People have been left rather confused by a mysterious building that appears to get smaller as you get closer to it.
When Emma Shand posted a video of Port Colborne, Ontario's 'shrinking mill' on TikTok, it left people baffled.
In the clip, she says: "Hey guys, we're going to be showing you the shrinking mill today in Port Colbourne. This is a mystery in Ontario, Canada that nobody really knows how it works."
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As Emma's car drives along a tree-lined road, she points out the building in the opening at the end of the street and tells viewers to 'watch the size of it as we get closer and closer.'
She explains: "Now, normally as you drive closer to something, wouldn't you think it gets bigger? But in this case, it shrinks, hence the name the shrinking mill."
True to her word, as the car nears the end of the road, at the closest point to the mill, the building appears far smaller than it was 30 seconds prior.
Social media users could hardly believe their eyes as they watched the mill shrink into the distance.
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One person wrote: "I don't like what this just did to my brain."
Another chimed in: "Glitch in the matrix."
But, there's actually a perfectly reasonable explanation behind the mind-boggling optical illusion called the Ponzo effect or 'moon illusion.'
It refers to optical illusion which occurs because our brain interprets the size of an object based on its surrounding context
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In the case of the shrinking mill, it has everything to do with the viewer's ability to see the horizon line.
When the car is first approaching the mill, you can't see it, leading the building to appear much larger than it actually is.
But as the car drives towards the bay and the surrounding horizon is revealed, it causes your perception to constantly readjust, giving the effect that the mill is shrinking at a rapid speed.
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Despite the rather simple explanation, tourists still travel to the area to see the trippy illusion for themselves.
"As much as we take it for granted, when people see it they're just in awe," a local resident told the Welland Tribune.
They also said that tourists are really easy to spot.
"They turn off of Cement Road, slow almost to stop and look at it, and then nine times out of ten, you see them drive by again a few minutes later."