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July 20

Element bonding

I learnt in school that different types of elements can bond in different ways, like non-metal atoms bond covalently together while a non-metal atom with a metal atom bond ionically, but why is that? Also, what factor(s) determine why some elements (like hydrogen) share/transfer 1 electron, while others (like carbon and nitrogen) and share/transfer 2 or 3 electrons? Bestfweind (talk) 04:58, 20 July 2024 (UTC)[reply]

More than anything else, it's the number of valence electrons that each atom has, and the number that it needs. Hydrogen needs just one extra valence electron to have a full outer shell, so two hydrogens share a single electron. Nitrogen needs three, so two nitrogens share three electrons. Nyttend (talk) 07:00, 20 July 2024 (UTC)[reply]

Also, you may be thinking of common compounds such as table salt, sodium chloride, which involves an alkali metal (at the left end of the periodic table) and a halogen (near the right end). Like the other alkali metals, sodium has just one valence electron, so it's highly electropositive (ready to give up an electron), and like the other halogens, chlorine needs just one valence electron, so it's highly electronegative (ready to gain an electron), and it's extremely easy to create an ionic bond between atoms that are both highly electropositive/negative and that need to give/take the same number. Nyttend (talk) 07:06, 20 July 2024 (UTC)[reply]

The bond is better described as ionic when one atom is much more electronegative than the other. In something like table salt you can approximate the valence electron of Na as having passed completely to the Cl, although in reality it's not a complete transfer. Covalency happens when the electronegativities are similar. It is all a continuum from one to the other: Na–Cl will be more ionic than Li–Cl, which will in turn be more ionic than C–Cl.

The first-row elements B–Ne have a larger tendency towards multiple bonding than their higher homologues in lower rows, because their atoms are so small that non-bonding pairs of electrons result in significant repulsion. It's less of an issue for things like Al–Ar. Double sharp (talk) 07:24, 20 July 2024 (UTC)[reply]

Our Double bond rule is quite light on cited content for the concept itself, and gives (with cite, that I can't access) a different rationale. Please update if you've got a ref. DMacks (talk) 03:02, 21 July 2024 (UTC)[reply]

doi:10.1002/anie.198402721. I've updated the page. :) Double sharp (talk) 03:46, 21 July 2024 (UTC)[reply]

Thanks! I keep meaning to split up that hybrid (ha!) of an article, but obviously keep never getting around to it. DMacks (talk) 04:37, 21 July 2024 (UTC)[reply]

@DMacks: Also, I added a link to double bond rule in kainosymmetry, where this (together with other unusual features of first-row elements) is discussed. Double sharp (talk) 06:10, 23 July 2024 (UTC)[reply]

Big Bang vs supernatural creation

When there are evidence in support of Big Bang, why do people believe in God? CometVolcano (talk) 16:41, 20 July 2024 (UTC)[reply]

What better explanation of the Big Bang is there? You did note who first proposed it (second sentence of article)? -- Verbarson ^talk_edits 17:28, 20 July 2024 (UTC)[reply]

It also depends on how one defines "God". ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:04, 20 July 2024 (UTC)[reply]

God could have started things off with a big bang. The two are not mutually exclusive. There are physics Nobel laureates who are Christians, e.g. Charles H. Townes. Clarityfiend (talk) 02:40, 21 July 2024 (UTC)[reply]

Also renowned cosmologist and Quaker George F. R. Ellis. Clarityfiend (talk) 03:32, 21 July 2024 (UTC)[reply]

See Religious interpretations of the Big Bang theory. Double sharp (talk) 04:09, 21 July 2024 (UTC)[reply]

If a belief is not falsifiable, evidence seems irrelevant. Sean.hoyland (talk) 11:41, 21 July 2024 (UTC)[reply]

If image sleuths were to discover that the unexplained "Little Red Dots" observed by the JWST,^[1] as seen from the solar system against the cosmic expanse, actually spell out a message in a well-known two-dimensional barcode, namely, "Of course I exist, you blockheads. Yours forever, God", would this seem relevant evidence? --Lambiam 12:09, 22 July 2024 (UTC)[reply]

