Tilting of axis necessary for life?

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Offline Bill.D.Katt.

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Tilting of axis necessary for life?
« on: 14/11/2010 04:02:57 »
Is the axial tilt of a planet, which induces seasons, necessary or beneficial to the formation of life on a planet? If so, to what extent?


Offline chris

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Tilting of axis necessary for life?
« Reply #1 on: 14/11/2010 10:12:59 »
Hi Bill

The Earth's axial tilt, also known as the obliquity, is currently 23.4 degrees; this changes over long timescales (of about 40,000 years) because the Earth "wobbles" a bit during its orbit. In the past it has ranged between 22.1 and 24.5 degrees.

As you correctly point out, year on year the effect of this tilt is to trigger seasons. These occur because the amount of time a part of the Earth's surface is illuminated by the Sun changes, and this alters the energy input and therefore the temperature.

But these seasons in themselves will not, in my view, necessarily make life on Earth more likely, although they will certainly increase the diversity of life on Earth as more species evolve to exploit the many niches created by the changing weather that results from the changing seasons.

What is more important to life on Earth is the overall long-term stability of the ecosystems that life has evolved to occupy. Therefore keeping the obliquity within relatively tightly constrained bounds - thus keeping the climate on Earth stable over the long term - is the key, and we have the moon to thank for that. Orbiting the Earth as it does, it helps to keep the planet more or less "upright", which prevents dramatic, rapid departures from the status quo.

I never forget a face, but in your case I'll make an exception - Groucho Marx