Paul P. Mealing

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Showing posts with label Quantum Mechanics. Show all posts
Showing posts with label Quantum Mechanics. Show all posts

Sunday 3 March 2024

Is randomness real or illusion?

 Let’s look at quantum mechanics (QM). I watched a YouTube video on Closer To Truth with Fred Alan Wolf, a theoretical physicist, whom I admit I’d never heard of. It’s worth watching the first 7 mins before he goes off on a speculative tangent that maybe dreams are a more fundamental level of reality, citing Australian Aboriginal ‘dreamtime’ mythology, of which I have some familiarity, though no scholarship.
 
In the first 7 mins he describes QM: its conceptual frustrations juxtaposed with its phenomenal successes. He gives a good synopsis, explaining how it describes a world we don’t actually experience, yet apparently underpins (my term, not his) the one we do. In particular, he explains:
 
There is a simple operation that takes you out of that space into (hits the table with his hand) this space. And that operation is simply multiplying what that stuff - that funny stuff – is, by itself (waves his hands in circles) in a time-reverse manner, called psi star psi (Ψ*Ψ) in the language of quantum physics.
 
What he’s describing is called the Born rule, which gives probabilities of finding that ‘stuff’ in the real world. By ‘real world’ I mean the one we are all familiar with and that he can hit his hand with. Ψ (pronounced sy) is of course the wave function in Schrodinger’s eponymous equation, and Schrodinger himself wrote a paper (in 1941) demonstrating that Born’s rule effectively multiplies the wave function by itself running backwards in time.
 
Now, some physicists argue that Ψ is just a convenient mathematical fiction and Carlo Rovelli went so far as to argue that it has led us astray (in one of his popular books). Personally, I think it describes the future, which explains why we never see it, or as soon as we try to, it disappears, and if we’re lucky, we get a particle or some other interaction, like a dot on a screen, all of which exist in our past. Note that everything we observe, including our own reflection in a mirror, exists in the past.
 
Wolf then goes on to speculate that the infinite possibilities we use for our calculations are perhaps the true reality. In his own words: What I’m interested in are the things we can’t see… And he makes an interesting point that most people don’t know: that if we don’t take into account the things we can’t see, ‘we get the wrong answers’.
 

And this is where it gets interesting, because he’s alluding to Feynman’s sum-over-histories methodology, which takes into account all the infinite paths that the particle (as wave function) can take. In fact, the more paths that are allowed for, the more accurate the calculation. Wolf doesn’t mention Feynman, but I’m sure that’s what he’s referring to.
 
Feynman’s key insight into QM was that it obeys the least-action principle, which is mathematically expressed as a Lagrangian. It’s the ‘least-action principle’ that determines where light goes through a change in medium (like glass), obeying Fermat’s law where it takes the path of ‘least time’. It also determines the path a ball follows if you throw it into the air by following the path of ‘maximum relativistic time’. I elaborate on this in another post.
 
There is something teleological about this principle, as if the ball, particle, light, ‘knows’ where it has to go. Freeman Dyson, who was a close collaborator with Feynman, argued that QM cannot describe the past, but only the future, and that only classical physics describes the past. So these infinitude of paths that are part of the calculation to determine the probability of where it will actually be ‘observed’ make more sense to me if they exist in the future. I don’t think we need a ‘dream state’ unless that’s a euphemism for the future.
 
Like Dyson, I don’t think we need consciousness to make a quantum phenomenon become real, but it does provide the reference point. In his own words:
 
We do not need a human observer to make quantum mechanics work. All we need is a point of reference, to separate past from future, to separate what has happened from what may happen, to separate facts from probabilities.
 
The thing about consciousness is that it exists in a ‘constant present’, as pointed out by Schrodinger himself (when he wasn’t talking about QM), so it logically correlates with 'a point of reference, to separate past from future', that Dyson refers to.
 
Schrodinger coined a term, ‘statistico-deterministic’, to describe quantum phenomena, because, at a statistical level, it can be very predictable, otherwise we wouldn’t be able to call it ‘successful’. He gives the example of radioactive decay (exploited in his eponymous cat thought experiment) whereby we can’t determine the decay of a single isotope, yet we can statistically determine the half-life of astronomical numbers of atoms very accurately, as everyone knows.
 
I contend that real randomness, that we all observe and are familiar with, is caused by chaos, but even this is a contentious idea. I like to give the example of tossing a coin, but a lot of physicists will tell you that tossing a coin is not random. In fact, I recently had a lengthy, but respectful, discourse with Mark John Fernee (physicist at Qld Uni) on Quora on this very topic. When I raised the specific issue of whether tossing a coin is ‘random’, he effectively argued that there are no random phenomena in physics. To quote him out of context:
 
Probability theory is built from statistical sampling. There is no assumed underlying physics.
 
The underlying physics can be deterministic, while a statistical distribution of events can indicate random behaviour. This is the assumption that is applied to every coin toss. Because this is just an assumption, you can cheat the system by using specific conditions that ensure deterministic outcomes.
 
What I am saying is that randomness is a statistical characterisation of outcomes that does not include any physical mechanism. As such, it is not a fundamental property of nature.
(Emphasis in original)
 
I get the impression from what I’ve read that mathematicians have a different take on chaos to physicists, because they point out that you need to calculate initial conditions to infinite decimal places to achieve a 100% predicted outcome. Physicist, Paul Davies, provided a worked example in his 1988 book, The Cosmic Blueprint. I quoted Davies to Fernee during our ‘written’ conversation:
 
It is actually possible to prove that the activity of the jumping particle is every bit as random as tossing a coin.
 
The ‘jumping particle’ Davies referred to was an algorithm using clock arithmetic, that when graphed produced chaotic results, and he demonstrated that it would take a calculation to infinity to get it ‘exactly right’. Fernee was dismissive of this and gave it as an example of a popular science book leading laypeople (like myself) astray, which I thought was a bit harsh, as Davies actually goes into the mathematics in some detail, and I possibly misled Fernee by quoting just one sentence.
 
Just to be clear, Fernee doesn’t disagree that chaotic phenomena are impossible to predict; just that they are fully deterministic and, in his words, only ‘indicate random behaviour’.
 
Sabine Hossenfelder, who argues very strongly for superdeterminism, has a video demonstrating how predicting chaotic phenomena (like the weather) has a horizon (my term, not hers) of predictability that can never be exceeded, even in principle (10 days in the case of the weather).
 
So Fernee and Hossenfelder distinguish between what we ‘cannot know’ and what physically transpires. But my point is that chaotic phenomena, if rerun, will always produce a different result – it’s built into the mathematics underlying the activity – and includes significant life-changing phenomena like evolutionary biology and the orbits of the planets, as well as weather and earthquakes. Even the creation of the moon is believed to be a consequence of a chaotic event, without which life on Earth would never have evolved.
 
Note that both QM and chaos have mathematical underpinnings, and whilst most see that as modelling or a very convenient method of making predictions, I see it as more fundamental. I contend that mathematics transcends the Universe, yet it’s also a code that allows us to plumb Nature’s deepest secrets and fathom the dynamics of the Universe on all scales.

Monday 23 October 2023

The mystery of reality

Many will say, ‘What mystery? Surely, reality just is.’ So, where to start? I’ll start with an essay by Raymond Tallis, who has a regular column in Philosophy Now called, Tallis in Wonderland – sometimes contentious, often provocative, always thought-expanding. His latest in Issue 157, Aug/Sep 2023 (new one must be due) is called Reflections on Reality, and it’s all of the above.
 
I’ve written on this topic many times before, so I’m sure to repeat myself. But Tallis’s essay, I felt, deserved both consideration and a response, partly because he starts with the one aspect of reality that we hardly ever ponder, which is doubting its existence.
 
Actually, not so much its existence, but whether our senses fool us, which they sometimes do, like when we dream (a point Tallis makes himself). And this brings me to the first point about reality that no one ever seems to discuss, and that is its dependence on consciousness, because when you’re unconscious, reality ceases to exist, for You. Now, you might argue that you’re unconscious when you dream, but I disagree; it’s just that your consciousness is misled. The point is that we sometimes remember our dreams, and I can’t see how that’s possible unless there is consciousness involved. If you think about it, everything you remember was laid down by a conscious thought or experience.
 
So, just to be clear, I’m not saying that the objective material world ceases to exist without consciousness – a philosophical position called idealism (advocated by Donald Hoffman) – but that the material objective world is ‘unknown’ and, to all intents and purposes, might as well not exist if it’s unperceived by conscious agents (like us). Try to imagine the Universe if no one observed it. It’s impossible, because the word, ‘imagine’, axiomatically requires a conscious agent.
 
Tallis proffers a quote from celebrated sci-fi author, Philip K Dick: 'Reality is that which, when you stop believing in it, doesn’t go away' (from The Shifting Realities of Philip K Dick, 1955). And this allows me to segue into the world of fiction, which Tallis doesn’t really discuss, but it’s another arena where we willingly ‘suspend disbelief' to temporarily and deliberately conflate reality with non-reality. This is something I have in common with Dick, because we have both created imaginary worlds that are more than distorted versions of the reality we experience every day; they’re entirely new worlds that no one has ever experienced in real life. But Dick’s aphorism expresses this succinctly. The so-called reality of these worlds, in these stories, only exist while we believe in them.
 
