Things I don't know

With a lot of things that are related to science, I generally have a ballpark idea of how to answer the question, though I'll have to up my game fairly soon as my son starts in on more serious science classes.  Of course, one can never keep all with all the innovations (I still am pretty stuck on "brontosaurus" and not "apatosaurus" for example).  But every now and again, I find myself really stuck to the point where I half wonder if I should send in a question to "Ask Cecil."  I had quite a doozy the other day, but it has slipped my mind.  Anyway, I'll list some of the more intriguing things that have been puzzling me.  I'll add some more as they come to me.

What is the largest animal that has actually been caught in a spider web, not just somewhat inconvenienced?  A related question is what is the largest animal that spiders actually treat as prey?  (Perhaps this should be split into spiders that use webs and those that don't.)

What are the practical implications of the earth running out of helium?  Will this actually occur in the next 100 years?

I have great difficulty in understanding how "quantum computing" would be stable enough to be practical.  (One would hardly want the cells in one's spreadsheet to be blank until one actually observed them...)  Is there actually anything quantum about the process, or is it mostly marketing?

Now I remember one that I occasionally think about from hearing about it in school -- the miracle of Dunkirk.  Now clearly it was pretty amazing that so many Allied troops were rescued, but the teacher claimed the "miracle" was how this rescue effort was coordinated, since there was supposedly complete radio silence -- all the ships and fishing vessels and so on just showed up spontaneously.  I imagine this aspect of the rescue was overblown and someone managed to get back across the Channel with the news and bring back help.  Still, I may need to do a bit of research into this.

Anyway, if anyone has some insights into these or any other puzzlers I may add, feel free to comment.  Thanks in advance.