How do animals know when a storm is approaching?
(http://encarta.msn.com/author_askbillnye/Ask_Bill_Nye.html)
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If you're an animal; how do you sense storms? Let me ask it another way. How would you know that animals were sensing storms, if you were not sensing them as well? You can see dark clouds. You can feel the wind. So can cows and birds. Although cows might not seem to be thinking too hard, they certainly could be feeling wind, cold, and pressure changes.

I mean, they're out there all day and often all night. For cows and other farm animals to make it this far in the eons that have passed since the Earth came into existence, they must have noticed a few things like storms. Then for birds to sense a storm coming, they're stuck using nothing more than their birdbrains. They nevertheless can see about eight times as much detail in what they're looking at as we can. They have eight times as many cells in the back of their eyes. We have an expression, "eagle eye," for someone with particularly good eyesight. Even though their brains are small, birds can process enough information to allow them to fly in precise paths. Their eyes are so good they can hunt from the sky. You've got to figure that they can see storms just fine.

When a thunderstorm approaches me, my ears pop. No kidding. I'm sure my ears pop as the atmospheric pressure goes down. Our atmosphere sloshes like water in a tub. Where the atmosphere sloshes so that there is less air between the ground and outer space, that's where we have low pressure and storms.

Here's how it works. The water vapor in the air changes--it stops staying a gas. As the pressure of the air it's mixed with goes down, the energy of the water vapor gets spread out. It cools off and changes from a vapor to a liquid--raindrops. We get rain, snow, sleet, and hail.

Perhaps country animals aren't distracted by human activities like school, baseball, and visiting Web sites, so they see the sky. Be an animal, and take time to notice the weather. It's beautiful.