humm interesting and mind stimulating hummmmmmmm

Yep, all those silent letters k in know and knife, gh in thought etc, were once spoken, and still are in some English dialects. In Scotland they say " It's a braw bricht, moonlicht nicht the nicht." That is "It's a beautiful moonlight night tonight."

Hmmm, in Middle English, when those spellings were derived, the "k" didn't used to be silent, right?

i don't know if night and knight are pronounced the same.  it may be an affectation of dialect, but i've found that a k in front of an 'n' tends to be pronounced with a slightly greater emphasis, drawn out just slightly more.

now has a terse 'n'.  know has a longer 'n' sound, and it's softer.  night seems to emphasize the t and the i.  knight puts a greater emphasis on the n and the i.  it could just be something northeasterly in the u.s.  but i swear i can hear the difference a 'k' makes.

I want to know why we change tenses when describingn if a store in open.........................logically a store should be open or close or opened of closed.

I wouldn't consider them an ideal "primer" for silent "k" because they aren't, in linguistic terms, a minimal pair - two words that only differ in one phonological or orthographic respect.  "Now" and "know" aren't the best candidates because, while their spellings only differ in one way, their pronunciations also differ in an unrelated way.

A better solution would illustrate the silent "k" construction with two words whose spellings are otherwise the same, and whose pronunciation differs only in the presence or absence of the sound of the "k": in this case, nothing!  A nice pair for this, in my opinion, would be "night" / "knight"...particularly appropriate for the English-learning chess crowd!