Transcript SNC1D0 Motions of the Earth and the Moon

MOTIONS OF THE EARTH, THE
MOON, AND PLANETS
Earth’s Movement
Rotation
Revolution
 The spinning of an object
 The movement of one
around an axis.
Example:
- The Earth completes a full
rotation in 24 hours
object around another (aka
orbit)
Example:
- The Earth completes a full
revolution around the Sun
in ~ 365 days.
Orbital Radius and Eccentricity
 Planets and other celestial objects rarely follow
perfect circular paths .
 The orbital radius refers to the average distance
between the Sun and the celestial object of
interest
Orbital Radius and Eccentricity
 Highly oval, or elliptical, orbits are called
eccentric orbits
Motions of the Moon
 The Moon exhibits synchronous rotation
 Its rotational period is the same as its revolution.
 This means the same side of the Moon is always
facing Earth
Phases of the Moon
 The Moon reflects the Sun’s light as the Earth
revolves around the Sun and the Moon
revolves around the Earth.
MOON
MOON
Eclipses
Solar Eclipse
Lunar Eclipse
 A solar eclipse occurs when
 A lunar eclipse occurs when
the Moon passes between
the Sun and the Earth.
the Earth passes between
the Sun and the Moon
Force of Gravity
 A natural phenomenon by which physical
bodies attract with a force proportional to
their mass.
The Moon’s Influence on Earth’s Tides
 The Moon’s gravity pulls Earth and its oceans
toward it.
 This causes a bulge of water to form on the
side of the Earth facing the Moon.
How Do We Know What We Know?
 Claudius Ptolemy (87-150 BCE)
 Roman citizen living in Egypt
 Mathematician, Astronomer, Geographer,
Astrologer and Poet
 Created the Geocentric Model of the Solar System
 The Earth is the center of the Solar System
How Do We Know What We Know?
 Nicholas Copernicus (1473-1543)
 Renaissance Astronomer from Poland
 Created the Heliocentric Model of the Solar
System but kept his views to himself and close
friends.
 The Sun is at the center of the Solar System
How Do We Know What We Know?
 Galileo Galilei (1564-1642)
 Italian physicist,
mathematician, astronomer,
and philosopher
 “The Father of Modern
Physics”
 Found support for the
Heliocentric Model of the
Solar System and defended
the Copernican view of the
Solar System.
Earth’s Tilt and the Seasons
 The Earth rotates at a 23.5ᵒ angle from the
Earth-Sun orbital plane.
 This tilt is the cause of seasons.
Seasons in the Northern Hemisphere
 When the Earth is tilted towards the Sun,
North America experiences summer.
Seasons in the Northern Hemisphere
 When the Earth is tilted away from the Sun,
North American experiences winter.
Seasons in the Northern Hemisphere
 When the Earth isn’t tilted towards, or away
from, the Sun, North America experiences
Autumn and Spring.
Solstices and Equinoxes in
the Northern Hemisphere
 Summer Solstice: longest day (June 21st)
 Winter Solstice: shortest day (December 21st)
 Vernal Equinox: first day of Spring with
12hour days and 12 hour nights (March 21st)
 Autumnal Equinox: first day of Autumn with
12 hour days and 12 hour nights (September
21st)
Precession: Earth’s Wobble
 The Earth spins
around an axis that
wobbles like a slow
spinning top.
 This wobble takes 26
000 years to
complete.
 Currently, the North
Star is Polaris. In 12
000 years the new
“North Star” will be
the star Vega.
Homework
 Finish P. 328 Q: 1-14
 Read 8.6 in preparation for tomorrow’s class