Sloan Digital Sky Survey Imaging of Low Galactic Latitude Fields Technical Summary and Data

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小小黏菌,大大智慧：预测星系间暗物质网络的黏菌算法

小小黏菌，大大智慧：预测星系间暗物质网络的黏菌算法作者：Leo来源：《飞碟探索》2020年第02期黏菌是群体智能的代表：个体是单细胞，但菌落的繁殖移动却像是拥有智慧——可以找到食物之间的最短路径。

在一項最新研究中，黏菌的群体智能被进一步开发——研究者参考黏菌生长设计出的新算法，竟然能够高质量地模拟宇宙演化的过程，井构建出可信的星系间暗物质网络。

绘制宇宙网的黏菌算法根据广为接受的大爆炸理论，在大爆炸之后，弥漫在宇宙中的物质逐渐形成了星系、星云等天体，天体之间则存在着巨大的空洞。

依照现有理论，这些大型天体并不是孤立地运转在这片虚空之中的，而是由暗物质和气体构成的细丝把众多的星体联系在一起，形成了宇宙网（cosmicweb）。

这些看不到的暗物质，在宇宙，总物质中的占比达到惊人的85%。

科学家却很难观测这些包含暗物质和气体的丝线，因为它们确实“暗”得难以被探测到。

群有着黄色黏液的黏菌启发了加州大学圣克鲁兹分校的天文学家和计算机科学家，他们利用黏菌的生长模型设计了一种算法，以帮助天文学家们计算出宇宙网。

这一创造性的算法为预测宇宙网的大尺度结构提供了新方法。

黏菌——科学家的老朋友黏菌可以说算得上是科学家的老朋友了，尤其是一种被称为“海绵宝宝”的黏菌——多头绒泡菌（Physarumpolycephalum），更是广为人知的学术明星。

多头绒泡菌常见于森林的朽木和落叶中。

多个细胞聚集在一起形成的原生质团（一种成分复杂的胶体），会为了寻找食物而四处“爬动”，从而绘制出往来食物之间的最优路径，最终形成复杂又迷人的网络。

科学家就曾做过利用黏菌走迷宫的实验，更广为人知的，可能就是利用多头绒泡菌绘制东京交通网络的实验了。

黏菌算法这个利用黏菌模型来实现的多主体算法并不算复杂。

首先，把输入的数据模拟为黏菌要找的食物（deposit）。

黏菌为了寻找食物会依照随机选定的角度和距离移动，并在网络中留下随机游走的轨迹（trace），最终会布满整个空间。

剑桥商务英语听说星系

剑桥商务英语听说星系The Milky Way GalaxyThe Milky Way is the galaxy that contains our Solar System, with the Earth and Sun. This galaxy is a vast, spinning collection of stars, planets, dust and gas, held together by gravity. It is just one of hundreds of billions of galaxies in the observable universe.The Milky Way galaxy is estimated to contain 100-400 billion stars and have a diameter between 100,000 and 180,000 light-years. It is the second-largest galaxy in the Local Group, with the Andromeda Galaxy being larger. As with other spiral galaxies, the Milky Way has a central bulge surrounded by a rotating disk of gas, dust and stars. This disk is approximately 13 billion years old and contains population I and population II stars.The solar system is located about 25,000 to 28,000 light-years from the galactic center, on the inner edge of one of the spiral-shaped concentrations of gas and dust called the Orion Arm. The stars in the Milky Way appear to form several distinct components including the bulge, the disk, and the halo. These components are made of different types of stars, and differ in their ages and their chemicalabundances.The Milky Way galaxy is part of the Local Group, a group of more than 50 galaxies, including the Andromeda Galaxy and several dwarf galaxies. The Local Group in turn is part of the Virgo Supercluster, a giant structure of thousands of galaxies. The Milky Way and Andromeda Galaxy are moving towards each other and are expected to collide in about 4.5 billion years, although the likelihood of any actual collisions between the stars themselves is negligible.The Milky Way has several major arms that spiral from the galactic bulge, as well as minor spurs. The best known are the Perseus Arm and the Sagittarius Arm. The Sun and its solar system are located between two of these spiral arms, known as the Local Bubble. There are believed to be four major spiral arms, as well as several smaller segments of spiral arms.The nature of the Milky Way's bar and spiral structure is still a matter of active research, with the latest research contradicting the previous theories. The Milky Way may have a prominent central bar structure, and its shape may be best described as a barred spiral galaxy. The disk of the Milky Way has a diameter of about 100,000 light-years. The galactic halo is a spherical component of the galaxy that extends outward from the galactic disk, as far as 200,000 light-years from the galactic center.The disk of the Milky Way Galaxy is marked by the presence of a supermassive black hole known as Sagittarius A*, which is located at the very center of the Galaxy. This black hole has a mass four million times greater than the mass of the Sun. The Milky Way's bar is thought to be about 27,000 light-years long and may be made up of older red stars.The Milky Way is moving with respect to the cosmic microwave background radiation in the direction of the constellation Hydra with a speed of 552 ± 6 km/s. The Milky Way is a spiral galaxy that has undergone major mergers with several smaller galaxies in its distant past. This is evidenced by studies of the stellar halo, which contains globular clusters and streams of stars that were torn from those smaller galaxies.The Milky Way is estimated to contain 100–400 billion stars. Most stars are within the disk and bulge, while the galactic halo is sparsely populated with stars and globular clusters. A 2016 study by the Sloan Digital Sky Survey suggested that the number is likely to be close to the lower end of that estimate, at 100–140 billion stars.The Milky Way has several components: a disk, in which the Sun and its planetary system are located; a central bulge; and a halo of stars, globular clusters, and diffuse gas. The disk is the brightest part of theMilky Way, as seen from Earth. It has a spiral structure with dusty arms. The disk is about 100,000 light-years in diameter and about 13 billion years old. It contains the young and relatively bright population I stars, as well as intermediate-age and old stars of population II.The galactic bulge is a tightly packed group of mostly old stars in the center of the Milky Way. It is estimated to contain tens of billions of stars and has a diameter of about 10,000 light-years. The Milky Way's central bulge is shaped like a box or peanut. The galactic center, which lies within this bulge, is an extremely active region, with intense radio source known as Sagittarius A*, which is likely to be a supermassive black hole.The Milky Way's halo is a spherical component of the galaxy that extends outward from the galactic disk, as far as 200,000 light-years from the galactic center. It is relatively sparse, with only about one star per cubic parsec on average. The halo contains old population II stars, as well as extremely old globular clusters.The Milky Way's spiral structure is uncertain, and there is currently no consensus on the nature of the Milky Way's spiral arms. Different studies have led to different results, and it is unclear whether the Milky Way has two, four, or more spiral arms. The Milky Way's spiral structure is thought to be a major feature of its disk, and it may berelated to the generation of interstellar matter and star formation.The Milky Way's spiral arms are regions of the disk in which the density of stars, interstellar gas, and dust is slightly higher than average. The arms are thought to be density waves that spiral around the galactic center. As material enters an arm, the increased density causes the material to accumulate, thus causing star formation. As the material leaves the arm, star formation decreases.The Milky Way's spiral arms were first identified in the 1950s, when radio astronomers mapped the distribution of gas in the Milky Way and found that it was concentrated in spiral patterns. Since then, astronomers have used a variety of techniques to study the Milky Way's spiral structure, including observations of the distribution of young stars, star-forming regions, and interstellar gas and dust.One of the key challenges in studying the Milky Way's spiral structure is that we are located within the disk of the galaxy, which makes it difficult to get a clear view of the overall structure. Astronomers have had to rely on indirect methods, such as measuring the distances and motions of stars and gas clouds, to infer the shape and structure of the galaxy.Despite these challenges, our understanding of the Milky Way's spiral structure has advanced significantly in recent years, thanks tonew observations and more sophisticated modeling techniques. Ongoing research is continuing to shed light on the nature and evolution of the Milky Way's spiral arms, and the role they play in the overall structure and dynamics of the galaxy.。

