13 December 2009


(Note: click on any image to enlarge) I was thinking about plate tectonics, the well-proven theory describing the division of the earth's lithosphere (crust and upper mantle) into distinct solid plates, which float convectively upon the hotter, deeper, liquid asthenosphere (termed visco-elastic -- think lava), not unlike icebergs floating on the ocean's surface.

Tectonic plates are categorized as being continental or oceanic, depending upon whether their surface is higher or lower than sea level. Unlike the iceberg analogy, however, tectonic plates are jammed together and in constant motion, with new material being formed constantly by upwelling molten rock along mid-oceanic ridges, driving the plates apart. in the convergent boundaries where plates are forced together, they either collide directly, with one plate being forced beneath the other (a collision which forms mighty mountain ranges like the Rockies and the Himalayas), or they collide indirectly, traveling like passing cars, rubbing together to produce earthquakes and/or volcanos, e.g. the Pacific Ring of Fire.

Tectonic plate movement is relatively slow -- ranging from 10-40 mm per year (about as fast as fingernails grow), up to 160 mm per year (about as fast as hair grows).
So even when we're standing still, we are in motion. This set me thinking in the other direction, from down to up. Here we are, standing on the earth's surface, apparently motionless. But if the earth's atmosphere were completely stationary relative to the surface, we would immediately sense our rotational speed by the relative wind -- about 1000 miles per hour at the equator. So motion is compounded upon motion, and we're not even taking a step in any direction.

That's not all. The earth is revolving around the sun, covering its orbit in a year by traveling at a leisurely 1,600,920 miles per hour.

Further, the entire solar system is part of the rotating Milky Way galaxy -- our speed around the galactic center is very roughly 1,296,000 miles per hour.

All without moving a muscle.

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