Universe Cycle - Universe (1)

  • Discovering that the Sun is a star.
  • Comparing and contrasting bodies that reflect light.
  • comet
  • light
  • reflect
  • star

Students learn that stars generate their own light.

This is a spiral galaxy with many stars
 generating their own energy. 


A star is a ball of burning gases, mostly hydrogen and helium. A star shines or glows because its gravity causes its gases to fuse together. This process releases energy, hence the "shine". Our Sun is only a medium-sized star. There are stars that are bigger, smaller, hotter, and cooler. However, the Earth is very small compared to the Sun. More than a million Earths could fit into the Sun. All life on Earth depends on the Sun for light and heat.

Until the seventeenth century, most scientists thought that the Earth was the center of the Universe, mainly because it appears that way to casual observation. It is quite obvious that the Sun and Moon travel across the sky from east to west. Ancient people often thought that the Sun and Moon were gods with chariots such as Apollo and Athena, and gave them personalities.

Part of this confusion was because while all sky objects appear bright, some stars and galaxies (collections of stars) radiate light, while the others only reflect light. This is sometimes difficult for children to understand as well. When they look up at the night sky, they see the brightly shining moon. How can it be that it does not produce its own light, but yet it shines?

The stars make their own light. The Moon, planets, asteroids, natural satellites, and comets shine by light reflected from the Sun. The Moon has no light of its own, so it appears to have phases, cycling from new Moon to full Moon and back every 29 days. The phases happen because of the angle at which the Sun's rays strike the Moon relative to the Earth, but the exact mechanism will be explained in the later grades.

  1. In this lab activity, students will learn that bodies in space can be classified in two many ways: (1) those bodies that produce light (stars) and (2) those bodies that do not (planets, comets, meteorites, and most everything else in space).
  2. A flashlight or an energy ball can be an example of an object that produces its own light. Show students these items and discuss whether the light is produced inside or not. A flashlight is like a star. If you put an object, like a basketball in a dark room, you will not see the basketball. However, if you shine the flashlight on the ball, you can see the basketball in the dark. The basketball is the Moon or Earth and the flashlight is the Sun. You many want to demonstrate this in class.
  3. Comets also reflect light from the Sun. A comet is an object that is made up of gases and "rocks." Comets do not pass Earth very often and ancient peoples were frightened of them. Give each pair of students one "comet ball." (A ball with reflective streamers.) Give several students the energy balls to act as shining stars in the room. Two or three students should have control of the flashlight to shine it as students are tossing the comets.
  4. Students will have to throw the comets to their partner. Make them practice several times because when you turn the lights out you want them to be able to catch the comets. Then turn the lights off and ask students if they can see any comets when they throw them to their partner. They should answer no. Next, put several flashlights around the room, and shine them on the energy balls. Have the students throw the comets again. Ask them when can they see the comets. They should realize that the comets are only visible when they come into contact with the light. The comet is reflecting light, not producing light. The students using the energy balls are representing stars.

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