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.
Twice each year, as the sun marches across the sky, its center crosses Earth’s Equator.
This celestial alignment results in the equinox—a day with light and dark of (nearly) equal length, with the sun rising precisely in the east and setting precisely in the west. This year, the vernal, or spring, equinox will occur on Tuesday, March 20.
For most people, the equinox simply heralds a changing of the seasons. In March, the vernal equinox signals the beginning of spring in the Northern Hemisphere and autumn in the south, and the reverse happens during the September equinox.
What is an Equinox? What are equinoxes? What causes these astronomical events? Find out how they influence the seasons and hours of daylight on each planet.
But for many ancient cultures across the Americas, equinoxes were something more: a time for celebration, sacrifice, and migration.
For millennia, observing the sun’s shifting path was both essential for survival and hard to ignore. Our star’s celestial wanderings foretold the onset of the growth and harvest seasons and warned of impending winter, so it’s not unusual to find a variety of solar calendars among the artifacts of vanished civilizations. Other cultures are keeping their traditions alive, and still performing ceremonies timed to the equinox.
Ancient Calendars
Many people have heard of the Maya calendar, but others are lesser known. In the Peruvian desert north of Lima, at a site called Chankillo, an enormous astronomical observatory sits atop a ridge. Dating back to at least 500 B.C., the installation is a complex array of 13 towers, fashioned in a north-south line resembling a spine.
As the sun moves through its yearly paces, it rises and sets between the towers at predictable times, appearing to the left of the first tower at the summer solstice, in the center at equinox, and to the right of the last tower at winter solstice.
“The extreme end towers are very clearly marking the solstices, though the argument for the equinox is more indirect,” notes archaeologist Iván Ghezzi of the Catholic University of Peru, who described the site’s solar connection in 2007.
The identity of the observatory’s builders is still unknown, but like many ancient cultures in the Americas, they appeared to worship the sun. “Chankillo is much more than merely an astronomical observatory,” Ghezzi says. “It’s a site that was a large ceremonial center.”
Chankillo, though still fundamentally enigmatic, is one of many examples of structures built to align with the equinox, such as a Stonehenge-like circle of wooden poles, or Woodhenge, at a prehistoric site called Cahokia in Southern Illinois, and the earthen lodges oriented toward astronomical features built by the Skidi Pawnee.
Light, Shadow, and Sacrifice
But sometimes, simply marking astronomical alignments isn’t enough; another ancient method of tracing the sun’s meanderings through the sky involves using light and shadow to paint particular images. Here, the sunlight itself does the work, inscribing illuminated shapes or casting shadows. One example of this is at Chichén Itzá, where the Maya crafted a sculpture that transforms itself into a blazing serpent at equinox, representing their deity Kukulcan.
Another image in light was discovered in 1977, when rock artist Anna Sofaer was exploring the petroglyphs of the American southwest. There, at the top of New Mexico’s Fajada Butte, Sofaer found what’s known as the Sun Dagger, a calendrical marking created from two spirals etched into the rock. During summer solstice and equinox, the spirals are sliced by a dagger of light as the sun shines through slabs of rock; at winter solstice, two daggers appear on either side of the spiral—or did. The rock slabs have shifted and the images no longer appear.
The site is in Chaco Canyon, where an ancient civilization thrived for millennia before mysteriously abandoning their city.
Further evidence, in the form of interred bird bones, suggests that the Chaco Canyon inhabitants marked the equinox by sacrificing scarlet macaws. They’re not alone: The practice was apparently quite common among the Puebloans of the Southwest and Northern Mexico.
“In many of areas of the ancient New World, scarlet macaws were symbolically associated with the sun and with fire, probably because of their red and yellow feathers,” says anthropologist Andrew Somerville, currently at the National Autonomous University of Mexico, who has worked extensively at a site called Paquime in northern Mexico. “By sacrificing a symbol of the sun on this solar holiday, one was perhaps ritually ending the dry season and hastening the arrival of the spring and summer rains.”
Living Traditions
Some Native American equinox traditions are still alive. For the Lakota of the U.S. Midwest, the vernal equinox not only kicked off a seasonal migration in the Black Hills of South Dakota, but also a series of ceremonies meant to welcome life on Earth and send the souls of the deceased to briefly rest in the core of the Milky Way.
“Our people, for all these years, have done that,” says Victor Douville, who teaches the ethnoastronomy course at Sinte Gleska University on the Rosebud Reservation in South Dakota. Millennia ago, Douville says, the Lakota noticed that every spring, the sun rises in the constellation known as the Dried Willow.
“Those stars look like nubs on the branch, and the branch represents the red willow,” Douville says.
The inner bark of that red willow is the main ingredient used to make tobacco for the equinoctial Sacred Pipe ceremony, which is meant to rekindle the sacred fire of life on Earth. The ceremony is the first in a series of four that culminates with the Sun Dance on the summer solstice.
For a long time, scholars thought only settled, agricultural societies marked the movements of the heavens. Yet the Lakota, who followed great herds of buffalo across the U.S. Midwest, also timed their movements to the motions of the sun and stars. The ancient traditions that accompanied their migrations are still alive, and in some cases thriving, on the Rosebud reservation today.
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.
