Earth’s Physical Geography

Chapter 2, Section 1

Our Planet, the Earth• The Earth, sun, planets, and stars are

all part of a galaxy, or family of stars.• What is the name of the galaxy we

live in?• The sun is the center of our galaxy.

Days and Nights• Sun 93 million miles away; provides

the Earth with light and heat• The Earth travels around the sun in

an oval-shape path called an orbit• It takes one year (365 days) for the

Earth to complete one revolution, a circular journey around the Earth

Days and Nights• Earth spins as it revolves around the

sun on its axis, an imaginary line running through the Earth between the North and South poles

• A complete turn takes 24 hours and is called a revolution

• As Earth rotates…– It is daytime on the side facing the sun– It is night on the side away from the sun

Seasons• Earth’s axis is on an angle• At certain times of the year, days are long

than nights• At other times, nights are longer than days• Earth’s orbit is at a tilt– The tilt causes a region to face toward the sun for

more hours than it faces away from the sun• Days are longer

– At other times, the region faces away from the sun for more hours than it faces toward the sun• Days are shorter

Seasons• Earth’s tilt and orbit cause changes

in temperature during the seasons• The warmth you feel at any time of

year depends on how directly the sunlight falls upon you

Latitudes

• In some places on Earth, the sun is directly overhead at particular days during the year

• On March 21 and September 23, the sun is directly above the Equator at 0 degrees latitude.– The days are almost exactly as long as

the nights– Spring and fall equinoxes

Latitudes• Tropic of Cancer 23 ½ degrees North of the

Equator– Sun shines directly above on June 21 or the 22nd

– First day of summer (summer solstice) in the Northern hemisphere

• Tropic of Capricorn 23 ½ degrees South of the Equator– Sun shines directly above on December 21 or 22nd

– First day of winter (winter solstice) in the Northern hemisphere

• When would summer solstice occur in the Southern hemisphere?

Latitudes• The area between the Tropic of

Cancer and the Tropic of Capricorn is called the low latitudes, or the tropics.

• Any location in the low latitudes receives direct sunlight at some time during the year. HOT!

Latitudes• Two other distinct regions the Arctic

Circle 66 ½ degrees north of the Equator and the Antarctic Circle 66 ½ degrees south of the Equator

• The regions between these circles and the poles are high latitudes, or polar zones– Receive no direct sunlight… COLD!!

Latitudes• Middle latitudes, or the temperate

zones, receive fairly direct sunlight at some times, and at others fairly indirect sunlight

• Seasons occur here.– Each lasts about three months and has

distinct patterns of daylight, temperature, and weather