| Vacuum_Tube_Diode A demonstration of how a vacuum tube diode works. |
| The_Van_de_Graaff_Generator_Website This site includes information on how Van de Graaff Generators work, typical classroom demonstrations, and instructions for building one. |
| VRML_Gallery_of_Electromagnetism Visualization of the electromagnetic field. |
| Wireless_Lab_at_Nizhny_Novgorod_University Laboratory of Physical Fundamentals and Technologies of Wireless networks at Nizhny Novgorod State University, Russia. |
| Wondermagnet_com Images of magnets and their uses, experiments, a discussion board about magnet-related topics, and an elementary primer on magnetism and magnetic physics. |
| X-ray_Optics_and_Microscopy_at_Stony_Brook Research describing use of coherent soft X-rays for optics experiments, including Fresnel zone plates, to produce the smallest focused spot of electromagnetic waves for studies of biological and mater |
| NSSDC__Venus From NASA's photo gallery. |
| Planet_Venus_-_overview_and_pictures Illustrated guide to Venus. Contains description, facts, statistics and a brief history. |
| Venus From The Nine Planets. |
| Venus NASA's Windows to the Universe. |
| Venus Details on this planet. |
| Venus From "Views of the Solar System". |
| Venus Facts, early knowledge and history of man's exploration of Venus. |
| Venus_Basic_Information Summary articles and related links. |
| Venus__Earth\'s_troubled_sister Although it looks a lot like Earth, it's actually dramatically different. |
| Welcome_to_the_Planets__Venus Planetary profile and vital statistics, some pictures. |
| ACalendar_com The calendar has many options with a standard monthly interface, including sunrise, sunset, and Moon phases. |
| Annus_Novus_Decimal_Calendar A proposal for a non-sectarian, culturally neutral calendar system. |
| Astro_Portal_-_CalSKY The worldwide interactive online astronomical/space calendar and calculator - for friends of astronomy, as well as astronomers. |
| Astronomical_Time_Keeping Extensive descriptions of many astronomical time keeping systems, with information on time zones and Julian day numbers. |
| Astronomy_by_JavaScript__Sun_Calculators_and_More Applets related to calendars and keeping time, including sidererial time. |
| Astronomy_Calendar Features different views of the night sky, constellations, stars, planets, and other celestial wonders. |
| Blue_Moon_Myths Second full moon in a month, or third full moon in a single season? |
| Britannica_com_-_Clockworks__From_Sundials_to_the_Atomic_Second Britannica.com explores the history of timekeeping, from sundials to cesium atomic clocks. |
| The_Calendar,_Leap_Years_and_the_Year_2000 An explanation of the calendar including the origin of the day, week, month and year. |
| Calendar_Studies Articles on the Gregorian and Julian calendars, the ISO date format, the Julian day number system, the Maya calendar, the Goddess lunar calendar, the Liberalia Triday Calendar and C functions for date |
| Calendars_through_the_Ages History and FAQs of calendars, from ancient Rome to outer space. Including Julian, Gregorian, Jewish, Islamic, Chinese, and Mayan. |
| Calendopaedia The Encyclopaedia of Calendars. |
| Calendrical_Calculations Published by Cambridge University Press. Gives a unified algorithmic presentation of the Gregorian, ISO, Julian, Coptic, Ethiopic, and Islamic civil calendars. |
| The_Chinese_Calendar The mathematics of the Chinese calendar. Explains the rules for the Chinese calendar. |
| The_Difference_Between_the_Millennium_and_Year_2000 Questions and answers to satisfy the hearts of true millennium buffs. |
| Greenwich_Time__Home_of_World_Time_(GMT)_since_1884 Complete guide to times in every time zone in the world. |
| Hindu_Calendar_Dates_52nd_Century Explains the cosmological and astronomical influences in creating the Indian calendar. |
| Indian_Moons A list of many American Indian tribe's names for months, days, and other calendar related information. |
| The_Islamic_Calendar The mathematics of the Islamic calendar in Singapore. |
| The_Julian_and_Gregorian_Calendars Explanations of the Julian Calendar, the Gregorian Reform, the adoption of the Gregorian Calendar, the length of the tropical year and related matters. |
| Julian_Day_Numbers An explanation of the Julian day number system used by astronomers and calendricists. |
| Leap_Seconds Civil time is occasionally adjusted by one second increments called leap seconds. A detailed explanation of what a second actually is, and why leap seconds are necessary. |
| LunarCal_-_A_Perpetual_Chinese_Lunar_Calendar LunarCal is a 160-year perpetual Chinese Lunar Calendar for 1900 to 2060. Chinese festivals are listed and the moon phase is displayed. |
| Lunisolar_Calendar Lunar calendar with lunations, from new moon to new moon, instead of months. Moon phase on each day. Chinese, Jewish, and Islamic months. Eclipses, meteors, planets, star charts. Christian, Pagan, Isl |
