Earth’s Movement

Rotation Revolution

The spinning of an object around an axis.

Example:

- The Earth completes a full rotation in 24 hours

The movement of one 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 the Moon passes between the Sun and the Earth.

A lunar eclipse occurs when 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