Carl Sagan postulated a somewhat similar idea in one of his books. However, there's also the logic problem postulated in the Hitchhiker's Guide. ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:40, 22 July 2024 (UTC)[reply]

Most people who believe in a god believe in the same one as their parents, implying that they do so because of what some would call cultural influences, but which I call love bombing and brainwashing from birth. HiLo48 (talk)

"Of course I exist, you blockheads. Yours forever, God" - I guess it could be evidence of something, trickster djinns, the breaking of the 4th wall between simulator and simulated etc. They could simply arrange in person book signings for their best-selling books, go on some podcasts etc. Sean.hoyland (talk) 07:35, 23 July 2024 (UTC)[reply]

Nay I say! No sceptic can deny the uncontrovertably unfalsifiable revelation that the number pi found in epiphany when expanded to sufficiently many decimal places actually contains the message "Of course I exist, you blockheads. Yours forever, God", perfectly encoded in ASCII, itself proof of a divine miracle predating knowledge that humans gained no earlier than 1963 as attested by these witnesses. Philvoids (talk) 20:54, 24 July 2024 (UTC)[reply]

I will add that the big bang is what happened after the creation, but was not the singularity that was the start of the Universe. So creation is at time 0. Big bang in the interval (0,CMB visibility] Graeme Bartlett (talk) 01:59, 23 July 2024 (UTC)[reply]

That claim definitely needs a Reliable source. HiLo48 (talk) 02:11, 23 July 2024 (UTC)[reply]

It is stated in our article on the Big Bang, with sources (see the "Singularity" section), that some authors use "Big Bang" to just mean the initial singularity and others include some periods after it. I'd argue that the name Big Bang nucleosynthesis sort of implies that at least the first few minutes (when deuterium, helium, and lithium are synthesised) can be taken as part of the "Big Bang". Double sharp (talk) 06:03, 23 July 2024 (UTC)[reply]

And Creation? There is no science behind that at all. HiLo48 (talk) 06:36, 23 July 2024 (UTC)[reply]

Graeme Bartlett said that "creation is at time 0". That's a clearly scientific definition, though I suppose you can call it instead the initial singularity, if you like that name better. I suppose physics before the quark epoch is not yet empirically testable, in the sense that current accelerators cannot reach the energies needed to explore electroweak unification, but that's a matter of our current level of technology. Double sharp (talk) 08:47, 23 July 2024 (UTC)[reply]

It's also a matter of theory — beyond a certain point we need a theory of quantum-gravity to proceed, and that does not exist yet. The "Big Bang" singularity is an extrapolation based on known physics, which is known (pun...) to not be applicable to those conditions. So the evidence for a "Big Bang" is not quite what OP appears to imagine it to be. --Wrongfilter (talk) 09:58, 23 July 2024 (UTC)[reply]

A very good point indeed. My apologies; once quarks stop being confined, it's not something I know much about anymore. :) Double sharp (talk) 03:29, 24 July 2024 (UTC)[reply]

A common mistake, made by people at both sides of the controversy, is that God and religion are not meant to provide answers about the physical world. God is not meant to be an answer to the origin of the universe, the origin of life or any such question that requires a scientific answer. “Give to Caesar what belongs to Caesar, and to God what belongs to God” Cambalachero (talk) 03:45, 24 July 2024 (UTC)[reply]

And that statement is just an opinion or point of view. What does "meant" mean? See Proximate and ultimate causation and Meaning of life. Graeme Bartlett (talk) 07:54, 25 July 2024 (UTC)[reply]

How about: A great deal of unnecessary conflict has been created by people who assume that 2000-3000 year old Hebrew literature is the same genre as nineteenth-century scientific journals, and can therefore be understood using exactly the same assumptions and literary methods. -- Verbarson ^talk_edits 20:54, 25 July 2024 (UTC)[reply]

Yes, the thousands years old Hebrew literature was written at a time when humans understanding of the nature was rudimentary and primitive, when people thought the Earth was the center of the universe and concept of atoms, subatomic particles and periodic table did not exist. --CometVolcano (talk) 16:01, 26 July 2024 (UTC)[reply]

Democritus: Say what? Clarityfiend (talk) 08:41, 27 July 2024 (UTC)[reply]

