers? To find the answer we follow George Ifrah’s Universal History of Numbers (Ifrah, 2000).

The invention of the modern number system is such a stroke of human genius that it is worth a detailed discussion. Its development. can be described as a passage through four stages:

  1. Grasping quantities
  2. Counting without numbers
  3. Using absolute number systems to count and calculate
  4. Using place-value number systems to calculate with pen and paper or calculator
Grasping quantities

We begin with the question: Do you need numbers to count? Framed in a different way, we may ask: If we are shown a group of identical objects, can we tell how many objects we see without counting?

It is known from observation and experiment that animals cannot count, but some animals can grasp quantities to a limited extent. An interesting anecdote about a French nobleman reports that he tried to rid himself of a raven that lived in the tower of his castle, but every time he approached the tower the raven flew to a nearby tree and waited until the nobleman had left. The nobleman sent two of his servants out and told them to enter the tower together; one of them should then leave, while the second servant should wait in the tower for the raven’s return. The raven was not fooled and waited until two persons had left the tower. The nobleman repeated the exercise with three of his men, then with four. The raven always waited until all men had left. But when five men entered the tower and four left, the raven could no longer grasp the difference and returned. (Dantzig, 1931)

This observation shows that the ability of animals to grasp the number of objects in a group without counting is quite limited. That the same is true for humans can easily be demonstrated with a simple test, which you should do at this point before reading on.

Compare your own data with the correct sequence(2 4 9 1 7 5 9 2 8 3 1 6 4 7 6 3 8 5)

You will find that the largest number the human brain can comprehend without counting or guessing is 4. Beyond that most people can identify 5 elements in a group by quickly counting them; everything beyond 5 can only be a guess, unless there is enough time for a count.

We can make the statement about the test result more scientific by giving it to a group of people and looking at the aggregate performance. I gave the test to two groups of “University of the Third Age” students, where the average age was well over 65, and to two groups of secondary school students and plotted the results. The graph shows (

test results



Here are the results from four classes that took the test. The curves show the percentage of students that recognized the quantity shown on the slide correctly. Blue curves are from classes of people 65 years of age and older, red curves are from classes of high school students. The n values indicate the sample size (people in each class).

The results show that virtually all students recognize quantities up to 4 or 5 correctly. (The high school students were less organised than the senior students; some missed the first few slides, which explains their performance slightly below 100% for small quantities.) For larger quantities the success rate falls off rapidly irrespective of age.

) that the accuracy of the result deteriorates quickly for numbers larger than 5 and that this is true regardless of age.

At the hunter-gatherer stage people had no need to count and invented words only for quantities that could be grasped without counting. Languages of such a society therefore had names only for the quantities one, two, three and four; everything beyond that was “many.” Examples for such a situation can still be found today where the hunter-gatherer society survives; they are (among others) the Aranda of Central Australia, the people of the Murray Islands in Torres Strait north of Australia, the Indians of Brazil and in Tierra del Fuego, the Abipón of Paraguay and the Bushmen of Africa. The Australian examples may stand here for all:

image

Such languages are often called primitive languages. This is correct in the sense that they represent a development of human society before the onset of civilization. It would, however, be extremely misguided to think that the people of today are intellectually superior to the people of the Neolithic age. The species Homo sapiens did not evolve significantly since the stone age, and as our test showed our ability to grasp quantities beyond 4 is the same as the ability of the hunter-gatherers of old. As our investigation progresses we shall see that the average Neolithic man or woman would not have any difficulty at all to catch up with our civilization within less than one generation. Every society develops the tools needed for its everyday activities. Egalitarian societies in which no person owns anything much and land is communally held have no need to count. If today’s hunter-gatherers do not count beyond 4 that only proves that they have no need for it.

Counting without numbers

If primitive societies have no need to count and therefore do not develop names for numbers beyond 4, when did the need to count arise? It could not have been the large numbers of animals in a herd – the Australian Aborigines also encountered many kangaroos during their hunting trips and were satisfied to say that there were many kangaroos, enough to satisfy their need for food and clothing. The need to establish the exact number of animals in a herd arises as soon as this herd becomes private property and can be traded.

Does the owner of the herd need words for numbers beyond 4 to be able to count his animals? Consider this problem: The owner of the herd asks you to deliver 40 head of sheep to a friend of his and return proof of delivery. He hands you a clay container, sealed with his personal stamp, containing 40 pebbles.

His friend will open the container and count the sheep by picking up one pebble for every sheep. He will then give you a receipt, for example a clay tablet with his personal stamp. By handing over the clay tablet to the vendor you can offer proof that you delivered 40 head of sheep as asked. Nobody involved in the transaction has to know the names of any numbers or be able to count. Evidence that this method of “counting” was widespread through several millennia is found in excavationsfrom Mesopotamia and retained in the English language: Calculus is Latin for “pebble”, so to calculate means “to move pebbles.”

