The Sun: Our Nearest Star

The Sun is a star — an enormous ball of extremely hot glowing gas. It looks different from the other stars only because it is so much closer.

Some numbers worth carrying:

Its energy crosses the emptiness between us by radiation, the only method of heat transfer that needs no material.

Why the Sun matters so much. Nearly every energy story on Earth begins with it:

• it warms the land, the sea and the air;
• green plants need its light in order to grow (exactly how they use it is a Grade 8 story);
• it drives the water cycle — sunlight evaporates water from the ocean, which later falls as rain over the Drakensberg;
• it drives the winds, by heating some parts of the Earth's surface more than others;
• and it powers solar panels and solar geysers directly.

Worked example — light's travel time. Sunlight takes about 8 minutes to reach us. In seconds that is

So the sunlight falling on your hand right now left the Sun about eight minutes ago.

A South African note. The Northern Cape has some of the strongest, most reliable sunshine on Earth, which is why large solar farms have been built near Upington and De Aar. A solar panel in South Africa is tilted to face north, because in the southern hemisphere the midday Sun stands in the northern half of the sky.