Ideal Solar Orbit...

Earth is sandwiched in an orbit between two terrestrial planets, Mars and Venus. Mars is a desert with a thin atmosphere. Venus is covered by a thick layer of corrosive carbon dioxide clouds, obscuring its super-heated surface below. Yet between these two forbidding worlds lies our Earth.

Earth is situated in a uniquely favorable position in the solar system, particularly with regards to its distance from the sun. It's just far enough away to be cool enough so that the oceans can condense. Yet not so far that its water would freeze over and the planet would become a ball of ice.

With an average temperature of less than -250 degrees C, Space is a very hostile environment for sustaining life. The temperature range for a planet to support liquid water is extremely narrow, from 0 to 100 degrees C. Unlike our neighbors, Venus and Mars, Earth is the perfect distance from the sun. Earth's average temperature is 59 degrees F. How did Earth come to be the ideal distance from the sun... just far enough away from the sun for the oceans to condense, but not so far that they would freeze?

Accidental - or intentional?

Ideal Surface Recycling System...

Earth is a geologically active planet. But unlike any other planets in our solar system, Earth employs a sophisticated geological process for continually recycling its surface.

The Earth's surface consists of huge tectonic plates. Driven by the convective motion of Earth's plastic interior, the plates grind against each other creating volcanoes, earthquakes, mountain ranges and ocean trenches. In fact, the entire surface of the Earth is completely recycled every 200 million years.

Earth maintains a critical balance between its interior forces (which cause volcanoes, mid-ocean rifts and mountains) and its exterior forces which cause erosion. Plate tectonics regenerates the mountains and coastlines that are being continuously degraded by atmospheric processes (like rain) and rivers. This recycling of the earth's crust is unique among the planets. Yet, if any one of these processes were to cease, Earth would become quite a different place.

What caused the Earth to be the only planet that recycles its surface?

Accidental - or intentional?

Ideal Atmosphere...

Earth has a unique atmosphere which screens and insulates it, yet provides just the right combination of gases we need to survive.

Earth's atmosphere is transparent to the Sun's visible light, but blocks most of the Sun's harmful ultraviolet and X-ray radiation. Earth's atmosphere also serves as an insulator by moderating temperature ranges. The Earth and the Moon are nearly the same distance from the Sun. But lacking an atmosphere, the Moon's surface temperature soars to 270 degrees after sunrise and plunges to -240 degrees after sunset. Earth's average surface temperature is 59 degrees and temperature highs and lows are held to much smaller differences.

Both Venus and Mars consist mainly of carbon dioxide (CO2). However, Earth's atmosphere contains only 0.03% CO2 and provides the perfect balance of gases for supporting life: 77% nitrogen, 22% oxygen, 1% water vapor and traces of argon, neon, sulfur, helium and carbon dioxide. Venus and Mars only contain trace amounts of the vital life-supporting gases, oxygen and nitrogen in their atmospheres.

Structured into four layers (see Figure), the troposphere contains eighty percent of the Earth's atmosphere. This is where weather takes place. The stratosphere contains the ozone which shields us from high energy photons (ultraviolet radiation). Mars, for example, has no ozone protection. UV radiation can break up molecules such as water into smaller fragments, allowing them to escape easily into space. Beyond the mesophere lies the thermosphere. The thermosphere contains individual atoms of oxygen and nitrogen which absorb very short-wavelength UV photons (which oxygen and nitrogen molecules cannot absorb).

Accidental - or intentional?

Ideal Planetary Physics...

Earth is the perfect size in mass to maintain an atmosphere. Although Venus is roughly the same size, Earth is the heaviest of the terrestrial planets, allowing it to manufacture and sustain several beneficial atmospheric levels.

Accidental - or intentional?

Ideal Climate Regulator - Our Unique Moon

The moon's gravitational pull keeps earth on an even keel, an average tilt of 23.5 degrees. This tilt provides our seasons.

By contrast, Mars lacks a big moon stabilizer, consequently it wobbles precipitously on its axis. Mar's tilt can vary anywhere from 0 to 90 degrees, playing havoc with its climate. Without our moon, the earth would wobble about in its solar orbit creating chaos of unpredictable weather patterns and temperature extremes.

Imagine a moon-less weather report - blizzards over the Sahara, floodwaters swallowing the Pyramids, 90-degree temperatures in Antarctica. As the earth wobbles on its axis - unsecured by the moon's gravitational pull - the polar caps would grow and recede at frightening rates. And without the moon, our planet would spin much faster - meaning four-hour days and searing temperatures. Arctic weather one day, possibly followed by intense tropical heat the next. This would create unlivable weather patterns of tornadoes, flooding and erosion. The polar ice caps would melt; Florida would disappear and coastal cities would be inundated with ocean water. Vegetation, which needs regular growing cycles, would not thrive, therefore oxygen would not be produced. The ozone layer would not exist and the sun's ultraviolet rays would burn up the earth's surface.

In fact, even the smallest changes in the earth's tilt can have profound effects. A less-than 1 degree shift in the earth's tilt once transformed the lush, greenlands of the Sahara - into the world's largest desert.

What caused the earth's tilt and how did we get such a perfectly-sized moon - with just the right distance and orbit?

Accidental - or intentional?

Ideal Greenhouse Effect...

The oceans play an important role in maintaining Earth's environment via the process known as the greenhouse effect.

The climate of the earth is determined by two processes: 1) the amount of solar radiation that the earth receives at its surface; 2) how that energy is retained by the earth. Visible radiation comes through the earth's atmosphere quite freely and is absorbed at the surface. This shortwave sunlight is then converted by the oceans, vegetation and surface to a longer infrared wavelength. That heat is then radiated away from the earth - but at different wavelengths of energy (infrared).

The earth's atmosphere is transparent to visible radiation (sunlight), but is relatively opaque to thermal infrared radiation. The gases that block this thermal radiation include water vapor and carbon dioxide. If the earth did not have this greenhouse effect, then the surface temperature would be 16 degrees below zero. In other words, the earth would be frozen.

How did the Earth's oceans, soil and vegetation develop the ability to shift the sun's short wavelength radiation - trapping just the right amount of the sun's energy?

Accidental - or intentional?

Earth's Perfect Energy Partner -the Sun...

The sun's rays allow photosynthesis in plants, which, in-turn, produce the oxygen that we breathe, the fossil fuels that we use for energy and the ozone layer that shields us from X-rays and harmful UV rays. Creating the convection which causes the wind, the sun acts as a giant heat pump in distributing heat and moisture away from the equator (largest surface area of sun's rays) throughout the globe.

Earth's Giant Bodyguard -Jupiter...

Jupiter's mass acts as a giant magnetic shield in attracting runaway meteors away from earth via its massive gravitational field.

Accidental - or intentional?