Our Unique Earth

Our universe has captured the minds and imaginations of many throughout the years. Space exploration is slowly becoming common place in our day and age. But, with the discovery of billions of galaxies in our ever-expanding universe, is the Earth just another planet in the grand scheme of things?

Before the 16th century, it was widely accepted that the Earth was at the center of our solar system, while the surrounding planets, moons, and sun revolved around it, making it unique and remarkable. However, Nicolaus Copernicus challenged this idea. He proposed that the Earth, and other planetary bodies in our solar system, revolve around the sun.

"Today, the 'Copernican Principle' – stating that not just we, but no one, occupies a special place in the Universe – is a bedrock tenet of modern cosmology." (New Astronomical Discovery Challenges 500-Year-Old 'Copernican Principle', Forbes.com)

Edwin Hubble solidified this notion with his discoveries in the 1920's. Using the 100-inch telescope at Mount Wilson, Hubble documented several galaxies beyond the Milky Way, proving that the universe was not specific to our own galaxy. With billions of galaxies now evident, our planet was hardly distinguished at all.

Carl Sagan in his book, 'Pale Blue Dot' described the Earth based on an image taken by Voyager 1 on February 14, 1990:

"Look again at that dot. That's here. That's home. That's us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives… Our planet is only a speck in the great enveloping cosmic dark." (Carl Sagan, Pale Blue Dot, 1994)

But is this so? Is the Earth just another lonely speck? Is there nothing special or unique about it?

With the advent of outer space exploration, evidence of complex life is seen as unique to Earth. While there are some who speculate that fossilized microscopic life may have been discovered on Mars, the complexity of life we see on Earth is by no means comparable. All the requirements for complex life to exist and thrive are present and precisely balanced.

Liquid water, as many would agree, is essential to life, and as you can probably tell, Earth has tons of it! Liquid water makes up 71% of the Earth's surface. But liquid water is not the only factor – Europa, one of Jupiter's moons, is hypothesized to have liquid water below the surface; however, there has been no evidence of life. Liquid water is essential, but not the only factor.

Another essential requirement is Earth's atmosphere. This thin layer measures less than 1% of the Earth's diameter. It is composed of 78% nitrogen, 21% oxygen and 1% argon – a mixture that is essential for liquid water to exist and a suitable environment for complex life to breathe. Our atmosphere also allows for our temperate climate, while blocking the unwanted radiation from space.

We also have our moon. Approximately a quarter the size of Earth, our moon stabilizes the planet on its axis at a constant 23.5 degrees, which ensures mild seasonal changes and temperatures, which would otherwise be too drastic for life.

The size of the sun is another important factor. Our sun is referred to as a spectral type G2 dwarf main sequence star and its size plays a key role in complex life. If our sun was smaller, like 90% of the other suns in our galaxy, the habitable zone of the Earth (the distance from the sun) would be need to be closer. The increased gravitational pull resulting from this short distance would cause the Earth's rotation to be in synch with its orbit around the sun – half of the earth would be in complete and utter darkness with cold and icy temperatures, while the other half would be constantly bombarded with solar radiation and become a desolate wasteland.

While the Earth is positioned perfectly in the habitable zone in our solar system with the right size sun, it is also situated in the galactic habitable zone of our galaxy – the milky way. The core of the milky way is comprised of millions of exploding suns and a black hole at the very center, while the outer edges of the galaxy lack the natural elements for life to exist. The galactic habitable zone is the ideal spot within our galaxy that life can exist; however, being within this zone is not the only factor. While you can be within the galactic habitable zone, the spiral 'arms' of the galaxy would pose a threat with several super novae present. The Earth, by all odds, managed to be within the galactic habitable zone, but outside of the galaxy's spiral arms, nested in a comfortable environment for complex life to exist.

There are myriads of other requirements, but it is undeniable that complex and intelligent life thrives on Earth. This level of complexity is defined by the innumerable number of species and other living organisms discovered. Many will think the complex life we see today is a result of evolution – the slow and gradual transformation of species through time. But, if we are a mere speck in this cosmic darkness and there is nothing distinguishable about the Earth, why is it that evolutionary biology hasn't occurred in any other parts of the known universe? If there are microbial life on Mars, why hasn't it evolved? Shouldn't evolution be an unchanging law much like the physical laws present throughout the universe? It would seem that evolution was partial to the Earth.

Contrary to what some may believe, the Earth is unique. It has all the necessary requirements for life to exist and thrive. We are not a mere happenstance in the cosmic dark, but it would seem that our planet was designed for us to inhabit. The abundance of liquid water, the right size sun and moon and our perfect placement in the cosmos appears to be that of a designer rather than a mere accident.