The other day I put a plate of food in the microwave, set the timer and started it up. After it had been going about a minute, I looked in and noticed a fly buzzing erratically (in other words, in typical fly-fashion) around in the microwave. I opened the door and the fly flew out, as far as I can tell, feeling fine. My mother’s hypothesis is that flies can detect the waves and it was flying to avoid them. 
I don’t share her optimism, but I’m interested to know what kept it alive.
Im sure its wrong, but I absolutely LOVED your mothers explanation. The idea of a fly dodging microwaves would make for a great cartoon.
My guess is that microwaves heat objects by resonating the water molecules contained therein, and the more thermal mass an object has, the more it can be effected by the microwaves. Since flys have pretty much no thermal mass, they wouldnt notice them at the concentrations per square inch in a microwave oven. I’m going to try putting a single drop of water into a microwave and see if it heats up to test this.
apparently I am correct. The effectiveness of the microwave appears to be proportional to the thermal mass and moisture level of the object. I put a drop in one cup, and about 1/4 cup of water in another, and found that the 1/4 cup got too hot to dip my finger in over 30 seconds on high, but the single drop’s temperature hadnt changed appreciably. Facinating.
It’s not the mass, it’s the size. Microwave ovens operate at 2.45 GHz, and the emitted radiation has a wavelegth of about 12.2 cm. The smaller the object is in relation to this length, the less effectively it will absorb radiation. Thus flies and drops of water are less affected by microwave energy at this frequency than glasses of water or cats.
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I nuked a roach! He didn’t die! Why? (24-Sep-1982)
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When I was an undergrad, we had a microwave oven down near the vending machines in our dorm. By the time I got there, however, it no longer worked. The inside was a mess, in part (I was told) from too many people putting grasshoppers in there and nuking them.
Grasshoppers are bigger than flies, and thus having enough mass to cook faster. But I’m sure you can microwave flies, with enough time.
[hint, hint)
BUY the friggin’ book already folks.
Are you out of your mind??? Don’t you realize in a few days your going to have a Giant Mutant Fly in your house? Possible with some sort of telepathic powers? (Either that or one that’s been genetically spliced with whatever you were cooking - Half Fly Half Potato!!!). Have we learned nothing from a half century of comic books and horror movies??? Get out! get out while you still can :eek: :eek: :eek: !!!
The mother may be partly right, well, sort of partly right. Whilst I’m sure that not even a fly’s reflexes are fast enough to allow it to dodge beams of energy, there are such things as ‘cold spots’ in some microwaves - zones where the radiation is less concentrated; a fly’s nervous system is sophisticated enough to make it take flight when there is some kind of adverse or ‘painful’ stimulus and/or stay still when there isn’t.