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One Man's Summer is Another Man's Winter
As we roll into July in the northern hemisphere and begin to strain our air conditioning
systems, it's hard to believe our neighbors to the south are hunkering down for
a long winter's night. At around midnight on July 5-6, the Earth reaches aphelion
- the point in its elliptical orbit the farthest from the sun - at around 94½ million
miles. The apparent brightness of the sun is reduced to about 93% of its level at
perihelion - around 91½ million miles away. Now, it hasn't always been this way,
nor will it be so in the future. Seasons of course, are caused by the 23½ degree
tilt of the Earth's rotational axis relative to the ecliptic plane. Gyroscopic precession
causes the axis of rotation to cycle ever 26,000 years. So, in 13,000 years, aphelion
will occur near the winter solstice in the northern hemisphere. Hmmmm, I wonder
if this natural cycle contributes to the apparent heating and cooling eras in the
Earth's history that some like to blame entirely on recent human activities?
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