Editing Inca Empire (section)

== Science and technology ==
=== Measures, calendrics and mathematics ===
{{Main|Mathematics of the Incas}}
[[File:Inca. Quipu.jpg|thumb|Quipu, 15th century. [[Brooklyn Museum]]]]

Physical measures used by the Inca were based on human body parts. Units included fingers, the distance from thumb to forefinger, palms, [[cubit]]s and wingspans. The most basic distance unit was ''thatkiy'' or ''thatki'' or one pace. The next largest unit was reported by Cobo to be the ''topo'' or ''tupu'', measuring 6,000 ''thatkiy''s, or about {{convert|7.7|km|1|abbr=on}}; careful study has shown that a range of {{convert|4.0|to|6.3|km|1|abbr=on}} is likely. Next was the ''wamani'', composed of 30 ''topo''s (roughly {{convert|232|km||disp=or|abbr=on}}). To measure area, 25 by 50 wingspans were used, reckoned in ''topo''s (roughly {{convert|3280|km2||disp=or|abbr=on}}). It seems likely that distance was often interpreted as one day's walk; the distance between ''tambo'' way-stations varies widely in terms of distance, but far less in terms of time to walk that distance.{{sfn|D'Altroy|2014|pp=246–247}}{{sfn|McEwan|2008|pp=179–180}}

Inca [[calendar]]s were strongly tied to [[astronomy]]. Inca astronomers understood [[equinox]]es, [[solstice]]s and [[zenith]] passages, along with the [[Transit of Venus|Venus cycle]]. They could not, however, predict [[eclipse]]s. The Inca calendar was essentially [[lunisolar]], as two calendars were maintained in parallel, one [[solar calendar|solar]] and one [[lunar calendar|lunar]]. As 12 lunar months fall 11 days short of a full 365-day solar year, those in charge of the calendar had to adjust every winter solstice. Each lunar month was marked with festivals and rituals.{{sfn|D'Altroy|2014|pp=150–154}} Apparently, the days of the week were not named and days were not grouped into weeks. Similarly, months were not grouped into seasons. Time during a day was not measured in hours or minutes, but in terms of how far the sun had travelled or in how long it had taken to perform a task.{{sfn|McEwan|2008|pp=185–187}}

The sophistication of Inca administration, calendrics and engineering required facility with numbers. Numerical information was stored in the knots of ''[[quipu]]'' strings, allowing for compact storage of large numbers.<ref name="NYT-20160102">{{cite news |last=Neuman |first=William |title=Untangling an Accounting Tool and an Ancient Incan Mystery |url=https://www.nytimes.com/2016/01/03/world/americas/untangling-an-accounting-tool-and-an-ancient-incan-mystery.html |archive-url=https://ghostarchive.org/archive/20220103/https://www.nytimes.com/2016/01/03/world/americas/untangling-an-accounting-tool-and-an-ancient-incan-mystery.html |archive-date=3 January 2022 |url-access=subscription |url-status=live |date=2 January 2016 |publisher=[[The New York Times]] |access-date=2 January 2016}}{{cbignore}}</ref>{{sfn|McEwan|2008|pp=183–185}} These numbers were stored in [[base-10]] digits, the same base used by the Quechua language<ref>{{cite web |url=http://www.arch.cam.ac.uk/~pah1003/loe/Eng/SupplInfo/2008Heggarty.htm |title=Supplementary Information for: Heggarty 2008 |website=arch.cam.ac.uk |access-date=24 September 2012 |url-status=dead |archive-url=https://web.archive.org/web/20130312203340/http://www.arch.cam.ac.uk/~pah1003/loe/Eng/SupplInfo/2008Heggarty.htm |archive-date=12 March 2013}}</ref> and in administrative and military units.{{sfn|D'Altroy|2014|pp=233–234}} These numbers, stored in ''quipu'', could be calculated on ''[[yupana]]s'', grids with squares of positionally varying mathematical values, perhaps functioning as an [[abacus]].<ref>{{cite web |url=http://www-history.mcs.st-and.ac.uk/HistTopics/Inca_mathematics.html |title=Inca mathematics |website=history.mcs.st-and.ac.uk |access-date=24 September 2012}}</ref> Calculation was facilitated by moving piles of tokens, seeds or pebbles between compartments of the ''yupana''. It is likely that Inca mathematics at least allowed division of integers into integers or fractions and multiplication of integers and fractions.{{sfn|McEwan|2008|p=185}}

