Alignment
A line in a building or landscape that points to a place on the horizon where a sky body rises or sets.
Read moreGlossary
The language of the ancient sky
32 words you meet when you read about Chaco, the Maya and the Sun, from azimuth to zenith passage, each in one or two sentences.
A
Altitude
The height of a sky object above the horizon, in degrees. The Sun’s noon altitude is highest at the June solstice in the northern hemisphere.
Read moreArchaeoastronomy
The study of how people in the past understood and used the sky, combining archaeology and astronomy.
Read moreAzimuth
Direction along the horizon measured clockwise from true north: east is 90°, south 180°, west 270°.
Read moreC
Calendar Round
The 52-year cycle after which the same Haab’ and Tzolk’in date pair repeats in the Maya calendar.
Read moreCardinal directions
North, east, south and west. Several Chacoan walls follow north–south and east–west lines.
Read moreCenote
A natural limestone sinkhole holding groundwater. Maya cities in the Yucatán grew around them.
Read moreD
Declination
The Sun’s angle north or south of the celestial equator. It ranges from about +23.44° to −23.44° through the year.
Read moreDendrochronology
Tree-ring dating. It dates Chaco’s roof beams, and so its building phases, almost to the year.
Read moreE
E-Group
A Maya architectural complex of a western pyramid facing a long eastern platform, linked to sunrise observation.
Read moreEquinox
One of two days, around March 20 and September 22, when the Sun rises due east and sets due west.
Read moreG
Great house
A large, planned multi-storey stone building at Chaco, such as Pueblo Bonito or Chetro Ketl.
Read moreH
Horizon calendar
A method of telling the date by where the Sun rises against known landmarks on the skyline.
Read moreK
Kiva
A room, often round and partly underground, used by Pueblo peoples for gathering and ceremony.
Read moreL
Long Count
A Maya count of days from a fixed starting point, used for long historical dates.
Read moreLunar standstill
The extreme of the Moon’s rising range, repeating about every 18.6 years. The last major one peaked in 2024–25.
Read moreP
Petroglyph
An image pecked or carved into rock, like the spiral behind the Sun Dagger slabs.
Read moreR
Refraction
The bending of light in the atmosphere. It lifts the Sun near the horizon and makes daylight a few minutes longer.
Read moreS
Sacbe
A raised white Maya causeway. At Dzibilchaltún one leads to the Temple of the Seven Dolls.
Read moreSolstice
The two days, around June 21 and December 21, when the Sun reaches its northernmost or southernmost rising point.
Read moreSpace weather
Conditions in space driven by the Sun that can affect satellites, radio and power grids.
Read moreSun Dagger
The blades of light that cross a spiral petroglyph on Fajada Butte at the solstices and equinoxes.
Read moreSynodic period
The time for a planet to return to the same position relative to the Sun as seen from Earth: about 584 days for Venus.
Read moreT
W
Z
Zenith passage
A day when the noon Sun stands straight overhead. It happens twice a year between the tropics.
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See the sky the way they did
Open a viewer, pick a date and watch the sunrise point move along a real horizon. Then download the guides and take them outside.