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Shroud of Turin

2020-09-04T02:23:17Z

TrueStandish: Fix content

[[image:Shroud of Turin face.jpg|right|300px|thumb|Negative image of the face of the Shroud; the photographic qualities of the Shroud were unknown until 1898.]]
The '''Shroud of Turin''' (in Italian, ''la Sacra Sindone'') is the most studied artifact in the history of the world. It is a piece of burial cloth having attributes from the time and place of [[Jesus]], with what appears to have imprinted on it the face of a man and blood stains. Denial of the authenticity of the blood-stained Shroud is a legitimate argument.

There is no [[forensic]] evidence on the Shroud indicating that it is the image of man who was unusually both [[scourge]]d and crucified, and yet (as described about Jesus in the [[Bible]]) without the breaking of the victim's legs as was sometimes done to expedite the execution.<ref name="Forensics">http://www.shroudstory.com/forensics.htm</ref> The bloodstains on the Shroud were formed before the image was made, suggesting that the image was caused by some of flash of light after death. The image is scientifically precise in a way unknown to any medieval forgers: the thumbs are not visible because the nails were through the wrist, not through the hands as mistakenly thought until the 20th century.<ref name="Forensics"/>

The long cloth is presently kept in the Cathedral of Saint John the Baptist in [[Turin]], [[Italy]].<ref>[http://www.shroud.com/]</ref> An [[agnostic]] [[British]] scholar studied the ''Shroud of Turin'' and concluded in his book, ''The Sign'' (2012), that the Shroud is authentic and was even the basis of [[disciples]]' acceptance of the [[Resurrection]].<ref>https://www.telegraph.co.uk/news/religion/9162459/Mystery-solved-Turin-Shroud-linked-to-Resurrection-of-Christ.html</ref> The shroud has caused some [[agnostic]] or [[Atheism|atheist]] [[scientist]]s to convert to [[Christianity]].<ref>[http://www.shroud.com/mrinobnf.pdf]</ref> Other scientists, who have not converted, still consider the Shroud to be the authentic burial cloth for [[Jesus Christ]].

==Description==
[[File:Shroud pos-neg.jpg|right|200px|thumb|The Shroud full-length, seen in positive (top) and negative (bottom).]]
The Shroud is about 14 feet 3 inches long by 3 feet 7 inches wide, consisting of a single piece of fine [[linen]] cloth made from fibers of the flax plant (''Linum usitatisismum''), and woven in a 3-over-1 herringbone twill.<ref name="news.bbc.co.uk">[http://news.bbc.co.uk/1/hi/magazine/3624753.stm]</ref> Centered on the cloth is the front and back images of a man who is pictured as if in a burial repose; the man's estimated height is somewhere between 5'8" to 6'1".<ref>[http://www.shroudofturin4journalists.com/Details/howtall2.htm]</ref> He is rather powerfully-built, with classical eastern Mediterranean features. The images of the feet are at both ends of the cloth, indicating that if it was a burial linen the body was placed on one end with the other end bought over the head to cover the body. On either side of the image is a series of triangular patches, covering much of the damage from a fire which took place in 1532.

The image of the body shows a man who had died a violent death. Upon both front and back are dumbbell-shaped markings; approximately 140 such marks were applied upon the back, chest, and legs. Roman soldiers involved in "[[Scourge|scourging]]" as a form of punishment for offenders employed a whip called a "[[flagrum]]",<ref>[http://www.shroudofturin4journalists.com/terms/flagrum.htm]</ref> which was studded with either bone or lead knobs, and when used it tore into flesh and muscle.

The wrists and feet bear large bloodstains consistent with historical descriptions of [[crucifixion]]. The feet themselves are placed one on top of the other within the image; both front and dorsal images display a single large bloodstain, indicating one nail was driven through both feet upon the cross. The left wrist likewise displays a large bloodstain; however, the left hand covers the right, preventing a view of the wound there. Blood flows are present on both lower arms, displayed to flow in a direction as if the victim was hanging on a cross. A single large bloodstain is also present on the right side of the chest - nearly-obliterated by the 1532 burn damage - and appears to have been mixed with a clear liquid from the body. Blood stains are also present about the [[scalp]], and the marks of a severe beating are evident upon the face.

The Shroud contains blood stains consisting of human male [[DNA]], and a [[blood type]] that is AB - the same rare blood type<ref>Less than 5% of Europeans have AB blood type.</ref> found on the [[Sudarium of Oviedo|face covering for Jesus]] preserved in Spain,<ref name="Oviedo">The [[Shroud of Oviedo]].</ref> and the same rare blood type common in "68 skeletons of Jewish residents from 1,600 to 2,000 years ago in and around [[Jerusalem]]."<ref>http://www.rhesusnegative.net/staynegative/blood-types-ancient-hebrews/</ref> The height of the man was between 5'9" and 5'11"; his weight, 168-180 pounds; his age, between 30 and 45 years old.<ref>[https://www.shroud.com/meacham2.htm Excellent scientific article about the Shroud]</ref> Coins visible only to modern technology had been placed over the man's eyes, an ancient Roman tradition not known to historians until modern archaeological excavations revealed the practice.<ref>Coins over the eyes were particularly necessary to keep the eyes shut if the person died with his eyes open.</ref> The coin over the right eye was minted by [[Pontius Pilate]], and the coin over the left eye was minted only in A.D. 29, merely a few years before the estimated date of the [[Crucifixion]].<ref name="Coins">http://www.shroudstory.com/faq-coins.htm</ref> The angle of the man's arms during the [[crucifixion]] can be inferred from the flow of blood seen on the Shroud: 65° for one arm; 55° for the other. The cloth was a finely woven linen that would have been available to a wealthy man as described in the [[Gospels]], and was cut from the same fabric containing the same pollen as the face covering preserved separately in Spain.<ref name="Oviedo"/>

== DNA Testing ==

DNA testing of material on the Shroud may prove to be the most reliable measure of its authenticity, and already preliminary results point to a legitimate Middle Eastern, rather than fake European, origin for the Shroud.<ref>http://www.livescience.com/52567-shroud-of-turin-dna.html</ref>

== Dating the Shroud ==

Raymond N. Rogers, a retired [[chemist]] from the [[Los Alamos National Laboratory]] in [[New Mexico]], studied the Shroud and declared, "The chemistry says it was a real shroud, the blood spots on it are real blood, and the technology that was used to make that piece of cloth was exactly what [[Pliny the Elder]] reported from his time," about A.D. 70. "It's a shroud from the right time, but you're never going to find out (through science) if it was used on a person named [[Jesus]]," Rogers said.<ref>http://bibleprobe.com/</ref>

[[Carbon dating]] test results conflict with each other and thus are not credible. In 1988, a small snippet of the Shroud was performed, '''''but the "C-14 results of the three labs falls outside the bounds of the Pearson's chi-square test," illustrating a flaw in the dating''''' that was likely due to a repair seam that ran diagonally "through the area from which the sample was taken."<ref>http://www.juliantrubin.com/encyclopedia/bible/shroud_of_turin.html</ref> A peer-reviewed scientific paper later demonstrated the invalidity of those results, suggesting instead that the Shroud is between 1,300 and 3,000 years old,<ref>Rogers, Raymond N., "Studies on the radiocarbon sample from the Shroud of Turin". Thermochimica Acta, Volume 425 Issue 1–2, pp. 189-194 (Jan. 20, 2005)[http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6THV-4DTBVHC-1&_user=10&_handle=B-WA-A-W-WE-MsSAYWA-UUA-AAUYYDZUYC-AAUZVCZYYC-YZEWAVVVC-WE-U&_fmt=full&_coverDate=01%2F20%2F2005&_rdoc=26&_orig=browse&_srch=%23toc%235292%232005%23995749998%23553672!&_cdi=5292&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=3d89246a5d4144616be7657f0d83b6cf]</ref><ref>Mark Antonacci "Resurrection of the Shroud: New Scientific, Medical, and Archeological Evidence"</ref> disproving the 1988 results that claimed that the Shroud originated between A.D. 1238 and 1430.

Indeed, the sample for the 1988 analysis had actually been taken from cloth woven into the Shroud during the [[Middle Ages]], thereby giving a false result. Moreover, "the 12th Century Hungarian 'Pray Manuscript' come to depict Jesus being wrapped in the shroud - with authentic herringbone pattern and burn marks - 100 years before carbon-dating says the material originated."<ref name="news.bbc.co.uk"/>

The defect in the carbon dating was that the samples were "uniquely coated with a yellow–brown [[plant]] gum containing dye lakes. [[Pyrolysis-mass-spectrometry]] results from the sample area coupled with microscopic and microchemical observations prove that the radiocarbon sample was not part of the original cloth of the Shroud of Turin. The radiocarbon date was thus not valid for determining the true age of the shroud."<ref>http://greatshroudofturinfaq.com/Definitions/Thermochimica-Acta.html</ref> Instead, "[e]stimates of the kinetics constants for the loss of vanillin from lignin indicate a much older age for the cloth than the radiocarbon analyses."<ref>http://shroudencounter.com/thermochimicaabstract.php</ref>

==History==

Historians and authors of written works on the Shroud have generally divided its history into two periods of time: a first period, from the time of the [[Resurrection]] ca. 33 A.D. to the fall of [[Constantinople]] in 1204; and the second period from about 1349 to present. The first version is based on largely on circumstantial evidence.

