Transcript SES4U Motions of the Earth

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.
 The Moon’s orbit is eccentric and therefore
experiences apogee (furthest point from
Earth) and perigee (closest point to Earth)
Perigee
Apogee
362 570 km
405 410 km
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?
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?
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?
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.