Birth of Earth

The beautiful Eagle Nebula

In my last post I described the dying of a huge star in a spectacular supernova explosion that spewed out chemically enriched dust and gases that formed a nebula cloud out of which a solar system like ours emerge. It is because astronomers have studied new solar systems in various stages of evolution, that we now have well accepted theories about how our own developed.   

Apparently, under the force of its own gravity the portion of the nebula cloud from which we came into being, contracted over a period of around 10 million years or so and, as it shrank, material was drawn in from space around it. The increasing amount of matter resulted in a larger gravitational pull and made material speed inward ever faster. When this mass smashed into the center, its energy of motion was transformed into heat energy and the temperature increased until it reached around 15 million degrees. At that temperature, the nuclei of hydrogen atoms are moving so fast that when they collide, they fuse forming Helium nuclei and give off incredible amounts of heat and light energy. That is the story of how our sun was born in our corner of cold dark space. The marvelous process by which stars are created is more fully illustrated in a posting I did on the sun a couple of years ago.

In the process of its formation, the sun had pulled in 99.86% of the matter in its vicinity and the slight rotation of the nebula cloud had speeded up so that the remaining 0.14% of matter  formed into planets that had just enough speed that they didn’t fall into the sun but orbited around it. As the planets grew by sweeping up the all the dust and rocky debris in their orbits, the birth of the sun sent out a blast of solar wind that cleared out all the remaining dust and rubble. 

Click on picture to enlarge & read the
thickness of the layers of Earth's interior

It’s interesting to have a look at the video simulation of all of this happening.  The video also depicts the Earth  in its early years when it was a molten mass and the heavy liquefied iron-nickel alloy sank to the center. Not mentioned is that the Earth’s mantle is kept molten by radioactive elements like uranium that give off heat as they decay. The story of the cooling of our planet and how our continents formed is told in some detail in an earlier post about the ‘Earth’s Crust’. 

Earth turned out to be the only one of the eight planets in our solar system that was at just the right distance from the sun to have a temperature range suitable for life. It has been speculated for years that there are other planets like ours in the Universe but it is the recent detection of billions of new planets that sparked my interest in going back to the very beginning and writing about the spectacular events that eventually produced our planet Earth. 

It is obvious that it has been a natural process and now, with the confirmation of so many other planetary systems, the probability that other intelligent beings exist becomes more real.  The problem is, with what we know of the Laws of Physics, it would take us at least 75,000 years to just reach the closest star similar to our own. That means we’ve no place to go if we don’t smarten up and keep our beautiful planet Earth habitable. For me it also increases the importance of the SETI  [Search for Extra-Terrestrial Intelligence]   program that searches for non-natural radio signals from sections of space outside our Solar System.  

Next week, if I find enough time to research it, the subject of my post will be what we know about how life started on Earth.  Rie

                                                                        

Alone in the Universe?

As usual my tendency is to look at things with a long perspective and scientific bent. However, it’s evident I’m not alone in wondering about the chances we’ll ever reach any form of life out there in the Universe. As is common knowledge, a radio call is being sent out through SETI – the global Institute whose purpose is to explore the ‘nature and prevalence of life in the universe’.

To answer that message, the life form on another planet would have to be advanced enough to understand it. Certainly we are unique on Earth in that we are intelligent enough to be logical and to communicate but it has taken most of the time since our planet was formed for us to have reached this level of complexity.

The fossil records are our main source of information on just what has happened during the evolutionary process. These scientific records tell us that:

- 4.6 billion years ago our planet was formed

- 3.8 billion years ago, life evolved in the form of single celled bacteria or microbes

- 0.53 billion [or 530 million] years ago bacteria got together to form multi-celled life forms and in a remarkably short period, many different species came into being in the so-called Cambrian Explosion

- 0.050 billion [or 50 thousand years ago] homo sapiens reached the modern form that could be recognized as us.

- 0.000,000,050 [or about 50 years] since radio became advanced enough to send messages out to the Universe. That has happened in the last very small fraction of time since the planet has existed.

If you consider that from our point of view on Earth, the sun has risen and set and the seasons have existed all those billions of years – in comparison to other planets, that makes ours a very rare and remarkably stable one. For this stability to occur we have had to:

- Be orbiting around a medium-sized, single sun in the outer reaches of our galaxy so as not to have been disturbed by other nearby suns.

- Be a planet that makes a circular orbit around the sun at just the right distance away to be in a good temperature range where most water was liquid.

- Be a planet spinning on its axis frequently enough (24 hours for us) so all parts were warmed in the day and cooled off at night. The axis had to be tilted so over a period of a year it wobbled and gave both hemispheres summer and winter seasons.

- Be fortunate enough to have a large moon that caught much of the debris during our planet’s early formative years.- There is much more about how rare our stable Earth has been if you click on the highlighted text.

Let’s try to always be aware how special and precious our planet is and do everything possible to prevent environmental deterioration so future generations can enjoy its beauty and bounty. Rie