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Definintion of science
1. Systematic study of the world
2. A way of knowing about the physical world
Characteristics of science
- empirical data
- provisional explanation
- specific to general
Siderdal day
360 rotation of the earth
Solar day
day measured from the sun
Differences between siderdal day and solar day
- earth is always orbiting the sun
- solar day is longer than siderdal day (1/365th)
- earth rotates one degree in a siderdal day
Celestial sphere
crystal that embeds the stars
celestial equator
great circle that lies between north and south of celestial poles
Celestial horizon
great circle that divides visible stars from non visible stars
Celestial meridian
divides east and west runs north south through observers zenith
Three ways to locate stars
- constellations
- declination
- azimath and altitude
Declination
angle between point on celestial sphere and equator.
Altitude
- angle above horizon
- always less than 90 degrees
Sideral period
moons 360 degree rotation around the earth in 27.3 days
Synodic period
repeat set of moon phases in 29.5 days
Cause of moon phases
- position of moon earth and sun
- we can only see a portion of the moon when lit
Solar eclipse
- sun's light is blacked by the moon
- need a new moon and ecliptic
Lunar eclipse
- sun's light on moon is blocked by earth
- need a full moon and ecliptic
Eratoshenes
discovered the earth was a circle
Retrograde motion
planets moving from east to west ; Mars, Jupiter, Saturn
Great astronomers
- Aristorchus (sun centered)
- Aristotle (earth centered)
- Hipparahus (invented epicycles)
- Ptolemy (used epicycles)
- Copernicus (heliocentric model; retrograde motion at opposition)
- Brahe (produced accurate data)
- Kepler
- Galileo
- Newton
Kepler laws
- planets move in elliptical with sun at focus
- line joining sun and planet sweeps out equal areas in equal time
- sideral period squared=cube of distance to sun
Galileo
- found sun spots
- saw Venus phases
- moons orbiting Jupiter
Newton's law of motion
- body at rest will go in straight line
- rate of change of velocity=mass of body being accelerated
- force a exerts on force b; b exerts equal and opposite force on a
Newton's law of universal gravitation
- mass attracts other mass in the universe
- force of one mass exerts on another=mass of two bits and is inversely proportional to the distance between them
Author
pricera
ID
41074
Card Set
Astro test
Description
Basic Astronomy
Updated
2010-10-14T00:55:04Z
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