Welcome to the I Can't Sleep Podcast,
Where I help you drift off one fact at a time.
I'm your host,
Benjamin Boster,
And today's episode is about the season's spring.
Spring,
Also known as springtime,
Is one of the four temperate seasons,
Succeeding winter and preceding summer.
There are various technical definitions of spring,
But local usage of the term varies according to local climate,
Cultures,
And customs.
When it is spring in the northern hemisphere,
It is autumn in the southern hemisphere,
And vice versa.
At the spring equinox,
Also called the vernal equinox,
Days and nights are approximately 12 hours long,
With daytime length increasing and nighttime length decreasing as the season progresses until the summer solstice.
The spring equinox is in March in the northern hemisphere and in September in the southern hemisphere,
While the summer solstice is in June in the northern hemisphere and in December in the southern hemisphere.
Spring and springtime refer to the season and also to ideas of rebirth,
Rejuvenation,
Renewal,
Resurrection,
And regrowth.
Subtropical and tropical areas have climates better described in terms of other seasons,
E.
G.
Dry or wet,
Monsoonal or cyclonic.
Cultures may have local names for seasons,
Which have little equivalence to the terms originating in Europe.
According to the online etymological dictionary,
Spring in the sense of the season comes from phrases such as springtime,
14th century,
And the spring of the year.
This use is from an archaic noun meaning act or time of springing or appearing.
The first appearance,
The beginning,
Birth,
Rise,
Or origin.
Spring as a word in general appeared via the Middle English springen,
Spelled s-p-r-i-n-g-e-n,
Via the Old English springen,
S-p-r-i-n-g-a-n.
These were verbs meaning to rise up or to burst forth,
And are not believed to have originally related to the season.
These all originate from Proto-Germanic springen.
Meteorologists generally define four seasons in many climatic areas.
Spring,
Summer,
Autumn,
And winter.
These are determined by the values of their average temperatures on a monthly basis,
With each season lasting three calendar months.
The three warmest months are by definition summer.
The three coldest months are winter,
And the intervening gaps are spring and autumn.
Meteorological spring can therefore start on different dates in different regions.
In the United States and United Kingdom,
Spring months are March,
April,
And May.
In Ireland,
Following the Irish calendar,
Spring is often defined as February,
March,
And April.
In Sweden,
Meteorologists define the beginning of spring as the first occasion on which the average 24 hours temperature exceeds zero degrees Celsius for seven consecutive days.
Thus,
The date varies with latitude and elevation,
But no earlier than February 15th,
And no later than July 31st.
In Australia,
New Zealand,
South Africa,
And Brazil,
The spring months are September,
October,
And November.
In the Northern Hemisphere,
With countries such as Germany,
The United States,
Canada,
And the UK,
Solar reckoning was traditionally used with the solstices and equinoxes representing the midpoints of each season.
However,
The astronomical vernal equinox,
Varying between the 19th and 21st of March,
Can be taken to mark the first day of spring with the summer solstice around June 21st,
Marked as first day of summer.
By solar reckoning,
Spring is held to begin February 1st until the first day of summer on May Day,
With the summer and winter solstices being marked as midsummer and midwinter respectively,
Instead of as the beginning of the season,
As is the case with astronomical reckoning.
In Persian culture,
The first day of spring is the first day of the first month,
Which begins on March 20th through 21st.
In the traditional Chinese calendar,
The spring season consists of the days between Lichuan,
The 3rd through the 5th of February,
Taking Chuanfen,
The 21st through the 22nd of March as its midpoint,
Then ending at Lixian,
The 5th through the 7th of May.
Similarly,
According to the Celtic tradition,
Which is based solely on daylight and the strength of the noon sun,
Spring begins in early February,
Near Imbolc or Candlemas,
And continues until early May,
Beltane,
With St.
Patrick's Day,
The 17th of March,
Being regarded as the middle day of spring.
Late Roman Republic scholar Marcus Terentius Varro defined spring as lasting from the 7th day before the Ides of Februarius,
The 7th of February,
To the 8th day before the Ides of Maius,
8th of May.
The spring season in India is culturally in the months of March and April,
With an average temperature of approximately 32 degrees Celsius.
Some people in India,
Especially from Karnataka state,
Celebrate their new year in spring,
Bhugadi.
The beginning of spring is not always determined by fixed calendar dates.
The phenological or ecological definition of spring relates to biological indicators,
Such as the blossoming of a range of plant species,
The activities of animals,
And the special smell of soil that has reached the temperature for microflora to flourish.
