Observe: Motion of the Earth

Orbit

While the Earth is rotating, it is also orbiting the Sun. The Earth's orbit is elliptical (in the shape of an oval).

One full revolution around the Sun takes about 365 days. This is how we measure a single Earth year.

As Earth travels around its orbit of the Sun, the North and South poles point away from the Sun to varying degrees at various times of the year, producing the four seasons.

As we move around the Sun, the tilt of the Earth’s axis brings parts of Earth to face the Sun directly (summer). Or, the tilt angles the Earth away from the Sun (winter). Depending on where you are located on Earth, this tilt combined with the earth’s orbit explains the changing of the seasons.



  History Connection


Pixabay

"If I have seen further than others, it is by standing on the shoulders of giants." - Isaac Newton

Isaac Newton (1642-1726)


Isaac Newton first explained the effect of gravity of the Sun and Moon on our planet. Gravity is causing the Earth's axis to change. Because the Earth's axis is changing, each day has an extra 0.25 (25/100 or one-fourth) of a day.

Gregorian Calendar


Our Gregorian calendar (named after Pope Gregory XIII), is a solar calendar. To keep the calendar accurate, every four years we adjust by putting an extra day at the end of February. We call it a ‘leap year’.

  Video

Watch this video to learn more about day, night and seasons.

Question: How can we explain our observations of objects moving in the sky?

Resources