Education and
Public Engagement
at the Lunar and Planetary Institute
Health in Space

Space Stations - Sponge Spool Spine


Children model what happens to a human spine in space by making a Sponge Spool Spine (alternating sponge pieces and spools threaded on a pipe cleaner). This represents a human spine on Earth, with the discs (sponges) pressed between the spinal vertebrae (the wooden spools). The children measure the spine length, dip it in a container of water (simulating the free fall that astronauts experience in orbit), and then re-measure the spine. They will find it has expanded, just like in space!

Activity Time

5 minutes

Type of Program

Facilitated hands-on experience
Station, presented in combination with related activities
Passive program
Demonstration by facilitator

Intended Audience

Families or other mixed-age groups, including children as young as 4 years old with assistance from an older child, teen, or adult
School-aged children ages 5–7 and 8–9
Tweens up to about age 13

What's the Point?


For the facilitator:

For Each Group of 10-15 Children



1.  Share ideas and knowledge.

Earth’s gravity still affects the space station and the astronauts, but since they are continually falling around the Earth (i.e., orbiting), they constantly experience that free-fall feeling we occasionally experience on amusement park rides. Astronauts aren’t riding a roller coaster, though; they are riding the International Space Station at 17,500 miles (28,000 kilometers) per hour, 200-250 miles (about 320-400 kilometers) above the Earth! Since the astronauts, their food and supplies, and their spacecraft are all falling together in orbit around the Earth, everything appears to float.

Use the terms “free-fall” and “microgravity”; the terms “zero gravity” and “weightlessness” are don’t give an accurate impression about how gravity works in space.

With older children, explain that the free-fall environment that astronauts experience in space is called microgravity. As they orbit Earth, the effect of gravity is so small (“micro-“), that it does not matter that a feather, a person, and a spacecraft all have different masses (i.e., are made up of different amounts of matter).

2.  Build a model spine.
Explain that the sponges represent disks in a person’s spine, and the wooden spools represent vertebrae. Encourage each participant to build his or her model as follows: Sponge Spool Spine

  1. Take 3 wooden spools. Take 3 dime-sized pieces of dry sponge and use a slightly sharpened pencil or pointy stick to poke a hole through the middle of each sponge piece. Twirl the pencil around to make a bigger hole.
  2. With one chenille stick, make a small loop at one end (the bottom), and push the pipe cleaner through the sponge disks and wooden spools, alternating discs and spools.
  3. Cut a second chenille stick in half to make “legs” and “arms.” Wrap one half of the chenille stick around the bottom of the “spine” to make legs — be sure to leave an inch or so of space between the “legs” and “spine.”
  4. Wrap the second half of a chenille stick above the discs and
    sponges — again leaving an inch or so of space — to make arms.  
  5. Optional: Add a sponge disc to the top of the chenille stick to form a head.

3.  Model what happens to an astronaut’s spine in space.  Have each participant take turns using the container of water to mimic microgravity, as follows:  

  1. Measure the length of the sponge spine — only the spools and sponges! — with a ruler and record your measurement. 
  2. Predict what will happen to the Sponge Spool Spine in “microgravity.”
  3. Gently lower the Sponge Spool Spine into the water and observe what happens.
  4. Measure the length of the sponge spine again and record your measurement.

4.  Share observations and connect them to the “real world.” Prompt the children to compare their measurements before and after the Sponge Spool Spine became wet with other children and/or family members. Prompt them to connect that experience to what astronauts experience in space.

5.  Explain that in space (a microgravity environment), astronauts grow taller in space — sometimes as much as two inches! They also suffer from headaches, back aches, and dizziness at times because their tissue and nerves stretch. On Earth, t he force of Earth's gravity pulls on our skeletons, causing our spines to compress. This model represents what happens to our spines in reduced gravity — they elongate because there is no net gravitational force pulling on them.

6.  Conclude. Summarize that there are many challenges astronauts face as they live and work in space, and they must be very fit to take on all the changes that happen to their bodies in space.


Weightlessness Demonstration
This Windows to the Universe® activity outlines facilitator steps to illustrate the effects of free fall using cups and water. Appropriate for ages 10–18.