Universe Cycle - Universe (3)
Pre Lab 

  • Students observe a model of a comet throughout the day.
  • Comparing comets with stars.
  • comet
  • gravity
  • meteorite
  • shooting stars
  • Solar System
  • Universe

Students observe a model of a comet throughout the day.

"Shooting stars" or meteorites

Halley's Comet


The study of the Universe is still new and exciting to third grade students. They have been exposed to words like Universe and Solar System, but still might not know how they fit together.

The Universe was created over 15 billion years ago. The Big Bang theory is the most widely accepted explanation for the creation of the Universe. This theory states that Universe began with a tremendous explosion and expansion, which rapidly created matter and energy as we know them. Many details about the Big Bang have yet to be discovered.

The Universe is composed of objects that are "attracted" to each other by gravity. After the Big Bang, matter in the Universe was distributed irregularly. The areas where more matter was clumped together had higher gravitation attraction, which pulled the matter closer together. This process eventually formed stars, solar systems, and all the other components of the Universe. Galaxies, which are major clusters of stars, are a remnant of this original clumping of matter.

A fun way to begin the Universe Cycle is to make a model of a comet. Most comets reside in areas outside the Solar System proper. The comets that we see from Earth, orbit the Sun. Theoretically there should be other solar systems that have their own comets, but the only comets we can see are part of our Solar System.

The name "comet" comes from the Greek word for hair. It suggests an imagined resemblance between the tail of a comet and long hair streaming in the wind. Comets, many scientists think, are leftovers from the formation of the Solar System. The main part of a comet is its nucleus, which is composed of frozen gas, rocks, and sometimes small amounts of organic material (not biologically created, as far as we know). The ingredients in the comet recipe, dry ice, ammonia, water, corn syrup, and soil, simulate the real composition of comets.

When a comet is close to the Sun, solar radiation heats it up. The nucleus becomes surrounded by a glowing coma of vaporized gas. The solar wind blows parts of the coma away, forming the cometís tail, which may be millions of kilometers in length. Comets are only visible to the naked eye when they have a coma and tail.

Students may confuse comets with "shooting stars". These are meteorites (rocks left over from the formation of the Solar System) that enter the Earthís atmosphere and burn up leaving a trail of ionized gas behind. "Shooting stars" glow for a matter of seconds at most. Comets differ from meteorites in three ways. First, as above, they are "dirty snowballs"; they are composed of frozen gas and rock, and are much less dense than meteorites. Second, comets orbit the Sun, and rarely come close to the Earth, whereas shooting stars enter the Earthís atmosphere. Third, comets may be visible in the sky for days to months as they orbit near the Sun.

  1. Make sure that students review what items are in the Universe. Quiz them on the meaning of the following words: stars, galaxy, planet, and nebula. It is important that by this grade that the students can distinguish that the Universe is the big picture, and that the Solar System is just a very small part of it.
  2. Making a comet for the students gives them a fun introduction to the wonders of the Universe. You should make the comet in the morning so the students can see the "comet" change throughout the day. You may want to do this activity with all the third graders. If there is comet mixture left over, you can share with other grade levels.
  3. We suggest that you mix the ingredients in front of students, so you can explain why you are putting them together. Caution: Use Plastic Gloves when handling the dry ice

    Directions to make a comet:

    1. Line mixing bowl with plastic wrap. Place 500 ml water in bowl.
    2. Place 5 ml of soil, and stir well.
    3. Add dash of ammonia and mix.
    4. Add dash of corn syrup and mix.
    5. Add 500 ml of crushed dry ice, and mix until mixture is almost frozen.
    6. Lift the comet out of the bowl, using the plastic liner and shape it as you would a snowball. Make sure you have plastic or well insulated gloves to prevent burns.

    This mixture will make a spooky mist. Do not let students touch the material, unless they have gloves on. In our experience, the students get very excited, so you may have to remind them to stay away from it.

  4. Place the mixture in a tray and have the students observe the comet throughout the day. It may take up to 3 or 4 hours before the comet disappears. You may want to record the findings on the board. There will sometimes be little "pops" during the day. This is occurs when pockets of gas escape from the comet.
  5. The Internet is full of wonderful information on the Universe. Below are a few sites that you might want the students to surf for information.
    A site from NASA that contains good scientific information on current research at the galaxy and universe level. Fundamental investigations on the large scale structure of the Universe, including the Big Bang and how galaxies may have formed.
    The Hubbles Space Telescope website, with animations of planets and galaxies. Links to the mother site, containing innumerable Hubble Space Telescope pictures.
    Cambridge Relativity of Cambridge University. Discusses Cosmology, Black Holes,Inflation, Cosmic stings, and more.... Good illustrations and graphics.
    Pictures of stars and galaxies....all star line up.
    "Star Journey" - a National Geographic site which includes star charts of the nighttime sky.

    The Constellations and Their Stars - includes interactive sky charts and pictures of stars and galaxies. 

[Back to Universe Cycle Grid]
   [Back to Universe (3)]