May 14 is the birthday of Gabriel Fahrenheit, as in "It's 32° Fahrenheit." Exactly who was Fahrenheit? He was a German physicist who developed the alcohol thermometer in 1709 and the mercury thermometer five years later, which meant temperature could be measured with more accuracy and universal agreement. Fahrenheit devised a scale for his thermometer and called every unit of change a degree.

Today, Fahrenheit would marvel at the wonders of measurement — and what you can learn about it on the World Wide Web. You can teach your students about the many kinds of meteorological measurements that are used to gauge weather every second nowadays and how thermometers actually measure temperature. Not only can they explore how temperature is measured, they can find out the temperatures and precipitation worldwide and all over the United States. Temperature and precipitation are only part of what is measured to form an accurate picture and predict the weather. The measurement of atmospheric pressure — the pressure that the atmosphere puts upon the surface of the Earth — is basic to meteorology and weather forecasting.

It's fun to click on a current weather map of the United States and discover that the temperature this hour in Seattle is 61°F and the barometric pressure 30.14 inches. But your students can also understand how scientists use the Internet daily in their work. The United States Geological Survey, for instance, provides data on the measurement of stream flow on the Web, where you can see the data for your local river or stream. Because this constantly updated data is posted on the Web, leaders in various towns have been able to make timely decisions about evacuation when floods threatened.

While you're thinking about measurement, you can show students about the precise measurement of time by using the U.S. Naval Observatory's Master Clock.