I'm not sure, but isn't it the case that Bose-Einstein condensates have been created (a collection of super cooled particles) and shown to behave as if they were a single particle?

Specifically, haven't physicists achieved putting such a condensate in a superposition? Wouldn't that count as a larger scale demonstration of superposition?

I can see that a virus is going to be much more complex than a bunch of uniform particles, but why should scale matter whether superposition is possible? Don't all objects experience some level of superpostion, only it occurs for immeasurably small time periods before wave collapse?

Exactly! But, isn't there a different (though related) question: Does it matter if the object (cat) is capable of making observations of its own? Is it possible that "being capable of observation" excludes the possibility of superposition?

I think we'd all agree that a virus isn't capable of making observations... but the cat is? (or if you have a problem with that, just place a person in the box)

Or maybe (BIG maybe), "being capable of observation" just requires a certain amount of complexity?

no, but you'd get simulated radiation and simulated (or artificial?) intelligence. The key difference is that your simulation of intelligence gets to interact with the outside world in much the same way that real intelligence gets to...simulated radiation not so much.

great theorems of mathematics. This book by William Dunham is a look at the lives and work of 10 or so great mathematicians throughout history.

The sections on Euclid and primes, Euler and infinite sums, and Cantor and the continuum are particularly good. Though it covers great and truly ingenious (even inspiring) mathematics, it should all be accessible to a high school student. Plus, the biographies are interesting in their own right and help to break up the parts where you actually have to concentrate.

I read this in my first year or so as an undergraduate, and I recommend it to anyone who wants to gain a feel for what mathematics is all about.