BEAKMAN, PHOEBE, & LESTER...

Weighing a car is a tough challenge, but we've put our heads together and figured out we can do it using our old pal, air pressure. Here's what you're going to need.

• Two pieces of posterboard.
• A ruler
• A pencil
• A tire pressure gauge
• A car

Remember, a car is a big, heavy object that can roll on top of you. So make sure you're with a grown-up and the car is turned off and parked on a flat surface. Set the emergency brake, too.

1. Push a piece of the posterboard under a tire in front as far as it will go and another piece of posterboard behind the tire.

2. Measure the gap between the two pieces of posterboard.

3. Then put the posterboard under the sides of the tire and measure the gap.

We're measuring the tire's footprint, or the part of the tire that touches the road. Now we need to measure the air inside the tire with our tire pressure gauge. Car tires are a lot like balloons. They're filled with air that pushes out in all directions. The tire pressure gauge measures how hard the air inside the tire is pushing out on the tire's walls.

4. Measure the tire pressure.

5. Multiply the first two measurements (the distances between the posterboards) to get the size of the tire's footprint.

6. Multiply the size of the tire's footprint (its area in square inches) by the air pressure (its pounds per square inch).

The number you get from these calculations tells you how much weight that tire is holding up.

7. Now do the calculations for the other three tires.

8. Add the results from all four tires together.

The more weight a tire holds up, the more that tire is flattened against the road and the bigger its footprint. So, if you know the size of a tire's footprint and the pressure of the air inside the tire, you can figure out how much weight that tire is holding up. And if you add the weight each tire is holding up, you know the general weight of the car. Check your cars owners manual for its official weight. If you come within ten percent, you've done a great job!

When something is too big or too small or too difficult to measure directly, scientists measure them indirectly. That means they measure one property in order to determine another. For example, when we measure temperature (the average kinetic energy of the molecules of a substance), we actually measure the length of a column of liquid (in a thermometer). The battery testing strips which are frequently included in packages of batteries do not measure the electric current directly. The current flowing through the test strip produces heat which changes the alignment of liquid crystals which, in turn, changes the color of the light they reflect! Even an ordinary scale measures weight by measuring the distortion of a spring.

Think about this: That big, heavy car or truck of yours is held up by nothing more than flimsy air! The tires do little more than contain the air. If you have any doubts, see how well the tires support the car when they don't contain air.

- For every human on earth, there are thirteen and a half million termites.

- People sweat as much as a quart or more liquid a day. Yummy!
- The average North American eats fifty tons of food and drinks eleven thousand gallons of liquid. That's in a lifetime? Most people proably eat more than that in a lunch time.

- The hair in our nostrils helps trap things like dust and pollen to keep them out of our bodies.

- The world's largest desert is the Sahara in Africa. At three and one half million square miles, it's sixteen times the size of France. Sacre bleu!

-By measuring the size of the Earth and the pull of gravity on it's surface, they've figured out that our planet Earth weighs six sextillion metric tons. That's six with twenty-one zeros after it: 6,000,000,000,000,000,000,000