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Timeline of knowledge about galaxies, clusters of galaxies, and large-scale structure
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Reionization
Matter-dominated
era
accelerated expansion
Unicellular life
photosynthesis
Multicellular
life
Vertebrates
Dark Ages
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Earliest universe (−13.80)
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Earliest stars
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Earliest galaxy
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Earliest quasar/sbh
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Omega Centauri forms
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Andromeda Galaxy forms
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Milky Way Galaxy
spiral arms form
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Alpha Centauri forms
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Solar System
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Earliest life
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Earliest oxygen
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Atmospheric oxygen
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Earliest sexual reproduction
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Earliest plants
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Cambrian explosion
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Earliest mammals
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Axis scale: billion years
Also see: Human timeline and Life timeline
Timeline of galaxies, clusters of galaxies, and large-scale structure of the universe
Contents
[hide]
1 Pre-20th century
2 Early 20th century
3 Mid-20th century
4 Late 20th century
5 Early 21st century
6 See also
7 References
Pre-20th century[edit]
5th century BC — Democritus proposes that the bright band in the night sky known as the Milky Way might consist of stars,
4th century BC — Aristotle believes the Milky Way to be caused by "the ignition of the fiery exhalation of some stars which were large, numerous and close together" and that the "ignition takes place in the upper part of the atmosphere, in the region of the world which is continuous with the heavenly motions",[1]
964 — Abd al-Rahman al-Sufi (Azophi), a Persian astronomer, makes the first recorded observations of the Andromeda Galaxy[2] and the Large Magellanic Cloud[3][4] in his Book of Fixed Stars, and which are the first galaxies other than the Milky Way to be observed from Earth,
11th century — Abū Rayḥān al-Bīrūnī, another Persian astronomer, describes the Milky Way galaxy as a collection of numerous nebulous stars,[5]
11th century — Alhazen (Ibn al-Haytham), an Arabian astronomer, refutes Aristotle's theory on the Milky Way by making the first attempt at observing and measuring the Milky Way's parallax,[6] and he thus "determined that because the Milky Way had no parallax, it was very remote from the Earth and did not belong to the atmosphere",[7]
12th century — Avempace (Ibn Bajjah) of Islamic Spain proposes the Milky Way to be made up of many stars but that it appears to be a continuous image due to the effect of refraction in the Earth's atmosphere,[1]
14th century — Ibn Qayyim Al-Jawziyya of Syria proposes the Milky Way galaxy to be "a myriad of tiny stars packed together in the sphere of the fixed stars" and that these stars are larger than planets,[8]
1521 — Ferdinand Magellan observes the Magellanic Clouds during his circumnavigating expedition,
1610 — Galileo Galilei uses a telescope to determine that the bright band on the sky, the "Milky Way", is composed of many faint stars
1750 — Thomas Wright discusses galaxies and the shape of the Milky Way,
1755 — Drawing on Wright's work, Immanuel Kant conjectures that the galaxy is a rotating disk of stars held together by gravity, and that the nebulae are separate such galaxies; he calls them Island Universes
1785 — William Herschel carried the first attempt to describe the shape of the Milky Way and the position of the Sun in it by carefully counting the number of stars in different regions of the sky. He produced a diagram of the shape of the galaxy with the solar system close to the center.
1845 — Lord Rosse discovers a nebula with a distinct spiral shape
Early 20th century[edit]
1918 — Harlow Shapley demonstrates that globular clusters are arranged in a spheroid or halo whose center is not the Earth, and hypothesizes, correctly, that its center is the Galactic Center of the galaxy,
26 April 1920 — Harlow Shapley and Heber Curtis debate whether or not the Andromeda Nebula is within the Milky Way,
1923 — Edwin Hubble resolves the Shapley–Curtis debate by finding Cepheids in the Andromeda Galaxy
1930 — Robert Trumpler uses open cluster observations to quantify the absorption of light by interstellar dust in the galactic plane; this absorption had plagued earlier models of the Milky Way,
1932 — Karl Guthe Jansky discovers radio noise from the center of the Milky Way,
1933 — Fritz Zwicky applies the virial theorem to the Coma Cluster and obtains evidence for unseen mass,
1936 — Edwin Hubble introduces the spiral, barred spiral, elliptical, and irregular galaxy classifications,
1939 — Grote Reber discovers the radio source Cygnus A,
1943 — Carl Keenan Seyfert identifies six spiral galaxies with unusually broad emission lines, named Seyfert galaxies,
1949 — J. G. Bolton, G. J. Stanley, and O. B. Slee identify NGC 4486 (M87) and NGC 5128 as extragalactic radio sources,
Mid-20th century[edit]
1953 — Gérard de Vaucouleurs discovers that the galaxies within approximately 200 million light-years of the Virgo Cluster are confined to a giant supercluster disk,
1954 — Walter Baade and Rudolph Minkowski identify the extragalactic optical counterpart of the radio source Cygnus A,
1959 — Hundreds of radio sources are detected by the Cambridge Interferometer which produces the 3C catalogue. Many of these are later found to be distant quasars and radio galaxies
1960 — Thomas Matthews determines the radio position of the 3C source 3C 48 to within 5",
1960 — Allan Sandage optically studies 3C 48 and observes an unusual blue quasistellar object,
1962 — Cyril Hazard, M. B. Mackey, and A. J. Shimmins use lunar occultations to determine a precise position for the quasar 3C 273 and deduce that it is a double source,
1962 — Olin Eggen, Donald Lynden-Bell, and Allan Sandage theorize galaxy formation by a single (relatively) rapid monolithic collapse, with the halo forming first, followed by the disk.
