SVSU PHYS 106C Keen Chp 2

Rotation

the spin of an object around an internal axis

Horizon

the horizontal circle defining the lower edge of the sky

altitude

the angular distance from a point on the sky to the point on the horizon directly below it

latitude

a measure of location specifying north-south position on earth running from 0 degrees to the equator @ 90 degrees north & 90 degrees south

Longtitude

a measure of location specifying east-west position on earth

angular size

angular distance measured on a sphere in degrees, minutes, arcminutes, and arcseconds

celestial sphere

an imaginary transparent sphere surrounding earth, on which positions of the stars, planets, and other celestial bodies are projected from extensions of earth's coordinate system

celestial equator

the extension of earth's equator onto the celestial sphere

Polaris

the star that is found very near earth's celestial pole

north celestial pole

the extension of earth's north pole on the celestial sphere

south celestial pole

the extension of earth's south pole on the celestial sphere

zenith

the point on the sky directly overhead from the observer

meridian

a circular arc crossing the celestial sphere and passing through the local zenith and celestial pole

declination

the position of an object on the celestial sphere, measured similarly to the latitude on earth

sidereal day

the time taken by the earth to rotate on its axis relative to the stars

solar day

the time between successive crossings of the same meridian on the sky by the sun

small angle formula

a mathematical relationship between the angular size of an object, as measured on the sky, and the object's distance and physical size

analemma

the figure-8 pattern formed by charting the daily position of the sun @ the same time of the day over the course of 1 year

summer solstice

the day (june 21st) with the most hours of sunlight, when the sun appears highest in the sky

winter solstice

the day (december 21st) with the fewest hours of daylight, when the sun appears lowest in the sky

equinox

A day when the hours of daylight and darkness are equal

orbit

the cyclical path in space that one object makes around another object

axial tilt or obliquity

the angle between a planet's rotation axis and a line perpendicular to the planet's orbital plane

precession

the rotation of a planet's spin axis, similar to that of a wobbling toy

constellations

a group of stars that form a pattern, and the designated region of the sky surrounding them

circumpolar constellation

a constellation that, from the viewer's perspective, never rises or sets.

ecliptic

the path that the sun appears to follow against the background as defined by earth's orbit around the sun

zodiac

13 constellations that lie close to the plane of the ecliptic

phase (of the moon)

as seen by observation of the earth, the appearance of the illuminated portion of the moon, which change cyclically so the moon orbits the earth

scientific model

an idea or set of ideas used to create testable explanations

New moon

moon is between earth and the sun
lunar face illuminated points away from the earth

waxing crescent

appears in the late afternoon sky as sun sinks in the west

first quarter moon

moon at its highest altitude @ sunset
occurs seven days after new moon

waxing gibbous

after first quarter

full moon

the time when the Moon is fully illuminated
7 days after first quarter
highest point in the night sky @ 12

waning gibbous

appears on eastern horizon closer to midnight

third quarter

7 days after full moon
rises @ midnight

waning crescent

last phase before it starts back over

synodic month

the amount of time it takes the moon to cycle through its phases (29.5 days)

sidereal month

the amount of time it takes the moon to make a complete orbit

Eclipse

the passing of one celestial body through the shadow of another

penumbra

the outer region of a shadow cast by an extended object

umbra

the inner region of a shadow cast by an extended object

Total lunar eclipse

an eclipse that occurs when the moon passes through Earth's umbral shadow

partial lunar eclipse

an eclipse that occurs when the moon passes partially through the earth's umbral shadow

total solar eclipse

an eclipse that occurs when a region of earth's surface passes under the moon's umbral shadow and the sun disk is fully blocked

totality

the moment or duration of total concealment of the sun or moon during an eclipse

apogee

the distance of farthest approach of an object orbiting earth

perigee

the distance of closest approach of an object orbiting earth

aphelion

the distance of farthest approach of an object orbiting the sun

perihelion

the distance of closest approach of an object orbiting the sun

annular eclipse

a solar eclipse that occurs when the positions of the moon and sun are such that the lunar disk does not fully block out the solar disk

partial solar eclipse

an eclipse that occurs when a region of earth's surface passes under the moon's penumbral shadow

line of nods

the line defined by the intersection of the moon's orbital plane and earth's orbital plane around the sun.

mythology

a collection of stories used to explain phenomena whose physical basis is not understood

megalith

a large stone used as a monument or part of a monument

paleolithic period

the period extending from 2.6 million years to 10,000 years ago (earliest known use of stone tools)

neolithic period

the period extending from 10,000 BCE to between 4500 and 2000 BCE, when farming was introduced

geocentric model

a model stating that earth is the body around which all other solar system objects orbit

heliocentric model

a model stating that the Sun is the body around which all other solar system objects orbit

parallax

a displacement or difference in the apparent position of an object viewed along two different lines of sight