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2 hours ago, K^2 said:

Earth's atmosphere is rotating significantly faster than Venus'. We just don't call that wind, because ground rotates at the same speed.

Venus' atmosphere super-rotates, but due to high density and viscosity of lower layers, any effect from difference in rotation speed between ground and atmosphere is completely nullified a few kilometers off the surface. The ground might as well not be there as far as upper atmosphere is concerned, and so the absolute wind speed is completely irrelevant.

On Earth, we're used to high turbulence, shear, and wind gusts to come with high wind speeds, because there is interaction with static terrain as well as temperature variations across it. Even on global weather scale, mountains and shapes of continents make an impact on how weather systems develop. You don't have any of that on Venus. The atmosphere is opaque, so the heat energy received by atmosphere is exceptionally uniform, and mountains are all lost in that thick, viscous part of the atmosphere, so they make absolutely no impact. The "weather" in upper Venusian atmosphere is exceptionally "calm". There is very little shear, turbulence, or gusts. Movement of atmosphere tends to be very uniform over large distances.

There's still a huge challenge in docking at hypersonic speeds. And I don't know enough about hypersonic aerodynamics to say how doable that is. Naively, I want to say that if you're catching up from behind, you should be inside the shock cones, and so it shouldn't be fundamentally different from same maneuver at subsonic speeds, but I'm not certain.

If that's not feasible, you'd have to drop speeds to subsonic and do docking the same way the in-air refueling is done. A slower start will mean extra fuel requirements, and then this might not work as an SSTO. I still think recovery vehicle should be a space plane even if it has to be staged, but it would certainly mean your recovery vehicle is larger and payload you can retrieve is smaller, which is a shame. But in any case, the absolute speed of wind with respect to terrain isn't going to matter. Conditions are going to be much better than they would have been on Earth at similar pressure altitude. The only thing that matters is how fast you're moving through local atmosphere during the docking.

"There's still a huge challenge in docking at hypersonic speeds", yes its called anti ballistic weapons who is very hard and interceptor and target get destroyed if it works because of the energy in the encounter :)
So you need to slow down, SSTO is off the table anyway I say. 
 

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5 hours ago, magnemoe said:

So you need to slow down, SSTO is off the table anyway I say. 

Fair! In that case, might even be possible to pull off a brief hover, and then the sample return can be entirely passive. (Edit: I mean, the part that returns to upper atmosphere from the lander.)

Edited by K^2
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With several space-faring nations and companies now regularly throwing rocks into LEO and other parts of the surrounding area... is there any agency deconflicting orbits between and among all the actors?

Also, how does this work when say 'Sekret Grup' from Country Zed wants to throw its intel gathering spycraft into orbit?  I know that we, and others routinely try to track and plot their launches... but is there any prior deconflicting?  (Or is it an extension of the 'big sky, little bullet' philosophy?)

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6 hours ago, JoeSchmuckatelli said:

With several space-faring nations and companies now regularly throwing rocks into LEO and other parts of the surrounding area... is there any agency deconflicting orbits between and among all the actors?

Also, how does this work when say 'Sekret Grup' from Country Zed wants to throw its intel gathering spycraft into orbit?  I know that we, and others routinely try to track and plot their launches... but is there any prior deconflicting?  (Or is it an extension of the 'big sky, little bullet' philosophy?)

You can't exactly put something into orbit quietly, so overwhelming majority of objects in LEO are tracked. There's always a chance of some forgotten derelict or a spook sat that quietly moved to another orbit and nobody noticed, but there's also a chance of a random rock just flying by. Generally, whoever does the launch will try to pick an orbit that's less likely to collide with anything. But that's no guarantee. And every nation that does launches, and probably a few that don't, basically just try to watch everything and notify whomever it concerns if there's a likely collision. Sometimes, one or the other satellite can be moved. Sometimes they just get to cross their fingers and watch. And collisions still happen, but yeah, they're extremely rare. Even birthday paradox can only do so much when there's so much space even in just LEO.

Edit: There might have actually only been the one satellite-satellite collision. Though, there have been debris strikes before. 2009 collision.

Edited by K^2
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A bit of esoterica for this 200th page: are physicists (or you, dear reader) more likely to believe in hard determinism or randomness in the processes that result in the universe we see today? 

 

Disclosure - this arises from a discussion relating to this article ( https://www.sciencealert.com/a-physicist-has-worked-out-the-math-that-makes-paradox-free-time-travel-plausible) about paradox - free time travel being possible. 