1963 — Maarten Schmidt identifies the redshifted Balmer lines from the quasar 3C 273
1973 — Jeremiah Ostriker and James Peebles discover that the amount of visible matter in the disks of typical spiral galaxies is not enough for Newtonian gravitation to keep the disks from flying apart or drastically changing shape,
1973 — Donald Gudehus finds that the diameters of the brightest cluster galaxies have increased due to merging, the diameters of the faintest cluster galaxies have decreased due to tidal distention, and that the Virgo cluster has a substantial peculiar velocity,
1974 — B. L. Fanaroff and J. M. Riley distinguish between edge-darkened (FR I) and edge-brightened (FR II) radio sources,
1976 — Sandra Faber and Robert Jackson discover the Faber-Jackson relation between the luminosity of an elliptical galaxy and the velocity dispersion in its center. In 1991 the relation is revised by Donald Gudehus,
1977 — R. Brent Tully and Richard Fisher publish the Tully–Fisher relation between the luminosity of an isolated spiral galaxy and the velocity of the flat part of its rotation curve,
1978 — Steve Gregory and Laird Thompson describe the Coma supercluster,
1978 — Donald Gudehus finds evidence that clusters of galaxies are moving at several hundred kilometers per second relative to the cosmic microwave background radiation,
1978 — Vera Rubin, Kent Ford, N. Thonnard, and Albert Bosma measure the rotation curves of several spiral galaxies and find significant deviations from what is predicted by the Newtonian gravitation of visible stars,
1978 — Leonard Searle and Robert Zinn theorize that galaxy formation occurs through the merger of smaller groups.
Late 20th century[edit]
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1981 — Robert Kirshner, August Oemler, Paul Schechter, and Stephen Shectman find evidence for a giant void in Boötes with a diameter of approximately 100 million light years,
1985 — Robert Antonucci and J. Miller discover that the Seyfert II galaxy NGC 1068 has broad lines which can only be seen in polarized reflected light,
1986 — Amos Yahil, David Walker, and Michael Rowan-Robinson find that the direction of the IRAS galaxy density dipole agrees with the direction of the cosmic microwave background temperature dipole,
1987 — David Burstein, Roger Davies, Alan Dressler, Sandra Faber, Donald Lynden-Bell, R. J. Terlevich, and Gary Wegner claim that a large group of galaxies within about 200 million light years of the Milky Way are moving together towards the "Great Attractor" in the direction of Hydra and Centaurus,
1987 — R. Brent Tully discovers the Pisces–Cetus Supercluster Complex, a structure one billion light years long and 150 million light years wide,
1989 — Margaret Geller and John Huchra discover the "Great Wall", a sheet of galaxies more than 500 million light years long and 200 million wide, but only 15 million light years thick,
1990 — Michael Rowan-Robinson and Tom Broadhurst discover that the IRAS galaxy IRAS F10214+4724 is the brightest known object in the Universe,
1991 — Donald Gudehus discovers a serious systematic bias in certain cluster galaxy data (surface brightness vs. radius parameter, and the D n {\displaystyle D_{n}} method) which affect galaxy distances and evolutionary history; he devises a new distance indicator, the reduced galaxian radius parameter, r g {\displaystyle r_{g}} , which is free of biases,
1992 — First detection of large-scale structure in the Cosmic microwave background indicating the seeds of the first clusters of galaxies in the early Universe
1995 — First detection of small-scale structure in the cosmic microwave background
1995 — Hubble Deep Field survey of galaxies in field 144 arc seconds across.
