THE SEASONS:

The tilt of the Earth’s

Axis, Reflection, and

absorption

WHY DO WE HAVE

SEASONS?

• TRUE OR FALSE:

– Because the Earth is closer to the sun in

summer than in winter.

ANSWER:

FALSE!!! The Earth is actually approx.

3% closer to the sun in January than it

is in July!!! (don’t feel bad – ¾ of

Harvard grads got this wrong (on

camera!)

KEY FACT: • THE EARTH’S AXIS IS TILTED 23.5O TOWARDS THE NORTH

STAR*, BUT NOT ALWAYS TOWARDS THE SUN:

-SOMETIMES IT’S TILTED TOWARDS THE SUN (SUMMER)

-SOMETIMES IT’S TILTED AWAY FROM THE SUN (WINTER)

-SOMETIMES IT’S TILT IS “IN BETWEEN” TOWARDS AND AWAY

(SPRING AND FALL)

The angle of sunlight: direct or not? This

makes all the difference!

SUMMER: a closer view…

Sunlight hits the

Earth’s surface at a

DIRECT angle, so the

energy is

CONCENTRATED,

causing WARMER

TEMPERATURES

WINTER: a closer view…

Sunlight hits the

Earth’s surface at an

INDIRECT angle, so

the energy is NOT

CONCENTRATED,

causing COOLER

TEMPERATURES

Concentration of rays

determines temperature

SPRING AND FALL:

a closer view…

This causes the Energy to reach

the ground “SOMEWHAT

CONCENTRATED” (more than

in winter, less concentrated

than in summer)

sun

TROPICS/EQUATOR – ALWAYS MOSTLY DIRECT = HOT;

ARCTIC CIRCLES/POLES – ALWAYS MOSTLY INDIRECT = COLD;

MIDDLE LATITUDES – BETWEEN CIRCLES AND TROPICS – VARY

BY SEASON

Click here for a simulation that

shows it all in motion!