Floating on Air
Theme: The Lord provides “wind beneath our wings,” giving us support.
Bible Verse: But those who wait on the LORD shall renew their strength; they shall mount up with wings like eagles, they shall run and not be weary, they shall walk and not faint. (Isaiah 40:31)
Materials Needed:
• Hair dryer
• Balloon, ping-pong ball, or other lightweight ball
Bible Lesson
To hope in the Lord, or to wait upon the Lord, does not mean to give up or to sit back and do nothing. Instead, it means not giving in to the pressures and temptations of life. It is trusting steadily in God, fully expecting him to make things right in the end.
Eagles can fly with no apparent effort. They will soar for hours on thermals, rising currents of warm air. Likewise, Christians have invisible support from on high. This is not to say that we will never get sick or experience failure. The promise is that God will be with us during the high times of soaring and also during the low times of testing. The promise involves exchanging a reliance on our own limited strength for complete trust in Christ. Lasting strength, freedom, and endurance come only from God.
Science Activity
Perhaps you have seen this activity in a store window as an eye-catcher. A ball is suspended permanently in the air by a vacuum hose. It jumps and bounces around but does not fall. In science this is called the Bernoulli effect, whereby the ball is supported by the stream of moving air. The air pressure is actually smaller within the airstream than it is around the outside. The greater outside pressure pushes inward on the ball from all sides, thus suspending it in the moving air. Whenever the ball begins to leave the airstream, higher pressure pushes it back into the center.
A balloon or lightweight ball placed in the airstream of a hair dryer will float in the air.
The electric hair dryer must have a good speed of air, which need not be heated. Hold the dryer steady or fasten it to a support. A balloon, light ball, some cotton, or even a paper wad can be supported by the upward airflow. A vacuum cleaner also works well, but only if the airflow can be reversed from suction to an outward airflow.
Objects will remain suspended as long as the invisible airstream is active. Stop the airflow by covering the source with your hand and the object will fall. In the same way, an eagle would fall from the sky if it lost its supporting air. For the believer, there is no such danger of a power failure.
Science Explanation
The change in pressure caused by moving air can be substantial. For example, an airplane wing is designed to cause greater air speed above the wing surface than below. This results in higher pressure beneath the wing than above. The many thousands of pounds of upward lift cause the plane to fly. Winged flight is not possible on the moon or in space, where there is no air and therefore no pressure differences.
Daniel Bernoulli expressed the speed-pressure principle in 1738: “The pressure of a fluid decreases with increased velocity of the fluid.” This Bernoulli effect is also responsible for such details as the curving of a baseball and the motion of a Frisbee.