INTRODUCTION FINDING THE WAY ou're hiking in the woods and suddenly everything looks the same You're lost and there's no trail in sight Thankfully you've got your compass You pull it out and hold it still The needle swings around showing you which way is north Now you can find your way Compasses are great tools especially in the woods or open seas where there aren't many landmarks Sailors have used compasses to navigate seas since the twelfth century They always work but do you know why It has to do with magnets and magnetism Magnets are pretty much everywhere from the door The needle of a compass always points north People began using simple compasses for navigation even before they understood how worked magnetism
With a map and a compass you can find your way out of the woods or nearly anywhere else of your fridge to the inside of your laptop Have you ever wondered what makes magnets work Or why some things stick to magnets and others don't These are the kinds of questions that lead to scientific theories Scientists study the world and ask questions about how it works Then they test their ideas through experiments and come up with answers based on evidence This process is known as scientific inquiry Through questions and experiments we can learn a lot about our world What do you want to know about magnetism 5
CHAPTER 1 AT IS A MAGNET ave you ever made a magnetic paper clip chain You just stick one paper clip to a magnet and then you can stick a second paper clip to the first one Soon you have a whole chain of dangling paper clips But if you take away the magnet all the paper clips fall apart How can the paper clips be magnetic one minute and then lose that force the next And why does the magnet stay magnetic Magnets have an invisible force that causes magnets to stick to some metals and to other magnets This force can also make some metals into magnets for a short time Some of these paper clips stick to other paper clips even though they are not touching the magnet The paper clips have become magnets temporary
Some ancient Chinese compasses were made from a flat piece of bronze and a magnetic stone carved into the shape of a spoon The spoon would spin to point in a north south direction EARLY MAGNETIC DISCOVERIES One kind of magnet is a mineral called magnetite Natural magnets are stones that contain magnetite The ancient Greeks and Chinese were the first to know about these magnetic stones which are called lodestones They realized that the stones attracted iron They also found out that if they rubbed a steel needle with a lodestone the needle became magnetic too If the needle was allowed to move freely it pointed north This discovery led to the compass first
