I don't quite trust my own senses, and neither should you trust yours. Note the series of pictures below, taken at the joint of the ceiling and the west and south walls of my apartment. I noticed this effect many times before and today I'll present it to you.
Reason tells us those are three 90 degree joints because the walls and ceiling are all perfectly square, and when square things are placed together right angles result. But it sure doesn't look that way.
Note that the camera I used, my little friend the Canon PowerShot A1400, sees the same angles as my eyes do, so you see now what I do.
In the first shot the joints are clearly greater than right, or 90 degrees.
But note in the third, with the camera placed right against the west wall, the ceiling/south wall joint looks exactly a right angle.
I'm sure it involves distance to subject and angle of view, and I think I can partially understand that. But it evokes a deeper question: how many of my senses deceive me, and how often? Can I believe anything I see, hear, feel, taste, or smell? Maybe my world is one big illusion. Yours too.
If you desire to further distrust the world you live in and your own senses, check out the work of this man-
I have learned much from him.