In searching, the internet seems very divided on this question. I want to achieve microwaving nirvana.
I think that would damage the CD 🤣
All jokes aside, center while covered.
There are resonate standing waves inside the microwave. A microwave works at 2.4 GHz. The wave length of 2.4 GHz is 4.92 inches or just under 12.6 centimeters. This is a sinusoidal wave, so half of that wavelength distance is in the trough and half is in the hump of the waveform. These high frequency photons are bouncing around in a Faraday cage made of metal. Their pattern inside the metal box is fixed. The magnetron is off to one side and emitting the radio light from a fix position. As the waves of light bounce around inside, they tend to align into standing wave patterns. Some of the waves cancel out while others work together to amplify little extra energetic spots.
If part of your food is effectively stationary, like at the turntable center of rotation, there is a chance that a dead spot in the radio light wave pattern will form in that region and will not transfer energy to the food. The more the food is offset, the more it should cross points of radio light. So it is always more effective to offset the dish as much as possible.
If the bowl you are heating is smaller than the radius of the microwave’s glass-platter, then no problem, you can offset it to touch the outside of the platter and miss the centrepoint.
If the bowl is larger than the radius, I usually heat for half the time with one side of the bowl touching the outside of the platter, then slide the bowl to touch the opposite side of the platter, and then heat for the other half the cook time.
Even heat dispersion generally.
Fun experiment: take your turntable out, place in a large plate with pieces of the shittiest American cheese slices. We are talking kraft single serves. Splay them out, no deeper than one layer thick is needed, but make a full cover of the microwave bed (on top of the plate though. You will make a mess if not). Then you simply cook the shit out of it. You will see the cheese bubble and burn in the microwave wave peaks and you will see cold cheese in the wave troughs.
And then you pull out a ruler and measure how far apart the middles of the bubbles are. Look up the frequency of your microwave and then use that to calculate the speed of light with nothing but fucking cheese, a microwave and a ruler.
Rotation is good. It makes sure the food gets bombarded by microwave particles on all sides. If it’s on the edge of the turntable, though, the side facing the table would be colder because the microwaves take more effort to hit it, much like how the moon has a dark side because it’s tidally locked around the Earth.
I’ve seen the best results when I stack or pile food around in a doughnut shape, and center the hole of the donut shape on the turntable.
