They say that if time was a 24 hour clock, that we hominids have been around for a little over a minute to say 8 minutes. Springing into existence between around 11:52:48 to 11:58:43 pm in the Miocene period. So with that perspective, just how old exactly is the Earth? Let’s explore this, and other questions below!
Formation And What Came Before
In human years, the solar system is old. The planets and other objects in the solar system were formed about 4.571 billion years ago, when the sun was just beginning to form. At first, there was just a big cloud of gas and dust. Something caused this cloud to collapse and form a swirling solar nebula. Eventually, gravity pulled this solar nebula in tighter and tighter forming a dense core area that became our Sun, and our Solar System was born.
Since then, the solar system has evolved and changed, with the planets forming, and interacting with each other. The solar system today is a much different place than it was when it was first formed. It will continue to evolve and change over the course of the Sun’s lifetime.
The Universe formed around 13.77 billion years ago, and our Solar System formed around 4.571 billion years ago. The Earth did not come along until around 4.543 billion years ago. At roughly a third the age of the Universe, and a good 28 million years younger than the Solar System, there was plenty going on before the Earth came into being.
In terms of the Solar System, the first thing to form was a solar nebula, from which the Sun was born. The bulk of the remaining dust and matter further out in the system eventually became the planets, dwarf planets and moons that we know today. The remaining matter that did not form into planets exists out there in asteroid belts and fields of debris.
The Earth as we know it today is a relatively young planet, having started to form around 4.543 billion years ago. In its infancy, the Earth was a very different place. It started to form when debris left over in the solar nebula after the Sun formed, started to clump together and collide. These collisions and the accumulation of mass generated massive heat and caused these big rocks to fuse together. Gravity pulled the heavier material to the center, and eventually a planet, with a core was formed. 
How Old Is The Earth?
The Earth is around 4.543 billion years old – give or take 50 million years. But life, and in particular complex life is much, much younger than that.
In the 1950’s at Cal Tec in the USA, a geochemist by the name of Clair C. Patterson measured the age of many meteorites and space rocks that were believed to have come from the same disc of dust and matter from which the Earth had formed. Through measuring the isotopic composition of lead in these rocks, he came to a conclusion that the Earth was around 4.5 billion years old. This estimate has changed only marginally since it was calculated in the 1950’s. More rocks from the moon have since been examined using a similar process that back up this measurement.
Life On Earth
One of the best and most frequently used methods to illustrate the age of the Earth, and the timeline of events is to use the 24 hour clock method. Where the timeline of the Earth, from formation to present day is given as a full 24 hour day and events are marked along the hours and minutes where they have occurred along the way.
In this method, the most simple forms of uni-cellular life begins to appear around 4 am on the clock. Little else changes in terms of life forms until around 1pm where the first eukaryotes start to appear. That’s half of Earth’s existence already, and only the most simple forms of life have developed.
Around 5.30 pm the first multicellular life starts to appear. But it’s not until after 10 pm that life starts to emerge from the water onto land. The dinosaurs arrive around 10.45 pm, mammals not until around 11.40 pm! It is not until around the last two seconds of the day that modern humans arrive on the scene. In the last two seconds every moment of human existence has taken place. That’s some mind bending perspective!