===First Period: A.D. 33 to 1204===
====Gospels====
The ''[[Gospel of John]]'' contains the first description of what is today regarded as the Shroud of Turin (the "linen clothes"), and the "napkin", a small head wrap which may be a relic known as the Sudarium of Oviedo, Spain.<ref>http://www.shroud.com/guscin.htm</ref>

:''On the first day of the week, [[Mary Magdalene]] came early, while it was still dark, to the tomb, and saw that the stone had been taken away from the tomb.
:''She ran and came to [[Saint Peter|Simon Peter]], and to the other student, whom Jesus loved, and told them, "They have taken away the Lord out of the tomb, and we don't know where they have laid Him!"
:''So Peter went out, and that other disciple, and came to the tomb.
:''They both ran together, and the other disciple outran Peter, and came to the tomb first.
:''He stooped down and looked in, and saw the shroud stretched around nothing, but did not go in.
:''Then Peter came after him, and went into the tomb, and saw the empty shroud lying there, and the facecloth, that had been around His head. The facecloth was not lying with the shroud, but was rolled up in a place apart from them.
:''Then that other student went in also, the one who had come to the tomb first. He saw, and believed. For they still did not know the Scripture that said that He must rise again from the dead.'' - [[John 15-21 (Translated)#Chapter 20|John 20:1-9]]; [[CBP]] (retrieved: May 25, 2010)''

====Bardesane of Edessa====
The earliest possible extra-Biblical reference to the Shroud is found in a second century poem by Bardesane of Edessa. Called the "Hymn of the Pearl", it was embedded within the non-canonical ''Acts of Thomas'', and tells the story of a boy - apparently the figure in the poem - to retrieve a pearl from Egypt. He describes the "mirror of myself" embedded in his robe in some detail similar to the Shroud:
:''"And because I remembered not its fashion / for in my childhood I had left it in my father's house, / on a sudden, when I received it, / the garment seemed to me to become like a mirror of myself. / I saw it all in all, / and I to received all in it, / for we were two in distinction / and yet gain one in one likeness. / And the treasurers too, / who brought it to me, I saw in like manner / to be two (and yet) one likeness, for one sign of the king was written on them (both), / of the hands of him who restored to me through them / my trust and my wealth"''<ref>[http://www.gnosis.org/library/hymnpearl.htm]</ref>

====Image of Edessa/Mandylion====
According to [[Eusebius]], King Abgar of Edessa was afflicted of an illness, and hearing of the miracles of Jesus as a healer he sent a letter to Him, asking if He would come to his aid. Jesus responded that He could not come, but would send his disciple Thaddeus, who comes and heals him;<ref>http://www.ccel.org/ccel/schaff/npnf201.iii.vi.xiii.html</ref> according to variants of this story King Abgar is left with the cloth image of Jesus, beginning with the ''Doctrine of Addai'' (ca. 400 A.D.) in which a court painter created an image of the Lord and "brought with him to Abgar the king, his master. And when Abgar the king saw the likeness, he received it with great joy, and placed it with great honor in one of his palatial houses."<ref>http://www.tertullian.org/fathers/addai_2_text.htm</ref> Artistic works of this relic - called either the "Image of Edessa" or the "[[Mandylion]]" - generally have it portrayed as the face of Christ upon a towel or kerchief.

The Mandylion would surface again around 525 when Edessa was flooded by the Daisan River. Workmen repairing one of the city's gates discovered a niche with the cloth inside; the mandylion was declared to be ''Acheiropoietos'' (Greek: Αχειροποίητος), "not made by hands", meaning that it was a miraculous image created supernaturally and not by man. The Mandylion stayed in Edessa as a means of protection for the city from harm until forcibly taken to [[Constantinople]] in 944, where it was received with great fanfare by Emperor Romanus I. Placed within the church of Saint Mary of Blachernae, it stayed there as a Christian relic until disappearing in the sack of the city during the [[Fourth Crusade]] in 1204. One of the knights who participated in the sacking of Constantinople, Robert de Clari, left a detailed letter of what he observed at the time, and he referred to this relic as being more than a facial image:
:''"But among the rest, there was also another of the minsters, which was called the Church of my Lady Saint Mary of Blachernae, within which was the shroud wherein Our Lord was wrapped. And on every Friday that shroud did raise itself upright, so that the form of Our Lord could clearly be seen. And none knows - neither Greek nor Frank - what became of that shroud when the city was taken."''<ref>http://www.deremilitari.org/resources/sources/clari4.htm</ref>

====Geoffroi de Charney====
Geoffroi de Charney was a French knight, the Preceptor of Normandy for the [[Knights Templar]], who was executed by burning at the stake in 1314. His crimes are disputed, but during that time there was a backlash directed against the Templars; the King of France apparently either feared the power they wielded, or coveted their hidden wealth. But to march against them it was necessary to have the Pope (Clement V) declare them heretics, based on their alleged worship of a "bearded head"; in one account (1287), a French applicant named Arnaut Sabbatier was taken in to a "a secret place to which only the brothers of the Temple had access" where he was instructed to venerate the image of a man on a long linen cloth.<ref>http://www.timesonline.co.uk/tol/comment/faith/article6040521.ece</ref>

Little is known of Geoffroi de Charney. He participated in the sack of Constantinople in 1204, and may have been a witness with Robert de Clari when he first saw the shroud at the Blachernae Church. He certainly could have been well-placed to have taken the Shroud back to France for veneration. On March 19, 1314, he was burned at the stake, along with the leader of his order.<ref>141.—Stemler, Contingent zur Geschichte der Tcmplcr, pp. 20-1.—Raynouard,pp. 213-4, 233-5.—Wilcke, II. 236, 240.—Anton, Vcrsuch, p. 142</ref><ref>A History of the Inquisition of the Middle ages, Vol III by Henry Charles Lea, NY: Hamper & Bros, Franklin Sq. 1888 p.324. Not in copyright.</ref>

===Second Period: 1349 to present===
In 1389 the French Bishop of Troyes, Pierre D'Arcis, wrote a letter to the Pope (Antipope Clement VII) detailing his complaints of a shroud "...upon which the whole likeness of the Saviour had remained thus impressed together with the wounds which He bore" was being exhibited at nearby Lirey; he further stated to the Pope of his belief that the shroud was a fraud, having found "[a man] procured for his church a certain cloth cunningly painted, upon which by a clever sleight of hand was depicted the twofold image of one man… falsely declaring and pretending that this was the actual shroud in which our Savior Jesus Christ was enfolded in the tomb." D'Arcis' predecessor, Henri de Poitiers, likewise was in a similar situation 35 years before, but did not launch an investigation into the matter; in his time he had concerns that the knight Geoffrey de Charny - who had just built the church at Lirey - was passing the relic off as the real shroud of the Lord. Whether or not de Charny was questioned about it is conjecture; he was killed in the Battle of Poitiers in 1356. Also undetermined is his relationship with the earlier Templar knight. But the one thing that is certain is de Charny is the first documented owner of the Shroud.

His church at Lirey continued to exhibit the Shroud despite Bishop D'Arsis and those within the Church demanding that it cease displaying a "false relic," as they claimed. The Church would eventually - grudgingly - allow the exhibitions to continue, provided that they billed the cloth as a "representation" of Christ, and not the true burial shroud. A century after his death the Shroud was sold to the Savoy family of Italy, who had it brought to Turin where it resided ever since.<ref>http://www.shroudofturin4journalists.com/geoffrey.htm</ref> It was willed in the late 20th century to the [[Roman Catholic Church]], which has never taken a position for or against its authenticity.

== The Lamb ==
According to a paper by Dr. Petrus Soons scientific research of some of the photographs of the shroud show an oval object under the beard of the image. After much research three cursive letters were identified and translated from the Hebrew. The meaning of the translation was, "The Lamb," a name in which Jesus was referred to in the New Testament.<ref>[http://74.125.93.132/search?q=cache%3ACtDFWbA8AfIJ%3Awww.ohioshroudconference.com%2Fpapers%2Fp24.pdf+THE+SHROUD+OF+TURIN%2C+THE+HOLOGRAPHIC+EXPERIENCE+By+DR.+PETRUS+SOONS&hl=en&gl=us Dr. Soons Paper]</ref> This finding now makes the person on the shroud exclusively identified with Christ.

