How long did it take for the earth to cool and how long?

Question

after that did the evolution of the dinosaurs start to happen and how long were they on this earth. Then after that how long did the evolution of humans start to happen (were there any other intelligent species in between)

Answer 1

Wnen the Earth started to form, from the coallescing of rocky material as the solar system formed, it contracted under the force of gravity into the not-quite spherical shape it is today.  Compress anything, and it heats up.  Compress something the size of the earth, and the heat of gravitational compression was so great, that the internal heat grew to several thousand degrees; enough to melt the material at the centre.  The heavier iron and nickel migrated to the centre; hence the earth now has a molten iron-nickel core (the compression is so great at the inner core, that it is solid; despite the great temperature).  

Around the core, is a mantle of rock, and above that a thin lighter silicious crust.  The outer layers insulate the hot centre well; and heat is also continuously produced by natural radioactive decay of uranium; so the net effect is that the earth's core is cooling very sligfhtly; only a degree every hundred thousand years or so.

But the earth's basic structure (molten metal rich core, rocky mantle and lighter crust) became fixed  shortly after its formation, three or four billion years ago; and long before the age of the dinosaurs.(about 100 million years ago).

Humans have been around for a very short time; compared to the age of the earth.  If you compared the age of the earth to a twenty-four hour day, then the earth's structure was in place by about 2am, life began to appear around midday, the dinosaurs were around about two minutes before midnight, and humans appeared about two seconds before midnight.

The earth will be around for another few billion years yet, until the sun expands to a red giant star and burns the earth to a crisp.  This won't happen for another four billion years or so yet, so we won't have to worry about it..  Using the twenty four hour analogy again; the earth is about half way through a two day cycle.

Answer 2

The Earth has not completely cooled down, that is why there are still active volcanoes around.

But I presume you mean cooled to a point where a crust could exist. Some rock samples were found that are consistent with the presence of a liquid ocean 4.3 billion years ago, thus about 200 million years after Earth's formation.

Dinosaurs were rather late arrival, since they appeared only 230 million years ago (there were other, more primitive life forms before, evidently, since life on Earth started 3.8 billion years ago, but was limited to bacteria for quite a while, it took 2.5 billion years for life to move to multi-celled organisms).

It is assumed that the path to humanity started about 2.5 million years ago, with creatures that were not much more than apes and that we'd have a hard time telling from some strange looking primitive chimps.

Other intelligent species before humans? If there were, they did not leave anything that would indicate they were around, so until proven otherwise, we'll assume there weren't.