Translation:The world undergoes a crisis, people know it.
I took the sentence to be a response to somebody's rant...Allright, allright, the world is in crisis, we know it. ...Now what?
I guess Duo's take is more like a summary in the historical present.
The first world war starts
Millions are killed
The world undergoes a crisis, people know it.
Literature and art are changed forever.
Duo places a problematic sentence in front of students
The Green Owl swoops.
Things are back to normal.
How would one know to use a comma here instead of a period if this were spoken? The pause by the computer voice made me think that a period should be used. Furthermore, this is a comma splice in English and a period must be used. But I see commas used in French like this all the time.