Poggendorff Illusion
Looking at the figure on the left, does the blue or red line appear to intersect with the black line to the left?
While it doesn’t look like it, the red line is actually aligned with the black line as shown on the figure to the right. This illusion is known as the Poggendorff Illusion as it was discovered by German physicist Johann Christian Poggendorff in 1860.