I have a student who is actually arguing with me that the latter is also correct when using it in the following example:
'Have you ever known that Russia is the largest country in the world'
Now as a native speaker this sentence sounds awkward and unnatural to me but I've been racking my brain and I can't think of any rules that support the fact that " Did you know..." would be more appropriate other than the fact that it's used more widely in this way.
Am I wrong?. If you could provide a solid explanation and perhaps some links to help back me up I would be ever so greatful.
Thank you :)