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**GordMay** · 22-03-2022, 02:05

The difference between a solstice, and an equinox comes down to length. At the two equinoxes, the days and nights are almost of equal length, whereas the solstices mark the shortest (winter solstice), and longest (summer solstice) days of the year.

During the equinoxes, the Sun is directly above Earth’s equator, giving us (nearly) equal hours of daylight and darkness.

During the summer solstice, the northern hemisphere is at its maximum tilt towards the Sun, so the Sun appears at its highest, giving us the longest day of the year. During the winter solstice, the northern hemisphere reaches its maximum tilt away from the Sun, so the Sun appears at its lowest in the sky, giving us the shortest day of the year.

**GordMay** · 22-03-2022, 02:09

The March equinox denotes the start of spring, in the northern hemisphere, and the start of autumn, in the southern hemisphere.

The March equinox 2022 ['spring' in the northern hemisphere], was on Sunday 20 March. The spring equinox marks the first day of spring, and the precise time of the equinox was at 3:33pm GMT.

When it’s the spring equinox, in the northern hemisphere, it’s the autumn equinox, in the southern hemisphere.

The spring equinox is when the Sun crosses the celestial equator, going from the southern hemisphere, to the northern hemisphere. As the Sun is exactly above the equator, both the northern hemisphere, and the southern hemisphere, receive nearly equal amounts of the Sun’s rays. In other words, the day and night are (almost) equal in both hemispheres.

In reality, we will actually be seeing a few more minutes of sunlight, at the spring equinox. This is thanks to refraction in the atmosphere, that bends the Sun’s rays, causing the Sun to appear above the horizon, when it’s actually below, resulting in slightly more daylight than darkness.

The exact point at which the Sun crosses the celestial equator during the spring equinox is known as the ‘First Point of Aries’. Back in the day, when the equinoxes were first observed by the Greek astronomer Hipparchus in 130 BCE, this point lay in the constellation Aries. Now, because of precession (as it rotates, the direction of the Earth’s axis wobbles and changes direction), it lies in the constellation of Pisces.

The First Point of Aries is slowly moving towards the constellation of Aquarius, at a rate of around one degree every 70 years. So, by the year 2597, the First Point of Aries will actually sit in Aquarius. It won’t be for another 23,000 years that the First Point of Aries will return home to its namesake.

The March equinox occurs with approximately a six-hour difference from the previous year. The equinox this year, in 2022, was at 3:33pm, and next year, in 2023, it will be around six hours later at 9:24pm GMT. But you don’t need to worry about remembering new dates every year; we’re stuck with the March equinox being on 20 March until 2044, when it’s on 19 March.

Declination is the angular distance, measured in degrees, of the Sun north or south of the celestial equator. When the Sun crosses the celestial equator at the equinox, the Sun’s declination is exactly 0°, as it’s not offset to the north or south. This happens twice a year, and, as a result, the gravitational effect of the Sun on the Earth is greater during the equinoxes.

This means that the Sun exerts a stronger pull on the Earth, because the equator of the Earth is lined up with the Sun. This results in a higher gravitational pull on the tides, and the tidal bulge gets bigger. Tides at this time are known as ‘equinoctial tides’. So watch out for greater-than-average ranges, between high and low tide.

Aurorae and major geomagnetic storms tend to occur more frequently around the equinoxes.
During the March equinox, the south pole of the Sun is tilted towards Earth (the reverse is true during the September equinox, when the north pole of the Sun is tilted towards the Earth). The magnetic field lines around the Sun’s equator loop back around, and back to the surface. But at the poles, they are open to space, extending out into the interplanetary magnetic field.

Although still poorly understood, during the equinoxes, it is thought there is more contact between the magnetic field lines of the Sun’s poles, with those of the Earth. When one of the Sun’s poles is tilted towards the Earth, it’s easier for ejected material to travel along these lines, until they interact with the Earth’s magnetosphere. The charged particles, that make up this ‘solar wind’, collide with nitrogen and oxygen molecules, resulting in the massive, dancing bands of the aurora.