Space Stations - Measure Up!
Type of Program
What's the Point?
1. Share ideas and knowledge.
- Introduce yourself. Help the children learn each other’s names (if they don’t know each other already).
- Use the Explore! Health in Space Discussion Guide to draw participants into the activity and frame the activity with the main message: Astronauts — and kids! — need to keep fit to take on life’s challenges.
- Ask the participants to describe the feeling of free-fall, which they may have experienced very briefly on a free-fall ride or roller coaster at an amusement park or on an elevator, just as the car started to descend.
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.
- Explain that astronauts experience free-fall all day, every day as they orbit the Earth. As astronauts float, the blood and water inside of them also floats.
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. Measure the same changes that astronauts experience in space. Encourage each pair of participants to take turns with the following steps:
- While they are standing up, wrap the string once around your partner’s ankle. Make a mark where the end of the string comes back into contact with the rest of the string. Measure the distance from the end of the string to the mark and record your measurement.
- Have your partner lay on the floor near a wall with his or her legs in the air leaning against the wall for one minute. After one minute, measure his or her ankle again — while his or her legs still are propped against the wall —with a different color, and record that measurement. Be sure to measure the ankle at the same place.
3. Compare observations and connect them to the “real world.”Prompt the participants to compare their ankle measurements before and after lying on their backs with their legs against the wall. Prompt them to connect that experience to what astronauts experience in space.
4. Explain that in space (a microgravity environment), objects “float.” This includes fluids, such as drinking water — and fluids (blood and water) inside the human body. This fluid shift causes the upper portion of astronauts'' bodies to swell, and their lower extremities to shrink. By lying upside down, the fluid in each partner’s body shifted. It was pulled down out of his or her ankles by Earth’s gravity.
On Earth, our bodies actively pump fluids back from our arms and legs. In a microgravity environment, astronaut’s bodies’ do not have to fight gravity to return blood and other fluids to the torso and head. Because we are on Earth, we have to lie down to cause our bodies’ fluids to shift in this same way.
Our bodies are made of 60% water, most of which is contained in our cells and circulatory system. Our bodies are well adapted to dealing with Earth's gravity; our hearts pump our blood and keep it from pooling in our feet. In microgravity conditions, however, things float. This includes the fluids in the human body! Without gravity pulling fluids into their legs, astronauts' bodies preferentially keep fluids in the torso and head. Within minutes of experiencing microgravity, fluids in the astronauts' bodies shift, causing puffy faces and shrunken legs and extremities — what they call "chicken leg syndrome!"