Eugene Merle Shoemaker
Eugene Merle Shoemaker known as Gene Shoemaker, was an American geologist and one of the founders of the field of planetary science. He is best known for co-discovering the Comet Shoemaker–Levy 9 with his wife Carolyn S. Shoemaker and David H. Levy; this comet hit Jupiter in July 1994: the impact was televised around the world. Shoemaker was well known for his studies of terrestrial craters, such as Barringer Meteor Crater in Arizona. Shoemaker was the first director of the United States Geological Survey's Astrogeology Research Program. Shoemaker was born in Los Angeles, the son of Muriel May, a teacher, George Estel Shoemaker, who worked in farming, business and motion pictures, his parents were natives of Nebraska. During Gene's childhood they moved between Los Angeles, New York City, New York and Wyoming, as George worked on a variety of jobs. George hated living in big cities, was quite satisfied to take a job as director of education for a Civilian Conservation Corps camp in Wyoming, his wife soon found life in a remote cabin quite unsatisfactory.
They compromised. She could teach in the Buffalo School of Practice of the State Teachers College at Buffalo during the school year while keeping Gene with her both would return to Wyoming during the summers. Gene's passion for studying rocks was ignited by the science education courses offered by the Buffalo Museum of Education, he enrolled in the School of Practice in the fourth grade, began collecting samples of minerals. Within a year, he was taking high-school-level evening courses; the family moved back to Los Angeles in 1942, where Gene enrolled in Fairfax High School at the age of thirteen. He completed high school in three years. During that time he played violin in the school orchestra, excelled in gymnastics, got a summer job as an apprentice lapidary. Gene enrolled in the Caltech at the age of sixteen, his classmates were older, more mature and on a fast track to graduate before serving in World War II. Gene earned his bachelor's degree in 1948, at age nineteen, he undertook the study of Precambrian metamorphic rocks in northern New Mexico, earning his M. Sc. degree from Caltech in 1949.
While Shoemaker was attending Caltech, his roommate was Richard Spellman, a young man from Chico, California. Although Shoemaker had enrolled in a doctoral program at Princeton University, Gene returned to California, to serve as best man at Richard's wedding in 1950, he met Richard's sister, for the first time on that occasion. Carolyn had been born in Gallup, New Mexico in 1929, but the Spellman family had moved to Chico soon afterward. Carolyn had earned degrees from Chico State College in history and political science, she had never exhibited any interest in scientific subjects while growing up, had taken one geology course in college, which she had found quite boring. The couple formed a "pen pal" relationship while Gene spent the next year in Princeton, followed by a two-week vacation touring the Colorado Plateau, she told others that,"listening to Gene explaining geology made what she had thought was a boring subject into an exciting and interesting pursuit of knowledge." The couple married on August 17, 1951.
The Shoemakers had three children: one son. Carolyn saw her work as keeping house and raising the children after they settled in Flagstaff in the 1960s, she had tried teaching school before they found the work unsatisfying. She traveled sometimes with Gene, but stopped after she noticed that her absence affected the children. After their children were grown, Carolyn wanted something meaningful to combat the "empty nest" feeling. By Gene Shoemaker suggested that she take up astronomy and join his team looking for asteroids approaching Earth. A student working at Lowell Observatory commenced teaching her astronomy, she showed great potential and launched her career as a planetary astronomer at age 51. She continues the work to the present; the United States Geological Survey hired Shoemaker in 1950. His first assignment was to search for uranium deposits in Colorado, his next mission was to study volcanic processes, since other investigators had noticed that uranium deposits were located in the vents of ancient volcanoes.
