converting wine to blood and bread to human flesh requires nuclear transmutation, not just chemistry

Okay, I haven't looked into this in any detail, but I must say this comes as a surprise. What elements are in meat that aren't in bread, or vice versa? (I had expected that they were both, pretty near entirely, carbon, hydrogen, oxygen and nitrogen, which is why the human body can digest bread and use it to grow - which is really a long-term way of transforming it into human flesh).

It can be something as prosaic as asking God to speak to two believers and tell them something -- anything -- but have it be the same thing in both cases.

Now, that would be interesting. It does require God's deliberate participation - in fact, all experiments to prove His existence do - so it's not going to work if He doesn't play ball. (Which brings us right back to the question of why He is so cagey about the whole existence thing at all...)

(BTW, Jesus actually got this wrong. It was not in fact written that thou shalt not tempt the Lord thy God. In fact, the Old Testament specifically calls on people to apply the scientific method to prophetic claims in Deuteronomy 18:21-22.)

There's a list of places where the new testament quotes or refers to the old over here. I see gjm's already found this quote, but it might save you some future searches in similar circumstances.