why is the image inside our eyes upsidedown?

I have a nice story for you on this topic. There were once a bunch of scientists that made an interesting experiment with one men's eyes. They made him wear a pair of glasses that made him see upside down. He wasn't supposed to take them off even when he slept for the next 3 days. In the forth morning, the scientists made him take of the glasses and the man sight was upside down. They left him like that for the next 3 days and then his sight came back to the normal position. I think that if the image would form normally on the retina then we would see upside down, but the brain will soon correct it :)