1

Chemistry / Re: Could sodium be used as fuel?

« on: Yesterday at 19:19:07 »

Indeed, NaK is awesome stuff (in the biblical sense), and so fun to make...

But I think this thread has gotten a little off topic...   

I think there are many good reasons given in previous posts as to why sodium does not have what it takes to make a good fuel.

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Chemistry / Re: Could sodium be used as fuel?

« on: Yesterday at 01:51:43 »

Sodium metal is a solid (though it melts at only about 100 °C), so it would be difficult to transfer it from storage tanks to fuel tanks, and from there into whatever engine could use it

Like coal, for instance.

Oh, so I take it your automobile and your plane both run on coal?

3

New Theories / Re: How will buckyballs fired at a double slit behave?

« on: 15/06/2019 21:16:59 »

If so, you are blind to the real world.

Then you are welcome to celebrate your clarity elsewhere and leave us to wallow in our ignorance.

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New Theories / Re: How will buckyballs fired at a double slit behave?

« on: 15/06/2019 20:02:55 »

I don't care what you call the experiment as long as you admit to no physicality in matter waves.

I will admit no such thing.

I will admit that:
A) buckyballs, or electrons, or whatever, are neither particles nor waves...
B) ...but they exhibit both wave-like and particle-like properties.
C) And whatever they "actually are," they are physical entities, with properties we call mass, charge, momentum, etc.
D) wave functions are mathematical equations that describe the behavior of these particles—wave functions are not actual physical entities.

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Physics, Astronomy & Cosmology / Re: Do Matter Waves collapse when bumping into any large object?

« on: 15/06/2019 19:55:16 »

So all the "atom in a box" analogies are pointless :/

Not pointless, just vastly oversimplified. They are good learning tools, and can be used as a starting point to make very crude predictions about real-world phenomena (like UV-vis spectra of flat, highly conjugated molecules, or crystallin nanoparticles), but are by no means an accurate representation of any real-world phenomenon.

If I may, I suspect that some of the apparent contradictions you see in QM has to do with the fact that none of the examples that show up in introductory textbooks/classes/videos are depictions of real-world scenarios. "Imagine the entire universe only contains two point particles, each with mass m, connected by a massless perfect spring, with spring constant k, and average length d"

is a far cry from

 "Imagine a hydrogen molecule as a system of two protons, each with mass, charge, and magnetic moment, and two electrons, each with their own mass, charge, and magnetic moment. These four 'particles' are all interacting with each other as if they are more like 'waves' in that the distance between the protons ends up being on the order of the wavelengths of the electrons, so the whole thing is a big interference pattern, but the whole ensemble is in constant motion--the distance between the protons is constantly oscillating, but like an oscillator with a spring constant that depends on the intereference pattern of the electrons, which is itself influenced by the distance between the protons.... oh, and this ensemble is constantly bombarded with photons that can change the wavelengths of the electrons, or make the molecule vibrate faster, or make it rotate, each of which would change everything about the whole molecule except the mass and charge involved (so go back to the top), and it can change rotation, vibration, and electronic wavelength all simultaneously... oh, and then the molecule can change again by emitting a photon, which is a purely stochastic event... oh and the whole system occasionally bumps into other complex systems, exchanging energy, momentum, angular momentum, and sometimes even particles..."

And even this last description is a VAST oversimplification.

6

New Theories / Re: How will buckyballs fired at a double slit behave?

« on: 15/06/2019 18:58:48 »

I think we are now confusing two different (but slightly related) concepts: tunneling and interference.

Interference has to do with how waves move AROUND barriers (or how waves from multiple sources interact).

