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I wonder if this can lead to revision of “vacuum energy” theories. The idea that empty space simply has a uniform, non-zero energy level is a disappointing and
by crmd 3y ago
I wonder if this can lead to revision of “vacuum energy” theories.
The idea that empty space simply has a uniform, non-zero energy level is a disappointing and kind of anti-climatic explanation for one of the greatest mysteries of physics and hints that our best models of the universe have huge gaps.
- teaearlgraycold 3y agoThat seems very counter-intuitive. Energy usually comes from a difference between two things. How could there be uniform energy everywhere? It's paradoxical.
- snarkconjecture 3y agoIt makes more sense if you've learned general relativity.
- hinkley 3y agoIf mass has energy, and mass creates space, who is to say that the energy isn’t smeared out across the universe? We’ve detected gravity “waves” now.
- AprilArcus 3y agoWell that's just what the Higgs field is, a scalar field with a nonzero vacuum expectation value. So the existence of a field of this kind isn't just possible in principle, it's been experimentally verified.
- snarkconjecture 3y agoYup. On which note, the Higgs' symmetry breaking should really have changed the vacuum energy density by something orders of magnitude larger than the density of dark energy...
- layer8 3y agoIt might not be everywhere, just by happenstance in the region that contains our observable universe.
- simonh 3y agoLet’s sincerely hope there isn’t a region with lower energy anywhere near us. If the vacuum energy here collapsed to a lower energy level you can kiss all current structured matter goodbye.
- hgtresd 3y ago> Energy usually comes from a difference between two things. Exactly, and letting either of those two things to be 0 is effectively saying you’re measuring between one thing, which is a contradiction.
- pigpang 3y agoUniverse is infinite. It means, that we can zoom up infinitely AND we can zoom down infinitely, which means that space always filled with something, and this something have a temperature.
- marginalia_nu 3y ago> Universe is infinite. It means, that we can zoom up infinitely AND we can zoom down infinitely, which means that space always filled with something, and this something have a temperature. I'm not sure this follows. The set of positive integers is infinite. It means that there's always a larger integer, but it doesn't mean there's always a smaller one, or an infinite number of integers between 1 and 10.
- naveen99 3y agoReplace integers with rationals or reals.
- marginalia_nu 3y agoHaving four legs doesn't follow from something being an animal just because there are examples of animals with four legs. A chicken is also an animal. Having four legs is accidental to being an animal, just as there being an infinite number of elements between any two elements in a set is accidental to its cardinality being infinite.
- naveen99 3y agoChickens have wings at the end of their arms.
- pigpang 3y agoEven in this case, there is infinitely small chance that we are sitting so close to the beginning of everything.
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- hinkley 3y agoThere’s one theory that the Big Bang happened when that energy state changed. That change affected how all matter interacts with each other and a completely new configuration of the universe was born at the new speed of light. And it could change again. We’d all be dead before we knew what was happening.
- snarkconjecture 3y agoWhy would a disappointingly simple explanation be a hint that there are gaps in our models? Or am I parsing that part wrong? I disagree that it's really that simple an explanation, though. Our best theoretical prediction for dark energy is that it should be denser by dozens of orders of magnitude. It's not remotely clear why the actual value seems to be so small, especially since it's not exactly zero.
- layer8 3y agoI see no good reason why this was downvoted.
- naasking 3y ago> It's not remotely clear why the actual value seems to be so small, especially since it's not exactly zero. It is very clear actually: one or both of the models producing the conflicting result are wrong. Smart money's on both, because we have good other reasons to think each of them is wrong.
- hgtresd 3y agoI think vacuum energy is best described as a product of the mathematical model used to describe reality with an accuracy of 10 decimal places. From that perspective it seems a very reasonable deduction. Wave functions can be seen as the sum of polynomial terms. So a wave function of: x^3+3x^2+4x could be expressed as its coefficients [1,3,4]. Now if any of those coefficients are allowed to be zero, then you’d have, say, [0,3,4] for your polynomial which simplifies to an identical polynomial [3,4]. This just reduced the dimension of the problem by 1, but a wave function in n dimensions is fundamentally different than one with n-1 or n+1. If you could reduce the dimension of a problem by zeroing a coefficient and still get accurate calculations then then “curse of dimensionality” would be moot because you could just keep reducing the dimension until the problem was tractable and then reverse the process to build back up to the original problem. Unfortunately, the pigeon hole problem creeps up when the additional states of the higher dimension lack a direct analogue to its lower dimension. Think of a binary tree. At each element draw two new elements branching from it on a line below. Allowing any leaf to be 0 effectively removes it and all of its parents and children from the model. So in order to retain the full tree all values at each leaf must be greater than 0.
- Retric 3y ago> mathematical model used to describe reality Except reality has zero requirements to conform to mathematical models even if ours sometimes work to 10 decimal places there’s other cases they don’t work at all.
- mensetmanusman 3y agoIt's clear that reality conforms to some operating model, ours may get somewhat close, but it's getting close to something that is real.
- Retric 3y agoSure, but trying to apply models from areas they work to areas they don’t is a mistake. As soon as you step outside the area a model provides accurate answers you need to stop using it because some unaccounted for factor is now significant. It’s a depressingly common mistake. Read up on what people used to say about breaking the sound barrier despite known examples of bullies etc doing so. People literally knew the model was wrong in that region and yet they still used it to make predictions.
- XorNot 3y agoVacuum energy is the product of the uncertainty principle though - the Casimir force is the result of the fact that in any given volume of free space there's a certain number of standing electromagnetic waves which could fit, and thanks to quantum mechanics these are in fact quite real. Put a pair of parallel conducting plates between a given bounded volume though, and interesting thing happens: while shorter, higher energy standing waves can still fit between them, the longer, lower energy ones cannot. As a result, there is now no longer an unbounded number of virtual photons between the inside plates and the outside ones, and this manifests as a very slight force on the plates because you now have a higher energy on the outside then on the inside. But it's a lossy process: the plates can only exclude longer, lower energy wavelengths, so there's a very finite upper bound on how much energy any given arrangement of this system can produce since as you move the plates closer together the remaining energy inside grows much faster then the energy outside (shorter virtual wavelengths). If you're wondering how this affects you: it's all around you. Vacuum energy - the Casimir force - is believed to account for most of the force known to be due to van der Waal's forces in chemistry - i.e. the basic force which sticks non-ionic, non-covalent things together. The difficulty of removing dust for example, is being driven by that. EDIT: "Dark Energy" - which is what's being discussed here, is very different.