THE ROSE CENTER FOR EARTH AND SPACE

     AMNH

The question came up yesterday, "How old is the earth and how long have modern humans been around?"  For those that may be interested I'll post my answers.

The Earth formed 4.5 Billion years ago.  It formed at the same time as our solar system and from something we call the solar nebula. Before the solar system existed, a giant cloud of gas and dust occupied our present space in the Milky Way Galaxy.  Something jarred this cloud and started it moving in a swirling motion. The heavier elements gravitated toward the center in a process we call differentiation, which simply means, that heavier elements will gravitate toward the center of a moving mass, leaving the lighter ones (usually gasses) to fill out the edges.

The sun formed first and from it's tremendous gravity the four inner rocky planets appeared. They were followed by the four larger gas giants. That's right, I said four and four. There are now only eight planets in our solar system not nine as we were all once taught in school. (Just goes to show how much and how fast our knowledge of science changes.) (Pluto is no longer classified as a planet in our solar system rather a  body that may have gone astray from the Kuiper Belt of Comets that circle just outside Pluto's orbit)

And so about 4.5 bya, our humble but extremely relevant solar system began. It is estimated that the sun still has another 4.5 billion years left before it expands, exhausts its fuel and turns into a brown dwarf.  So we still have some time. You can plan that vacation to the Grand Canyon.

As far as humans. Well there is much to say here. I will address my disgust and disappointment in the human race in blogs to come, but for now let's just talk about what we think we know. Modern Humans, what we refer to as the late Neandertals or Homo Sapiens, or what finally morphed into Homo Heidelbergensis and Homo Rhodesiensis is dated back to roughly 150,000 years. Though the earliest hominids date back to 6-7 million years with Australopithecus Afarensis. Recent discoveries are now dating hominids as far back as 7 million years. 

None-the-less we have caused more extinctions of life on earth than any other natural phenomena in our short egotistical existence and the extent of our legacy is still yet to be seen. More on this later.

Foo Non Kay say:  That is all for now.