To protect us from the Sun's harmful Ultra violet rays, as well as some other stuff, there is a layer round the Earth called the Ozone layer.  It's not a physical layer of solid objects but rather a load of gasses high up in the sky.  The Earth is travelling at a speed of about 67,000 mph round the Sun.

Water at least 4 km deep covers 70% of the Earth's surface.   The largest land mass is Eurasia (most of Europe and most of Asia) which measures 53,698,000 km².  The Earth is only slightly larger than Venus yet Venus has only 80% the mass of the Earth.  This is mostly due to the fact that we have a dense iron-nickel core at the centre of our planet.  The Earth's magnetic field is much larger than that of any of the other rocky planets and this is also due to our iron-nickel core spinning so fast.  Our magnetic field is actually pear shaped, pointing away from the Sun (it's blown in that direction by the Solar Wind) and it also deflects harmful radiation away from the planet.

The Russian Sputnik was the first artificial satellite of the Earth in 1957, and this was followed by the Luna 1, also Russian, the first spacecraft to leave Earth's gravity.  The first weather satellite (the TIROS 1) was launched in 1960 by NASA.  Then,  in 1961, Russian Cosmonaut Yuri Gagarin became the first man to leave the Earth, in his Vostok 1.  The first humans orbited the moon in 1968 and in 1969 Neil Armstrong and 'Buzz' Aldrin landed on the moon.  The first space station, the American Skylab was launched in 1973.  In 1998 the first satellite of the Earth Observing System was launched.  Then, in 2000, the first permanent crew inhabited the International Space Station, now orbiting the Earth many miles above our heads.

Sun dogs

Q: What is a sun dog and what makes it happen?

A: A sun dog is a rainbow-like spot in a cirrus cloud. Light shining through ice crystals in the cloud makes a sun dog, much like light shining through raindrops makes a rainbow.  They are reddish on the side facing the sun and often have bluish-white tails stretching horizontally away from them.

Cirrus clouds — these high fleecy white bands or patches in the sky are mostly tiny particles of ice. Ice can take on many forms and shapes. The cloud ice, however, is shaped like hex bathroom tiles or stubby pencils each no bigger than the tiniest grains of sand. These ice crystals bend light like a prism, disperse its colours, and cause sun dogs.

When the crystals line up, the light shining through makes sun dogs. The horizontal crystals bend the light 22 degrees as the light enters and exits the crystal. Light colours fan out from the bending and display as a sun dog.

Sun dogs are among the most commonly seen sky phenomena, appearing most prominently when the sun is low. They usually appear in pairs two handbreadths on either side of the sun when it rises or sets behind a very thin veil of high cirrus clouds.

Aurora

Auroras occur around Earth's north and south geomagnetic poles in regions known as auroral ovals. Southern auroras are called aurora australis; northern ones, aurora borealis.

The aurora is higher in the atmosphere than the highest jet plane flies. The lowest fringes are at least 40 miles above the Earth, while the uppermost reaches of the aurora extend 600 miles above the Earth. The space shuttle flies near 190 miles altitude.

Although there are stories about the aurora seeming to reach down into the clouds or to the tops of mountains, these are either illusions or some phenomenon other than the aurora. Only astronauts can fly through the aurora!

Some people believe that the aurora makes sound that accompanies the ripples and flow of the light. If the aurora does make sound, the sound would have to be generated here on Earth by some electromagnetic effect. Any noise generated by the aurora would take a long, long time to travel all the way to Earth, and the air up by the aurora is much too thin to carry sound. So does the aurora make noises? Nobody knows for sure!

Auroras occur because Earth's magnetic field interacts with the solar wind, a tenuous mix of charged particles blowing away from the sun. This wind from the sun sweeps by Earth in the interplanetary magnetic field, which is produced by the sun. We are protected from the solar wind's direct effects by Earth's comet-shaped magnetosphere, where the Earth's magnetic field is distorted by the interplanetary magnetic field and the solar wind. The electrical energy generated by the charged particles blowing across the Earth's magnetic field send charged particles down into the Earth's upper atmosphere.

Auroral light is similar to light from a colour television. In the picture tube, a beam of electrons controlled by electric and magnetic fields strikes the screen, making it glow in different colours, according to the type of chemicals (phosphors) that coat the screen. Auroral light is from the air glowing as charged particles, particularly electrons, rain down along the Earth's magnetic field lines. The colour of the aurora depends on the type of atom or molecule struck by the charged particles.

Each atmospheric gas glows with a particular colour, depending on its electrical state (ionised or neutral) and on the energy of the particle that hits the atmospheric gas. High-altitude oxygen, about 200 miles up, is the source of the rare, all-red auroras. Oxygen at lower altitudes, about 60 miles up, produce a brilliant yellow-green, the brightest and most common auroral colour. Ionised nitrogen molecules produce blue light; neutral nitrogen glows red. Auroral displays vary from night to night and during a single night. Usually, if sun-earth conditions produce an auroral substorm, a diffuse patch of glowing sky will be seen first, followed by a discrete arc that brightens, perhaps a thousand-fold in a minute. As an arc moves toward the equator, new ones may form on its poleward side. Appearing within arcs are upward-reaching striations aligned with the magnetic field, giving the impression of curtains of light. Ripples and curls dance along the arc curtains and pulsating patches of light may appear in the morning hours.