According to mid-17th-century Jesuit chronicler Bernabé Cobo,<ref>Cobo, B., (1983 [1653]), Obras del P. Bernabé Cobo, Vol. 1, Edited and preliminary study By Francisco Mateos, Biblioteca de Autores Españoles, vol. 91, Madrid, Ediciones Atlas.</ref> the Inca designated officials to perform accounting-related tasks. These officials were called quipo camayos. Study of khipu sample VA 42527 (Museum für Völkerkunde, Berlin)<ref>{{cite journal |last=Sáez-Rodríguez |first=A. |date=2012 |title=An Ethnomathematics Exercise for Analyzing a Khipu Sample from Pachacamac (Perú) |journal=Revista Latinoamericana de Etnomatemática |volume=5 |issue=1 |pages=62–88 |url=http://www.revista.etnomatematica.org/index.php/RLE/article/view/37}}</ref> revealed that the numbers arranged in calendrically significant patterns were used for agricultural purposes in the "farm account books" kept by the khipukamayuq (accountant or warehouse keeper) to facilitate the closing of accounting books.<ref>{{cite journal |last=Sáez-Rodríguez |first=A. |date=2013 |title=Knot numbers used as labels for identifying subject matter of a khipu |journal=Revista Latinoamericana de Etnomatemática |volume=6 |issue=1 |pages=4–19 |url=http://www.revista.etnomatematica.org/index.php/RLE/article/view/52}}</ref>

=== Communication and medicine ===
The Inca recorded information on assemblages of knotted strings, known as [[quipu]], although they can no longer be decoded. Originally, it was thought that Quipu were used only as mnemonic devices or to record numerical data. Quipus are also believed to record history and literature.{{sfn|McEwan|2008|p=183}}

The Inca made many discoveries in medicine.<ref>{{cite book |last1=Somervill |first1=Barbara A. |title=Empire of the Inca |date=2005 |publisher=[[Infobase|Facts on File]] |isbn=0-8160-5560-2 |pages=101–103 |url=https://archive.org/details/empireofinca0000some/page/101}}</ref> They performed successful [[Trepanation|skull surgery]], by cutting holes in the skull to alleviate fluid buildup and inflammation caused by head wounds. Many skull surgeries performed by Inca surgeons were successful. Survival rates were 80–90%, compared to about 30% before Inca times.<ref>{{cite web |url=http://www.sciencenews.org/view/generic/id/31466/title/Incan_skull_surgery |title=Incan skull surgery |publisher=[[Science News]] |access-date=25 September 2009 |archive-date=13 May 2012 |archive-url=https://web.archive.org/web/20120513193734/http://www.sciencenews.org/view/generic/id/31466/title/Incan_skull_surgery |url-status=dead}}</ref> According to chronicler Bernabé Cobo, they also had a deep knowledge of herbalism, and the Spanish soldiers trusted the hands of an indigenous surgeon more than one of the [[Barber surgeon|barbers]] who accompanied them.

=== Weapons, armor and warfare ===
{{Main|Inca army}}
[[File:Sacsayhuaman - 51188929520.jpg|thumb|left|[[Sacsayhuamán]], the largest Inca ''[[pukara]]'' (fortresses)]]
[[File:Cabezas de Bronce.jpg|thumb|upright|[[Copper]] heads for maces]]

The Inca army was the most powerful at that time, because any ordinary villager or farmer could be recruited as a soldier as part of the ''[[mit'a]]'' system of mandatory public service. Every able bodied male Inca of fighting age had to take part in war in some capacity at least once and to prepare for warfare again when needed. By the time the empire reached its largest size, every section of the empire contributed in setting up an army for war.

