Board Thread:Questions and Answers/@comment-30535075-20180216171039

Aizen has feats of been able to sense people from other dimensions.

The Muken is a different dimension separated from Soul Society: https://noobabble.files.wordpress.com/2013/01/l014.jpg

Aizen was able to sense Yhwach's remaining reiatsu from inside that dimension: http://mangaseeonline.us/read-online/Bleach-chapter-686-page-15.html

The Royal Palace exist in a different dimension:

http://mangaseeonline.us/read-online/Bleach-chapter-223-page-7.html

Aizen senses Ichigo in the Royal Palace:

http://mangaseeonline.us/read-online/Bleach-chapter-624-page-6.html

(Look previous pages no one told him that info.)

Aizen knew Ichigo and Yhwach were fighting in the Royal Palace:

http://mangaseeonline.us/read-online/Bleach-chapter-682-page-13.html

(Last time he saw Ichigo he had lost his powers.) 