I’ve discussed elsewhere how the brain (not just human but animal brains, generally) creates a model of reality that is so ‘realistic’, we actually believe it exists outside our head.
 
I recently had a cataract operation, which was most illuminating when I took the bandage off, because my vision in that eye was so distorted, it made me feel sea sick. Everything had a lean to it and it really did feel like I was looking through a lens; I thought they had botched the operation. With both eyes open, it looked like objects were peeling apart. So I put a new eye patch on, and distracted myself for an hour by doing a Sudoku problem. When I had finished it, I took the patch off and my vision was restored. The brain had made the necessary adjustments to restore the illusion of reality as I normally interacted with it. And that’s the key point: the brain creates a model so accurately, integrating all our senses, but especially, sight, sound and touch, that we think the model is the reality. And all creatures have evolved that facility simply so they can survive; it’s a matter of life-and-death.
 
But having said all that, there are some aspects of reality that really do only exist in your mind, and not ‘out there’. Colour is the most obvious, but so is sound and smell, which all may be experienced differently by other species – how are we to know? Actually, we do know that some animals can hear sounds that we can’t and see colours that we don’t, and vice versa. And I contend that these sensory experiences are among the attributes that keep us distinct from AI.
 
Tallis makes a passing reference to Kant, who argued that space and time are also aspects of reality that are produced by the mind. I have always struggled to understand how Kant got that so wrong. Mind you, he lived more than a century before Einstein all-but proved that space and time are fundamental parameters of the Universe. Nevertheless, there are more than a few physicists who argue that the ‘flow of time’ is a purely psychological phenomenon. They may be right (but arguably for different reasons). If consciousness exists in a constant present (as expounded by Schrodinger) and everything else becomes the past as soon as it happens, then the flow of time is guaranteed for any entity with consciousness. However, many physicists (like Sabine Hossenfelder), if not most, argue that there is no ‘now’ – it’s an illusion.
 
Speaking of Schrodinger, he pointed out that there are fundamental differences between how we sense sight and sound, even though they are both waves. In the case of colour, we can blend them to get a new colour, and in fact, as we all know, all the colours we can see can be generated by just 3 colours, which is how the screens on all your devices work. However, that’s not the case with sound, otherwise we wouldn’t be able to distinguish all the different instruments in an orchestra. Just think: all the complexity is generated by a vibrating membrane (in the case of a speaker) and somehow our hearing separates it all. Of course, it can be done mathematically with a Fourier transform, but I don’t think that’s how our brains work, though I could be wrong.
 
And this leads me to discuss the role of science, and how it challenges our everyday experience of reality. Not surprisingly, Tallis also took his discussion in that direction. Quantum mechanics (QM) is the logical starting point, and Tallis references Bohr’s Copenhagen interpretation, ‘the view that the world has no definite state in the absence of observation.’ Now, I happen to think that there is a logical explanation for this, though I’m not sure anyone else agrees. If we go back to Schrodinger again, but this time his eponymous equation, it describes events before the ‘observation’ takes place, albeit with probabilities. What’s more, all the weird aspects of QM, like the Uncertainty Principle, superposition and entanglement, are all mathematically entailed in that equation. What’s missing is relativity theory, which has since been incorporated into QED or QFT.
 
But here’s the thing: once an observation or ‘measurement’ has taken place, Schrodinger’s equation no longer applies. In other words, you can’t use Schrodinger’s equation to describe something that has already happened. This is known as the ‘measurement problem’, because no one can explain it. But if QM only describes things that are yet to happen, then all the weird aspects aren’t so weird.
 
Tallis also mentions Einstein’s 'block universe', which infers past, present and future all exist simultaneously. In fact, that’s what Sabine Hossenfelder says in her book, Existential Physics:
 
The idea that the past and future exist in the same way as the present is compatible with all we currently know.

 
And:

Once you agree that anything exists now elsewhere, even though you see it only later, you are forced to accept that everything in the universe exists now. (Her emphasis.)
 
I’m not sure how she resolves this with cosmological history, but it does explain why she believes in superdeterminism (meaning the future is fixed), which axiomatically leads to her other strongly held belief that free will is an illusion; but so did Einstein, so she’s in good company.
 
In a passing remark, Tallis says, ‘science is entirely based on measurement’. I know from other essays that Tallis has written, that he believes the entire edifice of mathematics only exists because we can measure things, which we then applied to the natural world, which is why we have so-called ‘natural laws’. I’ve discussed his ideas on this elsewhere, but I think he has it back-to-front, whilst acknowledging that our ability to measure things, which is an extension of counting, is how humanity was introduced to mathematics. In fact, the ancient Greeks put geometry above arithmetic because it’s so physical. This is why there were no negative numbers in their mathematics, because the idea of a negative volume or area made no sense.
 
But, in the intervening 2 millennia, mathematics took on a life of its own, with such exotic entities like negative square roots and non-Euclidean geometry, which in turn suddenly found an unexpected home in QM and relativity theory respectively. All of a sudden, mathematics was informing us about reality before measurements were even made. Take Schrodinger’s wavefunction, which lies at the heart of his equation, and can’t be measured because it only exists in the future, assuming what I said above is correct.
 
But I think Tallis has a point, and I would argue that consciousness can’t be measured, which is why it might remain inexplicable to science, correlation with brain waves and their like notwithstanding.
 
So what is the mystery? Well, there’s more than one. For a start there is consciousness, without which reality would not be perceived or even be known, which seems to me to be pretty fundamental. Then there are the aspects of reality which have only recently been discovered, like the fact that time and space can have different ‘measurements’ dependent on the observer’s frame of reference. Then there is the increasing role of mathematics in our comprehension of reality at scales both cosmic and subatomic. In fact, given the role of numbers and mathematical relationships in determining fundamental constants and natural laws of the Universe, it would seem that mathematics is an inherent facet of reality.
 

Friday 18 August 2023

The fabric of the Universe

Brian Greene wrote an excellent book with a similar title (The Fabric of the Cosmos) which I briefly touched on here. Basically, it’s space and time, and the discipline of physics can’t avoid it. In fact, if you add mass and charge, you’ve got the whole gamut that we’re aware of. I know there’s the standard model along with dark energy and dark matter, but as someone said, if you throw everything into a black hole, the only thing you know about it is its mass, charge and angular momentum. Which is why they say, ‘a black hole has no hair.’ That was before Stephen Hawking applied the laws of thermodynamics and quantum mechanics and came up with Hawking radiation, but I’ve gone off-track, so I’ll come back to the topic-at-hand.
 
I like to tell people that I read a lot of books by people a lot smarter than me, and one of those books that I keep returning to is The Constants of Nature by John D Barrow. He makes a very compelling case that the only Universe that could be both stable and predictable enough to support complex life would be one with 3 dimensions of space and 1 of time. A 2-dimensional universe means that any animal with a digestive tract (from mouth to anus) would fall apart. Only a 3-dimensional universe allows planets to maintain orbits for millions of years. As Barrow points out in his aforementioned tome, Einstein’s friend, Paul Ehrenfest (1890-1933) was able to demonstrate this mathematically. It’s the inverse square law of gravity that keeps planets in orbit and that’s a direct consequence of everything happening in 3 dimensions. Interestingly, Kant thought it was the other way around – that 3 dimensions were a consequence of Newton’s universal law of gravity being an inverse square law. Mind you, Kant thought that both space and time were a priori concepts that only exist in the mind:
 
But this space and this time, and with them all appearances, are not in themselves things; they are nothing but representations and cannot exist outside our minds.
 
And this gets to the nub of the topic alluded to in the title of this post: are space and time ‘things’ that are fundamental to everything else we observe?
 
I’ll start with space, because, believe it or not, there is an argument among physicists that space is not an entity per se, but just dimensions between bodies that we measure. I’m going to leave aside, for the time being, that said ‘measurements’ can vary from observer to observer, as per Einstein’s special theory of relativity (SR).
 
This argument arises because we know that the Universe is expanding (by measuring the Doppler-shift of stars); but does space itself expand or is it just objects moving apart? In another post, I referenced a paper by Tamara M. Davis and Charles H. Lineweaver from UNSW (Expanding Confusion: Common Misconceptions of Cosmological Horizons and the Superluminal Expansion of the Universe), which I think puts an end to this argument, when they explain the difference between an SR and GR Doppler shift interpretation of an expanding universe.
 
The general relativistic interpretation of the expansion interprets cosmological redshifts as an indication of velocity since the proper distance between comoving objects increases. However, the velocity is due to the rate of expansion of space, not movement through space, and therefore cannot be calculated with the special relativistic Doppler shift formula. (My emphasis)
 
I’m now going to use a sleight-of-hand and attempt a description of GR (general theory of relativity) without gravity, based on my conclusion from their exposition.
 