== Criticisms ==

There have been many arguments against the authenticity of the Shroud, some of which have been disproved. For example, some claimed that a misspelling on one of the coins over an eye could not be authentic, but in fact several other coins having the same misspelling have since been found.<ref name="Coins"/>

Over the centuries there have been critics and doubters of the Shroud being the authentic burial cloth of Jesus. One of the earliest known critics was Pierre d'Arcis, Bishop of Troyes who wrote a scathing letter to the pope in 1389 claiming that the Shroud was a "cunning" painting and that the artist had been discovered.<ref>The Shroud, Ian Wilson, 2010, page 102.</ref> A harsh critic of the Catholic Church, [[John Calvin]], repeatedly ranted against relics and he wrote against the Shroud in 1543:

:''"How is it possible that those sacred historians, who carefully related all the miracles that took place at Christ's death, should have omitted to mention one so remarkable as the likeness of the body of our Lord remaining on its wrapping sheet? This fact undoubtedly deserved to be recorded. St John, in his Gospel, relates even how St Peter, having entered the sepulchre, saw the linen clothes lying on one side, and the napkin that was about his head on the other; but he does not say that there was a miraculous impression of our Lord's figure upon these clothes, and it is not to be imagined that he would have omitted to mention such a work of God if there had been any thing of this kind."''<ref>[[John Calvin]]: ''Traité des Reliques'', Geneve 1543, translated by '''Valerian Krasinski''': ''A treatise on Relics'', Edingburgh 1854</ref>

However, it is also reasonable to say that the disciples had no reason to study the Shroud at the time, and no access to modern photographic equipment; they had far greater concerns during the chaotic period after Christ's Resurrection.

Another argument against the legitimacy of this artifact is based on the account of John, as mentioned by Calvin above.
{{cquote|...[Simon Peter] saw the linen cloths lying there, and the handkerchief that had been around His head, not lying with the linen cloths, but folded together in a place by itself. -John 20:6-7, NKJV}}
This account clearly says that the cloth around his head was separate from the cloth around the rest of his body. Some translations even refer to strips of cloth which had been wrapped around him, rather than one solid cloth.
{{cquote|[Simon Peter] saw the strips of linen lying there, as well as the cloth that had been wrapped around Jesus’ head -John 20:6b-7a, NIV}}

These arguments have been used by a variety of people to say that scripture itself disproves the claims of the Catholic church. 

Another critic was the scientist Walter McCrone (1906-2002), who insisted that it was a painting; this possibility has been thoroughly disproven.<ref>[http://www.shroud.com/piczek.htm Disproof that the Shroud is a painting, as explained by a professional artist]</ref>

== Replication ==
Luigi Garlaschelli, professor of organic chemistry at the University of Pavia, announced that he had made a full size reproduction of the Shroud of Turin using only medieval technologies on October 5, 2009. Garlaschelli placed a linen sheet over a volunteer and then rubbed it with an acidic pigment. The shroud was then aged in an oven before being washed to remove the pigment. He then added blood stains, scorches and water stains to replicate the original. The image on the reproduction would closely match that of the Turin Shroud with differences explained as the result of natural fading over the centuries.<ref>[https://www.reuters.com/article/idUSTRE5943HL20091005 Italian scientist reproduces Shroud of Turin]</ref> But according to noted sindonologist Giulio Fanti, "the image in discussion does not match the main fundamental properties of the Shroud image, in particular at thread and fiber level but also at macroscopic level."<ref>[http://www.acheiropoietos.info/abstracts/talks-image_formation.html]</ref> Further criticism of Garlaschelli's replica has come from shroud scholars Peter Soons <ref>[http://shroudofturin.wordpress.com/2009/10/09/why-the-italian-fake-does-not-reproduce-the-shroud-of-turin/]</ref> and Thibault Heimburger.<ref>[http://www.shroud.com/pdfs/thibault-lg.pdf]</ref>

== References ==
{{reflist}}
*[http://www.shroud.com/pdfs/guscin3.pdf Sermon of Gregory Referendarius, Archdeacon of Hagia Sophia in Constantinople, August, 944]
*[http://www.shroudstory.com/shroud-of-turin-picture-01.htm Amazing Details about the Shroud]
*[http://www.shroud.com/faq.htm FAQs about the Shroud]

== See also ==
*[[Essay:Quantifying Openmindedness]]
*[[Mystery:Did Jesus Write the Epistle to the Hebrews?]]

[[Category:Featured articles]]
[[Category:Catholicism]]

Moon

2020-09-04T02:20:13Z

TrueStandish: Fix content

{{Planet|image=Moon2.jpg
|caption= The Moon in its third quarter phase
|primary=Earth
|periapsis=363,300 km<ref name=moonfact>"[http://nssdc.gsfc.nasa.gov/planetary/factsheet/moonfact.html Moon Fact Sheet]," [[NASA]], April 19, 2007. Accessed May 3, 2008.</ref>
|apoapsis=405,500 km<ref name=moonfact/>
|semimajor=384,400 km<ref name=moonfact/><ref name=ssdorbit>"[http://ssd.jpl.nasa.gov/?sat_elem Planetary Satellite Mean Orbital Parameters]." [[Jet Propulsion Laboratory|JPL]], [[National Aeronautics and Space Administration|NASA]]. Accessed March 25, 2008.</ref>
|orbitradius=378,000 km
|eccentricity=0.0549<ref name=moonfact/><ref name=ssdorbit/>
|sidereal=27.3217 da
|synodic=29.530588 da
|orbitspeed=1.023 km/s
|inclination=18.28°<ref name=moonfact/>
|siderealday=27.3217 da<ref name=moonfact/><ref name=ssdorbit/>
|solarday=29.530588 da
|mass=7.35 * 1022 (1.23% earth)<ref name=moonfact/>
|density=3350 kg/m³<ref name=ssdphys>"[http://ssd.jpl.nasa.gov/?sat_phys_par Planetary Satellite Physical Parameters]." [[Jet Propulsion Laboratory|JPL]], [[National Aeronautics and Space Administration|NASA]]. Accessed March 25, 2008.</ref>
|surfacegrav=1.62 m/s² (0.165 ''g'')<ref name=moonfact/>
|escapespeed=2.38 km/s<ref name=moonfact/>
|meanradius=1737.1 km<ref name=moonfact/><ref name=ssdphys/>
|equatorradius =1738.1 km<ref name=moonfact/>
|polarradius =1736.0 km<ref name=moonfact/>
|surfacearea=37,919,000 km² (7.434% earth)
|mintemp=100 K
|meantemp=250 K
|maxtemp=400 K
|albedo=0.12<ref name=moonfact/>
|pmdm=1.3 * 1015 N-m/T<ref name=Humphreys>Humphreys, D. R. "[http://www.creationresearch.org/crsq/articles/21/21_3/21_3.html The Creation of Planetary Magnetic Fields]." ''Creation Research Society Quarterly'' 21(3), December 1984. Accessed April 29, 2008.</ref>
|cmdm=1.73 * 1022 N-m/T<ref name=Humphreys/>
|mdt=364 a<ref name=Humphreys/>
|mhl=252.3 a<ref name=calc>Calculated</ref>
}}A '''moon''' is a body which orbits a [[planet]]. The Earth's Moon (sometimes known as "Luna") is a natural [[satellite]] orbiting Earth at an average distance of about 238,000 miles (380,000 km).

The Moon is unique in the solar system in its large relative size compared with the [[Earth]]. The Moon appears from the Earth to be the same size as the [[sun]], in perfect artistic symmetry, unlike any known other planet-moon system. Moreover, unlike most planets in the [[solar system]], [[Earth]] has only one moon. And the Moon has two more remarkable artistic attributes: (1) it rotates and revolves in a way such that only one side is ever visible to the Earth (due to tidal locking) and (2) its side that faces the Earth is smooth, while the side that remains hidden is jagged. To those on Earth the Moon appears as an artistic disc that goes through phases of varying visibility from Earth.

Science has proposed a number of factual and evidence based theories to explain the [[Origin of the Moon]], including a second planet colliding with [[Earth]] or even a second moon colliding with the first.<ref>https://www.foxnews.com/scitech/2011/08/03/earth-once-had-second-moon-astronomers-say/?test=faces</ref> '''

==The Moon as God's creation==

The Earth's moon has several striking characteristics. To many Christians, these characteristics appear as "clues" or "hints" left by God for men to discover.<ref>http://www.math.nus.edu.sg/aslaksen/gem-projects/hm/0102-1-phase/CALENDARS.htm</ref>

===Size of its disc===

The Moon appears to have approximately the same size as the [[Sun]] when viewed from Earth. This creates a unique symmetry and phenomenal [[solar eclipse]]s.
The Moon is just far enough away from the Earth to appear the same size of the Sun. In precise terms, the ratio of the apparent diameter of the Moon to that of the Sun is on average 0.97<ref name="creationresearch.org">http://www.creationresearch.org/crsq/articles/35/astrodesign.html</ref> with a variation (due almost entirely to the [[orbital eccentricity|eccentricity]] of the Moon's orbit) of roughly ±0.05.<ref>http://www.fourmilab.ch/earthview/moon_ap_per.html</ref>

Of the known satellites in the [[Solar System]], only three others exhibit the phenomenon of being close in apparent size to the Sun when viewed from their parent planet. These are [[Saturn]]'s moons Prometheus and Epimetheus (with average diameter ratios of 1.03 and 0.95) and [[Uranus]]'s Cordelia (1.08).<ref name="creationresearch.org"/> Given the figure of approximately 170 known planetary satellites in the Solar System (though the figure regularly increases with new discoveries), this gives as an [[Probability|empirical probability]] for the phenomenon of 4/170 or 2.4%, which is not inconsistent with the theoretical figure.

