Somewhere, in another universe, there's a John that understands what multiverse theory is. But it's sure as heck not this John! Is there any real scientific theory behind the multiverse? Or is it just comic book fare like in "Spiderman: No Way Home" or "Doctor Strange and the Multiverse of Madness"? Apparently the answer involves Einstein, quantum mechanics, and string theory. So safe to say, Dr. Ryan has his work cut out for him on this one.