The Sloan Digital Sky Survey Status and Prospects

a r X i v :a s t r o -p h /9605028v 1 7 M a y 1996THE SLOAN DIGITAL SKY SUR VEY:STATUS ANDPROSPECTSJon Loveday Fermilab,Batavia,USA.(On behalf of the SDSS collaboration.)Abstract The Sloan Digital Sky Survey (SDSS)is a project to deﬁnitively map πsteradians of the local Universe.An array of CCD detectors used in drift-scan mode will digitally image the sky in ﬁve passbands to a limiting magnitude of r ′∼23.Selected from the imaging survey,106galaxies and 105quasars will be observed spectroscopically.I describe the current status of the survey,which is due to begin observations early in 1997,and itsprospects for constraining models for dark matter in the Universe.1IntroductionSystematic surveys of the local Universe (z ∼<0.2)can provide some of the most important constraints on dark matter,particularly through the measurement of the clustering of galaxies and clusters of galaxies on large scales.Most existing galaxy and cluster catalogues are based on photographic plates [7,3],and there is growing concern that such surveys might suﬀer from severe surface-brightness selection eﬀects,so that they are missing a substantial fraction of the galaxy population.In addition,the limited volume of existing redshift surveys means that even low-order clustering statistics,such as the galaxy two-point correlation function,cannot reliably be measured on scales beyond 100h −1Mpc,an order of magnitude below the scale on which COBE has measured ﬂuctuations in the microwave background radiation.A collaboration has therefore been formed with the aim of constructing a deﬁnitive map ofthe local universe,incorporating digital CCD imaging over a large area in several passbands and redshifts for around one million galaxies.In order to complete such an ambitious project over a reasonable timescale,it was decided to build a dedicated 2.5-metre telescope equippedwith a large CCD array imaging camera and multi-ﬁbre spectrographs.The collaboration com-prises around100astronomers and engineers from University of Chicago,Fermilab,Princeton University,Institute for Advanced Study,Johns Hopkins University,US Naval Observatory,University of Washington and the JPG—a group of astronomers in Japan.The total cost ofthe survey is around$30million,and funding sources include the Alfred P.Sloan Foundation,the National Science Foundation and the participating institutions.2Survey OverviewThe survey site is Apache Point Observatory,New Mexico,at2800metres elevation.Whilebetter sites probably exist in Chile and atop Mauna Kea,for a survey with such state-of-the-art instrumentation and signiﬁcant on-site manpower requirements(eg.ﬁbre plugging andchanging spectroscopic plates),it was decided to use a site within mainland USA and withgood communications and existing infrastructure.Figure1:SDSS system responsecurves,with(lower)and without(upper)atmospheric extinction.The survey hardware comprises the main2.5-metre telescope,equipped with CCD imagingcamera and multi-ﬁbre spectrographs,a0.6-metre monitor telescope and a10µall-sky camera.On the best nights(new moon,photometric,sub-arcsecond seeing)the2.5-metre telescopewill operate in imaging mode,drift scanning the sky at sidereal rate,and obtaining nearly simultaneously images in theﬁve survey bands u′,g′,r′,i′and z′.The system response curvesthrough theﬁveﬁlters are shown in Figure1.On sub-optimal nights,which will comprise thebulk of observing time,the imaging camera will be replaced with a spectroscopicﬁbre plug-plate.It is planned that imaging data will be reduced and calibrated,spectroscopic targetsselected,and plates drilled within the one-month lunar cycle,so that we will be obtainingspectra of objects that were imaged the previous month.We will spend most of the timeobserving within a contiguousπsteradian area in the north Galactic cap(NGC).For thosetimes when the NGC is unavailable,about one third of the time,we will repeatedly observethree southern stripes,nominally centred at RAα=5◦,and with central declinations ofδ=+15◦,0◦and−10◦.The nominal location of survey scans is shown in Figure2.In the remainder of this section I discuss the various components of the survey in moredetail.Figure2:Whole sky plot show-ing the location of SDSS scans.The light lines show galactic lat-itudes of b=0,±30and±60◦,with the north and south Galac-tic poles being the upper andlower crosses respectively.TheGalactic plane runs horizontallythrough the middle of the plotand the grey scale map showsStark HI contours in units of1020cm−2.The dark lines show thesurvey scan-lines,all of which fol-low great circles.We observe acontiguous area ofπsr in thenorth,and three separated stripesin the south.Note that the north-ern survey is tilted with respect tothe b=+30◦contour to avoid re-gions of high HI column density.2.5-metre telescope.The main2.5-metre telescope is of modiﬁed Richey-Chretien design with a3◦ﬁeld of view,and is optimised for both a wide-area imaging survey and a multi-ﬁbre spectroscopic survey of galaxies to r′∼18.One of the most unusual aspects of the telescope is it’s enclosure.Rather than sitting inside a dome,as is the case with conventional optical telescopes,the enclosure is a rectangular frame structure mounted on wheels,which is rolled away from the telescope in order to take observations.By completely removing the enclosure from the telescope,we can avoid the substantial degradation to image quality due to dome seeing.The telescope is situated on a pier overlooking a steep dropoﬀso that the prevailing wind willﬂow smoothly over the telescope in a laminarﬂow,which will also help to ensure good image quality.A wind baﬄe closely surrounds the telescope,and is independently mounted and driven.This baﬄe serves to protect the telscope from stray light as well as from wind buﬀeting.Imaging Camera.In order to image a large area of sky in a short time,we are building an imaging camera(Fig.3)that contains30×20482CCDs,arranged in six columns.Each column occupies its own dewar and contains one chip in each of theﬁveﬁlters.Pixel size is 0.4′′.The camera operates in drift-scan mode:a star or galaxy image drifts down the column through theﬁveﬁlters,spending about55seconds in each.This mode of observing has two signiﬁcant advantages over conventional tracking mode.1)It makes extremely eﬃcient use of observing time,since there is no overhead between exposures:on a good night we can open the shutter,drift-scan for eight hours and then close the shutter.2)Since each image traverses a whole column of pixels on each CCD,ﬂat-ﬁelding becomes a one-dimensional problem,and so can be done to lower surface-brightness limits than with tracking mode images.This,along with the high quantum eﬃciency of modern CCDs,will enable us to detect galaxies of much lower surface brightness than can wide-ﬁeld photographic surveys.There is a gap between each column of CCDs,but this gap is slightly smaller than the width of the light-sensitive area of theFigure3:Focal plane layout ofthe SDSS CCD imaging camera,showing the30photometric and24astrometric/focus CCDs.CCDs,and so having observed six narrow strips of sky one night,we can observe an interleaving set of strips a later night,and thus build up a large contiguous area of sky.The northern survey comprises45pairs of interleaving great circle scans,and so imaging observations for the north will require the equivalent of90full photometric nights.The camera also includes24smaller CCDs arranged above and below the photometric columns.These extra CCDs,equipped with neutral densityﬁlters,are used for astrometric calibration,as most astrometric standards will saturate on the photometric CCDs.Thus the photometric data can be tied to the fundamental astrometric reference frames deﬁned by bright stars.Spectrographs.The2.5-metre telescope will also be equipped with a pair ofﬁbre-fed, dual-beam spectrographs,each with two cameras,two gratings and two20482CCD detectors. The blue channel will cover the wavelength range3900–6100˚A and the red channel5900–9100˚A and both will have a spectral resolving powerλ/∆λ≈1800.Theﬁbres are3′′in diameter and the two spectrographs each hold320ﬁbres.Rather than employing roboticﬁbre positioners to place theﬁbres in the focal plane,we will instead drill aluminium plates for each spectroscopic ﬁeld and plug theﬁbres by hand.We plan on spectroscopic exposure times of45minutes and allow15minutes overhead perﬁbre plate.On a clear winter’s night we can thus obtain8plates ×640ﬁbres=5120spectra.In order to allow such rapid turnaround time between exposures we plan to purchase8sets ofﬁbre harnesses,so that each plate can be plugged withﬁbres during the day.It will not be necessary to plug eachﬁbre in any particular hole,as aﬁbre mapping system has been built which will automatically mapﬁbre number onto position in the focal plane after the plate has been plugged.This should considerably ease the job of theﬁbre pluggers,and we expect that it will take well under one hour to plug each plate.Monitor telescope.In order to check that observing conditions are photometric,and totie imaging observations to a set of primary photometric standards,we are also employing a monitor telescope.While the2.5-metre telescope is drift-scanning the sky,the0.6-metre mon-itor telescope,situated close by,will interleave observations of standard stars with calibration patches in the area of sky being scanned.Operation of this telescope will be completely au-tomated,and each hour will observe three calibration patches plus standard stars in allﬁve colours.10µall-sky camera.As an additional check on observing conditions,a10µinfrared camera will survey the entire sky every10minutes or so.Light cirrus,which is very hard to see on a dark night,is bright at10µ,and so this camera will provide rapid warning of increasing cloud cover,thus enabling us to switch to spectroscopic observing rather than taking non-photometric imaging data.10/7/93Figure4:Top-level data processing diagram.Data-reduction pipelines.The last,but by no means least,component of the survey is a suite of automated data-reduction pipelines(Fig.4),which will read DLT tapes mailed to Fermilab from the mountain and yield reduced and calibrated data with the minimum of human intervention.Such software is very necessary when one considers that the imaging camera will produce data at the rate of around31Gbytes per hour!A“production system”has been specced and purchased that can keep up with such a data rate(bearing in mind that imaging will take place only under the best conditions,on average around two full nights per month), and consists of two Digital Alphaserver82005/300s,each with1GByte of memory.Pipelines exist to reduce each source of data from the mountain(photometric frames and “postage stamps”,astrometric frames,monitor telescope frames and2-D spectra)as well as to perform tasks such as spectroscopic target selection and“adaptive tiling”to work out the optimal placing of spectroscopicﬁeld centres to maximize the number of spectra obtained.Thepipelines are integrated into a purpose-written environment known as SHIVA(Survey Human Interface and VisualizAtion environment,also the Hindu god of destruction)and the reduced data will be written into an object-oriented database.3Data ProductsThe raw imaging data inﬁve colours for theπsteradians of the northern sky will occupy about 14Tbytes,but it is expected that very few projects will need to access the raw data,which will probably be stored only on magnetic tape.Since most of the sky is blank to r′∼23,all detected images can be stored,using suitable compression,in around200Gbytes,and it is expected that these“atlas images”can be kept on spinning disc.The photometric reduction pipeline will meaure a set of parameters for each image,and it is estimated that the parameter lists for all objects will occupy∼100Gbyte.The parameter lists for the spectroscopic sample will proabblyﬁt into1–2Gb,and the spectra themselves will occupy∼20Gb.Work is progressing well on an astronomer-friendly interface to the database,which will answer such queries as“Return all galaxies with(g′−r′)<0.5and within30arcminutes of this quasar”, etc.3.1Spectroscopic SamplesThe spectroscopic sample is divided into several classes.In a survey of this magnitude,it is important that the selection criteria for each class remainﬁxed throughout the duration of the survey.Therefore,we will spend a considerable time(maybe one year),obtaining test data with the survey instruments and reﬁning the spectroscopic selection criteria in light of our test data.Then,once the survey proper has commenced,these criteria will be“frozen in”for the duration of the survey.The numbers discussed below are therefore only preliminary,and we expect them to change slightly during the test year.The main galaxy sample will consist of∼900,000galaxies selected by Petrosian mag-nitude in the r′band,r′∼<18.Simulations have shown that the Petrosian magnitude,which is based on an aperture deﬁned by the ratio of light within an annulus to total light inside that radius,provides probably the least biased and most stable estimate of total magnitude. There will also be a surface-brightness limit,so that we do not wasteﬁbres on galaxies of too low surface brightness to give a reasonable spectrum.This galaxy sample will have a median redshift z ≈0.1.We plan to observe an additional∼100,000luminous red galaxies to r′∼<19.5.Given photometry in theﬁve survey bands,redshifts can be estimated for the reddest galaxies to ∆z≈0.02or better[4],and so one can also predict their luminosity quite accurately.Selecting luminous red galaxies,many of which will be cD galaxies in cluster cores,provides a valuable supplement to the main galaxy sample since1)they will have distinctive spectral features, allowing a redshift to be measured up to1.5mag fainter than the main sample,and2)they will form an approximately volume-limited sample with a median redshift z ≈0.5.They will thus provide an extremely powerful sample for studying clustering on the largest scales and the evolution of galaxies.Quasar candidates will be selected by making cuts in multi-colour space and from the FIRST radio catalogue[1],with the aim of observing∼100,000quasars.This sample will be orders of magnitude larger than any existing quasar catalogues,and will be invaluable for quasar luminosity function,evolution and clustering studies as well as providing sources for followup absorption-line observations.In addition to the above three classes of spectroscopic sources,which are designed to providestatistically complete samples,we will also obtain spectra for many thousands of stars andfor various serendipitous objects.The latter class will include objects of unusual colour ormorphology which do notﬁt into the earlier classes,plus unusual objects found by other surveysand in other wavebands.4Current StatusIn this section I discuss the status(as of April1996)of the various systems within the survey.The monitor telescope has been operational now for several months,and is routinelyoperated remotely from Chicago.It is equipped with a set of SDSSﬁlters,and is being used toobserve candidate primary photometric standard stars,as well as known quasars to see wherethey lie in the SDSS colour system[8].Figure5:Photograph of the2.5-metre telescope structure,takenshortly after installation,on10October1995.Part of the tele-scope enclosure,in its rolled backposition,appears in the bottom-left of this picture.Note that nei-ther the mirrors nor the wind baf-ﬂe are installed yet.The2.5-metre telescope structure was installed on the mountaintop in October1995(seeFig.5).Work is currently underway on the control systems for the telescope.Telescope opticsare all due to be ready by June1996.These include the primary and secondary mirrors andvarious corrector elements.We posess all of the CCDs for the imaging camera,which is under construction at Prince-ton.Delivery to the mountain is expected by September1996.Construction of the spectro-graphs is well underway,with the optics installed for one of the spectrograph cameras.Each of the data reduction-pipelines is now basically working,with ongoing work on minorbug-ﬁxes,speed-ups and integration of the entire data processing system.The photometricreduction pipeline is being tested using both simulated data and with data taken using theFermilab drift scan camera on the ARC3.5-metre telescope at the same site.Similar tests arebeing carried out on the spectroscopic reduction pipeline,and our ability to eﬃciently placeﬁbres on a clustered distribution of galaxies is being tested using the APM galaxy catalogue[7].The currently-projected survey schedule is as follows:September1996Optics to be installed on2.5-metre telescope.Autumn1996Imager and spectrograph commissioning.Winter1996Astronomicalﬁrst light.Early1997Test period begins.1998–2003Survey proper carried out.2002First two years of survey data become public.2005Complete survey data become public.The intent of this project is to make the survey data available to the astronomical community in a timely fashion.We currently plan to distribute the data from theﬁrst two years of the survey no later than two years after it is taken,and the full survey no later than two years after it isﬁnished.Theﬁrst partial release may or may not be in itsﬁnal form,depending on our ability to calibrate it fully at the time of the release.The same remarks apply to the release of the full data set,but we expect the calibration eﬀort to beﬁnished before that release.5Prospects for constraining dark matterSince one of the topics of this meeting is dark matter,I will highlight two of the areas in which the SDSS will provide valuable data for constraining dark matter.5.1Measurement of the Fluctuation SpectrumThe huge volume of the SDSS redshift survey will enable estimates of the galaxy power spectrum to∼1000h−1Mpc scales.Figure6shows the power spectrum P(k)we would expect to measure from a volume-limited(to M∗)sample of galaxies from the SDSS northern redshift survey, assuming Gaussianﬂuctuations and aΩh=0.3CDM model.The error bars include cosmic variance and shot noise,but not systematic errors,due,for example,to galactic obscuration. Provided such errors can be corrected for,(and star colours in the Sloan survey will provide our best a posteriori estimate of galactic obscuration),then theﬁgure shows that we can easily distinguish betweenΩh=0.2andΩh=0.3models,just using the northern main galaxy sample.Adding the southern stripe data,and the luminous red galaxy sample,will further decrease measurement errors on the largest scales,and so we also expect to be able to easily distinguish between low-density CDM and MDM models,and models with diﬀering indices n for the shape of the primordialﬂuctuation spectrum.5.2Cosmological Density ParameterBy measuring the distortions introduced by streaming motions into redshift-space measures of galaxy clustering,one can constrain the parameterβ=Ω0.6/b,whereΩis the cosmological density paramter and b is the bias factor relatingﬂuctuations in galaxy number density to ﬂuctuations in the underlying mass distribution.While existing redshift surveys,eg.IRAS[2] and Stromlo-APM[6],are hinting thatβ<1(ie.that galaxies are signiﬁcantly biased tracers of mass or thatΩ<1),their volumes are too small to measure galaxy clustering in the fully linear regime reliably enough to measureβto much better than50%or so.With the SDSS redshift survey,we expect to be able to constrainβto10%or better.There are several ways we might hope to determine the galaxy bias factor b.By measuring galaxy clustering on∼1000h−1Mpc scales as shown in Figure6,we can compare with the COBE microwave backgroundﬂuctuations directly,and so constrain large-scale galaxy bias inFigure6:Expected1σuncer-tainty in the galaxy power spec-trum measured from a volume-limited sample from the SDSSnorthern survey,along with pre-dictions of P(k)from four vari-ants of the low-density CDMmodel.Note that the modelshave been arbitrarily normalisedto agree on small scales(k=0.4);in practice the COBE observa-tions of CMBﬂuctuationsﬁx theamplitude of P(k)on very largescales.a model-independent way.Analysis of higher-order clustering statistics[5],and of non-linear dynamical eﬀects[2]will also set constraints on galaxy bias.Knowingβand b.we will be in a good position to reliably measure the cosmological density parameterΩindependent of models for the shape of theﬂuctuation spectrum.6ConclusionsIt is probably no exaggeration to claim that the Sloan Digital Sky Survey will revolutionize the ﬁeld of large scale structure.Certainly we can expect to rule out large numbers of presently viable cosmological models,as illustrated in Figure6.As well as measuring redshifts for a carefully controlled sample of106galaxies and105quasars,the survey will also provide high quality imaging data for about100times as many extragalactic objects,from which one can obtain colour and morphological information.In addition to measuring the basic cosmological parametersΩand h discussed in the preceding section,the SDSS will also allow us to measure the properties of galaxies as a function of their colour,morphology and environment,providing valuable clues to the process of galaxy formation.Finally,I cannot resist the temptation to give a visual impression of what we might expect to see with the SDSS redshift survey.Figure7shows the distribution of62,295galaxies in a6◦slice from a simulation carried out by Changbom Park,assuming a low-density CDM model. This slice represents just one sixteenth of the million galaxy redshifts we will be measuring with the Sloan survey.I leave it to the readers imagination to dream up all the projects they would love to carry out given such a data-set.The work described here has been carried out by many people throughout the SDSS collab-oration,and I thank all my colleagues warmly.I am particularly grateful to Chris Stoughton and Michael Vogeley for providing Figures2and Figure6respectively,and to Philippe Canal for translating the Abstract into French.My attendance at the meeting was supported by a generous grant from the EEC.Figure7:Redshift-space distribu-tion of galaxies in a6◦slice from alarge,low-density CDM N-bodysimulation generated by Chang-bom Park.References[1]Becker,R.H.,White,R.L.and Helfand,D.J.,1995,ApJ,450,559[2]Cole,S.,Fisher,K.B.and Weinberg,D.H.,1995,MNRAS,275,515[3]Collins,C.A.,Heydon-Dumbleton,N.H.and MacGillivray,H.T.,1989,MNRAS,236,7P[4]Connolly,A.J.,et al.,1995,AJ,110,2655[5]Gazta˜n aga,E.and Frieman,J.A.,1994,ApJ,437,L13[6]Loveday,J.,Efstathiou,G.,Maddox,S.J.and Peterson,B.A.,1996,ApJ,in press[7]Maddox,S.J.,Sutherland,W.J.Efstathiou,G.and Loveday,J.,1990,MNRAS,243,692[8]Richards,G.T.,et al.,PASP,submittedLE SLOAN DIGITAL SKY SURVEY:L’´ETAT ET CES PERSPECTIVES Le Sloan Digital Sky Survey(SDSS)`a pour but de cartographi´eπsteradians de l’univers local.Une matrice de dispositif`a transfert de charges(CCD)scannant en mode balayage produira une image digitalis´e e du ciel avec cinq diﬀ´e rentsﬁltres et avec une pr´e cision allant jusqu’a`a peu pr`e s magnitude23.Une´e tude spectroscopique sera faite sur une s´e lection de106 galaxies et105quasars.Dans cet article,apr`e s avoir d´e cris l’´e tat d’advancement du projet qui doit commencer`a faire des observations des le d´e but de l’ann´e e1997,je pr´e sente ces perspectives pour l’´e tablissement de mod`e les de la mati`e re noire dans l’univers.。