Tunneling has to do with how waves behave at edges (and that they don't just stop). A buckyball (being composed of sixty nuclei and hundreds of electrons) is highly unlikely to tunnel through any barrier. However, single elementary particles can tunnel over vast distances (on a molecular scale) through barriers or empty space.

~~~

There is also the issue that we have to consider what the actual structure of the slits is. Are they gaps within a material barrier that is made of atoms? If so: What kinds of atoms, and how are the connected? How thick is the barrier, and what is the shape of the slits (again remembering that if the edge is made of atoms, it must be "fuzzy" too). If not: what is it made of???

7

Physics, Astronomy & Cosmology / Re: Do Matter Waves collapse when bumping into any large object?

« on: 15/06/2019 18:49:32 »

It is increasingly difficult to prevent wave function collapse for systems of increasing complexity, over longer distances and times. Essentially any interaction with anything else (massive or not) can disrupt superpositions. This is the primary roadblock to quantum computing, and why IBM quantum computers are mostly (by mass, volume, and $$$) refrigerators capable of keeping the actual computer bit REALLY cold.

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Physics, Astronomy & Cosmology / Re: Do Matter Waves collapse when bumping into any large object?

« on: 15/06/2019 18:46:22 »

Let me ask in a different way. If a free atom were to bump against any large object, would its state change?

probably

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Chemistry / Re: Could sodium be used as fuel?

« on: 15/06/2019 12:38:36 »

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Physics, Astronomy & Cosmology / Re: Can tunneling work with gravitational potential wells?

« on: 15/06/2019 12:34:43 »

Tunneling amplitude is proportional to e^{–width of barrier}

https://en.wikipedia.org/wiki/Quantum_tunnelling

even empty space can be viewed as a barrier through which to tunnel.

Electric potentials within molecule-scale systems can have very high gradients, so the distances involved are small.

For gravitational wells, gradients are typically not very strong (except in the hypothetical cases mentioned by evan_au), so the distances are likely to be such that tunneling can only happen once every million universe lifetimes or so (not actually calculated, but you get the idea)

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New Theories / Re: How will buckyballs fired at a double slit behave?

« on: 15/06/2019 01:55:48 »

...hmm, you guys are so close to admitting it.

"admitting it" makes it sound as if you believe that "we" know something and are actively trying to prevent that knowledge from spreading...

12

New Theories / Re: How will buckyballs fired at a double slit behave?

« on: 14/06/2019 15:00:34 »

And by the way, buckyballs are far smaller than the largest objects that have been shown to have quantum behaviors: https://medium.com/the-physics-arxiv-blog/physicists-smash-record-for-wave-particle-duality-462c39db8e7b

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New Theories / Re: How will buckyballs fired at a double slit behave?

« on: 14/06/2019 14:56:21 »

I am a professional chemist. I think about electrons and atoms and molecules and molecular-scale systems day-in and day-out. I am well aware that they are neither particles nor waves.

But it is very convenient to think about them as such in certain situations.

I have a kit sitting on my desk in front of me now, which allows me to build models of molecules with balls and sticks. This is very easy to visualize, and holding the models in my hands allows my physical-spatial intuition to make very useful predictions. But let's be honest: these balls and sticks are no more like molecules than this →  ← is a face.

Unfortunately for our simple minds, simplistic models like balls and sticks, fall short quite often when considering systems at this scale. Waves, springs, and pendulums (pendula?) are the next step up, and allow us to tackle dynamic and indeterminate systems.  But again, a system of oscillating springs is not more like a molecule than this ↓

face.jpg (65.93 kB . 542x840 - viewed 305 times)
↑ is a face.

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Chemistry / Re: Could sodium be used as fuel?

« on: 14/06/2019 14:46:34 »

In addition to the safety and efficiency concerns pointed out by Kryptid, I will comment on a few points:

• Good fuels are not just for storing and releasing energy. That energy has to be able to do work (son). For conventional fuels in combustion engines, this work is in the form of PV work (change in pressure and volume), which means that during combustion, they release hot gases, which then push the pistons, and move the vehicle forward. Sodium produces a lot of heat (thermal energy) when reacting with oxygen, but does not produce any gas (in fact it consumes gas), so it would be rather inefficient at performing PV work--most, if not all, energy would just go to heat (this heat could be used to expand another gas, which could do PV work, as in a heat engine, but I don't imagine that would be more effective than an internal combustion engine.

Another way for sodium to perform work would be to use it in an electochemical cell, have it produce an electromotive force, and use that to perform work. This could well be significantly more efficient than an internal combustion engine. I believe there is actually a significant amount of work being done on sodium-oxygen, sodium-air, and sodium sulfur batteries (though I don't know if there are any plans for putting these in cars or planes...) It is somewhat controversial whether the electron sources in batteries count as "fuel" but this is only a semantic argument.

