The sun, moon and stars

The sun has been shining for 4.6 billion years and has remained relatively unchanged over time. The core temperature of the sun is 27 million degrees Fahrenheit, hotter than anything found on earth, even the earth’s fiery core.

Electricity can be generated from the sun's heat. Referred to as solar energy, it can be captured using solar reflective panels and stored in batteries or transferred directly into the electrical grid.

The moon’s surface is covered with craters from meteorites crashing into the surface from space. Because the moon is so small -- one-sixth the size of the earth -- it is unable to hold an atmosphere to protect it from the onslaught of passing meteors.

Gravity is an invisible force that pulls objects towards each other. Earth's gravity keeps us on the ground and makes things fall.

The moon also has very little gravitational pull, and walking on the moon is much harder than here on earth. The moon is the only celestial body other than earth that man has landed and walked on.

There are so many stars in the universe that it is impossible to count them all. About 7,000 stars can be seen with the naked eye from earth. Many stars and constellations were named in ancients times for gods and animals that they resembled.

Many stars that are visible no longer exist, but because their light takes so long to reach the earth, they are still visible long after they have expired. The turbulence in earth's atmosphere is the reason why the stars appear to twinkle when we look at them.

When we look at the stars in the night sky, it is difficult to imagine that our blazing sun is also a star. It is the star nearest to the Earth. Although the sun is close to the Earth in cosmic terms, it is still 93 million miles away.

The sun is 109 times wider than the Earth and 330,000 times heavier. The sun formed approximately 4.5 billion years ago and will burn for an estimated 5 billion years more, so the sun is at the mid-point of its lifespan.

Just to make it clearer, 300,000 times heavier is the difference between a can of soup and 100,000 gorillas!