The Universe has a horizon that’s directly analogous to the horizon one observes at sea, because it ‘moves’ as the observer moves. In other words, other hypothetical ‘observers’ in other parts of the Universe would observe a different horizon to us, including hypothetical observers who are ‘over-the-horizon’ relative to us.
 
But the horizon of the Universe is a direct consequence of bodies (or space) moving faster-than-light (FTL) over the horizon, as expounded upon in detail in Davis’s and Lineweaver’s paper. But here’s the thing: if you were an observer on one of these bodies moving FTL relative to Earth, the speed of light would still be c. How is that possible? My answer is that the light travels at c relative to the ‘space’* (in which it’s observed), but the space itself can travel faster than light.
 
There are, of course, other horizons in the Universe, which are event horizons of black holes. Now, you have the same dilemma at these horizons as you do at the Universe’s horizon. According to an external observer, time appears to ‘stop’ at the event horizon, because the light emitted by an object can’t reach us. However, for an observer at the event horizon, the speed of light is still c, and if the black hole is big enough, it’s believed (obviously no one can know) that someone could cross the event horizon without knowing they had. But what if it’s spacetime that crosses the event horizon? Then both the external observer’s perception and the comoving observer’s perception would be no different if the latter was at the horizon of the entire universe.
 
But what happens to time? Well, if you measure time by the frequency of light being emitted from an object at any of these horizons, it gets Doppler-shifted to zero, so time ‘stops’ for the ‘local’ observer (on Earth) but not for the observer at the horizon.
 
So far, I’ve avoided talking about quantum mechanics (QM), but something curious happens when you apply QM to cosmology: time disappears. According to Paul Davies in The Goldilocks Enigma: ‘…vanishing of time for the entire universe becomes very explicit in quantum cosmology, where the time variable simply drops out of the quantum description.’ This is consistent with Freeman Dyson’s argument that QM can only describe the future. Thus, if you apply a description of the future to the entire cosmos, there would be no time.
 
 
* Note: you can still apply SR within that ‘space’.

 

Addendum: I've since learned that in 1958, David Finkelstein (a postdoc with the Stevens Institute of Technology in Hoboken, New Jersey) wrote an article in Physical Review that gave the same explanation for how time appears different to different observers of a black hole, as I do above. It immediately grabbed the attention (and approval) of Oppenheimer, Wheeler and Penrose (among others), who had struggled to resolve this paradox. (Ref. Black Holes And Time Warps; Einstein's Outrageous Legacy, Kip S. Thorne, 1994)
 

Monday 14 November 2022

Kant and modern physics

 I wrote a post on Kant back in February 2020, but it was actually an essay I wrote more than 20 years earlier, when I was a student of philosophy. I would not be able to improve on that essay, and I’m not about to try now. In that essay, I argue that Kant’s great contribution to philosophy, and epistemology in particular, was his idea of the ‘thing-in-itself’, which may remain forever unknowable, as we only have our perceptions of ‘things’.
 
In other posts, I have sometimes argued that the ‘thing-in-itself’ is dependent on the scale that we can observe it, but there is something deeper that I think only became apparent in the so-called golden age of physics in the 20th Century. In a more recent post, I pointed out that both relativity theory and quantum mechanics (the 2 pillars of modern physics) are both observer dependent. I argue that there could be an objective ontology that they can’t describe. I think this is more obvious in the case of special relativity, where different observers literally measure different durations of both space and time, but I’m getting ahead of myself.
 
On Quora, there are 4 physicists whom I ‘follow’ and read regularly. They are Viktor T Toth, Richard Muller, Mark John Fernee and Ian Miller. Out of these, Miller is possibly the most contentious as he argues against non-locality in QM (quantum mechanics), which I’m not aware of any other physicist concurring with. Of course, it’s Bell’s Inequality that provides the definitive answer to this, of which Miller has this to say:
 
If you say it must because of violations of Bell’s Inequality, first note that the inequality is a mathematical relationship that contains only numbers; no physical concept is included.
 
But the ‘numbers’ compare classical statistical outcomes with Born statistical outcomes and experiments verify Born’s results, so I disagree. Having said that, Miller makes pertinent points that I find insightful and, like all those mentioned, he knows a lot more about this topic than me.
 
For example, concerning relativity, he argues that it’s the ruler that changes dimension and not the space being measured. He also points out, regarding the twin paradox, that only one twin gains energy, which is the one whose clock slows down. Note that clocks are also a form of ‘ruler’, but they measure time instead of space. So you can have 2 observers who ‘measure’ different durations of space and time, but agree on ‘now’, when they reunite, as is the case with the twin paradox thought experiment.
 
This point is slightly off-track, but not irrelevant to the main focus of this post. The main focus is an academic paper jointly written by Shaun Maguire and Richard Muller, titled Now, and the Flow of Time. This paper is arguably as contentious as Miller’s take on non-locality and Bell, because Muller and Maguire argue that ‘space’ can be created.
 
Now, Viktor T Toth is quite adamant that space is not created because space is not an entity, but a ‘measurement’ between entities called ‘objects’. Now, it has to be said, that Muller has stated publicly on Quora that he has utmost respect for Toth and neither of them have called each other out over this issue.
 
Toth argues that people confound the mathematical metric with ‘space’ or ‘spacetime’, but I’d argue that this mathematical metric has physical consequences. In another post, I reference another paper, recommended to me by Mark John Fernee (authored by Tamara M. Davis and Charles H. Lineweaver at the University of New South Wales) which describes how a GR Doppler shift intrinsically measures the expansion of space.
 
The general relativistic interpretation of the expansion interprets cosmological redshifts as an indication of velocity since the proper distance between comoving objects increases. However, the velocity is due to the rate of expansion of space, not movement through space, and therefore cannot be calculated with the special relativistic Doppler shift formula.
(My emphasis)
 
As I explain in that post: ‘What they are effectively saying is that there is a distinction between the movement of objects in space and the movement of space itself.’
 
The spacetime metric that Toth refers to provides a reference frame for c, the speed of light. So, whilst a spacetime metric (‘space’ by another name) can travel faster than light with respect to us (so over the horizon of the observable universe), an observer situated in that metric would still measure light as c relative to them.
 
Muller’s and Maguire’s paper goes even further, saying that space is created along with time, and they believe this can be measured as ‘a predicted lag in the emergence of gravitational radiation when two black holes merge.’ I won’t go into the details; you would need to read the paper.
 
A conclusion implicit in their theory is that there could be a universal now.
 
A natural question arises: why are the new nows created at the end of time, rather than uniformly throughout time, in the same way that new space is uniformly created throughout the universe.

 
The authors then provide alternative arguments, which I won’t go into, but they do ponder the fundamental difference between space and time, where one is uni-directional and the other is not. As far as we know, there is no ‘edge’ in space but there is in time. Muller and Maguire do wonder if space is ‘created’ throughout the Universe (as quoted above) or at an ‘edge’.
 
You may wonder how does Kant fit into all this? It’s because all these discussions are dependent on what we observe and what we theorise, both of which are perceptions. And, in physics, theorising involves mathematics. I’ve argued that mathematics can be seen as another medium determining perceptions, along with all the instruments we’ve built that now include the LHC and the Hubble and Webb telescopes.
 
Sabine Hossenfelder, whom I often reference on this blog these days, wrote a book, called Lost in Math, where she interviews some of the brightest minds in physics and challenges the pervading paradigm that mathematics can provide answers to questions that experimentation can’t – string theory being the most obvious.

Before the revolution in cosmology, created by Copernicus and built on by Galileo, Kepler and Newton, people believed that the Sun went round the Earth and that some objects in the night sky would occasionally backtrack in their orbits, which was explained by epicycles. That was overturned, and now it seems obvious that, in fact, the Earth rotates on its axis and orbits the sun along with all the other planets, which explains our ‘perception’ that sometimes the planets go ‘backwards.’
 
I wonder if the next revolution in science and cosmology may also provide a ‘simpler’ picture, where there is a ‘universal now’ that explains the age of the Universe, the edge of time that we all experience and non-locality in QM.
 
Of course, I’m probably wrong.

Addendum: This is Richard Muller talking about time on Quora.

Sunday 25 September 2022

What we observe and what is reality are distinct in physics

 I’ve been doing this blog for 15 years now, and in that time some of my ideas have changed or evolved, and, in some areas, my knowledge has increased. As I’ve said on Quora a few times, I read a lot of books by people who know a lot more than me, especially in physics.
 
There is a boundary between physics and philosophy, the shoreline of John Wheeler’s metaphorical ‘island of knowledge in the infinite sea of ignorance’. To quote: “As the island grows so does the shoreline of our ignorance.” And I think ignorance is the key word here, because it’s basically speculation, which means some of us are wrong, including me, most likely. As I’ve often said, ‘Only future generations can tell us how ignorant the current generation is’. I can say that with a lot of confidence, just by looking at the history of science.
 
If this blog has a purpose beyond promoting my own pet theories and prejudices, it is to make people think.
 