~~Aristarchus: Hmm?~~ Double sharp (talk) 08:45, 27 July 2024 (UTC)[reply]

From well before these guys. Graeme Bartlett (talk) 12:24, 27 July 2024 (UTC)[reply]

Indeed. *facepalm* Double sharp (talk) 14:04, 27 July 2024 (UTC)[reply]

At that time, humans had no understanding of the nature of the universe. They did not know there are many galaxies in the universe. It was not untill the Great Debate (astronomy) humans did not know that Milky Way is one of billions of galaxies in the universe. --CometVolcano (talk) 19:25, 27 July 2024 (UTC)[reply]

And a generation (or two) ago scientists hadn't noticed the 95% of the universe we now call dark energy and dark matter. Just imagine what our grandchildren will discover (and how condescending they might be about our ignorance). -- Verbarson ^talk_edits 21:48, 27 July 2024 (UTC)[reply]

+1 Double sharp (talk) 04:07, 28 July 2024 (UTC)[reply]

Length contraction

Since it doesn't only refer to an object's length, but also to any abstract length, so why isn't this general fact mentioned in the lead of the article Length contraction, nor in (most of) the common literature discussing the phenomenon of length contraction?

Explanation: The lead of our article claims the following: If we (travel on a train and) observe a moving "object" (e.g. a moving building), for which $L$ is the object's length measured in the object's reference frame, then we will meausre the object's length to be shorter, i.e. $L/\gamma .$ So, why does the lead of our article (as well as the professional literature discussing this phenomenon) only mention an "object", even though this is also true for abstract lengths? Just substitute "distance" (e.g. between two buildings) for "object", and you'll get the following true analogous sentence: If we (travel on a train and) observe a moving distance (e.g. a distance between two co-moving buildings), for which $L$ is the distance's length measured in the distance's reference frame (i.e. in the reference frame of the buildings), then we will meausre the distance's length to be shorter, i.e. $L/\gamma .$

Indeed, our article contains some hints, e.g. in the chapter "Basis in relativity": Here, "object" simply means a distance with endpoints that are always mutually at rest, i.e., that are at rest in the same inertial frame of reference. Yet, this general fact is neither mentioned nor implied, neither in the lead - nor in the chapters that prove the length contraction - nor in (most of) the common professional literature. HOTmag (talk) 19:26, 20 July 2024 (UTC)[reply]

The phrase "any length in the moving object's reference frame" is ambiguous. Supposedly it is the length of some (other) object. Is it co-moving with the first object? By "a moving object measures (some length)", do you mean, "an observer to whom this moving object is at rest measures (some length)"? It is not very clear. --Lambiam 20:20, 20 July 2024 (UTC)[reply]

There once was a fellow called Fisk
Whose fencing was strikingly brisk
So fast was his action
That FitzGerald contraction
Reduced his rapier to a disk
—I thought this was an original Lear, but can't find it. It was printed in our physics books at school in the 1970s.Martin of Sheffield (talk) 20:48, 20 July 2024 (UTC)[reply]

Our articles say that Lear died in 1888 and Length contraction wasn't postulated by George FitzGerald until 1889. AlmostReadytoFly (talk) 11:11, 22 July 2024 (UTC)[reply]

My answers to all of your questions are positive.

Let's focus on the following concrete example: If a moving observer measures a given distance between two trees to be one mile long, then we measure this distance to be shorter, i.e.

1/\gamma

mile long, right? So, why isn't this fact mentioned in the article? It only mentions an "object's length", which really includes the observer's length, yet not any abstract length, e.g. a distance between two trees and likewise. The phenomenon of length contraction is not only about an object's length, right? HOTmag (talk) 22:04, 20 July 2024 (UTC)[reply]

If the observer is moving along a row of trees, the trees are moving relative to the observer, so this moving observer will observe length contraction by a factor of

\gamma ^{{-}1}

for the distance between successive trees, compared to this distance as measured by an observer in whose frame of reference the trees are not moving. So, if "we" are the latter observer, we measure this distance to be longer, by a factor of

\gamma ,

than the length reported by the moving observer. If, on the other hand, the trees are moving with the observer, who (from their point of view) is standing still among a row of trees while seeing us whizz along in a rocket, this observer, who is moving only relative to us and not to the trees, will not observe length contraction for the distance between successive trees, whereas to us in the rocket the trees are moving, so we measure the inter-tree distance to be shorter by a factor of

\gamma ^{{-}1}.

