Feb 21, 2025 08:35 PM
Quantum mechanics, white holes, and the relational universe
https://iai.tv/articles/quantum-mechanic..._auid=2020
INTRO: Once considered pure speculation, black holes are now a well-established scientific entity. In this IAI interview, Carlo Rovelli makes the case that white holes—though still theoretical—warrant serious attention. White holes are the hypothetical opposites of black holes; instead of pulling matter in, they expel it out and cannot be entered. Rovelli explains how quantum mechanics suggests that black holes could eventually transform into white holes through a process called quantum tunnelling, challenging our understanding of space, time, and gravity.
-EXCERPT- . . . CB: Throughout your work, you’re aware of the limits of scientific understanding when proposing theories like white holes and loop quantum gravity. Are these theories describing an ultimate reality that exists out there, or are they just models to help us understand the world? Are these two ideas connected, or is there a clear distinction?
CR: Neither actually. Reality exists independently of us, and things are out there, regardless of our thinking. However, our descriptions of reality are not independent of us. Science helps us create conceptual frameworks and mathematical tools to make sense of the world based on our experiences. These theories aren’t arbitrary—they reflect properties of reality that we can describe, but only within some approximation. We know all theories are incomplete; for instance, general relativity doesn’t include quantum mechanics. So, in that sense, our theories describe reality, but they’re not a perfect reflection of it. They show us how things look from our perspective, but reality itself, like a galaxy, is more than just our view of it. It’s a blend of describing what’s out there and developing our own understanding of it... (MORE - details)
Can time emerge from a timeless world?
https://iai.tv/articles/can-time-emerge-..._auid=2020
EXCERPTS: The concept of time is indispensable in modern physics, yet in our equations for quantum gravity it is shown to disappear. Some have accepted the fundamental timelessness of nature and others have sought a deeper theory in which a time is recoverable, but other physicists and philosophers of physics have attempted a different approach – to show that that time emerges from a timeless world. While some have critiqued this notion of emergence on metaphysical grounds, Eugene Chua argues that we should instead critique theories of emergent time on the merits of their physical arguments which, as Chua points out, aren’t as coherent as some of their proponents might think.
[...] Despite the demise of a global Now, concepts of time persist nonetheless in special and general relativity: for instance, we can find globally well-defined times (e.g. cosmic time) when spacetimes possess certain symmetries, and we can always find a Lorentz invariant proper time interval between any two points along time-like world-lines – the time read out by clocks moving along that line. Granted, these are not quite the universal, observer-independent, notions earlier thinkers like Aristotle or Newton had in mind. However, as Craig Callender points out in What Makes Time Special, there remains in general relativity “sharp and important distinctions between the timelike and spacelike directions of spacetime” which allows us to find some notions of time even in the relativistic setting.
In recent decades, however, the existence of time itself has come under attack, due in part to the aptly named “Problem of Time”. This problem arises in the context of a particular strategy for unifying our best theory of matter, quantum mechanics, and our best theory of spacetime, general relativity: the canonical approach to quantum gravity. In this approach, we obtain a fundamental equation very much reminiscent of a time-dependent Schrodinger’s equation (TDSE), called the Wheeler-DeWitt equation (WDE). It differs from the TDSE in at least one crucial way. While the usual TDSE tells us how wave-functions representing the quantum state of ordinary matter evolve over time, the WDE seems to tell us that the quantum state of the world – matter and gravity included – does not change at all over time. The world is utterly ‘frozen’ and unchanging – timeless.
[...] The middle way has attracted a lot of attention from philosophers and physicists because of its intriguing claim that time (and, often, spacetime) are emergent from fundamentally non-temporal ontology. If the middle way works out, it seems like we can have our layer cake and eat it, too: we can accept the Problem of Time but recover the time we know and love.
Schematically, the middle way proceeds in three steps. One, start with the fundamentally timeless ontology. Two, apply some set of formal tools – equations, approximations, idealizations, whatever we have in our mathematical toolbox – to the ontology. Three, obtain some formal product – some (sets of) solutions, some models, some parameters, and so on – that is to be interpreted temporally. I’ll briefly mention two stories for walking the middle way: semiclassical time and thermal time. Both begin from the fundamentally timeless ontology governed by the WDE, but take very different paths in trying to find time in a timeless world.