 

One guy  argued:


A chain of cause and effect reach back to the origin of time, space, mass, and reality itself. This enforces hard determinism.
... 

It can be seen that all proper causes have a proper effect, within chemistry and physics, as well as in life.
Even ideas like quantum observer concepts can likely be traced to mundane cause and effect at its lowest level.

The only way to defy determinism is to have improper causes or improper effects occur.
This is generally called, "magic."
 
 
 
 
To which I countered: 'Research showing that exceptionally complex systems can arise from a few very simple rules allows for randomness - and this explanation is more likely than the existence of some over-arching complex equation that describes what was, is and ever will be
 
Thoughts? 
 
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1 hour ago, JoeSchmuckatelli said:

A bit of esoterica for this 200th page: are physicists (or you, dear reader) more likely to believe in hard determinism or randomness in the processes that result in the universe we see today? 

There is  *lot* of randomness out there.

If you make 10,000 hard drives that are all virtually identical, you still have a 'mean time before failure' instead of an 'expected expiration date'

In our macroscopic world, we *think* things are deterministic because we only work with things at a relatively huge scale compared to the individual components(atoms).

At CERN(arguably one of the most advanced research facilities in the world) they use statistics to try and determine what actually happened when smashing together atoms at a large fraction of the speed of light, and they repeat the process a large number of times(hundreds of millions of times per second) to collect data on events that may happen with a low probability.

 ref: https://home.cern/science/computing/processing-what-record

The nuclear weak force, which I believe is the second strongest of the four, can only be predicted in a statistical way( the 'Half Life' is how long it takes half of a material to decay into something else.  You have no way of knowing if a specific atom will decay or not, just how long it will last 'on average').

Unless you can predict when each and every atom will decay, you cannot really say that you have a fully deterministic system, just that you have a statistically deterministic system. 

 

And that is without even getting into wonky stuff like quantum mechanics, where it is perfectly reasonable, and some times even expected, for a particle to move from point A to point B without crossing the intervening distance, Either because of energy levels(electron orbits), or because you don't really know exactly where the particle is, and even if it started out on one side of an impermeable barrier, if it's probability function includes points on the far side of that barrier, it might just end up on the far side of that barrier(without penetrating it).

 

'Determinism' seems to be something that can only be really believed by people who don't look too closely at how the universe works...

Edited by Terwin
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I follow the multiverse way.

The universe is a simultaneous superposition of its possible states, so there is no "future", "past", "randomness", "cause", and "effect", as well as "time machine paradox" and so on.
There is a fractal hologram, and all those terms just decribe various possible ways of a sunbunny moving along/across it.

It's deterministic with technically infinite number of possible states, so it's technically not deterministic.

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2 hours ago, JoeSchmuckatelli said:

A bit of esoterica for this 200th page: are physicists (or you, dear reader) more likely to believe in hard determinism or randomness in the processes that result in the universe we see today? 

Every test we've done shows physics to be entirely deterministic. Yes, even quantum events. Any time you observe a "random" outcome, it's just a side effect of you having partial knowledge about the system state. In case of classical "randomness," like a coin flip, that's an uncontroversial statement. In cases of quantum randomness, it requires a bit more interpretation, but the bottom line is that you need an observer with partial information and a system to observe before you get anything like "random" outcomes. If you describe that interaction as a complete system, all random outcomes go away, and you have a purely deterministic system. It's only when you start describing the observations an inherently limited observer is making that randomness comes into play. In ironic twist, perhaps, is that in classical theory, a random outcome is when you discover something you didn't previously know about the system. In quantum mechanics, you get a random outcome when you failed to learn something about the system.

The net outcome is the same though. The universe is entirely deterministic and essentially a fixed structure in time. We're just too insignificant to appreciate it, looking at the most minute portion of the universe, and thinking that it seems kind of random.

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27 minutes ago, K^2 said:

Every test we've done shows physics to be entirely deterministic. Yes, even quantum events. Any time you observe a "random" outcome, it's just a side effect of you having partial knowledge about the system state. In case of classical "randomness," like a coin flip, that's an uncontroversial statement. In cases of quantum randomness, it requires a bit more interpretation, but the bottom line is that you need an observer with partial information and a system to observe before you get anything like "random" outcomes. If you describe that interaction as a complete system, all random outcomes go away, and you have a purely deterministic system. It's only when you start describing the observations an inherently limited observer is making that randomness comes into play. In ironic twist, perhaps, is that in classical theory, a random outcome is when you discover something you didn't previously know about the system. In quantum mechanics, you get a random outcome when you failed to learn something about the system.

