Do the two ends of the green line passing behind the gate appear offset or aligned? The two ends of the line are completely aligned, although they appear to be offset.  If you don’t believe it, use something straight, like a ruler or sheet of paper, to confirm.  German physicist Johann Christian Poggendorff discovered this […]

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 […]