Lesson 4

The Big Attraction

What instrument do we use,

to tell us what direction to travel in?

compass is an instrument containing a freely suspended magnetic element which displays the direction of the horizontal component of the Earth's magnetic field at the point of observation. The magnetic compass is an old Chinese invention.

Compass

How does a compass work?

What is magnetism?

What are the laws of magnetism?

This is a drawing of a single magnet,

All magnetic objects produce invisible lines of force that extend between the poles of the object. An easy way to visualize this is to spread iron filings on a sheet of paper and place a bar magnet under the paper. The iron filings will arrange themselves around the magnet and

along the magnetic field lines.

As the Earth rotates, it generates a magnetic field.

Magnetic field lines radiate between Earth's north and south magnetic poles just as they do between the poles of a bar magnet. Charged particles become trapped on these field lines (just as the iron filings are trapped), forming the magnetosphere.

Rotational axis

There are two North Poles: the geographical and the magnetic North Pole.

The magnetosphere extends into the vacuum of space from approximately 80 to 60,000 kilometres (50 to 37,280 miles) on the side toward the Sun, and trails out more than 300,000 kilometres (186,500 miles) away from the Sun.

How do we make a Magnet?

Can we use any material to make a magnet?

The Aurora Borealis as seen in Alaska

When some high energy charged particles or ions, become trapped in the Earth's magnetic field above the poles complex reactions in the ionosphere give rise to aurorae (borealis (N) and australis(S)) visible as flickering and waving arcs, bands, curtains and streaks of coloured lights that are visible most nights above the pole.

1909 expedition to the North PoleRobert E. Peary, the great arctic explorer

Bowers, Evans, Scott, Oates and Wilson at the South Pole

The South Pole was exploration's last great prize, and was widely expected to be won by the British.

Race for Antarctic gloryDecember 1911

Roald Amundsen, born in 1872 near Oslo, Norway, left his mark on the Heroic Era as one of the most successful polar explorers ever born. His career of adventure began at the age of 15

Notes