Why do days get longer in the summer?
(Lansing State Journal, May 15, 1996)


The first astronomers thought they could keep time by following how long it took the sun to go from one high noon to the next.  However, they soon realized the sun is not a good time keeper because the length of time it takes to do this changes with the seasons.

The Earth is tilted as it moves around the sun.  It rotates around the sun every 365.25 days and spins on its axis once every 24 hours.  The Earth’s axis, a line extending from the Earth’s north and south poles is tilted 23.5 degrees.  As the Earth reaches a particular point in its orbit about the sun, the northern hemisphere tilts towards the sun while the southern hemisphere tilts away from it.  The imaginary line that divides the Earth into the northern and southern hemispheres is the equator.  Michigan is in the northern hemisphere.  The season when we are tilted toward the Sun is out summer.  During our summer, the daylight lasts more than 12 hours because the sun is at it’s northernmost position from the equator.  During winter, daylight lasts less than 12 hours for the north because the sun is at its southernmost position from the equator.  The farther north from the equator you are, the shorter the daylight hours.

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