[Please read the OP before voting. Special voting rules apply.]
Causal connections should not be part of our most fundamental model of the Universe. Everything that is useful about causal narratives is a consequence of the Second Law of Thermodynamics, which is irrelevant when we’re talking about microscopic interactions. Extrapolating our macroscopic fascination with causation into the microscopic realm has actually impeded the exploration of promising possibilities in fundamental physics.
I upvoted it because of the last sentence. Physicists are well aware that the differential equations (as opposed to the boundary conditions) of our universe are most likely CPT-invariant.
Yes, they are aware of this, but there are many examples of physicists failing to grasp the full significance of this fact. There is a difference between physicists acknowledging the CPT-invariance of fundamental laws, and fully embracing the philosophical consequences of this invariance. Huw Price’s Time’s Arrow and Archimedes’ Point documents a number of cases of physicists failing to do the latter.
For further examples, see the mess of a priori causality conditions and chronology protection conjectures in GR, largely motivated by a desire to avoid “causal paradoxes”. Tachyons are declared unphysical for similar reasons. So-called retrocausal interpretations of quantum mechanics, a very promising research topic IMO, are largely unexplored. Advanced (as opposed to retarded) solutions to differential equations are ruled unphysical. I could go on.
There is still a big unwritten assumption in theoretical physics that proper scientific explanations must account for things that happen now in terms of things that happened earlier. I can’t think of any reason for this bias beyond an attachment to causal narratives.
see the mess of a priori causality conditions and chronology protection conjectures in GR
Classical GR actually rules out changing the past (while allowing CTCs), despite the common misconceptions about it. The Novikov’s self-consistency principle was self-admittedly a way to say “there is no new physics other than GR”. Hawking’s famous chronology protection paper mainly showed that QFT cannot be done in the standard way on a wormhole background.
Tachyons are declared unphysical for similar reasons.
They are generally “declared unphysical” because the time-travel aspects cannot be analyzed self-consistently. Plus there is little evidence for it. However, non-propagating tachyon fields are not incompatible with GR. For example, a 2+1D slice of a 3+1D Schwarzschild black hole contains induced FTL matter fields, Kaluza-Klein style. PM me if you want more details.
So-called retrocausal interpretations of quantum mechanics
I can’t imagine how an interpretation can be a promising research topic.
There is still a big unwritten assumption in theoretical physics that proper scientific explanations must account for things that happen now in terms of things that happened earlier. I can’t think of any reason for this bias beyond an attachment to causal narratives.
I think this is overstating it. As long as a model is capable of predicting future observations based on the current ones, it is worth considering. If not, then it’s no longer a natural science, but at best math.
[Please read the OP before voting. Special voting rules apply.]
Causal connections should not be part of our most fundamental model of the Universe. Everything that is useful about causal narratives is a consequence of the Second Law of Thermodynamics, which is irrelevant when we’re talking about microscopic interactions. Extrapolating our macroscopic fascination with causation into the microscopic realm has actually impeded the exploration of promising possibilities in fundamental physics.
That would explain why it took so long for someone to discover timeless physics.
That sentence has the same air of paradox about it as “Many solipsists believe …”. (Perhaps deliberately?)
I confess I’m surprised by all the upvotes this one is getting. I thought it was quite a mainstream view.
I upvoted it because of the last sentence. Physicists are well aware that the differential equations (as opposed to the boundary conditions) of our universe are most likely CPT-invariant.
Yes, they are aware of this, but there are many examples of physicists failing to grasp the full significance of this fact. There is a difference between physicists acknowledging the CPT-invariance of fundamental laws, and fully embracing the philosophical consequences of this invariance. Huw Price’s Time’s Arrow and Archimedes’ Point documents a number of cases of physicists failing to do the latter.
For further examples, see the mess of a priori causality conditions and chronology protection conjectures in GR, largely motivated by a desire to avoid “causal paradoxes”. Tachyons are declared unphysical for similar reasons. So-called retrocausal interpretations of quantum mechanics, a very promising research topic IMO, are largely unexplored. Advanced (as opposed to retarded) solutions to differential equations are ruled unphysical. I could go on.
There is still a big unwritten assumption in theoretical physics that proper scientific explanations must account for things that happen now in terms of things that happened earlier. I can’t think of any reason for this bias beyond an attachment to causal narratives.
Classical GR actually rules out changing the past (while allowing CTCs), despite the common misconceptions about it. The Novikov’s self-consistency principle was self-admittedly a way to say “there is no new physics other than GR”. Hawking’s famous chronology protection paper mainly showed that QFT cannot be done in the standard way on a wormhole background.
They are generally “declared unphysical” because the time-travel aspects cannot be analyzed self-consistently. Plus there is little evidence for it. However, non-propagating tachyon fields are not incompatible with GR. For example, a 2+1D slice of a 3+1D Schwarzschild black hole contains induced FTL matter fields, Kaluza-Klein style. PM me if you want more details.
I can’t imagine how an interpretation can be a promising research topic.
I think this is overstating it. As long as a model is capable of predicting future observations based on the current ones, it is worth considering. If not, then it’s no longer a natural science, but at best math.
Oh, that’s a good point. I wonder whether pragmatist really meant to make such a strong statement there.