[...] Time is indispensable to standard physics, yet in quantum gravity our equations paint a strangely frozen world. The middle way promises reconciliation, but whether it can do so without sacrificing physical coherence is far from settled. Ultimately, whether time genuinely emerges or simply never was, the nature of this dimension of our world remains obscured for now, a most familiar stranger. Only time will tell if its secrets are revealed... (MORE - missing details)
https://iai.tv/articles/quantum-mechanic..._auid=2020
INTRO: Once considered pure speculation, black holes are now a well-established scientific entity. In this IAI interview, Carlo Rovelli makes the case that white holes—though still theoretical—warrant serious attention. White holes are the hypothetical opposites of black holes; instead of pulling matter in, they expel it out and cannot be entered. Rovelli explains how quantum mechanics suggests that black holes could eventually transform into white holes through a process called quantum tunnelling, challenging our understanding of space, time, and gravity.
-EXCERPT- . . . CB: Throughout your work, you’re aware of the limits of scientific understanding when proposing theories like white holes and loop quantum gravity. Are these theories describing an ultimate reality that exists out there, or are they just models to help us understand the world? Are these two ideas connected, or is there a clear distinction?
CR: Neither actually. Reality exists independently of us, and things are out there, regardless of our thinking. However, our descriptions of reality are not independent of us. Science helps us create conceptual frameworks and mathematical tools to make sense of the world based on our experiences. These theories aren’t arbitrary—they reflect properties of reality that we can describe, but only within some approximation. We know all theories are incomplete; for instance, general relativity doesn’t include quantum mechanics. So, in that sense, our theories describe reality, but they’re not a perfect reflection of it. They show us how things look from our perspective, but reality itself, like a galaxy, is more than just our view of it. It’s a blend of describing what’s out there and developing our own understanding of it... (MORE - details)
Can time emerge from a timeless world?
https://iai.tv/articles/can-time-emerge-..._auid=2020
EXCERPTS: The concept of time is indispensable in modern physics, yet in our equations for quantum gravity it is shown to disappear. Some have accepted the fundamental timelessness of nature and others have sought a deeper theory in which a time is recoverable, but other physicists and philosophers of physics have attempted a different approach – to show that that time emerges from a timeless world. While some have critiqued this notion of emergence on metaphysical grounds, Eugene Chua argues that we should instead critique theories of emergent time on the merits of their physical arguments which, as Chua points out, aren’t as coherent as some of their proponents might think.
[...] Despite the demise of a global Now, concepts of time persist nonetheless in special and general relativity: for instance, we can find globally well-defined times (e.g. cosmic time) when spacetimes possess certain symmetries, and we can always find a Lorentz invariant proper time interval between any two points along time-like world-lines – the time read out by clocks moving along that line. Granted, these are not quite the universal, observer-independent, notions earlier thinkers like Aristotle or Newton had in mind. However, as Craig Callender points out in What Makes Time Special, there remains in general relativity “sharp and important distinctions between the timelike and spacelike directions of spacetime” which allows us to find some notions of time even in the relativistic setting.
In recent decades, however, the existence of time itself has come under attack, due in part to the aptly named “Problem of Time”. This problem arises in the context of a particular strategy for unifying our best theory of matter, quantum mechanics, and our best theory of spacetime, general relativity: the canonical approach to quantum gravity. In this approach, we obtain a fundamental equation very much reminiscent of a time-dependent Schrodinger’s equation (TDSE), called the Wheeler-DeWitt equation (WDE). It differs from the TDSE in at least one crucial way. While the usual TDSE tells us how wave-functions representing the quantum state of ordinary matter evolve over time, the WDE seems to tell us that the quantum state of the world – matter and gravity included – does not change at all over time. The world is utterly ‘frozen’ and unchanging – timeless.
[...] The middle way has attracted a lot of attention from philosophers and physicists because of its intriguing claim that time (and, often, spacetime) are emergent from fundamentally non-temporal ontology. If the middle way works out, it seems like we can have our layer cake and eat it, too: we can accept the Problem of Time but recover the time we know and love.
Schematically, the middle way proceeds in three steps. One, start with the fundamentally timeless ontology. Two, apply some set of formal tools – equations, approximations, idealizations, whatever we have in our mathematical toolbox – to the ontology. Three, obtain some formal product – some (sets of) solutions, some models, some parameters, and so on – that is to be interpreted temporally. I’ll briefly mention two stories for walking the middle way: semiclassical time and thermal time. Both begin from the fundamentally timeless ontology governed by the WDE, but take very different paths in trying to find time in a timeless world.
[...] Time is indispensable to standard physics, yet in quantum gravity our equations paint a strangely frozen world. The middle way promises reconciliation, but whether it can do so without sacrificing physical coherence is far from settled. Ultimately, whether time genuinely emerges or simply never was, the nature of this dimension of our world remains obscured for now, a most familiar stranger. Only time will tell if its secrets are revealed... (MORE - missing details)