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The "shut up and calculate" attitude has done a lot of harm to physics research over the past decades. It is quite remarkable and more than a bit surprising tha

by uoaei 2y ago

The "shut up and calculate" attitude has done a lot of harm to physics research over the past decades. It is quite remarkable and more than a bit surprising that the primary tenet of general relativity -- that spacetime behaves differently where there is curvature vs where there is not -- was not sufficiently accounted for seemingly by any researchers this entire time. I am interested to see some retrospective metaanalysis on how many cosmological models have not suffered from this glaring omission. I suspect it's very few but I also think that it would be difficult to do this kind of modeling before we were able to do analysis in silico so there would be an obvious bias in the set of theories.

JumpCrisscross 2y ago
> The "shut up and calculate" attitude has done a lot of harm to physics research over the past decades This is a shut up and calculate paper. There is zero theoretical ground being broken. The meat is in the statistical analysis (which I concede is beyond me).
- uoaei 2y ago
  This paper is distinct in that it's cogent about the underlying cosmological principles. "Shut up and calculate" poisoned academic physics by eliding the necessity of thinking of systems as systems, and not merely as sets of equations to be manipulated.
ANewFormation 2y ago
This is also the biggest surprise for me, but I'd frame it as people largely just handwaving in the assumption of a (at scale) isotropic universe, even though that's highly questionable. I think the practical issue is that that assumption let a lot more work get done than would have been possible otherwise. Of course if it turns out the universe is not isotropic then most all of that work is worth less than nothing. So publish or perish strikes again?
- programjames 2y ago
  It is somewhat surprising, because one of the most famous papers in chaos theory, "The Applicability of the Third Integral of Motion" (Henon & Heiles), basically starts by saying a similar assumption isn't true, that stars aren't ergodically distributed in the axial/radial directions. If you have five equations of motion in a six-dimensional universe (3 space + 3 velocity coordinates), you can compute the future trajectory of each point. Two equations come from constant energy & angular momentum, and these constrain where in phase-space the trajectories can go. Another two equations are do not make any such constraints, which implies stars are at least ergodically distributed in a 2D phase-space. Since none of these equations constrain the axial/radial velocity, you would expect the dispersions to be equal for both directions. However, this turns out to not be the case. This means there must be a third isolating equation of motion out there, and the surprising thing Henon & Heiles find is it's chaotic! Sometimes it constrains points to 2D regions of phase-space (i.e. concentric circles of orbits), and other times it lets them move in a 3D region (i.e. chaotic trajectories filling the space).
sampo 2y ago
Also Pioneer Anomaly was solved, after dropping simple models treating the space probe as a simple or spherical particle, and accounting for the 3-dimensional shape of the probe. Because of the shape of the space probe, part of the thermal radiation emitted from its surfaces were hitting some other surfaces, and thus the probe did not emit radiation evenly into every direction. https://en.wikipedia.org/wiki/Pioneer_anomaly https://en.wikipedia.org/wiki/Pioneer_anomaly
caconym_ 2y ago
> It is quite remarkable and more than a bit surprising that the primary tenet of general relativity -- that spacetime behaves differently where there is curvature vs where there is not -- was not sufficiently accounted for seemingly by any researchers this entire time. This was also my first thought when I heard about this paper. It seems almost impossible that nobody in the entire contentious field of physical cosmology had considered whether our current consensus models account for the relativistic effects of the (known!) large scale structure of space. Following from that, my second thought was that maybe there is something more subtle about this analysis---maybe the question the researchers asked is less obvious than the headline makes it seem ("we forgot about relativity"). Obviously the subject matter is beyond me to answer that question myself, and I haven't found any good answers elsewhere.
- exe34 2y ago
  GR calculations are very hard, and it's easy to think the effects aren't relevant outside of extreme conditions. this reminds me of the (sadly not very well supported) paper about gravitomagnetism explaining the rotation curves without dark matter.
- justlikereddit 2y ago
  The way I see it people got stuck in a mindset of universal background time that is pretty much what earth clocks run at. With any serious relativity effects only being locally compartmentalized next to extreme cosmic phenomena. Adding dark matter to this mindset makes it even worse because it homogenizes everything even further towards a Universal Standard Timeframe when 80% of all mass is finely dispersed as a background fog. Put the Real back in Relativity. It's by far a more satisfying solution than magic mystery matter. My pet theory is that black holes are also vastly misunderstood because they're always seen from the Universal Standard Timeframe, if we probe a black hole and their local space from strongly relativistic timeframe they'll start to make more sense, but I'll leave that to the daydreams of the reader.
  - User23 2y ago
    GR says that you can pick any frame that you want. The Earth-centered, Earth-fixed coordinate system happens to be really convenient practically, for things like navigation satellites.

