The phantom lighthouse: new research explains one of Australia’s strangest illusions
Visitors to Lady Elliot Island report seeing a lighthouse far out to sea at night – and scientists have at last figured out why.
A strange optical illusion has been puzzling visitors to Lady Elliot Island, an Australian gem at the edge of the Great Barrier Reef. The phenomenon involves seeing a phantom lighthouse shining on the horizon at night, a sight that has captivated observers for over a century. The first known report of this illusion dates back to 1937, and it has since been documented off the coast of Brittany, France. But what causes this illusion that seems to challenge our perception of reality?
To unravel the mystery, researchers traveled to Lady Elliot Island to investigate the illusion firsthand and recreate it in a virtual reality environment. This approach allowed them to better understand the underlying mechanisms at play. The illusion appears to occur when our brains combine expectations with sensory evidence, leading to an incorrect interpretation of the scene.
To observe the illusion, participants stood at least 70 meters away from the lighthouse, facing away from it while looking out at the sea. Despite knowing that the light is coming from behind them and not from the horizon, they still perceived the phantom lighthouse shining on the horizon. The virtual reality recreation of the experience provides a sense of what it feels like to witness this eerie illusion.
In a recent study, researchers examined the natural illusion on Lady Elliot Island and replicated it in a virtual reality setting. Their findings suggest that the illusion is a result of the brain merging expectations with available sensory data. At night, with limited distance cues, the visual system needs to rely on expectations about the distance of different parts of the lighthouse beam.
Much like the "crater illusion," where a photograph of a crater can be mistaken for a dome or hill, our expectations about the distance and movement of the lighthouse beam lead us to perceive the phantom lighthouse.
The phantom lighthouse illusion demonstrates the brain's role as a "prediction machine," constantly combining expectations and current data to make inferences about the world. While this ability generally helps us make accurate interpretations of our environment, it can sometimes lead us astray. In the case of the phantom lighthouse, the brain interprets the light as coming from a source in front of the observer due to the expectation that distant objects should move slower than closer ones.
This highlights the delicate balance between our brain's predictive prowess and the potential for errors.
Written by urgent.news from The Conversation AU's reporting — not their text. Machine-written — may contain errors; check the original before relying on it.