This study led him to explore the Hopi Buttes of Northern Arizona, which happened to be near Meteor Crater. Daniel Barringer, an entrepreneur and mining engineer who had discovered Meteor Crater in 1891, had postulated that it had been caused by the impact of a meteor. About the same time, G. K. Gilbert, the chief geologist of the USGS, examined the crater and announced that it had been created by an explosive venting of volcanic steam. A majority of scientists accepted Gilbert's explanation of the cause of the crater, This theory remained as conventional wisdom until Shoemaker's investigations a half century later. For his Ph. D. degree at Princeton, under the guidance of Harry Hammond Hess, Shoemaker studied the impact dynamics of Barringer Meteor Crater. Shoemaker noted Meteor Crater had the same form and structure as two explosion craters created from atomic bomb tests at the Nevada Test Site, notably Jangle U in 1951 and Teapot Ess in 1955. In 1960, Edward C. T. Chao and Shoemaker identified shocked quartz at Meteor Crater, proving the crater was formed from an impact generating high temperatures and pressures.
They followed this discovery with the identification of coesite within suevite at Nördlinger Ries, proving its impact origin. In 1960, Shoemaker directed a team at the USGS center in Menlo Park, California, to generate the first geol
Pease is a lunar impact crater that lies in the north-northwestern edge of the huge skirt of ejecta that surrounds the Mare Orientale impact basin. It lies just over one crater diameter to the east of the smaller crater Butlerov. To the east-northeast of Pease is the somewhat larger Nobel; this is a circular, bowl-shaped formation with an outer rim, only moderately eroded. No significant craters lie across the interior. There is a slight straightening of the western rim
A reflecting telescope is a telescope that uses a single or a combination of curved mirrors that reflect light and form an image. The reflecting telescope was invented in the 17th century, by Isaac Newton, as an alternative to the refracting telescope which, at that time, was a design that suffered from severe chromatic aberration. Although reflecting telescopes produce other types of optical aberrations, it is a design that allows for large diameter objectives. All of the major telescopes used in astronomy research are reflectors. Reflecting telescopes come in many design variations and may employ extra optical elements to improve image quality or place the image in a mechanically advantageous position. Since reflecting telescopes use mirrors, the design is sometimes referred to as a "catoptric" telescope; the idea that curved mirrors behave like lenses dates back at least to Alhazen's 11th century treatise on optics, works, disseminated in Latin translations in early modern Europe. Soon after the invention of the refracting telescope, Giovanni Francesco Sagredo, others, spurred on by their knowledge of the principles of curved mirrors, discussed the idea of building a telescope using a mirror as the image forming objective.
There were reports that the Bolognese Cesare Caravaggi had constructed one around 1626 and the Italian professor Niccolò Zucchi, in a work, wrote that he had experimented with a concave bronze mirror in 1616, but said it did not produce a satisfactory image. The potential advantages of using parabolic mirrors reduction of spherical aberration with no chromatic aberration, led to many proposed designs for reflecting telescopes; the most notable being James Gregory, who published an innovative design for a ‘reflecting’ telescope in 1663. It would be ten years, before the experimental scientist Robert Hooke was able to build this type of telescope, which became known as the Gregorian telescope. Isaac Newton has been credited with building the first reflecting telescope in 1668, it used a spherically ground metal primary mirror and a small diagonal mirror in an optical configuration that has come to be known as the Newtonian telescope. Despite the theoretical advantages of the reflector design, the difficulty of construction and the poor performance of the speculum metal mirrors being used at the time meant it took over 100 years for them to become popular.
Many of the advances in reflecting telescopes included the perfection of parabolic mirror fabrication in the 18th century, silver coated glass mirrors in the 19th century, long-lasting aluminum coatings in the 20th century, segmented mirrors to allow larger diameters, active optics to compensate for gravitational deformation. A mid-20th century innovation was catadioptric telescopes such as the Schmidt camera, which use both a spherical mirror and a lens as primary optical elements used for wide-field imaging without spherical aberration; the late 20th century has seen the development of adaptive optics and lucky imaging to overcome the problems of seeing, reflecting telescopes are ubiquitous on space telescopes and many types of spacecraft imaging devices. A curved primary mirror is the reflector telescope's basic optical element that creates an image at the focal plane; the distance from the mirror to the focal plane is called the focal length. Film or a digital sensor may be located here to record the image, or a secondary mirror may be added to modify the optical characteristics and/or redirect the light to film, digital sensors, or an eyepiece for visual observation.