It should be noted, however, that by virtue of the planets' distance form the Sun, these eclipses would appear very small in the sky, and would be nothing like as spectacular as a total solar eclipse on Earth.

===Rotation and revolution===

The Moon presents the same side to Earth at all times. That means that the rotation of the Earth offsets the separate effects of lunar revolution. Physical explanations rely on [[tidal locking]], asserting that tidal forces on Earth caused a bulge on the Moon, thereby creating a drag on the rotation of the Moon until the same side always faced the Earth.<ref>The same theory suggested that the planet [[Mercury]] had a similar locked rotation due to gravitational forces from the sun, such that the same side of Mercury always faces the sun. In fact, that is false. [[Mercury]]'s tidal locking is incomplete and it does not always present the same face to the sun.</ref> In fact, current tidal forces exerted by the Earth on the Moon cannot account fully for its bulge or egg shape.<ref>"[http://physics.fortlewis.edu/Astronomy/astronomy%20today/CHAISSON/AT308/HTML/AT30803.HTM Chapter 8, Section 3: The Rotation of the Moon]," "Astronomy Today", Department of Physics, Fort Lewis College, Durango, [[Colorado|CO]]. Accessed February 18, 2008</ref>

===Lunar origin theories===

The current scientific consensus is that the Moon originated from a collision early in Earth's history which created an orbiting ring of debris from the [[iron]]-poor surface of the planet which eventually coalesced into the moon.<ref>http://www.astronomy.com/asy/default.aspx?c=a&id=2198</ref>

Biblical history records the Moon being created on the fourth day of [[creation week]], along with the Sun:

{{Bible quote|And God said, Let there be lights in the firmament of the heaven to divide the day from the night; and let them be for signs, and for seasons, and for days, and years: And let them be for lights in the firmament of the heaven to give light upon the earth: and it was so. And God made two great lights; the greater light to rule the day, and the lesser light to rule the night: [he made] the stars also. And God set them in the firmament of the heaven to give light upon the earth, And to rule over the day and over the night, and to divide the light from the darkness: and God saw that [it was] good. And the evening and the morning were the fourth day.|book=Genesis|chap=1|verses=14-19|version=KJV}}

===Rate of recession===

The Moon currently recedes from the Earth at a rate of 1.5 inches (3.8 cm) per year,<ref>NASA [http://sunearth.gsfc.nasa.gov/eclipse/SEhelp/ApolloLaser.html Measuring the Moon's Distance], LPI Bulletin, No. 72, August, 1994.</ref> and is believed by [[atheist]]ic scientists to be 4.6 billion years old,<ref>NASA, [http://history.nasa.gov/SP-350/ch-15-2.html Apollo Expeditions to the Moon], Chapter 15.2.</ref> The Moon could never have been closer than about 11,000 miles or it would have been broken up by tidal forces.<ref name="js">Sarfati, Jonathan, [http://www.creationontheweb.com/content/view/764/ The moon: the light that rules the night], ''Creation'' 20(4):36–39, September 1998.</ref> If the rate of recession stayed constant at 3.8 cm per year, it would take 9.6 billion years for the lunar distance to migrate from 11,000 miles to the present distance of about 240,000 miles. However these assumptions are very inaccurate as the rate of recession would definitely not be constant over the past 4 billion years. 

===Impact craters===
Astronomers assume that crater impacts are a reliable indicator of the age of a celestial body. True to the form and principles of [[uniformitarianism]] (as applied to [[astronomy]] rather than to [[geology]]), any such estimation relies upon uniform constants and weather/erosion trends. Recent research into crater impacts on the moon suggests that many of the assumptions previously made are unwarranted. Bonnie Buratti of NASA's Jet Propulsion Laboratory has asserted that space weathering "takes place very rapidly on the Moon."<ref>David, Leonard. "[http://www.space.com/missionlaunches/lunar_impact_021214.html Lunar Crash of 1953: Impact Crater Identified]." <http://www.space.com>, December 14, 2002. Accessed January 16, 2008.</ref> Peter Brown of the University of Western Ontario insists that there is no absolute criteria for the dating of craters.<ref>Hecht, Jeff. "[http://www.newscientist.com/article.ns?id=dn3242 New crater revives Moon mystery]." <http://www.newscientist.com>, January 11, 2003. Accessed January 16, 2008.</ref>

===Creationist models===
Danny Faulkner of the [[Institute for Creation Research]] has observed that many of the lunar maria contain ''ghost craters'', or craters that the lava flow that produced the maria seem to have filled only partially. In the [[deep time]] scale required by [[uniformitarianism]], the ghost craters are the result of impacts that occurred as much as half a gigayear before the crust-fracturing impacts that caused the lava flows.<ref name=Henderson>Henderson, Thomas H. "[http://www.hal-pc.org/~tom/HeavyCratering.html Do heavily cratered planets and moons demand an old age for the solar system]?" ''Tom Henderson's Creation Resources'', July 25, 2003. Accessed March 25, 2008.</ref> This is not a reasonable assumption, because any impact strong enough to crack the crust should have obliterated any craters previously extant. Faulkner thus concludes that the impacts that formed the ghost craters, and those that let loose the lava flows that formed the maria, occurred within days of one another<ref name=Faulkner1>Faulkner, Danny. "[https://www.icr.org/research/index/researchp_df_r01/ The Current State of Creation Astronomy]." ''Proceedings of the Fourth International Conference on Creationism,'' Creation Science Fellowship, Pittsburgh, pp. 201–216, August 3–8, 1998. Hosted at ''[[Institute for Creation Research]].'' Accessed March 25, 2008.</ref> and were probably part of at least one system-wide catastrophe involving a narrow stream of meteoroids and/or comets that delivered a concentrated bombardment of the Earth and Moon in a short interval.<ref name=Faulkner2>Faulkner, Danny. "[http://creationontheweb.com/content/view/1637 A Biblically-based cratering theory]." ''Technical Journal'' (now ''Journal of Creation''), 13(1):100-104, April 1999.</ref>

Faulkner assumes that this system-wide catastrophe occurred during the year of the [[Great Flood]]. But in 1984, Russell Humphreys, then at the Sandia National Laboratories, developed evidence suggesting different dates entirely. Specifically, the [[Project Apollo]] exploration teams brought back many samples of [[basalt]] (an [[igneous rock]]) and [[brecchia]] (pulverized meteor-impact remains). Geologists analyzed both types of samples and found evidence that each type of rock had once been in a magnetic field far more powerful than that which the Moon has today. Using his model for the creation and decay of magnetic fields,<ref name=Humphreys/> Humphreys determined that the basalt had been laid down about 370 years after creation, and the brecchia had been laid down 1840 years after creation, or about 190 years after the Flood.<ref name=Humphreys2>Humphreys reasoned that the higher the magnetic dipole moment of the samples, the earlier in lunar history they were formed.</ref> These findings clearly suggest that the Moon, and presumably all other bodies in the solar system, have been subject to two separate system-wide bombardments, one occurring in the second or third generation after the [[fall of man]] and the other occurring well after the Flood.

==Tides==

The gravitational force of the Moon causes the ocean [[tides]]; these tidal forces have other effects as well. These tidal forces have the effect of creating resistance which slows down the rotation of both objects. In the case of the Earth, the result is that the Earth's rotation slows on the order of one millisecond per century. The Moon's rotation is locked in to its period of revolution, and the same side of the Moon always faces the Earth.

==The "dark" or far side==

The phrase "the ''dark'' side of the Moon" is inaccurate because the Moon does rotate relative to the Sun, with the same period as its period of revolution, once every 29 days. Our view of the Moon from the Earth always shows the same side of the Moon, with the same markings and features. When the Moon is full, the entire side that faces us is experiencing lunar "day" and is lit by the Sun. Two weeks later, when the Moon is new, the side that faces us is experiencing solar "night" and is unlit (and virtually invisible).

The far side of the moon is far more heavily cratered than the near, and the predominant type of cratering is consistent with brecchia-forming meteor impact. This would suggest that the far side suffered its bombardment in the latter of the two catastrophes that Humphreys suggests that the Moon has suffered.

