The word Tian is not simplified and there are no traditional Chinese characters.
天 tiān
1. Understanding. Oracle glyphs. The bottom is a frontal human figure (large), the top indicates a human head, and the small seal characters become a horizontal line. Original meaning: the top of a person's head.
2. Same original meaning
Heaven means top. ...The top one is the top among people. Known as Van Gogh. ——"Shuowen Jiezi Annotation"
Tianzi Oracle Bone Inscriptions
Shang. Yin Ruins Oracle Bone Inscriptions