Stoked on Science: The first day of spring

Jade Harvey

Special to the Review

So, it seems March has suddenly appeared, miraculously warm and sunny. Unbelievably my driveway is already free of snow. It appears I now judge all weather and the happiness of my life on the ease of which I can move my vehicle from drive to street. I must indeed be getting old. Today, Wednesday the 20th of March signifies that the first official day of spring is here. Scientifically referred to as the Vernal Equinox (in the Northern Hemisphere), this phenomenon falls this year, rather excitedly for me, exactly on my 30th birthday.

This aligning of the sun with our equator, due to the Earth’s tilt being neither tilted toward or away from the Sun, happens twice per year – the Vernal (spring) equinox, falling on either March 20th/21st or The Autumnal (Fall) equinox on Sept 22nd/23rd. The term ‘Equinox’ means ‘the equality between the day and night’ and comes from the Latin terms ‘aequus’ meaning equal and ‘nox’ night. This refers to the fact that the Southern and Northern Hemisphere receive the same amount of solar insolation or sunlight on this date and that the day and nights for both hemispheres is the same, roughly 12 hours each. As the Sun is at 90 degrees to the Earth on this day, If you happen to be standing on the equator on the Equinox you will see the sun directly overhead for the whole daytime.

Our seasons are controlled by out orientation and angle around the Sun. Today, the Earth’s axis is tilted 23.5 degrees from the plane of its orbit around the sun. As we move around the Sun and spin on our axis this tilt remains the same. Sort of. It does in fact change. During a cycle that averages about 40,000 years, the tilt of the axis varies between 22.1 and 24.5 degrees. This is known as the Obliquity of the orbit and as Milutin Milankovitch, the scientist to discover this, stated over 200 years ago, “As the axial tilt increases, the seasonal contrast increases so that winters are colder and summers are warmer.”

This variable can change how extreme our seasons feel as they either mean more time either faced towards the sun or for the other hemisphere, without its delicious life giving glow. Right now we are heading towards the extreme end of this one variable (of many) which may further exacerbate the effects of anthropogenic climate change occurring on the Earth.

From March 20 the days will get longer until the peak at the June Solstice, the first day of Summer (June 21). This occurs when our hemisphere points the most towards the Sun, spreading more light and warmth for us. From June 21 until the Autumnal Equinox (Sept. 21) days will shorten back to equal. From the Autumnal Equinox forward to the first day of Winter on Dec. 21 the days will get shorter and shorter, with less and less of us facing our life giving star until the cycle begins again and a seasonal year is complete.

The Vernal Equinox has been a part of our cultural and societal connection with the heavens since the inception of thought. More recently it signifies the start of the new astrological year but it was cherished and worshipped thousands of years ago by the Babylonians. Huge monuments were built inline with the rising sun on this date by the Egyptians and the day of Easter is celebrated on the first Sunday, after the full moon that follows the Equinox. It has figured into rituals, celebrations and mysticisms of faiths and cultures across all time and the span of our world. But most importantly of course, it falls on my birthday, making it a pretty special day.

Fun thought to ponder though…If June 21 is the day when we receive the most sunshine, why is it regarded as the beginning of Summer and not its peak? And similarly, why is Dec. 21, the day of least sunshine, the beginning of Winter and not mid-winter day? You can blame the oceans. They store and release heat through the year, but their heating and cooling happens only slowly. By June 21 they are still cool from the winter time, and that delays the peak heat. Similarly, in December the water still holds warmth from the summer, and the coldest days are still ahead.

And so on my birthday, sorry, Vernal Equinox, I will be thankful for a week of high pressure bringing a sunny day for me to celebrate on. I will cherish the movement of our planet into its next phase of orbit and for another year of my life to start in the place I love the most, Revelstoke. I enjoy these days of significance not for the mystical nature, nor for the fact that anything magical happens but for the reminder of the magnificence of being alive on a big chunk of rock spinning continuously, on our latitude, at about 1125km per hour as it whizzes through space. It’s really quite amazing. What a joy to be alive and 30!

Jade graduated with a 1st Class Honours BSc in Physical Geography from QMUL, a top 5 university in Europe. Having spent the last 8 years travelling the mountainous regions of the world, mountain guiding and lecturing on science in schools she now likes to share her passion for science through writing and telling stories at the Regent Hotel and CMH Revelstoke.



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