{"id":56478,"date":"2024-03-20T09:22:22","date_gmt":"2024-03-20T09:22:22","guid":{"rendered":"http:\/\/92f4da77-e903-443c-ac26-54001604a656"},"modified":"2024-03-20T10:32:34","modified_gmt":"2024-03-20T10:32:34","slug":"today-marks-the-first-day-of-spring-but-why-is-this-the-spring-equinox-solstices-and-equinoxes-explained","status":"publish","type":"rss_feed","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/rss_feed\/today-marks-the-first-day-of-spring-but-why-is-this-the-spring-equinox-solstices-and-equinoxes-explained\/","title":{"rendered":"Today marks the first day of spring! But why is this the spring equinox? Solstices and equinoxes explained"},"content":{"rendered":"

How Earth’s tilt and orbit gives us seasons, solstices and equinoxes, and when they are occurring in 2024. <\/p>

By Katrin Raynor\n <\/p>

Published: Wednesday, 20 March 2024 at 09:22 AM<\/p>

\n\n

The Northern\u2019s Hemisphere\u2019s vernal or spring equinox occurs on 20 March 2024, the centre of the Sun\u2019s disc moving south to north across the celestial equator at 03:06 UTC.<\/p>

And in 2024 the summer solstice occurs on 20 June at 21.51 BST (20.51 UTC).<\/p>

But what do solstices and and equinoxes actually mean, and why do we mark them on our calendars?<\/p>

Read on to find out.<\/p>

Solstices and equinoxes in 2024<\/strong><\/h2>
Spring equinox 2024<\/strong> occurs on 20 March at 03:07 UTC<\/li>
Summer solstice 2024<\/strong> occurs on 20 June at 20:51 BST<\/li>
Autumn equinox 2024<\/strong> occurs on 22 September at 12.44 UTC<\/li>
Winter solstice 2024<\/strong> occurs on 21 December at 09:21 UTC<\/li><\/ul>
Illustration of people gathering at Stonehenge to witness the summer solstice. Credit: Mark Garlic \/ Science Photo Library<\/figcaption><\/figure>
For thousands of years, our ancient ancestors tracked the path of the Sun across the sky.<\/p>
Watching it rise and set at different positions throughout the year and constructing monuments such as the prehistoric stone circle Stonehenge<\/a> in Wiltshire to keep track of its movement.<\/p>
June is a key month in the Sun\u2019s path and also at Stonehenge, where thousands visit to mark the summer solstice \u2013 the longest day and shortest night of the year in the Northern Hemisphere.<\/p>
The word \u2018solstice\u2019 comes to us from Latin, \u2018sol\u2019 meaning Sun and \u2018sistere\u2019 to stand still.<\/p>
But why does the Sun appear to stand still? And what does it signify in the astronomical calendar?<\/p>
Join me on a short journey as we follow Earth\u2019s orbit of the Sun<\/a> and learn why we experience seasons and variations in sunlight throughout the year.<\/p>
$\"The$
The differences between our seasons is caused by just a few degrees of slant. Credit: Michael Moltenbrey<\/figcaption><\/figure>
Solstices, equinoxes and Earth’s orbit<\/strong><\/h2>
We know that the changing position of the Sun in the sky is down to various factors involving the movement and position of our own planet over the year.<\/p>
Earth is 150 million kilometres from the Sun and orbits it along a slightly elliptical path at a speed of 107,208 kilometres per hour.<\/p>
One orbit takes approximately 365 days.<\/p>
Our planet isn\u2019t upright in its orbit; it\u2019s tilted at an angle of 23.4\u00b0 and spins on an axis (an imaginary line that passes through the North Pole to the South Pole) at a speed of 1,670 kilometres per hour.<\/p>
One spin takes 24 hours.<\/p>
$\"The$
The changing of the seasons, solstices and equinoxes are a visible sign of Earth’s tilt and orbit around the Sun. Credit: Peter Adams \/ Getty Images<\/figcaption><\/figure>
The tilt, rotation and elliptical orbit of Earth all give rise to changes in the amount of sunlight that we receive in each hemisphere throughout the year, and this is why we have seasons<\/a>.<\/p>
When the top of Earth is tilted towards the Sun, the Northern Hemisphere experiences summer, while the Southern Hemisphere faces away and people there have their winter.<\/p>
Six months later and the seasons flip in each hemisphere.<\/p>
Our seasons in the astronomical calendar are determined by two solstices and two equinoxes a year.<\/p>
A solstice occurs at the two points in Earth\u2019s orbit when our globe is at its maximum tilt either towards or away from the Sun.<\/p>
Equinoxes happen at the two points of the orbit when the Sun appears directly over the equator.<\/p>
The solstices and equinoxes divide the year into four parts: spring, summer, autumn and winter.<\/p>
$\"Earth\u2019s$
Earth\u2019s tilt affects how much direct light we receive from the Sun, which causes the yearly cycle of the seasons, solstices and equinoxes<\/figcaption><\/figure>
Summer solstice and Earth’s tilt<\/b><\/h2>
The summer solstice occurs when that hemisphere\u2019s pole is tilted at its maximum angle towards the Sun.<\/p>
During this time, we experience a day with the longest period of daylight, 16 or so hours in the UK.<\/p>
In 2023 the summer solstice in the Northern Hemisphere fell on 21 June.<\/p>
On this day at 3:57pm BST the Sun reached the most northerly point along its path through the sky (the ecliptic<\/a>) before moving south again.<\/p>
This is what is meant by the Sun \u2018standing still\u2019.<\/p>
The winter solstice is the opposite and occurs in December, when the North Pole is tilted at its maximum angle away from the Sun and the Sun reaches its most southerly point in the sky.<\/p>
In 2023 the winter solstice in the northern hemisphere occurred at at 03:28 UT on 22 December.<\/p>
You might think that because Earth is tilted towards the Sun during the summer solstice, that that\u2019s when we are closest to our star.<\/p>
But this is not the case. In fact, the point at which our planet is closest to the Sun (perihelion) is in early January.<\/p>
On 21 June, Earth was actually nearing the point at which it is furthest away from the Sun (aphelion), in early July.<\/p>
$\"Equinoxes$
Equinoxes occur when the Sun crosses the celestial equator. For Earth, this is the point that the planet\u2019s axis points neither towards nor away from the Sun. Credit: BBC Sky at Night Magazine<\/figcaption><\/figure>
Equinoxes explained<\/strong><\/h2>
Falling between the summer and winter solstices are the spring and autumn equinoxes.<\/p>
\u2018Equinox\u2019 again comes from Latin and translates as \u2018equal night\u2019.<\/p>
The equinoxes happen when Earth\u2019s axis points neither towards nor away from the Sun, a point when the Sun crosses the celestial equator going northwards or southwards depending on the time of year.<\/p>
The Sun is above the horizon for the same amount of time as it is below it.<\/p>
In 2023, spring equinox was on 20 March; the autumn equinox was on 23 September.<\/p>
This article originally appeared in the June 2023 issue of BBC Sky at Night Magazine.<\/strong><\/em><\/p> <\/body><\/html>\n
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