These indicators,
Along with the beginning of spring,
Vary according to the local climate and according to the specific weather of a particular year.
In England,
Wales,
And Northern Ireland,
The National Trust runs the hashtag Blossom Watch campaign,
Which encourages people to share images of blossoms with one another as an early indicator of the arrival of the season.
Some ecologists divide the year into six seasons.
In addition to spring,
Ecological reckoning identifies an earlier separate pre-vernal,
Early or pre-spring season,
Between the hibernal,
Winter,
And vernal spring seasons.
This is a time when only the hardiest flowers,
Like the crocus,
Are in bloom,
Sometimes while there is still some snow cover on the ground.
During early spring,
The axis of the Earth is increasing its tilt relative to the Sun,
And the length of daylight rapidly increases for the relevant hemisphere.
The hemisphere begins to warm significantly.
Causing new plant growth to spring forth,
Giving the season its name.
Any snow begins to melt,
Swelling streams with runoff,
And any frosts become less severe.
In climates that have no snow and rare frosts,
Air and ground temperatures increase more rapidly.
Many flowering plants bloom at this time of year in a long succession,
Sometimes beginning when snow is still on the ground and continuing into early summer.
In normally snowless areas,
Spring may begin as early as February in the northern hemisphere,
Or August in the southern hemisphere.
Heralded by the blooming of deciduous magnolias,
Cherries,
And quince.
Many temperate areas have a dry spring and wet autumn,
Which brings about flowering in this season,
More consistent with a need for water,
As well as warmth.
Subarctic areas may not experience spring at all until May.
While spring is a result of the warmth caused by the changing orientation of the Earth's axis relative to the Sun,
The weather in many parts of the world is affected by other less predictable events.
The rainfall in spring,
Or any season,
Follows trends more related to longer cycles,
Such as the solar cycle,
Or events created by ocean currents and ocean temperatures,
For example the El Niño effect and the Southern Oscillation Index.
Unstable spring weather may occur more often when warm air begins to invade from lower latitudes,
While cold air is still pushing from the polar regions.
Flooding is also most common in and near mountainous areas during this time of year,
Because of a snow melt which is accelerated by warm rains.
In North America,
Tornado Alley is most active at this time of year,
Especially since the rocky mountains prevent the surging hot and cold air masses from spreading eastward,
And instead force them into direct conflict.
Besides tornadoes,
Supercell thunderstorms can also produce dangerously large hail and very high winds,
For which a severe thunderstorm warning or tornado warning is usually issued.
Even more so than in winter,
The jet streams play an important role in unstable and severe northern hemisphere weather in springtime.
In recent decades,
Season creep has been observed,
Which means that many phenological signs of spring are occurring earlier in many regions,
By around two days per decade.
Spring in the southern hemisphere is different in several significant ways to that of the northern hemisphere for several reasons,
Including 1.
There is no land bridge between southern hemisphere countries in the Antarctic zone,
Capable of bringing in cold air without the temperature mitigating effects of extensive tracts of water.
2.
The vastly greater amount of ocean in the southern hemisphere at most latitudes.
3.
There is a circumpolar flow of air,
The roaring 40s and 50s,
Uninterrupted by large landmasses.
4.
No equivalent jet streams.
5.
The peculiarities of the reversing ocean currents in the Pacific.
Carnival is practiced by many Christians around the world in the days before Lent,
40 days,
Without Sundays,
Before Easter.
It is the first spring festival of the new year for many.
Easter is the most important religious feast in the Christian liturgical year.
Christians believe that Jesus was resurrected from the dead on the third day,
Two days after his crucifixion,
And celebrate this resurrection on Easter Day,
Two days after Good Friday.
Since the Last Supper was a Passover Seder,
The date of Easter can be calculated as the first Sunday after the start of Passover.
This is usually the first Sunday after the first full moon,
Following the spring equinox.
The date of Easter varies between March 22nd and April 25th,
Which corresponds to between April 4th and May 8th in their Gregorian calendar for the Eastern and Oriental Orthodox churches using the Julian calendar.
In this celebration,
The children do an Easter egg hunt.
The first of May is the date of many public holidays.
In many countries,
May Day is synonymous with International Workers' Day or Labor Day,
Which celebrates the social and economic achievements of the labor movement.
As a day of celebration,
The holiday has ancient origins,
And it can relate to many customs that have survived into modern times.
Many of these customs are due to May Day being a cross-quarter day,
Meaning that in the Northern Hemisphere,
Where it is almost exclusively celebrated,
It falls approximately halfway between the spring equinox and summer solstice.
