Earth refers to the planet we live on, our home, and home to millions of different life forms. The Earth is also known as "the world".
The third planet from the Sun in the Solar System (located in the Local Interstellar Cloud, Local Bubble, Orion–Cygnus Arm, the Milky Way), Earth is known as the "Goldilocks planet" because it has the conditions suitable to sustain life. It is the largest of the four terrestrial planets in the Solar System. Thus far, it is the only known astronomical source sustaining life in the Solar System, making it a very special place indeed.
Formation of Earth[edit | edit source]
Geology is the science used to study the Earth. It is through geological research that scientists have been able to piece together when and how Earth was formed over enormous spans of time. Geology must cover time spans of tens of thousands to millions of years when looking at Earth's history. This can be hard for the human mind to grasp, but that doesn't make the time scale any less real.
Through scientific research, the age of the Earth has been found to be about 4.54 billion years. Life on Earth arose around 3.5 billion years ago when the first living cells developed. Human origins form only a small portion of Earth's history.
Life on Earth[edit | edit source]
Earth as a system[edit | edit source]
Earth is a complex system, consisting of the atmosphere, biosphere, hydrosphere and interior. Each component interacts with each other component. For the study of Earth, the component parts need to be studied independently to better understand them but such closer research of each component must always be done with a constant view to how the components contribute to and interact with the whole Earth system.
Inspiring Earth[edit | edit source]
The Earth has long inspired human awe, inspiration and determination to survive upon it.
An interesting point to ponder is how much humanity has learned about the miraculous nature of life, the amazing balance of this Goldilocks planet, from being able to finally see our amazing planet from space. In 1948 Sir Fred Hoyle commented: "Once a photograph of the Earth, taken from the outside, is available, a new idea as powerful as any in history will be let loose." From the 1930s, grainy and incomplete photographs of the Earth were taken from balloons and rockets, revealing the curvature of Earth and giving humanity its first glimpses of the amazing planet it resided upon. By the 1950s, humanity was able to see photographs of Earth against the black backdrop of space. In 1972, on 7th December, the most iconic image of the Earth was taken by the crew on the Apollo 17 spacecraft. This image is known as "The Blue Marble". One of the most widely distributed images in human history, it has had a significant impact on human understanding of our place in the universe, a unique and beautiful perspective. In 2015, 43 years after The Blue Marble was taken, NASA released a new photo of the Earth in its entirety (not a stitched-together or composite format as many photos of the Earth tend to be), as taken by the onboard camera of the Deep Space Climate Observatory (DSCOVR). NASA intends to take "daily selfies" of the planet using the Discover satellite when fully operational, which will be one more source by which we can monitor and gauge the planet's health and changes, such as atmospheric changes, cloud height and ultraviolet reflectivity.
For astronauts, the few human beings to have seen Earth through their own eyes and not the medium of the camera, the recognition of Earth's incredible status is known as the "overview effect", that realisation that we live on a planet that is a "shared home", and it instills a sense of awe. For the rest of us, photographs of the Earth from space remind us of how unique and special our planet is, inspiring us to realise, more than ever, that this is a truly special part of the universe that is worth caring for and treating with respect.
Some of the comments about Earth after seeing it for real from space or from images of it taken from space include:
- Yuri Gagarin (Cosmonaut, First Human in Space): “When I watched the horizon, I saw the abrupt, contrasting transition from the earth’s light-colored surface to the absolutely black sky. I enjoyed the rich color spectrum of the earth. It is surrounded by a light blue aureole that gradually darkens, becoming turquoise, dark blue, violet, and finally coal black.”
- Neil Armstrong (Apollo astronaut, looking back at the Earth from the Moon in July 1969.): "I didn’t feel like a giant. I felt very, very small."
- William Anders (Apollo astronaut): "We came all this way to explore the moon, and the most important thing is that we discovered the Earth."
- Nicole Stott (shuttle/ISS astronaut): "We have this connection to Earth. I mean, it's our home. And I don't know how you can come back and not, in some way, be changed. It may be subtle. You see a difference in different people in their general response when they come back from space. But I think, collectively, everybody has that emblazoned on their memories, the way the planet looks. You can't take that lightly."
- Ron Garan (shuttle/ISS astronaut): "When we look down at the earth from space, we see this amazing, indescribably beautiful planet. It looks like a living, breathing organism. But it also, at the same time, looks extremely fragile. [...] Anybody else who's ever gone to space says the same thing because it really is striking and it's really sobering to see this paper-thin layer and to realize that that little paper-thin layer is all that protects every living thing on Earth from death, basically. From the harshness of space."
- James B. Irwin (Apollo astronaut): "As we got further and further away, it [the Earth] diminished in size. Finally, it shrank to the size of a marble, the most beautiful you can imagine. That beautiful, warm, living object looked so fragile, so delicate, that if you touched it with a finger it would crumble and fall apart. Seeing this has to change a man."
- Mike Collins (Apollo 11 astronaut): "Oddly enough the overriding sensation I got looking at the Earth was, my god that little thing is so fragile out there."
- Edgar Mitchell (Apollo 14 astronaut):"From out there on the Moon, international politics look so petty. You want to grab a politician by the scruff of the neck and drag him a quarter of a million miles out and say, 'Look at that, you son of a b---.'" (People magazine, 8 April, 1974.)
- Ron Garan (ISS astronaut): "I returned to Earth after that first space mission with a call to action. I could no longer accept the status quo on our planet. We have within our grasp the resources and technology to solve many, if not all, of the problems facing our planet yet, nearly a billion people do not have access to clean water, countless go to bed hungry every night, and many die from completely preventable and curable diseases. We live in a world where the possibilities are limited only by our imagination and our will to act. It is within our power to change much – and yet we don’t."
- Carl Sagan (astronomer): "There is perhaps no better a demonstration of the folly of human conceits than this distant image of our tiny world." (Time magazine, 9 January 1995, after seeing an image taken of Earth by Voyager 1 spacecraft in 1990, the image known as Pale Blue Dot.)
- Carl Sagan: "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. The aggregate of our joy and suffering, thousands of confident religions, ideologies and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every "superstar", every "supreme leader", every saint and sinner in the history of our species lived there—–on a mote of dust suspended in a sunbeam."
It behoves every human being to look at images of the Earth from space, to read the testaments of the overview experiences of astronauts. To fully comprehend the miracle that the planet Earth is. To understand that despite Earth's strength as a planetary body, the health of its system as a whole is dependent on all of us coming together to make the right choices about our use of energy, resources and habitats, choices that affect not only human beings but all the many millions of other living beings this planet has given harbour to.
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