earth in space section 19.1. earth’s shape considered to be ellipsoid oblate spheroid earth is...
TRANSCRIPT
Earth’s Shape
• Considered to be ellipsoid
Oblate spheroid
• Earth is wider
than it is tall
• Bulges at equator,
flattened at poles
Earth’s Motions
1. sidereal day The time it takes the Earth
to
rotate once with respect to a
reference star.• One 360° Rotation• Time = 23 hr. 56 min.
1-2: Globe rotates 360° - sidereal1-3: Globe re-points to sun - synodic
Earth’s motions
2. solar (synodic) day = 24 hours
The time it takes Earth to rotate once with respect to the sun.
(Sun’s Highest point in sky to the
next highest point in sky).
Earth’s Motions
- Revolves once every 365.25 days (year)
need leap years
- elliptical shaped orbit
- Jan. 3 - 147 million km from sun (perihelion)
- July 4 - 152 million km from sun (aphelion)
Seasons on Earth
• Earth’s axis is tilted 23.5o
• The area tilted towards sun has longer days and more radiant energy (summer)
• The area tilted away from
the sun has shorter days
and less radiant energy (winter)
Winter solsticeDec 21 or 22Shortest day
Summer solsticeJune 21 or 22Longest day
Vernal equinoxMarch 20 or 21
Autumnal equinoxSept 22 or 23
Solstice – the sun reaches the greatest distance north or south of the equator
Equinox- the sunis directly abovethe equator.Equal daylight and night time hours all over the world
• Law of universal gravitation: every object in the universe attracts every other object.
Earth’s Orbit
Isaac Newton
MASS
• The amount of The amount of matter (stuff) matter (stuff) in an objectin an object
• Does not Does not changechange
WEIGHT
• Force ( a push Force ( a push or pull) of or pull) of gravity on an gravity on an object.object.
• Changes Changes depending on depending on where you are.where you are.
VS
Earth’s Orbit• Inertia – the tendency of an object to resist
change in motion
• Newton’s first law of motion
• An object in motion will stay in motion, in straight line, at a constant speed unless acted upon by an outside force
Earth’s Orbit
Inertial force
Gravitationalforce
Newton concluded that
2 forces (inertia, gravity) combine to keep
Earth in orbit around the sun
Earth’s motion around the sun,Not as easy as I thought