2019届奉贤区高考英语二模

学霸学习提醒一、课本是最好的老师。

要注重基础，反复研读课本，巩固基础知识。

二、要养成良好的学习习惯。

良好的学习习惯是高效率掌握知识的保障。

三、要保持良好的学习状态，自信踏实，刻苦努力，以饱满的精神迎接新一天的挑战。

四、课堂上：专心听讲是第一位。

事实证明，自以为是的确是不好的习惯。

同样的例题，自己看懂与听老师讲懂是完全不同的两种效果。

五、建议同学们在课外多投入些时间做题，并且要从心里重视数学。

还应该准备一个错题本，老老实实地将每次错过的题抄在上面，并写上正确的解题思路，变不懂为精通。

特别提醒：请学习稍差的同学一定不要放弃，哪怕到最后一学期，也不能放弃。

只要按照老师说的去做，只要塌实地付出了，就一定会有奇迹出现。

永远不要放弃拼搏，因为奇迹只发生在相信奇迹存在的人身上！！！2018学年奉贤区调研测试高三英语试卷（2019.04）Ⅱ. Grammar and VocabularySection ADirections：After reading the passage below, fill in the blanks to make the passage coherent and grammatically correct. For the blanks with a given word, fill in each blank with the proper form of the given word; for the other blanks, use one word that best fits each blank.How to Make the Most of Y our Lunch HourShould you grab a bite at your desk or eat with your colleagues? That depends on what’s on your agenda for the rest of the day.Lunch hours ___21___（get）shorter and shorter and even disappearing in some parts of today’s working world. With fewer employees ___22___（ask）to accomplish more in a day, many Americans treat lunch not as a break but as just another task to squeeze into an already over-booked day.But do quick meals at the desk actually improve productivity over more leisurely meals?The researchers only studied 32 employees, so the findings are datable. But when they assigned one group to eat at their desks and another to dine with a colleague at a restaurant, they found those who ate lunch together showed a decline ___23___ their performance on tests that measured concentration, memory and the ability to catch errors and read emotions in facial expressions following lunch than before lunch. Both groups ate the same meals, but those who ate alone were only given 20 minutes to consume their food, ___24___ the paired participants were allowed one hour in the restaurant. Those who ate alone did not have as large a drop in their cognitive processing as those who ate in the restaurant.What was responsible for the change? There were too many variables at play to determine which had the strongest influence on cognitive control—was it the companionship, or was it the restaurant environment ___25___ other diners were present, music was played and the meal was served by wait staff, or was it the longer time to enjoy the meal?___26___ factor was responsible, the group that took a restaurant lunch break came back more relaxed, say the authors, and that likely affected their cognitive sharpness. Sharing a meal outside the office with a friend appears to have a ___27___（calm）effect, and while it reduces intellectual skills, it may develop social harmony and teamwork, which ___28___ be an important feature of some work tasks.But don’t feel sorry for the lone lunchers. It turns out ___29___ since they were able to maintain their cognitive skills following the meal, they might be in a better position ___30___（think）creatively for projects that require more innovative solutions or approaches.Section BDirections：Fill in each blank with a proper word chosen from the box. Each word can only be used once. NoteThe contributions genes make to intelligence increase as children grow older. This goes against the idea most people hold that as we age, environmental influences gradually overpower the genetic legacy（遗产）we are born with and may have ___31___ for education.“People assume the genetic influence goes down with age because the environmental differences between people pile up in life,”says Robert Plomin.“What we found was quite ___32___ and goes in the other direction.”Previous studies have shown variations in intelligence are ___33___ due to genetics. To find out whether this genetic contribution varies with age, Plomin’s team gathered data from six separate studies carried out in 4 countries, ___34___ a total of 11000 pairs of twins. The researchers tested twins on reasoning, arithmetic etc, to measure a quantity called “G”. Each study also included both identical twins, with the same genes, and Lateral twins（异卵双生）, sharing about half their genes, making it possible to ___35___ the contributions of genes and environment to their G scores.Plomin’s team calculated that in childhood, genes account for about 41 percent of the variation in intelligence. In adolescence, this rose to 55 percent; by young adolescence, it was 66 percent.No one ___36___ knows why the influence from genes should increase with age, but Plomin suggests that as children get older, they become better at handing their environment to suit their genetic needs, and says “Kids with high G will use their environment to develop their cognitive ability and choose friends who are like-minded. ” Children with ___37___ to low G may choose less challenging pastimes and activities, further emphasizing their genetic legacy.Is there any way to interfere with the pattern? Perhaps. “The evidence of strong heritability（遗传可能性）doesn’t mean at all that there is nothing you can do about it,”says Susanne Jaeggi, “from our own work, the ones that started off with lower IQ scores had higher ___38___ after training.”Plomin suggests that genetic differences may be more emphasized if all children share an identical curriculum instead of it being ___39___ to children’s natural abilities. “My tendency would be to give everyone a good education, but put more effort into the lower end,” he says.Intelligence researchers Paul Thompson agrees: “It shows that educators need to ___40___ kids towards things drawing out their natural talents.”Ⅱ. Reading Comprehension.Section ADirections：For each blank in the following passages there are four words or phrases marked A, B, C, and D. Fill in each blank with the word or phrase that best fits the context.Open data-sharers are still in the minority in many fields. Although many researchers broadly agree that public access to raw data would promote science, most are ___41___ to post the results of their own labours online.Some communities have agreed to share online-geneticists, for example, post DNA sequences at the GenBank repository（库）, and astronomers are accustomed to ___42___ images of galaxies and stars from, say, the Sloan Digital Sky Survey, a telescope that has observed some 500 million objects -- but these remain the ___43___, not the rule Historically, scientists have ___44___ sharing for many reasons: it is a lot of work; until recently, good databases did not exist; grant funders were not pushing for sharing; it has been difficult to agree on standards for formatting data; and there is no agreed way to assign credit for data.But the ___45___ are disappearing in part because journals and funding agencies worldwide are encouraging scientists to make their data ___46___. Last year, the Royal Society in London said in its report that scientists need to“___47___ a research culture where data is viewed as private preserve”. Funding agencies note that data paid for with public money should be public information, and the scientific community is recognizing that data can now be shared online in ways that were not possible before. To match the growing demand, services are springing up to make it easier to publish research products ___48___ and enable other researchers to discover and cite（引用）them.Although calls to share data often concentrate on the ___49___ advantages of sharing, the practice is not purely beneficial to others. Researchers who share get plenty of personal benefits, including more connections with colleagues, improved ___50___ and increased citations. The most successful sharers -- those whose data are downloaded and cited the most often -- get noticed, and their work gets used. ___51___, one of the most popular data sets on multidisciplinary repository Dryad is about wood density around the world; it has been ___52___ 5,700 times. Co-author Amy Zanne thinks that users probably range from climate-change researchers wanting to estimate how much carbon is stored in biomass, to foresters looking for information on different grades of trees.“I’d much prefer to have my data used by the ___53___ number of people to ask their own questions,”she says.“It’s important to allow readers and reviewers to see exactly how you arrive at your results. Publishing data and code allows your science to be ___54___.”Even people whose data are less popular can benefit. By making the effort to organize and label files so otherscan understand them, scientists can become more organized and better disciplined themselves, thus avoiding ___55___ later on.41. A. restricted B. reluctant C. desperate D. generous42. A. accessing B. processing C. analyzing D. identifying43. A. assumption B. mystery C. exception D. phenomenon44. A. longed for B. appealed to C. focused on D. objected to45. A. symptoms B. barriers C. advantages D. consequences46. A. controllable B. unique C. reliable D. public47. A. shift away from B. end up with C. give rise to D. build up48. A. secretly B. digitally C. ethically D. fairly49. A. material B. individual C. moral D. economic50. A. visibility B. awareness C. condition D. confidence51. A. On the contrary B. As a result C. For example D. After all52. A. downloaded B. updated C. optimized D. addressed53. A. moderate B. maximum C. average D. estimated54. A. reversible B. profitable C. reproducible D. recognizable55. A. crisis B. confusion C. risk D. conflictSection BDirections：Read the following three passages. Each passage is followed by several questions or unfinished statements. For each of them there are four choices marked A, B, C, and D. Choose the one that fits best according to the information given in the passage you have just read.AIt was 1961 and I was in the fifth grade. My marks in school were miserable and, the thing was, I didn’t know enough to really care. My older bother and I lived with Mom in a humble house in Detroit. We watched TV every night.But one day Mom changed our world forever. She turned off the TV. Our mother had only been able to get through third grade. But, she was much brighter and smarter than we boys know at the time. She had noticed something in the suburban houses she cleaned--books. So she came home one day, snapped off the TV, sat us down and explained that her sons were going to make something of themselves. “You boys are going to read two books every week,” she said. “And you’re going to write a report on what you read.”We complained about how unfair it was. Besides, we didn’t have any books in the house other than Mom’s Bible. But she explained that we would go where the books were: “I’ll drive you to the library.”So pretty soon there were these two peevish boys sitting in her car on their way to Detroit Public Library, depressed and restless. I wandered reluctantly among the children’s books. I loved animals, so when I saw some books that seemed to be about animals, I started leafing through them.The first book I read clear through was Chip the Dam Builder. It was about beavers. For the first time in my life I was lost in another world. No television program had ever taken me so far away from my surroundings as did this virtue visit to a cold stream in a forest and these animals building a home.It didn’t dawn on me at the time, but the experience was quite different from watching TV. There were images forming in my mind instead of before my eyes. And I could return to them again and again with the flip of a page. Soon I began to look forward to visiting this quiet refuge from my other world.Now my older brother is an engineer and I am a doctor. Sometimes I still can’t believe my life’s journey, from a failing and indifferent student in a Detroit public school to this position, which takes me all over the world to teachand perform critical surgery.But I know when the journey began the day Mom switched off the TV set and put us in her Oldsmobile for that drive to the library.56. We can learn from the beginning of the passage that ____.A. the author and his brother had done well in schoolB. the author had been very concerned about his school workC. the author had spent much time watching TV after schoolD. the author had realized how important schooling was57. According to the passage, which of the following words can best describe the author’s mother?A. Tolerant and decisive.B. Aggressive and open-minded.C. Determined and farsighted.D. Persistent and literate.58. The underlined word“peevish”in the passage can be replaced by ____.A. naughtyB. bad-temperedC. patientD. obedient59. The author began to love books for the following reasons EXCEPT that ___.A. he could constantly review the plots in the booksB. he could visualize what he read in his mindC. he could get many rewards from his motherD. he realized that books offered him new experienceBNANCY DREW AND THE HIDDEN STAIRCASE（PG）Age 10+Sparkling book adaptation has great characters, some scares.“Nancy Drew and the Hidden Staircase”is based on a classic 1930 Nancy Drew mystery book and is aimed at teens and young teens. Although the story involves a politically motivated kidnapping and a supposedly haunted house, the scariest moment is during what turns out to be a dream sequence. Positive messages include courage and teamwork, and strong role models（mostly female）are at the center of the action.（89 minutes）WONDER PARK（PG）Age 8+Imaginative but intense adventure deals with worry and fear.“Wonder park”is an animated adventure about an imaginative girl named June（voiced by Brianna Denski），who’s spent years dreaming up a magical amusement park named Wonderland with her mom（Jennifer Garner）. You can expect plenty of action（including explosions and peril），as well as the looming presence of worry and sadness, since June is dealing with the fact that her mom has a serious illness. The film celebrates imagination, curiosity and perseverance, and it underlines the importance of not letting fear stop you from being yourself and doing what you love.（93 minutes）CAPTIVE STATE（PG-13）Age 14+Dark, disconnected but smart alien invasion movie.“Captive State”is an alien-invasion movie set in a future Chicago. Some humans try to cooperate with the conquering aliens, while others try to rebel; there’s a very complex plan at the heart of the story. Violence is the biggest issue: Humans are killed, both vaporized by aliens and shot by guns. There are explosions, blood splatters, gory surgeries, gross alien effects, cyanide pills and lots of chaos and stress. The movie is more about its own bigideas than characters or emotions, but it’s smart enough that it should please most teen and adult sci-fi fans. John Goodman and Vera Farmiga co-star.（109 minutes）FIVE FEET APART（PG-13）Age 13+Strong acting saves predictable, sentimental love story.“Five Feet Apart”is based on the best-selling YA novel about Will（Cole Sprouse）and Stella（Haley Lu Richardson），two hospitalized 17-year-olds with cystic fibrosis（囊胞性纤维症）who fall in love. The story promotes treasuring those closest to you and has themes of perseverance and empathy.（115 minutes）60. If you are hooked on science fictions, which movie will you prefer according to the passage?A. WONDER PARKB. NANCY DREW AND THE HIDDEN STAIRCASEC. FIVE FEET APARTD. CAPTIVE STATE61. Which of the following statement is TRUE according to the passage?A. It’s appropriate to watch the film“Captive State”with a younger sister aged 5.B. The movie“Wonder Park”can teach you to be brave enough to face fear.C. It’s advisable of you to watch“Five Feet Apart”if you are free for one and half hours.D.“Nancy Drew and the Hidden Staircase”is adapted from a best-selling novel.62. After reading the passage, we can _____.A. know about the background of the film productionB. learn about the popularity of these filmsC. gain a thorough understanding of the filmsD. have the best option for the film we wantCThe company that revolutionized the delivery of information now aims to do the same with electricity. Technology powerhouse Google today announced it would spend "tens of millions" of dollars next year in research and development and investments in an effort to drive down the cost of large-scale renewable energy to make it cheaper than coal. Not only will Google be hiring engineers and energy experts for its new initiative,known as RE<C (renewable energy at less cost than coal), but it also will make investments in new companies—starting with those that focus on solar-thermal technology, enhanced geothermal, and high-altitude wind power."Cheap renewable energy is not only critical for the environment but also vital for economic development in many places where there is limited affordable energy of any kind," said Sergey Brin, Google co-founder and president of technology, in a prepared statement.Coal supplies 40 percent of the world's electricity and more than half of U.S. power, and if current trends continue, it is expected to grab an ever increasing share because it is a plentiful and cheap fuel for big consumers like the United States and Russia. But coal is also the worst fuel in its production of the global warming gas carbon dioxide. Google co-founder Larry Page said the company's goal is to produce one gigawatt（十亿瓦特）of renewable energy capacity that is cheaper than coal within "years, not decades." Google says that's enough electricity to power a city the size of San Francisco (about 330,000 households).Google, located in Mountain View, Calif., said it was initially working with two other California companies. They are eSolar, of Pasadena, which is specializing in solar-thermal power, using large fields of mirrors to concentrate sunlight and generate steam to run utility-scale electric turbines（涡轮）, and Makani of Alameda, which is developing wind energy technology that takes advantage of the much stronger and more reliable currents available at high altitudes.Google did not specify how much money it was putting into its projects with these companies but said they both had "promising scalable energy technologies." This portion of the initiative will be funded through the company'sphilanthropic arm, Google. org, which is not a traditional charity but can make equity（股票）investments in companies. Brin and Page have pledged（抵押）1 percent of Google's equity and profits toward efforts including climate change and global poverty.The RE<C program is the latest of a series of steps Google has taken on climate change. The company says it is on track in its goal to be carbon neutral in the near future.63. Which of the following statements is TRUE of the coal?A. It is a kind of controversial fuel given its large quantity and its harm to the environment.B. It is a plentiful and cheap fuel that will surely earn more market share.C. It will be totally replaced by the renewable energy in years because it produces the worst gas-carbon dioxide.D. It is supported by some enthusiastic countries like U.S. and Russia which rely heavily on the coal64. It can be inferred from the passage that ____.A. Google. org has made some crucial decisions in expanding the companyB. Google. org has focused on exploiting alternatives to traditional energyC. Google. org is a charity organization committed to funding the projects benefiting mankindD. Google. org is an environmental organization that specializes in promoting green fuel65. What can Not be learned about the Re<C Programme?A. It will come true in a few years with the efforts made.B. It is a programme of environmental protection.C. It is one of the measures taken to neutralize carbon.D. It will be realized through investment in solar and wind energy companies.\66. The best title of this passage is ___.A. Google’s RE<C ProgrammeB. Google, the Energy RevolutionaryC. Google, the Environmental ProtectorD. Google’s Renewable Energy ProjectSection CDirections：Read the following passage. Fill in each blank with a proper sentence given in the box. Each sentenceThe annual Venice Carnival is in full swing, with thousands of revelers（狂欢者）gathering the city’s canals and squares in elaborate costumes and extraordinary masks. ___67___The Carnevale di Venezia is thought to date back to the 11th century, making it one of the world’s oldest. Carnivals are held in many Catholic countries; such as Spain and Brazil, where they serve s a last chance to eat, drink and be merry before the deprivation of Lent, the 40 days of fasting（斋戒）that precede Easter.It is thought that the masks allowed Venetians to hide their identities, allowing the poor to mix with the wealthy, breaking strict social order, even if only for a brief and controlled period.___68___ The theme of Carnival 2019 is“Tutta colpa della Luna,”or“Blame the moon,”marking a half-centurysince man first walked on the satellite.To prevent overcrowding, authorities have installed turnstiles at the entrances to the historic St. Marks’ Square, closing it off to new visitors once 23,000 revelers have entered. Costumed revelers are also searched as they enter the square.Venice is situated across a group of 118 small islands that are separated by canals and linked by over 400 bridges. The islands are located in the shallow Venetian Lagoon, an enclosed bay that lies between the mouths of the Po and the Piave Rivers. ___69___ The lagoon and a part of the city are listed as a UNESCO World Heritage Site. Although most visitors stick to the traditional Carnival costumes of baroque gowns and bejeweled masks for women and black capes and threatening masks for men, more and more people are opting for their own unique interpretations.Some visitors use Carnival as an opportunity to show off a fantastic creation they’ve always dreamed of wearing. It doesn’t have to be Venetian. ___70___ At Carnival, everybody is free to be who—or what—they want to be. Perhaps a different gender—or even species. That’s the joy of the mask—nobody knows who or what the person wearing it was before Carnival.Ⅱ. Summary WritingDirections：Read the following passage. Summarize the main idea and the main point(s) of the passage in no more than 60 words. Use your own words as far as possible.71. Gardening can have many positive effects on your physical and mental health. Whether you’re growing fruit and veggies, flowers or succulents, getting your green thumb on can have a surprising number of health benefits for you and your family.Depending on the size of your garden, maintaining it can be a great way to be physically active. This could be as tough as mowing the lawn, or as gentle as getting a good stretch and practice stabilizing yourself while kneeling, sitting or reaching. In fact, gardening is a recommended activity as it can encourage the use of many motor skills, improve endurance and strength and keep you moving.These days, we can buy pretty much any fruit and vegetable we want from the supermarket, at any time of year. But gardening enables us to eat seasonally, which has important benefits for our bodies. For example, asparagus and apricots grow in spring and summer, while Brussels sprouts get going in winter. Eating seasonally can keep healthy eating exciting by encouraging you to try new recipes using in-season produce. You will also get a wider variety of different coloured produce, providing nutritious vitamins and minerals in your diet throught the year as the produce you eat changes with the seasons.Gardening is also a great way to relax, providing opportunities to still the mind and get away from the busyness of everyday life. There is even evidence to suggest that gardening can help case symptoms of mental illnesses like depression and anxiety. Whether you’re gardening by yourself, or getting the whole family involved, it’s a great way to spend some time outdoors, away from screens and to-do lists, and engage with nature. From repetitive tasks like weeding that provide opportunity for meditation, to practicing patience while waiting for plants to grow, gardening is a great exercise for your mind as well as your body.Ⅱ. TranslationDirections：Translate the following sentences into English, using the words given in the brackets.72. 这项新颁布的规定仅适用于一些突发情况。

