# Seasons on Earth Butler Middle School 8th Grade Science

## Presentation on theme: "Seasons on Earth Butler Middle School 8th Grade Science"— Presentation transcript:

Seasons on Earth Butler Middle School 8th Grade Science
Bob, Paul, Ms Adams, Oct 25, 2012

The Observed Data: 4 Seasons
Autumn or Fall Winter Spring Summer imgres

We can explain the 4 seasons using Models of the Earth and Sun

Scientific Model Representation of an object for study and understanding (very common in Science) Models can be physical and/or conceptual Model leg in 7th grade life science Computer model of a large weather system

Spherical Earth Model Equator Earth rotates on N-S axis once per day

Earth-Sun Model (evolved over 100’s maybe 1000‘s of years)
Earth revolves around the sun once per year + a little bit

Earth’s Orbital Plane to Polaris perpendicular to orbital plane
Points to Polaris (North Star) to Polaris orbital plane perpendicular to orbital plane 7

Rotate and Revolve Rotation: spinning like a top Earth rotates on its axis once per 24hr Causes day & night Revolution: 1 object moving around a 2nd object Earth revolves around sun once per year: days + 1/4 day Leap Year Every 4 years February has an extra day 4 years = ( ) = 1461 days

Comparing Diameters Earth Sun
Sun ≈ 109 x Earth

Sun illuminates Earth The Sun is a huge ball of fire - sends energy (light & heat) to the earth - 1/2 of earth is always illuminated - day - 1/2 of earth is always in the dark - night

Energy distribution from Sun
slanted hit large area (cooler) U direct hit small area (warmer) N

Energy distribution from Sun

Understanding the Seasons
It’s all in the tilt Summer: - Earth is tilted toward the sun, we get a more direct hit, so it’s warmer Winter: Earth is tilted away from the sun, we get a slanted hit, so it’s cooler No tilt means 1 Season!

Understanding Summer and Winter
Summer in the North Winter in the North S U night day N South South From summer to winter earth revolves half-way around Sun

Special Days Vernal Equinox March 20 Winter Solstice Dec 21 Summer
June 21 Autumnal Equinox Sept 22 Vernal Equinox March 20

Earth Sun Model