Clem Sunter

How old is my planet and how long will it last?

2013-08-02 14:08

Clem Sunter

When I give talks on the future, occasionally a question at the end poleaxes me. A mother in the audience brought her young son up to the podium the other day and said he was dying to ask me something. I was all ears. He looked at me quizzically and then launched the missile: "My mother tells me you look far ahead into the future. How old is my planet and how long will it last?" Just for good measure he added: "I am talking about life on Earth as well as the ground under my feet."

At the time, I ran for cover with a fairly vague answer along the following lines. The universe started with a Big Bang billions of years ago out of which our planet along with other stars and planets were formed. Life, and in particular human life, came later and will continue until our sun develops into a red giant which will cause such a change to the solar system that life as we know it will probably cease. That, however, is also in billions of years time so you need not worry about life ending in your own lifetime or that of your kids or grandkids! Planet Earth will then survive empty until the expanding sun envelops and consumes it.

However, the lad's question preyed on my mind and, like we all do these days, I resorted to the internet for more precise answers. First, I looked up the history of the universe and here it is. We have had 13.8 billion years since the Big Bang while the age of the Earth is 4.5 billion years. Life started 3.55 billion years ago and multicellular life started around one billion years ago. Mammals have a history of 200 million years, great apes 20 million years and anatomically modern humans 200 000 years.

As for the future, you must google "when will life end" and you will come across a fascinating article written by Hayley Dixon on 2 July this year in The Telegraph. The gist is that, barring a catastrophe such as cosmic bombardment from an asteroid or comet, a gigantic supernova or a sudden tectonic shift in the Earth's crust, life will begin to fade away in one billion years according to a recent scientific study. The reason is ironically that there will be too little carbon dioxide for photosynthesis of plants due to greater evaporation as the sun grows hotter. Herbivores will go extinct followed by carnivores which prey on them. Microbes will be left but after a further billion years even they will die out as the oceans completely dry up. So the end of life is scheduled for 2000 002 013 AD. The end of the Earth could be as far away as 7.5 billion years.

In order to put all this in perspective, let us assume a year is a second. There are 31.5 million seconds in a year. Thus the age of the universe on this assumption is 438 years and the age of the Earth is 143 years. Life started 112 years ago and multicellular life 32 years ago. Mammals have been around for 6.3 years, apes 230 days and humans 2.3 days. Life will end in 63 years and the Earth in 238 years time. In other words, we are nearly two-thirds of our way through life of any kind but the ground under our feet still has almost two-thirds to go. Spare a thought too that we as humans have been around for 2.3 days and have already disturbed the planet's environment.

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