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What is an Equinox?

Today is the long-awaited spring, or vernal, equinox for folks in the northern hemisphere.  If you’re one of the 99.9% of people who are sick of winter then this is fantastic news.  In the Mid-Atlantic we’ve had one hell of a winter!  For three months it was just snowstorm after snowstorm and lots, I mean lots, of cloudy skies.  We also had the polar vortex swing by twice dropping temperatures into the single digits with sub-zero wind chills.  I think it’s fair to say that I am not alone in saying “Sayonara winter!”

The beginning of spring is officially today at 16:57 UTC or 12:57 EDT.  Why the exact time?  Well that’s because the changing of the seasons on Earth is indicated by the tilt of our planet.  As you might know the Earth orbits the Sun in a slightly elongated oval-shaped orbit.  Somewhat counter-intuitively it is not our position in our orbit that changes the seasons.  Did you know that Earth’s closest point to the sun actually occurs in early January?  Likewise Earth is furthest from the sun in the summer time.  It is actually how the Earth is angled with respect to the orbital plane that determines what season it is.  As the Earth orbits around the Sun it also spins causing day and night to come and go.  This rotation occurs around the Earth’s axis which is tilted about 23 degrees.  Throughout each year the Earth “wobbles” as it goes around the sun thanks to the inclination of the Earth’s axis.  When the Earth is tilted a certain way in respect to the Sun we call it an equinox.

The tilting of the Earth's axis throughout the year causing the seasons to change.

The tilting of the Earth’s axis throughout the year causing the seasons to change.

Equinox is a Latin term that means “equal night”.  During an equinox day and night are approximately the same length.  When an equinox occurs the plane of the Earth’s equator crosses the center of the Sun so that the Earth is neither tilted away or towards the Sun, causing an equal amount of sunlight to shine on both the southern and northern hemispheres.  As you can see from the incredible video below the day/night line (called a terminator) moves throughout the year if seen from space.  During an equinox the terminator is completely vertical.  In the case of the spring equinox the northern hemisphere has been angled away from the Sun for several months and thus has been receiving less direct sunlight and shorter days.  After the winter solstice during which the northern hemisphere experiences its shortest day the Earth begins to angle itself to point the northern hemisphere back towards the Sun resulting in longer days and more direct sunlight…summer!

This video is really hypnotizing.  What you’re seeing here is quite fantastic.  The video was taken using images from NASA’s Meteosat satellite.  Meteosat is a geosynchronous satellite which means it orbits around the Earth at the same speed as the Earth’s rotation so it always sees the same part of the planet.  As a result the planet never seems to move throughout the year.  In this video courtesy of Astronomy Picture of the Day and NASA, you see an entire Earth year in just twelve seconds!  You notice that the Earth’s terminator swings back and forth.  That is the seasons progressing as the Earth tilts on its axis.  The video begins on an autumnal equinox in September 2010 then the terminator swings over to the right giving the southern hemisphere lots of direct sunlight.  It reaches the solstice then swings back the other way towards the spring equinox when the terminator runs from north pole to south pole before swinging to the left and giving the northern hemisphere more light.  The video ends on the September equinox 2011 completing a full orbit around the Sun and an entire year for the people of Earth.

Because of our busy lives we tend to forget how dependent we are on the celestial mechanics of the solar system for life.  We owe our very existence to the fact that everything in the solar system, indeed the galaxy, moves in predictable orbits.  Thankfully for Earth our solar system is stable but that is not the case elsewhere in the galaxy.  In alien solar systems that we’ve only recently discovered there are planets that are drifting away from their stars and getting colder.  There are also planets that are being drawn inexorably towards their stars to eventually be consumed by them.  Other planets cross orbits too close to one another and are knocked off their orbits never to return to their home solar system.

We are lucky that our solar system has time to work out its kinks before life began on Earth.  If the solar system did not have orbital stability there’s a good chance life might not have arose here.  So be thankful we live on such a marvelous planet in a marvelous solar system!  On this spring equinox 2014 take a moment to think about the science that is behind the changing of the seasons and if the weather is clear tonight (fingers crossed!) go outside and take a look at the night sky and think that everything you see up there obeys the same laws that govern the seasons here on Earth.

