Autumn equinox
| 09:25 UK time, Tuesday, 22 September 2009
The weather has been on top form in Wales recently with very little if any rain for almost a fortnight.
A cold front will bring a little rain today but things are looking up again later this week.
High pressure bringing another dose of fine, settled weather and some sunshine.
Today is the Autumn Equinox. And some people take this day as the official start to Autumn in the Northern hemisphere.
The equinox refers to the moment that the sun crosses directly overhead at the Earth's equator.
The word equinox derives from the Latin words aequus (equal) and nox (night). It means equal day and night. But in reality, the day is longer than the night at an equinox.Ìý
This is because the sun is not a single point of light, but appears to be a disc. So when the centre of the sun is still below the horizon, the upper limb is already visible and emits light.
The atmosphere also refracts light downwards, so even when the upper limb of the sun is still below the horizon, its rays already reach around the horizon to the ground. This combination makes the day slightly longer than the night.
In Cardiff, day and night are equal on September 25th a few days after the Autumn Equinox. At the South Pole the penguins will be celebrating the first appearance of the sun in 6 months.
At the North Pole polar bears will be bracing themselves for 6 months of darkness.
Here in Wales the nights are drawing in but cheer up - there are only 93 shopping days left until Christmas! ;0
Derek
A cold front will bring a little rain today but things are looking up again later this week.
High pressure bringing another dose of fine, settled weather and some sunshine.
Today is the Autumn Equinox. And some people take this day as the official start to Autumn in the Northern hemisphere.
The equinox refers to the moment that the sun crosses directly overhead at the Earth's equator.
The word equinox derives from the Latin words aequus (equal) and nox (night). It means equal day and night. But in reality, the day is longer than the night at an equinox.Ìý
This is because the sun is not a single point of light, but appears to be a disc. So when the centre of the sun is still below the horizon, the upper limb is already visible and emits light.
The atmosphere also refracts light downwards, so even when the upper limb of the sun is still below the horizon, its rays already reach around the horizon to the ground. This combination makes the day slightly longer than the night.
In Cardiff, day and night are equal on September 25th a few days after the Autumn Equinox. At the South Pole the penguins will be celebrating the first appearance of the sun in 6 months.
At the North Pole polar bears will be bracing themselves for 6 months of darkness.
Here in Wales the nights are drawing in but cheer up - there are only 93 shopping days left until Christmas! ;0
Derek
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