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100 Years After Einstein's Relativity, We're Still Just Figuring Gravity Out
- kyberias 11y agoIronically the tattoo in the image is the Newton's equation.
- dogma1138 11y agoWhich still is used and works even on cosmological scales. Relativity is only really useful in certain scenarios, people still calculate the motions of stars and galaxies with Newtonian physics:)
- brianberns 11y agoYes, but Newton's equation isn't relevant to the issues discussed in the article.
- kyberias 11y agoI'm sure everyone knows that here. :)
- genug 11y agoIt's a perfectly fine limiting case of G + Λg = 8πT. A minor point: it's "the Newton equation" or "Newton's equation", but not "the Newton's equation" (in the same way that one could write "the Eisenhower presidency" or "Eisenhower's presidency", but not "the Eisenhower's presidency").
- vardump 11y agoDisclaimer: I am not a physicist. Maybe gravity will turn out to be just a computational artefact. The more energy and states in a volume, the "slower" progression of the [local] system. An effect like this could appear as curved space at energy concentrations. Perhaps GR could be derived from something like this?
- danbruc 11y agoIdeas like that are often mentioned here when related topics come up but they are almost surly totally wrong. Computing means doing something in several steps and that is - as far as we can tell - absolutely not what the universe is doing. Even if the universe did something like that it would just mean that there is another layer below evolving in a more fundamental way. Many people seem pretty confused when physicist talk about things like the black hole information paradox. We think that all physical processes are reversible which means that distinct physical states will always remain distinct. If state A and state B could or would evolve into the same state C this assumption would no longer hold because you could no longer tell whether you arrived at state C from state A or B. The laws of physics would not be time reversible. And this is the sense in which physicist talk about information, the description of the state space. If you throw something into a black hole the only things that remain visible are things like the mass, the charge or the (angular) momentum but you just lost all the details about the thing you threw into the black hole which is a problem for our understanding of physics.
- Filligree 11y ago> And this is the sense in which physicist talk about information, the description of the state space. If you throw something into a black hole the only things that remain visible are things like the mass, the charge or the (angular) momentum but you just lost all the details about the thing you threw into the black hole which is a problem for our understanding of physics. Why is that a problem? The information could still exist, it'd just be inaccessible... This seems no different to me than a spaceship going beyond the Hubble horizon.
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- timeu 11y agoPBS Spacetime has some really nice videos about Gravity (Newtonian vs GR) https://www.youtube.com/watch?v=NblR01hHK6U https://www.youtube.com/watch?v=NblR01hHK6U
- sneezeplease 11y agoGravity is a lie and doesnt exist. The theory of relativity is well debunked at this point.
- bwooceli 11y agoHonest question. If the concept of dark matter flows from our current understanding of gravity, and gravity is so admittedly poorly understood, how confident are we that dark matter is "a thing"? I know an intuitive sensibility is not the best foundation for an understanding of The Universe, but every time I read about dark matter, I get a very "Aether"-ish vibe. I just imagine comments section in the 2070 version of HN getting a good natured laugh about dark matter.
- genug 11y agoSystems like the bullet cluster (https://en.wikipedia.org/wiki/Bullet_Cluster https://en.wikipedia.org/wiki/Bullet_Cluster) are taken as evidence that most of the matter in large-scale, gravitationally bound astrophysical systems does not behave like luminous matter.
- ISL 11y agoBoth dark matter and dark energy are descriptive placeholders for phenomena we partially understand. With them, we can simultaneously explain lots of observed effects. But, as in the time of the aether, we know we don't have the whole story.
- chunky1994 11y ago> gravity is so admittedly poorly understood Gravity as a force/phenomena in space on its own is actually very well understood. In fact it's possibly one of the most well understood theories we have in physics because of general relativity. However, at a particle scale we lack the understanding of how gravity would work. Dark matter is the collective name for whatever "stuff" exists in the universe that we predict it should have, however because it is noninteractive in any way other than exerting a gravitational pull (it accounts for a lot of astrophysical observations that otherwise are bewildering given what we see in the universe). We know it should exist, we don't know what it is and can barely understand its current properties. So indeed, it is quite possible that it might be Aether-ish if we end up finding something else that explains our current observations or a drastic overhaul of how gravity works at large scales (the latter being very unlikely because of how well GR has stood up to experimentation so far).
- AnimalMuppet 11y agoWarning: speculation follows. If we understand correctly, the universe is about 13.7 billion years old. I recall reading once that there is enough mass (matter plus dark matter) that the Swarzchild Radius of that much mass is approximately 13.7 billion light-years. What if we're inside a black hole? How would that affect how we interpret what we see at large distances? (For example, does that explain the Hubble redshift? Does it explain dark energy?) And, if it's true, then what is a black hole? Can you have a black hole inside the Swarzchild radius of another black hole?