When you let two fingers touch in front of your eye and but focus on the background, why does it look like they are merging or ‘building a bridge between each other’ before they physically touch?

Question

When you let two fingers touch in front of your eye and but focus on the background, why does it look like they are merging or ‘building a bridge between each other’ before they physically touch?

In: Physics

Answer 1

Oh my god you put it into words! I’m not an expert in opthalmology but I think it’s to do with how the blurred edges of the fingers merge creating an overlap in the blur, therefore making the blur more opaque. Regarding the “bridge building”, I think what you’re seeing is your fingers touching ever so slightly but not enough for you to feel it so you think it’s just merging together. I hope this helps!