Translation:The cat exists and at the same time does not exist.
It is Schroedinger's cat. The sentence deals with this thought experiment relating to particles physics. (Just to give you the keyword for a Google search; I' m not able to explain further...)
Here's the link to the wikipedia article: https://en.wikipedia.org/wiki/Schr%C3%B6dinger%27s_cat (I was on my phone this morning, and I can't handle linking etc on my phone very well.)
The original Schrodinger's cat was dead and alive at the same time, so this is a spin-off, but it still made me laugh.
I wanted to add the original version, but 죽다 (to die) wasn't introduced yet.
If I were Duolingo, I would mark Duolingo wrong for saying "the" instead of "that"
Both are accepted, and we are trying our best to add alternative translations!
I put "Whilst the cat exists, it does not exist" and was marked wrong. I thought 면서 was whilst?
Since Korean has no corresponding word for the, it is sometimes (actually very often) impossible to tell whether it is an apple or the apple that they are talking about, from the context. Then chances are it is an apple, as it is normal to use 그 in lieu of the in such cases.
This is the reason why most of the translations on Duolingo are missing the the/a equivalent translations when both are correct. The best a student can do is remember the other correct translation when Duolingo states that the your correct translation is wrong. At this point the missing the/a equivalent translations are probably the biggest category of translations missing in this Duolingo course.
That cat exists while at the same time does not exist. I thought 면서 was while?
Duo attempts to be cute here, like earlier references to "What does the fox say?" and "Animal Farm". If you ask me, here it didn't work (pedagogically). But , yes, Duo literally wrote "The cat is not while it is".
In the Duolingo notes it says that the conjunction -서 connects a sequence of events. In this sentence there is not a sequence, but two events that happen at the same time!! Please Mods write proper Notes or we're going to be very confused.