1998 — The 2dF Galaxy Redshift Survey maps the large-scale structure in a section of the Universe close to the Milky Way
1998 — Hubble Deep Field South
1998 — Discovery of accelerating universe
2000 — Data from several cosmic microwave background experiments give strong evidence that the Universe is "flat" (space is not curved, although space-time is), with important implications for the formation of large-scale structure
Early 21st century[edit]
2001 — First data release from the ongoing Sloan Digital Sky Survey
2004 — The European Southern Observatory discovers Abell 1835 IR1916, the most distant galaxy yet seen from Earth.
2004 — The Arcminute Microkelvin Imager begins to map the distribution of distant clusters of galaxies
2005 — Spitzer Space Telescope data confirm what had been considered likely since the early 1990s from radio telescope data, i.e., that the Milky Way Galaxy is a barred spiral galaxy.[9][10][11]
2012 — Astronomers report the discovery of the most distant dwarf galaxy yet found, approximately 10 billion light-years away.[12]
2012 — The Huge-LQG, a large quasar group, one of the largest known structures in the universe, is discovered.[13]
2013 — The galaxy Z8 GND 5296 is confirmed by spectroscopy to be one of the most distant galaxies found up to this time. Formed just 700 million years after the Big Bang, expansion of the universe has carried it to its current location, about 30 billion light years away from Earth.
2013 — The Hercules–Corona Borealis Great Wall, a massive galaxy filament and the largest known structure in the universe, was discovered through gamma-ray burst mapping.[14][15][16]
See also[edit]
Illustris project
Large-scale structure of the cosmos
References[edit]
^ Jump up to: a b Josep Puig Montada (September 28, 2007). "Ibn Bajja". Stanford Encyclopedia of Philosophy. Retrieved 2008-07-11.
Jump up ^ Kepple, George Robert; Glen W. Sanner (1998). The Night Sky Observer's Guide. 1. Willmann-Bell, Inc. p. 18. ISBN 0-943396-58-1.
Jump up ^ "Observatoire de Paris (Abd-al-Rahman Al Sufi)". Retrieved 2007-04-19.
Jump up ^ "Observatoire de Paris (LMC)". Retrieved 2007-04-19.
Jump up ^ O'Connor, John J.; Robertson, Edmund F., "Abu Rayhan Muhammad ibn Ahmad al-Biruni", MacTutor History of Mathematics archive, University of St Andrews .
Jump up ^ Mohamed, Mohaini (2000). Great Muslim Mathematicians. Penerbit UTM. pp. 49–50. ISBN 983-52-0157-9.
Jump up ^ Hamid-Eddine Bouali; Mourad Zghal; Zohra Ben Lakhdar (2005). "Popularisation of Optical Phenomena: Establishing the First Ibn Al-Haytham Workshop on Photography" (PDF). The Education and Training in Optics and Photonics Conference. Retrieved 2008-07-08.
Jump up ^ Livingston, John W. (1971). "Ibn Qayyim al-Jawziyyah: A Fourteenth Century Defense against Astrological Divination and Alchemical Transmutation". Journal of the American Oriental Society. American Oriental Society. 91 (1): 96–103 [99]. doi:10.2307/600445. JSTOR 600445.
Jump up ^ Britt, Robert Roy. "Milky Way’s Central Structure Seen with Fresh Clarity."
Jump up ^ SPACE.com 16 August 2005.
Jump up ^ Devitt, Terry "Galactic survey reveals a new look for the Milky Way." Archived 2006-02-09 at the Wayback Machine. 16 August 2005
Jump up ^ "Dark matter galaxy hints seen 10bn light-years away". BBC News. 2012-01-18.
Jump up ^ Wall, Mike (2013-01-11). "Largest structure in universe discovered". Fox News.
Jump up ^ Horvath I.; Hakkila J. & Bagoly Z. (2014). "Possible structure in the GRB sky distribution at redshift two". Astronomy & Astrophysics. 561: L12. arXiv:1401.0533  . Bibcode:2014A&A...561L..12H. doi:10.1051/0004-6361/201323020.
Jump up ^ Horvath I.; Hakkila J. & Bagoly Z. (2013). "The largest structure of the Universe, defined by Gamma-Ray Bursts". arXiv:1311.1104  . Bibcode:2013arXiv1311.1104H.
Jump up ^ Klotz, Irene (2013-11-19). "Universe's Largest Structure is a Cosmic Conundrum". discovery. Retrieved 2013-11-22.
