Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Einstein's relativity rules chemical bonds in heavy elements, new research shows

brown.edu

Post reply on HN
Print view View original

151–160 of 207 posts

Re: Einstein's relativity rules chemical bonds in heavy elements, new research shows

#151

Post by gcanyon »

amelius wrote: post #144
gcanyon wrote: post #123

> The increased nuclear mass causes orbiting electrons to speed up to a significant fraction of the speed of light, where the rules of Einstein’s theory of relativity are important. Fun fact: this is why mercury is liquid at room temperature. Its inner electrons move at close to 60% the speed of light, pulling in its outer electrons more tightly, making it harder for it to bond and be solid. (I am not a physicist, do…

Meanwhile there are quarks inside every regular atom moving at speeds like 0.99995c ...

Interesting -- does that have any macroscopic/real world impact?

Re: Einstein's relativity rules chemical bonds in heavy elements, new research shows

#152

Post by dolni »

gmueckl wrote: post #68
DiscourseFan wrote: post #34

Earlier quoted context omitted.

But oftentimes theoretical chemistry is not as important as what we get out of experiments because unlike physics, which attempts to derive general laws of nature, chemistry has to deal with the nitty gritty of the diversity of actual miscroscopic interactions of things. Any theory that is not entirely rigorous or even has slight room for an exception will be ignored by necessity, and physics is chock full of such ex…

Where is physics chock full pf exceptions?

I'm not a physicist but I've always seen physics as a bit hand-wavy myself.

Dark matter is a great example.

Our understanding of gravitation didn't cleanly apply at ultra-large scales so we had to add a massive fudge factor.

You can't "go faster" than the speed of light, but space in between things can expand faster than the speed of light.

It seems like things that are "settled" regularly get an "ope, but except for this special case..." treatment.

Re: Einstein's relativity rules chemical bonds in heavy elements, new research shows

#153

Post by jeremyjh »

ordersofmag wrote: post #146
tremon wrote: post #140

Earlier quoted context omitted.

I don't think that's true. Mathematics can model every conceivable universe; you cannot derive the values of c or G in our universe from a purely mathematical model. Even if there were a proof that the current values for cosmological constants are the only possible values, that proof would necessarily have to rely on lemmas from physics.

It could be that once we truly understand math in a complete way it would lead inexorably to the definition of one and only one possible universe with only one possible set of rules and c and G would simply fall out naturally. I'd agree it seems unlikely given our current understanding of math and physics (and their relationship to each other). But given both are incomplete it remains a possibility. The one theme tha…

Please tell us more about this. I’m not familiar with any definition of mathematics that would support the idea that it can prove statements about our universe without access to observed facts.

Are there any papers where this possibility is explored? What does it mean to have a complete understanding of mathematics?

Re: Einstein's relativity rules chemical bonds in heavy elements, new research shows

#154

Post by moelf »

gcanyon wrote: post #151
amelius wrote: post #144

Earlier quoted context omitted.

Meanwhile there are quarks inside every regular atom moving at speeds like 0.99995c ...

Interesting -- does that have any macroscopic/real world impact?

well, 90%+ of the mass of a proton comes from moving stuff, rather than rest mass of the quarks.

so the real world impact is, having anything at all

Re: Einstein's relativity rules chemical bonds in heavy elements, new research shows

#155

Post by alok-g »

colechristensen wrote: post #39
nanolith wrote: post #14

Wait... wasn't it already understood that relativity influences electron orbits of heavy elements? I clearly remember being taught some of this in physics, in the mid-noughties. For instance, we know that gold gets its color from relativistic effects. https://physics.aps.org/articles/v10/s3

The Dirac equation which is the equation for describing the wavelike behavior of electrons. It predicted the existence of antimatter and particle spin. You start with the Schrödinger equation, add relativity to get the Klein-Gordon equation which is a mess because it's second order in time involving negative probabilities, if you in ways "take the square root" of it you get the Dirac equation. Relativity has been par…

Thanks for the insights. I am interested in learning all this stuff. Am currently going through just Schrodinger's Equation. Do you have book recommendation(s) that include insights everywhere just like what you shared? Thanks.

