Winter is officially over and the days are now getting longer, although it may not feel like it in many parts of Britain
With patches of snow still covering the ground in parts of Britain, it may not seem like the first day of spring. But as of 4.15am Tuesday morning, winter was officially over for another year.
The spring, or vernal, equinox marks the point in space and time when the sun moves across the celestial equator, an imaginary circle projected into the sky above the real equator.
In the northern hemisphere, the sun moves south to north in the spring equinox, and days grow longer and nights shorter. For those in the southern hemisphere, the same equinox marks the arrival of autumn and longer nights.
When is the first day of spring? Read more
Seasons on Earth are driven by the planet’s orbit and 23.5 degree tilt from the vertical axis. As the Earth circles the sun, it can show more of its northern or southern poles to the sun. But when the Earth passes through an equinox, both poles receive equal sunlight, because the planet is tilted neither towards or away from the sun.
While the equinox signals a time when day and night are equal, the moment when both share 12 hours apiece happens days earlier, because of atmospheric effects.
“The Earth’s atmosphere delays the sunset and makes the sunrise earlier,” said Robert Massey at the Royal Astronomical Society. “When the sun is on the horizon, light is bent round because we have a thick atmosphere, and that appears to raise the sun in the sky. So when the sun appears on the horizon, it would actually have set if we had no atmosphere.”
The date of the spring equinox varies from 19 to 21 March depending on location and corrections due to the mismatch between the Gregorian calendar, which logs 365 days a year, and the duration of Earth’s orbit around the sun, which takes 365.25 days to complete.
Happy Spring #Equinox and happy #firstdayofspring! Today the length of night and day are nearly equal. The days will now become longer at the higher latitudes because it takes the sun longer to rise and set. More satellite imagery: https://t.co/mbgRYot60A pic.twitter.com/kGlGhM5V58 — NOAA Satellites (@NOAASatellites) March 20, 2018
The National Oceanic and Atmospheric Administration (NOAA) celebrated a crisp start to spring today (March 20) in the Northern Hemisphere with a stunning view of Earth from sunset to sunrise.
NOAA officials tweeted the view of sunset on March 19 through sunrise March 20, taken with the agency's GOES-East weather satellite.
"Happy Spring #Equinox and happy #firstdayofspring!" NOAA officials wrote. "Today the length of night and day are nearly equal. The days will now become longer at the higher latitudes because it takes the sun longer to rise and set."
The Suomi NPP satellite took this image of the snow-covered northeastern United States and Canada on March 18, 2018. The image was created by combining the three color channels of the satellite's Visible Infrared Imaging Radiometer Suite (VIIRS) instrument. Credit: NOAA/NESDIS
The vernal equinox occurs as the sun passes over the equator from Earth's perspective and the Northern Hemisphere begins to tilt toward the sun, leading to longer days in the north and shorter days in the south. It marks the north's first day of spring — snowy weather in some areas notwithstanding — and the beginning of fall for those in the Southern Hemisphere. While the day-to-day variations in weather are much more complex, the vernal equinox is a sign that warmer days are on the way.
The next big sun event for the Northern Hemisphere is the summer solstice on June 21, the longest day of the year, when Earth's northern half is most directly tilted toward the sun. (It's also the south's winter solstice.)
A true-color view of Earth taken with the Suomi NPP satellite's VIIRS instrument on March 19, 2018. Credit: NOAA/NESDIS
Even better views are coming. NOAA launched what will be the new GOES-West spacecraft this month in partnership with NASA; the eagle-eyed satellite will help track extreme weather across the western United States and eastern Pacific Ocean as a counterpart to GOES-East. The satellite will move to its final GOES-West vantage point after about six months of preparing its instruments and running checks.
To see more NOAA imagery taken today, readers can visit https://www.nesdis.noaa.gov/content/imagery-and-data.
Email Sarah Lewin at slewin@space.com or follow her @SarahExplains. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.
AS THE days begin to get slightly longer, many of us have been wondering when we can finally herald the arrival of spring.
March 20 marks the Spring Equinox - but does this mean winter has officially finished and is it the same thing as the Vernal Equinox? Here's what you need to know...
Getty Images Are you craving warmer temperatures? Weather will take a turn for the better from today
When is the Spring Equinox?
Good news for those counting down the days until warmer weather - the 2018 spring equinox is here!
This is the time when the sun passes the celestial equator and days become longer - no more going to work in pitch darkness.
For some March 20 marks the first official day of spring - but meteorologists argue that it's actually March 1.
The Met Office tend to use the meteorological seasons, these are based on the annual temperature cycle and the state of the atmosphere.
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What is the Vernal Equinox?
The Vernal Equinox is another name given to the Spring Equinox and labels the March Equinox in the Northern Hemisphere.
In the Southern Hemisphere, the March Equinox is called the Autumnal Equinox.
In September the equinoxes are labelled vice versa – the Northern Hemisphere experiencing an Autumnal Equinox and the Southern Hemisphere having their Vernal Equinox.
The equinox marks the moment the Sun crosses the celestial equator – the imaginary line in the sky above the Earth’s equator.
It is at this time that the Northern Hemisphere marks the first day of astronomical spring.
Getty Images The Spring Equinox is finally here after months of winter
When date does the Vernal Equinox fall on in March?
The 2018 Vernal Equinox, is the same thing as the Spring Equinox and falls on March 20.
The different seasons are caused by the Earth rotating around the Sun.
The way the Earth rotates means that certain areas of the globe are tilted towards the Sun while other parts are tilted away from it.
This means there are different levels of sunlight reaching each part of the globe, causing the seasons.
For the Northern Hemisphere, Tuesday, March 20, marks the vernal, or spring, equinox — the first day of spring.
The National Weather Service shared this image from space of the Earth just before “the sun crossed the equator,” or just before the start of spring. For those living north of the equator — the imaginary latitude line that marks the middle of the Earth — the days will begin to get longer.
What does that mean?
Equinoxes happen twice per year (the vernal and autumnal equinox) when the sun crosses over the equator. During an equinox the length of day and night of the Northern and Southern Hemispheres are nearly the same. (The word equinox means “equal night”.)
Why does this happen?
“Earth’s axis is an imaginary pole going right through the center of Earth from ‘top’ to ‘bottom,'” NASA explains. “Earth spins around this pole, making one complete turn each day. That is why we have day and night, and why every part of Earth’s surface gets some of each.”
We have seasons because Earth’s axis is on a tilt, and that tilt “always points in the same direction,” according to NASA. So as Earth rotates around the sun, during part of the year, the North Pole tilts towards the sun, and for half of the year the South Pole tilts towards the sun. Thus, causing our seasons (summer in the Northern Hemisphere when the North Pole is tilting towards the sun, and summer for the Southern Hemisphere when the South Pole is tilting towards the sun).
On an equinox, “the tilt of the Earth’s axis is perpendicular to the Sun’s rays,” according to Time and Date. After this vernal equinox, the Northern Hemisphere will begin to experience the sun’s rays more directly, hence spring and summer!
Though, for some in the Northern Hemisphere who are preparing for Winter Storm Toby, it may not feel like spring just yet.
