|Origins of life|
Almost everywhere you look on earth, there is life. Although it is not always visible to the unaided eye, it is most likely there. From the micro-organisms living on the computer screen you are looking at now, which are too small to see, to the animals in forests, to the animals of the ocean. But how did life begin on earth? Where did it all come from?
Early on in Human existence, people had little scientific understanding of the world around them. They believed that a God or Gods created the universe, earth, life, and everything around them. This theory seemed flawless, as if there was something that could not be explained, they assumed that god was behind it. (There may or may not be a God. This website is not concerned with that, however. It is concerned with scientific explanations. As Humans evolved their scientific understanding, and discovered more and more about life, other theories came up to explain the origins of life.
One theory is that life came to earth from another planet. In 1884 a Swedish scientist, named Svante Arrhenius proposed a theory he called 'Panspermia'. He calculated the possibility that micro-organisms could be blasted into space by volcanic eruptions and planetary air currents. He then proceeded to calculated that micro-organisms would be pushed through space by pressure exerted by the sun's light rays. He calculated that in only 14 months, a micro-organism could be pushed out of our solar system, and would reach our nearest neighboring star, Alpha Centauri, which lies 4 light years from earth, in only 9 000 years. Arrhenius proposed that this is how life may have reached earth.
This however does not seem very likely, as we know of no life forms which can survive the extremes of space: Either very high or very low temperatures, immense radiation, etc. v
The British astronomer Sir Fred Hoyle proposed that life ejected into space mixed with spacial dust, and eventually became mixed into meteors, which would protect the life, and create an environment where the life could reproduce. But, when meteors enter the earth's atmosphere, they are engulfed in a ball of flames, and only occasionally, in the case of large meteors, does something survive to strike the earth's surface.
Although these theories are credible, they do not solve the problem of how life originally began. The theory which is currently most accepted by the scientific community is that life formed on earth from non-organic compounds and base elements, which formed organic compounds (compounds containing carbon (C), hydrogen (H) and oxygen (O) ), and eventually cells.Next: The First Cell
Home | Formation of the Earth | Earth's Structure | Life on Earth
Life on Earth: Origins of Life | The First Cell | Evolution of Life
Copyright 2000, ThinkQuest team C003124
All rights reserved.