by uoaei 2y ago

JumpCrisscross 2y ago

> The "shut up and calculate" attitude has done a lot of harm to physics research over the past decades This is a shut up and calculate paper. There is zero theoretical ground being broken. The meat is in the statistical analysis (which I concede is beyond me).

uoaei 2y ago
This paper is distinct in that it's cogent about the underlying cosmological principles. "Shut up and calculate" poisoned academic physics by eliding the necessity of thinking of systems as systems, and not merely as sets of equations to be manipulated.

ANewFormation 2y ago

This is also the biggest surprise for me, but I'd frame it as people largely just handwaving in the assumption of a (at scale) isotropic universe, even though that's highly questionable. I think the practical issue is that that assumption let a lot more work get done than would have been possible otherwise. Of course if it turns out the universe is not isotropic then most all of that work is worth less than nothing. So publish or perish strikes again?

programjames 2y ago
It is somewhat surprising, because one of the most famous papers in chaos theory, "The Applicability of the Third Integral of Motion" (Henon & Heiles), basically starts by saying a similar assumption isn't true, that stars aren't ergodically distributed in the axial/radial directions. If you have five equations of motion in a six-dimensional universe (3 space + 3 velocity coordinates), you can compute the future trajectory of each point. Two equations come from constant energy & angular momentum, and these constrain where in phase-space the trajectories can go. Another two equations are do not make any such constraints, which implies stars are at least ergodically distributed in a 2D phase-space. Since none of these equations constrain the axial/radial velocity, you would expect the dispersions to be equal for both directions. However, this turns out to not be the case. This means there must be a third isolating equation of motion out there, and the surprising thing Henon & Heiles find is it's chaotic! Sometimes it constrains points to 2D regions of phase-space (i.e. concentric circles of orbits), and other times it lets them move in a 3D region (i.e. chaotic trajectories filling the space).

sampo 2y ago

Also Pioneer Anomaly was solved, after dropping simple models treating the space probe as a simple or spherical particle, and accounting for the 3-dimensional shape of the probe. Because of the shape of the space probe, part of the thermal radiation emitted from its surfaces were hitting some other surfaces, and thus the probe did not emit radiation evenly into every direction. https://en.wikipedia.org/wiki/Pioneer_anomaly https://en.wikipedia.org/wiki/Pioneer_anomaly

caconym_ 2y ago

> It is quite remarkable and more than a bit surprising that the primary tenet of general relativity -- that spacetime behaves differently where there is curvature vs where there is not -- was not sufficiently accounted for seemingly by any researchers this entire time. This was also my first thought when I heard about this paper. It seems almost impossible that nobody in the entire contentious field of physical cosmology had considered whether our current consensus models account for the relativistic effects of the (known!) large scale structure of space. Following from that, my second thought was that maybe there is something more subtle about this analysis---maybe the question the researchers asked is less obvious than the headline makes it seem ("we forgot about relativity"). Obviously the subject matter is beyond me to answer that question myself, and I haven't found any good answers elsewhere.

exe34 2y ago
GR calculations are very hard, and it's easy to think the effects aren't relevant outside of extreme conditions. this reminds me of the (sadly not very well supported) paper about gravitomagnetism explaining the rotation curves without dark matter.
justlikereddit 2y ago
The way I see it people got stuck in a mindset of universal background time that is pretty much what earth clocks run at. With any serious relativity effects only being locally compartmentalized next to extreme cosmic phenomena. Adding dark matter to this mindset makes it even worse because it homogenizes everything even further towards a Universal Standard Timeframe when 80% of all mass is finely dispersed as a background fog. Put the Real back in Relativity. It's by far a more satisfying solution than magic mystery matter. My pet theory is that black holes are also vastly misunderstood because they're always seen from the Universal Standard Timeframe, if we probe a black hole and their local space from strongly relativistic timeframe they'll start to make more sense, but I'll leave that to the daydreams of the reader.
- User23 2y ago
  GR says that you can pick any frame that you want. The Earth-centered, Earth-fixed coordinate system happens to be really convenient practically, for things like navigation satellites.