For Questions That Don't Merit Their Own Thread

[JoeSchmuckatelli]

12 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 if CERN created a particle that decays in a nanosecond, you are saying that at the moment of it's creation it came into existence as itself and its decayed state? The act of decay isn't an act of creation, then? 

So... 

Is U-238 also Lead-206... And every particle in between in superposition with one another, but merely awaiting the amplitude change? 

If so, that has some interesting implications. 

Edited February 9, 2021 by JoeSchmuckatelli

[K^2]

3 hours ago, Terwin said:

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)

Imagine that somebody started reading you off digits of pi from an arbitrary point. Is it fully deterministic? Yes. Is it a good source of random numbers? So long as you don't know the starting point, also yes. So here's the question. How long do you have to keep recording the numbers, before you know what part of the sequence they're being read from? Right.

When you perform a measurement, you entangle measurement device to the measured state, and that only gives you so much. But you can still do incredible things with that if you get creative. Now, I don't think we have fine enough control of transitions at relevant energies to do something like this with nuclear decay, but you can do this experiment with optical states or, better yet, nuclear spins in magnetic fields via magnetic resonance. If you have a nucleus with magnetic moment, you can place it in a magnetic field, and then have a spin down state with low energy and spin up with high energy. Moreover, you can interact with that spin in a number of ways, including exciting a spin down nucleus to a spin up state, then letting it decay. As always, if you want to measure a state, all you can tell is whether it's spin up or spin down, and not the exact superposition of the two. Another problem with nuclear decay is that it's an interaction with vacuum, which is always noisy. So you're not just getting randomness from quantum process, but also from environment. You can exclude that in NMR. Instead of just letting excited state decay naturally, you can have controlled demolition of sorts by coupling the nuclear spin of interest to another nuclear spin. That sets up a decay at a predictable rate as excitation is transferred from one nucleus to another. It's still a quantum decay, though. You can wait out the correct amount of time and have a prediction of probability of finding the atom in spin up or spin down state, but never the exact condition. That probably still sounds very random, but it's also where I'm going to kick it up a notch.

Quantum states can't be cloned, but they can be amplified. That is, you create a copy that is entangled to the original. You can make measurements on either one, and both copies collapse to the same state. But that's not wild enough for us here. Have another lab on another continent set up identical experiment. Have a satellite overhead that can send you entangled pairs. You start the process by exciting your spin of interest then let it decay for some pre-determined amount of time t₁. At that point, instead of making a measurement, you amplify the state to a copy, use an entangled pair from satellite to perform quantum teleportation of that "copy" to the other lab. Have them initialize their version of the experiment from that copy, wait out predetermined amount of time t₂ and then have either lab perform measurement of final state and the other lab confirm it. Repeat this all a bunch of time with different values for t₁ and t₂. Here are some exciting results you'll get. First of all, you will measure a distribution of up and down results that is identical to just letting the original system sit for time t = t₁ + t₂ regardless of which lab did the measurement. Moreover, the other lab will always agree. These are two independent decays on two continents that are providing you with consistent results. Which is something we've gotten used to with basic entanglement, but these are two independently decaying system.

If the decay between t₁ and t₂ was random, how can we expect the results between two labs to agree? Yes, the quantum states are synchronized at t₁, but then each one decays independently.

 

1 hour ago, JoeSchmuckatelli said:

Is U-238 also Lead-206... And every particle in between in superposition with one another, but merely awaiting the amplitude change? 

Matter is just an excited state of vacuum, so yeah, you can think of it that way.

Edited February 9, 2021 by K^2

[JoeSchmuckatelli]

...

And back to Determinism.  In another thread, the Determinist argued:

Quote

Now, if a person wanted to begin to challenge me scientifically, I would ask them for proof that randomness occurs.

And they will NEVER be able to deliver this proof because time only flows in one direction.
Do not look at me like someone can somehow can show me proof using a ~really good~ argument.

They will never be able to go back to an event and show me it occurring in a way it did not occur.

It is literally impossible to ever show proof of non-determinism. Serious proof. Powerful proof. Compelling proof.
There is plenty of proof that we lack understanding. But proof that things can have alternative outcomes, despite only one outcome ever actually occurring? It is a logical impossibility unless you have some sort of TIME MACHINE.

I get this.  You roll a 20 sided die, and it comes up 17.  Of course no other outcome was possible, because that is what occurred.  We can look back at a single timeline and agree that what has happened, happened.  Looking backward, our timeline is deterministic, not probabilistic.  What I don't necessarily agree with is that even during the moment when the die was being tossed that it was guaranteed to become a 17.  As I toss the die and it flies toward the table, it can come up with a number, any number or even no number (edge roll) constrained by the media.

I'm guessing the determinist would argue that if we knew the material properties of the die (composition, weight, friction, etc) the speed and spin of the throw and the properties of the table - heck even the time of day, temperature and relative humidity of the air, position of the Moon and Jupiter and whether a pair of neutron stars recently collapsed into a black hole (etc, etc, etc) that with all that data we could reduce or eliminate any uncertainty and know - absolutely - that this die will show a 9 when it stops spinning... 

I'm guessing the logical extension of this is that the universe is constrained by its existence and current state in a deterministic way that it cannot encompass random, unexpected occurrences (while we, with limited knowledge are allowed to be surprised by the unknown - and perceive that as 'random').  That the universe is what it is, and will be what it will be, because it is what it is.  Further, that for any truly random, unexpected thing to occur within the universe... that it would, by definition, have to come from outside the universe, which has some logical inconsistencies. "God does not play at dice" makes more sense, now.

The problem, for me, is that this view seems a bit smug.

To be true, you* would have to know (i.e. have observed) literally every thing. 

It's the Schrödinger Cat idea: in the box the cat is both dead and not dead... and once we reduce the variable to knowledge by testing / observation, looking backward it was clearly determined (especially from the moment of observation) - but for it to be forwardly determined seems like cheating - like eliminating the instance of 'now' as time flows.  To declare that our living in the now is an illusion.

It is the equivalent of declaring that we are actually living or factually repeating that which has already occurred.  Reading a novel that has already been written - of course it can't end any differently; the story arc was determined before we even picked up the book.

So, the problem for me is that the instant (or expanse) of time before the instant of now has to be indeterminate, and can be probabilistic regardless of how informed our predictions can possibly be... because within the universe, that instant before 'now' incorporates all of the possibilities that haven't been reduced to knowledge through having occurred.

 

 

 

*I don't mean to imply a sentient observer 'you' - the Universe could 'know' a thing that has happened, once it has happened, because it has happened.

.

[magnemoe]

1 hour ago, K^2 said:

Imagine that somebody started reading you off digits of pi from an arbitrary point. Is it fully deterministic? Yes. Is it a good source of random numbers? So long as you don't know the starting point, also yes. So here's the question. How long do you have to keep recording the numbers, before you know what part of the sequence they're being read from? Right.

Note that RNG() function used in software tend to work just like this, the fun part is that you can run this with an seed then you set up the random number generator. 
Normally the seed or starting point is selected somehow random in the computer like the millisecond of the time. 
However it let you get an list of random numbers who is also deterministic so if some other running the rnd with the same seed will get the same sequence, surface details on Mun in KSP is made this way.  Benefit is that its require no storage but is the same for all games.

[K^2]

3 minutes ago, magnemoe said:

Note that RNG() function used in software tend to work just like this, the fun part is that you can run this with an seed then you set up the random number generator. 

With caveat that RNG is a finite state machine. So you can always figure out where in the sequence you are in finite number of samples. With a good RNG that number is still impractically large, of course. Though, there have been cases of just a poor choice of RNG or one with intentional back door being used to spy on encrypted communication (The story behind Elliptical DRGB is some cyberpunk stuff), which is why quantum encryption is still a better option if you have access to it.

[mikegarrison]

On 2/8/2021 at 3:22 PM, K^2 said:

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.

What about, for instance, the Pauli exclusion principle? If that's valid, isn't an example of something that is discrete?

[K^2]

32 minutes ago, mikegarrison said:

What about, for instance, the Pauli exclusion principle? If that's valid, isn't an example of something that is discrete?

Not really. Think of fermions like twists on a tape. If you try to push two clockwise twists together, the more you push, the more they repel. So you can never pass one clockwise twist through another. Nor can you create two twists in the same exact space. But a clockwise and counter-clockwise twists will merge together, and you can use that to have a clockwise twist pass through counter-clockwise one. The way two fermions with opposite spin can pass through each other, while two fermions with the same spin can't is very similar.

Of course, real fermions exist in 3D space, have other conserved charges, and the spin space is a bit more complex than all that, but it still acts like a topological charge with Pauli exclusion as a consequence, so it's not a bad analogy to keep in mind overall, and it's exceptionally close to the actual math of fermionic fields, which is unusual for simple analogies in QM.

[ARS]

When long-duration space mission using probes are conducted (which can take years, such as Dawn mission). After setting the flight and orbit parameter of the probes' autopilot (when to do burn, how long the burn is conducted, craft orientation, hibernation mode, etc.), when the probes are on escape trajectory from earth's gravity well, does the mission control keep tracking the probe everyday for years until it reached the point for flight maneuver adjustment (such as when entering another celestial body's gravity well for gravity assist, maneuvering for rendezvous, etc.), or just do like what most KSP players did with ion engine burn? Estimate time for the next maneuver (which can take years) and go grab a lunch downstairs (or wait for years), come back when the time comes to do the maneuver?

[kerbiloid]

They press "Time warp".

***

Just the Dawn crew, including two Flight Operation teams:

https://solarsystem.nasa.gov/missions/dawn/mission/the-team/mission-teams/

(links are expandable).

They still need receiving the telemetry and run tests. Sometimes to fix bugs. In Voyagers they even updated software.

P.S.
Just think: in KSP we do all these people's work alone.
What a mighty game it is!

Edited February 10, 2021 by kerbiloid

[JoeSchmuckatelli]

6 hours ago, kerbiloid said:

Just think: in KSP we do all these people's work alone

That's because NASA is government funded.  There's always bloat in Gov't

[tater]

7 hours ago, kerbiloid said:

They press "Time warp".

Spoiler

 

 

[kerbiloid]

16 minutes ago, tater said:

They press "Time warp".

Remember, love, mourn...

Spoiler

 

 

 

 

 

 

Edited February 10, 2021 by kerbiloid

[JoeSchmuckatelli]

This is cool:  Alpha Centauri from New Horizons (left) and Earth (right).

TNKgS8X.jpg (3790×1952) (imgur.com)

Parallax, baybeee!

[JoeSchmuckatelli]

Anyone seen the 'estimated costs' for a static fire of engines?

 

I'm guessing it's 'worth it' in the long run to prove the systems work... but it can't be cheap

[wumpus]

12 hours ago, JoeSchmuckatelli said:

Anyone seen the 'estimated costs' for a static fire of engines?

 

I'm guessing it's 'worth it' in the long run to prove the systems work... but it can't be cheap

I suspect it is similar to the cost of a real launch, less the  cost of the rocket.  You don't have to worry about notice to airmen and such, but you also have to deal with a huge flame at ground level.  It looks like Spacex is going to need a few more (for reliable ignition of raptors).  How they are going to deal with the difference of plenty of air blasting up the nozzle (when they fail) vs. none on a static test is a bigger question.

[magnemoe]

1 hour ago, wumpus said:

I suspect it is similar to the cost of a real launch, less the  cost of the rocket.  You don't have to worry about notice to airmen and such, but you also have to deal with a huge flame at ground level.  It looks like Spacex is going to need a few more (for reliable ignition of raptors).  How they are going to deal with the difference of plenty of air blasting up the nozzle (when they fail) vs. none on a static test is a bigger question.

This, an static fire will work like an launch around the launch site but not downrange. 
Static fire of engines are another thing and cheaper if set up as you feed the engines from other types of tanks who are not weight constrained and you can put the engine in an pillbox setup in an location no complain about the noise. 

[RyanRising]

Obviously this can’t be the case for a multitude of reasons, but if the budget that went towards the SLS had instead just been a “make a good moon rocket” fund instead of a “keep the Shuttle contractors employed” fund, do we have any idea what that rocket might have looked like? Or is that idea too far divorced from reality for us to have any inkling what NASA could have come up with?

[JoeSchmuckatelli]

16 hours ago, RyanRising said:

Obviously this can’t be the case for a multitude of reasons, but if the budget that went towards the SLS had instead just been a “make a good moon rocket” fund instead of a “keep the Shuttle contractors employed” fund, do we have any idea what that rocket might have looked like? Or is that idea too far divorced from reality for us to have any inkling what NASA could have come up with?

Interesting question - the problem is with government is the desire to do too many things with the one thing (and build them in congressionally powerful districts).  Example: the USMC is still using amphibious tractors first used during Vietnam (yes, the same hulls) - we had an opportunity to get a new vehicle for the 21st century.  Mission creep killed it.  From what I've seen, SLS got hit with the same problem. 

NASA "We want a heavy lift rocket" 

Congress: "Cool, it needs to be able to go to the moon" 

".. . And Mars" 

"... And carry lots more people - make it wider" 

"... And go to the ISS" 

"Make it cheaper" 

"... Oh-and make sure you build it in Alabama" 

[StrandedonEarth]

You forgot “...and keep the Shuttle  contractors involved”

Probably the biggest advantage of a clean sheet design instead of trying to make it look like they were using Shuttle-heritage systems is that they probably would have quickly concluded that LH2 for the first stage is not the most cost-effective choice. 

Edited February 13, 2021 by StrandedonEarth

[kerbiloid]

12 hours ago, JoeSchmuckatelli said:

NASA "We want a heavy lift rocket" 

Congress: "Cool, it needs to be able to go to the moon" 

".. . And Mars" 

"... And carry lots more people - make it wider" 

"... And go to the ISS" 

"Make it cheaper" 

"... Oh-and make sure you build it in Alabama" 

Let me make it brief for you.

Thiokol.

[mikegarrison]

Edited February 14, 2021 by mikegarrison

[JoeSchmuckatelli]

If / when folks return to the moon...  would it make sense to have a compressed 'air' blower system available outside the airlock / hatches to dust off the spacesuits before re-entering the craft?

 

I hear regolith in the lungs is not fun.

[kerbiloid]

No.
It's a must-have inside it.

Mars rules. It has CO2 for free.
I guess, on the Moon they should recycle the gas. Though, probably CO2, too. It's easier to freeze, and it's inert.

Unless they still hope to use those terrible suitports.
Till the first broken leg... Because how to bring a wounded inside through that small door on back without damaging him even more, when the nearest real surgery is on another planet.

They probably can try to use the suitports daily, but they anyway need a real big airlock and a way to clean the suits.

Edited February 16, 2021 by kerbiloid

[K^2]

10 hours ago, JoeSchmuckatelli said:

If / when folks return to the moon...  would it make sense to have a compressed 'air' blower system available outside the airlock / hatches to dust off the spacesuits before re-entering the craft?

That's going to be so ridiculously inefficient... I'm wondering if it makes sense to drag suits inside in the first place. Can't be that difficult to build an airlock that mates directly to the hatch on the back of the suit, can it? Seems like it'd be a much better option to just have the suits always stay on the outside.

[magnemoe]

1 hour ago, K^2 said:

That's going to be so ridiculously inefficient... I'm wondering if it makes sense to drag suits inside in the first place. Can't be that difficult to build an airlock that mates directly to the hatch on the back of the suit, can it? Seems like it'd be a much better option to just have the suits always stay on the outside.

Like this in freefall 
http://tangent128.name/depot/toys/freefall/freefall-flytable.html#3552
http://tangent128.name/depot/toys/freefall/freefall-flytable.html#981

Yes its makes plenty of sense.  

 

Edited February 17, 2021 by magnemoe