Tag Archives: Longfellow

It is the Harvest Moon!

Here in New England, the long summer has abruptly receded, and a series of cool nights have signaled the arrival of fall. The maples, among the first to sense the changing seasons, have slowed their production of chlorophyll, and the first bright colored leaves have begun to peek through the canopy. This year, the changing of the seasons is coupled with a unique combination of astronomical events: Sunday’s full moon, the Harvest Moon, will additionally be both a supermoon and a “blood moon” lunar eclipse. These terms seem ripe for poetry on their own. But what do they really mean?

It is the Harvest Moon! On gilded vanes
And roofs of villages, on woodland crests
And their aerial neighborhoods of nests
Deserted, on the curtained window-panes
Of rooms where children sleep, on country lanes
And harvest-fields, its mystic splendor rests!

Henry Wadsworth Longfellow’s poem, “The Harvest Moon,” depicts a still nighttime scene presided over by a Harvest Moon, in all its “mystic splendor.” The term “Harvest Moon” is applied to the full moon closest to the autumnal equinox. The Harvest Moon, which usually occurs in September, historically allowed farmers to continue their harvest into the night. Other, related, names for the September full moon include the Barley Moon and the Corn Moon.

The Harvest Moon is special for another reason. At the time of the Harvest Moon, the moon rises at about the same time for several nights, making it seem like the moon is full multiple nights in a row. This occurs because of the angle of the moon’s orbit relative to earth’s. Because the moon’s orbit is offset from earth’s orbit, the moon usually rises about 50 minutes later each successive night (that is, the time between sunset and when you see the moon increases by about 50 minutes from night to night). But around the time of the autumnal equinox, the moon’s orbital path makes a shallow angle with the horizon, so for a few days before and after the harvest moon, the moon rises only about 30 minutes later than it did the previous night. This happens around sunset, so what we see is a large, bright moon lingering around the eastern horizon just as it gets dark.

In 2015, our Harvest Moon is even more special than usual. This year, it is also a supermoon lunar eclipse, a phenomenon that hasn’t happened since 1982 and won’t happen again until 2033.

A supermoon is caused by the shape of the moon’s orbit. Because the orbit is elliptical, sometimes the moon is closer to the earth than other times. At its closest approach to earth, called perigee, the moon is about 31,000 miles closer to us than when it’s at its farthest point, called apogee. If a full moon coincides with perigee, we call it a supermoon because its proximity makes the moon look about 14 percent larger and 30 percent brighter than a normal moon, according to  NASA.

Which brings us to the “blood moon” lunar eclipse. A lunar eclipse occurs when the earth lines up between the sun and the moon, blocking the sun’s light from falling on the moon. In the shadow of our planet, the moon appears reddish.

lunar-eclipse-diagram-1012-02

If the earth didn’t have an atmosphere, the moon might appear completely dark during an eclipse. Instead, sunlight bends around the earth and is filtered through the atmosphere, which removes blue light but allows red and orange light to reach the moon’s surface. What we see when a lunar eclipse is at its peak, is a blood-colored moon.

On Sunday, if the weather is clear, we should see a huge, bright moon that appears red for a few hours while it is eclipsed. Stand out in its light to celebrate, or mourn, the end of summer. The birds are leaving, the leaves are falling, and the chill wind wraps us as we reap whatever harvest this year has brought to us.

Gone are the birds that were our summer guests,
With the last sheaves return the laboring wains!
All things are symbols: the external shows
Of Nature have their image in the mind,
As flowers and fruits and falling of the leaves;
The song-birds leave us at the summer’s close,
Only the empty nests are left behind,
And pipings of the quail among the sheaves.

REFERENCES

“The Harvest Moon,” by Henry Wadsworth Longfellow. Read it here.

Byrd, Deborah. 2015. “Everything you need to know: Super Harvest Moon of 2015.” EarthSky. Link.

Morrow, Ashley. 2015. ” NASA Scientist Sheds Light on Rare Sept. 27 Supermoon Eclipse.” NASA. Link.

Palmer, Katie M. 2015. “Here’s Where to Watch the Supermoon Eclipse Online.” Wired. Link. 

“Why a Totally Eclipsed Moon Looks Red.” 2015. EarthSky. Link.

