After the Big Bang

Between the Big Bang and before there was an Earth, there was activity.

I’ll admit, the Big Bang is one of those phrases I’ve picked up since graduate school with no understanding and little interest. Remember, in college, I’d already relegated all questions about the origins of the universe to that class whose answers led to more unknowns, and I’d accepted a level ignorance that was willing to stipulate - the Earth exists.

However, in Early Earth Systems, Hugh Rollinson has explained one consequence I find fascinating, the creation of the elements.

According to him, during the Big Bang the first three elements in the periodic table were created - hydrogen, helium, and lithium - along with the hydrogen isotope deuterium.

The hydrogen burned to produce helium at temperatures greater than 50,000,000c degrees.

The helium burned to produce carbon and oxygen at temperatures greater than 100,000,000c degrees.

The carbon and oxygen burned to produce the elements up to silicon in the table, including sodium, magnesium and aluminum. The stellar core had contracted and temperatures had risen even more.

The silicon burned to produce the elements up to iron at 1,000,000,000c degrees, then the process stopped. At that point, heat no longer was generated. The production of additional elements would have used energy. Sodium, potassium and calcium are in the range between silicon and iron in the periodic table.

Once the basic elements existed, they fell into three categories:
* Gases - hydrogen, helium
* Ices - water, methane, ammonia, nitrogen
* Rocks - magnesium-iron silicates

The first are essentially from the first phase of element creation.

The second group uses products from burning helium. Water is oxygen and hydrogen. Methane is carbon and hydrogen. Ammonia is nitrogen and hydrogen. Nitrogen falls between carbon and oxygen in the periodic table.

The rocks come from the third and fourth phases.

The ice, gas and dirt were circulating in a circumstellar disk where temperatures were falling. When they reached 700c or 1420F the iron began to become magnetic.

When the overall temperature fell into the range of 227c to 527c, the iron-magnesium silicates and iron-nickle began condensing.

Within the next 10,000 years, the small grains were kept buoyant by the gases, and began accumulating through nongraviational electromagnetic forces.

Then, when enough atoms had changed, gravitational forces took over. By the end of a million years, larger clusters (planetesimals) formed into planet embryos, a process that continued until all the material was absorbed into a larger body.

At that point, the gas had been dispersed, and no longer acted as a cushion between the embryos. They began colliding with one another which produced energy (heat) which began melting the material.

At the end of 100 million years the planet was formed, roughly 4,537 million years ago. The segregation of iron from silicon continued to form the core which was complete about 4,535 years ago.

Notes: See entry on Earthly Beginnings for 22 November 2011 for core formation and the role of temperature and iron in the process.

Rollinson gives temperatures in Kelvin which are 237 degrees greater than Celsius, a meaningless difference at these temperatures; you could even think of them as Fahrenheit without loss of meaning.