The world’s strangest optical illusions
The effect of Brocken Spectre is when an image of a shadow is cast within a circular rainbow. (Gareth McCormack/LPI)
Can you believe your eyes? When it comes to these head-twisters, chances are you cannot. From “God's burning finger” to the polar lights, here are 10 of the most extraordinary natural mirages that will leave you asking “Did you just see what I just saw?”.
Fata Morgana, Antarctica
Way up north (or way down south) the clear, pure air brings distant objects into sharp focus. Depth perception becomes impossible and the world takes on a strangely two-dimensional look. Fata Morganas are caused by light reflections off water, ice and snow. When combined with temperature inversions, they create the illusion of solid, well-defined features where there are none. Early explorers meticulously mapped islands, headlands and mountain ranges that were never seen again. One Swedish explorer described a craggy headland with two unusual symmetrical valley glaciers – when he was actually looking at a walrus!
St Elmo's Fire, Edinburgh, Scotland
Herman Melville called it “God's burning finger”. Caesar saw it on the javelins of his troops the night before battle. This spectacular effect (cause by the discharge of electricity from storm clouds to the earth) has always conjured thoughts of omens and divine intervention. Its name comes from St Elmo, a protector of sailors. Men at sea would welcome the sight, often seen on the mast of a ship during a storm, as it usually comes at the point where a storm is quietening down. The effect is also frequently seen on the heights of Edinburgh's Castle Rock.
Northern Lights, Alta, Norway
The Northern Lights are a dazzling Arctic and Antarctic display, with colourful sheets of light transforming the endless winter nights into natural lava lamps. Also known as the aurora borealis and aurora australis, the Northern Lights form when solar particles, thrown out by explosions on the sun, are drawn by the earth's magnetic field towards the north and south poles, colliding with atmospheric gases to emit photons, or light particles. What results are brilliant sheets of green, red, white, purple or blue light. At a latitude of 69 degrees north, the Norwegian town of Alta is renowned as an excellent base to see the lights.
Brocken Spectre, Goslar, Germany
For thousands of years, anyone lucky enough to witness this extraordinary optical phenomenon probably thought they were in the presence of God or undergoing their own spiritual rebirth. The traveller is confronted with an image of his or her shadow, surrounded by a halo of light, usually around the head. The phenomenon mostly occurs near mountain peaks when the air is moist and the sun is low. The name owes its provenance to the Brocken, which at 1,141m is the highest peak in the Harz Mountains that straddle the German province of Saxony-Anhalt.
Green Flash, St-Jean de Luz, France
A favourite of those with romantic imaginations, the Green Flash (or Green Ray) seems to capture something of the ineffable and transitory nature of existence. It is an effect seen at the end of the sunset, when a green spot or a green ray seems to shoot out of the sun. The causes of the illusion are complex and have to do with the refraction of light, the thickness of the atmosphere and the curvature of the earth. Try for a glimpse of it in St-Jean de Luz, the French town featured in Éric Rohmer's moody film Le Rayon Vert.
New-growth conifers, Mount St Helens, United States
This is one for a spring day. As you approach Mount St Helens in Washington state, you will see that the new, pale-green growth sprouting on the dark-green conifers forms an eye-bending pattern, almost like an op-art painting. Spread across the scale of the forest, the effect is startling. Mount St Helens erupted spectacularly in 1980, causing its north face to collapse in a shower of rocks and releasing a massive ash cloud. Fifty-seven people were killed and the landscape was instantly turned into a featureless moonscape. Since then, the area has been protected and allowed to re-generate. Visit the Mount St Helens National Volcanic Monument website to check out the webcam and visitor details.