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Pogonska raketa je naredila krater in oblak materiala, skozi katerega je nato letela sonda. Zadetek pogonske rakete je bil sicer veliko manj veliËasten, kot so priËakovali, in ga tudi skozi najveËje zemeljske teleskope niso zaznali. Je pa sonda uspešno opravila svoje delo, saj so vsi inštrumenti delovali zelo zanesljivo in zajeli zelo veliko koliËino podatkov. Ker je podatkov ogromno, bomo na rezultate morali še nekaj Ëasa poËakati. Vsekakor pa smo lahko prepriËani, da v kraterju, v katerega se je zaletela sonda, ni zelo velike koliËine vode, saj bi jo takoj zaznali in o tem hitro obvestili javnost. Vsekakor pa bodo rezultati odprave zelo pomembni, saj nam bodo dali tudi mnogo drugih podatkov o Luninem površju in njegovi sestavi.
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Editorial Tomaž Sajovic Geophysics Centennial of the Discovery of the MohoroviËiÊ Discontinuity Andrej Gosar Datum: 15. 11. 2009. »as: 21:00. Kraj: Ljubljana.
The Croatian seismologist Andrija MohoroviËiÊ discovered an important velocity discontinuity between the Earth’s crust and the mantle when he analyzed seismograms of the earthquake which occurred one hundred years ago (on 8 October 1909) in the Kolpa Valley. This boundary was later named the MohoroviËiÊ discontinu-
ity. He discovered two types of P and S wave arrivals at the epicentral distances between 300 and 720 km. The first arrivals visible on seismograms are Pn and Sn phases, which correspond to a longer, refracted, but faster path through the upper part of the mantle. Later Pg and Sg phases correspond to direct waves propagating only through the Earth’s crust, which is characterized by lower seismic velocities. Newer investigations have shown big differences in the depth of the MohoroviËiÊ discontinuity below Slovenia with some surprising jumps in transition zones.
Evolution Evolution of the Silver Sword or Darwin’s Legacy in Hawaii Marina Dermastia Hawaiian vegetation represents a true Darwin’s workshop of evolution. It extends from the lush tropical rainforest on the oldest island, Kauai, to the almost out of this world, black landscape dominated by volcanoes on Big Island at the other end of this island chain. Only occasionally and bashfully do plants take root in the cold lava on Big Island. However, there is something that all of the islands have in common − unique and unusual plants growing among those that are commonly known and were introduced to the island from elsewhere. Even a lay person cannot overlook the plants whose shoots take very different shapes on different islands. Despite this life-form diversity, they all have compact inflorescences (heads) − pseudanthiums. The silversword alliance comprises 30 perennial species in three endemic genera: Argyroxiphium, Dubautia and Wilkesia that represent an independent evolutionary line within the Asteraceae family (tribus Madiinae). The silversword alliance was named after its representative Silver Sword (Argyroxiphium sandwicense). In his notes on transmutations Darwin already correctly considered Hawaiian plants ideal for the study of evolution of plant forms and new species. The silversword alliance has a special place among these plants. Today we know that this alliance evolved by adaptive radiation in extremely diverse habitats of different Hawaiian islands and is a true Rosetta stone for understanding the origin of plant morphological diversity. Nature Conservation Okrešelj − a Nature Conservation Driven Acquisition? Tomaž PoliËnik In 1931 the Savinja branch of the Slovenian Alpine Society bought the Okrešelj area in the Logar Valley (Logarska dolina). It was supposed to be a nature conservation driven acquisition, as there were some subsequent efforts to establish a Logarska dolina − Okrešelj national park. However, the documentation shows that the original motives for the acquisition of Okrešelj had been of a different kind. By buying land in the Logar Valley before WW1 the Savinja branch tried to keep the ownership of Slovenian land in Slovenian hands. The very idea of the acquisition of Okrešelj dates into the end of the 19th century, but the Ljubljana diocese refused to sell the land at the time. The original motive for the acquisition of the Okrešelj area was therefore not nature conservation, but preservation of national identity. It was not until the acquisition in 1931 that nature conservation tendencies came to the fore. That was when members of the Savinja branch of the Slovenian Alpine Society were trying to organize a national park. When the regulation on national parks was out in 1938 they were determined to establish a national part in this area. Physics Light Reflection on the Ljubljanica River Hans-Joachim Schlichting A look under the Ljubljanica bridges reveals a stunning play of diffuse and specular reflection. A visitor to the Slovenian capital is standing with his back to the Sun on the first of the three bridges across the Ljubljanica. The camera lens is focused on the water surface under the second bridge. You can see an astonishing play of shadows that ends at the overexposed arch of the second bridge above, and below with its reflection on the Ljubljanica. Obviously the greenish substances floating under the surface reflect the sunlight diffusely, which means the light is scattered in all directions. Where the first bridge and its parapet block the sunlight they cut light gaps with their shape, thus creating an outline of its shadow in the turbid water. However, also the specular reflection plays a role here. It dominates when the objects reflected are bright enough. Here, the incident angle at which the light hits the surface equals the reflective angle. Both kinds of reflections interact in fascinating phenomena. Nobel Prize in Physics 2009 Nobel Prize in Physics Janez Strnad Half of this year’s Nobel Prize in physics went to Charles K. Kao for “groundbreaking achievements concerning the transmission of light in fibers for optical communication”. The other half was divided between Willard S. Boyle and George E. Smith “for the invention of an imaging semiconductor circuit − the CCD sensor”. The first half of the prize is about communication transmission, while the other has to do with the way we obtain an image and what we do with it.
