David Aguilar (617) 495-7462
Christine Pulliam (617) 495-7463
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What's New: The Solstice
 

The June Solstice occurs at 6:51 am EDT on June 21. But what exactly does this mean, and why is it important?

As the Earth rotates, its axis always points in the same direction relative to the background stars. Its axis extended northward points to the North Celestial Pole near the star Polaris in the constellation Ursa Minor; its axis extended southward points to the South Celestial Pole, near the rather inconspicuous star Sigma Octantis. However, this axis is inclined by about 23.5° to the plane of Earth's orbit around the Sun. As a result, the area of Earth's surface most exposed to the Sun varies as our planet, traveling in this plane, makes its annual trip around the Sun. The area most exposed to the most direct rays of light from the Sun gets the warmest: it experiences summer. The area getting less of the Sun's direct rays experiences winter.

Six months later, the positions of these areas with respect to the Sun are reversed, as are the seasons.

Solstice
The Earth and Sun on June 21 - the June, or "Summer," Solstice (click image to enlarge*).

On June 21, the Earth's Northern Hemisphere is most tilted towards the Sun and experiences summer. Though this is commonly referred to as the "summer solstice" it is, strictly speaking, summer only in the Northern Hemisphere; the Southern Hemisphere is experiencing winter.

Solstice
The Earth and Sun on December 21 - the December, or "Winter," Solstice (click image to enlarge*).

On December 21, the Earth's Southern Hemisphere is most tilted towards the Sun and experiences summer. Though this is commonly referred to as the "winter solstice" it is, strictly speaking, winter only in the Northern Hemisphere; the Southern Hemisphere is experiencing summer.

Solstice
The Earth and Sun on September 22 - the September, or "Fall," Equinox (click image to enlarge*).

On September 22, each of Earth's hemispheres is equally exposed to the Sun's rays. This marks the beginning of fall in the Northern Hemisphere and of spring in the Southern Hemisphere.

Of course, there is a corresponding equinox on March 20th, which marks the beginning of spring in the Northern Hemisphere and of fall in the Southern Hemisphere.

It is worth noting that the Earth's seasons are caused by this axial tilt rather than the planet's distance from the Sun.

In any case, enjoy the weather you have!

 
 

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