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Galaxies
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Pipeline (Unix)
From Wikipedia, the free encyclopedia
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This article is about the original implementation for shells. For software pipelines in general, see Pipeline (software).
A pipeline of three programs run on a text terminal
In Unix-like computer operating systems, a pipeline is a sequence of processes chained together by their standard streams, so that the output of each process (stdout) feeds directly as input (stdin) to the next one.
The concept of pipelines was championed by Douglas McIlroy at Unix's ancestral home of Bell Labs, during the development of Unix, shaping its toolbox philosophy.[1][2] It is named by analogy to a physical pipeline.
The standard shell syntax for pipelines is to list multiple commands, separated by vertical bars ("pipes" in common Unix verbiage). For example, to list files in the current directory (ls), retain only the lines of ls output containing the string "key" (grep), and view the result in a scrolling page (less), a user types the following into the command line of a terminal:
 ls -l | grep key | less
"ls -l" produces a process, the output (stdout) of which is piped to the input (stdin) of the process for "grep key"; and likewise for the process for "less". Each process takes input from the previous process and produces output for the next process via standard streams. Each "|" tells the shell to connect the standard output of the command on the left to the standard input of the command on the right by an inter-process communication mechanism called an (anonymous) pipe, implemented in the operating system. Pipes are unidirectional; data flows through the pipeline from left to right.
 process1 | process2 | process3
Contents
[hide]
1 Pipelines in command line interfaces
1.1 Error stream
1.2 Pipemill
2 Creating pipelines programmatically
3 Implementation
3.1 Network pipes
4 History
4.1 Other operating systems
5 See also
6 References
7 External links
Pipelines in command line interfaces[edit]
All widely used Unix shells have a special syntax construct for the creation of pipelines. In all usage one writes the commands in sequence, separated by the ASCII vertical bar character "|" (which, for this reason, is often called "pipe character"). The shell starts the processes and arranges for the necessary connections between their standard streams (including some amount of buffer storage).
Error stream[edit]
By default, the standard error streams ("stderr") of the processes in a pipeline are not passed on through the pipe; instead, they are merged and directed to the console. However, many shells have additional syntax for changing this behavior. In the csh shell, for instance, using "|&" instead of "|" signifies that the standard error stream should also be merged with the standard output and fed to the next process. The Bourne Shell can also merge standard error with |& since bash 4.0[3] or using 2>&1, as well as redirect it to a different file.
Pipemill[edit]
In the most commonly used simple pipelines the shell connects a series of sub-processes via pipes, and executes external commands within each sub-process. Thus the shell itself is doing no direct processing of the data flowing through the pipeline.
However, it's possible for the shell to perform processing directly, using a so-called mill, or pipemill, (since a while command is used to "mill" over the results from the initial command). This construct generally looks something like:
command | while read var1 var2 ...; do # process each line, using variables as parsed into $var1, $var2, etc # (note that this may be a subshell: var1, var2 etc will not be available # after the while loop terminates; some shells, such as zsh and newer # versions of Korn shell, process the commands to the left of the pipe # operator in a subshell) done
Such pipemill may not perform as intended if the body of the loop includes commands, such as cat and ssh, that read from stdin:[4] on the loop's first iteration, such a program (let's call it the drain) will read the remaining output from command, and the loop will then terminate (with results depending on the specifics of the drain). There are a couple of possible ways to avoid this behavior. First, some drains support an option to disable reading from stdin (e.g. ssh -n). Alternatively, if the drain does not need to read any input from stdin to do something useful, it can be given < /dev/null as input.
Creating pipelines programmatically[edit]
Pipelines can be created under program control. The Unix pipe() system call asks the operating system to construct a new anonymous pipe object. This results in two new, opened file descriptors in the process: the read-only end of the pipe, and the write-only end. The pipe ends appear to be normal, anonymous file descriptors, except that they have no ability to seek.
To avoid deadlock and exploit parallelism, the Unix process with one or more new pipes will then, generally, call fork() to create new processes. Each process will then close the end(s) of the pipe that it will not be using before producing or consuming any data. Alternatively, a process might create a new thread and use the pipe to communicate between them.
Named pipes may also be created using mkfifo() or mknod() and then presented as the input or output file to programs as they are invoked. They allow multi-path pipes to be created, and are especially effective when combined with standard error redirection, or with tee.