Due to a slight "wobble" in the lunar motion called ''libration,'' we actually see a little bit more than half of the Moon's surface; sometimes it is turned a bit one way and sometimes the other. However, nobody had any idea of what the far side of the Moon looked like until 1959, when a Soviet satellite photographed it and relayed pictures back.
==Earthshine==
[[image:oldmooninnew.jpg|200px|right|thumb|The "old Moon in the new Moon's arms"]]
In the old Scottish ballad ''Sir Patrick Spens'',<ref>Child, Francis James (1860), ''The English and Scottish Popular Ballads,'' [http://www.sacred-texts.com/neu/eng/child/ch058.htm No. 58]; the ballad is thought to refer to an actual event of the year A.D. 1290.</ref> a [[sailor]] cautions:

:"I saw the new moon late yestreen
::With the old moon in her arm;
:And if we go to sea, master,
::I fear we'll come to harm."

The effect known as "the old Moon in the new Moon's arms" can often be seen when the Moon is a narrow [[crescent]]. Within the intensely bright crescent, a dim and mysterious view of the entire circular moon is seen. The effect is also known as ''earthshine'' because it is light from the Sun reflected off the Earth to the Moon and back that lights up the darker portion of the Moon. The bright crescent is lit by the Sun and is in full daylight. The rest of the Moon is not lit by the Sun; but an [[astronaut]] standing in this area would see a "full Earth" dominating the nighttime sky, lighting it up by its earthshine. The brightness of Earthshine, and hence the visibility of the old Moon in the new Moon's arms, varies. When the Earth is covered with clouds, or when there is a lot of snow-pack on the side of the Earth facing the Moon, the Earth is a white and bright and the Earthshine is intense. When the Earth looks like a "big, blue marble," it is less intense.

==Lunar calendars==

Throughout history, many calendar systems have been based on the phases of the moon.

The months of the [[Islam|Muslim]] [[calendar]] are determined by observations of the [[hilal]], the moment at which the thin crescent moon first becomes visible. This marks the start of a month. Traditionally, and today in [[Pakistan]] and [[Jordan]], hilal is determined by actual observation and can be affected by weather and other factors. When following the traditional method, it is not actually possible to be certain precisely when future months will begin. In most Muslim countries, actual observation has been replaced by [[astronomy|astronomical]] rules.

== Magnetism Mystery ==

Rocks on the Moon are magnetized, yet there is no magnetic field there today. In one new proposal, researchers at the University of California have suggested that the moon's solid-rock middle layer, called its mantle, stirs up its liquid iron core. The researchers believe this happens because the moon's core and its mantle rotate around slightly different axes, and the boundary between them is not quite spherical.

The strength of this stirring is determined by the angle between the core and the mantle, and the distance between the Earth and the moon, because the tidal forces from the Earth causes the moon's mantle to rotate differently than the core.

This model would explain why the moon no longer has a magnetic field. Since the angle between the mantle and the core has narrowed over time, while the distance between the moon and the Earth has widened, this has caused the tidal forces to steadily decrease. While these forces used to be enough to generate a dynamo inside the moon, they aren't anymore.
<ref>https://www.csmonitor.com/Science/2011/1109/Have-scientists-finally-solved-the-mystery-of-the-magnetic-moon</ref>

==The Moon in culture==

"The Old Moon in the New Moon's Arms" is the title of a poem by [[Ella Wheeler Wilcox]], in which she interprets the effect as the New Moon wishing that her lost love, the Old Moon, be in her arms one last time; Venus grants the wish, and:

:Swift thro' the vapors and the golden mist—
::The Full Moon's shadowy shape shone on the night,
:The New Moon reached out clasping arms and kissed
::Her phantom lover in the whole world's sight.

== Other moons ==
[[Image:Many_Moons.jpg|250px|left]]
While the Moon of Earth is the best-known satellite of any [[planet]], other planets in our solar system also have moons. Earth has the least number of moons (one), while [[Jupiter]] has sixty-two. The first extraterrestrial moons to be discovered were the four Galilean moons ([[Io]], [[Europa (moon)|Europa]], [[Ganymede]], and [[Callisto]]). Next to these, Earth's Moon is one of the largest, but Jupiter and [[Saturn]] have moons in orbit about them that might qualify as planets if they orbited the [[Sun]] instead.
{{clear}}
===Moons in our solar system===
{| class="wikitable"
|-
! Planet !! Number of moons !! Moon names
|-
| Earth || 1 || "Moon" or Luna
|-
| Mars || 2|| Deimos & Phobos
|-
| Jupiter || 79 ||
|-
| Saturn || 62 ||
|-
| Uranus || 27 ||
|-
| Neptune || 14 ||
|-
|Pluto (dwarf) || 5 || Charon, Nix & Hydra
|-
| Haumea (dwarf) || 2 ||Namaka & Hi'iaka
|-
|Eris || 1 || Dysnomia
|}
There are at least 182 natural moons known to exist in our solar system, counting those which are in orbit of dwarf planets.<ref>https://windows2universe.org/our_solar_system/moons_table.html (Retrieved April 9, 2019)</ref><ref>https://www.universetoday.com/15516/how-many-moons-are-in-the-solar-system/ (Retrieved April 9, 2019)</ref><ref>https://space-facts.com/moons/ (Retrieved April 9, 2019)</ref><ref>https://spacedictionary.org/moons/ (Retrieved April 9, 2019)</ref>
=== Sizes of moons ===
Most moons in the solar system are no larger than typical asteroids. They are of irregular shape, have light and variable surface gravities, and are often unstable in their orbits. [[Phobos]] and [[Deimos]], the moons of [[Mars]], fall into this category.

Earth's own moon is an example of a [[dwarf planet]]-sized moon. These moons are so large that their own self-gravity forces them to collapse into spheres or spheroids. Some of them, like [[Ganymede]] and [[Titan (moon)|Titan]], are larger even than the planet [[Mercury]]. Earth's moon was, of course, known to the ancients, but the remaining dwarf-planet-sized moons were generally the first to be discovered in orbit around any given primary. [[Galileo Galilei]] discovered the first four of these in orbit about [[Jupiter]] early in the seventeenth century; [[Christiaan Huygens]] then discovered Titan of [[Saturn]] later in that same century.

== Symbolic importance in Islam ==
The crescent moon is an internationally recognized symbol of [[Islam]]. It appears on the flags of several Islamic nations. It also forms part of the official emblems of the International Red Cross and Red Crescent Societies.<ref>http://islam.about.com/od/history/a/crescent_moon.htm</ref>

== See also ==
*[[Origin of the Moon]]
== External links ==

*[http://www.solarviews.com/eng/terms.htm Glossary]
==Further reading==
* Donna Henes. ''The Moon Watcher's Companion: Everything You Ever Wanted to Know About the Moon, and More'' (2004) [https://www.amazon.com/Moon-Watchers-Companion-Everything-Wanted/dp/1569244669/ref=sr_1_11?ie=UTF8&s=books&qid=1241592218&sr=1-11 excerpt and text search]
* David Schrunk et al. ''The Moon: Resources, Future Development and Settlement'' (2007) [https://www.amazon.com/Moon-Resources-Development-Settlement-Exploration/dp/0387360557/ref=sr_1_12?ie=UTF8&s=books&qid=1241592379&sr=1-12 excerpt and text search]
* Seymour Simon, ''The Moon'' (2003) [https://www.amazon.com/Moon-Seymour-Simon/dp/0689835639/ref=sr_1_1?ie=UTF8&s=books&qid=1241592218&sr=1-1 excerpt and text search]

== Notes and References ==
{{reflist|2}}
{{Solarsystem}}
[[Category:Astronomy]]
[[Category:Moon]]

Black hole

2020-09-04T02:16:36Z

TrueStandish: Fact adjustmentt

[[Image:Iu8969hu.jpg|right|thumb|300px|Artist's conception of a binary system consisting of a black hole (upper left) and a main sequence star (lower right). The black hole is drawing matter from the star via an ''accretion disk'' (blue) around it, and some of this matter forms a gas jet (also blue).]]
A '''black hole''' is a formation in space with near-[[infinity|infinite]] density and sufficient gravitational force that escape velocity exceeds the speed of light. Thus, "black" refers to the impossibility of any light ([[photon]]s) escaping, thereby making them completely dark.<ref>They are assumed to come into existence from extremely large stars that collapse into a state of high density when they run out of fusion fuel. An object becomes a black hole when it lies entirely inside the Schwarzschild radius (see below) determined by its mass. For most objects, the Schwarzschild radius is very tiny compared with its size (for Earth it is about 1 centimeter), so the object could not lie inside that radius.</ref>

Black holes are reported by reliable publications, such as the science page of the ''[[New York Times]]'', glossy magazines, and movies including ''Event Horizon'' (1997), ''The Black Hole'' (TV, 2006), and ''Interstellar'' (2014). Black holes fail the [[falsifiability]] requirement of science, because it is impossible to prove that they do not exist anywhere in the universe. Black holes also have meaning in everyday speech, as in "his office has become a black hole!"