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Number 476 (Story #1), March 24, 2000 by Phillip F. Schewe and Ben SteinTOPSY TURVY: THE FIRST TRUE "LEFT HANDED" MATERIAL has been devised by scientists at the University of California at San Diego. In this medium, light waves are expected to exhibit a reverse Doppler effect. That is, the light from a source coming toward you would be reddened and the light from a receding source would be blue shifted. The UCSD composite material, consisting of an assembly of copper rings and wires (see figure at Physics News Graphics), should eventually have important optics and telecommunications applications. To understand how a reverse Doppler shift and other bizarre optical effects come about, consider that a light wave is a set of mutually reinforcing oscillating electric and magnetic fields. The relationship between the fields and the light motion is described picturesquely by what physicists call the "right hand rule": if the fingers of the right hand represent the waves' electric field, and if the fingers curl around to the base of the hand, representing the magnetic field, then the outstretched thumb indicates the direction of the flow of light energy. Customarily one can depict the light beam moving through a medium as an advancing plane of radiation, and this plane, in turn, is equivalent to the sum of many constituent wavelets, also moving in the same direction as the energy flow. But in the UCSD composite medium this is not the case. The velocity of the wavelets runs opposite to the energy flow (an animated video illustrates this concept nicely, and this makes the UCSD composite a "left handed substance," the first of its kind. Such a material was first envisioned in the 1960's by the Russian physicist Victor Veselago of the Lebedev Physics Institute (Soviet Physics Uspekhi, Jan-Feb 1968), who argued that a material with both a negative electric permittivity and a negative magnetic permeability would, when light passed through it, result in novel optical phenomena, including a reverse Doppler shift, an inverse Snell effect (the optical illusion which makes a pencil dipped into water seem to bend), and reverse Cerenkov radiation. Permittivity (denoted by the Greek letter epsilon) is a measure of a material's response to an applied electric field, while permeability (denoted by the letter mu) is a measure of the material's response to an applied magnetic field. In Veselago's day no negative-mu materials were known, nor thought likely to exist. More recently, however, John Pendry of Imperial College has shown how negative-epsilon materials could be built from rows of wires (Pendry et al., Physical Review Letters, 17 June, 1996) and negative-mu materials from arrays of tiny resonant rings (Pendry et al., IEEE, Trans. MTT 47, 2075, 1999). Now, this week, at the American Physical Society meeting in Minneapolis, Sheldon Schultz and David Smith of UCSD reported that they had followed Pendry's prescriptions and succeeded in constructing a material with both a negative mu and a negative epsilon, at least at microwave frequencies. The raw materials used, copper wires and copper rings, do not have unusual properties of their own and indeed are non-magnetic. But when incoming microwaves fall upon alternating rows of the rings and wires mounted on a playing-card-sized platform and set in a cavity, then a resonant reaction between the light and the whole of the ring-and-wire array sets up tiny induced currents, which contribute fields of their own. The net result is a set of fields moving to the left even as electromagnetic energy is moving to the right. This effective medium is an example of a "meta-material." Another example is a photonic crystal (consisting of stacks of tiny rods or solid material bored out with a honeycomb pattern of voids) which excludes light at certain frequencies. At a press conference in Minneapolis, Schultz (sschultz@ucsd.edu) and Smith (drs@sdss.ucsd.edu) said that having demonstrated that their medium possessed a negative mu and epsilon, they were now proceeding to explore the novel optical effects predicted by Veselago. Furthermore, they hope to adapt their design to accommodate shorter wavelengths. As for applications in microwave communications, a medium which focuses waves when other materials would disperse them (and vice versa) ought to be useful in improving existing delay lines, antennas, and filters. Outside commentators at the press conference showed interest and curiosity. Marvin Cohen of UC Berkeley said that until he read the UCSD paper (Smith et al., Physical Review Letters, 1 May; science writers should go to Physics News Select) he had not thought a negative-mu material was possible. Walter Kohn of UC Santa Barbara (winner of the 1998 Nobel Prize in chemistry) considered the UCSD work "...an extremely interesting result. I would be surprised if there weren't interesting applications." 