Download Chapter 1 - Humble ISD

Chapter 1: Charting the heavens
1.1 Our Place in Space
1.3 The “Obvious” View
1.4 Earth’s Orbital Motion
1.5 Motion of the Moon
1.6 The Measurement of
Distance
1.1 Our Place in Space
• Earth is __________________________—we don’t occupy any _________________________________
• Universe: _______________________________ all space, time, matter, and energy
• Astronomy: _________________________________________
• Scales are very large: measure in ______________________________, the distance light travels in a year—
about ___________________________________
• In one nanosecond, or 10-9 of a second, light travels ______________________ inches.
• In one microsecond, or 10-6 of a second, light travels ________________ feet.
• In one millisecond, or 10-3 of a second, light travels _____________________ miles.
• In one second, light travels _________________________ miles.
1.3 The “Obvious” View
• Simplest observation: _____________________________________________________
• About ______________________________ stars visible at any one time; distributed randomly but human
brain tends to find _____________________________________________
• Group stars into _________________________: Figures having meaning to those doing the grouping
• Useful: ______________________________, which is _______________________________________
• Useless: Astrology, which makes ________________________________________________________________________
based on the star patterns at their birth
• Stars that ________________________________________ in the sky may not actually be_________________________
• The celestial sphere: Stars _________________________________________________________________________ of a
sphere surrounding the Earth
• They aren’t, but can use two-dimensional spherical coordinates (similar to _________________________
________________________________________) to locate sky objects
More Precisely 1-1: Angular Measure
• Full circle contains __________________ (degrees)
• Each degree contains ___________ (arc-minutes)
• Each arc-minute contains ______________________ (arc-seconds)
• Angular size of an object depends on its ________________________________________
1.4 Earth’s Orbital Motion
• Daily cycle, noon to noon, is ____________________________ motion —________________________
• Stars aren’t in quite the same place__________________________ hours later, though, due to Earth’s
rotation around Sun; when they are once again in the same place, ____________________________ has
passed
• Seasonal changes to night sky are due to _______________________________
• Twelve constellations Sun moves through during the year are called the _________________________;
path is ___________________________
• Ecliptic is plane of Earth’s path around Sun; at ____________________________ to ___________________________
• Northernmost point of path (above celestial equator) is ____________________________; southernmost is
_____________________; points where path crosses celestial equator are
_________________________________________
• Combination of _______________________________________________ gives seasons
• Time from one vernal equinox to next is __________________________________________
• ___________________________: rotation of Earth’s axis itself; makes one complete circle in about
______________________________________
•
•
Time for Earth to orbit once around Sun, relative to fixed stars, is ______________________________
______________________ follows seasons; ________________________________ follows constellations—in
_____________________________________________ will still be summer, but _________________________ will be a
summer constellation
1.5 Motion of the Moon
• Moon takes about _________________ days to go through whole cycle of phases—_________________________
• Phases are due to different amounts of ________________________ being visible from Earth
• Time to make full ________________________ around Earth, sidereal month, is about _____________ shorter
• Eclipses occur when Earth, Moon, and Sun form a ______________________
• Lunar eclipse:
• Earth is between __________________________
• Partial when only part of Moon is in shadow
• Total when it all is in shadow
• Solar eclipse: Moon is between ________________________
• Partial when only part of Sun is blocked
• Total when it all is blocked
• Annular when Moon is too far from Earth for total
• Eclipses don’t occur every month because Earth’s and Moon’s orbits are ________________________
______________________________________
1.6 The Measurement of Distance
• Triangulation: _______________________________________________________________________________________
• ______________________________________________ Similar to triangulation, but look at apparent motion
of object against distant background from two vantage points
• Measuring Earth’s radius:
• Done by _______________________________________ about 2300 years ago; noticed that when
Sun was directly overhead in one city, it was at an angle in another.
• Measuring that angle and the distance _______________________________________________________.