• One could also imagine reacting sodium with water to produce heat and hydrogen, which would then be combined with oxygen to make hot water vapors which could drive a combustion-type engine, but there are many safety and logistical issues with this approach. Sodium metal is a solid (though it melts at only about 100 °C), so it would be difficult to transfer it from storage tanks to fuel tanks, and from there into whatever engine could use it (liquid fuels are very convenient). Also, the violence of the reaction with water could be a very significant safety hazard, and the caustic (and boiling hot) sodium hydroxide solution would be very corrosive, placing severe limitations on the materials that could be used for constructing the engine (as well as have a high cost for disposal). When combined with the requirements for robustness to thermal shock, I think there would be very few suitable materials indeed.

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New Theories / Re: How will buckyballs fired at a double slit behave?

« on: 14/06/2019 04:02:36 »

waves are matter...

rather, matter can be modeled as waves, not just as particles

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New Theories / Re: How will buckyballs fired at a double slit behave?

« on: 14/06/2019 03:53:18 »

Mass has little to do with how big a slit something needs to get through... (so the proposed experiment can neither confirm nor challenge the notion that waves can have mass--spoiler alert, waves can have mass)

...but there is a somewhat nifty way to see that mass is important for calculating tunneling barriers for particles (which depends on the wave function treatment of the particles):

We can measure the rates of chemical reactions, and see how much they change when hydrogen atoms are switched for deuterium (chemically identical isotope, but with twice the mass). This is called the kinetic isotope effect (or KIE). Sometimes a hydrogen atom has to tunnel from one place to another for the reaction to occur, and sometimes (especially when the reaction is very cold) this is the rate determining step, which means that we can directly measure how long (on average) it takes for protons to tunnel from x to y, and compare with hoe long it takes deuterons to tunnel from x to y. When this tunneling is the rate determining step, the KIE is very large, sometimes even slowing down by a factor of 100 when doubling the mass of the tunneling particle. This means that mass is an important property of a quantum object, even when considering it as a wave.

https://en.wikipedia.org/wiki/Kinetic_isotope_effect#Tunneling

17

Chemistry / Re: why do phosphines and isonitriles smell so bad, while CO is odorless?

« on: 11/06/2019 17:05:22 »

I think evolution is the answer here those who could not smell carbon monoxide despite its harmful effects carried on cooking and warming their caves and bred more than those who did not use fire.

ahh... I guess I didn't think about it that way. Could make sense. Do we know whether animals (of the non-cooking variety) can smell CO?

18

Chemistry / why do phosphines and isonitriles smell so bad, while CO is odorless?

« on: 10/06/2019 22:45:07 »

I’m not sure which section this goes in (could also be physiology or biology).

Why is it that we have such a strong visceral reaction to the smell of compounds like primary phosphines, even at very trace levels? (some have odor thresholds below 1 ppb) They are toxic by inhalation at the ppm level, but I don’t think our ancestors would ever have had the pleasure of smelling such compounds. Sulfides, sure, but phosphines? The perception of these compounds by smell could be  very similar (sulfides and phosphines are chemically similar), but why are they sooo bad?

Also, isonitriles are similarly wretched-smelling, but the analogous carbon monoxide (which is chemically fairly similar) is completely odorless. And I am quite confident that our ancestors came into quite a bit of contact with carbon monoxide while they were working out the whole fire thing.

It is all quite curious…

19

New Theories / Re: Why Do You Believe Superposition/Entanglement Include Spacetime?

« on: 06/06/2019 23:51:04 »

I'm saying, I understand the double slit experiment better than anyone.

Well then. I guess this is about as far as this thread can go then...

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New Theories / Re: Why Do You Believe Superposition/Entanglement Include Spacetime?

« on: 06/06/2019 18:57:44 »

I don't understand what you're trying to say here... but I will try to provide some pertinent information:

A) The wave function of a quantum object (like an electron in a H atom) can be used to determine the probability amplitude of the electron in both time and space. Though there are also quantum aspects that can be probed without gaining (or losing, or requiring) any information about space, like spin state (so space is irrelevant for quantum entanglement dealing only with spin) see more here: http://farside.ph.utexas.edu/teaching/qmech/Quantum/node88.html 

B) as far as I know, neither space nor time is quantized, so we cannot talk about the "wavefunction" of spacetime.

C) relativity does apply to the very small: we can see relativistic effects on single electrons going very fast, or that are very near large nucleii (search for relativistic corrections for wave functions and gold or mercury)

D) and quantum also applies to very big (at least, virus size).