The Incas had no iron or steel and their weapons were not much more effective than those of their opponents so they often defeated opponents by sheer force of numbers, or else by persuading them to surrender beforehand by offering generous terms.<ref name="AHE"/> Inca weaponry included "hardwood spears launched using [[Spear-thrower|throwers]], arrows, javelins, slings, the [[bolas]], clubs, and maces with star-shaped heads made of copper or bronze".<ref name=AHE>{{Cite web |url=https://www.worldhistory.org/Inca_Warfare/ |title=Inca Warfare |last=Cartwright |first=Mark |date=19 May 2016 |website=[[World History Encyclopedia]]}}</ref><ref name="MacQuarrie2008">{{cite book |author=Kim MacQuarrie |title=The Last Days of the Incas |url=https://books.google.com/books?id=Emql_kU0QLIC&pg=PA144 |date=17 June 2008 |publisher=Simon and Schuster |isbn=978-0-7432-6050-3 |page=144}}</ref> Rolling rocks downhill onto the enemy was a common strategy, taking advantage of the hilly terrain.<ref name="Parker2008">{{cite book |author=Geoffrey Parker |title=The Cambridge Illustrated History of Warfare: The Triumph of the West |url=https://books.google.com/books?id=yqNj5BlEMtcC&pg=PA136 |date=29 September 2008 |publisher=[[Cambridge University Press]] |isbn=978-0-521-73806-4 |page=136}}</ref> Fighting was sometimes accompanied by drums and trumpets made of wood, shell or bone.<ref name="Stevenson1968">{{cite book |author=Robert Stevenson |title=Music in Aztec & Inca Territory |url=https://books.google.com/books?id=b2Gk32Zn2tgC&pg=PA77 |date=1 January 1968 |publisher=[[University of California Press]] |isbn=978-0-520-03169-2 |page=77}}</ref><ref name="CoboHamilton1990">{{cite book |author1=Father Bernabe Cobo |author2=Roland Hamilton |title=Inca Religion and Customs |url=https://archive.org/details/incareligioncust0000cobo |url-access=registration |date=1 May 1990 |publisher=[[University of Texas Press]] |isbn=978-0-292-73861-4 |page=218}}</ref> Armor included:<ref name="AHE"/><ref name="Burland1968">{{cite book |author=Cottie Arthur Burland |title=Peru Under the Incas |url=https://archive.org/details/peruunderincas00burl |url-access=registration |date=1968 |publisher=Putnam |page=101 |quote=The sling was the most deadly projectile weapon. Spear, long-handled axe and bronze-headed mace were the effective weapons. Protection was afforded by a wooden helmet covered with bronze, long quilted tunic and flexible quilted shield.}}</ref>
* Helmets made of wood, cane, or animal skin, often lined with copper or bronze; some were adorned with feathers
* Round or square shields made from wood or hide
* Cloth tunics padded with cotton and small wooden planks to protect the spine
* Ceremonial metal breastplates of copper, silver, and gold have been found in burial sites, some of which may have also been used in battle.<ref name="SiversDesnoyers2012">{{cite book |author1=Peter Von Sivers |author2=Charles Desnoyers |author3=George B. Stow |title=Patterns of World History |url=https://books.google.com/books?id=ttZL_B_qcPEC&q=copper+breastplates |date=2012 |publisher=[[Oxford University Press]] |isbn=978-0-19-533334-3 |page=505}}</ref><ref>{{cite journal |last1=Maestro |first1=Carmen Pérez |title=Armas de metal en el Perú prehispánico |journal=Espacio, Tiempo y Forma, Señe I, Prehistoria y Arqueología |date=1999 |pages=319–346 |url=http://revistas.uned.es/index.php/ETFI/article/download/4689/4528 |language=es |access-date=1 July 2019 |archive-date=1 July 2019 |archive-url=https://web.archive.org/web/20190701142707/http://revistas.uned.es/index.php/ETFI/article/download/4689/4528 |url-status=dead }}</ref>

Roads allowed quick movement (on foot) for the Inca army. Shelters called ''[[Tambo (Incan structure)|tambo]]'' and storage silos called [[qullqa]]s were built one day's travelling distance from each other, so an army on campaign could be fed and rested. This can be seen in names of ruins such as [[Ollantaytambo]] or "the storehouse of Ollantay". These were set up so the Inca and his entourage would always have supplies (and possibly shelter) ready as they traveled.