Is gravity just entropy rising? Long-shot idea gets another look

Toy Models of Gravity and “More Space”

• Some participants propose intuitive pictures: particles jostling thermally have a slightly higher chance of diffusing toward regions with “more space,” interpreted as spacetime curvature, leading to effective attraction.
• Critics ask why there should be “more space” between bodies, how such a model yields real acceleration and solid objects, and point out it implicitly leans on general relativity without adding explanatory power.
• Others liken it to older kinetic or shadow-gravity ideas (e.g., Le Sage-type models) and note these usually fail due to drag, heating, or conflict with observations.

Entropy, Temperature, and Mass-Energy

• Several comments discuss that hotter bodies gravitate very slightly more (via E = mc² and the stress-energy tensor), but the effect is tiny and practically unmeasurable.
• A question arises whether a body at absolute zero would be gravitationless; replies stress rest mass dominates over thermal energy, so gravity persists even at 0 K.

Cosmology, Low Entropy, and Gravity

• Some tie the Sun’s “low-entropy” radiation to gravitational clumping: self-gravity allows matter to collapse into hot, luminous stars starting from an initially low-entropy universe.
• There is discussion of inflation, Big Bang vs. bounce scenarios, and the difficulty of explaining how a prior high-entropy universe could seed a new low-entropy one.
• A side debate: whether empty, uniform space is low or high entropy, and how gravitational degrees of freedom complicate that picture.

What Is Entropy, Really?

• Large subthread over whether entropy is “just ignorance” or an objective physical quantity.
• One side: entropy always involves probability distributions; with perfect microstate knowledge, entropy is zero, so it is epistemic.
• Other side: thermodynamic entropy tracks real physical behavior (melting ice, tangled cords) and is defined for macrostates independent of human observers.
• Links are made between thermodynamic and information entropy, Maxwell’s demon, and minimum description length, with clarifications that “order/disorder” is shorthand for macrostate multiplicity.

Status of Entropic Gravity Theories

• Some find entropic gravity compelling as an emergent, statistical explanation: gravity as an effective entropic force rather than a fundamental interaction.
• Others worry these models are highly tuned, require unseen media or baths, and so far mostly re-derive Newtonian gravity, not full general relativity.
• Experimentalists emphasize the need for clear, distinct predictions (e.g., MOND-like regimes) to make such theories falsifiable; otherwise they risk being elegant but untestable reinterpretations.