The net outcome is the same though. The universe is entirely deterministic and essentially a fixed structure in time. We're just too insignificant to appreciate it, looking at the most minute portion of the universe, and thinking that it seems kind of random.

A agree if you know the position and the vector of an electron with high enough accuracy you can determine if it cross the gate of an FET transistor or not. 
Knowing that is the challenge, first you have to disprove Heisenberg uncertainty principle, then you have to do this in practice. 

Rest is theology as in is the universe deterministic or not. Its theology as we can 1) neither prove or disprove it using know physic. 2) its totally irrelevant unless we can predict it to some degree. 
Worse you also has macro effects like the butterfly effect, in an chaotic system any trivial change will have large effect over time. 

Now the main issue with theology and determinism is: That is the point? Why simulate or create an something you knew the outcome off. 

I see this more as the bias of the writer. I don't like randomness so I say its an unknown underlying layer below quantum mechanic who is deterministic.
 

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20 minutes ago, magnemoe said:

Rest is theology as in is the universe deterministic or not. Its theology as we can 1) neither prove or disprove it using know physic. 2) its totally irrelevant unless we can predict it to some degree. 

Nonsense. By that metric gravity is theology. You can't prove that there isn't a deity that's holding everyone to the ground and bends light as it passes stars, therefore, any claims that gravity is due to general relativity is religion!

That's not how science works. We actually have a body of work on randomness of physics. We've tested the hidden variable theory and found it to be bogus. We've tested quantum mechanics and found it to be valid. We can draw conclusions based on it.

23 minutes ago, magnemoe said:

A agree if you know the position and the vector of an electron with high enough accuracy you can determine if it cross the gate of an FET transistor or not. 
Knowing that is the challenge, first you have to disprove Heisenberg uncertainty principle, then you have to do this in practice. 

And that's not how uncertainty principle works. It's not about inability of you to know the momentum and position, it's about the fact that you can't have electron in a state where both are eigen states of the respective operators. An electron in a certain position has a spectrum of momenta and vice versa. And that goes back to the fact that there are no hidden variabl.es. It's part of why quantum mechanics is fully deterministic.

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@K^2

Does knowledge of a deterministic structure in the quanta necessarily translate into a finding that the macro universe must be deterministic as well? 

 

(This asked in relation to the concept that hugely complex systems can evolve from simple rules: I fail to see a connection between knowing the position of the elements of the system at Point A in time and space allows you the certainty of how the system will evolve way down the line... You reference imperfect understanding... But would perfect understanding of such a system not merely give you a range of probability for what will develop at Point W?) 

Edited by JoeSchmuckatelli
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17 minutes ago, JoeSchmuckatelli said:

This asked in relation to the concept that hugely complex systems can evolve from simple rules: I fail to see a connection between knowing the position of the elements of the system at Point A in time and space allows you the certainty of how the system will evolve way down the line... You reference imperfect understanding... But would perfect understanding of such a system not merely give you a range of probability for what will develop at Point W?

No. Complexity doesn't lead to uncertainty. If you can examine every little element and predict the outcome, then given enough time, you can go over everything and predict the outcome for the total system. Granted, it's a practical impossibility, which is why concept of chaos exists, but it doesn't make the system indeterminate.

Between the chaos and quantum mechanics, though, I can be pretty bold about making claims about determinism of the universe, and still, I'm going to come up completely dry if you ask me about free will. I think, a lot of people conflate the two, but they are orthogonal concepts. Yes, in the grand scheme of things of all of the universe, none of your choices matter. But you can probably guess that without a degree in physics. On the other hand, you make decisions based on partial knowledge of the universe around you, and choices you make influence what changes you will observe in the universe. And that might sound like a bit of a solipsist view, but as you can't really experience universe from perspective of another person, that's all you really have to go on to judge your impact on the universe, and from that perspective, your actions and consequences are entirely a matter of your own choice. That's a far cry from definitive, "Yes, people have free will," but it's also a resounding "maybe" in a context of the universe as a whole being fully predetermined, and that's kind of amazing.

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26 minutes ago, K^2 said:

Nonsense. By that metric gravity is theology. You can't prove that there isn't a deity that's holding everyone to the ground and bends light as it passes stars, therefore, any claims that gravity is due to general relativity is religion!

