Planetary Cycles

Our universe has many cycles. Our galaxy, the Milky Way, turns like a wheel, and all the stars within it revolve around its center. Our solar system moves within this galaxy. The sun spins on its axis once every 24 days and 16 hours. The planets turn on their axis and orbit the sun. Moons orbit their planets.

It took a long time for humans to understand about our planet and its cycles. Humans used to think that the earth was a huge plate that rested on the back of four elephants standing on a giant floating turtle. Or they believed that one of the gods carried the earth on this shoulders.

We now know that the cycles of our planet earth, our moon, and the sun all affect life on earth.

Sample some of the following activities to learn more about planetary cycles.


Places To Go    People To See    Things To Do    Teacher Resources    Bibliography

Places To Go

The following are places to go (some real and some virtual) to find out about planetary cycles.

Cycles of the Earth System
Learn about how the Earth is always changing and how mankind's activities affect that change.
Bay of Fundy
Visit the Bay of Fundy on the Canadian Atlantic coast near Nova Scotia. It has the highest tide changes in the world.
Exploring the Planets
Visit the planets of our solar system and compare their atmospheres, their surfaces, and the processes by which they were formed.
NASA - Mercury
Mercury's years are short, and its days are long compared to the earth. Mercury travels around the sun in just under 88 earth days. Calculate what your age would be if you lived on Mercury. (A 10-year-old on earth would be 41 years old on Mercury).
National Air and Space Museum
Virtually walk through the National Air and Space Museum at the Smithsonian for planetary exhibits.

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People To See

Ask An Astronomer
Ask the astronomers at this site your questions about planetary cycles.
Ask Dr. Universe
Ask Dr. Universe how the moon affects the tides, how stars get their colors, and all your other planetary cycle questions. 
Ask the Space Scientist
Ask the Space Scientist your questions about planetary cycles. Browse through this site's excellent archive of past questions and answers.
Ferdinand Magellan
In 1522, when his remaining ship arrived back in Spain from the long voyage around the world, it proved that the earth is round. (Magellan, himself, didn't arrive back in Spain. He was killed in the Philippines at one of their stops).
The Galileo Project
Galileo Galilei built his first telescope in 1609. He used it to look at 4 objects near Jupiter that he first thought were stars. He realized that they were moons circling around Jupiter. This discovery was instrumental in showing that every object in the sky did not move around the earth. Here's more about Galileo.
Isaac Newton
Visit with Isaac Newton. He was from England. He was also interested in the movement of planets. In the middle 1600s, he figured out that the force that made the planets go around the sun was gravity.
Johannes Kepler
Chat with Johannes Kepler. He was from Germany. He was also interested in planetary cycles. In 1609, he studied the movement of the planets and realized that they did not move in a perfect circle around the sun. He figured out that they had an elliptical path. Here's more about Kepler.
Nicolaus Copernicus
Visit with Nicolaus Copernicus. He was from Poland. He was interested in planetary cycles. In 1543, he published his studies on the planets. His measurements of the paths of the planets suggested that they moved around the sun. Here's more about Copernicus.
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Things To Do

Stars and Galaxies (pdf)
Galaxies contain billions of stars. Students apply the concepts of scale to grasp the distances between stars and galaxies.
Complete Sun and Moon Data for One Day
Find the exact times for sunrise, sunset, moonrise, and moonset for your town.
Local Times Around the World
The earth is divided into 24 time zones. They start at the Greenwich Meridian in England where the time is called Greenwich Mean Time or G.M.T. Find out how we first measured time.
NOAA - Tides
Tides are the effect that the moon and the sun have on the oceans. When the earth, moon, and sun are in a line, the combined pull of the moon and sun causes the highest and lowest tides. Lean about Spring and neap tides both happen twice a month.
Solar System Extrema
Check out the largest, smallest, brightest and densest of the major bodies in the solar system and those with best prospects for life.
Star Child - Life Cycle of Stars
Find out how stars are formed. They have a cycle all their own that begins with a nebula and ends with a black hole.

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Teacher Resources

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  • Armentrout, Patricia. Tides and Waves. Vero Beach, Fla.: Rourke Press, c1996.
  • Clay, Rebecca. Stars and Galaxies. New York: Twenty-First Century Books, c1997.
  • Gallant, Roy A. When the Sun Dies. New York: Marshall Cavendish, 1999.
  • George, Michael. The Sun. Chanhassen, Minn.: Child's World, c1998.
  • Kosek, Jane Kelly. What's Inside the Sun? New York: PowerKids Press, 1999.
  • Rockwell, Anne F. Our Stars. San Diego: Silver Whistle/Harcourt Brace & Co., c1999.
  • Sipiera, Paul P. Stars. New York: Children's Press, 1997.
  • Tesar, Jenny E. The Moon. Des Plaines, Ill.: Heinemann Interactive Library, 1998.
  • Tesar, Jenny E. The Sun. Des Plaines, Ill.: Heinemann Interactive Library, c1998.
  • Walker, Niki. The Moon. New York: Crabtree Pub., c1998.
  • Welsbacher, Anne. Sun and Stars. Minneapolis, Minn: Abdo & Daughters, c1997