[meindnoch]

Sure, I'm not denying that entropy exists as a concept, that can be used to explain things macroscopically. But like you said, it's origins are statistical. To me, temperature is also a similar "made up" concept. We can only talk about temperature, because a sufficiently large group of particles will converge to a single-parameter distribution with their velocities. A single particle in isolation doesn't have a temperature.

So if they say gravity might be an entropic effect, does that mean that they assume there's something more fundamental "underneath" spacetime that - in the statistical limit - produces the emergent phenomenon of gravity? So it isn't the entropy of matter that they talk about, but the entropy of something else, like the grains of spacetime of whatever.

[nearbuy]

When you go deeper into physics, mass and energy don't seem real either, in that, like entropy, they're emergent properties of a system rather than fixed, localized things.

I always thought of the energy of a system (kinetic + potential) as a useful mathematical invariant that helps us predict systems rather than a physical thing. If you put a cart at the top of a hill, then the cart has more potential energy (but only from certain reference frames). It doesn't feel like that potential energy is physical. It doesn't have a specific location; it's a property of the whole Earth-cart system. And yet, it's this total energy that gives rise to the physical properties we're familiar with. In fact, almost all of the mass in your body comes not from the mass of elementary particles, but from the potential energy in the bonds between quarks. Your mass is more than 99% from potential energy.

And then when you get into Quantum Field Theory, it turns out particles (like electrons) are no longer truly point particles but rather another emergent phenomenon from ripples in an underlying field. A particle is just a model that describes it well when looked at from a distance. (I hope I'm not butchering that, as I'm not a physicist.)

So mass, matter, energy, and entropy are all emergent properties of a system rather than being localized, "real" things in the way we'd intuitively think. And at that point, I'm not sure how we would define "real" or why it would be a useful distinction. Is there a useful insight to be gained by putting entropy in a different category of realness than mass?

[flufluflufluffy]

Yes, exactly. The model is based on (in the first approach) a “lattice” of some type of undiscovered particle-like thing (what they refer to as “qubits” in the article, which is unfortunate because it is NOT the same “qubit” from quantum computing) permeating space time. Or maybe more aptly, it is that lattice from which spacetime emerges. And what we observe as the force of gravity emerges from the entropic forces happening in this lattice.

[spacecadet]

Im an idiot, let's get that out of the way first. I think that your temperature analogy answered your own question.

I guess my question in turn is, if we imagine a universe at the end of time(?), one that maybe dominated by a few black holes and not much else. Would an observer experience gravity if place sufficiently far enough way? Or even further, if nothing is left in the universe at all. Assuming that doesn't cause a big crunch, rip, or whatever...