That's not how science works. We actually have a body of work on randomness of physics. We've tested the hidden variable theory and found it to be bogus. We've tested quantum mechanics and found it to be valid. We can draw conclusions based on it.

And that's not how uncertainty principle works. It's not about inability of you to know the momentum and position, it's about the fact that you can't have electron in a state where both are eigen states of the respective operators. An electron in a certain position has a spectrum of momenta and vice versa. And that goes back to the fact that there are no hidden variabl.es. It's part of why quantum mechanics is fully deterministic.

Don't understand might misunderstood you first statement. 

Quantum mechanics is fully deterministic as in we know the probabilities.
Newer heard once before. Kind of Vasa was the larges warship in Sweden until she sunk, yes it was days from launch and a hour something from maiden voyage but true :) 

But still I say that in an deterministic universe you know if the cat is dead or alive. Yes all who owned cats know it escaped.

Who brings up free will, again this is extremely chaotic with lots of feedback effects. How chaotic? Well an insane amount has gone into researching marketing campaigns and products who was legendary flops. And if you could predict the stock marked 5% better than average and had some millions you would be the worlds riches in a year. 

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18 minutes ago, K^2 said:

No. Complexity doesn't lead to uncertainty. If you can examine every little element and predict the outcome, then given enough time, you can go over everything and predict the outcome for the total system. Granted, it's a practical impossibility, which is why concept of chaos exists, but it doesn't make the system indeterminate.

Between the chaos and quantum mechanics, though, I can be pretty bold about making claims about determinism of the universe, and still, I'm going to come up completely dry if you ask me about free will. I think, a lot of people conflate the two, but they are orthogonal concepts. Yes, in the grand scheme of things of all of the universe, none of your choices matter. But you can probably guess that without a degree in physics. On the other hand, you make decisions based on partial knowledge of the universe around you, and choices you make influence what changes you will observe in the universe. And that might sound like a bit of a solipsist view, but as you can't really experience universe from perspective of another person, that's all you really have to go on to judge your impact on the universe, and from that perspective, your actions and consequences are entirely a matter of your own choice. That's a far cry from definitive, "Yes, people have free will," but it's also a resounding "maybe" in a context of the universe as a whole being fully predetermined, and that's kind of amazing.

Heh - I've tried, here, to phrase the question to avoid delving into how or whether free will relates to the question.  In the other, we got to Allah and 'magic' in about two steps. 

I still feel like there is room to quibble with what you write above.  Certainly, if you start with knowing what's going on at Spacetime Point A and follow sequentially through each step between it and Point W, you would say that the system had to develop the way it did... Because that is how it developed. 

But I think @Terwinbrings up an interesting point - something like decay where there is no guarantee of the particle decaying at the second averaged by its fellows, how can we say that knowing Point A is deterministic rather than probabilistic?

If the answer is that 'perfect knowledge' of what's going on at Point A incorporates knowledge of exactly when the particle will decay... I might argue that 'perfect knowledge' in that case would require Allah to comprehend (because you would also, then, have to know not only when that particle would decay, but also the instant of decay of particles not yet in existence) 

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23 minutes ago, magnemoe said:

Quantum mechanics is fully deterministic as in we know the probabilities.

No, quantum mechanics is deterministic in that we know the outcomes. Yes, that's not how they teach it in school. You also don't learn group theory when you learn algebra in school.

The only point at which probabilities enter into the picture is when you start interpreting observations made by an observer that is part of the system. And while there are some questions about that in regards to Copenhagen Interpretation, we do have theorems showing equivalence of interpretations, so you can take any interpretation you like that doesn't have that problem, like Many Worlds. Further, quantum mechanics conserves entropy, and you can't have that with any random chance outcomes. Of course, so does classical mechanics (also deterministic) and here we'd have to start talking about entropy grain... Point is, random chances and probabilities aren't actually a feature of quantum mechanics, despite what many popular or school explanations often say.

28 minutes ago, JoeSchmuckatelli said:

Heh - I've tried, here, to phrase the question to avoid delving into how or whether free will relates to the question.

Yeah, but it's kind of an unavoidable discussion. It's the main reason why people are hesitant to embrace determinism, so I have to say a few words about it.

31 minutes ago, JoeSchmuckatelli said:

something like decay where there is no guarantee of the particle decaying at the second

That's not how decay works, though. A particle doesn't just sit in excited state, then suddenly decides to decay. The physical process of decay is gradual transition of particle from it's excited to its decayed state. You just can't observe a superposition. It's Schrodinger's cat all over again.