2019上海奉贤区高三二模英语及答案

2018学年奉贤区调研测试高三英语试卷(201904)I.Listening ComprehensionSection ADirections: In Section A. you will hear ten short conversations between two speakers. At the endof each conversation, a question will be asked about what was said. The conversations and the questions will bespoken only once. After you hear a conversation and the question about it, readthe four possible answers on your paper, and decide which one is the best answer to the question you have heard.1.A. At an airport.B. In an office,C. At a police station.D, At a travel agency.2. A. Down jackets are now on sale,B. She can't wait for the winter to arrive.C. It's hard to know how severe the winter will beD. She needs a warm jacket.3. A. Learning to drive.B. Buying the insurance.C. Buying a carD. Taking a plane,4. A. Erie won't eat vegetable without meatB. Eric likes both vegetable and meatC. Some meat will solve Eric's problemD. Eric is short of vegetable.5. A. He is invasiveB. He is heroicC. He is life-threateningD He is awkward6. A. Reviews of the comedy are negative.B. The reaction to the comedy is varied.C. The review of the newspaper is one sided.D. Media are prejudiced against the comedy.7. A. Deliver the package in person.B. Pick up the package at the post officeC.Ask to have the package delivered to his homeD. Find out the opening hours of the post office8. A. It hasn’t been graded.B. It received a low grade.C. The committee is discussing itD. The woman hasn't handed it in.9. A. He has been to Seattle many tines.B. He has chaired a lot of conferences.C. He holds a high position in his company.D. He lived in Seattle for many years.10. A. It is too late for the man to go to the theatre.B. People have already been standing in line for two hours.C. The man must wait for two hours to buy the ticket.D. The man can buy a special ticket before the drama starts.Section BDirections: In Scion B, you will hear two short passages and one longer conversation, andyou will be asked questions on each of them. The passages and conversation will be read twice,but the questions will be spoken only once. When you hear a question, read the four possible answers on your paper and decide which one would be the best answer to the question you have beard.Questions I1 through 13 are based on the following passage.11. A. They are gardeners.B. They sell vegetables.C. They run a guesthouse:D. They are scientists.12. A. Five hours.B. Eight hours.C. Twelve hours.D. Fourteen hours.13. A. They have deeper roots.B They don't need sunshineC. They have wider leaves.D.'They have bigger flowers.Questions 14 through l6 are based on the following news.14. A. It is produced in small quantities.B. It is sold at a lower priceC. It is served mainly in McDonald's.D. It is grown from cows alone,15. A. The land and the water system have been polluted seriously.B. Not enough meat has been produced to meet people's needsC. Much land has been used up for animals and their food.D. It has consumed fewer and fewer natural resources16. A. Steaks and hamburgersB. Animal rights.C. The food crisis in the future.D. Lab-grown meat.Questions 17 through 20 are based o0 the following conversation17. A. He is an Englishman living in Sweden.B. He prefers hot weather to cold weatherC. He visits London nearly every winter.D. He likes Sweden better than England.18. A. The long nightB. The bad weather.C. The gloomy winterD. The cold houses19. A. Delightful. B. Refreshing. C. Painful D. Frustrating20. A. They work hard and play hard,B. They often stay up late reading.C. They like to go comping in summerD. They try to earn more and spend more,II.Grammar and VocabularySection ADirections: After reading the passage below, fill in the blanks to make the passage coherent and grammatically correct. For the blanks with a given word, fill in each blank with the proper form ofthe given word; for the other blanks, use one word that best fits each blank.How to Make the Most of Y our Lunch HourShould you grab a bite at your desk or eat with your coll That depends on what's on your agenda for the rest of the day.Lunch hours (21)________(get) shorter and shorter and even disappearing in some parts of today's working world. With fewer employees (22)________ (ask) to accomplish more in a day,many Americans treat lunch not as a break but as just another task to squeeze into an already over-booked day.But do quick meals at the desk actually improve productivity over more leisurely meals?The researchers only studied 32 employees, so the findings are debatable. But when they assigned one group to eat at their desks and another to dine with a colleague at a restaurant, they found those who ate lunch together showed a decline (23)________ their performance on tests hat measured concentration, memory and the ability to catch errors and read emotions in facial expressions following lunch than before lunch. Both groups ate the same meals, but those who ate their food alone were only given 20 minutes to consume their food, (24)________ the paired participants were allowed one hour in the restaurant. Those who ate alone did not have as large a drop in their cognitive processing as those who ate in the restaurant.What was responsible for the change? There were too many variables at play to determine which had the strongest influence on cognitive control--was it the companionship or the restaurant environment (25)________ other dinners were present, music was played and the meal was served by wait staff, or was it the longer time to enjoy the meal?(26)________ factor was responsible, the group that took a restaurant lunch break came back more relaxed, say the authors, and that likely affected their cognitive sharpness. Sharing a meal outside the office with a fiend appears to have a (27)________ (calm) effect, and while it reduces intellectual skills, it may develop social harmony and teamwork, which (28) ________ bean important feature of some work tasks."But don't feel sorry for the lone hunger. It turns out (29)________ since they were ableto maintain their cognitive skills following the meal, they might be in a better position (30)________ (think) creatively for projects that require more innovative solutions or approaches. Section BDirection: Fill in each blank with, a proper word chosen from the box. Each word can be usedonly once. Note that there is one word more than you need.A. involvingB. distinguishC. adapted F. gainsG. partially H. amazing D. tailored E. mediumI. definitely J. steer K. implicationsGenes That Make You SmarterThe contributions genes make to intelligence increase as children grow older. This goes against the idea most people hold that as we age, environmental influences gradually overpowerthe genetic legacy (财产) we are born with and may have (31)________ for education"“People assume the genetic influence goes down with age because the environmental differences between people pile up in life," says Robert Plomin. “What w e found was quite (32)________and goes in the other dire ction.”Previous studies have shown variations in intelligence are (33)________ due to genetics. To find out whether this genetic contribution varies with age, Plomin's team gathered data from six separate studies carried out in 4 countries, (34)________ a total of 1100 pairs of twins. 'The researchers tested twins on reasoning, arithmetics etc. to measure a quantity called "G". Each study also included both identical twins, with the same genes, and fraternal twins(异卵双生), sharing about half their genes, making it possible to (35)________ the contributions of genes and environment to their G scores.Plomin's team calculated in childhood, genes account for about 41 percent of the variations in intelligence. In adolescence, this rose to 55 percent;, by young adolescence, it was 66 percentNO one (36)________ knows why the influence from genes should increase with age,but Plomin suggests that as children get older, they become better at handling their environment to suit their genetic needs, and says “kids with with high G will use their environment to develop cognitive ability and choose friends who are like-minded. Children with (37)________ to low Gmay choose less challenging pastimes and activities, further emphasizing their genetic legacy.Is there any way to interfere with the pattern? Perhaps. The evidence of strong heritability (遗传可能性) doesn’t mean that there is nothi n g you can do about it." says Susanner om our own work, the ones that started off with lower IQ scores had higher Jaeggi, “ｆ(38)________ training. Plomin suggests genetic differences may be more emphasized if all children share an identical curriculum instead of it being (39)________ to children's natural abilities. My tendency would be to give everyone a good education, but put more effort into thelower end." he says. Intelligence researchers Paul Thompson agrees: It shows. that educators need to (40)________ ads towards things drawing out their natural talents.Ш. Reading ComprehensionSection ADirection: For each blank in the following passage there are four words or phrases marked A,B, C and D. Fill in each blank with the word or phrase that best fits the context.Open data-sharers are still in the minority in many fields. Although many re searchers broadly agree thatpub1icaccess to raw data would promote science, most are (41)________ to post the results of their own labours online.Some communities have agreed to share online-geneticists, for ex ample, post DNA sequences at the GenBank repository (库). and astronomers are accustomed to (42)________ images of galaxies and stars from, say, the Sloan Digital Sky Survey, a telescope that has observed some 500 million objects-but these remain the (43)________ not the rule. Historically, scientists have (44)________ sharing for many reasons: it is a lot of work, until recently, good databases did not exist: grant funders were not pushing for sharing; it has been difficult to agree on standards for formatting data, and there is no agreed way to assign credit for data.But the (45)________ are disappearing in part because journals and funding agencies worldwide are encouraging scientists to make their data (46)________.Last year, the Royal Society in London said in its report that scientists need to. (47)________ a research culture where data is viewed as private preserve". Funding agencies note that data paid for with public money should be public information. and the scientific community is recognizing that data can now be shared online in ways that were not possible before. To match the growing demand, services are springing up to make it easier to publish research products (48)________ and enable other researchers to discover and cite (引用) them.Although calls to share data often concentrate on the (49)________ advantages of sharing, the practice is not purely beneficial to others. Researchers who share get plenty of personal benefits including more connections with colleagues. improved (50)________ and increased citations. The most successful sharers- those whose data are downloaded and cited the most often-getnoticed, and their work gets used. (51)________ one of the most popular data setson multidisciplinary repository Dryad is about wood density around the world: it has been (52)________ 5700 times. Co-author Amy Zanne thinks that users probably range from climate -change researchers wanting to estimate how much carbon is stored in biomass, to foresters looking for in formation on different grades of trees. I’d much prefer to have my date used by the (53)________ number of people to as their own questions," she says.It's important to allow readers and reviewers to see exactly how you arrive at your results. Publishing data and code allows your science to be (54)________.Even people whose data are less popular can benefit. By making the effort to organize and 1abel files so others can understand them, scientists can become more organized and better disciplined themselves, thus avoiding (55)________later on.41. A. restricted B. reluctant C. desperate D. generous42. A. accessing B. processing C. analyzing D. identifying43. A. assumption B. mystery C. exception D. phenomenon44. A. longed for B. appealed to C. focused on D. objected to45. A. symptoms B. barriers C. advantages D. consequences46. A. controllable B. unique C. reliable D. public47. A. shift away from B. end up with C. give rise to D. build up48. A. secret B. digitally C. ethically D. fairly49. A. materia1 B. individual C. moral D. economic50. A. visibility B. awareness C. condition D. confidence51. A. On the contrary B.As a result C. For example D. After all52. A. downloaded B. updated C. optimized D. addressed53. A. moderate B maximum C. average D. estimated54. A. reversible B. profitable C. reproducible D. recognizable55. A. crisís B. confusion C. risk D. conflictSection BDirections: Read the following three passages. Each passage is followed by several questions orunfinished statements. For each of them there are four choices marked A, B, C and D. Choose theone that fits best according to the information given in the passage you have just read.AIt was 1961 and I was in the fifth grade. My marks ín school were miserable and, thething was, 1 didn't know enough to really care. My older brother and I lived with Mom in ahumble house in Detroit. We watched TV every night.But one day Mom changed our world forever. She turned off the TV. Our mother hadonly been able to get through third grade. But, she was much brighter and smarter than we boysknow at the time. She had noticed something in the suburban houses she cleaned--books. So shecame home one day, snapped of the TV, sat