Posted
on January 8, 2015
I
know what you're thinking: isn't EVERY day Earth's Rotation Day?
Isn't
that literally what day means? (Day = 24 hour period
corresponding to one rotation of the earth on its axis.)
And
you would be exactly right. I suppose today is the day to actually
acknowledge that rotation!
You
probably know that most people in the far past thought of the Earth
as the one stable, unmoving thing in the cosmos. You know, the thing
that is rock solid and firm beneath our feet! Everything else—Moon,
Sun, stars, nebulae, and planets—seemed to be moving around Earth.
Most of these things seemed to slowly wheel across our skies at one
consistent pace...But the consistent pace was of course the speed at
which the Earth was spinning!
 |
| Sun up and sunset are of course REALLY just the world spinning. Ditto "day" and "night." |
(As
it turns out, everything in the universe is rushing around at really
amazing speeds. Earth is not only spinning on its axis, it is also
orbiting the Sun. Our solar system is part of the Milky Way Galaxy's
giant pinwheel rotation, and the galaxy is rushing away from all the
other galaxies. A lot of motion in this cosmic ocean!)
Here
are some questions to consider:
- What would happen if the Earth's rotation were to gradually slow down?
- What would the planet be like if the Earth didn't rotate on its axis but still orbited around the Sun?
- The Earth could (probably) never ever suddenly stop rotating on its axis, but what would happen if it did?
Think
about that for a while....
Here
are some answers:
- If the Earth's rotation (spinning) were to gradually slow down, the day would get longer and longer.
Actually, the Earth's rotation IS gradually slowing down! The day is longer now than it was in the distant past! Not necessarily a lot longer, though. Scientists have discovered that a modern day is 1.7 thousandths of a second longer than a day a century ago.
The Earth's rotation is gradually slowing because of the tidal friction caused by the Moon pulling on the Earth, kind of dragging at it. How it works is that the orbital momentum is being transferred from the Earth to the Moon, and the Moon is slowly receding from the Earth (about four centimeters a year).
If
the Earth didn't rotate on its axis, a day would be as long as a
year. Let's say the Earth slowed its rotation all the way down to a
standstill. If that happened, the oceans would migrate to the poles,
and the Earth would have one huge equatorial mega-continent and two
polar oceans. Take a peek at this website
for more on this scenario.
If
the Earth was to suddenly stop spinning, everything else would still
be in motion at the same 1100 mile per hour speed that the Earth now
rotates. So everything on the surface – including all the water
and air and animals and people – would be suddenly moving SIDEWAYS
to Earth, and the land surface would be scrubbed clean of anything
not attached to bedrock.
Also
on this date:
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ahead:
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