[gcanyon]

> 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, don't rely on my statements for your space ship design)

[sigmoid10]

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

[Laforet]

Relativistic effects are observed with many other 6th and 7th period elements. For example, the yellow colour of gold and caesium comes from altered electron energy levels due to relativistic orbital contraction, so are the special catalytic and bonding properties of platinum.

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

[gweinberg]

OP claimed relativistic effects explain why mercury is liquid at room temperature. That may be part of the story, but it isn't the whole thing, since other heavy elements are not liquid at room temperature.

[nyrikki]

Explaining relativistic effects in plain text forums to a general audience is a big ask, but here is a link to the first study[0] that gave evidence but it has long expected.

[0] https://onlinelibrary.wiley.com/doi/epdf/10.1002/anie.201302...

[sigmoid10]

That still doesn't answer why these relativistic effects don't cause neighbouring elements to be liquid. Electron velocities should be quite similar for them. There must be something apart from relativistic effects that makes mercury special in that regard.

[nyrikki]

Gold is right next door, relativistic effects shrink both Gold and Mercury’s 6s orbitals.

In gold it changes the color, in Mercury it changes freezing temperature.

Gallium has a low melting point 29.76C but that is due to unique chemical bonding.

"relativistic contraction" (shrinking of s and p orbitals) and "relativistic expansion" (destabilization of d and f orbitals) causes many observed phenomena.

Relativistic contraction of the 6s orbital and expansion of the 5d orbital lower the energy required to excite electrons. Consequently, gold absorbs blue light.

Strong relativistic contraction of the outer 6s electrons leaves them tightly bound and unavailable for metallic bonding. This results in incredibly weak atomic interactions, thus mercury a liquid at room temperature.

Lead also has 6s, which is what makes lead acid batteries work as well as they do.

So while the observed effects change, there are relativity effects with several nearby neighbors.

[gus_massa]

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.

[LorenPechtel]

You can start your car.

Without relativistic effects a lead acid battery would put out about .2V rather than 2V.

[zyklu5]

Nice! Thanks for this.

More details at: https://arxiv.org/abs/1008.4872

[lr1970]

Thanks for the link to the paper published in 2010 (16 years) ago. The OP article from Brown reads as if they were the first to establish importance of Special Relativity for heavy atoms which is not true.

[LoveMortuus]

I feel like that's often the case, right? Even gravity being describe first by Brahmagupta and Bhaskara II before Issac.

[beacon294]

It would be the element underneath it which is synthetic. But it is interesting that all the elements in that row are soft or brittle in pre form or in some compounds.

[sehugg]

And relativity describes the orbit of the quick-moving planet Mercury which shares its name with the quick-flowing element. What a world.

[amelius]

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

[Jblx2]

If the spatial extent of the proton is not infinite, this would imply that the charged quarks making up the proton are accelerating. Why aren't these quarks then emitting electromagnetic radiation, thus slowing down? I thought electrons were essentially standing waves around the nucleus, and thus not accelerating. Maybe there is a good youtube video explainer? Seems like there would also be an associated temperature and blackbody radiation of these quarks.

[CamperBob2]

Quarks don't have quantum energy states to transition between, hence they aren't subject to radiating photons due to acceleration.

Similar to why the electron in a hydrogen atom doesn't keep emitting radiation and crash into the nucleus once it reaches its ground state... there's no lower state for it to jump to.

[Jblx2]

Electrons in an antenna aren't transitioning between quantum states and are still radiating.

[DHRicoF]

Yes they are. They are transitioning through levels in the conduction band where you have plenty of them.

Every time you see a macroscopic phenomena, you are looking at a stupidly high amount of quantum levels with very similar energies.

[CamperBob2]

That's a good point, I don't know what's up with that. Google just says, "A single oscillating electron does not continuously emit radio waves; it has a microscopic probability of emitting a single RF photon during a given cycle." It would be necessary to delve into the whole QED thing to get a better explanation, based on what I'm reading.

Either way, quarks don't have an electron-like magnetic moment, so they aren't capable of coupling to the EM field.

[IAmBroom]

"The laws that bind an ox do not bind Jupiter" applies to quantum particles.

[dustingetz]

because conservation of energy dominates

[gcanyon]

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

[moelf]

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

[prox]

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.

[mr_toad]

> I thought it imparted all mass.

It’s all relative; in the quarks frame of reference it does get all its mass from the interaction with the Higgs field.

[prox]

I really want to read more about this. It’s fascinating but also very difficult to wrap your head around. I did enjoy the Feynman talks.

[ChrisClark]

just enough to keep electrons from staying at light speed like photons

[amelius]

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

[gigatexal]

This is the coolest fact I’ve learned in a long time. Thank you!