Unit 3 Flashcards
(26 cards)
lines of longitude
great circles that pass through both the north and south poles
meridian
great circles that pass through both the north and south poles
parallels
circles in planes parallel to the equator define north-south measurements
lines of latitude
circles in planes parallel to the equator define north-south measurements
rotation
an object’s spinning motion about its own axis
revolution
an object’s orbital motion around another object
precession
the slow movement of the axis of a spinning body around another axis due to a torque (such as gravitational influence) acting to change the direction of the first axis. It is seen in the circle slowly traced out by the pole of a spinning gyroscope
nutation
a periodic oscillation of the earth’s axis that causes the precession of the poles to follow a wavy rather than a circular path.
sidereal day
the time required for one complete rotation of the earth in reference to a star; 23 hours, 56 minutes, and 4.09 seconds
solar day
time required for the earth to complete one revolution around its axis compared to the sun
celestial sphere
fictitious sphere centered on the Earth upon which all celestial bodies can be projected
right ascension
celestial equivalent of longitude; the angular distance of a point celestial sphere, measured east together with declination, define the position of an object in the sky. Measured in hours (max. 24 hours), minutes (max 60 min), seconds (max 60 sec)
declination
angular distance north or south from the equatorial plane of the earth measured toward the poles; together with right ascension, define the position of an object in the sky. Measured in degrees
zenith
point on the celestial sphere directly overhead for an observer
nadir
the direction opposite the zenith
ecliptic plane
the plane in which the Earth orbits the sun, 23.4° from the celestial equator
equinox
times at which the center of the Sun is directly above the equator, marking the beginning of spring and autumn
hour angle
the distance in hours, minutes, and seconds westward along the celestial equator from the observer’s meridian to the object’s RA
troposphere
starts at the Earth’s surface and extends 8 to 14.5 kilometers high (5 to 9 miles). This part of the atmosphere is the most dense. Almost all weather is in this region
stratosphere
starts just above the troposphere and extends to 50 kilometers (31 miles) high. The ozone layer, which absorbs and scatters the solar ultraviolet radiation, is in this layer
mesosphere
starts just above the stratosphere and extends to 85 kilometers (53 miles) high. Meteors burn up in this layer
thermosphere
starts just above the mesosphere and extends to 600 kilometers (372 miles) high. Aurora and satellites occur in this layer
ionosphere
an abundant layer of electrons and ionized atoms and molecules that stretches from about 48 kilometers (30 miles) above the surface to the edge of space at about 965 km (600 mi), overlapping into the mesosphere and thermosphere. This dynamic region grows and shrinks based on solar conditions and divides further into the sub-regions: D, E and F; based on what wavelength of solar radiation is absorbed. The ionosphere is a critical link in the chain of Sun-Earth interactions. This region is what makes radio communications possible
exosphere
upper limit of our atmosphere. It extends from the top of the thermosphere up to 10,000 km (6,200 mi
