HOW HTML CODE WORKS
Try our interactive form to learn about HTML code. Build your own web page by changing the code - then view the results instantly in your browser window. This is fun stuff!

LEARN HTML
Our step by step guide to building your own web pages. Simple "copy and paste" instructions allow you to create a basic page, and then add or modify text, fonts, font sizes, colors, background colors, graphics, links, lists, etc.

HOW GEARS WORK
Learn about gears, gear ratios and gear trains so that you can understand what all the different gears you see are doing.

HOW A COMPASS WORKS
Learn how a compass work and make a compass from scratch.

HOW A BLOCK AND TACKLE WORKS
See how a block and tackle works, and examine several other force-multiplying devices.

HOW DOES A CATAPULT WORK?
There are several different technologies that fall into the "catapult" category. They include the catapult, the ballista and the trebuchet.

HOW TO BUILD CATAPULTS AND TREBUCHETS
Here is a collection of plans collected from around the web, compiled from several sources by many people. Some are suitable for physics projects, and some are for more serious hobbyists. You'll have to figure out which ones are right for you.

THE TRACTION TREBUCHET PAGE
With a Traction Trebuchet the power is human muscle. A team of people haul down on ropes hanging from the short end of the beam which causes the other side to go up - and throw whatever is on that side.

MEDIEVAL SEIGE
The trebuchet was only the most frightening of the weapons early European warriors employed in siege warfare.

TREBUCHET PLANS
For people who like to hurl! This page discusses the design, construction, and firing of a 1/6 scale trebuchet.

HOW A PROPELLER WORKS (Athropolis)
The surface of a propeller blade is curved so that the blade has the shape of an airfoil... From our GLOSSARY.

A PROPELLER EXPERIMENT
You'll need a wagon or roller skate, a small electric fan, and a long extension cord...

ANOTHER PROPELLER EXPERIMENT
Make one.

HOW TELESCOPES WORK
Maybe you've been out looking at the stars in the night sky, searching for constellations; or maybe you'd like to take a closer look at the moon, planets or stars - with the aid of a telescope

CAN HOT WATER FREEZE FASTER THAN COLD?
Yes. Here's an explanation.

HOW THERMOMETERS WORK
An explanation of bulb and bi-metallic thermometers.

INVENTIONS FROM A TO Z
A great directory of inventions and inventors.