This is the most crucial thing to understand here. The biggest mistake in how quantum mechanics is popularized is right there in the name. Nothing is actually quantized. Nothing is actually discrete. All quantum processes and all physical quantities are inherently continuous. The things that are discrete are the eigen states of measurement operators, which is purely a mathematical quirk.

In chemistry class, they tell you that an atom can only absorb a photon of exactly the right wavelength and in the exact quantum of energy, and that the electron will instantly jump to a new energy state. But that's such a bad oversimplification, it might as well be a lie. If you spend some time studying Magnetic Resonsance, for example, you'll quickly learn that a short pulse at roughly the right frequency will get the system part of the way to excited state. What does it look like for an atom that absorbed a portion of the energy required for transition? Well, it's a superposition of the orbital states you learn in the chemistry class, which are nothing but eigen states of the energy operator. If this wasn't the case, photons with the "wrong" energy wouldn't interact at all, and then glass wouldn't be refractive. The reason glass has index of refraction is because there are atoms whose absorption spectra are near visible light, and they absorb and re-emit light as it passes through the medium. If an atom would be unable to absorb a portion of a photon with the wrong energy, glass would be visually indistinguishable from vacuum.

An atom in a half-excited state has half the energy required for a single photon of a given frequency, and it will emit that energy over time as an electromagnetic wave with half the total intensity, and if that wave encounters a detector, that detector itself will be taken into a superposition state. And if a scientist takes the measurement from the detector, that scientist is now in a superposition state. There's a big question of how far down the chain you should care. The idea of decoherence, much like idea of coarse-grained entropy, lets you cut this chain and just start treating the picture classically. If you chose to interpret experiment in such a way, then you would compute probabilities, but it's an interpretation choice to substitute one unknown with another that results in a probabilistic outcome and not anything in the underlying physics. The other choice is to keep it Many Worlds, and then there are no probabilities. Just two timelines with their own outcomes. Either way, the system's entirely deterministic.

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Quick question (as I formulate my response); Is it fair to say that a particle has three states:

  • Undecayed (which gives no information about when it will decay)
  • Decaying (which gives information about the rate and progress), and
  • Decayed (which gives no information about when it decayed?

 

 

(Or am I fully exposing ignorance by even asking the question???)

4 hours ago, K^2 said:

That's not how decay works, though. A particle doesn't just sit in excited state, then suddenly decides to decay. The physical process of decay is gradual transition of particle from it's excited to its decayed state. You just can't observe a superposition. It's Schrodinger's cat all over again.

 

Can't seem to edit these correctly; Your response, quoted above, suggests the answer to my question is 'no'.  I just want to be sure.

Edited by JoeSchmuckatelli
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46 minutes ago, JoeSchmuckatelli said:

Quick question (as I formulate my response); Is it fair to say that a particle has three states:

The "decaying" isn't really a separate state. It's a superposition of decayed and undecayed. So there's really only two. Well, in general, there can be a lot more, like, there can be different decay modes, and so on. But if we're trying to keep it simple, there are only two that you care about within the context. And the system is technically always in some sort of a superposition of these two states. But over time, the amplitude of the decayed state is increasing and undecayed decreasing.

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9 hours ago, K^2 said:

The "decaying" isn't really a separate state. It's a superposition of decayed and undecayed. So there's really only two. Well, in general, there can be a lot more, like, there can be different decay modes, and so on. But if we're trying to keep it simple, there are only two that you care about within the context. And the system is technically always in some sort of a superposition of these two states. But over time, the amplitude of the decayed state is increasing and undecayed decreasing.

So you are saying that we now have the equipment to look at an undecayed atom and predict exactly when it will decay, or at least a design that was used to do this successfully in the past, correct?

Or is this all still theoretical?

(I may not be the most attentive to scientific forums, but at the very least I would have expected to hear about radioactive decay no longer being a sufficiently entropic randomness source for strong encryption)

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11 minutes ago, SOXBLOX said:

So, the universe IS deterministic? Awesome! I hated the concept of randomness.

It is. Like a 1000-page table of pseudorandom numbers with unnumbered pages.

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8 minutes ago, JoeSchmuckatelli said:

If you flung the pages off a cliff, would you have a cascade of entropy? 

If the pages code the information about the pages positions relative to the cliff, no.

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