Recently, I’ve been pre-occupied with determinism and something called superdeterminism, which has become one of those pet prejudices among physicists in the belief that it’s the only conclusion one can draw from combining relativity theory, quantum mechanics, entanglement and Bell’s theorem. Sabine Hossenfelder is one such advocate, who went so far as to predict that one day all other physicists will agree with her. I elaborate on this below.
 
Mark John Fernee (physicist with Qld Uni), with whom I’ve had some correspondence, is one who disagrees with her. I believe that John Bell himself proposed that superdeterminism was possibly the only resolution to the quandaries posed by his theorem. There are two other videos worth watching, one by Elijah Lew-Smith and a 50min one by Brian Greene, who doesn’t discuss superdeterminism. Nevertheless, Greene’s video gives the best and easiest to understand description of Bell’s theorem and its profound implications for reality.
 
So what is super-determinism, and how is it distinct from common or garden determinism? Well, if you watch the two relevant videos, you get two different answers. According to Sabine, there is no difference and it’s not really to do with Bell’s theorem, but with the measurement problem in QM. She argues that it’s best explained by looking at the double-slit experiment. Interestingly, Richard Feynman argued that all the problems associated with QM can be analysed, if not understood, by studying the double-slit experiment.
 
Sabine wrote an academic paper on the ‘measurement problem’, co-authored with Jonte R. Hance from the University of Bristol, which I’ve read and is surprisingly free of equations (not completely) but uses the odd term I’m unfamiliar with. I expect I was given a link by Fernee which I’ve since lost (I really can’t remember), but I still have a copy. One of her points is that as long as we have unsolved problems in QM, there is always room for different philosophical interpretations, and she and Hance discuss the most well-known ones. This is slightly off-topic, but only slightly, because even superdeterminism and its apparent elimination of free will is a philosophical issue.
 
Sabine argues that it’s the measurement that creates superdeterminism in QM, which is why she uses the double-slit experiment to demonstrate it. It’s because the ‘measurement’ ‘collapses’ the wave function and ‘determines’ the outcome, that it must have been ‘deterministic’ all along. It’s just that we don’t know it until a measurement is made. At least, this is my understanding of her argument.
 
The video by Elijah Lew-Smith gives a different explanation, focusing solely on Bell’s theorem. I found that it also required more than one viewing, but he makes a couple of points, which I believe go to the heart of the matter. (Greene’s video gives an easier-to-follow description, despite its length).
 
We can’t talk about an objective reality independent of measurement.
(Which echoes Sabine’s salient point in her video.)
 
And this point: There really are instantaneous interactions; we just can’t access them.
 
This is known as ‘non-locality’, and Brian Greene provides the best exposition I’ve seen, and explains how it’s central to Bell’s theorem and to our understanding of reality.
 
On the other hand, Lew-Smith explains non-locality without placing it at the centre of the discussion.
 
If I can momentarily go back to Sabine’s key argument, I addressed this in a post I wrote a few years back. Basically, I argued that you can only know the path an electron or photon takes retrospectively, after the measurement or observation has been made. Prior to that, QM tells us it’s in a superposition of states and we only have probabilities of where it will land. Curiously, I referenced a video by Sabine in a footnote, where she makes this point in her conclusion:
 
You don’t need to know what happens in the future because the particle goes to all points anyway. Except…  It doesn’t. In reality, it goes to only one point. So maybe the reason we need the measurement postulate is because we don’t take this dependency on the future seriously enough.
 
And to me, that’s what this is all about: the measurement is in the future of the wave function, and the path it takes is in the past. This, of course, is what Freeman Dyson claims: that QM cannot describe the past, only the future.
 
And if you combine this perspective with Lew-Smith’s comment about objective reality NOT being independent of the measurement, then objective reality only exists in the past, while the wave function and all its superpositional states exist in the future.
 
So how does entanglement fit into this? Well, this is the second point I highlighted, which is that ‘there really are instantaneous reactions, which we can’t access’, which is ‘non-locality’. And this, as Schrodinger himself proclaimed, is what distinguishes QM from classical physics. In classical physics, ‘locality’ means there is a relativistic causal connection and in entanglement there is not, which is why Einstein called it ‘spooky action at a distance’.
 
Bell’s theorem effectively tells us that non-locality is real, supported by experiment many times over, but you can’t use it to transmit information faster-than-light, so relativity is not violated in practical terms. But it does ask questions about simultaneity, which is discussed in Lew-Smith’s video. He demonstrates graphically that different observers will observe a different sequence of measurement, so we have disagreement, even a contradiction about which ‘measurement’ collapsed the wave function. And this is leads to superdeterminism, because, if the outcome is predetermined, then the sequence of measurement doesn’t matter.
 
And this gets to the nub of the issue, because it ‘appears’ that ‘objective reality’ is observer dependent. Relativity theory always gives the result from a specific observer’s point of view and different observers in different frames of reference can epistemically disagree. Is there a frame of reference that is observer independent? I always like to go back to the twin paradox, because I believe it provides an answer. When the twins reunite, they disagree on how much time has passed, yet they agree on where they are in space-time. There is not absolute time, but there is absolute space-time.
 
Did you know we can deduce the velocity that Earth travels relative to absolute space-time, meaning the overall observable Universe? By measuring the Doppler shift of the CMBR (cosmic microwave background radiation) in all directions, it’s been calculated that we are travelling at 350km/s in the direction of Pisces (ref., Paul Davies, About Time; Einstein’s Unfinished Revolution, 1995). They should teach this in schools.
 
Given this context, is it possible that entanglement is a manifestation of objective simultaneity? Not according to Einstein, who argued that: ‘The past, present and future is only a stubbornly persistent illusion’; which is based on the ‘fact’ that simultaneity is observer dependent. But Einstein didn’t live to see Bell’s theorem experimentally verified. Richard Muller, a prize-winning physicist and author (also on Quora) was asked what question he’d ask Einstein if he could hypothetically meet him NOW. I haven’t got a direct copy, but essentially Muller said he’d ask Einstein if he now accepted a ‘super-luminal connection’, given experimental confirmation of Bell’s theorem. In other words, entanglement is like an exception to the rule, where relativity strictly doesn’t apply.
 
Sabine with her co-author, Jonte Hance, make a passing comment that the discussion really hasn’t progressed much since Bohr and Einstein a century ago, and I think they have a point.
 
Mark Fernee, whom I keep mentioning on the sidelines, does make a distinction between determinism and superdeterminism, where determinism simply means that everything is causally connected to something, even if it’s not predictable. Chaos being a case-in-point, which he describes thus:
 
Where this determinism breaks down is with chaotic systems, such as three body dynamics. Chaotic systems are so sensitive to the initial parameters that even a slight inaccuracy can result in wildly different predictions. That's why predicting the weather is so difficult.
Overall, complexity limits the ability to predict the future, even in a causal universe.

 
On the other hand, superdeterminism effectively means the end of free will, and, in his own words, ‘free will is a contentious issue, even among physicists’.
 
Fernee provided a link to another document by Sabine, where she created an online forum specifically to deal with less than knowledgeable people about their disillusioned ideas on physics – crackpots and cranks. It occurred to me that I might fall into this category, but it’s for others to judge. I’m constantly reminded of how little I really know, and that I’m only fiddling around the edges, or on the ‘shoreline of ignorance’, as Wheeler described it, where there are many others far more qualified than me.
 
I not-so-recently wrote a post where I challenged a specific scenario often cited by physicists, where two observers hypothetically ‘observe’ contradictory outcomes of an event on a distant astronomical body that is supposedly happening simultaneously with them.
 
As I said before, relativity is an observer-dependent theory, almost by definition, and we know it works just by using the GPS on our smart-phones. There are algorithms that make relativistic corrections to the signals coming from the satellites, otherwise the map on your phone would not match the reality of your actual location.
 
What I challenge is the application of relativity theory to an event that the observer can’t observe, even in principle. In fact, relativity theory rules out a physical observation of a purportedly simultaneous event. So I’m not surprised that we get contradictory results. The accepted view among physicists is that each observer ‘sees’ a different ontology (one in the future and one in the past), whereas I contend that there is an agreed ontology that becomes observable at a later time, when it’s in both observers’ past. (Brian Greene has another video demonstrating the ‘conventional’ view among physicists.)
 
Claudia de Rahm is Professor of Physics at Imperial College London, and earlier this year, she gave a talk titled, What We Don’t Know About Gravity, where she made the revelatory point
that Einstein’s GR (general theory of relativity) predicted its own limitations. Basically, if you apply QM probabilities to extreme curvature spacetime, you get answers over 100%, so nonsense. GR and QM are mathematically incompatible if we try to quantise gravity, though QFT (quantum field theory) ‘works fine on the manifold of spacetime’, according to expert, Viktor T Toth.
 
Given that relativity theory, as it is applied, is intrinsically observer dependent, I question if it can be (reliably) applied to events that have no causal relation to the observer (meaning outside the observer's light cone, both past and future). Which is why I challenge its application to events the observer can't observe (refer 2 paragraphs ago).

