Ambient · northern lights
Aurora Clock
Slow curtains of green and violet light drifting over a starlit ridge line. The most colourful scene here, and one of the quietest.
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Press F for full screen. Motion pauses automatically if your system asks for reduced motion.
The real thing
What Causes the Northern Lights
Particles from the Sun
The sun throws charged particles outward constantly. When they reach Earth, the magnetic field funnels them towards the poles, where they collide with gases high in the atmosphere and make them glow. The aurora is that glow, seen from below.
Colour Comes from Altitude
Oxygen at around a hundred kilometres gives the familiar green. Higher up, above two hundred kilometres, thinner oxygen produces red. Nitrogen contributes blue and violet at the lower edges. The layered colours are a map of altitude.
Both Hemispheres Get Them
The northern aurora borealis has a southern twin, the aurora australis, and the two are near mirror images because the same particles arrive at both poles. The south simply has less land to watch from.
They Move Slowly
Real curtains shift over seconds to minutes, not instantly. This scene keeps to that pace deliberately, which is what makes it usable as a background rather than a distraction.
Under the hood
How This Scene Is Built
Three heavily blurred gradient bands drift and skew at different rates in screen blend mode, over ninety twinkling stars and a jagged CSS ridge line. Because the bands run on different cycles, the combined pattern takes a very long time to repeat.
If you find blurred moving colour hard to look at, the pause button holds the curtains still and leaves the colour in place, which still looks like a photograph of an aurora.
Answers
Aurora Background Questions
What actually causes an aurora?
Charged particles from the sun are steered by Earth's magnetic field towards the poles, where they strike gas atoms high in the atmosphere and make them emit light. The curtains follow the shape of the magnetic field lines.
Why are they usually green?
Because oxygen at roughly a hundred kilometres altitude emits green when excited, and that is where most collisions happen. Red comes from thinner oxygen much higher up, and nitrogen adds blue and violet lower down.
Is there a southern equivalent?
Yes, the aurora australis, which is close to a mirror image of the northern one. It gets watched less simply because there is far less inhabited land at southern latitudes.
Does this predict where I could see one?
No, it is decorative. Real viewing depends on geomagnetic activity, darkness and clear skies, and there are dedicated forecast services for that.
Why is the motion so slow?
Partly accuracy — real curtains shift over seconds to minutes — and partly usability. Slow motion in the corner of your eye is background; fast motion is a distraction.