It occurs to me that there are several entirely different types of things which would indicate "Atomic Theory may be Wrong."
1: You look into an Electron Microscope, expecting to see Atoms. You see Infinitely divisible Swiss Cheese spelled out into the shape of the word "Nope."
2: You use an ultra accurate scale, expecting to weigh something at 1.255000001. It weighs 1.255000002. Because the integral weight of the subatoms, subsubatoms, subsubsubatoms etc, causes your measurement to be off.
3: I am inexplicably transported to "Fantasia." Atomic theory doesn't work here because Fantasia is constructed from strange matter, namely infinitely divisible magicons, but it does still work on Earth, which is in fact still made of ordinary matter.
4: I am in the middle of looking into a Microscope which is broadcasting onto a TV. everyone is suprised to note that at 12:00 noon exactly, the Atoms suddely appeared to be more divisible than they were before.
5: Omega shows up and I am informed that I am in a simulation which does not actually use real world physics. Instead, it uses simplified physics.
Ergo, if Atomic Theory is invalid, it brings up the question of how it is invalid:
Does it work on everything except this thing? Does it approximately work on everything, but doesn't exactly work? Does it work on everything in a particular area, but not in other areas? Does it work at some times and not at others? Does it only work because it is the rules of the simulation?
This is important, because for instance, If there's a 1% chance that I'm in a Omega simulation, and a 1% chance that an Omega simulation is not being run using the real worlds physics, then even if I was 100% confident that Atomic Physics described my simulation (which I shouldn't be), my confidence that the Atomic theory correctly describes the real world shouldn't exceed 99.99%, if I've been doing the math correctly.
So I feel like the answer is, my number doesn't describe anything without some kind of shared context between me and the person.
How much confidence do you place in the scientific theory that ordinary matter is made of discrete units, or 'atoms', as opposed to being infinitely divisible?
More than 50%? 90%? 99%? 99.9%? 99.99%? 99.999%? More? If so, how much more? (If describing your answer in percentages is cumbersome, then feel free to use the logarithmic scale of decibans, where 10 decibans corresponds to 90% confidence, 20 to 99%, 30 to 99.9%, etc.)
This question freely acknowledges that there are aspects of physics which the atomic theory does not directly cover, such as conditions of extremely high energy. This question is primarily concerned with that portion of physics in which the atomic theory makes testable predictions.
This question also freely acknowledges that its current phrasing and presentation may not be the best possible to elicit answers from the LessWrong community, and will be happy to accept suggestions for improvement.
Edit: By 'atomic theory', this question refers to the century-plus-old theory. A reasonably accurate rewording is: "Do you believe 'H2O' is a meaningful description of water?".