Do you feel our article should explicitly mention the fact that length contraction is not observed by an observer in whose frame of reference the object is not moving? --Lambiam 06:32, 21 July 2024 (UTC)[reply]

I'm really referring to the latter case you've mentioned, in which the trees are co-moving with the observer, who sees them at rest. It's only us who see, both the observer and the trees, co-moving at the same velocity.

As for your last question: No, I don't want our article to mention the obvious fact that no length contraction is observed by any observer in whose frame of reference the object being measured is at rest. However, I do want the lead of our article, as well as the professional literature discussing the phenomenon of length contraction, to mention that this phenomenon is not only about a given object's length but also about a given abstract length.

Let me explain my point: The lead of our article claims (in my own words) that: if we (travel on a train and) observe a moving "object" (e.g. a moving tree), for which

L

is the object's length measured in the object's reference frame, then we will meausre the object's length to be shorter, i.e.

L/\gamma ,

right? I guess you agree (if not to my exact own words then to their content). So, why does the lead of our article (as well as the professional literature discussing this phenomenon) only mention an "object", even though this is also true for abstract lengths? Just substitute "distance" (e.g. between two trees) for "object", and you'll get the following true analogous sentence: If we (travel on a train and) observe a moving distance (e.g. a distance between two co-moving trees), for which

L

is the distance's length measured in the distance's reference frame (i.e. in the reference frame of the trees), then we will meausre the distance's length to be shorter, i.e.

L/\gamma ,

right? This was my question from the very beginning. HOTmag (talk) 07:57, 21 July 2024 (UTC)[reply]

Certainly two trees set a distance apart is an object that has length. They don't have to be touching anymore than the solar system's planets do. Modocc (talk) 11:22, 21 July 2024 (UTC)[reply]

I think the term "system's length" is more appropriate, than the term "object's length", as far as a distance (between two trees or two planets and the like) is concerned. Have you ever called the solar system "an object"? HOTmag (talk) 11:58, 21 July 2024 (UTC)[reply]

Our solar system is a physical object. As are galaxies and our universe. Of course, these kinds of objects have spatial dimensions and a time dimension. Modocc (talk) 12:11, 21 July 2024 (UTC)[reply]

Which name is more appropriate: a "solar system" or a "solar object"?

On the other hand, which name would you prefer: a "system" consisting of two trees, or an "object" consisting of two trees? HOTmag (talk) 13:14, 21 July 2024 (UTC)[reply]

Depends on the physical context. The term "system" regarding physical objects tends to be more abstract and typically refers to processes like with manufacturing and computers. An atmospheric cloud is both a system of particles and an object. Modocc (talk) 13:24, 21 July 2024 (UTC)[reply]

Back to the trees observed by an observer on a moving train, who sees them co-moving and measures the distance between them: They are pretty wide, so the length being measured is not required to include their width, but only the distance between them, i.e. excluding them. This distance is influenced by the effect of length contraction. Would you call this distance an "boject", a "system", or simply a "distance"? The same question may be asked about the distance between two stars, excluding them. HOTmag (talk) 14:10, 21 July 2024 (UTC)[reply]

The length between buttons is the same as the distance between them. With relativity the measured contraction is ~~not an "effect", it is~~ a change in coordinates. The stationary Earth is an oblique sphere, but with reference frame Lorentz boosts it is pancake-shaped instead. Of course, isometries of Minkowski spacetime are defined by the Poincaré group and its subgroup the Lorentz group. Modocc (talk) 14:39, 21 July 2024 (UTC)[reply]

With relativity the measured contraction is not an "effect". I've never disagreed. I called it "effect", just because it's called "effect" - in the lead of our article Length contraction - and in common speech.