us down and explained that her sons were going tomake something of themselves, . You boys are going to read two books every week, " she said. "And you're going to write a report on what you read."We complained about how unfair it was. Besides, we didn't have any books in the houseother than Mom s Bible. But she explained that we would go where the books were: " I'll driveyou to the library.'So pretty soon there were these two peevish boys sitting in her white 1959 Oldsmobileon their way to Detroit Public Library. I wandered reluctantly among the children’s books. animals, so when I saw some books that seemed to be about animals, I started leafing throughthem.The first book I read clear through was Chip the Dam Builder. It was about beavers. Forthe first time in my life I was lost in another world. No television program had ever taken me sofar away from my surroundings as did this virtue visit to a cold stream in a forest and theseanimals building a home.It didn’t dawn on me at the time, but the experience was quite different from watchingTV. There were images forming in my mind instead of before my eyes. And I could return to themagain and again with the flip of a page. Soon I began to look forward to visiting this quietsanctuary form my other world.Now my older brother is an engineer and I am a doctor. Sometimes I still can’t believemy life’s journey, from a failing and indifferent student in a Detr oit public school to this position,which takes me all over the world to teach and perform critical surgery.But I know when the journey began the day Mom switched off the TV set and put us inher Oldsmobile for that drive to the library.56. We can learn from the beginning of the passages that ________.A the author and his brother had done well in schoolB. the author had been very concerned about bis school workC. the author had spent much time watching TV after schoolD. the author had realized how important school was57.According to the passage which of the following words can best describe the author's mother?A. Tolerant and decisive.B. aggressive and open-minded.C. Determined and farsighted.D. Persistent and literate.58. The underlined word "peevish" in the passage can be replaced by________.A. naughtyB. bad-temperedC. patientD. obedient59. The author began to love books for the following reasons EXCEPT that ________.A. he could constantly review the plots in the booksB. he could visualize what he read in bis mindC. he could get many rewards from his motherD. he realized that books offered him new experienceBNANCY DREW AND THE HIDDEN STAIRCASE (PG)Age 10+Sparkling book adaptation has great characters, some scares.Nancy Drew and the Hidden Staircase" is based on a classic 1930 Naney Drew mystery book and is aimed at tens and young ten. Although the story involves politically motivated kidnapping and a supposedly haunted house, the scariest moment is during what turns out to be a model dream sequence. Positive messages include courage and teamwork, and strong role (mostly female) are at the center of the action (89 minutes)WONDER PARK (PG)Age 8+Imaginative but intense adventure deals with worry and fear"Wonder Park" is in animated adventure about an imaginative girl named June (voicedby Brianna Denski), who’s spent years dreaming up a magical amusement park named Wonderland with her mom (Jennifer Granner). You can expect plenty of actions (including explosions and perils), as well as the looming presence of worry and sadness, since June is dealing with the fact that her mom has a serious illness. The film celebrates imagination, curiosity and perseverance, and it underlines the importance not letting fear stop you from being yourself and doing what you love. (93 minutes)CAPTIVE STATE (PG- 13)Age 14+Dark, disconnected but smart alien invasion movie"Captive State" is an alien-invasion movie set in a future Chicago. Some humans try to cooperate with the conquering aliens, while others try to rebel; there's a very complex plan at the heat of the story. Violence is the biggest issue: Humans are killed both vaporized by aliens andshot by guns. There are explosions, blood splatters gory surgeries, gross alien effects, cyanide pills and lots of chaos and stress, The movie is more about its own big ideas than about characters or emotions, but it's smart enough that it should please most teen and adult sci-f?fans. John Goodman and Vera Farmiga co-star. (109 minutes)FIVE FEET APART (PG-13)Age 13+Strong acting saves predictable, sentimental love storyFive Feet Apart" is based on the best selling YA novel, about Will (Cole Sprouse) and Stella (Haley Lu Richardson), two hospitalized 17-year-olds with cystic fibrosis (囊胞性纤维症) fall in love, The story promotes treasuring those closest to you and has themes of perseveranceand empathy. (115 minutes)60. If you are hooked on science fictions, which movie will you prefer according to the passage?A. WONDER PARKB. NANCY DREW AND THE HIDDEN STAIRCASE.C. FIVE FEET APART.D. CAPTIVE STA TE.61 Which of the following statements is TRUE according to the passage?A. It’s appropriate to watch the fil m “Captive State” w i th a younger sister aged 5.B. The movie "Wonder Park" can teach you to be brave enough to face fearC. It's advisable of you to watch "Five Feet Apart" if you are free for one and half hoursis adapted from a best-selling novel.D. “Nancy Drew and the Hidden Staircase”　62 After reading the passage, we can________.A. know about the background of the film productionB. learn about the popularity of these filmsC. gain a thorough understanding of the filmsD. have the best option for the film we wantCThe company that revolutionized the delivery of information now aims to do the samewith electricity. Technology powerhouse Google today announced it would spend "tens of millions" of dollars next year in research and development and investments in an effort to drivedown the cost of large-scale renewable energy to make it cheaper than coal. Not only will Googlebe hiring engineers and energy experts for its new initiative, known as RE<C (renewable energy at less cost than coal), but it also will make investments in fledgling companies—starting with those that focus on solar-thermal technology, enhanced geothermal, and high-altitude wind power. "Cheap renewable energy is not only critical for the environment but also vital for economic development in many places where there is limited affordable energy of any kind," said Sergey Brin, Google co-founder and president of technology, in a prepared statement.Coal supplies 40 percent of the world's electricity and more than half of U.S. power, andif current trends continue, it is expected to grab an ever increasing share because it is a plentifuland cheap fuel for big consumers like the United States and Russia. But coal is also the worst fuelin its production of the global warming gas carbon dioxide. Google co-founder Larry Page said the company's goal is to produce one gigawatt(十亿瓦特) of renewable energy capacity that is cheaper than coal within "years, not decades." Google says that's enough electricity to power a city the size of San Francisco (about 330,000 households) .Google, located in Mountain View, Calif., said it was initially working with two other California companies. They are eSolar, of Pasadena, which is specializing in solar-thermal power, using large fields of mirrors to concentrate sunlight and generate steam to run utility-scale electric turbines (涡轮), and Makani of Alameda, which is developing wind energy technology that takes advantage of the much stronger and more reliable currents available at high altitudes.Google did not specify how much money it was putting into its projects with these companies but said they bot h had “promising s calable energy technology”. This portion of the initiative will be funded through the company's' philanthropic arm, , which is not a traditional chanty but can make equity (股票) investments in companies Brin and Page have pledged (抵押) 1 percent of Google's equity and profits toward efforts including climate changeand global poverty.The RE<C program is the least of a series of steps Google has taken on climate change. The company say it is on track in its goal to be carbon neural in the near future.63. Which one of the following statements is TRUE of the coal?A. It is a kind of controversial fuel given its large quantity and its harm to the environmentB. It is plentiful and cheap fuel hat will surely earn more market share.C. It will be totally replaced by the renewable energy in years because it produces the worstgas-carbon dioxide,D. It is supported by some enthusiastic countries like US and Russia which rely heavily on thecoal64. It can be inferred from the passage that _________.A. has made some crucial decisions in expanding the companyB. has focused on exploiting alternatives to traditional energyC. Google. org is a charity organization committed to funding the projects benefiting mankindD. is an environmental organization that specializes in promoting green fuel65. What can Not be learned about the RE<C Programme?A It will come true in a few years with the efforts made.B. It is a programme of environmental protectionC. It is one of the measures taken to neutralize carbonD. It will be realized through investments in solar and, wind energy companies.66. The best title of this passage is ________.A. Google's RE<C ProgrammeB. Google, the Energy RevolutionaryC. Google, the Environmental ProtectorD. Google's Renewable Energy ProjectSection CDirections: Read the following passage. Fill in each blank with a proper sentence given in the box. Each sentence can be used only once. Note that there are two more sentences than you need.A. This year's Carnival festivals kicked off' on February 16 and go on until March 5.B. During the 18 days of Carnival, the city fills with thousands of tourists from across Italy andaround the world.C. Parts of Venice are well known for the beauty of their settings, their architecture and artwork.D. The Italian government decided to bring back the history and culture of Venice by seeking touse the traditional Carnival.E. It doesn't have to be traditional.F. Carnival virtually disappeared when Napoleon's troops brought an end to the V enetian Republicin 1797.Venice CarnivalThe annual Venice Carnival is in full swing, with thousands of revelers (狂欢者)gathering the city's canals and squares in elaborate costumes and extraordinary masks.(67)____________The Carnevale di Venezia is thought to date back to the 11th century, making it one ofthe world’s oldest. Carnivals are held in many Catholic countries, such as Spain and Brazil, wherethey serve as a last chance to eat, drink and be merry before the deprivations of Lent, the 40 daysof fasting（斋戒）that precede Easter.It is thought that the masks allowed Venetians to hide their identities, allowing the poorto mix with the wealthy, breaking strict social order, even if only for a brief and controlled period.(68) ___________ The theme of Carnival 2019 is “Tutta colpa della Luna,”or “Blame the moon, marking a half-century since man first walked on the satellite.To prevent overcrowding, authorities have installed turnstiles at the entrances to theSquare, closing it off to new visitors once 23,000 revelers have entered.historic St. Marks’　Costumed revelers are also searched as they enter the square.Venice is situated across a group of 118 small islands that are separated by canals andlinked by over 400 bridges. The islands are located in the shallow Venetian Lagoon, an enclosedbay that lies between the mouths of the Po and the Piave Rivers. (69)___________ The lagoonand a part of the city are listed as a UNESCO World Heritage Site.Although most visitors stick to the traditional Carnival costumes of baroque gowns andbejeweled masks for women and black capes and threatening masks for men, more and morepeople are opting for their own unique interpretations.Some visitors use Carnival as an opportunity to show off a fantastic creation they'vealways dreamed of wearing. It doesn't have to be Venetian. (70) ____________ At Carnival,everybody is free to be who--or what--they want to be. Perhaps a different gender-- or evenspecies. That's the joy of the mask--nobody knows who or what the person wearing it was beforeCarnival.IV. Summary WritingDirections: Read the following pas Summarize the main idea and the main point(s) of the passagein no more than 60 words. Use your own words as far as possible71. Gardening can have many positive effects on your physical and mental health. Whetheryou’re growing fruit and veggies, flowers or succulents, getting your green thumb on can have asurprising number of health benefits for you and your family.Depending on the size of your garden, maintaining it can be a great way to be physicallyactive. This could be as tough as mowing the lawn, or as gentle as getting a good stretch andpractice stabilizing yourself while kneeling, sitting or reaching. In fact, gardening is arecommended activity as it can encourage the use of many motor skills, improve endurance andstrength and keep you moving.These days, we can buy pretty much any fruit and vegetable we want from thesupermarket, at any time of year. But gardening enables us to eat seasonally, which has importantbenefits for our bodies. For example, asparagus and apricots grow in spring and summer, whileBrussels sprouts get going in winter. Eating seasonally can keep healthy eating exciting byencouraging you to try new recipes using in-season produce. You will also get a wider variety ofdifferent coloured produce, providing nutritious vitamins and minerals in your diet throughout the。