Our Fragile Island Home – Earth Day 2013

I’ve always been a conservationist and an eco-minded person since my days in Boy Scouts.  We learned that nature is should be respected and cared for and as much as possible we should live in harmony with our surroundings.  However, when you’re able to see pictures of the Earth from space your whole perspective changes.  I’m sure most people are familiar with the famous “Earthrise” photograph taken by Apollo 8 astronaut William Anders in 1968.  “Earthrise” gave a whole new perspective of our home planet and gave realization to the fact that our planet is just a fragile little island floating in an unimaginably huge universe.  Imagine being in the position of Anders or any of the Apollo astronauts as they saw the Earth rise over the lunar surface and realized that everything they’ve ever experienced, everyone they’ve ever known, all their prior life was 250,000 miles away on that small blue rock.

Apollo 8 "Earthrise" photo taken December 24, 1968

Apollo 8 “Earthrise” photo taken December 24, 1968

Few people have had the privilege to see the Earth from space, whether from low orbit or during a lunar mission but we’ve been able to vicariously experience it through the photos and films they’ve brought back that  have left us stunned.  One such striking video was recently compiled by NASA’s MESSENGER probe as it left the Earth on its way to Mercury.  The probe had a camera pointed back towards the Earth as it left it behind and the stitched together frames produced in image of stunning beauty and inspiration.  As the Earth slowly fades away into the blackness of space we realize our true place in the universe.  We are but minnows swimming in a vast, vast ocean.  

Even with the potential of planetary travel and colonization in the distant future we must still place immeasurable value on our home planet.  The Earth has been so good to us for millions of years and will continue to do such if we take proper care of it.  As a whole, the human race is awakening from a slumber of environmental torment.  From the mid-to-late 1800’s and the dawn of industrialism we have polluted the planet to a sickening degree.  We’ve deforested much of the rain forests and polluted the water we drink and the air we breathe.  For over a century we were largely oblivious to the damage we were doing to our fragile environment.  But now we’re waking up to the consequences of our actions.  It is not too late to reverse the damage we’ve done to our planet because she is a resilient creature.  But that should not give us a license to continue to damage her and squander the beauty and riches of our island home.

Even if we travel to hundreds of planets in the future we may never find one quite like Earth (if we find any like it at all).  We were placed here on Earth by divine decree and it is that same decree that should guide our actions going forward to restore and protect our pale blue dot, our fragile island home because it’s all we have.

 

Earth Day 2012

Dear Bloggosphere and Interweb:

Earth Day 2012 is this Sunday April 22nd.  This is the 42nd year of Earth Day which makes this year’s Earth Day superior to all the rest, the answers to life, the universe, and everything hinge upon your participation in the celebration!  If you’ve never read The Hitchhiker’s Guide to the Galaxy don’t worry about it.  But seriously, Earth Day is a global effort to raise awareness for nature conservation, green technology, efficient energy use, and much more.

As a lover of the cosmos I marvel at how vast, impressive, and beautiful the universe is through my telescope.  The wonders of the universe are simply too many to be counted, it’s beauty and complexity too immense for the human mind to fully comprehend.  All of the focus on celestial bodies and phenomena serves one massive purpose:  to fully and better understand the uniqueness and immense beauty of our home planet; our tiny blue dot!  Indeed when you spend but 10 minutes thinking of how vast and immeasurable the universe is, you begin to appreciate our home all the more.  Much of the universe is hostile and inhabitable, but here we are orbiting a star at just the right distance, a star that is just the right size, just the right temperature, and our planet is just the right size to to hold onto an atmosphere.  The conditions for life on planet Earth are perfect in every sense of the word!  We also exist in exactly the right time period in the universe’s life.  The window of opportunity for life to arise in the universe is so small that if the entire life of the universe was one 24-hour period, the conditions for life to arise would occupy less than a minute of that time!

Our planet is incredibly special and unique, not only in our solar system, but in the entire universe.  We’ve yet to discover any other alien planets that definitely have the correct conditions for supporting life.  We’re constantly searching and there are a lot of candidates, but so far we haven’t struck gold.  Once you understand the rarity of our planet and its unique nature in the universe a very profound experience of connection with the planet occurs.  We are merely stewards of this planet.  Our goal should be to live responsibly on the planet, not to greedily consume its resources and squander its beauty.  One look at the cosmos and we’re reminded that once Earth is barren there is no where else to go.  We live on an island travelling though the cosmos.  We are in complete isolation, even if there are other living creatures elsewhere we couldn’t hope of reaching their planets or moons.  Plain and simple, Earth is all we have.

