6 ms·

Maybe we don’t need a new model, but rather just accepting that the universe can be two seemingly opposite things at the same time Like the particle/wave duali

by nico 2y ago

Maybe we don’t need a new model, but rather just accepting that the universe can be two seemingly opposite things at the same time Like the particle/wave duality Maybe the whole universe is both quantum and not, at the same time. And we just perceive it differently at different scales. Like with a stroboscopic light, we might perceive things differently depending on how we are sampling (and not necessarily because the thing is different)

nathan_compton 2y ago
Nice idea, but there are intermediate scales and sampling methods and the universe has to have rules that determine how things happen at those scales.
- NoMoreNicksLeft 2y ago
  > and the universe has to have rules that Has anyone bothered to tell the universe this?
  - MengerSponge 2y ago
    I won't have any Last Thursdayists under my roof.
tsimionescu 2y ago
The wave/particle duality has long-since been accepted, as have other dualities (e.g. the event horizon of a black hole is both a completely normal portion of spacetime, and a boundary region that emits Hawking radiation, depending on your trajectory), where it is impossible to make an experiment that could see both at the same time. But QM can't be reconciled with GR in the same way. One day we'll have precise enough instruments to measure the gravitational interactions of large particles. One day we'll have large enough particle accelerators to be able to measure quantum properties of huge molecules whose gravitational properties we already know. When those days come, we'll need a unified theory of how quantum fields cause gravitational effects. And even if it turns out there is some fundamental limit of some type of measurement that does cause a QM/GR duality to exist, a theory that includes that specific limit would itself be a new, unified theory, that supersedes both QM/QFT and GR.
- nico 2y ago
  > But QM can't be reconciled with GR in the same way Would you care to explain? Why are the models so fundamentally incongruent? What exactly is the issue?
  - tsimionescu 2y ago
    I'm not a physicist, just a layman interested in this topic. So, if you're looking for very rigorous explanations, I can't help. That said, my understanding is this: if you try to calculate the trajectory of small particles using the equations of GR, and then compare that to measurements, you'll find that GR is dead wrong. Conversely, if you try to calculate the motion of stellar objects in strong gravitational fields using the equations of QM or QFT, you'll again get results that don't match observations at all. Further, for more complex mathematical reasons that I can't personally follow, if you just try to introduce the GR space-time deformation terms into QM equations, you can't compute anything because the equations diverge.
  - hifromwork 2y ago
    (Also not a physicist). GR works and has been tested experimentally on a large scale, but it doesn't always work on a small scale. QM works, has been tested experimentally on a small scale, but it doesn't always work on a large scale. They just give different predictions in some very small or very large cases. Obviously they can't both be right: if one theory predicts A and the other theory predicts B then we can just do the experiment and one of them will turn out to be wrong. Unfortunately, they only differ in extreme circumstances that are hard to recreate, and we were not able to perform an experiment that will tell us which is right (or how to tweak them to make them compatible with each other). Fun fact: There is a thing called a cosmological constant problem. It's the disagreement between the observed values of the cosmological constant (using GR) and a theoretical value suggested by QM. The observed value is... 10**120 times smaller than QM predicts it should be [1]. Now this is what I call a fundamental incongruence :). [1] This is also called "probably the worst theoretical prediction in the history of physics".
  - nyssos 2y ago
    QFTs are effective field theories: they describe interactions at a particular energy scale, smoothing over whatever unknown physics is going on at lower (or sometimes higher) length scales. This makes the strengths of interactions scale-dependent. So in QED, for instance, the fine structure "constant" is actually a few percent larger at the GeV scale than it is at zero energy. Fortunately for us, we only need to measure the fine-structure constant at finitely many energies to calculate its value at any energy scale we like. But this is just because QED happens to be well-behaved. When we try to apply the same techniques to the gravitational constant, we end up with infinitely many free parameters for reasons which are too technical to explain here. Any intro QFT textbook will probably have a rough heuristic argument (I used Srednicki), but we don't actually know with certainty that there's no clever way to get all those higher order terms to cancel - we just haven't found one and have no reason to expect one.
petsfed 2y ago
>And we just perceive it differently at different scales. Like with a stroboscopic light, we might perceive things differently depending on how we are sampling That's actually exactly what's going on with wave/particle duality. Everything's a wave, all the time, but in certain regimes, wave behavior very closely approximates particle behavior. The realization that particle behavior is therefore just a subset of wave behavior is part of the motivation for looking for an omnibus theory that accounts for everything. Unification is not unprecedented, consider e.g. the unification of the weak nuclear force and electromagnetic forces into the electroweak force.
- nico 2y ago
  Where’s the incongruence? At a macro scale, anything that happens in time can be considered as a sort of wave that we perceive as an object because of the way we are sampling it Even basic things, like when you measure your own weight, will vary throughout the day/time, but instead of considering them a wave, we usually just “collapse it” into some sort of average of observations Conceptually at least, both models seem to represent the same How are they not compatible? Is it a math issue?
  - tahoeskibum 2y ago
    The main incompatibility is that QM predicts that all fields have a zero point energy associated with each mode. However, GR predicts zero point energy will cause spacetime to curve. However there are infinite modes in QM, so now using this in GR leads to all spacetime instantly collapsing. However we exist so this collapse hasn't happened. The solution is the elusive Quantum Gravity, something that physicists from Einstein, Feynman haven't been able to solve.
    - nico 2y ago
      Thank you for the explanation What does it mean for “all spacetime instantly collapsing”? It would be amazing to see a video of a simulation of that
barfbagginus 2y ago
I propose the sharticle. Whereas particles and waves have energy and phase, the sharticle is always just in different states of shitting its pants. This makes it much more relatable to a human, who is already a type of sharticle.

by nico 2y ago

nathan_compton 2y ago

Nice idea, but there are intermediate scales and sampling methods and the universe has to have rules that determine how things happen at those scales.

