Overall Height: 6" / 15cm
From How Stuff Works Website:
To operate the Dippy Bird, you get its head wet. As the water evaporates, fluid moves up into the head, causing the bird to become top-heavy and dip forward. Once the bird dips forward, fluid moves back into the abdomen, causing the bird to become bottom-heavy and tip up.
Here is how a Dippy Bird works:
1.When water evaporates from the fuzz on the Dippy Bird's head, the head is cooled.
2.The temperature decrease in the head condenses the methylene chloride vapor, decreasing the vapor pressure in the head relative to the vapor pressure in the abdomen.
3.The greater vapor pressure in the abdomen forces fluid up through the neck and into the head.
4.As fluid enters the head, it makes the Dippy Bird top-heavy.
5.The bird tips. Liquid travels to the head. The bottom of the tube is no longer submerged in liquid.
6.Vapor bubbles travel through the tube and into the head. Liquid drains from the head, displaced by the bubbles.
7.Fluid drains back into the abdomen, making the bird bottom-heavy.
8.The bird tips back up.
If the bird dips into a cup of water, the fuzzy material absorbs water again and the cycle starts over.
Your warm hand can cause fluid in the Dippy Bird to rise. If you hold a Dippy Bird upright in your hand, touching the abdomen, the following happens:
1.Your body heat warms the fluid in the abdomen.
2.The heat increases the vapor pressure in the abdomen relative to the head (the reverse of what happens when you wet the head).
3.The fluid rises into the head in response to the pressure difference (moving from high pressure to low pressure).
4.The bird becomes top-heavy, and tips.