Black holes had never been directly observed, and there is no direct evidence for their existence. In early 2019 astronomers released a photo-shopped image of a super-massive black hole located in the galaxy Messier 87 - some 55 million light-years away<ref>https://www.washingtonpost.com/science/2019/04/10/see-black-hole-first-time-images-event-horizon-telescope/</ref>. That alleged black hole has since been informally named "Powehi".<ref>http://time.com/5569262/black-hole-hawaii-powehi/</ref>

Evidence for the existence of black holes relies on the observations of radiation from accretion disks, motion of stars near the center of the galaxy, and "gravitational lensing," around places where there are no visible objects. Most the evidence for the existence of black holes relies on circumstantial evidence, with heavy reliance on theoretical equations.

Because of [[quantum mechanics|quantum-mechanical]] phenomena involving Hawking Radiation, discussed later in the article, black holes must emit radiation and thus are not ''perfectly'' black. Nevertheless, they are called "black holes". Quibbling about this is similar to quibbling about the statement "The Earth is round".

Black holes are conceptually associated with "[[wormhole]]s",<ref name="nytimes.com">The prediction of the existence of wormholes, and its naming in 1957, predates the prediction and naming (1967) of a black hole.[https://www.nytimes.com/2008/04/14/science/14wheeler.html?pagewanted=print]</ref> which never caught on with the public, perhaps due to its unattractive terminology.

==Mathematical description==
A '''black hole''' is any object that lies entirely inside its own Schwarzschild radius, given by
:<math>r=\frac{2G}{c^2}\ m</math>
where
*G is Newton's gravitational constant;
*c is the speed of light;
*m is the mass of the object.

Numerically,
:<math>r=1.5 \times 10^{-27}\ m</math>
in meters and kilograms.

This is a concept of gravity, under [[General Relativity]]. For any normal object, from things one would see on Earth up to stars that are not extremely massive or dense (much more massive or dense than the Sun), the Schwarzschild radius is very tiny relative to the object. This means that the object does not lie inside that radius, and cannot be a black hole. For example, the Schwarzschild radius of the Earth is about one centimeter, and that of the Sun is about three kilometers. The Earth could only become a black hole if it were compressed into a radius of one centimeter.

What makes the Schwarzschild radius significant is that the behavior of gravity, under General Relativity, is determined by the Schwarzschild metric, and is (not surprisingly) nearly identical to the behavior given by Newton's law of gravity. The difference only shows up at distances at or near the Schwarzschild radius. If the Earth were compressed to a radius of one centimeter or less, the behavior of gravity would become radically different as one approached that distance. Normal world-lines would cease to be "time-like", and such world-lines would be unable to make progress from inside the Schwarzschild radius to outside of it. This is a rather paradoxical situation when viewed in the way we normally view the way the universe works. In short, no object, and no light, can actually pass from inside the radius to outside. The surface at this radius is called the '''event horizon'''.

The concept of the Schwarzschild radius was worked out by Karl Schwarzschild in 1916, as part of his solution (the first solution ever worked out) of Einstein's field equation for General Relativity. At first, neither Einstein nor Schwarzschild believed that something could be so dense that these objects could exist.

==Pre-history==
The notion of something that has gravity so strong that light can't escape actually dates back to the 18th century, when scientists became aware of the finite speed of light and the concept of escape velocity. The corpuscular theory of light held that light was made up of invisibly small particles, and that these particles moved along ballistic trajectories, like tiny bullets. In this framework, it was believed possible that a distant star could be so massive that light emitted from its surface would be dragged back down again. This theory was first advanced by John Michell, who wrote in 1783, "If the semi-diameter of a sphere of the same density as the Sun in the proportion of five hundred to one, and by supposing light to be attracted by the same force in proportion to its [[Mass (science)|mass]] with other bodies, all light emitted from such a body would be made to return towards it, by its own proper gravity."<ref name="r1">http://www.aps.org/publications/apsnews/200911/physicshistory.cfm</ref>

Suggesting the same possibility independently, Pierre-Simon Laplace wrote in 1796, "It is therefore possible that the greatest luminous bodies in the universe are on this account invisible."<ref name="r1" />

This appeared to depend on the corpuscular theory of light, which gave way to the [[wave theory of light]] in the early 19th century, so the idea of "dark" or "invisible" stars fell from favor. It was believed that light, being a wave and having no mass, might be unaffected by gravity. Research into [[quantum mechanics]], however, reignited interest in the light-as-particles view, ultimately resulting in the modern notion of [[wave-particle duality]]. Under this theory, light could be affected by gravity, so the question of whether light could be emitted from extraordinarily massive bodies was once again open.

But the wave-versus-particle nature of light turned out to be a [[red herring]]. Under the "equivalence principle", it is known that anything, wave, particle, or whatever, that can be construed to have a trajectory, will have that trajectory bent by a gravitational field.

But none of this mattered at the time. A star (or other body) large enough to show this effect was utterly inconceivable. A sphere of Uranium at its normal density would have to weigh 10 million times the mass of the Sun, and be as large as the Earth's orbit, to lie inside its Schwarzschild radius. (Though such a large block of Uranium would not have its normal density.)

And the term "black hole" was unheard-of.

==20th century history==
By the mid-20th century, the physics of stellar dynamics and quantum mechanics had advanced to the point that it was possible to conceive of incredibly dense objects. Stars such as the Sun are actually "inflated" to their current size by the radiation pressure from the fusion reactions going on within them. When stars have consumed all their fuel, that pressure stops, and the material collapses to a much smaller size. The normal interatomic spacing, with electrons orbiting the nuclei, no longer applies. A variety of things can occur, including the electrons combining with the protons to make a "neutron star". Various phenomena were formulated, such as neutron stars, supernovas, pulsars, and magnetars. Before long these objects were actually observed. (Pulsars were observed before the theory had been worked out, and supernovas had been observed since antiquity.)

Stellar evolution and dynamics are quite complicated. Once a star has burned up all its Hydrogen, it may, depending on its size, burn Helium, and then heavier elements, all the way up to Iron. (Iron is the most stable nucleus; fission or fusion of Iron nuclei is not energetically favored.) As the material becomes more compressed, it is held up by the "electron degeneracy pressure" instead of the normal radiation pressure. The normal atomic structure, with orbiting electrons, is replaced by a collection of nuclei and unbound electrons, obeying the rules of quantum mechanics, particularly the Pauli exclusion principle. This pressure generally stops further collapse, leading to a [[white dwarf]]. White dwarfs may continue accreting matter from nearby objects. If the mass is over the "Chandrasekhar limit" of 1.4 solar masses, the gravitational force is too strong even for the degeneracy pressure, and the star becomes a supernova, neutron star, or black hole. The theory of this gravitational collapse was worked out in the 1930's.

If the mass is greater than the Tolman-Oppenheimer-Volkoff limit of about 1.5 solar masses, the neutron star becomes a black hole.

The properties of these objects (the "event horizon", and matter and information may only pass through the event horizon in one direction) were worked out in the 1950's. The exact solutions to Einstein's equation were worked out in the 1960's for rotating black holes (the Kerr solution), electrically charged black holes (the Reissner-Nordström solution), or both (the Kerr-Newman solution). Various theorems relating to thermodynamics were worked out by Stephen Hawking in the 1970's.

The term "black hole" was coined by John Wheeler in 1967. The term caught on very quickly in both the scientific community and the public at large, helped by the catchy nature of the phrase. Because of the remarkable nature of black holes, the concept quickly became a staple of science fiction stories, "popular" science magazines, television shows, and movies such as ''Event Horizon'' (1997), ''The Black Hole'' (TV, 2006), and ''Interstellar'' (2014). The latter movie put a lot of effort into making the visual depiction of the black hole scientifically accurate.

This was all theoretical at the time. There was no evidence that a black hole actually existed until the early 1970's, when scientists began to suspect that the radio source "Cygnus X1" was an actual black hole, and the 1990's, when scientists began to suspect that there was a black hole near the radio source "Sagittarius A*" at the center of our galaxy. (The name is pronounced with the word "star".) Since then evidence has accumulated that enormous black holes lie at the center of many galaxies.