天文学中的数值模拟SDSS的模拟星表

天文学中的数值模拟:SDSS的模拟星表斯隆数字巡天（SDSS）是如今最具影响力的天文项目之一，它得出的数据是无数星系天文学以及宇宙学研究者的重要资料。

不过本文要说的不是SDSS得出的真实星表，而是该项目使用的模拟星表。

在项目的预研期，以宇宙学数值模拟为基础的模拟星表起了关键的论证作用。

为了得到直观印象，不妨先比较一下模拟星表中的星系随红移的分布与真实巡天得到的分布：SDSS模拟星表中的星系分布（上）以及真实的星系分布（下），其中下图对应的纵深比上图大一些，为20亿光年。

（图片提供：Sloan Digital Sky Survey）不提其他，乍看两张图真的很类似。

换句话说，当代由数值模拟创建的虚拟宇宙在形态上已经和实际的宇宙很接近了。

当然，这是SDSS模拟星表真正能发挥作用的前提。

构造SDSS模拟星表的基础是Lambda-CDM模型，也就是Lambda-冷暗物质模型。

它是大爆炸宇宙学的基础模型，也是最简单的一种理论，可以解释微波背景辐射的形成、星系团大尺度结构以及宇宙的加速膨胀等观测事实。

在这一框架下，Lambda指与暗能量相关的宇宙学常数，暗物质成分以非重子的低速物质为主，用Friedmann方程、Friedmann–Lemaitre–Robertson–Walker度规和宇宙状态方程描述可观测宇宙，而基本参数则包括重子密度、暗物质密度、暗能量密度、再电离光深、标量谱指数和曲率涨落振幅6个，包括哈勃常数在内的其他参数可以由这6个基本参数导出。

SDSS的模拟星表采取的参数是以20世纪90年代初COBE卫星的测量为基础的，所以与现在WMAP给出的新值相比有很大的差异，比如哈勃常数是在60上下，而非70有余。

另外由于在90年代末，人们只是刚刚发现了宇宙加速膨胀的迹象，暗能量的存在尚未被更多Ia型超新星的观测所证实，因此这里所谓Lambda-CDM，实际上是确切的CDM，再加上为了保持时空平直而单纯从理论上引入的宇宙学常数Lambda。

C u r i o s i t y 算法

机器学习为NASA贡献了什么？机器学习为NASA贡献了什么？策划 | 李冬梅NASA 不仅是软件工程的鼻祖，在软件架构方面的造诣也是极为先进的。

我们曾经编译过《太空不惧宕机，软件工程鼻祖 NASA 是怎么做到的？》。

毫不意外的是，在机器学习领域中，NASA 也丝毫不逊于那些世界级科技大厂，让我们来看看，NASA 都使用了哪些机器学习技术？机器学习在太空探索中必不可少从研究地球外层大气到寻找其他星球上的生命迹象，都有 NASA 参与的痕迹。

在当今这个万物离不开数据的时代，机器学习在太空发现领域扮演着重要的角色。

NASA 的各种航天器和卫星所生成的数据量惊人（举个例子，仅斯隆数字化巡天（Sloan Digital Sky Survey ）一个项目，未来将生成 5000 多万张星系的图像），因此，为了识别这些数据中的模式，机器学习是必不可少的。

未来，机器学习还可以用来检测宇航员在太空中的健康状况、进行航天器的智能化维修、在其他星系中发现更多的行星以及进行一些更为奇妙的探索。

事实上，只要涉及到太空和机器学习，就意味着有无限可能。

这里，我们就先来了解下 NASA 都使用了哪些机器学习应用来进行太空探索。

NASA 用到的机器学习应用火星上的漫游车：勇气号和机遇号如果你认为 Tesla、Google、Uber 等是第一批大举投资自动驾驶汽车的公司可能就错了，实际上，早在十年前，NASA 就已经为发明了可以用在火星上的无人驾驶探测车——火星漫游车（Self-Driving Rovers on Mars）。

2004 年，火星漫游车“勇气号”（Spirit）和“机遇号”（Opportunity）就搭载了一套基于机器学习的导航和驾驶系统，称为AutoNav。

2011 年发射的另一辆火星漫游车“好奇号”（Curiosity），也搭载了 AutoNav，直至现在，这辆火星漫游车仍然在火星上进行探索，它的任务是寻找水以及其他能够使火星适合人类去探索的物质。

宇宙探索与发现课后答案

练习题答案1.（B ）较正确地反映了太阳系的实际，为以后开普勒总结出行星运动定律，伽利略、牛顿建立经典力学体系铺平了道路，从根本上动摇了“人类中心论”的神话。

A.托勒玫的地心说B.哥白尼的日心说C.银河的系发现D.广阔恒星世界的发现2.科学家根据拍照发现，几乎所有宇宙星系的某种元素的光谱线，相对于地球实验室内同种元素的广谱线，都具有明显而普遍的（C ）现象，于是根据物理学的多普勒效应，科学家进一步得出了“目前宇宙正在膨胀”的结论。

A. 减弱；B. 增强；C. 红移；D. 蓝移3.1718年，（A ）将自己的观测数据同1000多年前托勒玫（Claudius Ptolemaeus，约90-168）时代的天文观测结果相比较，发现有几颗恒星的位置已有了明显变化，首次指出所谓恒星不动的观念是错误的。

A.哈雷B.哈勃C.斯特鲁维D.勒维特4.18-19世纪中期，（C ）兄妹及父子，通过数遍天上星星等大量观测事实提出“银河是一个星系”的观点，第一次为人类确定了银河系的盘状旋臂结构，把人类的视野从太阳系伸展到10万光年之遥，树立了继哥白尼以后开拓宇宙视野的第二个里程碑。

A.伽利略B.哈雷C.威廉·赫歇尔D.哈勃5.爱因斯坦是现代宇宙学的奠基人，他根据理论推算得出，宇宙是一个“有限、无界、静态的体系”，这个结论打破了以往“宇宙无限”的错误观点，但是其中关于“宇宙是静态”的说法却被现代天文学观测到的（D ）的事实所否定。

A.宇宙无限大B.宇宙不可测量C.宇宙在收缩D.宇宙在膨胀6.哈勃在上世纪中叶发现的星系光谱线的红移速度v与星系离我们的距离r之间存在着的关系是（D ）。

A.r=H/vB.r=HvC.r=1/HvD.r=v/H7.类星体、恒星、行星及生命出现的年代大约距大爆炸的起点时刻（B ）。

A.1亿年B.10亿年C.100亿年D.120亿年8.目前所知的“宇宙大爆炸”理论的最强有力的证据是（C ）。

A.轻元素的丰度B.古老恒星的年龄C.宇宙微波背景辐射D.星系光谱的普遍红移9.综合先进的观测技术和仪器所获得的的数据发现，约50亿年前宇宙开始加速膨胀，其动因是神秘的（D ）。

英文好文翻译一组(英汉对照)

Using gravitational "lenses" in space, University of Utah astronomers discovered that the centers of the biggest galaxies are growing denser -- evidence of repeated collisions and mergers by massive galaxies with 100 billion stars. "We found that during the last 6 billion years, the matter that makes up massive elliptical galaxies is getting more concentrated toward the centers of those galaxies. This is evidence that big galaxies are crashing into other big galaxies to make even bigger galaxies," says astronomer Adam Bolton, principal author of the new study."Most recent studies have indicated that these massive galaxies primarily grow by eating lots of smaller galaxies," he adds. "We're suggesting that major collisions between massive galaxies are just as important as those many small snacks."The new study -- published recently in The Astrophysical Journal -- was conducted by Bolton's team from the Sloan Digital Sky Survey-III using the survey's 2.5-meter optical telescope at Apache Point, N.M., and the Earth-orbiting Hubble Space Telescope.The telescopes were used to observe and analyze 79 "gravitational lenses," which are galaxies between Earth and more distant galaxies. A lens galaxy's gravity bends light from a more distant galaxy, creating a ring or partial ring of light around the lens galaxy.The size of the ring was used to determine the mass of each lens galaxy, and the speed of stars was used to calculate the concentration of mass in each lens galaxy.Bolton conducted the study with three other University of Utah astronomers -- postdoctoral researcher Joel Brownstein, graduate student Yiping Shu and undergraduate Ryan Arneson -- and with these members of the Sloan Digital Sky Survey: Christopher Kochanek, Ohio State University; David Schlegel, Lawrence Berkeley National Laboratory; Daniel Eisenstein, Harvard-Smithsonian Center forAstrophysics; David Wake, Yale University; Natalia Connolly, Hamilton College, Clinton, N.Y.; Claudia Maraston, University of Portsmouth, U.K.; and Benjamin Weaver, New York University.利用引力透镜”的空间，犹他大学的天文学家发现的最大的星系的中心，越来越密集的恒星的星系——100000000000多次的碰撞和合并的证据。

2017年6月大学英语六级考试真题及答案解析(第二套加第三套)

2017年6月大学英语六级考试真题及答案解析（第二套完整版）Part I Writing (30 minutes)Directions: Suppose you are asked to give advice on whether to major in science or humanities at college, write an essay to state your opinion. You are required to write at least 150 words but no more than 200 words.【参考范文】Whether to Major in Science or Humanities at College?Nowadays, as the whole society place increasingly considerable value on education, the question of whether to major in science or humanities at college is not only a concern for students, but also a focal point for parents. Some believe that to dig into science is a better choice because it promises us a brighter future; others may hold the opposite view that humanity knowledge is the foundation of humanity quality.As for me, both arguments are justified. However, I believe that the important thing is not about which subject is better, what matters most is people who will have to make the decision. In other words, we should not lay one-sided emphasis on the advantages of either subject; on the contrary, the students themselves, their interests and preferences, pros and cons are supposed to be taken into consideration. For example, if a student is more adept at humanity and that’s where his real interests lie, then he should dedicate to the study on humanity.Whether to major in science or humanities is a critical choice for every student because its result has a profound influence on personal career development and life style. Thus we should figure out what we really care about so as not to put the cart before the horse.Part II Listening Comprehension (30 minutes)Section ADirections: In this section, you will hear two long conversations. At the end of each conversation, you mil hear four questions. Both the conversation and the questions will be spoken only once. After you hear a question, you must choose the best answer from the four choices marked A), B), C) and D). Then mark the corresponding letter on Answer Sheet 1 with a single line through the centre.Questions 1 to 4 are based on the conversation you have just heard.1. A) Doing enjoyable work. B) Having friendly colleagues.44. Greenhouse gas emissions, if not properly dealt with, will pose endless risks for mankind.45. It is urgent for governments to increase the cost of using fossil fuels to an appropriate level to lessen the catastrophic effects of climate change.36.【解析】[D]。

寻找暗能量存在的证据

寻找暗能量存在的证据天文学家认为，暗能量在宇宙中起斥力作用，但又不能严格说其是一种斥力，只能称其为能量。

宇宙大爆炸时发生膨胀，产生的能量把物质往外排斥，暗能量斥力作用的发现，使学者们认识到，宇宙不光是在膨胀，而且还是在加速膨胀。

暗能量在宇宙中更像是一种背景，让人根本感觉不到它的存在，但它确实存在，且起着非同一般的作用。

有人把暗能量称为“真空能”。

20世纪20、30年代，就有科学家认为真空不空，只是物理的探测仪器探测不到“真空”中并非真的什么都没有。

爱因斯坦的“宇宙常数”对暗能量理论上的猜测可追溯到爱因斯坦年代，1915年爱因斯坦（Albert Einstein，1879-1955）提出了广义相对论，这是自牛顿时代以来第一次出现的重力理论。

1917年，他将广义相对论公式应用到整个宇宙，想看看能否获得对宇宙本质的新认识。

世界上的物理学家、数学家随即开始解其中的引力方程，方程有两种解，结论是宇宙不会完全静止、宇宙没有静止点。

方程的第一种解是，如果宇宙只存在引力，没有别的力作用的话，出于相互吸引，宇宙不可能静止；方程的另一种解是，宇宙爆炸的那一瞬间获得了一个初速度，向外膨胀，但由于引力作用往回拉，宇宙肯定越胀越慢，所以宇宙不是膨胀就是收缩，不可能静止。

爱因斯坦觉得从哲学思想上分析，这两种解都不合适，按他的想法宇宙应该是静止的，不能永不停息地运动。

因此，爱因斯坦又向广义相对论引力方程中引入了一项“宇宙常数”（Cosmological Constant λ）。

这个宇宙常数起排斥力的作用，有了该常数之后，引力方程同时具备了引力和斥力，正好能够达到平衡，可让宇宙“静止”下来。

20世纪20年代，美国著名天文学家哈勃（Edwin Powell Hubble，1889-1953）经过观测发现，宇宙确实是在不断膨胀，他根据星系的距离和运行速度证实，离我们越远的星系向外运动的速度越快，这是宇宙正在膨胀的表现。

