Watch the moment spring officially sprung: Incredible timelapse video captured by a satellite reveals the sun shining directly over Earth's equator

Spring has finally sprung, which means days will keep getting longer from now until the summer. 

The season officially commenced as the sun shone directly over the equator and daytime and nighttime reached nearly equal lengths all around the world. 

Now, an amazing timelapse video shows the very moment this happened on Wednesday, at 3:06am GMT (Tuesday, March 19, at 11:06 pm EDT).

The clip is from GOES East, a space satellite operated by NASA and the National Oceanic and Atmospheric Administration (NOAA). 

For a whole year, GOES East snapped one still image per day at exactly the same time – 11:50 UTC – from the same position before stringing all the images together. 

Spring officially started on Wednesday, March 20 at 3:06am GMT (Tuesday, March 19, at 11:06 pm EDT). This still from the video shows the sun shining directly over the equator and daytime and nighttime reaching nearly equal lengths all around the world

READ MORE: Spring really has sprung! Sunworshippers bask in the rays as Britain enjoys above-average temperatures

A woman relaxes in St James's Park in central London on Wednesday 

The resulting animation shows the constant movement of the dividing line between day and night – known by some astronomers as the 'terminator'. 

'From their position 22,236 miles above the equator, the GOES satellites orbit at the same rate Earth rotates, so they can keep constant watch over the same region,' NOAA said in a statement. 

'GOES East geostationary satellite, also known as GOES-16, keeps watch over most of North America, including the contiguous United States and Mexico, as well as Central and South America, the Caribbean, and the Atlantic Ocean to the west coast of Africa.' 

Some people think 'spring' is an arbitrary name given to the time of year when the weather starts to get warmer and flowers start to appear – but that's not the case.

In fact, the four seasons (and when exactly they start) are all to do with the movement of the Earth in relation to the sun. 

Don't forget, out planet spins at an angle as it moves around the sun, so the amount of sunlight we get changes. 

Because Earth is tilted on its axis, the sun illuminates the northern or southern hemisphere more depending on where the Earth is along its orbit.

There are two equinoxes every year - in September and March - when the Sun shines directly on the equator and the length of day and night is nearly equal. During equinoxes, we experience pretty average temperatures and equal lengths of day and night

However, at two points in the year the Sun will illuminate the northern and southern hemispheres equally – known as the equinoxes. 

In the northern hemisphere, spring kicks off when the first 'equinox' occurs, which is when the shines directly on the equator.

It means the lengths of day and night are just about equal regardless of where you are on the planet – 12 hours or sunlight and 12 hours of darkness. 

The term 'equinox' is derived from Latin, meaning 'equal night'. 

The first equinox is officially called the 'vernal equinox' – and every year it happens on March 20 or March 21.

It marks the start of spring in the northern hemisphere and the start of autumn in the southern hemisphere. 

The second equinox is officially called the 'southward equinox' – and every year it happens around September 22. 

It marks the start of autumn in the northern hemisphere and the start of spring in the southern hemisphere. 

'This week marks the vernal or spring equinox, one of two points in the year when the number of daylight and night-time hours are the same,' Anna Ross, an astronomer at the Royal Observatory Greenwich, told MailOnline. 

NASA graphic explains the difference between the solstice and the equinox. The solstices take place in June and December; the equinoxes take place in March and September

The winter solstice is the day of the year when the Northern Hemisphere has the fewest hours of sunlight and the Southern Hemisphere has the most

'The Earth takes one year (or 365-and-a-quarter days) to orbit once around the Sun and it is tilted over slightly on its axis. 

'So for half of the year, the Northern Hemisphere is tilted slightly towards the sun, meaning we have longer daylight hours and hotter temperatures.

'For the other half of the year, we are tilted slightly further away from the Sun so we have longer nights and colder weather. It's this tilt that gives us our seasons.

'There are two points in the year where the Earth's tilt is at its most extreme relative to the Sun.' 

While the vernal equinox marks the point at which the Northern Hemisphere enters spring, the Southern Hemisphere enters autumn. 

For the Northern Hemisphere, the vernal equinox kicks of the countdown to the summer solstice – the longest day of the year and the start of summer – which this year will be on June 20. 

Solstices – which are essentially the opposite of the equinoxes – occur when the planet’s geographical pole in the Northern or Southern Hemisphere is most greatly inclined towards the Sun. 

'There are two points in the year where the Earth’s tilt is at its most extreme relative to the sun,' said Ross.

'These days are known as the solstices.

'On these dates, depending on which hemisphere you live in, you will either experience midsummer with the longest day of the year or midwinter with the longest night. 

'In between both of these extremes, we get our spring and autumn months, with the exact midpoints being the equinoxes.' 

The vernal equinox, which has been celebrated for centuries, is seen as heralding new beginnings and the renewal of the natural world

However, if you asked a meteorologist when the seasons start you might get a different answer.   

Wednesday marked the start of 'astronomical spring', which is actually one of two definitions of when the seasons start and end. 

Astronomical spring is different from meteorological spring, which always commences on March 1 and ends May 31. 

Meteorological seasons are based on the annual temperature cycle and are more rigidly defined by the months of the year. 

The Met Office explains: 'These seasons are split to coincide with our Gregorian calendar, making it easier for meteorological observing and forecasting to compare seasonal and monthly statistics.'