Slice of (human) Life

Continuing on the rather gloomy theme on mankind’s place in the Universe, here’s a little summary I made of the Earth’s future from Ward and Brownlee’s “The life and death of planet Earth”


The planet is 4.5 billion years old will exist for about another 7.6 billion before being eaten by the Sun.

Modern humans (hom sap sap) emerged 200,000 years ago. (About 22 thousandth of the age of the Earth) and will be extinct within the next 15,000 to 80,000 years as the climate returns to Ice Age average.

On any reasonable scale of Earth’s existence humans don’t even get on the graph.


Goldilocks Earth

After 700 million years the meteor bombardments that created the Earth slowed down. The Moon was originally a lot closer to Earth. (It is still moving away.)

The Earth’s tilt moderates the temperature across the whole planet. The tilt is held stable due to the exceptionally large moon.

The combination of land and and sea allows the carbon cycle to regulate the planet’s temperature.

Without a biological ecosystem, free oxygen would disappear: oxidizing surface materials or forming nitric acid.

Free oxygen on Earth forms ozone. Which protects animals from from UV radiation.

Water is the 3rd most plentiful material in the universe. It came to Earth in meteorites and comets. (Back to the first line.)

(From The Life And Death of Planet Earth. Peter Ward & Donald Brownlee.)


Earth is 4.5 billion years old.
Life has existed for the last 3.4 billion years.
It is predicted the last animals will disappear in less than half a billion years from now. Life (diversity) on Earth is already in decline.

If 4.5 billion years was a 24-hour clock, then:

  • Complex life (Cambrian) doesn’t start until 22:00 hrs.
  • Dinosaurs start at 23:00 hrs.
  • – And Homo Sapiens have existed for 2 seconds.


If 4.5 billion years was a mountain as high as Everest.  My life is the height of the last snowflake at the top of the summit.

(From The Life And Death of Planet Earth. Peter Ward & Donald Brownlee.)