==Methods of Observation==
Black holes are literally invisible by traditional means of observation (that is, emission or reflection of some sort of radiation) and so cannot be directly observed, their nature is determined by other means. That said however, as particles near the event horizon their velocity increases and particles are drawn closer and closer together resulting in friction which caused a radioactive accretion disc which can be observed on the electromagnetic spectrum not visible to the eye.<ref>https://www.physicsoftheuniverse.com/topics_blackholes_event.html</ref><ref>{{cite journal
|last1=Gillessen |first1=S.
|last2=Eisenhauer |first2=F.
|last3=Trippe |first3=S.
|last4=Alexander |first4=T.
|last5=Genzel |first5=R.
|last6=Martins |first6=F.
|last7=Ott |first7=T.
|display-authors=3
|title=Monitoring Stellar Orbits around the Massive Black Hole in the Galactic Center
|journal=The Astrophysical Journal
|volume=692
|issue=2|page=1075|date=2009
|doi=10.1088/0004-637X/692/2/1075
|arxiv=0810.4674
|bibcode=2009ApJ...692.1075G
|ref=harv
}}</ref> Since 1995, astronomers have tracked the motions of 90 stars orbiting an invisible object coincident with the radio source in the center of our galaxy, Milky way. The astronomers were able to infer that a 2.6 million sollar mass object must be contained within the radius of 0.02 [[light-year]]s to cause the motions of those stars.<ref name="Ghez1998">{{cite journal
|last1=Ghez |first1=A. M.
|last2=Klein |first2=B. L.
|last3=Morris |first3=M.
|last4=Becklin |first4=E. E.
|display-authors=3
|title=High Proper‐Motion Stars in the Vicinity of Sagittarius A*: Evidence for a Supermassive Black Hole at the Center of Our Galaxy
|journal=The Astrophysical Journal
|volume=509
|issue=2|page=678|date=1998
|doi=10.1086/306528
|arxiv=astro-ph/9807210 |bibcode=1998ApJ...509..678G
|ref=harv
}}</ref>

Colliding black holes should produce gravitational waves, possible to detect experimentally. On 24 September 2015 the [[LIGO]] observatory made the first-ever successful observation of such event.<ref name="PRL-20160211">{{cite journal |author=Abbott, B.P. |title=Observation of Gravitational Waves from a Binary Black Hole Merger |url=http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.061102 |journal=[[Phys. Rev. Lett.]] |volume=116 |pages=061102 |year=2016 |doi=10.1103/PhysRevLett.116.061102 |display-authors=etal|arxiv = 1602.03837 |bibcode = 2016PhRvL.116f1102A }}</ref><ref name="NYT-20160211-db">{{cite news |last=Overbye |first=Dennis |authorlink=Dennis Overbye |title=Physicists Detect Gravitational Waves, Proving Einstein Right |url=https://www.nytimes.com/2016/02/12/science/ligo-gravitational-waves-black-holes-einstein.html |date=11 February 2016 |work=[[New York Times]] |accessdate=11 February 2016 }}</ref> The signal was consistent with theoretical predictions. The gravitational wave signal suggests that the separation of the two holes prior to merger was just 350 km, hence they must be small in size, leaving black holes as the most plausible interpretation.

While matter and energy, even light, may not escape a black hole, Stephen Hawking has shown that when described by quantum mechanics, they should emit [[Hawking radiation]], which absent of an influx of mass-energy would lead to the evaporation of the black hole in a burst of gamma rays. This radiation may be possible to observe. However all results obtained to date remain unverified and debatable.<ref name="Milanoguys">{{cite journal|title=Hawking radiation from ultrashort laser pulse filaments |first1=F. |last1=Belgiorno |first2=S. L. |last2=Cacciatori |first3=M. |last3=Clerici |first4=V. |last4=Gorini |first5=G. |last5=Ortenzi |first6=L. |last6=Rizzi |first7=E. |last7=Rubino |first8=V. G. |last8=Sala |first9=D. |last9=Faccio |arxiv=1009.4634 |doi=10.1103/PhysRevLett.105.203901 |date=2010 |journal=Phys. Rev. Lett. |volume=105 |page=203901}}</ref><ref>{{cite news|title=Ultrafast Laser Pulse Makes Desktop Black Hole Glow|newspaper=[[Wired (magazine)|Wired]]|date=September 29, 2010|first=Lisa|last=Grossman|url=https://www.wired.com/wiredscience/2010/09/hawking-radiation-in-the-lab/|accessdate=April 30, 2012}}</ref>

==History of the idea==

===General Relativity===
As it happened, the question became unavoidable shortly after the publication in 1915 of Einstein's [[general theory of relativity]]. Karl Schwarzschild solved the Einstein field equations in a way that describes the geometry of spacetime outside a spherically symmetric, uncharged, non-rotating distribution of mass. Well away from the center of this distribution of mass, the Schwarzschild solution closely matches the Newtonian model of a gravitational field; only close to the mass, where the curvature of spacetime is large, do significant differences between the two models appear. But if the diameter of the mass distribution is taken to be arbitrarily small, then the region of spacetime immediately surrounding the mass appears to take on extremely curious properties, properties so curious that many questioned whether they had any physical interpretation at all. Therefore, Schwarzschild showed that black holes were possible under the theory of [[general relativity]].

[[File:Cygnusx1.jpg|right|200px|thumb|Jet-powered nebula formed from the accretion disk of the binary star Cygnus-X1]]
However, neither Schwarzschild himself nor [[Albert Einstein]], who developed the theory of relativity, believed that black holes actually existed.<ref name="amazing-space.stsci.edu">http://amazing-space.stsci.edu/resources/explorations/blackholes/lesson/whatisit/history.html</ref> Einstein even tried to re-work general relativity to render these [[Singularity|singularities]] impossible. However, Roger Penrose and Stephen Hawking proved the first of many Singularity Theorems, which states that singularities must form if certain conditions are present. This demonstrated that, rather than mathematical oddities, singularities are a fairly generic consequence of realistic solutions to relativity: any mass with radius less than its Schwarzschild radius is a black hole. Since then, support for black holes among the scientific community has grown.

==Nature of a Black Hole==
===Mathematics===

There are several solutions of the Einstein field equations that are used to model black holes. The simplest of these is the Schwarzchild metric. From this metric, one can calculate the Schwarzschild radius, which defines the boundary (event horizon) of the black hole, to be
:<math>r_s=\frac{2GM}{c^2}</math>,
where
* rs is the Schwarzschild radius;
* G is the gravitational constant;
* M is the mass of the gravitating object;
* c is the speed of light in vacuum.

If the black hole has a nonzero electric charge, it is modeled by the Reissner-Nordström metric. Astronomical objects are generally electrically neutral, since otherwise they would attracted charged particles of opposite sign and quickly become neutral. Therefore, the Reissner-Nordström metric is largely of theoretical interest.

A far more realistic situation occurs when the black hole is spinning (i.e. has nonzero angular momentum). Then the Schwarzschild solution is insufficient (as it was for the charged case), and instead one turns to the Kerr metric. Since astrophysical black holes are generically believed to have angular momentum, this is the solution that best describes them. Among the more interesting consequences of the Kerr metric is the phenomenon of frame dragging, in which the rotating black hole literally pulls nearby spacetime along with it.

If one wishes to consider a black hole that is both charged and spinning, one employs the Kerr-Newman metric, which combines the Reissner-Nordström and Kerr metrics. Since the no-hair theorem states that (non-quantum) black holes are unique up to mass, charge, and angular momentum, the Kerr-Newman metric is sufficient to describe any classical black hole.

===Time and Distance===
Within a certain distance from an arbitrarily small distribution of mass — a distance now known as the [[Schwarzschild radius]] — the curvature of spacetime becomes so great that no paths leading away from the mass exist. That is to say, a test particle released inside the Schwarzschild radius will inevitably move in toward the mass, not because the force of gravity is great as in the Newtonian approximation, but because spacetime is curved to such an extent that ''no other directions exist.'' A particle within the Schwarzschild radius can no more move further from the central mass than it can go backwards in time. In fact, from the frame of reference of an infalling observer beyond the Schwarzschild radius, all directions that once pointed away from the central mass now point backwards in time. Once inside the Schwarzschild radius, further motion toward the central mass is as inevitable as further motion through time is for any other observer.

For some time after the publication of the Schwarzschild solution, the validity of these results was hotly debated. In the solution's original coordinate frame, some terms in the equations ''diverged,'' or became infinite, at the Schwarzschild radius, leading physicists to wonder whether the results of the equations in that region had any valid physical interpretation. One proposed interpretation was that at the Schwarzschild radius, all time for the infalling observer would stop. This led to the use of the term "frozen stars;" it wasn't believed frozen stars were cold, but rather that they were literally frozen in time.

Later refinement of the Schwarzschild solution demonstrated that the apparent infinities were merely an artifact of the coordinate frame chosen, and that an infalling observer in fact can pass beyond the Schwarzchild radius. In fact, the equations predicted he would notice no effects when doing so. But any attempt on the part of that infalling observer to communicate with the outside universe, say by sending a radio message, would be doomed to failure, as the radio waves would traverse geodesics through the severely curved spacetime and end up bent toward the central mass. From this, we can say that nothing that occurs within the Schwarzschild radius can ever affect events outside the Schwarzschild radius. This gives the Schwarzschild radius of a non-rotating black hole its other name: the [[event horizon]].