In the Celtic tradition,
This date marked the end of spring and the beginning of summer.
The Passover begins on the 15th day of the month of Nisan,
Which typically falls on March or April of the Gregorian calendar on the night of a full moon after the northern spring equinox.
However,
Due to leap months falling after the vernal equinox,
Passover sometimes starts on the second full moon after vernal equinox,
As in 2016.
Jewish people celebrate this holiday to commemorate their escape from slavery in Egypt,
As described in the Book of Exodus in the Torah.
Foods consumed during Passover seders,
Such as lamb and barley,
Are tied to springtime seasonal availability.
In this celebration,
Children recite the four questions during the seder and hunt for the yafikoman afterwards.
The Western Christian season,
Encompassing the Tridium of All Saints' Eve,
Halloween,
All Saints' Day,
All Hallows,
And All Souls' Day,
Are observed in the spring in the Southern Hemisphere.
A solar equinox is a moment in time when the sun appears directly above the equator,
Rather than to its north or south.
On the day of the equinox,
The sun appears to rise directly east and set directly west.
This occurs twice each year,
Around March 20th and September 23rd.
An equinox is equivalently defined as the time when the plane of Earth's equator passes through the geometric center of the sun's disk.
This is also the moment when Earth's rotation axis is directly perpendicular to the sun-Earth line,
Tilting neither toward nor away from the sun.
In modern times,
Since the moon,
And to a lesser extent the planets,
Causes Earth's orbit to vary slightly from a perfect ellipse,
The equinox is officially defined by the sun's more regular elliptical longitude rather than by its declination.
The instants of the equinoxes are currently defined to be when the apparent geocentric longitude of the sun is 0° and 180°.
The word is derived from the Latin equinoctium,
From equa,
Equal,
And nox,
Night.
On the day of an equinox,
Daytime and nighttime are of approximately equal duration all over the planet.
Contrary to popular belief,
They are not exactly equal because of the angular size of the sun,
Atmospheric refraction,
And the rapidly changing duration of the length of day that occurs at most latitudes around the equinoxes.
Long before conceiving this equality,
Equatorial cultures noted the day when the sun rises due east and sets due west,
And indeed this happens on the day closest to the astronomically defined event.
As a consequence,
According to a properly constructed and aligned sundial,
The daytime duration is 12 hours.
In the northern hemisphere,
The March equinox is called the vernal or spring equinox,
While the September equinox is called the autumnal or fall equinox.
In the southern hemisphere,
The reverse is true.
During the year,
Equinoxes alternate with solstices.
Leap years and other factors cause the dates of both events to vary slightly.
Hemisphere neutral names are northward equinox for the March equinox,
Indicating that at the moment the solar declination is crossing the celestial equator in a northward direction,
And southward equinox for the September equinox,
Indicating that at that moment the solar declination is crossing the celestial equator in a northward direction.
Daytime is increasing most quickly at the vernal equinox,
And decreasing most quickly at the autumnal equinox.
Systematically observing the sunrise,
People discovered that it occurs between two extreme locations at the horizon,
And eventually noted the midpoint between the two.
Later it was realized that this happens on a day when the duration of the day and the night are practically equal,
And the word equinox comes from the Latin equus,
Meaning equal,
And nox,
Meaning night.
In the northern hemisphere,
The vernal equinox,
March,
Conventionally marks the beginning of spring in most cultures,
And is considered the start of the new year in the Assyrian calendar,
Hindu,
And the Persian or Iranian calendars,
While the autumnal equinox,
September,
Marks the beginning of autumn.
Ancient Greek calendars too had the beginning of the year either at the autumnal or vernal equinox,
And some at solstices.
The Antikythera mechanism predicts the equinoxes and solstices.
The equinoxes are the only times when the solar terminator,
The edge between night and day,
Is perpendicular to the equator.
As a result,
The northern and southern hemispheres are equally illuminated.
For the same reason,
This is also the time when the sun rises for an observer at one of Earth's rotational poles,
And sets at the other.
For a brief period lasting approximately four days,
Both north and south poles are in daylight.
For example,
In 2021,
Sunrise on the north pole is March 18th,
709 UTC,
And sunset on the south pole is March 22nd,
1308 UTC.
Also in 2021,
Sunrise on the south pole is September 20th,
1608 UTC,
And sunset on the north pole is September 24th,
2230 UTC.
In other words,
The equinoxes are the only times when the subpolar point is on the equator.
Meaning that the sun is exactly overhead at a point on the equatorial line.
