Big full Moon tonight and it's a good night to test the horizon illusion. When the Moon is on the horizon, cover one eye, uncover it, cover it, uncover it. Notice the Moon instantly changes size. Your brain, despite being aware consciously of the horizon illusion, cannot shut the illusion off. But if you block the 3D image from your retina, it can. In 2D, the Moon looks its natural size. In 3D your brain adjusts the size you perceive (for all intents and purposes the size you are sure you see) in relation to as if it were an object on Earth on the horizon. Your brain says, this is the size of the Moon based on the evidence hitting the retina. You believe your brain is saying, this is the size of the Moon based on the light entering the eye. And here you thought you were in control.