This Earth Day make a pledge to, by the best of your ability, live a more environmentally-friendly life in 2012.  Be more conscious of how your every day life affects the planet.  Rethink your commute to work.  Begin recycling.  Commit to planting trees.  Talk to your lawmakers about environmental issues.  Let your voice be heard on behalf of our fragile planet!  For more information on Earth Day 2012 visit the website www.earthday.org/2012.

Our fragile island home taken by Apollo astronaut Jim Lovell on Christmas Eve 1968

The Fake First Day of Spring

Today is March 1st…holy crap it’s March already?!?!  When did that happen?  I swear time moves faster every year that goes by.  Anyway, the fact that it is March 1st causes lots of people to hear something strange on TV or the radio.  Meteorologists like to trick people into believing that today is the first day of Spring.  Now we all know that the first day of Spring is March 20, 2012, also known as the Vernal (March) Equinox.

People get all excited when they hear that the equinox is coming up.  They start packing away all their heavy winter coats, hats, glove, snow shovels (unwise!), and thermal underwear.  The equinox is great because you get to see your neighbors again after their deep winter hibernation because their food supplies are running low.  People make last-minute trips to the grocery store to buy eggs.  Not for Easter mind you, but because they’ve eaten the last one and you must at least try to stand one on its end…only to give up after 20 minutes of frustration.  But why this false hope so early in the month?  The equinox isn’t for another 19 days!  The reason meteorologists state is that before we divided the seasons up into precise measurements based on the astronomical calendar we took the easy road and just said that each season was exactly three months long and started on the first of every third month, Spring on 3/1, Summer on 6/1, Autumn on 9/1, and Winter on 12/1.  These months were chosen based on variations in overall temperature.  It was long observed that the temperature began to change on or about the first of every third month.  As we can all tell, this way of reckoning the seasons isn’t terribly inaccurate, but we’ve since discovered a more accurate way of measuring the seasons based on the orbit of our planet around the sun.

Because of the eccentricity of the Earth (its elliptical orbit) and the axial tilt of 23.5 degrees we have varying climates which we call seasons.  When a certain hemisphere (north or south) is pointed towards the sun that hemisphere experiences summer while the other hemisphere experiences winter.  The transitional seasons of spring and autumn occur at the equinoxes when the Earth is midway through its “wobble” and the sunlight hits both hemispheres evenly.  Even once the astronomical reckoning had been established, meteorologists continued to use their own reckoning to determine seasons.

The "official" sign of spring Credit: Florence McGinn

Why do the meteorologists insist on using their way of defining the seasons?  I don’t know.  Perhaps that contributes to why they seem to always get the forecast wrong.  Although, I can’t exactly argue with their theory today.  In Baltimore it is currently 65° and sunny and last night we even had a pretty good thunderstorm which usually don’t happen until actual springtime.  It certainly feels a lot like spring here.  But this is Maryland, the land of inconsistency!  It is my belief that in Maryland we have the wackiest weather in the whole country.  It’s been a very mild winter for the entire east coast but it is definitely not unusual for MD to have a couple days every winter where the temperature reaches 70°.  Then the very next day it will be a chilly 33°. We see snow in April sandwiched by upper 60’s days, cold snaps in the summer, and sometimes snow before Halloween.  So as a way of reaching through all the clutter of when the seasons actually begin I’ve come up with a better way to do it all.  Sports.

I’ve always thought of the seasons this way.  I makes sense.  It’s also extremely simple.  Spring begins on the third Sunday of February when pitchers and catchers report for Spring Training.  Summer begins once the European soccer season ends in late May, after the Champions League Final.  Autumn begins with Week 1 of the NFL season, and winter begins once the NFL playoffs begin and basketball and hockey are in full-swing.  One could even simplify it further by lumping spring & summer together under baseball season and combining autumn and winter together under soccer season.  There is some overlap included since the European soccer season stretches from August to May, but the dividing point is always the beginning of Spring Training.  If only the whole world followed the MLB and NFL then this calendar would be easily recognized by all developed nations.  But alas it is not, so I am forced to officially recognized the two methods we have now while following the athletic method in my heart.  With that being said, go out and enjoy the fake first day of Spring!

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