Have you ever witnessed the image of a flying ship, a silhouette with a halo, or a ghostly city hovering over the sea?
If you are a fan of fantasy stories or movies like Harry Potter or Pirates of the Caribbean, images of flying ships and hovering vehicles are not unfamiliar.
While these images may seem like they belong only in fantasy films, in reality, from a scientific perspective, seeing such images in real life is considered an optical illusion.
Optical illusions can deceive our vision as they appear just like real objects when we are in a particular environment. Below are some of the most common optical illusions found around the world.
1. Fata Morgana
For sailors, Fata Morgana is a surreal optical illusion that no one wants to encounter during sea voyages. This illusion typically appears on the horizon over oceans and seas, especially in polar regions. It makes distant objects, such as another ship, appear to be floating in the sky.
Usually, Fata Morganas occur when light is refracted (or “bent”) by contrasting air temperatures with the sea surface temperature. However, this phenomenon can also occur over lakes or deserts, not just in oceans.
2. The Brocken Spectre
Named after the Brocken peak in Germany, this optical illusion was first discovered by mountaineers. These individuals noticed ghostly figures seemingly looking at them through the mist above. The head of the “spectre” is often surrounded by colorful light rings similar to halos, creating a radiant aura.
In reality, this is merely their own shadow being diffracted, similar to how rainbows form when sunlight passes through tiny water droplets in the air.
3. Sun Dog
This phenomenon, also known as Sundog, features bright spots appearing on either side of the real sun. In many cases, they even create a faint halo in an arc shape.
This phenomenon occurs when sunlight is refracted by ice crystals in the atmosphere. Sun Dogs often appear at sunrise or sunset and can be seen anywhere in the world at any time of year. They are called Sundogs because they always follow the sun, just like a dog follows its owner.
4. Mirage in the Desert
This phenomenon is likely familiar to fans of Hollywood films. It is an occurrence in the desert where a mirage presents an oasis with a pool of water, trees, and cool air amidst the harsh daytime weather.
However, as we approach, there is no oasis to be found. This is known to occur when light is bent while passing through warm, less dense air.
In the desert, the hottest air is near the sand surface and cools as it rises. Therefore, when light is refracted downward, it causes our eyes to perceive a blue color beneath the horizon.
5. City on the Sea
The optical illusion of a city on the sea is a unique phenomenon documented since 1840 when a resident living on a small island in England discovered it. This illusion reveals a ghostly image of a vast city with tall buildings suddenly appearing in a hazy mist, leaving many astonished.
However, like other phenomena, this is also a result of light being reflected off objects, continuously changing direction before reaching our eyes.