这一观测结果完全与引入“宇宙常数”之前的引力方程的计算结果相契合，迅速得到了世界上绝大多数科学家的认可。

天文学中的数字化技术应用

天文学中的数字化技术应用天文学是一门探究宇宙奥秘的科学，在过去的几个世纪中，人们通过望远镜、望远镜阵列等工具不断深入探究着宇宙的秘密。

然而，随着数字化技术的发展，天文学界在今天逐渐将目光投向了更加高精度、高效率的数字化观测和处理手段。

数字化技术对于天文学的意义在于提高了观测的精度和数据处理的效率。

数字化技术的应用不仅仅是在望远镜等观测设备方面，还体现在了天文数据库的建设、数据分析和模型预测等方面。

下面将从数字化观测、数据处理和数据共享三个方面探讨数字化技术在天文学中的应用。

数字化观测数字化技术的发展推动了望远镜的升级，在望远镜的光电探测器和数据采集等方面，数字化技术都发挥着巨大的作用。

数字化技术使得望远镜产生的数据可以通过网络传输和储存，便于观测数据的分析和处理。

数字技术的应用不仅提高了观测精度，还能够将不同观测文件进行压缩处理，减少存储空间，提高数据的传输效率。

在光学望远镜领域，CCD相机是数字技术的代表，现在几乎所有大型光学望远镜都采用CCD相机进行观测。

与传统的底片比较，CCD相机具有观测精度高、曝光时间短、观测效率高、数据保存方便等优点，可以大大提高观测数据的质量和效率。

在射电观测方面，数字技术使得射电天文学观测变得更加高精度和高效率。

维持射电望远镜的观测效率需要大量的校准数据，数字技术的应用使得校准数据的处理变得方便快捷，可以大幅度减少人工干预。

数据处理天文学是一门数据密集型学科，数据处理是天文学研究的基础。

数字技术的发展使得数据处理变得更加精确和快速。

在天文学数据处理方面，数字技术可以提供多点观测数据处理、数据可视化、自动化算法搜索等高效的处理方式，使研究者能够更加精确地处理数据，更加深入地了解数据信息。

数字技术的应用使得天文学处理数据的标准化和模型化得以实现，实现了天文学数据的开放共享。

目前，天文学界有多个数据集合项目在数据处理方面大量使用了数字技术，如：SDSS（Sloan Digital Sky Survey）、HEASARC（High Energy Astrophysics Science Archive Research Center）等。

SDSS黑洞直径

SDSS黑洞直径超大质量黑洞是宇宙中的神秘现象之一。

它们是质量比太阳还要大数千倍甚至上百万倍的黑洞，被认为存在于星系中心。

SDSS（Sloan Digital Sky Survey）对这些黑洞进行了大规模观测和研究。

黑洞的直径和其他性质涉及到许多相关参考内容，如观测结果和理论模型。

首先，观测结果是研究黑洞直径的重要依据。

通过天文观测技术，科学家能够测量黑洞周围物质的运动轨迹，从而间接推断黑洞的大小。

例如，SDSS观测到的超大质量黑洞M87中心的射电天体Sgr A*，它的视直径约为100微弧秒。

这一观测结果是根据地基干涉测量的数据得出的，其详细观测方法和结果报告可以在天文学期刊上查阅。

另外，理论模型也为我们理解黑洞直径提供了支持。

根据广义相对论的理论框架，黑洞是一种引力极强的物体，其直径实际上并不具有物理意义，因为黑洞是一种无限密度的奇点。

但是，黑洞的事件视界（Event Horizon）是由于光无法逃离黑洞引力而形成的区域，可以作为黑洞的边界来研究。

根据Hawking辐射的理论，黑洞也可能存在半径更大的“因而曲率较低的相对缓和地带”，这可能是我们研究黑洞直径的一个方向。

此外，通过天文观测和模拟计算，科学家可以推测超大质量黑洞的大小。

例如，一项基于动态摄谱计研究的研究表明，黑洞的大小可能与星系的速度关系密切相关。

这项研究使用了SDSS提供的数千个星系的观测数据，发现星系的中央黑洞质量与星系速度分散之间存在一种线性关系。

通过这种关系，科学家可以估算出超大质量黑洞的直径。

此外，现代天文学研究还涉及到数值模拟和理论预测。

在宇宙演化的模型中，科学家通过模拟恒星形成和生命周期来研究宇宙中黑洞的起源和演化。

这些模拟通过计算密度、温度、压力等参数来估算黑洞的大小。

例如，某一模拟得出了一个具有百万倍太阳质量的黑洞，黑洞的大小可以通过观测黑洞吸积盘的物质运动来研究。

这种模拟结果被认为是研究黑洞直径的重要参考。

综上所述，研究超大质量黑洞的直径涉及到观测结果、理论模型和数值模拟等多方面内容。

st4导星标准

st4导星标准
ST4导星标准是Sloan Digital Sky Survey (SDSS) 星等系统中的
一个指标，用于描述天体在特定波段（通常是r波段）的亮度。

ST4导星标准是由美国天文学家Kevin R. Hall 设计的，他使用了SDSS数据和u、g、r、i、z波段的天体亮度数据来计算该
指标。

ST4导星标准是一个相对系统，其数值越小表示天体越亮。

ST4导星标准是用于天文观测和导航的重要工具，用于比较和
选定天体的亮度。

它可以帮助天文学家确定观测对象的亮度，并进行星等的标定。

在实际观测中，ST4导星标准常用于引导
望远镜和摄像机，以确保观测到正确亮度的天体。

需要注意的是，ST4导星标准是在SDSS数据集的基础上设计的，并且仅适用于SDSS波段。

对于其他波段的天体亮度测量，可能需要使用不同的标准。

2021国外和国内大规模天文光谱巡天的成果范文1

2021国外和国内大规模天文光谱巡天的成果范文 1、国际上的光谱巡天项目天文学是一门观测的科学,发展大型的天文望远镜是天文学发展的必由之路, 也成为学科发展的重要战略组成部分. 巡天观测是对天体进行普查, 通常是使用大视场望远镜对天空进行覆盖式观测, 这对于天文学研究来说是基础性的工作. 根据终端仪器的区别, 巡天观测分为多色成像巡天和光谱巡天. 多色成像是在望远镜的焦面上放置滤光片和探测器进行观测,可同时获得多个天体的位置和不同波段上的亮度信息. 而光谱观测则是在望远镜焦面上放置光谱仪, 以获得天体的光谱信息. 利用天体的光谱,不但能够确定天体的化学组成, 而且可以确定天体的温度、压力、密度、磁场和运动速度等物理条件. 在 21 世纪, 天文学进入“多波段、大样本、高信息量”时代, 大规模的光谱巡天成为天文观测的突破口, 其目的是获取数以十万、百万甚至千万计天体的光谱, 可以得到成像巡天所不能提供的更加丰富的天体信息. 十多年来国际上开展了一系列的天体光谱巡天项目, 如下所述. (1)2dF 项目英澳天文台的2dF 项目是使用在澳大利亚的英澳天文台的 3.9 m 英澳望远镜, 视场为 2°, 400 根光纤.于 1997 年开始试观测, 2002 年完成观测任务, 共获得了220000 条星系的光谱和 23000 条类星体的光谱. (2)6dF 项目使用在澳大利亚的英澳天文台的1.2 m UK 施密特望远镜, 视场为6°, 150根光纤. 在2001-2006年完成了 12 万个星系的光谱观测. (3)SDSS 项目 SDSS项目使用美国 APO 天文台的口径为 2.5 m的光学望远镜. 它所配备的仪器一是用于成像巡天的大型拼接 CCD 相机, 观测时可以同时得到 5 个波段上的天空图像, 另外是两台光纤光谱仪, 可以同时测量640个天体的光谱. 该项目于 1999 年开始试观测, 于 2005 年完成第一期观测, 2008 年完成第二期观测, 目前正在进行第三期观测. (4)RAVE 使用英澳天文台的1.2 m UK 施密特望远镜, 视场为6°, 150根光纤. RAVE光谱巡天的设计目标是获得南天百万恒星的视向速度以研究银河系的结构和动力学演化. RAVE 在 2003–2005 年进行试观测, 之后进行正式的南天恒星光谱巡天, 在 2013 年发布了57 万颗恒星的窄波段光谱. (5)Gaia Gaia是欧洲空间局的一颗天体测量卫星, 于2013 年 12 月发射. Gaia 将对全天进行多历元的测光和低分辨光谱观测. 它将获得 10 亿颗恒星的三角视差和自行, 还将得到 1.5 亿颗恒星的视向速度和几百万颗恒星的大气参数.本文将以国外的 SDSS 项目和我国自主研制的新型大视场兼大口径光学天文望远镜(LAMOST)为主来介绍大规模天文光谱巡天的结果. 2、SDSS 巡天项目 SDSS是斯隆数字化巡天 (Sloan Digital SkySurvey)项目的简称, 是美国、日本和德国等国的大学和研究所的合作项目. 该项目计划进行成像巡天和光谱巡天的观测,所获得的观测资料将被用以研究宇宙的大尺度结构、星系的形成与演化等天体物理学的重大前沿课题. SDSS使用了一架口径为 2.5 m 的光学望远镜,这样的望远镜在世界上算是中小型的, 但它配备的仪器则是世界领先的. 一是用于成像巡天的大型拼接 CCD 相机, 在相机中有 30 个 CCD 组成了成像部分, 观测时可以同时得到 5 个波段上的天空图像; 在相机中还有 20 个 CCD 用于天体的精确位置测量. 另外是两台光纤光谱仪, 可以同时测量 640 个天体的光谱. 除了 2.5 m 望远镜外, SDSS 还配备了其他辅助的设备, 一个是用于对巡天图像进行光度定标的口径为 0.5 m 的测光望远镜, 另外还有用于对天文观测条件进行监测的“视宁度监视仪”和“红外云量照相机”等仪器. 2.1SDSS 成像巡天在SDSS 的成像巡天计划中, 对整个天空的三分之一天区进行了 5 个波段上的成像观测, 这些天区是银河系星际物质对光线的吸收效应最小的天区(图 1).【图1-8略】 SDSS成像巡天的深度和观测到的天体数目达到前所未有的水平, 它将观测到所有亮于 23 星等的天体,主要包括约五千万个星系、一百万颗类星体和八千万颗恒星. SDSS 在获得成像巡天的观测数据后, 通过自动处理软件来对巡天图像中的天体进行检测, 并确定它们的位置、形态和在 5 个波段上的亮度(五色星等). 利用SDSS 成像巡天所得到的上亿个天体的参数, 可以将星系和类星体从中挑选出来. 例如, 利用天体形态的延展性来挑选出星系, 而利用天体的五色星等可以将类星体从绝大多数恒星中区分出来(图2). SDSS 将依此选择出一百万个星系和十万个类星体来进行光谱巡天的观测. 2.2SDSS 光谱巡天 SDSS光谱巡天的主要任务是确定宇宙的大尺度结构, 其方法是对一百万个星系进行光谱观测(图3(a)-(f)), 有了星系光谱就能得到星系的红移, 根据红移就有可以确定星系的距离, 由此可以得到星系在宇宙中的三维分布(图 4), 从而可以研究宇宙的结构和星系的演化等问题. 由于 SDSS 观测星系光谱的数目比以前多了十倍, 因此可以更加精确地揭示出宇宙中的结构是什么样的. 同时, 通过 SDSS 的光谱巡天, 不但可以了解星系和类星体在空间上的分布,而且可以了解它们在时间上的演化. SDSS 观测到的星系和类星体可以远达数十亿光年甚至上百亿光年,也就是看到它们在数十亿年到上百亿年前的样子. 因此,比较不同距离上的星系和类星体的物理特性,就可以研究它们随时间的演化过程. 另外, SDSS 所获得的上百万个类星体的光谱可以用来探测宇宙中遥远的星系间的物质分布. 这是因为类星体距离我们十分遥远, 在其光线传播过程中会被星系间的物质吸收掉特定波长上的光, 从而可以用来研究宇宙的演化历史. SDSS在 2013 年 7 月发布的 DR10 数据集, 其中包括近 500 亿天体的测光数据, 以及 180 万星系光谱、31 万类星体光谱、74 万恒星光谱等. 当前, 世界上已有了近十架口径为 8–10 m 的光学望远镜, 而SDSS 使用的望远镜只能算是中小型的 . 但由于SDSS 项目选择了大视场巡天的目标, 并使之达到了前所未有的深度、广度和精度, 因此 SDSS 将会极大地推动人类对宇宙的认识. 近些年来, SDSS 一直是被学术论文引用最高的天文设备, 甚至超过了耗资巨大的地面和空间大型天文设备. 3、LAMOST 光谱巡天 3.1LAMOST 的特点 LAMOST的全称是“大天区面积多目标光纤光谱天文望远镜”(The Large Sky Area Multi-object FiberSpectroscopic Telescope). LAMOST的光学系统是视场 5° 、通光孔径3.6–4.9 m 的主动反射施密特系统(王-苏反射施密特系统), 它由施密特改正镜 Ma、球面主镜 Mb 和焦面组成(图 5). 其反射施密特改正镜 Ma(5.72 m×4.40m)是由 24 块对角线长 1.1 m、厚度为 25 mm 的六角形子镜拼接而成. 球面主镜 Mb(6.67 m×6.05 m)是由37 块对角线长 1.1 m、厚度为 75 mm 的六角形球面子镜拼接而成. LAMOST 球面主镜固定在地基上, 反射施密特改正镜放置在主镜北端, 两者之间通过 40多米的高精度镜筒连接, 望远镜的焦平面位于镜筒内. 观测天体时,通过 Ma 跟踪就可将赤纬-10°到+90°的天体尽收眼底. 天体的光经Ma 反射到 Mb,再经 Mb 反射后成像在焦面上. 焦面上放置的光纤将天体的光传输到光谱仪的狭缝, 最终通过光谱仪分光后由 CCD 照相机记录下天体的光谱. LAMOST开创了一种新的望远镜类型(大视场兼大口径望远镜), 打破了大视场望远镜不能兼有大口径的瓶颈, 被国际上誉为“建造地面高效率的大口径望远镜最好的方案”. LAMOST 首次在世界上在一块大镜面上同时应用薄镜面(可变形镜面)主动光学技术和拼接镜面主动光学技术; 首次在世界上实现六角形的主动可变形镜面; 首次在世界上在一个光学系统中同时采用两块大口径的拼接镜面; 首次在世界上应用 4000 根光纤的定位技术. LAMOST 成为我国最大的光学望远镜(主镜口径为 6 m), 将成为国际上最大的大视场望远镜, 将使人类观测天体光谱的数目提高一个数量级, 使我国在大视场多目标光纤光谱观测方面处于国际领先地位. LAMOST将对人类认识宇宙的起源、星系的形成与演化、银河系的结构、恒星的演化等诸多的研究领域做出重大的贡献. 在建设 LAMOST 过程中发展起来的新技术大大的推动了我国在光学仪器的制造、精密机械、电子技术、海量数据处理等技术科学领域的发展, 并为我国正在预研的下一代 30–100 m极大光学/红外望远镜、为我国的科研、生产和国防建设的发展提供可靠的技术储备. 3.2LAMOST 巡天观测 LAMOST项目作为重大科学工程于 1997 年 8 月由国家立项, 2001 年 8 月开工, 2009 年 6 月通过国家验收. 经过两年紧张有序的调试和科学试观测后, 启动了LAMOST 的巡天观测(图 6). LAMOST先导巡天自 2011 年 10 月 24 日开始,到 2012 年 6 月 24 日结束, 共观测 401 个天区, 获得54 万条信噪比大于 10 的恒星光谱和 37 万颗恒星参数星表. 2012 年 9 月 28 日, LAMOST 正式巡天启动,2013 年 6 月 15 日圆满结束第一年巡天观测, 共观测689 个天区(图 7), 获得 117 万条信噪比大于 10 的恒星光谱和 71 万颗恒星参数星表. 包括先导巡天和第一年正式巡天的光谱数据——DR1 数据集于2013 年8 月 26 日正式释放, 供国内用户和国外合作者使用. DR1释放光谱数共计 220 万, 其中信噪比大于 10 的恒星光谱 172 万条, 已然超过目前世界上所有已知恒星巡天项目的光谱总数. 在 DR1 发布的数据中, 还包括一个108 万条恒星光谱参数星表, 也是目前世界上最大的恒星光谱参数星表. 截止到2013年底, 利用 LAMOST巡天光谱数据已经取得了一系列较高质量研究成果. (1) 在M31/M33 及其邻近的 135 平方度区域内新发现 500多颗类星体, 这是目前我国天文学家利用自主设备在该天区发现的世界上数目最多的类星体样本等. 这些类星体可用来探测M31/M33 及其周围子结构中星际介质的化学组成、分布和运动学信息. (2) 发现了近 3000 颗白矮星, 其中 206 颗是新发现的 DA 型白矮星. 白矮星是恒星演化晚期的代表性产物, 它可用来独立确定星团年龄. 白矮星的光度函数可确定恒星形成率和银河系的演化历史. (3) 捕获 28 颗白矮-主序双星, 其中发现2 颗是共包层后双星候选体, 共包层后双星是激变变星和 Ia 型超新星的前身,对研究共包层演化具有重要意义. (4) 从 157 颗天琴 RR 变星中探测到了 3 颗天琴 RR 变星存在超高声速激波现象. 天琴 RR 变星对恒星结构与演化,银河系的形成和宇宙学的研究有重要意义. (5) 新发现了 17 颗贫金属恒星候选体, 为研究银河系形成和化学演化及早期宇宙中的恒星形成提供了观测限制. (6)在 LAMOST 先导巡天的数据中共发现了 10 个激变变星, 其中 2 个是最新发现. 激变变星对研究恒星和密近双星的结构演化、检验和发展吸积盘理论具有重要的作用和意义. (7) 美国合作团队对 LAMOST先导巡天期间获取的 400000 颗恒星的大样本光谱进行分析研究, 发现银河系盘星的运动模式并非简单的圆周运动. (8) 新发现一颗距地球最近的超高速. 2013年 9 月 10 日, LAMOST 第二年正式巡天顺利启动. 从先导巡天开始到 2014 年 3 月, LAMOST光谱巡天已经获得超过 300 万的天体光谱, 其中有270 万恒星光谱. 利用 LAMOST 所获得的恒星光谱巡天数据, 可以得到海量的恒星光谱参数即有效温度、表面重力、化学组成和视向速度等(图 8). 结合国内外其他的天文观测数据, 天文学家们不仅可以探知银河系的物质(特别是暗物质)分布, 还将揭示银河系中各组分的化学和动力学特征. 恒星的化学组成就如同化石一样, 可以用来追踪银河系漫长的演化历史, 探究星系起源和演化的规律. 这些研究将使人们对银河系的了解提高到前所未有的高度, 也将启发人们对宇宙的形成和演化产生更加深刻的认识. LAMOST恒星光谱巡天有望在 5 年时间里获得超过 500 万条高质量的恒星光谱, 海量的恒星光谱数据将成为“数字银河系”的重要基石, 对于研究银河系的结构、运动、形成和演化具有重要的科学研究价值. 基于 LAMOST 光谱数据开展的研究, 将取得一系列标志性科研成果, 培养一批实测和理论天体物理学家, 为我国在相关领域跻身世界先进行列做出重大贡献. 4、结论自伽利略发明第一台折射望远镜以来的400 年间, 光学天文学一直在天文学中占据主导地位, 光谱分析也是目前天文学研究中最为成熟的工具之一. 大规模光学光谱巡天不仅可以提供河外、河内的天体的红移或速度信息来研究宇宙的大尺度结构、银河系结构,可以对观测到的海量星系、类星体、恒星进行分类并进行其性质的统计研究, 还可以搜寻各种特殊天体. 这些巡天还建立各种天体的数据库, 为多波段甚至全波段研究各类天体提供全面的光学信息. 目前正在进行的天文大规模光谱巡天项目有SDSS、LAMOST和 Gaia. 作为光谱获取率最高的天文望远镜, LAMOST 对光学天文学的意义是不言而喻的, 正如 LAMOST 国际评估报告(2005 年 6 月)所指出的那样: “LAMOST 将会是一个适合于研究广泛领域中重大天体物理问题的世界级巡天设备.” “LAMOST将会有非常好的科学产出. 望远镜一定能够在河外天文学与银河系天文学方面产生世界级的研究成果.”。