The primary mirror in most modern telescopes is composed of a solid glass cylinder whose front surface has been ground to a spherical or parabolic shape. A thin layer of aluminum is vacuum deposited onto the mirror, forming a reflective first surface mirror; some telescopes use primary mirrors. Molten glass is rotated to make its surface paraboloidal, is kept rotating while it cools and solidifies; the resulting mirror shape approximates a desired paraboloid shape that requires minimal grinding and polishing to reach the exact figure needed. Reflecting telescopes, just like any other optical system, do not produce "perfect" images; the need to image objects at distances up to infinity, view them at different wavelengths of light, along with the requirement to have some way to view the image the primary mirror produces, means there is always some compromise in a reflecting telescope's optical design. Because the primary mirror focuses light to a common point in front of its own reflecting surface all reflecting telescope designs have a secondary mirror, film holder, or detector near that focal point obstructing the light from reaching the primary mirror.
Not only does this cause some reduction in the amount of light the system collects, it causes a loss in contrast in the image due to diffraction effects of the obstruction as well as diffraction spikes caused by most secondary support structures. The use of mirrors avoids chromatic aberration but they produce other types of aberrations. A simple spherical mirror cannot bring light from a distant object to a common focus since the reflection of light rays striking the mirror near its edge do not converge with those that reflect from nearer the center of the mirror, a defect called spherical aberration. To avoid this problem most reflecting telescopes use parabolic shaped mirrors, a shape that can focus all the light to a common focus. Parabolic mirrors work well with objects near the center of the image they produce, but towards the edge of that same field of view they suffer from off axis aberrations: Coma - an aberr
Albert A. Michelson
Albert Abraham Michelson FFRS HFRSE was an American physicist known for his work on measuring the speed of light and for the Michelson–Morley experiment. In 1907 he received the Nobel Prize in Physics, becoming the first American to win the Nobel Prize in a science. Michelson was born in Strzelno, Province of Posen in Germany, the son of Samuel Michelson and his wife, Rozalia Przyłubska, both of Jewish descent, he moved to the US at the age of two. He grew up in the mining towns of Murphy's Camp and Virginia City, where his father was a merchant, his family was Jewish by birth but non-religious, Michelson himself was a lifelong agnostic. He spent his high school years in San Francisco in the home of his aunt, Henriette Levy, the mother of author Harriet Lane Levy. President Ulysses S. Grant awarded Michelson a special appointment to the U. S. Naval Academy in 1869. During his four years as a midshipman at the Academy, Michelson excelled in optics, heat and drawing. After graduating in 1873 and two years at sea, he returned to the Naval Academy in 1875 to become an instructor in physics and chemistry until 1879.
In 1879, he was posted to Washington, to work with Simon Newcomb. In the following year he obtained leave of absence to continue his studies in Europe, he visited the Universities of Berlin and Heidelberg, the Collège de France and École Polytechnique in Paris. In 1877, he married Margaret Hemingway, daughter of a wealthy New York stockbroker and lawyer and the niece of his commander William T. Sampson, they had a daughter. Michelson was fascinated with the sciences, the problem of measuring the speed of light in particular. While at Annapolis, he conducted his first experiments of the speed of light, as part of a class demonstration in 1877, his Annapolis experiment was refined, in 1879, he measured the speed of light in air to be 299,864 ± 51 kilometres per second, estimated the speed of light in vacuum as 299,940 km/s, or 186,380 mi/s. After two years of studies in Europe, he resigned from the Navy in 1881. In 1883 he accepted a position as professor of physics at the Case School of Applied Science in Cleveland and concentrated on developing an improved interferometer.
