A really hard but good question.
I'm not sure I can give you an adequate explanation but I will try, maybe we can both learn together
Sorry, my mistake:
~ㄴ 거예요 = Present tense
~ㄹ 거예요 = Future tense
In this pattern ~ㄹ/을 거예요 'something will be.' In this case 거예요
거야 is used as a supposition about things present as well as indicating the future when preceded by verbs having 'ㄹ' added to them. Some examples 알(know), 할(do), 살(buy), 먹을(eat) 거야
알 거야 - lit. will be known
I/he/you will know
할 거야 - (I) will do it.
살 거야 - (I) will buy it.
먹을 거야 - (I) will eat
I/we am/are gonna eat.
Supposition form: Michael이
알 거야, 걔한테 물어보자. - Michael will know, let's ask him. We suppose that Michael knows (now).
I've never heard anyone say '알다' to indicate 'knowing' in the present tense, instead '안다' is used "너도
안다" means 'you also know' 너도
아는 거야 -You also know this(it's obvious) or This is something you also know.
However, when you add '고' to '알,' it modifies '알' in such a way that it can now indicate knowing in the past and present.
알고 있었다 -already known
너 알고 있었다 - You knew it.
알고 있다 - is known
너 알고 있다 - You know.
A funny thing happens when you try to use 알 with the common tenses of 음니다:
압니다 - I know. I understand. (알아요)
알았습니다 - I understood. I see. I understand. (알았어요)
알겠습니다 - I see. I understand. (알곘어요)
So you see these 'players' can become turncoats depending on the combinations. This is why it is difficult to give a direct simple answer.
George - fellow student