CHAPTER 2, SECTION 1 Our Planet, Earth

The Little Blue Planet Though our world seems big, we are just a small part of the Milky Way Galaxy. Our every day life on Earth is shaped by forces millions of miles away in space, such as the Sun. Though the sun is 93 million miles away from us, it supports all life on earth.

The Sun The sun is responsible for providing heat and light to Earth. It is what creates our calendar, determines our time zones, and creates seasonal weather. All of these things happen because we are in constant motion.

The Sun and The Year This sense of constant motion creates a way for us to measure time. The Earth is constantly rotating around the sun in an orbit, or path one body makes as it circles around another. It takes us 365 ¼ days, or one year, to complete this journey. To complete our orbit in that time, our planet is traveling through space at 66,000 miles per hour!

The Sun and A Day As we circle the sun, we are also spinning on an axis.  An axis is an imaginary line running through the Earth, from the North Pole to the South Pole. This rotation, which takes 24 hours, creates day and night.  As our side of the planet rotates towards the sun, we experience sunrise and daytime.  When it rotates away from the sun, the sun sets and night falls. To help us adjust to this as a planet, governments have created time zones – standard lines which divide up the Earth so that no matter where you live, your noon is the middle of the day when the sun is highest, while midnight is the middle of the night.

Time Zones

The Sun and Seasons The rotation of the Earth on its axis also causes the earth to have seasons. When the earth spins on its axis, it doesn’t spin perfectly straight. It tilts sideways on its axis, like a top. The Earth's Axis

The Sun and Seasons

In the spring and fall, the Earth’s axis is sideways, keeping the sun closest to the equator, giving us moderate temperatures. In summer, the Earth’s axis leans towards the earth, bringing the Northern hemisphere towards the sun. This gives us summer weather. In winter, the Earth’s axis leans away from the sun, bringing the Northern hemisphere away from the sun. This gives us winter weather.