This method, sometimes called counting by association, works fine as long as the number of sheep is not too large. How do you use pebbles to count very large numbers? You introduce pebbles of different shape. This system of counting was in use in many early societies of all continents.

Number systems

To associate pebbles of different shape with different values requires a number system. Our modern number system, known as the decimal system, uses the base 10, so we would use different pebbles for 1, 10, 100, 1000 etc.

Is there a “natural” number system? The usual response to that question is: “Of course; 10, because we have 10 fingers.” All evidence shows that when humans begin to count they use their fingers, so using body parts as a base for a number system does indeed come naturally. Nevertheless, the usual answer is a good example of cultural bias. When I visited Ocean University of Qingdao in China in the 1980s and 1990s I did not speak Chinese, but I quickly learnt how people in China indicate numbers with only one hand – they can indicate any number with five fingers by forming shapes with their fingers, rather than using the second hand to lift one finger at a time to indicate 6, 7, 8 etc.

The practice of counting on one hand was in use in Europe until at least 1600. Calculation tutorials from the time were not considered exhaustive if they did not include a description of the finger counting method. The method is superior to our way of counting with ten fingers in several respects. Anyone who has observed the activity in a noisy stock exchange has seen brokers signalling numbers across the room with two hands. The Chinese method allows the use of only one hand and leaves the other free for the mobile phone.

There are several ways to use your fingers for counting. A method still widely practiced in the Middle East uses the thumb to point to different parts of each finger. Each finger can be used to indicate three numbers, so the four fingers of one hand cover the numbers 1 – 12. This produces the number 12 as an alternative base for a “natural” number system, known as theduodecimal system.

A logical extension of the duodecimal system is the sexagesimal system, which uses the base 60. It uses one hand to count from 1 to 12 and the other hand to indicate the multiples of 12.

Yet another “natural” number system developed in regions of benign climate where people do not wear shoes and therefore can also use their toes for counting. This produces the vigesimal system, a system with the base 20.

We notice that the question what is “natural” does not have an easy answer. Even tday we can find evidence for a range of number systems. Some people were content to use only one hand for counting to five; their quinary system used the base 5. This system survived in the language of the Api from Vanuatu in the South Pacific. They use the decimal system today, but their names for the numbers 1 – 10 are

image

Evidence for the use of the duodecimal system during some developmental stage of science survives in most European languages. The normal construction of numbers larger than 20 in the English language is twenty-one, twenty-two, twenty-three etc. A similar system is used for the numbers 13 – 19: Three-ten (thirteen), four-ten (fourteen), five-ten (fifteen) etc. But the two numbers 11 and 12 have their own names, eleven and twelve, which are not composites such as twenty-eight or thirteen. The same “anomaly” occurs in the German, French and other languages.

Evidence for the use of the sexagesimal system survives in the French language. French names for numbers follow the normal decimal construction up to sixty (soixante) and continue on in the normal way sixty-and-one (soixante-et-un), sixty-two (soixante-deux), sixty-three (soixante-trois) and so on up to sixty-nine (soixante-neuf). But the numbers then continue as sixty-ten (soixante-dix), sixty-eleven (soixante-onze), sixty-twelve (soixante-douze) etc. The system returns to normal decimal counting at 100.

The following table shows which number systems have been in use in different parts of the world. It is evident that today’s decimal system is only one of several options. It has certain advantages over the sexagesimal system, which will become evident in the next lecture, but is not superior to any of the other systems. Its use today is more the result of historical accident than inherent advantage.

number systems used by different societies.

image

 

Summary

The next lecture will discuss how different civilizations developed writing systems for numbers. It will build on the outcome from this lecture, so let us summarize the essential points:

  • The ability of the human brain to comprehend quantities without counting is limited to 4 or 5 items.
  • This ability is the same in any human society, from hunter-gatherer to modern urban populations.
  • The need to develop methods for counting did not exist until some individuals acquired large personal wealth in early husbandry societies.
  • The invention of numbers is not the result of general curiosity but the answer to a problem that occurred with the accumulation of wealth during the development of society.
  • Different civilizations used different number systems. All were based on the use of the human body for counting.
Reference

Dantzig, T. (1930) Number, the language of science. London.

Ifrah, G. (2000) Universal History of Numbers. John Wiley & Sons. Translated from Ifrah, G. (1981) Histoire Universelle des Chiffres, (Seghers).

 

SOURCE  http://www.es.flinders.edu.au/

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