Re: Einstein's relativity rules chemical bonds in heavy elements, new research shows

#156

Post by alok-g »

gus_massa wrote: post #112
brabel wrote: post #85

Earlier quoted context omitted.

I don’t understand how something that has no clearly defined position like an electron can have a well defined speed. I thought I had understood that at that level, particles are more like clouds, or vibrations in the quantum field, and they had no well defined position until you tried to measure it, causing its cloud to collapse to a smaller region. But if non observed electrons can have a speed that defines the col…

You are mostly correct. The idea is that it has not a clearly definite position, but it has a distribution of probability to find it that looks like a "cloud" https://en.wikipedia.org/wiki/Atomic_orbital In a more abstract sense, has not a clearly definite speed, but it has a distribution of probability to find it in a speed graphic. The distribution of position and speed are defined by an equation and you must add a…

(Newbie here). And then going further, shouldn't there also be acceleration and its distribution? It says classical models could not explain why accelerating electrons were not radiating. If acceleration also shows up in QM, then ... a distribution of radiation?

Re: Einstein's relativity rules chemical bonds in heavy elements, new research shows

#157

Post by gus_massa »

sigmoid10 wrote: post #124
gcanyon wrote: post #123

> The increased nuclear mass causes orbiting electrons to speed up to a significant fraction of the speed of light, where the rules of Einstein’s theory of relativity are important. Fun fact: this is why mercury is liquid at room temperature. Its inner electrons move at close to 60% the speed of light, pulling in its outer electrons more tightly, making it harder for it to bond and be solid. (I am not a physicist, do…

I guess the more interesting question is why this doesn't happen for neighbouring elements in the periodic table?

It also has an effect, it is a small correction in the energies and bounding. Sometimes it's enough to change the color or state, sometimes it's a correction like making it 1% softer or harder and is not interesting unless you are a specialist.

Re: Einstein's relativity rules chemical bonds in heavy elements, new research shows

#158

Post by terminalbraid »

moring wrote: post #130
terminalbraid wrote: post #115

Earlier quoted context omitted.

That's a fundamentally different problem and a terribly unfair comparison.

Am I right with my assumption that by "fundamentally different problem", you mean we lack a good simulation model, but that the number of degrees of freedom would actually be manageable?

To simulate a proton you need to solve a strongly coupled highly relativistic SU(3) gauge theory (naturally non-abelian i.e. the force carrier field itself carries charge and is self-interacting at tree order) problem with constituents that have masses orders of magnitude below the relevant energy scales (i.e. you have many matter AND force particles that can pop in and out of existence and they all strongly interact with one another).

To simulate a water molecule you do so with a weakly coupled SU(1) gauge theory (light does not interact with itself at tree order) problem where the masses of all constituents are orders of magnitude above the relevant energy scales (you can think of it as the electrons and nuclei and particles coming in and out of existence are contained in a renormalization scheme).

We have "good simulation models" of both, but the former is extraordinarily complicated compared to the latter for the reasons stated above.

Re: Einstein's relativity rules chemical bonds in heavy elements, new research shows

#159

Post by amelius »

moelf wrote: post #154
gcanyon wrote: post #151

Earlier quoted context omitted.

Interesting -- does that have any macroscopic/real world impact?

well, 90%+ of the mass of a proton comes from moving stuff, rather than rest mass of the quarks. so the real world impact is, having anything at all

And this mass is again an emergent property of Einstein's relativity ...

Re: Einstein's relativity rules chemical bonds in heavy elements, new research shows

#160

Post by prox »

moelf wrote: post #154
gcanyon wrote: post #151

Earlier quoted context omitted.

Interesting -- does that have any macroscopic/real world impact?

well, 90%+ of the mass of a proton comes from moving stuff, rather than rest mass of the quarks. so the real world impact is, having anything at all

I think I recently learned that the Higgs is actually not that much part of imparting mass for atomic particles. I thought it imparted all mass.
Post reply on HN