Implementation[edit]
In most Unix-like systems, all processes of a pipeline are started at the same time, with their streams appropriately connected, and managed by the scheduler together with all other processes running on the machine. An important aspect of this, setting Unix pipes apart from other pipe implementations, is the concept of buffering: for example a sending program may produce 5000 bytes per second, and a receiving program may only be able to accept 100 bytes per second, but no data is lost. Instead, the output of the sending program is held in the buffer. When the receiving program is ready to read data, then next program in the pipeline reads from the buffer. In Linux, the size of the buffer is 65536 bytes (64KB). An open source third-party filter called bfr is available to provide larger buffers if required.
Network pipes[edit]
Tools like netcat and socat can connect pipes to TCP/IP sockets.
History[edit]
The pipeline concept was invented by Douglas McIlroy and first described in the man pages of Version 3 Unix.[5] McIlroy noticed that much of the time command shells passed the output file from one program as input to another.
His ideas were implemented in 1973 when ("in one feverish night", wrote McIlroy) Ken Thompson added the pipe() system call and pipes to the shell and several utilities in Version 3 Unix. "The next day", McIlroy continued, "saw an unforgettable orgy of one-liners as everybody joined in the excitement of plumbing." McIlroy also credits Thompson with the | notation, which greatly simplified the description of pipe syntax in Version 4.[6][5] The idea was eventually ported to other operating systems, such as DOS, OS/2, Microsoft Windows, and BeOS, often with the same notation.
Although developed independently, Unix pipes are related to, and were preceded by, the 'communication files' developed by Ken Lochner [7] in the 1960s for the Dartmouth Time Sharing System.[8]
In Tony Hoare's communicating sequential processes (CSP) McIlroy's pipes are further developed.[9]
The robot in the icon for Apple's Automator, which also uses a pipeline concept to chain repetitive commands together, holds a pipe in homage to the original Unix concept.
Other operating systems[edit]
Main article: Pipeline (software)
This feature of Unix was borrowed by other operating systems, such as Taos and MS-DOS, and eventually became the pipes and filters design pattern of software engineering.
See also[edit]
Everything is a file – describes one of the defining features of Unix; pipelines act on "files" in the Unix sense
Anonymous pipe – a FIFO structure used for interprocess communication
GStreamer – a pipeline-based multimedia framework
CMS Pipelines
Iteratee
Named pipe – persistent pipes used for interprocess communication
GNU parallel
Pipeline (computing) – other computer-related pipelines
Redirection (computing)
Tee (command) – a general command for tapping data from a pipeline
XML pipeline – for processing of XML files
xargs
References[edit]
Jump up ^ Mahoney, Michael S. "The Unix Oral History Project: Release.0, The Beginning". McIlroy: It was one of the only places where I very nearly exerted managerial control over Unix, was pushing for those things, yes.
Jump up ^ http://cm.bell-labs.com/cm/cs/who/dmr/mdmpipe.html
Jump up ^ "Bash release notes". tiswww.case.edu. Retrieved 2017-06-14.
Jump up ^ http://web.archive.org/web/20120306135439/http://72.14.189.113/howto/shell/while-ssh/
^ Jump up to: a b McIlroy, M. D. (1987). A Research Unix reader: annotated excerpts from the Programmer's Manual, 1971–1986 (PDF) (Technical report). CSTR. Bell Labs. 139.
Jump up ^ http://www.linfo.org/pipe.html Pipes: A Brief Introduction by The Linux Information Project (LINFO)
Jump up ^ http://www.cs.rit.edu/~swm/history/DTSS.doc
Jump up ^ http://cm.bell-labs.com/who/dmr/hist.html
Jump up ^ https://swtch.com/~rsc/thread/ Bell Labs and CSP Threads (Russ Cox)
Sal Soghoian on MacBreak Episode 3 "Enter the Automatrix"
External links[edit]
History of Unix pipe notation
Doug McIlroy’s original 1964 memo, proposing the concept of a pipe for the first time
pipe: create an interprocess channel – System Interfaces Reference, The Single UNIX Specification, Issue 7 from The Open Group
Pipes: A Brief Introduction by The Linux Information Project (LINFO)
Unix Pipes – powerful and elegant programming paradigm (Softpanorama)
Ad Hoc Data Analysis From The Unix Command Line at Wikibooks – Shows how to use pipelines composed of simple filters to do complex data analysis.
Use And Abuse Of Pipes With Audio Data – Gives an introduction to using and abusing pipes with netcat, nettee and fifos to play audio across a network.
stackoverflow.com – A Q&A about bash pipeline handling.
Retrieved from "https://en.wikipedia.org/w/index.php?title=Pipeline_(Unix)&oldid=802973746"
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