Technically, the moment science would show an interaction between physical entities and something else, that something else would immediately be classified as a physical entity. In a very real sense, the discovery of radioactivity involved physical entities being found to interact with an as-yet unknown, invisible, intangible force.

If ghosts existed, the same would happen as with radioactivity. They would be researched, hypotheses on their nature would be tested, and a scientific theory would arise, and then they would be a part of the “physical world” too. And then all the mystics would be bored with ghosts because they are just incorporeal noospheric echoes of old people, as boring as neurology or biochemistry or stellar fusion.

Science has never in the history of science reliably shown a single interaction between physical entities and any sort of non-physical force.

Fucking magnets,

How do they work?

https://www.youtube.com/watch?v=_-agl0pOQfs

Saying “science has never reliably shown something” is not the same as “science has definitively proven something false.” Claiming otherwise is anti-scientific and logically fallacious.

According to the scientific worldview, we don’t know what we don’t know until we know it. Otherwise, we would never discover anything new.

I’m not saying ghosts are real. I’m just encouraging a healthy skepticism, whether for or against. So I’ll play devil’s advocate and respond in turn to each of your “million ways” it fails the smell test.

What makes a ghost exist?

We don’t know, but there’s a lot we don’t know. What makes gravity exist? What made matter and energy exist? What causes the big bang? What is the origin and nature of dark matter?

There’s a lot we don’t understand about the universe, so the answer could be as simple as a cloud of electrons or even photons, or as complex as a field of quantum fluctuations, dark matter, a previously undiscovered type of boson, a state of matter beyond plasma where the particles vibrate so rapidly that they’re mostly unobservable, a range of electromagnetic frequencies with wavelengths so fine that our instruments can’t detect them, or even an entity in a higher dimension that ephemerally crosses the plane of our familiar third dimension.

Why aren’t we positively lousy with ghosts?

The answer depends on the above, but it could be that we are and just can’t observe them under ordinary circumstances. Or perhaps there’s a different place where they go, or possibly a different dimension, and we only notice the ones who get stuck here somehow. Or perhaps there’s some sort of ethereal ecosystem which keeps the ghost population in check like birds do for insects.

Are there rules?

Probably, but there are plenty of rules in the universe we don’t understand. What rule is responsible for gravity? Why does dark matter behave the way it does? Why do quantum fluctuations behave the way they do? Why does spacetime behave the way it does? And why do quantum mechanics and general relativity seem to describe contradictory sets of rules for the same universe, albeit at different scales relative to the one at which newtonian physics are accurate?

Until we figure out unified field theory, dark matter, and that higher dimension thing, we can’t pretend we’ve described every rule in the universe.

What would they be and what mechanism is there to both quantify and effect them?

This has already been addressed under “what makes them exist?”

Why do ghosts follow the rotation and revolution of the earth but otherwise aren’t physically bound?

It could be that their physically-boundedness is just subtler than most things we’ve observed. They could maintain their relative position gravitationally or by friction, or possibly through electromagnetism, quantum entanglement, exertion of conscious effort, or simply some higher-dimensionality which allows them to be present anywhere they want at a given moment.

How can one have any sort of cognition?

How can any living human have any sort of cognition? There’s a lot we don’t understand there either. It could be that consciousness is a property of electromagnetic fields, in which case it would explain it if the ghosts were made of electron clouds. Or perhaps consciousness is a property of quantum fields, or something else we don’t understand such as a higher-dimensional entity with more complex states of matter and energy, that simply can only perceive and interact with the world in three dimensions because those are the limitations of the physical organism it has developed to inhabit and maintain itself.

So the answer to ghost cognition depends on the answer to human consciousness, which is still one of the major mysteries of the universe.

Alternatively, perhaps ghosts aren’t conscious at all and only appear to be, but they’re really more like a complex sort of jellyfish, mindlessly following patterns that were set by the mind of the conscious entity prior to the death of the physical organism.

If a ghost does, how can it perceive anything without intercepting photons or other physical phenomena?

Perhaps it directly perceives electromagnetic waves that enter its field of existence, or perhaps there’s some higher-dimensional perspective that allows them to observe the 3-dimensional world from the outside.

We don’t intercept photons when we dream, yet our brains construct images. So physical sensation is not a necessary precondition to mental perception.

If there are ghosts and somehow they have cognition and perception, are we obligated to leave Netflix on when we leave for work?

No, that’s when they’re busy conspiring with your cats. And I’m sure they would have plenty of entertainment observing the antics of the living without requiring mortal means of diversion.

I think you could rationally explore ghosts in the “radically redefining” them arena. Ghosts could rationally exist as an artifact of your mind, and saying that is not the same thing as saying they don’t exist. Hallucinations exist. They aren’t real, but they exist. Ghosts could rationally exist in the exactly same way, as processes in our own heads. It’s when you start saying they interact with the world in a way outside people’s heads that you can’t really reconcile.