===Inside the Event Horizon===
What actually exists inside the event horizon of a black hole is a question physics is unable to answer, as it seems to defy reason. Some postulate that within the event horizon exists a point of zero (or nearly zero) volume but infinite energy density, a point sometimes referred to as a ''gravitational singularity,'' after the notion of a mathematical singularity (a term referring to a point in an equation at which one would have to solve by dividing by zero, a feat presently impossible in mathematics) in a field equation. The closest mathematics is able to come to this is an infinite limit. Others suspect that infinite energy density is a physical impossibility, and that a black hole contains actual finitely-dense matter compressed into a [[degenerate matter|degenerate]] form, such as quark-degenerate matter. Since all black holes are surrounded by an event horizon which prevents any information or messages from leaving, all these theories are non-[[falsifiable]]; we can never be sure what the interior structure of a black hole is like.

===Properties of Black Holes===

Black holes described with classical mechanics only have three intrinsic properties by which one differs from another: mass, electric charge, and angular momentum. Mass describes the amount of matter inside the event horizon. Angular momentum refers to whether the black hole is stationary or rotating around an axis. While the singularity of a non-rotating black hole may be an infinitely small point, the singularity of a rotating black hole would be in the shape of an infinitely thin ring. Quantum mechanics, which postulates that information loss cannot occur in a black hole, suggests properties beyond the three suggested by classical physics. Using this description, information must also be emitted by black holes. This radiation, referred to as Hawking Radiation, is thermal radiation that has currently only been described mathematically.

Although radiation from inside the event horizon has not yet been observed, there is much phenomenon that occurs outside the horizon due to the black hole. Matter entering a spinning black hole is first swirled around by the black hole’s gravity, causing it to heat up and emit x-rays, which can be used to detect the black hole. In the supermassive black holes at the centers of galaxies, some of the matter does not fall into the black hole. Instead it is blasted into space in twin jets of hot gas perpendicular to the accretion disc, in a phenomenon known as an Active Galactic Nucleus.

==Origins of Black Holes==
[[Image:Hs-2005-02-e-web.jpg|right|thumb|300px|The [[red supergiant]] star V838 Monocerotis, an example of one type of star which may become a black hole.]]
Stellar-mass black holes are said to form when stars more than ten times the mass of the Sun run out of fuel and die. The process of death occurs when stars that have fused the products of their own fusion into larger and larger elements, up to iron. The star then tries to fuse the iron core that forms as a result, but this does not produce enough energy to hold the outer layers of the star apart against the pull of gravity. When this happens, the iron core at the center of the star implodes in a supernova, and the outer layers of the star are blasted into space in one of the most energetic events in the universe—one star going out in a supernova can give off as much light as an entire galaxy. Not all supernovae result in black holes, but if the mass of the core is large enough, about 1.5-3.0 times the mass of the Sun (this value is termed the Tolman-Oppenheimer-Volkoff limit, and its value is not yet known to great precision), the leftover gravity of the shrinking core stalls the outward rush of the initial blast, and crushes the core into a point of infinite density: a black hole.

Extremely small black holes, with masses of around 1015 grams, have been theorized to have formed in the early universe. Any sufficiently small primordial black hole would be expected to evaporate within the lifetime of the universe, but the rate of evaporation is not currently known with any certainty.

At the opposite end of the spectrum, objects with the characteristics of supermassive black holes, millions or billions of times more massive than the sun, have been detected at the centers of many [[galaxies]], including our own [[Milky Way]]. In our galaxy, the hypothesized supermassive black hole is in the constellation Sagittarius, and is known as Sagittarius A* (pronounced "A star"). Based on the extraordinary angular velocity of stars near the galactic center, Sagittarius A* is believed to be on the order of two to three million solar masses. It is unknown how supermassive black holes form, though several models have been proposed. One hypothesis simply begins with a black hole of stellar mass which grows over the lifetime of the galaxy that surrounds it. Another proposal describes supermassive black holes as a natural, in fact nearly unavoidable, consequence of galactic formation. To date, no one theory of supermassive black hole formation is favored over all others.

Physicists trying to understand the theory of black hole formation have once again hit a dead end.<ref>http://www.fromquarkstoquasars.com/new-research-mathematically-proves-quantum-effects-stop-formation-black-holes/</ref>

==Speculative Future Exploration==

Scientists have speculated that if a rotating black hole is large enough, a person could pass through the center of the ring-shaped singularity and possibly enter a wormhole. However, it would have to be a very large hole, for if it were not, the hypothetical astronaut would never survive to reach the event horizon due to tidal forces.

Matter coming close to the event horizon of a small black hole undergoes a process called spaghettification, a term coined by Stephen Hawking in his book ''A Brief History of Time'' to describe extraordinarily strong tidal forces. Because the mass at the center of the black hole is so dense, the gravitational pull on the near end of an object is much greater than the pull on the object’s far end. This causes the object to be stretched out in a way resembling a piece of spaghetti, and generally torn in two.

==White Holes==
Because the [[Quantitative Introduction to General Relativity|general relativity equations]] are symmetric with respect to time, one can reverse the time parameter to yield an equation describing a hypothetical object which expels, rather than attracts, matter and energy.<ref>http://cosmology.berkeley.edu/Education/BHfaq.html#q10</ref> As this is the exact opposite of a black hole, it is called a '''white hole'''.

However, there is no evidence white holes actually exist. If they generate new matter and energy, this would violate the [[Law of the conservation of mass]]. Therefore, some scientists have proposed that matter falling into black holes goes through a [[wormhole]] to emerge at a white hole. While such wormholes are allowed by general relativity, they would be extremely unstable,<ref>http://casa.colorado.edu/~ajsh/schww.html</ref> and there is no evidence that they exist.

Scientists, who have been extremely eager to promote the idea of black hole existence, have shown a strong aversion to the white hole theory, even though, like a white hole, a black hole has never been observed directly. This may reflect an anti-creation bias on the part of scientists who are uncomfortable with the idea that matter and energy can be created outside of what scientific theories dictate should happen.

Fundamentalists and creationists have used white holes to attempt to solve the cosmic time problem. Dr. [[Russell Humphreys]] used a white hole in his model of the universe during [[Creation week]] to allow millions of years to pass in outer space while only three days passed on Earth.

==In Popular Culture==
Black holes are increasingly promoted by [[liberal]] publications, such as the science page of the ''[[New York Times]]'', glossy magazines, and the movies the ''Event Horizon'' (1997), ''The Black Hole'' (TV, 2006), and ''Interstellar'' (2014). They are sometimes seen as [[sacred cow]]s of [[atheistic science]], and used to be commonly mentioned in atheistic propaganda. However both proving or disproving of the actual existence of black holes does not very obviously support any religion-related view.

Black holes have been a device in science fiction ever since their prediction. Many sci-fi books, movies, and television shows use black holes as a method of travel (see the Potential Future Exploration section above) or as a threat to a space-going vessel. In at least one season of the show ''Star Trek: the Next Generation'' by Gene Roddenberry, artificially created miniature black holes are used as power sources for spaceships and natural ones as incubators for the young of an alien race. Neither of these uses has much of a basis in reality, of course.

Contrary to popular myth, a black hole is not a cosmic vacuum cleaner. In other words, a one-solar-mass black hole is no better than any other one-solar-mass object (such as, for example, the Sun) at "sucking in" distant objects. However, a one-solar-mass black hole has the same amount of matter as any other one-solar-mass object but compressed into a much smaller space, making it impossible to move fast enough to leave a black hole once inside the event horizon. If all of the Earth's matter could be compressed down to a radius of one centimeter at the center of the Earth's present configuration, it would become a black hole, but gravity at normal distances would be unchanged. The Moon would still orbit the Earth, as would all artificial satellites (International Space Station, GPS satellites, communications satellites, etc.) If a spherical platform could be constructed at an altitude of 4000 miles above the black hole, we could walk around on it and not notice anything unusual. (But if you dropped a nickel through a hole in the platform, you would never see it again.)

The term "black hole" is also used as a metaphor for a place that it is hard to get out of, generally containing a high concentration of something unpleasant. Ex: "The inner city is a black hole of crime and drug use." The "Black Hole of Calcutta" long predates the celestial use of the term; it was a horrible underground prison in [[Calcutta]], India.

==Are Black Holes Falsifiable?==
''Things'' cannot be judged [[falsifiable]] or non-falsifiable. The concept of being falsifiable only applies to theories or hypotheses. One can't say the unicorns are falsifiable, but the hypothesis "there are no unicorns" is. The imagined experiment would consist of finding a unicorn. If one were found, the hypothesis would be refuted. None has ever been found, but that's not germane to the question of falsifiability. Similarly, the hypothesis "there are no black holes" is falsifiable. The test would be to find one. (Many have been found, perhaps the most notable being the ones involved in the discovery of [[gravitational waves]].)

==See also==
*[[Black hole firewall]]
==References==
{{reflist}}
==External links==
*[http://imagine.gsfc.nasa.gov/docs/science/know_l2/black_holes.html Black Holes]
*[http://cosmology.berkeley.edu/Education/BHfaq.html Black Holes (Frequently Asked Questions)]

{{Relativity}}
[[Category:Relativity]]
[[Category:Black hole]]