Why This Stuff Costs $2700 Trillion Per Gram - Antimatter at CERN

The part about antimatter possibly falling upward got me thinking, and I thought I'd share my thoughts. Half, if not most of this is unrelated but I thought it was interesting:

If antimatter had negative mass then when you tried to push a positron into a container with a positively charged plate, it wouldn't work. This is because of f=ma, or a=f/m, if you try to repel the positron into said container with a positively charged plate, the negative mass actually makes the acceleration negative as well, so the positron heads *towards* the plate. As this does not happen, we know they don't have negative mass.

Negative masses also still fall in normal gravity, however. f=mg, so the negative mass means the object is pushed by gravity.
But again, as a=f/m, the negative mass means this pushing force accelerates the object toward the positive mass.
So the reason for antimatter falling upward wouldn't be negative mass, but some other property.

As far as I can tell, negative mass must be impossible. This is because while positive masses attract negative ones, negative masses repel positive ones. The pushing force exerted by the positive mass on the negative one must, by Newton's laws, mean that the negative mass exerts a pushing force of equal magnitude on the positive mass. As its mass is positive, it is indeed repelled.

So we have an object being repelled by another object, which is itself being attracted to the first. They will follow each other, accelerating ad infinitum. Now let's attach this system to the end of a pole, with a generator in the middle. Infinite free energy as the two follow each other in a loop, turning the generator to produce energy. Infinite free energy is of course impossible as per the laws of thermodynamics, and so negative mass must be too.

I could be wrong, so look it up if you're interested.