In 1887 he and Edward Morley carried out the famous Michelson–Morley experiment which failed to detect evidence of the existence of the luminiferous ether. He moved on to use astronomical interferometers in the measurement of stellar diameters and in measuring the separations of binary stars. In 1889 Michelson became a professor at Clark University at Worcester, Massachusetts and in 1892 was appointed professor and the first head of the department of physics at the newly organized University of Chicago. In 1898, he noted the Gibbs phenomenon in Fourier analysis on a mechanical computer, constructed by him. In 1907, Michelson had the honor of being the first American to receive a Nobel Prize in Physics "for his optical precision instruments and the spectroscopic and metrological investigations carried out with their aid", he won the Copley Medal in 1907, the Henry Draper Medal in 1916 and the Gold Medal of the Royal Astronomical Society in 1923. A crater on the Moon is named after him. Michelson died in Pasadena, California at the age of 78.
The University of Chicago Residence Halls remembered Michelson and his achievements by dedicating'Michelson House' in his honor. Case Western Reserve has dedicated a Michelson House to him, Michelson Hall at the United States Naval Academy bears his name. Clark University named a theatre after him. Michelson Laboratory at Naval Air Weapons Station China Lake in Ridgecrest, California is named for him. There is a display in the publicly accessible area of the Lab which includes facsimiles of Michelson's Nobel Prize medal, the prize document, examples of his diffraction gratings. Numerous awards and honors have been created in Albert A. Michelson's name; some of the current awards and lectures named for Michelson include the following: the Bomem-Michelson Award and Lecture annually presented until 2017 by the Coblentz Society. A. Michelson Award presented every year by the Computer Measurement Group. S. Naval Academy. In 1899, he married Edna Stanton, they raised three daughters. As early as 1869, while serving as an officer in the United States Navy, Michelson started planning a repeat of the rotating-mirror method of Léon Foucault for measuring the speed of light, using improved optics and a longer baseline.
He conducted some preliminary measurements using improvised equipment in 1878, about the same time that his work came to the attention of Simon Newcomb, director of the Nautical Almanac Office, advanced in planning his own study. Michelson's formal experiments took place in June and July 1879, he constructed a frame building along the north sea wall of the Naval Academy to house the machinery. Michelson published his result of 299,910 ± 50 km/s in 1879 before joining Newcomb in Washington DC to assist with his measurements there, thus began a long professional collaboration and friendship between the two. Simon Newcomb, with his more adequately funded project, obtained a value of 299,860 ±
Mount Wilson Observatory
The Mount Wilson Observatory is an astronomical observatory in Los Angeles County, United States. The MWO is located on Mount Wilson, a 1,740-metre peak in the San Gabriel Mountains near Pasadena, northeast of Los Angeles; the observatory contains two important telescopes: the 100-inch Hooker telescope, the largest aperture telescope in the world from its completion in 1917 to 1949, the 60-inch telescope, the largest operational telescope in the world when it was completed in 1908. It contains the Snow solar telescope completed in 1905, the 60 foot solar tower completed in 1908, the 150 foot solar tower completed in 1912, the CHARA array, built by Georgia State University, which became operational in 2004 and was the largest optical interferometer in the world at its completion. Due to the inversion layer that traps smog over Los Angeles, Mount Wilson has more natural steady air than any other location in North America, making it ideal for astronomy and in particular for interferometry; the increasing light pollution due to the growth of greater Los Angeles has limited the ability of the observatory to engage in deep space astronomy, but it remains a productive center, with the CHARA Array continuing important stellar research.
The observatory was conceived and founded by George Ellery Hale, who had built the 1 meter telescope at the Yerkes Observatory the world's largest telescope. The Mount Wilson Solar Observatory was first funded by the Carnegie Institution of Washington in 1904, leasing the land from the owners of the Mount Wilson Hotel in 1904. Among the conditions of the lease was that it allow public access. There are three solar telescopes at Mount Wilson Observatory. Today, the 60 foot Solar Tower, is still used for solar research; the Snow Solar Telescope was the first telescope installed at the fledgling Mount Wilson Solar Observatory. It was the world's first permanently mounted solar telescope. Solar telescopes had been portable so they could be taken to solar eclipses around the world; the telescope was donated to Yerkes Observatory by Helen Snow of Chicago. George Ellery Hale director of Yerkes, had the telescope brought to Mount Wilson to put it into service as a proper scientific instrument, its 24-inch primary mirror with a 60-foot focal length, coupled with a spectrograph, did groundbreaking work on the spectra of sunspots, doppler shift of the rotating solar disc and daily solar images in several wavelengths.
