4 ms·
I was literally thinking of the same similarities. Barbour's exposition of the principle of least action as being time is interesting. There's a section in The
by pizza 2y ago
I was literally thinking of the same similarities. Barbour's exposition of the principle of least action as being time is interesting. There's a section in The Janus Point where he goes into detail about the fact that there are parts of the cosmos that (due to cosmic inflation) are farther apart in terms of light-years than the universe is old, and growing in separation faster than c, meaning that they are forever causally separated. There will never be future changes in state from one that result in effects in the other. In a way, this also relates to computation, maybe akin to some kind of undecidability.
Another thing that came to mind when reading the part about how "black holes have too high a density of events inside of them to do any more computation" is Chaitin's incompleteness theorem: if I understand it correctly, that basically says that for any formal axiomatic system there is a constant c beyond which it's impossible to prove in the formal system that the Kolmogorov complexity of a string is greater than c. I get the same kind of vibe with that and the thought of the ruliad not being able to progressively simulate further states in a black hole.
- ziofill 2y agoActually, the parts of the universe receding from us faster than the speed of light can still be causally connected to us. It’s a known “paradox” that has the following analogy: an ant walks on an elastic band toward us at speed c, and we stretch the band away from us by pulling on the far end at a speed s > c. Initially the ant despite walking in our direction gets farther, but eventually it does reach us (in exponential time). The same is true for light coming from objects that were receding from us at a speed greater than c when they emitted it. See https://en.m.wikipedia.org/wiki/Ant_on_a_rubber_rope https://en.m.wikipedia.org/wiki/Ant_on_a_rubber_rope
- adastra22 2y agoThey will never reach us because the rate of expansion is accelerating.
- ziofill 2y agohttps://arxiv.org/abs/astro-ph/0310808 https://arxiv.org/abs/astro-ph/0310808
- adastra22 2y agoThat article doesn't back up your claim.
- ziofill 2y agoYes it does, look at the caption of Fig. 1: "Photons we receive that were emitted by objects beyond the Hubble sphere were initially receding from us (outward sloping lightcone at t <∼ 5 Gyr). Only when they passed from the region of superluminal recession vrec > c (gray crosshatching) to the region of subluminal recession (no shading) can the photons approach us". I can’t reply to your last reply. I agree, in fact I said those regions can be still causally connected to us, not that they are.
- adastra22 2y agoIt shows that SOME “superluminal” photons can reach us, not that ALL can. With accelerating expansion, eventually all galaxies fall out of that interval and become unreachable.
- nyrikki 2y agoThose photons aren't superluminal, the are in our past light cone, they were headed out way before the emitter was beyond the horizon. It gets complicated because the concept of 'now' is a local property and because those objects aren't moving away ftl, space is expanding.
- csomar 2y ago> There will never be future changes in state from one that result in effects in the other. You are assuming that the Principle of locality is true and proven. This is far from being the case from my understanding.
- adrianN 2y agoYou can’t really prove things in physics, but to my knowledge we don’t have observations that contradict locality.
- pizza 2y agoI've been thinking about this comment a bit. What do you mean that it's far from being proven? Wouldn't this mean there is some evidence for something faster than c?
- psychoslave 2y ago>There's a section in The Janus Point where he goes into detail about the fact that there are parts of the cosmos that (due to cosmic inflation) are farther apart in terms of light-years than the universe is old, and growing in separation faster than c, meaning that they are forever causally separated. There will never be future changes in state from one that result in effects in the other. In a way, this also relates to computation, maybe akin to some kind of undecidability. Ho, I love this hint. However even taking for granted that no faster than light travel is indeed an absolute rule of the universe, that doesn't exclude wormhole, or entangled particles. https://scitechdaily.com/faster-than-the-speed-of-light-information-transfer-through-spooky-action-at-a-distance-at-the-large-hadron-collider/ https://scitechdaily.com/faster-than-the-speed-of-light-info...
- nyrikki 2y agoIt would be nice if this was a problem with decidablity, but often it is a problem with indeterminacy that is way stronger than classic chaos. The speed of causality or I information is the limit that is the speed of light. Even in the case of entanglement, useful information is not ftl, If I write true on one piece of paper and false on another and randomly seed them to Sue and Bob, Sue instantly knows what Bob has as soon as she opens hers. While we teach QM similar to how it was discovered, there are less mystical interpretations that are still valid. Viewing wave function collapse as updating priors vs observer effects works but is pretty boring. While wormholes are a prediction of the theory, we don't know if the map matches the territory yet. But it is a reason to look for them. But if we do find them it is likely that no useful information will survive the transit through them. Kerr's rebuke of Hawkings assumption that black hole singularities are anything more than a guess from a very narrow interpretation of probably unrealistic, non rotating, non charged black holes is probably a useful read. The map simply isn't the territory, but that doesn't mean we shouldn't see how good that map is or look for a better one.
- nyrikki 2y agoKerr's paper that was referenced above. https://arxiv.org/abs/2312.00841 https://arxiv.org/abs/2312.00841