Born to Do Math 188 – “A physicist is just an atom’s way of looking at itself.”
Author(s): Scott Douglas Jacobsen and Rick Rosner
Publication (Outlet/Website): Born To Do Math
Publication Date (yyyy/mm/dd): 2020/10/08
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Scott Douglas Jacobsen: So, we were talking off-tape about the arrow of time and physics.
Rick Rosner: So, the physics that I know has always had a problem with the arrow of time. The physical interactions, e.g., particles smashing into each other, the stuff that contains few enough particles that you’re not dealing with statistical, thermodynamic phenomena. The stuff that is reversible. It is something that physics has dwelled on it. People who do physics have not paid much attention to it because they have their own physics to do. It is that the universe is not reversible. The stuff happening to us has a definite time arrow. The individual physical interactions as dictated by the rules of physics seem not to. You can run everything backwards.
If you could run a film of a cup running backwards exploding, there’d be nothing in the backward film breaking the laws of physics. It would regain its kinetic energy and use that energy to come back together and jump back onto the table and come together. Between the kinetic energy of the parts of the cup and the floor, nothing would be disallowed by running the film backwards. But we’ve talked. I think the arrow of time is determined by large-scale physical interactions.
That is, the photons that make it to the surface of the Sun, the vast majority, go for billions of lightyears and lose most of their energy to the curvature of space, which is, I believe, a tacit exchange of information. That large-scale transmission of energy across billions of lightyears is what propels the arrow of time. Because when you have a gazillion of photons and neutrinos sharing information that way, none of those long-distance photons are doing anything that can be time reversed. They are spreading their information across the skyn of relationships in the universe in an irreversible way.
That’s not a local thing. Like I said, if a photon gets out of the Sun, it’s not going to be local. I don’t know. I haven’t done the math. Somebody probably has; how many photons there are that travel a quadrillionth of a millimetre within the Sun before they get captured again? I guess the sheer number of photons that only travel a tiny distance would outnumber the photons that travel a huge distance.
If you consider each increment between each photon travelling from the center o the Sun to being captured, and if you consider that one interaction, then the number of those close interactions outnumbers the number of interactions with long-distance photons, maybe. It’s the long distance particles that shape the universe and determine the arrow of time. But there is another arrow of time under IC, and under quantum mechanics, which is, “What moments are allowed to follow each other?”
The deal is, under quantum mechanics, there is the universe – or whatever system you’re looking at – contains a lot of open interactions, open positions, where something is due to happen at some point in the future. That thing that can happen can have a number of different outcomes. There’s a reaction that sets a neutron loose. A free neutron lasts for 10 or 11 minutes before decaying on average. So, the decay of that free neutron is like an open proposition. You don’t know when.
Because there is no way under the rules of quantum mechanics to predict exactly when it is going to decay and when the various energies of the products of the decay… the amount of energy has to stay the same. But how that energy is distributed among the particles that fly apart from a decayed neutron, those are all unpredictable things. There is a gazillion of these open issues in each moment of the universe. But your subsequent moments of your universe or system have to follow the open positions and be consistent with the closed positions too – to the extent that there are closed positions.
It is probably a philosophical-quantum mechanical issue. Anyway, each candidate for next possible moment of the universe is going to be a member of the set of possible moments that close some of these open issues. That some of your possible next moments of the universe are going to have that neutron decaying from one moment and the next. That, itself, is an ironclad arrow of time. Of course, it still has the same issue; super local or micro interactions appear to be time reversible under the laws of quantum mechanics.
Neutrons can undecay too. Shit can come together and form a neutron without violating the rules of quantum mechanics, but, still, it is a macro, large-scale system-wide thing. The moments follow from each other. The open issues are closed in a sequence that follows the arrow of time. Partly what I am saying is that the super local apparent reversibility of physics is, maybe, like free will or dwelling on the wrong question. I think what needs further analysis besides everything is how the sequencing based on determining previously indeterminate quantum questions.
That is, we know in a moment when the neutron has decayed. We know it has decayed. Before it decayed, we didn’t know when. So, that open question has been closed. There should be interesting things about linking the closing of open questions and the large-scale loss of energy of long-distance particles. Those need to work together to determine the arrow of time. That’s a place to look to see how they relate to each other in some very obvious and, probably, in some not very obvious ways.
Then you want to relate that to thermodynamic systems, which are all embroiled in the arrow of time, too. So, that’s mostly it.
One issue that seems to arise or one principle that seems to arise is that when you’re looking at super local interactions that don’t have an arrow of time according to the rules of physics. According to Newtonian and traditional physics, under the rules of quantum mechanics, nothing is entirely local in quantum mechanics. Everything is tied to everything else. There is always a non-zero probability that a particle showing up in one place can show up way the fuck away just due to chance. There is quantum tunneling.
A particle confined in the box can appear outside the box because there is no way to completely confine a particle’s probability wave. It spreads across all of space. Where it is next detected within its own probability wave, which is anyplace, it could be anywhere with varying degrees of probability. It is always possible an electron bouncing around in a lead box can appear outside the lead box. So, quantum mechanics, in that way, is non-localized.
The arrow of time stuff appears to be tied to the universe as a whole. It is a non-local thing. There is a sense of that in the thermodynamic arrow of time. Statistically, it is much more likely the cup falls off the counter and smashed on the floor than the cup unsmashing on the floor and coming together on the counter. The unlikelihood requires a lot of atoms, 10^23rd or 10^25th atoms on the floor. It is a non-super-local interaction. Even though, it only involves the table top, the floor, and the cup.
It still involves a shitload of particles and a shitload of things implied by statistical likelihoods and unlikelihoods. It is not super local in this sense. It is not just one electron repelling another electron. When you look at the other stuff that seems to have an arrow of time, super long distance particles and the universe having all of these open questions that get solved sequentially with an arrow of time. There’s the strong implication that arrow of time is tied into the entire system.
That the entire system is tied into the entire system via the rules of quantum mechanics. It means everything is tied to everything else. Maybe, worrying about the irreversibility, the complete apparent reversibility, of super local, super discrete interactions – a few particles in small scales – is worrying about the wrong issues, instead, you want to worry about, “How about does a system with all these discrete particles tied together work?”
Of course, many of the answers are contained in quantum mechanics. Quantum mechanics needs to be tied to cosmology to get the rest of the answers out of it.
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