The subsolar point crosses the equator moving northward at the March equinox,
And southward at the September equinox.
When Julius Caesar established the Julian calendar in 45 BC,
He sets March 25th as the date of the spring equinox.
This was already the starting day of the year in the Persian and Indian calendars.
Because the Julian year is longer than the tropical year by about 11.
3 minutes on average,
Or one day in 128 years,
The calendar drifted with respect to the two equinoxes.
So that in 300 AD,
The spring equinox occurred on about March 21st,
And by the 1580s AD,
It had drifted backwards to March 11th.
This drift induced Pope Gregory VIII to establish the modern Gregorian calendar.
The Pope wanted to continue to conform with the edicts of the Council of Nicaea in 325 AD concerning the date of Easter.
Which means he wanted to move the vernal equinox to the date on which it fell at the time.
March 21st is the day allocated to it in the Easter table of the Julian calendar.
And to maintain it at around that date in the future,
Which he achieved by reducing the number of leap years from 100 to 97 every 400 years.
However,
There remained a small residual variation in the date and time of the vernal equinox of about plus or minus 27 hours from its mean position.
Virtually all because the distribution of 24-hour centurial leap days causes large jumps.
The dates of the equinoxes change progressively during the leap year cycle because the Gregorian calendar year is not commensurate with the period of the Earth's revolution about the Sun.
It is only after a complete Gregorian leap year cycle of 400 years that the seasons commence at approximately the same time.
In the 21st century,
The earliest March equinox will be March 19th,
2096.
While the latest was March 21st,
2003.
The earliest September equinox will be September 21st,
2096.
While the latest was September 23rd,
2003,
Universal Time.
On the date of the equinox,
The center of the Sun spends a roughly equal amount of time above and below the horizon at every location on the Earth.
So,
Night and day are about the same length.
Sunrise and sunset can be defined in several ways,
But a widespread definition is the time that the top limb of the Sun is level with the horizon.
With this definition,
The day is longer than the night at the equinoxes.
1.
From the Earth,
The Sun appears as a disk rather than a point of light.
So,
When the center of the Sun is below the horizon,
Its upper edge may be visible.
Sunrise,
Which begins daytime,
Occurs when the top of the Sun's disk appears above the eastern horizon.
At that instant,
The disk's center is still below the horizon.
2.
The Earth's atmosphere refracts sunlight.
As a result,
An observer sees daylight before the top of the Sun's disk appears above the horizon.
3.
In sunrise-sunset tables,
The atmospheric refraction is assumed to be 34 arcminutes,
And the assumed semidiameter,
Apparent radius of the Sun,
Is 16 arcminutes.
The apparent radius varies slightly depending on time of year,
Slightly larger at perihelion in January than at apohelion in July,
But the difference is comparatively small.
Their combination means that when the upper limb of the Sun is on the visible horizon,
Its center is 50 arcminutes below the geometric horizon,
Which is the intersection with the celestial sphere of a horizontal plane through the eye of the observer.
These effects make the day about 14 minutes longer than the night at the equator and longer still towards the poles.
The real equality of day and night only happens in places far enough from the equator to have a seasonal difference in day length of at least 7 minutes,
Actually occurring a few days towards the winter side of each equinox.
One result of this is that at latitudes below plus or minus 2 degrees,
All the days of the year are longer than the nights.
The times of sunset and sunrise vary with the observer's location,
Longitude and latitude,
So the dates when day and night are equal also depend upon the observer's location.
A third correction for the visual observation of a sunrise or sunset is the angle between the apparent horizon as seen by an observer and the geometric or sensible horizon.
This is known as the dip of the horizon and varies from 3 arcminutes for a viewer standing on the seashore to 160 arcminutes for a mountaineer on Everest.
The effect of a larger dip on taller objects,
Reaching over 2.
5 degrees of arc on Everest,
Accounts for the phenomenon of snow on a mountain peak turning gold in the sunlight long before the lower slopes are illuminated.
The date on which the length of day and night are the same length is known as an equilux.
The neologism believed to have been coined in the 1980s achieved more widespread recognition in the 21st century.
At the most precise measurements,
A true equilux is rare because the lengths of day and night change more rapidly than any other time of the year around the equinoxes.
In the mid-latitudes,
Daylight increases or decreases by about 3 minutes per day at the equinoxes and thus adjacent days and nights only reach within one minute of each other.
The date of the closest approximation of the equilux varies slightly by latitude.
In the mid-latitudes,
It occurs a few days before the spring equinox and after the fall equinox in each respective hemisphere.