Stellar research soon followed as the brightest stars could have their spectra recorded with long exposures on glass plates. Today the Snow solar telescope is used by undergraduate students who get hands on training in solar physics and spectroscopy, it was used publicly for the May 9, 2016 transit of Mercury across the face of the sun. The 60-foot Solar Tower soon built on the work started at the Snow telescope. At its completion in 1908, the vertical tower design of the 60 foot focal length solar telescope allowed much higher resolution of the solar image and spectrum than the Snow telescope could achieve; the higher resolution came from situating the optics higher above the ground, thereby avoiding the distortion caused by the heating of the ground by the sun. On June 25, 1908, Hale would record Zeeman splitting in the spectrum of a sunspot, showing for the first time that magnetic fields existed somewhere besides the earth. A discovery was of the reversed polarity in sunspots of the new solar cycle of 1912.
The success of the 60 foot Tower prompted Hale to pursue yet taller tower telescope. In the 1960s, Robert Leighton discovered the sun had a 5-minute oscillation and the field of heliosiesmology was born; the 60 foot Tower is operated by the Department of Physics and Astronomy at University of Southern California. The 150-foot focal length solar tower expanded on the solar tower design with its tower-in-a-tower design. An inner tower supports the optics above, while an outer tower, which surrounds the inner tower, supports the dome and floors around the optics; this design allowed complete isolation of the optics from the effect of wind swaying the tower. Two mirrors feed sunlight to a 12-inch lens, it was first completed in 1910, but unsatisfactory optics caused a two-year delay before a suitable doublet lens was installed. Research included solar rotation, sunspot polarities, daily sunspot drawings, many magnetic field studies; the solar telescope would be the world's largest for 50 years until the McMath-Pierce Solar telescope was completed at Kitt Peak in Arizona in 1962.
In 1985, UCLA took over operation of the solar tower from the Carnegie Observatories after it was decided to stop funding the observatory. For the 60-inch telescope, George Ellery Hale received the 60-inch mirror blank, cast by Saint-Gobain in France, in 1896 as a gift from his father, William Hale, it was a glass disk 19 cm thick and weighing 860 kg. However it was not until 1904 that Hale received funding from the Carnegie Institution to build an observatory. Grinding took two years; the mounting and structure for the telescope was built in San Francisco and survived the 1906 earthquake. Transporting the pieces to the top of Mount Wilson was an enormous task. First light was December 8, 1908, it was at the time the largest operational telescope in the world. Lord Rosse's Leviathan of Parsonstown, a 72-inch telescope built in 1845, was, by the 1890s, out of commission. Although smaller than the Leviathan, the 60-inch had many advantages including a far better site, a glass mirror instead
Interferometry is a family of techniques in which waves electromagnetic waves, are superimposed, causing the phenomenon of interference, used to extract information. Interferometry is an important investigative technique in the fields of astronomy, fiber optics, engineering metrology, optical metrology, seismology, quantum mechanics and particle physics, plasma physics, remote sensing, biomolecular interactions, surface profiling, mechanical stress/strain measurement and optometry. Interferometers are used in science and industry for the measurement of small displacements, refractive index changes and surface irregularities. In most interferometers, light from a single source is split into two beams that travel in different optical paths, which are combined again to produce interference; the resulting interference fringes give information about the difference in optical path lengths. In analytical science, interferometers are used to measure lengths and the shape of optical components with nanometer precision.
In Fourier transform spectroscopy they are used to analyze light containing features of absorption or emission associated with a substance or mixture. An astronomical interferometer consists of two or more separate telescopes that combine their signals, offering a resolution equivalent to that of a telescope of diameter equal to the largest separation between its individual elements. Interferometry makes use of the principle of superposition to combine waves in a way that will cause the result of their combination to have some meaningful property, diagnostic of the original state of the waves; this works because when two waves with the same frequency combine, the resulting intensity pattern is determined by the phase difference between the two waves—waves that are in phase will undergo constructive interference while waves that are out of phase will undergo destructive interference. Waves which are not in phase nor out of phase will have an intermediate intensity pattern, which can be used to determine their relative phase difference.