 

Addendum: I changed the title so it's more consistent with the contents of the post. The previous title was Ignorance and bliss; philosophy and science. Basically, the reason we have different interpretations of the same phenomenon is because physics can only tell us about what we observe, and what that means for reality is often debatable; superdeterminism being a case in point. Many philosophers and scientists talk about a ‘gap’ between theory and reality, whereas I claim the gap is between the observation and reality, a la Kant.

Wednesday 7 September 2022

Ontology and epistemology; the twin pillars of philosophy

 I remember in my introduction to formal philosophy that there were 5 branches: ontology, epistemology, logic, aesthetics and ethics. Logic is arguably subsumed under mathematics, which has a connection with ontology and epistemology through physics, and ethics is part of all our lives, from politics to education to social and work-related relations to how one should individually live. Aesthetics is like an orphan in this company, yet art is imbued in all cultures in so many ways, it is unavoidable.
 
However, if you read about Western philosophy, the focus is often on epistemology and its close relation, if not utter dependence, on ontology. Why dependence? Because you can’t have knowledge of something without inferring its existence, even if the existence is purely abstract.
 
There are so many facets to this, that it’s difficult to know where to start, but I will start with Kant because he argued that we can never know ‘the-thing-in-itself’, only a perception of it, which, in a nutshell, is the difference between ontology and epistemology.
 
We need some definitions, and ontology is dictionary defined as the ‘nature of being’, while epistemology is ‘theory of knowledge’, and with these definitions, one can see straightaway the relationship, and Kant’s distillation of it.
 
Of course, one can also see how science becomes involved, because science, at its core, is an epistemological endeavour. In reading and researching this topic, I’ve come to the conclusion that, though science and philosophy have common origins in Western scholarship, going back to Plato, they’ve gone down different paths.
 
If one looks at the last century, which included the ‘golden age of physics’, in parallel with the dominant philosophical paradigm, heavily influenced, if not initiated, by Wittgenstein, we see that the difference can be definitively understood in terms of language. Wittgenstein effectively redefined epistemology as how we frame the world with language, while science, and physics in particular, frames the world in mathematics. I’ll return to this fundamental distinction later.
 
In my last post, I went to some lengths to argue that a fundamental assumption among scientists is that there is an ‘objective reality’. By this, I mean that they generally don’t believe in ‘idealism’ (like Donald Hoffman) which is the belief that objects don’t exist when you don’t perceive them (Hoffman describes it as the same experience as using virtual-reality goggles). As I’ve pointed out before, this is what we all experience when we dream, which I contend is different to the experience of our collective waking lives. It’s the word, ‘collective’, that is the key to understanding the difference – we share waking experiences in a way that is impossible to corroborate in a dream.
 
However, I’ve been reading a lot of posts on Quora by physicists, Viktor T Toth and Mark John Fernee (both of whom I’ve cited before and both of whom I have a lot of respect for). And they both point out that much of what we call reality is observer dependent, which makes me think of Kant.
 
Fernee, when discussing quantum mechanics (QM) keeps coming back to the ‘measurement problem’ and the role of the observer, and how it’s hard to avoid. He discusses the famous ‘Wigner’s friend’ thought experiment, which is an extension of the famous Schrodinger’s cat thought experiment, which infers you have the cat in 2 superpositional states: dead and alive. Eugne Wigner developed a thought experiment, whereby 2 experimenters could get contradictory results. Its relevance to this topic is that the ontology is completely dependent on the observer. My understanding of the scenario is that it subverts the distinction between QM and classical physics.
 
I’ve made the point before that a photon travelling across the Universe from some place and time closer to its beginning (like the CMBR) is always in the future of whatever it interacts with, like, for example, an ‘observer’ on Earth. The point I’d make is that billions of years of cosmological time have passed, so in another sense, the photon comes from the observer’s past, who became classical a long time ago. For the photon, time is always zero, but it links the past to the present across almost the entire lifetime of the observable universe.
 
Quantum mechanics, more than any other field, demonstrates the difference between ontology and epistemology, and this was discussed in another post by Fernee. Epistemologically, QM is described mathematically, and is so successful that we can ignore what it means ontologically. This has led to diverse interpretations from the multiple worlds interpretation (MWI) to so-called ‘hidden variables’ to the well known ‘Copenhagen interpretation’.
 
Fernee, in particular, discusses MWI, not that he’s an advocate, but because it represents an ontology that no one can actually observe. Both Toth and Fernee point out that the wave function, which arguably lies at the heart of QM is never observed and neither is its ‘decoherence’ (which is the measurement problem by another name), which leads many to contend that it’s a mathematical fiction. I argue that it exists in the future, and that only classical physics is actually observed. QM deals with probabilities, which is purely epistemological. After the ‘observation’, Schrodinger’s equation, which describes the wave function ceases to have any meaning. One is in the future and the observation becomes the past as soon as it happens.
 
I don’t know enough about it, but I think entanglement is the key to its ontology. Fernee points out in another post that entanglement is to do with conservation, whether it be the conservation of momentum or, more usually, the conservation of spin. It leads to what is called non-locality, according to Bell’s Theorem, which means it appears to break with relativistic physics. I say ‘appears’, because it’s well known that it can’t be used to send information faster than light; so, in reality, it doesn’t break relativity. Nevertheless, it led to Einstein’s famous quote about ‘spooky action at a distance’ (which is what non-locality means in layperson’s terms).
 
But entanglement is tied to the wave function decoherence, because that’s when it becomes manifest. It’s crucial to appreciate that entangled particles are described by the same wave function and that’s the inherent connection. It led Schrodinger to claim that entanglement is THE defining feature of QM; in effect, it’s what separates QM from classical physics.
 
I think QM is the best demonstration of Kant’s prescient claim that we can never know the-thing-in-itself, but only our perception of it. QM is a purely epistemological theory – the ontology it describes still eludes us.
 
But relativity theory also suggests that reality is observer dependent. Toth points out that even the number of particles that are detected in some scenarios are dependent on the frame of reference of the observer. This has led at least one physicist (on Quora) to argue that the word ‘particle’ should be banned from all physics text books – there are only fields. (Toth is an expert on QFT, quantum field theory, and argues that particles are a manifestation of QFT.) I won’t elaborate as I don’t really know enough, but what’s relevant to this topic is that time and space are observer dependent in relativity, or appear to be.
 
In a not-so-recent post, I described how different ‘observers’ could hypothetically ‘see’ the same event happening hundreds of years apart, just because they are walking across a street in opposite directions. I use quotation marks, because it’s all postulated mathematically, and, in fact, relativity theory prevents them from observing anything outside their past and future light cones. I actually discussed this with Fernee, and he pointed out that it’s to do with causality. Where there is no causal relation between events, we can’t determine an objective sequence let alone one relevant to a time frame independent of us (like a cosmic time frame). And this is where I personally have an issue, because, even though we can’t observe it or determine it, I argue that there is still an objective reality independently of us.
 
In relativity there is something called true time (τ) which is the time in the frame of reference of the observer. If spacetime is invariant, then it would logically follow that where you have true time you should have an analogous ‘true space’, yet I’ve never come across it. I also think there is a ‘true simultaneity’ but no one else does, so maybe I’m wrong.
 
There is, however, something called the Planck length, and someone asked Toth if this changed relativistically with the Lorenz transformation, like all other ‘rulers’ in relativity physics. He said that a version of relativity was formulated that made the Planck length invariant but it created problems and didn’t agree with experimental data. What I find interesting about this is that Planck’s constant, h, literally determines the size of atoms, and one doesn’t expect atoms to change size relativistically (but maybe they do). The point I’d make is that these changes are observer dependent, and I’d argue that there is a Planck length that is observer independent, which is the case when there is no observer.
 
This has become a longwinded way of explaining how 20th Century science has effectively taken this discussion away from philosophy, but it’s rarely acknowledged by philosophers, who take refuge in Wittgenstein’s conclusion that language effectively determines what we can understand of the world, because we think in a language and that limits what we can conceptualise. And he’s right, until we come up with new concepts requiring new language. Everything I’ve just discussed was completely unknown more than 120 years ago, for which we had no language, let alone concepts.
 
Some years ago, I reviewed a book by Don Cupitt titled, Above Us Only Sky, which was really about religion in a secular world. But, in it, Cupitt repeatedly argued that things only have meaning when they are ‘language-wrapped’ (his term) and I now realise that he was echoing Wittgenstein. However, there is a context in which language is magical, and that is when it creates a world inside your head, called a story.
 
I’ve been reading Bryan Magee’s The Great Philosophers, based on a series of podcasts with various academics in 1987, which started with Plato and ended with Wittgenstein. He discussed Plato with Myles Burnyeat, Professor of Ancient Philosophy at Oxford. Naturally, they discussed Socrates, the famous dialogues and the more famous Republic, but towards the end they turned to the Timaeus, which was a work on ‘mathematical science’, according to Burnyeat, that influenced Aristotle and Ptolemy.
 
It's worth quoting their last exchange verbatim:
 
Magee: For us in the twentieth century there is something peculiarly contemporary about the fact that, in the programme it puts forward for acquiring an understanding of the world, Plato’s philosophy gives a central role to mathematical physics.
 
