As long as I know, it's not Einstein who came up with the theory of relativity.

Hi.

I'm familiar with the phrase 'as far as I know', and I've used that a lot.
'So far as I know' is, as far as I know, a similar one.

Is 'as long as I know' almost the same one as 'as far as I know'?
The expression that comes to my head first is 'as long as you love me', 
which is also the title of a song by a singing band 'Westlife'.

The song goes like, 
'I don't care who you are, where you're from, what you did, as long as you love me baby.'

The singer said he wouldn't care what his lover did or where she came from only if she loved him.
Nothing would matter only if she loved him. This is what the lyrics are all about, I suppose.

Now, instead of 'as far as I know', if I said, 

'As long as I know, the one who came up with the theory of relativity is not Einstein, but his wife.' 

Would it make no sense?

My quick Google search showed me quite a lot of 'as long as I know' examples, 
but I'm not quite sure if they mean the same thing as 'as far as I know.'

Could you please share your thoughts?
Any comments will be appreciated.
Thank you in advance.