A Wilderness of White

Photograph of a natural snowflake captured with a  specially designed snowflake photomicrograph.  Photo: snowcrystals.com

Photograph of a natural snowflake captured with a specially designed snowflake photomicrograph. Photo: snowcrystals.com

“How full of creative genius is the air in which these are generated!  I should hardly admire more if real stars fell and lodged on my coat.”
 -Henry David Thoreau
 

In the northeast, winter is a season of cold.  It is a time when outdoor activities are dictated more than ever by the weather.  As children, snow is the stuff of dreams.  It can be mounded, piled, thrown, shaped, dug out, eaten, colored, ridden on, and experienced in a million ways.  As if that isn’t enough, the enduring hope of snow day is ever present, and the moment when you first wake up to that brightness of reflected sunlight through your windows, when you wake up and know it will be a day for only fun, is the lightest feeling in the world.  As adults, snow is polarizing: you love its beauty or hate its inconvenience.  Everyone has heard that every individual snowflake is unique.  But is this true?  And if so, why?

“Out of the bosom of the Air,
Out of the cloud-folds of her garments shaken,
Over the woodlands brown and bare,
Over the harvest-fields forsaken,
Silent, soft, and slow
Descends the snow.”
-Henry Wadsworth Longfellow 
 

First off: a definition of terms.  Snowflake is a more general term, and can refer to an ice crystal, a single crystal of ice, or to larger clumps of ice crystals that fall in agglomerations.  An ice crystal is not a frozen raindrop.  Liquid water that freezes and falls to the ground becomes sleet.  Rather, ice crystals are formed when water vapor in the clouds condenses directly into ice.  As you may (or may not) remember from chemistry class, ice crystals, each molecule of which is made of an oxygen atom and two hydrogen atoms, form what is called a hexagonal lattice.  The six-sided symmetry of this lattice is what gives snowflakes their six-sided symmetry.  Elaborate patterns emerge as the ice crystals grow in the clouds.

The most basic form of a snow crystal is a hexagonal prism, which includes two basal facets and six prism facets.  Different shapes can occur under different conditions, and the form of a snowflake depends very heavily on temperature and humidity.  The growth of these crystals relies on a balance between branching and faceting.  Branching is due to a property of water molecules and the way they travel through the air: they must diffuse, and thus the surface of a crystal a water molecule reaches first is the one one which it condenses.    A small bump on an otherwise-homogeneous structure is thus more likely to result in a crystalline branch, and once a branch has formed, it is more likely to grow longer.  Facets, on the other hand, are due to the fact that some surfaces of ice crystals grow more slowly than others.  Unlike a bump on a crystal surface, inviting a water molecule to bond, the flat surface of a facet is more likely to remain smooth because there is nothing for the water molecule to attach to.  Therefore, this surface grows more slowly.

Below, see a general guide for the most common forms of snowflakes:

types of snowflakes

For all that we understand about crystalline structure and how ice crystals form, there is even more we don’t know.  Why do the most complex shapes form at high humidity?  Why do the shapes of snowflakes go from plates to columns as the temperature lowers?  Usually, each arm of a snow crystal is different from its other arms.  Air current turbulence causes this: as crystals are blown about, water molecules can condense unevenly as each corner of a snow crystal experiences a different environment in the atmosphere.  So there is truth in the unique design of snowflakes, and it is ultimately due to the randomness of nature, building a snow crystal as it is spun and whipped through the air inside a cloud.  John Hallett, director of the Ice Physics Laboratory in Reno, NV, explains that, “[A snowflake’s] final shape is a history lesson of how the thing grew.  The outside edge of the crystal is where it grew last, and as you go inward you can tell where it was before.”

“Before I melt,
Come, look at me!
This lovely icy filigree!
Of a great forest
In one night
I make a wilderness
Of white”
-Walter de la Mare
 

The winter has come, and with it, the cold.  Snow has been sparse in this part of the country the last few years, and all we can do is watch and wait.  Will we awake tomorrow morning with the light bright and snow-shattered through our windows, with a kiss of frost on the glass from a storm like those when we were children?  If so, take a minute and think about how these amazing ice creations came to be.  And then go make a snowman.

REFERENCES:

Griffin, Julia 2011.  The science of snowflakes, and why no two are alike.  PBS Newshour.  Link.

SnowCrystals.com.  Kenneth G. Libbrecht 1999.  Caltech.  Link.

“Snow-Flakes,” by Henry Wadsworth Longfellow.  Read it here.

“Snowflakes,” by Walter de la Mare.