Burnyeat: Yes. What Plato aspired to do, modern science has actually done. And so there is a sort of innate sympathy between the two which does not hold for Aristotle’s philosophy. (My emphasis)


Addendum: This is a very good exposition on the 'measurement problem' by Sabine Hossenfelder, which also provides a very good synopsis of the wave function (ψ), Schrodinger's equation and the Born rule.

Tuesday 16 August 2022

How does science work?

 This post effectively piggybacks onto my last post, because, when it comes to knowledge and truth, nothing beats science except mathematics. It also coincides with me watching videos of Bryan Magee talking to philosophers, from 30 to 40 years ago and more. I also have a book with a collection of these ‘discussions’, so the ones I can’t view, I can read about. One gets an overall impression from these philosophers that, when it comes to understanding the philosophy of science, the last person you should ask is a scientist.
 
Now, I’m neither a scientist nor a proper philosopher, but it should be obvious to anyone who reads this blog that I’m interested in both. And where others see a dichotomy or a grudging disrespect, I see a marriage. There is one particular discussion that Magee has (with Hilary Putnam from Harvard, in 1977) that is headlined, The Philosophy of Science. Now, where Magee and his contemporaries turn to Kant, Hume and Descartes, I turn to Paul Davies, Roger Penrose and Richard Feynman, so the difference in perspective couldn’t be starker.
 
Where to start? Maybe I’ll start with a reference to my previous post by contending that what science excels in is explanation. In fact, one could define a scientific theory as an attempted explanation of a natural phenomenon, and science in general as the attempt to explain natural phenomena in all of their manifestations. This axiomatically rules out supernatural phenomena and requires that the natural phenomenon under investigation can be observed, either directly or indirectly, and increasingly with advanced technological instruments.
 
It's the use of the word ‘attempt’ that is the fly in the ointment, and requires elaboration. I use the word, attempt, because all theories, no matter how successful, are incomplete. This goes to the core of the issue and the heart of any debate concerning the philosophy of science, which hopefully becomes clearer as I progress.
 
But I’m going to start with what I believe are a couple of assumptions that science makes even before it gets going. One assumption is that there is an objective reality. This comes up if one discusses Hume, as Magee does with Professor John Passmore (from ANU). I don’t know when this took place, but it was before 1987 when the collection was published. Now, neither Magee nor Passmore are ‘idealists’ and they don’t believe Hume was either, but they iterate Hume’s claim that you can never know for certain that the world doesn’t exist when you’re not looking. Stephen Hawking also references this in his book, The Grand Design. In this context, idealism refers to a philosophical position that the world only exists as a consequence of minds (Donald Hoffman is the best known contemporary advocate). This is subtly different to ‘solipsism’, which is a condition we all experience when we dream, both of which I’ve discussed elsewhere.
 
There is an issue with idealism that is rarely discussed, at least from my limited exposure to the term, which is that everything must only exist in the present – there can be no history - if everything physically disappears when unobserved. And this creates a problem with our current knowledge of science and the Universe. We now know, though Hume wouldn’t have known, that we can literally see hundreds and even thousands of years into the past, just by looking at the night sky. In fact, using the technology I alluded to earlier, we can ‘observe’ the CMBR (cosmic microwave background radiation), so 380,000 years after the Big Bang (13.8 billion years ago). If there is no ‘objective reality’ then the science of cosmology makes no sense. I’m not sure how Hoffman reconciles that with his view, but he has similar problems with causality, which I’ll talk about next, because that’s the other assumption that I believe science makes.
 
This again rubs up against Hume, because it’s probably his most famous philosophical point that causality uses an inductive logic that can’t be confirmed. Just because 2 events happen sequentially, there is no way you can know that one caused the other. To quote Passmore in his conversation with Magee: “exactly how does past experience justify a conclusion about future behaviour?” In other words, using the example that Passmore does, just because you saw a rubber ball bounce yesterday, how can you be sure that it will do the same tomorrow? This is the very illustration of ‘inductive reasoning’.
 
To give another example that is often used to demonstrate this view in extremis, just because night has followed day in endless cycles for millennia, doesn’t guarantee it’s going to happen tomorrow. This is where science enters the picture because it can provide an explanation, which as I stated right at the beginning, is the whole raison d’etre of science. Night follows day as a consequence of the Earth rotating on its axis. In another post, written years ago, I discussed George Lakoff’s belief that all things philosophical and scientific can be understood as metaphor, so that the relationship between circular motion and periodicity is purely metaphorical. If one takes this to its logical conclusion, the literal everyday experience of night and day is just a metaphor.
 
But getting back to Hume’s scepticism, science shows that there is a causal relationship between the rotation of the Earth and our experience of night and day. This is a very prosaic example, but it demonstrates that the premise of causality lies at the heart of science. Remember, it’s only in the last 400 years or so that we discovered that the Earth rotates. This was the cause of Galileo’s fatally close encounter with the Inquisition, because it contradicted the Bible.
 
Now, some people, including Hoffman (he’s my default Devil’s advocate), argue that quantum mechanics (QM) rules out causality. I think Mark John Fernee (physicist with the University of Queensland) provides the best response by explaining how Born’s rule provides a mathematically expressed causal link between QM and classical physics. He argues, in effect, that it’s the ‘collapse’ of the wave function in QM that gives rise to the irreversibility in time between QM and classical physics (the so-called ‘measurement problem’) but is expressed as a probability by the Born rule, before the measurement or observation takes place. That’s longwinded and a little obtuse, but the ‘measurement’ turns a probability into an actual event – the transition from future to past (to paraphrase Freeman Dyson).
 
On the other hand, Hoffman argues that there is no causality in QM. To quote from the academic paper he cowrote with Chetan Prakash:
 
Our views on causality are consistent with interpretations of quantum theory that abandon microphysical causality… The burden of proof is surely on one who would abandon microphysical causation but still cling to macrophysical causation.
 
So Hoffman seems to think that there is a scientific consensus that causality does not arise in QM. But it’s an intrinsic part of the ‘measurement problem’, which is literally what is observed but eludes explanation. To quote Fernee:
 
While the Born rule looks to be ad hoc, it actually serves the function of ensuring that quantum mechanics obeys causality by ensuring that a quantum of action only acts locally (I can't actually think of any better way to state this). Therefore there really has to be a Born rule if causality is to hold.
 
Leaving QM aside, my standard response to this topic is somewhat blunt: if you don’t believe in causality, step in front of a bus (it’s a rhetorical device, not an instruction). Even Hoffman acknowledges in an online interview that he wouldn’t step in front of a train. I thought his argument specious because he compared it to taking an icon on a computer desktop (his go-to analogy) and putting it in the trash can. He exhorts us to take the train "seriously but not literally", just like a computer desktop icon (watch this video from 26.30 min).

That’s a lengthy detour, but causality is a such a core ‘belief’ in science that it couldn’t be ignored or glossed over.
 
Magee, in his discussion with Passmore, uses Einstein’s theory of gravity superseding Newton’s as an example of how a subsequent scientific theory can prove a previous theory ‘wrong’. In fact, Passmore compares it with the elimination of the ‘phlogiston’ theory by Lavoisier. But there is a dramatic difference. Phlogiston was a true or false theory in the same way that the Sun going around the Earth was a true or false theory, and, in both cases, they were proven ‘wrong’ by subsequent theories. That is not the case with Newton’s theory of gravitation.
 
It needs to be remembered that Newton’s theory was no less revolutionary than Einstein’s. He showed that the natural mechanism which causes (that word again) an object to fall to the ground on Earth is exactly the same mechanism that causes the moon to orbit the Earth. There is a reason why Newton is one of the few intellectual giants in history who is commonly compared with the more recent intellectual giant, Einstein.
 
My most pertinent point that I made right at the start is that all scientific theories are incomplete, and this applies to both Newton’s and Einstein’s theories of gravity. It’s just that Einstein’s theory is less incomplete than Newton’s and that is the real difference. And this is where I collide head-on with Magee and his interlocutors. They argue that the commonly held view that science progresses as a steady accumulation of knowledge is misleading, while I’d argue that the specific example they give – Einstein versus Newton – demonstrates that is exactly how science progresses, only it happens in quantum leaps rather than incrementally.
 
Thomas Kuhn wrote a seminal book, The Structure of Scientific Revolutions, which challenged the prevailing view that science progresses by incremental steps and this is the point that Magee is making. On this I agree: science has progressed by revolutions, yet it has still been built on what went before. As Claudia de Rahm (whom I wrote about in a former post) makes clear in a discussion on Einstein’s theory of gravity: any new theory that replaces it has to explain what the existing theory already explains. She specifically says, in answer to a question from her audience, that you don’t throw what we already know to be true (from empirical evidence) ‘into the rubbish bin’. And Einstein faced this same dilemma when he replaced Newton’s theory. In fact, one of his self-imposed criteria was that his theory must be mathematically equivalent to Newton’s when relativistic effects were negligible, which is true in most circumstances.
 
