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Such a difference in season could also result in drastically different global climates, where one is habitable by humans and the other isn’t.
Eccentricity is less obvious to the casual observer but
easy to observe with a telescope suitable for solar
observations (that is, has a proper solar filter). If you
observe the sun in January, it will appear larger than
the same observation in July (see Figure 3).
While tilt and eccentricity are discernable from shortterm observations, precession requires long term
Figure 2 Above : Earth today with a hypothetical
Earth having a 90 degree tilt (not to scale)
Figure 3: Apparent difference in the size of the
sun at aphelion and perihelion (orbit is not to
scale)
ICY SCIENCE | QTR 1 2014