SDSS黑洞直径

年满18岁服兵役登记流程年满18岁的男性公民在中国是需要服兵役的，这是国家法律规定的义务。

本文将为大家介绍年满18岁服兵役的登记流程。

首先，需要了解的是，年满18岁的男性公民在何时开始登记服兵役。

根据《中华人民共和国兵役法》规定，男性公民在18周岁时即可开始登记兵役。

因此，一般情况下，登记兵役的时间是在18周岁生日之后。

接下来，我们来介绍具体的登记流程。

一、准备材料在进行兵役登记前，需要准备以下材料：1.身份证原件及复印件。

2.户口簿原件及复印件。

3.学历证书或学校开具的在读证明原件及复印件。

4.兵役登记表，可在当地兵役办公室领取或下载打印。

5.其他证明材料，如残疾证明、户口迁移证明等（根据个人情况而定）。

二、前往当地兵役办公室准备好以上材料后，前往当地兵役办公室进行登记。

兵役办公室一般设在县级以上行政区划的人民政府或军队驻地。

登记时需要携带身份证等证件原件进行核验。

三、填写兵役登记表在兵役办公室，填写兵役登记表，包括个人基本信息、家庭情况、学历情况等。

填写时需要认真核对，确保信息正确无误。

四、进行体检完成兵役登记表填写后，需要进行体检。

体检包括身体各项指标的检查，如视力、听力、身高、体重等。

体检结果将影响个人兵役的类型和服役时间。

五、接受面试体检完成后，需要接受面试。

面试内容主要包括政治思想、家庭情况、学历情况等方面的考察。

面试考核的结果将影响个人兵役的类型和服役时间。

六、领取兵役证完成体检和面试后，需要等待兵役办公室核实信息并发放兵役证。

兵役证是证明个人已完成兵役登记的重要证件，需要妥善保管。

以上就是年满18岁服兵役的登记流程。

需要注意的是，兵役登记是国家法律规定的义务，未完成兵役登记的男性公民将受到相应的处罚。

因此，年满18岁的男性公民应当积极履行兵役登记义务，为国家的安全和发展做出贡献。

二战后物理学最重要的实验有哪些？ - 知乎

提问搜索话题、问题或人...首页发现消息物理学科学史实验物理修改二战后物理学最重要的实验有哪些？修改对「最重要」的定义：这个我很纠结，本来想说二战后物理学实验中前十名重要的实验。

但我平生最讨厌「十大」，因为怎么那么巧是十个……修改添加评论分享 • 邀请回答举报4 个回答按票数排序著微，細推物理須行樂曾恒福、宋诗薇、邓雄杰等人赞同「重要」的标准见仁见智。

且学科的发展是一脉相承的，实际上很难说那一步「更」重要。

于是不妨多列举一些，并给出简要评介。

物理是实验科学，重大实验发现一般也意味着物理学本身的重大进展，所以写成了大事年表。

有些严格来说算是「发现」，不过发现和实验本来就无绝对界限；还有一些实际上是「发明」或者「技术」，但因意义重大，故一并列出。

————————————————————核磁共振（1946）Edward Purcell 和Felix Bloch 分别用共振吸收和核磁感应法测量核磁矩，实现了核磁共振。

二人因此获得1952年Nobel 物理学奖。

Lamb 位移（1947）由Willis Lamb 和Robert Retherford 发现。

Lamb 位移是量子电动力学的第一个实验证据。

其说明即便最简单的氢原子，量子力学也不能完整描述，而需要用量子电动力学。

Lamb 因此获得1955年Nobel 物理学奖。

电子反常磁矩（1947）反常磁矩包括电子和μ子的反常磁矩。

前者由Polykarp Kusch 精确测量，并因此获1955年Nobel 物理学奖。

反常磁矩同Lamb 位移一起，是量子电动力学的最重要的实验支柱。

π介子（1947）由Cecil Powell 等人在宇宙线中发现。

Powell 因此获得1950年Nobel 物理学奖。

而在1949年，汤川秀树则因为理论预测π介子存在获得Nobel 奖。

π介子是最轻也是最重要的介子，对研究低能268曾恒福话题20强相互作用有重要作用。

晶体管（1947）由Bell实验室的John Bardeen、Walter Brattain和William Shockley发明。

地球才是宇宙的中心？地心说被科学家证实「传统与新知系列」4

地球才是宇宙的中⼼？地⼼说被科学家证实「传统与新知系列」4每⼀个⼈，当他放眼浩瀚的苍穹之际，都曾经发出这样的追问：星空有多⼤？天空的边际有多远？我们脚下的地球在这个巨⼤的星空中处于怎样的位置？这⼀切⼜是如何形成的？古今中外的⼈对于这些问题有着不同阶段的认知。

从古⽼的“地⼼说”发展到哥⽩尼的“⽇⼼说”，历经⼀千多年的时间，⽽⽇⼼说也⼀度代表着科学对于中世纪宗教体系的挑战和冲击。

⽽最近的⼏⼗年⾥，随着哈勃望远镜等⼀批天⽂仪器和众多新的天⽂科学发现，科学家们从更洪⼤的宇宙视野观测中发现，地球⼜再⼀次回到宇宙的中⼼……张衡与托勒密的“地⼼说”⼫佼(前390年-前330年)⼫佼，战国时期著名的政治家、道家等思想家，先秦诸⼦百家之⼀。

⼫佼在《⼫⼦》⼀书中对宇宙概念明确写到“四⽅上下⽈宇,往古来今⽈宙.”意思是：宇表⽰东南西北上下六个⽅向,即表⽰空间.宙表⽰过去、现在和将来,即表⽰时间。

东汉著名天⽂学家张衡(78年-139年)东汉著名天⽂学家张衡在《浑天仪图注》⼀书中载有：“浑天如鸡⼦,天体圆如弹丸,地如鸡中黄,孤居于内,天⼤⽽地⼩,天表⾥有⽔,天之包地,犹壳之裹黄.”意思是整个天像⼀个鸡蛋，天圆像弹丸，地球像蛋黄，单独在最中⼼，天很⼤地很⼩，天以⽔包着地，，就像鸡蛋壳包着蛋清和最中⼼的蛋黄。

张衡的观点已经把地球看做整个宇宙中漂浮的实体，同时也是中国古⼈对“地⼼说”的⼀个形象表达。

⽽在古⽼的西⽅，地⼼说的起源很早，最初由⽶利都学派形成初步理念，后由古希腊学者欧多克斯提出，经亚⾥⼠多德完善，⼜由托勒密进⼀步发展成为托勒密'地⼼说'。

希腊晚期亚历⼭⼤城的数学家、天⽂学家托勒密(Claudius Ptolemy ，约90-168)所完成的西⽅的地⼼说体系，⼏乎与中国东汉的张衡同⼀时期。

托勒密体系的地⼼说在他所写的'天⽂⼤全'，后来⽤阿拉伯语简称为《⾄⼤论》(Almagest)⼀书的前⾔中，他明确提出:'……天宇是球形的并且作球体运动，⼤地就形状来说，显然是球状的……;就位置来说，它恰在天宇的中央，象⼏何中⼼⼀样，就⼤⼩和距离来说，[⼤地]与恒星⽐较就是⼀个点，它本⾝完全没有运动。

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二战后物理学最重要的实验有哪些？ - 知乎

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