Passmore argues that Einstein’s theory even contradicts Newton’s theory, without being specific. The thing is that Einstein’s revolution affected the very bedrock of physics, being space and time. So maybe that’s what he’s referring to, because Newton’s theory assumed there was absolute space and absolute time, which Einstein effectively replaced with absolute spacetime.
 
I’ve discussed this in another post, but it bears repeating, because it highlights the issue in a way that is easily understood. Newton asks you to imagine a spinning bucket of water and observe what happens. And what happens is that the water surface becomes concave as a consequence of centrifugal forces. He then asked, what is it spinning in reference to? The answer is Earth, but the experiment applies to every spinning object in the Universe, including galaxies. They weren’t known in Newton’s time, nevertheless he had the insight to appreciate that the bucket spun relative to the stars in the night sky – in other words, with respect to the whole cosmos. Therefore, he concluded there must be absolute space, which is not spinning. Einstein, in answer to the same philosophical question, replaced absolute space with absolute spacetime.
 
In last week’s New Scientist (6 August 2022), Chanda Prescod-Weinstein (Assistant Professor in physics and astronomy at New Hampshire University) spent an entire page explaining how Einstein’s GR (General Theory of Relativity) is a ‘background independent theory’, which, in effect, means that it’s not dependent on a specific co-ordinate system. But within her discussion, she makes this point about the Newtonian perspective:
 
The theory [GR] did share something with the Newtonian perspective: while space and time were no longer absolute, they remained a stage on which events unfolded.
 
Another ‘truth’ that carries over from Newton to Einstein is the inverse square law, which has a causal relationship with planets, ensuring their orbits remain stable over astronomical time frames.
 
While Magee’s and Putnam’s discussion is ostensibly about the philosophy of science they mostly only talk about physics, which they acknowledge, and so have I. However, one should mention the theory of evolution (as they also do) because it demonstrates even better than the theory of gravitation, that science is a cumulative process. Everything we’ve learnt since Darwin’s and Wallace’s theory of natural selection has demonstrated that they were right, when it could have demonstrated they were wrong. And like Newton and Einstein, Darwin acknowledged the shortcomings in his theory – what he couldn’t explain.
 
But here’s the thing: in both cases, subsequent discoveries along with subsequent theories act like a filter, so what was true in a previous theory carries over and what was wrong is winnowed out. This is how I believe science works, which is distinct from Magee’s and Putnam’s account.
 
Putnam distinguishes between induction and deduction, pointing out that deduction can be done algorithmically on a computer while induction can’t. He emphasises at the start that induction along with empirical evidence is effectively the scientific method, but later he and Magee are almost dismissive of the scientific method, as if it’s past its use-by-date. This inference deserves closer analysis.
 
A dictionary definition of induction in this context is worth noting: the inference of a general law from particular instances. This is especially true in physics and has undoubtedly contributed to its success. Newton took the observation of an object falling on Earth and generalised it to include the entire solar system. He could only do this because of the work of Kepler who used the accurate observations of Tycho Brahe on the movements of the planets. Einstein then generalised the theory further, so that it was independent of any frame of reference or set of co-ordinates, as mentioned above.
 
The common thread that runs through all 3 of these iconoclasts (4 if you include Galileo) is mathematics. In fact, it was Galileo who famously said that if you want to read the book of nature, it is written in the language of mathematics (or words to that effect). A sentiment reiterated by Feynman (nearly 4 centuries later) in his book, The Character of Physical Law.
 
Einstein was arguably the first person who developed a theory based almost solely on mathematics before having it confirmed by observation, and a century later that has become such a common practice, it has led to a dilemma in physics. The reason that the scientific method is in crisis (if I can use that word) is because we can’t do the experiments to verify our theories, which is why the most ambitious theory in physics, string theory, has effectively stagnated for over a quarter of a century.
 
On the subject of mathematics and physics, Steven Weinberg was interviewed on Closer to Truth (posted last week), wherein he talks about the role of symmetry in elementary particle physics. It demonstrates how mathematics is intrinsic to physics at a fundamental level and integral to our comprehension.

 

Footnote: Sabine Hossenfelder, a theoretical physicist with her own YouTube channel (recommended) wrote a book, Lost in Math; How Beauty Leads Physics Astray (2018), where she effectively addresses the 'crisis' I refer to. In it, she interviews some of the smartest people in physics, including Steven Weinberg. She's also written her own book on philosophy, which is imminent. (Steven Weinberg passed away 23 July 2021)

Wednesday 12 January 2022

Space and time: still a mystery after all this (time?)

How’s that for a self-referential title, hence the question mark and parentheses. It highlights the fact that time is an everyday phenomenon that literally runs our lives and yet it remains one of the great mysteries of the Universe, still debated among philosophers and scientists. You may think that space is less of a mystery, yet it sparks debate as well, even without Einstein’s revelation that they are cosmologically entwined thanks to the constant speed of light, c.


The problem is with how do we categorise space and time. Are they entities, parameters, dimensions, metrics, mathematical constructions? Perhaps all of the above. I think we can safely say they are not physical objects, yet they determine the relationships between objects everywhere in the Universe, including those that we can’t perceive. In fact, some scientists would argue that time and space are all about relationships and nothing else, which I’ll return to later.

 

But let’s start with one obvious question, which was raised by Kant and still persists today, thanks to Donald Hoffman (refer my last post), and that is: are time and space simply constructs of the mind? To quote Kant from Critique of Pure Reason:

 

But this space and this time, and with them all appearances, are not in themselves things; they are nothing but representations and cannot exist outside our minds.

 

The problem with this viewpoint is that it’s readily believed by almost everyone that space and time existed for billions of years before any ‘mind’ arose in the Universe.

 

Another contentious point is to whether space is an ‘entity’ that ‘expands’ and ‘stretches’ as the Universes itself expands (which is not disputed). Viktor T Toth, a renowned expert on physics on Quora, argues very strongly that it doesn’t and what we witness is the ‘distance’ actually increasing between objects. Proponents against space expanding (like Toth) argue that the space within atoms doesn’t expand. My response is that the size of atoms is determined almost solely by Planck’s constant (h), for which there is no evidence that it changes with the universe’s expansion.

 

However, space can travel faster than light, which suggests it is an entity. This is not disputable, and it’s why there is a horizon to the observable universe (refer my post on the End of the Universe). It’s also why we can incorporate ‘inflation’ into the birth of the Universe. It also has ramifications for black holes, which I’ll come to later. According to Einstein’s theories of relativity, both space and time can change according to the observer and these changes are measurable. In other words, space and time are not ‘fixed’ and they are affected by gravity. In fact, Einstein’s famous formula for his general theory has the curvature of spacetime on one side and the momentum-energy tensor on the other side. In other words, spacetime is curved by energy/matter. To quote John Wheeler: “Spacetime tells matter how to move; matter tells spacetime how to curve.”

 

During this discussion, I’ll cite people who know a lot more than me, like Viktor T Toth and John Wheeler (already cited), even if I disagree with them. But I’m going to attempt the impossible: I’m going to argue ideas that I consider obvious, though not incontrovertible, and I will probably fail, since they will include black holes, quantum mechanics and relativity, all of which I don’t have as much knowledge as I would like. But bear with me, because it’s mostly just logic.

 

I want to point out, right at the start, that I’m not one of those people who think Einstein got it wrong, quite the contrary, but I will point out the limitations of his theory based on what we can actually observe. And that’s a good place to start. A common diagram used to visualise Einstein’s formulation of spacetime is the light cone going both forwards and backwards in time. If you are an observer at the centre of this cone you can only be affected by events from the past within the past light cone, and you can only affect events in the future within the future light cone. Everything else outside these cones can’t be observed or have a causal relationship with you, and this is what I mean when I say relativity has limitations because they are real limitations. Sometimes people will tilt the cones over, indicating movement on your part and the horizontal plane, called the 'hypersurface present', also tilts over. However, there is no causal connection along that 'hypersurface' (through spacetime), according to what I’ve just described.



But this brings one to the subject of simultaneity, because Einstein showed with his famous train and platform thought experiment that 2 observers in different frames of reference could observe different sequences of the same event or perceive a difference in what occurs simultaneously.

 

This is a video that explains this better than I can, including the mathematics involved. Two things worth mentioning: the lecturer includes the spatial Lorenz contraction as well as the time dilation in his calculations; and the observer in the same frame of reference as the source of light sees zero difference and therefore observes a ‘true simultaneity’, though no one calls it that. I’ve long argued that the ‘other observer’ who doesn’t see the simultaneity, observes a difference in the Doppler effect caused by the ‘moving’ frame of reference with the moving light source, which should tell that observer that their observation is incorrect. The Doppler effect tells the observer if the light source is in their frame of reference or a frame of reference moving relative to them. It’s the Doppler effect that tells us that the Universe is expanding uniformly in all directions – it has no centre. It also tells us that we’re moving relative to the CMBR (cosmic microwave background radiation). In other words, we can measure our ‘velocity’ relative to the whole of spacetime, which, of course, is the Universe.

