# See why astronauts are taller in space

Use books and sponges to represent a human spine and understand why astronauts grow taller in space, where gravity is much weaker.

## You will need:

• 4 large books (to represent vertebrae)
• 3 large flexible sponges (to represent the spongy tissue)
• 1 large rubber band or 1 rope (to represent gravity)
• Measuring tape

Stack books and sponges alternately to represent a human spine.

This model represents segments of the human spine and spinal cord.

## How to see the effect gravity has on your spine:

1. Stack the books and sponges alternately.
2. Press down on the stack of books and sponges to compress it.
3. Stretch the rubber band (or tighten the rope) around the stack to hold it in that position.
4. Measure the height of the stack.
5. Remove the rubber band (or the rope) while keeping the stack upright.
6. Once again, measure the height of the stack.
7. You will notice that the stack measures more without the rubber band (or the rope).

## What it means:

In this exercise, the books represent your vertebrae, the sponges represent the spongy tissue between your vertebrae, and the combination of the two represents your spine. The rubber band (or tightened rope) represents the force of gravity.

As you have seen, the force of gravity compresses the discs in the spinal column. When that force disappears, our spine stretches and we grow taller. That is why astronauts become taller when they are in space, where gravity is much weaker than on Earth.