In 1969, when observing the Earth from the moon, Apollo astronaut James Irwin said, “When you lean far back and look up, you can see the earth like a beautiful, fragile Christmas tree ornament hanging in the blackness of space”.1 The delicate blue shell of the atmosphere, the deep blue of the sea, the brown continents, the white polar caps and smudges of cloud, all in stark contrast with the pitch blackness of space with its myriads of stars, make the earth the most beautiful place in the universe.
There is a hidden beauty about our planet that makes it apparent that Earth is extraordinarily well suited to be the home for mankind, just as it has been designed to be. Let’s explore just a few of the amazing features of our planet that make it so well suited for life.
Planet Earth moves in a nearly perfectly circular orbit in what is called the circumstellar habitable zone, or ‘Goldilocks’ zone, around the sun. This zone is where liquid water can exist so it is not too hot, to prevent all the water from boiling away, and not too cold, to prevent all the water from freezing solid. For liquid water to exist on a planet, that planet must have a solid surface and an atmosphere providing sufficient pressure at the surface to prevent all the water evaporating. In fact, on earth, water can and does exist in all three states (liquid, solid (ice) and water vapour) and can move relatively easily between them. If the earth’s orbit were highly elliptical, there would be large variations in temperature, making the environment unsuitable for life.
The more we learn about our planet the more amazed we are at how extraordinarily well suited it is for life
The earth spins on its axis once per solar day, providing variation of night and day and providing colourful displays in the clouds at sunrise and sunset. The rotation of the earth helps to regulate the temperature around the globe so no one part becomes too hot or too cold. If the earth were tidally locked to the sun, as the moon is to the Earth, one side would be permanently facing the sun, and would be searingly hot, with the other in permanent frozen darkness.
The axis of the earth is tilted about 23.5 degrees with respect to the plane in which the earth orbits the sun, so we experience a variation of seasons each year. In the northern hemisphere summer, the North Pole is tilted towards the sun so the sun is higher in the sky and the days are longer than the nights. At the same time the southern hemisphere is experiencing its winter. The reverse is true six months later. When the sun passes through Earth’s equatorial plane, the days and nights are of equal length. This is called equinox and occurs in late March and late September.
The variation of seasons is vital for many forms of life to thrive. The annual cycle of cold to warm seasons regenerates plants and animals and serves to measure the passing of time with variety in the weather conditions around us. The warmth of summer gives way to the glorious colours of autumn, then to the repose of winter followed by the explosion of new life in the spring.