NoMoreNicksLeft 2y ago
> and the universe has to have rules that Has anyone bothered to tell the universe this?
- MengerSponge 2y ago
  I won't have any Last Thursdayists under my roof.

tsimionescu 2y ago

The wave/particle duality has long-since been accepted, as have other dualities (e.g. the event horizon of a black hole is both a completely normal portion of spacetime, and a boundary region that emits Hawking radiation, depending on your trajectory), where it is impossible to make an experiment that could see both at the same time. But QM can't be reconciled with GR in the same way. One day we'll have precise enough instruments to measure the gravitational interactions of large particles. One day we'll have large enough particle accelerators to be able to measure quantum properties of huge molecules whose gravitational properties we already know. When those days come, we'll need a unified theory of how quantum fields cause gravitational effects. And even if it turns out there is some fundamental limit of some type of measurement that does cause a QM/GR duality to exist, a theory that includes that specific limit would itself be a new, unified theory, that supersedes both QM/QFT and GR.

nico 2y ago
> But QM can't be reconciled with GR in the same way Would you care to explain? Why are the models so fundamentally incongruent? What exactly is the issue?
- tsimionescu 2y ago
  I'm not a physicist, just a layman interested in this topic. So, if you're looking for very rigorous explanations, I can't help. That said, my understanding is this: if you try to calculate the trajectory of small particles using the equations of GR, and then compare that to measurements, you'll find that GR is dead wrong. Conversely, if you try to calculate the motion of stellar objects in strong gravitational fields using the equations of QM or QFT, you'll again get results that don't match observations at all. Further, for more complex mathematical reasons that I can't personally follow, if you just try to introduce the GR space-time deformation terms into QM equations, you can't compute anything because the equations diverge.
- hifromwork 2y ago
  (Also not a physicist). GR works and has been tested experimentally on a large scale, but it doesn't always work on a small scale. QM works, has been tested experimentally on a small scale, but it doesn't always work on a large scale. They just give different predictions in some very small or very large cases. Obviously they can't both be right: if one theory predicts A and the other theory predicts B then we can just do the experiment and one of them will turn out to be wrong. Unfortunately, they only differ in extreme circumstances that are hard to recreate, and we were not able to perform an experiment that will tell us which is right (or how to tweak them to make them compatible with each other). Fun fact: There is a thing called a cosmological constant problem. It's the disagreement between the observed values of the cosmological constant (using GR) and a theoretical value suggested by QM. The observed value is... 10**120 times smaller than QM predicts it should be [1]. Now this is what I call a fundamental incongruence :). [1] This is also called "probably the worst theoretical prediction in the history of physics".
- nyssos 2y ago
  QFTs are effective field theories: they describe interactions at a particular energy scale, smoothing over whatever unknown physics is going on at lower (or sometimes higher) length scales. This makes the strengths of interactions scale-dependent. So in QED, for instance, the fine structure "constant" is actually a few percent larger at the GeV scale than it is at zero energy. Fortunately for us, we only need to measure the fine-structure constant at finitely many energies to calculate its value at any energy scale we like. But this is just because QED happens to be well-behaved. When we try to apply the same techniques to the gravitational constant, we end up with infinitely many free parameters for reasons which are too technical to explain here. Any intro QFT textbook will probably have a rough heuristic argument (I used Srednicki), but we don't actually know with certainty that there's no clever way to get all those higher order terms to cancel - we just haven't found one and have no reason to expect one.

petsfed 2y ago

>And we just perceive it differently at different scales. Like with a stroboscopic light, we might perceive things differently depending on how we are sampling That's actually exactly what's going on with wave/particle duality. Everything's a wave, all the time, but in certain regimes, wave behavior very closely approximates particle behavior. The realization that particle behavior is therefore just a subset of wave behavior is part of the motivation for looking for an omnibus theory that accounts for everything. Unification is not unprecedented, consider e.g. the unification of the weak nuclear force and electromagnetic forces into the electroweak force.

nico 2y ago
Where’s the incongruence? At a macro scale, anything that happens in time can be considered as a sort of wave that we perceive as an object because of the way we are sampling it Even basic things, like when you measure your own weight, will vary throughout the day/time, but instead of considering them a wave, we usually just “collapse it” into some sort of average of observations Conceptually at least, both models seem to represent the same How are they not compatible? Is it a math issue?
- tahoeskibum 2y ago
  The main incompatibility is that QM predicts that all fields have a zero point energy associated with each mode. However, GR predicts zero point energy will cause spacetime to curve. However there are infinite modes in QM, so now using this in GR leads to all spacetime instantly collapsing. However we exist so this collapse hasn't happened. The solution is the elusive Quantum Gravity, something that physicists from Einstein, Feynman haven't been able to solve.
  - nico 2y ago
    Thank you for the explanation What does it mean for “all spacetime instantly collapsing”? It would be amazing to see a video of a simulation of that

barfbagginus 2y ago

I propose the sharticle. Whereas particles and waves have energy and phase, the sharticle is always just in different states of shitting its pants. This makes it much more relatable to a human, who is already a type of sharticle.