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It’s interesting that you class dark energy (the thing accelerating universal expansion) as, “We don’t know,” but don’t put gravity into that same category. The
by aardvark179 5y ago
It’s interesting that you class dark energy (the thing accelerating universal expansion) as, “We don’t know,” but don’t put gravity into that same category. They are both aspects of general relativity that we have failed to integrate with our other most successful fundamental theories, but if you asked an average person on the street I’m sure they’d put them in very different categories of understanding, as you did.
- Ma8ee 5y agoThe thing with gravity is that it is kind of easy to detect, even for a layperson, while dark energy and dark matter haven't been detected at all, by anyone, but only used as mathematical devices to make indirect measurements of large scale structures align with our models. So, it isn't only the "average man on the street" that thinks there are good reasons to put them in very different categories of understanding.
- mnw21cam 5y agoRelevant xkcd: https://xkcd.com/1489/ https://xkcd.com/1489/ The mouseover-text is the important bit: "Of these four forces, there's one we don't really understand." "Is it the weak force or the strong--" "It's gravity." That's even though it's the one with the simplest equations.
- Ma8ee 5y agoIs that an attempt to appeal to authority?
- kergonath 5y agoWorse than that: an appeal to the reader’s sense of humour.
- tsimionescu 5y ago> That's even though [gravity]'s the one with the simplest equations. Aren't the equations for gravity non-linear, while the other 3 are linear?
- whatshisface 5y agoThey're linear to the first-order, but everything is linear to first order by the definition of first order.
- whatshisface 5y agoCuriously... In the way dark matter has never been detected (no particle has been found), gravity has never been detected, and in the way gravity has been detected (through its influence on the trajectories of detectable matter), dark matter has been as well.
- vkazanov 5y agoWell, scientists would argue that general relativity (I.e. gravity the way we understand it now) does predict a lot of things really well. Now, the problem is that its predictions fall apart at quantum scale and cosmological scale. Dark thingies are just a way to make the equations work at cosmological scale. There's always modified gravity, which takes an alternative approach by changing the equations. That's how they taught me 15 years ago, so give or take:-)
- Ma8ee 5y agoIt’s a rather novel and very strange to say that something hasn’t been detected because you haven’t found a particle responsible for it, even though our whole existence and all our everyday experiences are grounded in it. Gravity is the effect. It’s there. Whether you explain it with force carrying particles or the geometry of space time won’t change it. Dark matter is one hypothetical explanation of an effect (or rather several). It’s possible to find another explanation for the same phenomena without changing the phenomena. In other words, gravity and dark matter have very different ontological status.
- whatshisface 5y ago>In other words, gravity and dark matter have very different ontological status. I get what you're saying, but you can make them the same again by transposing Dark Matter to Dark Matitation, by analogy to Gravitons->Gravitation.
- Ma8ee 5y agoNo, they are still not the same. If I understand you correctly, you are saying that Dark Matter would correspond to Gravitons. But that would just prove my point, because Gravitons is just a hypothetical explanation of gravity, in the same way as Dark matter is a hypothetical explanation of, e.g., the rotation profiles of galaxies. (And here we have so far left out that the only reason Dark matter makes sense is because we are trying to not have to modify our current understanding of gravity.)