Everyone is talking about the source of light, as if it can't be disputed... but what if it's night time? The lights could be anywhere, we have lamps and everything. Light source means nothing. Just like shadows also aren't factors, since they're made with light. And not all cats move the same. So, there's actually no way to know.
its going downstairs- first look at the lighting, then the shadows, then the cat's position. a cat doesnt look like that when its going up stairs!!! I should know, I have a cat. :-O what, didn't think of that? its so obvious!
Hm, it is definitely a very good illusion. But you can get easily confused and just pick 1 over the other. Only if you look closely at the picture. Examine it closely. The person behind the camera was at the end of the stairs and took this photo. How do you know exactly? Well, if you look closely at the stairs themselves, you can see the parts that make the ledges See More▼ coming forward, and the backs of the stairs inward, its complicated but if you look up different stairs you'll understand more. Those ledges/cliffs aren't seen going UPstairs but rather DOWNstairs (if you are downstairs like the person behind the camera). Have you ever fallen UP stairs? If you do not step before your foot runs into the back of the stair or close those little 'cliffs' will catch your foot, causing your fall, it is most common, not coincidence. Careful where you step, my pupils. ?
The sourse of the light is behind the cat, not in front of it.