Loan amortization interest?

Joe asked:


I understand loan amortization for the most part. I understand you are figuring out a schedule of equal payments over a period time, and how often the interest is compounded, along with the given iterest and principal of the loan.

My question is, Why does the amount of interest decrease over time as the principal falls.

I know the payments add up to the total amount of the principal plus all the interest compounded, so why isn’t the interest equally split. My book doesn’t say why. they just say that it happens.

Thanks

probably not something i need to know, but it’s important