Earth in Space

1
Earth in Space

• Section 19.1

2
Earths Shape

• Considered to be ellipsoid
• Oblate spheroid
• Earth is wider
• than it is tall
• Bulges at equator,
• flattened at poles

3
Earths motions

• Rotation spinning on an axis
• - causes day and night

4
Earths 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 - sidereal 1-3 Globe
re-points to sun - synodic
5
Earths motions

• 2. solar (synodic) day 24 hours
• The time it takes Earth to rotate once with
  respect to the sun.
• (Suns Highest point in sky to
  the
• next highest point in sky).

6
Earths Motions

• Revolution movement around a fixed point (sun)

7
Earths 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)

8
Seasons on Earth

• Earths 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)

9
Vernal equinox March 20 or 21
Solstice the sun reaches the greatest distance
north or south of the equator
Summer solstice June 21 or 22 Longest day
Winter solstice Dec 21 or 22 Shortest day
Equinox- the sun is directly above the
equator. Equal daylight and night time hours all
over the world
Autumnal equinox Sept 22 or 23
10
Earths Motions

• Precession Earths wobble

11
Earths Orbit

• Law of universal gravitation every object in the
  universe attracts every other object.

Isaac Newton
12

• Attracts all objects towards each other.

13

• Depends on two factors

MASS
DISTANCE
The amount of matter (stuff) in an object
STRONGER
14
MASS
WEIGHT
VS

• The amount of matter (stuff) in an object
• Does not change

• Force ( a push or pull) of gravity on an object.
• Changes depending on where you are.

15
265 lbs
120 x 1.6
About 45 lbs
16
Earths Orbit

• Inertia the tendency of an object to resist
  change in motion
• Newtons 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

17
Earths Orbit
Inertial force
Newton concluded that 2 forces (inertia,
gravity) combine to keep Earth in orbit around
the sun
Gravitational force
Earths motion around the sun, Not as easy as I
thought