Most interferometers use some other form of electromagnetic wave. A single incoming beam of coherent light will be split into two identical beams by a beam splitter; each of these beams travels a different route, called a path, they are recombined before arriving at a detector. The path difference, the difference in the distance traveled by each beam, creates a phase difference between them, it is this introduced phase difference that creates the interference pattern between the identical waves. If a single beam has been split along two paths the phase difference is diagnostic of anything that changes the phase along the paths; this could be a physical change in the path length itself or a change in the refractive index along the path. As seen in Fig. 2a and 2b, the observer has a direct view of mirror M1 seen through the beam splitter, sees a reflected image M′2 of mirror M2. The fringes can be interpreted as the result of interference between light coming from the two virtual images S′1 and S′2 of the original source S.
The characteristics of the interference pattern depend on the nature of the light source and the precise orientation of the mirrors and beam splitter. In Fig. 2a, the optical elements are oriented so that S′1 and S′2 are in line with the observer, the resulting interference pattern consists of circles centered on the normal to M1 and M'2. If, as in Fig. 2b, M1 and M′2 are tilted with respect to each other, the interference fringes will take the shape of conic sections, but if M′1 and M′2 overlap, the fringes near the axis will be straight and spaced. If S is an extended source rather than a point source as illustrated, the fringes of Fig. 2a must be observed with a telescope set at infinity, while the fringes of Fig. 2b will be localized on the mirrors. Use of white light will result in a pattern of colored fringes; the central fringe representing equal path length may be light or dark depending on the number of phase inversions experienced by the two beams as they traverse the optical system.
Interferometers and interferometric techniques may be categorized by a variety of criteria: In homodyne detection, the interference occurs between two beams at the same wavelength. The phase difference between the two beams results in a change in the intensity of the light on the detector; the resulting intensity of the light after mixing of these two beams is measured, or the pattern of interference fringes is viewed or recorded. Most of the interferometers discussed in this article fall into this category; the heterodyne technique is used for shifting an input signal into a new frequency range as well as amplifying a weak input signal. A weak input signal of frequency f1 is mixed with a strong reference frequency f2 from a local oscillator; the nonlinear combination of the input signals creates two new signals, one at the sum f1 + f2 of the two frequencies, the other at the difference f1 − f2. These new frequencies are called heterodynes. Only one of the new frequencies is desired, the other signal is filtered out of the output of the mixer.
The output signal will have an intensity proportional to the product of the amplitudes of the input signals. The most important and used application of th
Virtual International Authority File
The Virtual International Authority File is an international authority file. It is a joint project of several national libraries and operated by the Online Computer Library Center. Discussion about having a common international authority started in the late 1990s. After a series of failed attempts to come up with a unique common authority file, the new idea was to link existing national authorities; this would present all the benefits of a common file without requiring a large investment of time and expense in the process. The project was initiated by the US Library of Congress, the German National Library and the OCLC on August 6, 2003; the Bibliothèque nationale de France joined the project on October 5, 2007. The project transitioned to being a service of the OCLC on April 4, 2012; the aim is to link the national authority files to a single virtual authority file. In this file, identical records from the different data sets are linked together. A VIAF record receives a standard data number, contains the primary "see" and "see also" records from the original records, refers to the original authority records.
The data are available for research and data exchange and sharing. Reciprocal updating uses the Open Archives Initiative Protocol for Metadata Harvesting protocol; the file numbers are being added to Wikipedia biographical articles and are incorporated into Wikidata. VIAF's clustering algorithm is run every month; as more data are added from participating libraries, clusters of authority records may coalesce or split, leading to some fluctuation in the VIAF identifier of certain authority records. Authority control Faceted Application of Subject Terminology Integrated Authority File International Standard Authority Data Number International Standard Name Identifier Wikipedia's authority control template for articles Official website VIAF at OCLC