Are you ready for a mind-bending challenge? This optical illusion has taken the internet by storm, leaving many puzzled. It's one of the trickiest visual illusions online, and only the sharpest ...

SCIENCE has lost one of her most diligent and devoted servants by the death of Prof. Dr. J. Poggendorff, in Berlin, on January 24, He was born in Hamburg on December 29, 1796. The early deaths of ...