Week of Sept. 20-26, 2009 by Dennis Mammana on Creators.com

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Week of Sept. 20-26, 2009

I don't know about you, but I'm always a bit sad to see summer end. True, where I live in the Southwestern desert, summers can become so blistering hot that even the lizards rent RVs and head to Minnesota for relief.

But autumn is on its way, bringing with it shorter days and pleasant temperatures.

This whole seasonal business comes about because our planet's axis is tipped 23.4 degrees to our orbit around the sun. This causes sunlight to fall more directly onto one hemisphere than the other at various times of the year.

The moment that our sun "crosses" the equator from north to south — in other words, when it illuminates both hemispheres equally — marks the "autumnal equinox." It occurs this year on Sept. 22 at 2:19 p.m. PDT (5:19 p.m. EDT).

Watch the position of the mid-day sun throughout the year and you will see one manifestation of this annual change.

Over billions of years, life on our planet has adapted to these seasonal changes. But suppose our world had no tilt at all? How might life on Earth be different?

With no tilt, climate at each location on Earth would be fairly stable and flora and fauna might become quite specialized.

Creatures of varying sizes and types might intermingle more, and the ecology of the Earth would be noticeably different than it is today.

And if our planet's axis were tilted more? Seasonal changes would be extreme. Strong winds and powerful storms would be more prevalent. Most locations would experience hot tropical summers and hostile arctic winters. Massive polar ice caps would form during winter and melt during summer, changing sea levels by more than a hundred feet every six months.

Land masses where life could evolve would shrink; less of our planet's surface would remain for long periods at a temperature conducive to life; and even less would have seasonal variations moderate enough for life to develop successfully.

Life forms that did manage to evolve on land would need to be quite mobile to cope with these stark seasonal changes. Animals would have to migrate huge distances to survive, and most would be prone to extinction if anything should block their movement.

So, while it might seem sad to bid adieu to the summer of '09, we must remind ourselves to relish the changes that are coming our way. We owe to them our very existence.

To find out more about Dennis Mammana and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at www.creators.com.