 

I’ve explained elsewhere how different observers in different parts of the Universe literally see different ‘now(s)’. They can literally see events occurring in opposite sequences, as a consequence of the finite speed of light, even without relativistic effects. However, if the events have a causal relationship, then all observers will see them in the same sequence. But this also means that my present will be seen in another observer’s past in their future, but it doesn’t mean the converse: that their future can be seen in my present. In fact, the relationship is reciprocal because I will see their past in my present. Observers can only see another observer’s past, no matter where they are. No observer can see another observer’s future. 

 

To give an example, a hypothetical observer in the Small Magellanic Cloud would see us 210,000 years ago when we were just emerging from Africa. Likewise, we would observe them 210,000 years ago (relative to us) if that was physically possible. Therefore, I don’t hold to the widely held view that we can theoretically see another observer’s future (due to the tilting 'hypersurface' plane in the light cone graphic), which infers that the future must already exist for everyone.

 

We know from the twin paradox thought experiment, as well as data from orbiting satellites, that clocks do literally run at different rates due to gravity as well as motion (your satnav depends on making corrections). Also, the famous muon observations arriving on the Earth’s surface. So both special and general theories of relativity change the rate of time, yet when the clocks are back in the same reference frame, they will show a different time duration while agreeing on where they are in the spacetime co-ordinates of the solar system. In other words, they don’t exist in different ‘now(s)’ just because they measured different durations to arrive at the same destination.

 

We know that different animals see time ‘flow’ at different rates. Many birds and insects see the world in slow-motion compared to us. This means they will see the hands of a clock literally moving slower while telling the same time. As Paul Davies has pointed out, if time was to slow down or speed up, you wouldn’t notice. But you can notice if you compare clocks in relativity. My point is that ‘now’ doesn’t change for these creatures even though they perceive time flowing at a different rate to us.

 

Well, I contend the same is true on a cosmic scale. If you were to go near the event horizon of a black hole, like in the movie, Interstellar, time would slow down for you compared to everyone back on Earth, even though you wouldn’t notice it. My argument is that this is no different, perceptually, to the bird observing time going slower. If you were to use the Doppler effect of receding galaxies as a clock, they would actually appear to be going faster (assuming you could take accurate enough measurements) compared to what Earthlings observed, and when you returned, you would agree on what ‘now’ is, compared to these distant cosmic clocks, though you would be considerably younger than your counterparts, if they were still alive, but more likely you would be meeting their subsequent generations.

 

And this is true even on Earth, where clocks run infinitesimally faster on mountaintops compared to sea level. But you don’t see an accumulated difference in ‘now’ over millions of years of the Earth’s rotation. All the while, the clocks are in the same ‘present’ while they are measuring different rates of time passing.

 

Carlo Rovelli gave a talk at the Royal Institute on ‘time’, where he argues that there is no ‘universal time’. But during the 15min question time (shown in another video), he contends that we arrive at a cosmic time for the Universe by taking an ‘average’. Brian Greene, in his book, The Fabric of the Universe, said something similar. However, if you lived on a planet orbiting near a black hole, surely the age of the Universe would be much less than what we observe, because any clock would be measuring time passing at a much slower rate than what we measure on Earth. Like the clocks on top of the mountains on Earth, I don’t believe hypothetical observers orbiting close to a black hole, perceive a ‘now’ that progressively gets out of step with the ‘now’ Earthlings observe over the course of their lives in the Universe, even if they measured a different age. In other words, I contend that you can have a universal now for the whole universe even if different clocks measure different rates of time dependent on where they are located.

 

Another video, which is an interview with loop quantum gravity theorist, Lee Smolin, describes time and space as being separate, which is both heretical and interesting. I think he has a point when you consider that, on a cosmic scale, time is finite and space is possibly infinite. Space could also be finite but perceptually infinite, like a hyperbolic universe, but, as Marcus du Sautoy pointed out in his book, What We Cannot Know, if the Universe is truly spatially infinite, we might never know. Smolin conjectures that space could be a consequence of ‘causal relationships’ between physical objects, which he doesn’t elaborate on, but which I find difficult to conceptualise. Causation is determined by the speed of light, otherwise everything would happen at once (Caspar Henderson, A New Map of Wonders). Smolin also contends that time might be an ‘emergent’ property (also without elaborating). The point is that causality requires time axiomatically. The thing about both space and time is that they are dimensions and if you add light (c) into the mix, you get a 4-dimensional universe that is fundamental for it to function in the way it does. With more than 3 spatial dimensions, planets would not have stable orbits, and if there was more than 1 dimension of time you would get time loops. If you have 2 spatial dimensions you would literally fall apart. Also, more than 3 spatial dimensions causes light waves to travel inconsistently. Our universe has the ideal time-space dimensional combination for its goldilocks existence.

 

In the same video, Smolin explains how the event horizon of a black hole breaks causality. This can be seen mathematically by Schwarzchild’s equation for a static black hole, which is described in this video. As the presenter explains, the +ve and -ve signs of the equation change when you cross the event horizon, which breaks causality. Causality is caused by the space dimension being less than the (negative) time dimension, and they are reversed on the other side of the event horizon (watch the video). It should be pointed out that Einstein was initially sceptical about the existence of black holes, even though Schwarzchild derived his equation from Einstein’s tensor.

 

There is a paradox inherent in a black hole (more than one, actually) but the most fundamental one is that time theoretically stops at the event horizon because time is related to light, and light can’t escape a black hole by definition. Viktor T Toth says that ‘the event horizon is always in an observer’s future’, so how can anyone (or anything) fall into a black hole? In a previous post, I speculated that maybe ‘space’ itself ‘falls’ into the black hole and that’s exactly what the guy in the video says. This is only possible because space can travel faster than light, as I described earlier.

 

This is already a lengthy post but I can’t talk about time without mentioning quantum mechanics. The same guy (who talks about black holes), gives a very good summary explanation of Richard Feynman’s path integral formulation of QED (quantum electrodynamics) in this video. It should be pointed out that Julian Schwinger’s ‘field’ interpretation called QFT (quantum field theory) is now more popular, if that’s the right word. In QFT, particles are seen as ‘excitations’ of a quantum field which is everywhere in the Universe. Someone on Quora even suggested that the word ‘particle’ should be erased from every physics text book, because they just don’t exist. Curiously, Feynman, in his book, QED, argued that everything is ‘particles’, but that was in the context of whether quantum phenomena are ‘waves’ or ‘particles’ in the Bohr tradition. I like Freeman Dyson’s view that it depends on whether an event is in an observer’s future or past, but I’m getting ahead of myself.

 

A good place to start with QM is Schrodinger’s equation. Carlo Rovelli, whom I cited earlier, in one of his books, is almost dismissive of Schrodinger’s equation and argues that the wave function (ψ) has misled us in our understanding of QM. But Schrodinger’s wave function is the basis of Feynman’s QED, so that’s where I’ll start.

 

Schrodinger’s equation encapsulates all the characteristics of QM which make it weird: superposition, entanglement and the uncertainty principle. The wave function also incorporates time-reversal symmetry, which is an inherent feature of QM. It doesn’t incorporate relativity, but I’ll come to that later.

 

The thing about Schrodinger’s equation, which is rarely mentioned, is that it describes the future – it makes predictions about where something will be in time. It was Dirac who derived the Lagrangian for QM, and Feynman adopted that for his ‘sum over histories’ or ‘path integral’ formulation, because it calculates the path of ‘least action’, which dictates what something does. (This also applies in a gravitational field, by the way, but I don’t want to confuse you.) Feynman used the proper time (τ) in place of t (that Schrodinger used) which automatically allows for special relativity (as explained in the video).

 

As someone on Quora once explained (David Moore, who is a Sydney based GP), a probability of ONE exists in the past, after the event. In the future, the probability is always less than one. This is what happens when the wave function ‘collapses’, for want of a better word, and neatly incorporates Freeman Dyson’s view that QM describes the future while classical physics describes the past. Feynman’s formulation has an infinity of possible future paths, that he integrates (hence the ‘integral’ in path integral) and also gives the path of least action. There is an element of teleology in this, but I don’t believe it makes the universe deterministic, though others disagree. On a large enough scale, as Schrodinger himself pointed out, you get a statistical deterministic effect, which he coined ‘statistico-deterministic’. But it can’t predict individual events, like when a radioactive isotope will decay, which is the crucial component in his eponymous cat thought experiment.

 

In regard to photons being the ‘particle’ nature of light, Mark John Fernee (physicist at Queensland University and regular Quora contributor) made the point in one of his posts, that if we didn’t observe light as photons, we would not be able to see many of the distant stars that we do. If light was purely a wave, then it would be so dispersed over the massive sphere of its influence it would be too faint to see. But, as a photon, it can arrive in just one point in space, where we happen to observe it.

 

I will leave the last word to Paul Davies. Even though he’s talking about QM in reference to black holes and Hawking radiation, the principle he describes is universal.

 

The very act of measurement breaks the time symmetry of quantum mechanics in a process sometimes described as the collapse of the wave function... the rewind button is destroyed as soon as that measurement is made.



Addendum: This video gives a more detailed and accurate explanation of black holes. It's more complex than my exposition would suggest.