Serious music question about tonality in 12 tone equal temperament (and also just intonation)?

Okay, how does a half step interval sound like a whole step interval in a scale (this is in 12 tone equal temperament and just intonation) Like, in a C major scale, how does going from E to F (which is a semitone, or only 100 cents) sound as consonant as going from, lets say, D to E, which is twice as many cents (200) apart! That makes no sense to me, it seems like they would all flow well with a certain amount of cents (or hertz, however you want to measure it) apart from each scale step. But then when I try that, which in C major is C D E F# G# A# C, (whole tone scale) it actually sounds really dissonant? I know full music theory and love improvising on the piano, but this just caught my attention, so does anyone know why that is, that a semi tone sounds as consonant in a major scale as a whole tone? Thank you (: