roobee

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Discussion between roobee and Aaron S…

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roobee

Apr 6, 2020 18:42

no problem. no rush

roobee

Apr 6, 2020 18:40

is that understanding right? adding this just in case you don't get automatically pinged, @AaronStevens

roobee

Apr 6, 2020 18:32

But if you can't express the system wavefunction as a product of individual wavefunctions. than there isn't even a wavefunction associated with each electron, only with the system. so you can't invoke Pauli's Exclusion principle to say that the 2 electrons can't be in the same state, because the electrons do not occupy a state individually. they only occupy a state as a system.

roobee

Apr 6, 2020 18:32

So when we express a system wavefunction as a product of individual electron wavefunctions. Ie: ∣↑↓⟩, which means electron 1 looks like the single electron wavefunction ∣↑⟩. where ∣↑⟩ means spin up in the ground state. similarly for electron 2. then the pauli exclusion principle makes sense.

roobee

Apr 6, 2020 18:26

hi i'm moving this to chat since the website suggested it

roobee

Apr 6, 2020 18:25

well, quantum numbers wouldn't exist anymore because there would only be one system wavefunction. and there would be no wavefunction associated with individual electrons anymore. I think?

roobee

Apr 6, 2020 18:25

Ok. But even when looking at only one observable, spin, if there is significant electron electron interaction you can't express the system wavefunction as a linear combination of the products of the individual wavefunctions right? Oh, but in that case than you wouldn't even have individual wavefunctions to examine. All the electrons would be in the same hybrid orbital. So the Pauli Exclusion Principle wouldn't even be used right?

roobee

Apr 6, 2020 18:25

for example, if ∣𝜓⟩=a ∣1⟩+b ∣2⟩+c ∣3⟩+d ∣4⟩+e ∣5⟩ where ∣1⟩ is the spin up in ground state, ∣2⟩ is the spin down in ground state, ∣3⟩ is spin up in state above ground state, ∣4⟩ is spin down in state above ground state, etc.

roobee

Apr 6, 2020 18:25

Also, it looks like you are expressing the system wavefunction as a linear combination of a product of the individual electron wavefunctions. From what I've read I think this is only allowed if there is negligible electron-electron interaction. If you don't do that, will you still get the Pauli Exclusion Principle result to arise from the anti-symmetry conditions?

roobee

Apr 6, 2020 18:25

And I'm assuming if you instead chose to make ∣𝜓⟩ a superposition of 5 basis states. And you looked at a 5 electron system. When you do the slater determinant math you would similarly have only one possible solution wavefunction. Which involves each electron in a different basis state?

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roobee

Mar 7, 2020 18:21

an electron in free space has an infinite plane wave wavefunction. however, to be localized it is expressed as a sum of plane waves of different frequencies.

however, for a particle in a box you calculate density of states. that assumes each state can only have one electron, and the same electron can't occupy multiple states.

so can an electron occupy multiple wavefunction solutions. or no?

roobee

Oct 31, 2019 00:13

@JMac thanks. it looks like you can make a water stream appear to be frozen using a trash bag. hoping i'll have the time to try it out

roobee

Oct 30, 2019 22:24

Anyone know how to recreate this?
https://www.reddit.com/r/oddlysatisfying/comments/54c9a0/this_water_stream/
I heard laminar flow nozzles and strobe lights mentioned. But most laminar flow nozzle video's I've searched although the water does look smooth it doesn't look nearly as frozen

roobee

Oct 25, 2019 04:57

@JohnRennie thanks, didn't realize spontaneous combustion is a thing. found for glucose in a divided solid state somewhere over 716 for the temp if anyone else was interested

roobee

Oct 25, 2019 04:28

it seems like a calorimeter uses electrical ignition? so electrical ignition is a reliable way to ignite difficult to ignite materials then?

roobee

Oct 25, 2019 04:09

anyone know how the enthalpy of glucose is measured? i imagine they burn powdered glucose in an o2 rich environment. but when i saw youtube videos burning powdered sugar on a table was difficult. they had to make it into a dust cloud form before it ignited

roobee

Oct 20, 2019 02:15

So ya when thinking in terms of the microscopic movement of particles it's still confusing.

How does one deduce light power has 1 Watt originally without any pre-existing light standards? I can imagine one take a watt of electrical energy, feed it into a lightbulb, measure the heat dissipation, shine the light on an photodiode, measure the temperature increase and electrical power produced. Then set that light source as a standard for light power. But that seems a hassle. Is there an easier way?

roobee

Oct 20, 2019 01:40

@JMac when thinking of energy conservation that is a good point. Although I'm not sure how the piezoelectric effect functions from a kinetic perspective. I was modeling it as a black box.

roobee

Oct 20, 2019 01:34

@JMac I was thinking the random motions of the material would bump into the piezoelectric sensor to convert into electricity?

roobee

Oct 20, 2019 01:25

@JMac That is the thermodynamic argument which I agree is experimentally correct. I am confused when thinking kinetically why I can't place tiny piezoelectric sensors (with rectifiers so the average current > 0) on a object to convert the thermal motions to electricity

roobee

Oct 20, 2019 01:10

if heat is atoms vibrating why can't we cool atoms to absolute zero by harvesting the thermal motions? i know thermodynamically this is impossible by not sure why kinetically it doesn't work.

roobee

Oct 20, 2019 00:33

so solar sails convert light to kinetic energy. but it they are very inefficient. is there some theoretical limitation or just we have not practically found a good material yet?

is there some mechanism that can reversibly convert light to kinetic energy? sorta like the piezoelectric effect except with light instead of electricity?

roobee

Oct 18, 2019 11:51

what's a summary of the recent (last 20 years) important advances in fluid mechanics?

roobee

Oct 5, 2019 23:38

math causes the most heated debates? lol

roobee

Oct 5, 2019 22:34

anyone know any recent important scientific discoveries that in retrospect were obvious and should have been discovered sooner?

roobee

Aug 29, 2019 19:08

well actually i was wondering whether weird theories could help in areas that modern physics has weaknesses in (namely actually being able to compute a solution like for chaos theory or weather prediction), at the expense of generality. but i didn't put too much hope in that idea

roobee

Aug 29, 2019 19:00

well i wasn't planning on using the weird theories practically. more like i wanted to expand the way i think of the world

roobee

Aug 29, 2019 18:40

actually, i think that's what i learned in geometry class in high school. we never used a coordinate plane or #s

roobee

Aug 29, 2019 18:31

well that's why i was interested in the most successful (in terms of predicting) of the weird theories, even knowing they wouldn't be as succesfull as modern physics.

roobee

Aug 29, 2019 18:28

That's my difficulty. I'm not sure if I know specifically what differences I'm looking for. In general, I'm looking for theories that make me think "Oh gee. That seems like a fundamentally different view on physics.". I can think of examples that make me think that, and I've stated them. But I don't know what specific property they have that made me think that.

that synthetic geometry sounds potentially interesting

roobee

Aug 29, 2019 18:19

particle particle interactions and point masses still feel too similar to field theories to me but i'll take it. any more suggestions?

roobee

Aug 29, 2019 18:16

@enumaris I originally asked what theories don't use field. Curious said basically all theories use them. So I tried finding a different word that would get people mentioning the types of theories I would be interested in, and couldn't think of any.

If theory A indeed doesn't use a field, that's fine. I would then ask again what other theories don't use fields, especially what are the most successfull theories that don't use fields.

roobee

Aug 29, 2019 18:06

like i'm trying to learn about theories that seem to have very different foundations from modern physics, like theory A. And I know that they will not be as useful/accurate, otherwise they would be popular. But I do want to know what's the best they have to offer in terms of predictions, to see just how much worse the best of them are. So I originally asked about theories that don't use universal mechanism or fields, but apparently those words were vague or inaccurate.

roobee

Aug 29, 2019 18:00

so an object imbued with earth could emanate an earth field within a short distance from it. When it interacts with your nose field or tongue field it would give a characteristic taste or smell. Or is the answer that the above is not conventially viewed as a field, and that the absence of using fields to describe things in theory A what fundamentally differentiates it from modern physics?

roobee

Aug 29, 2019 17:58

so the two theories above use fields, so that is not what differentiates them fundamentally. I don't know what else would fundamentally differentiate them, so is the answer there is no fundamental difference? Only that one is right and the other is wrong learned by experience?

roobee

Aug 29, 2019 17:54

I had originally thought the below two theories had some fundamental difference. but upon contemplation I think that there only difference is that life experience shows one to work while the other doesn't. Is this accurate?

if there is a new material and you wish to judge it's toughness you could
1) Use theory A which says to determine how much it is imbued with earth via techniques like licking and smelling it. the more earth it is imbued with the tougher it is
2) Use structural analysis according to Newtonian Physics.

roobee

Aug 29, 2019 17:18

@ACuriousMind So in order for a theory to not use fields, it would basically have to give up the concept of space, time, or both?

roobee

Aug 29, 2019 17:09

And would this count as a "field"? A theory of physics using sound as the building blocks. Upon hearing sound A, after waiting a period of time equal to how long it would take sound B to start and finish, sound C will occur 50% of the time. with inputs being A and outputs being (1, B, .5, C)?

roobee

Aug 29, 2019 17:06

@ACuriousMind What theories use fields whose output/input are not numbers/collections of numbers?

roobee

Aug 29, 2019 16:59

@ACuriousMind If modern physics don't rely on the motion and collision of matter then here is a follow up question. What theories of physics don't rely on fields (I believe QM and GR use fields)?

roobee

Aug 29, 2019 16:50

what theories of physics are there that don't rely on universal mechanism (the philosophy that everything can be reduced to the motion and collision of matter)? I can think of the "physics" of Aristotle and Native Americans, but they are very limited in what they can predict and are sometimes just wrong. What other theories qualify that do better at predicting the world? Quantum mechanics might fit but I don't have a strong enough understanding of it to say that definitively.