BACKGROUND:
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 comet’s
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 Earth’s 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
Earth’s atmosphere. Third, comets may be visible in the sky for days to
months as they orbit near the Sun.
PROCEDURE:
- 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.
- 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.
- 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:
- Line mixing bowl with plastic wrap. Place 500 ml water in bowl.
- Place 5 ml of soil, and stir well.
- Add dash of ammonia and mix.
- Add dash of corn syrup and mix.
- Add 500 ml of crushed dry ice, and mix until mixture is almost
frozen.
- 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.
- 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.
- 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.
http://map.gsfc.nasa.gov/
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.
http://www.damtp.cam.ac.uk/user/gr/public/
Cambridge Relativity of Cambridge University. Discusses Cosmology, Black
Holes,Inflation, Cosmic stings, and more.... Good illustrations and
graphics.