In memoriam To Professor Miroslav Kališnik, PhD 8 April 1927 − 10 March 2009 Metka Zorc
Nature photography Dušan Klenovšek − Naturalist, Conservationist and Nature Photographer Hrvoje Teo OršaniÊ New books Ljubljana Moor. Non-living world, flora, fauna, history and nature conservation Andrej Seliškar Readers’ letters
Our sky Water on the Moon Mirko Kokole
■ Geofizika
MohoroviËiÊevo odkritje hitrostne diskontinuitete med Zemljino skorjo in plašËem je bilo zelo pomembno za nadaljnji razvoj seizmologije in geofizike. Pravi pomen tega odkritja se je pokazal šele mnogo pozneje, ko so v šestdesetih letih dvajsetega stoletja oblikovali teorijo tektonike plošË. Takrat so tudi spoznali, da je razumevanje globalnih tektonskih procesov kljuË za razumevanje geološke zgradbe strukturno zapletenih sistemov, kakršni so Alpe, Andi ali Himalaja. V iskanju energetskih virov in mineralnih surovin je Ëlovek posegal tudi vedno globlje v Zemljino skorjo. Hkrati je razvoj aktivnih geofizikalnih metod omogoËil, da so se po celem svetu zaËele intenzivne raziskave globokih delov skorje in strukture MohoroviËiÊeve diskontinuitete, ki trajajo še danes.
■ Evolucija
Evolucija srebrnega meËa ali Darwinova zapušËina na Havajih
Rastlinstvo na Havajih pomeni pravo Darwinovo delavnico evolucije ∑ od bogatega tropskega deževnega gozda na najstarejšem Kauaiju do skoraj nezemeljsko puste, Ërne in z vulkanskimi kraterji razbrazdane pokrajine najmlajšega Velikega otoka na drugem koncu otoške verige. Med rastlinami, ki so nam poznane in so bile seveda na otoke prinešene, opazimo primerke edinstvenih in nenavadnih oblik. Med njimi tudi nepoznavalec ne more zgrešiti rastlin, ki imajo na razliËnih otokih zelo razliËno oblikovane poganjke. Kljub temu pa so vsem skupna glaviËasta socvetja košarnic ∑ koški. Gre za približno trideset vrst iz treh endemiËnih rodov: Argyroxiphium, Dubautia in Wilkesia, ki tvorijo samostojno evolucijsko linijo znotraj nebinovk (družina Asteraceae, tribus Madiinae). Gre za skupino srebrnega meËa, ki je svoje ime dobila po predstavniku srebrnem meËu (Argyroxiphium sandwicense). Kot je pravilno razmišljal že Darwin, so havajske rastline idealne za preuËevanje razvoja rastlinskih oblik in novih vrst. Med temi rastlinami ima skupina srebrnega meËa prav posebno mesto. Danes vemo, da se je ta skupina z adaptivno radiacijo razliËno razvijala v zelo razliËnih življenjskih prostorih posameznih havajskih otokov in je pravi kamen iz Rosette za razumevanje izvora rastlinske morfološke raznolikosti.
