This is debatable, but I'm in the camp that many worlds is testable against collapse interpretations, if not other interpretations. Seeing typical quantum observations for a macroscopic body would settle it pretty easily. We just need to be able to accelerate baseballs in baseball accelerators.
Not quite baseballs, but a couple of years ago, quantum superposition was observed in a 30 micron object, which is large enough to be seen with the naked eye.
Today's post, When Science Can't Help was originally published on 15 May 2008. A summary (taken from the LW wiki):
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