The length between buttons is the same as the distance between them. This is exactly what I'm claiming from the very beginning. That's why I'm asking, why the lead of that article - only attributes that contraction to objects - and not also to distances as in your example of a distance between two buttons. HOTmag (talk) 17:02, 21 July 2024 (UTC)[reply]

Right. Matter is composed of various objects and referring to distances between their elements is simply redundant when length suffices, especially when talking about object velocities. Modocc (talk) 17:46, 21 July 2024 (UTC)[reply]

Referring to distances between their elements is simply redundant when length suffices. Does mentioning "length" alone, suffice? Our article is not satisfied with mentioning "length" alone, and mentions an "object's length", so I asked: Why "object's length" only, and not also a "distance's length", as in your example of a distance between two buttons. This distance has nothing to do with matter, because it excludes the buttons. HOTmag (talk) 18:35, 21 July 2024 (UTC)[reply]

The distance between buttons is spacial is it not. They are embedded in actual space. Thus the distances between the ends of rulers are the same as their lengths. Modocc (talk) 18:47, 21 July 2024 (UTC)[reply]

is it not. Yes it is.

the distance between the ends of a ruler is the same as the ruler's length. Your argument is the following: With regard to length contraction, OBJECT includes a ruler, whereas RULER includes any abstract length, Hence OBJECT is supposed to include any abstract length...

Just as, with regard to time dilation, OBJECT includes a clock, whereas CLOCK includes any abstract time, hence OBJECT is supposed to include any abstract time......

According to your explanation, the leads of our articles Length contraction and Time dilation, should've used, either the terms "object's length" and "object's time", respectively, or the terms "ruler's length" and "clock's time", respectively, or "length" alone and "time" alone, respectively.

However, this is not the case. The lead of our article Length contraction attributes "length" to an "object", rather than to a "ruler", whereas the lead of our article Time dilation attributes "time" to a "clock", rather than to an "object". How do you justify this asymmetry, between length contraction and time dilation? HOTmag (talk) 19:38, 21 July 2024 (UTC)[reply]

Rulers and clocks are objects that measure space and time. With relativity their asymmetric reference frame dependencies are a consequence of a coordinate change given the supposed existence of SR and GR's spacetime which conserves the distances of its worldlines. It is by no means a classical model. Modocc (talk) 20:02, 21 July 2024 (UTC)[reply]

When I recently asked you about how "you justify this asymmetry between length contraction and time dilation", I didn't refer to what you're calling now "their asymmetric reference frame dependencies", but rather to the asymmetry between - how the lead of our article length contraction attributes "length" to an "object" rather than to a "ruler" - and how the lead of our article time dilation attributes "time" to a "clock" rather than to an "object".

Please notice, that according to your explanation in your previous response, the leads of those articles should've used, either the terms - "object's length" and "object's time" - respectively, or the terms - "ruler's length" and "clock's time" - respectively, or "length" alone and "time" alone respectively. However, this is not the case in the leads of those articles. My recent question was: Why, and it only referred to the leads of those articles (as well as to the common professional literature). HOTmag (talk) 20:36, 21 July 2024 (UTC)[reply]

Our articles state: "Length contraction is the phenomenon that a moving object's length is measured to be shorter than its proper length, which is the length as measured in the object's own rest frame." and "Time dilation is the difference in elapsed time as measured by two clocks, either because of a relative velocity between them (special relativity), or a difference in gravitational potential between their locations (general relativity). When unspecified, "time dilation" usually refers to the effect due to velocity." Both descriptions refer to measurements of objects in relative motion. Modocc (talk) 21:05, 21 July 2024 (UTC)[reply]

As you quote, the lead of our article length contraction states: "Length contraction is the phenomenon that a moving object's length is measured to be shorter than its proper length", right? So the lead of this article attributes "length" to one "object", instead of attributing length measurement to two "rulers" - a stationary one and a moving one, right?

On the other hand, as you quote, the lead of our article time dilation states: "Time dilation is the difference in elapsed time as measured by two clocks", right? So the lead of this article attributes time measurement to two "clocks" - a stationary one and a moving one, instead of attributing time to one "object", right? My question was: How do you justify this asymmetry between the leads of those articles. HOTmag (talk) 21:46, 21 July 2024 (UTC)[reply]

The first article does not attribute "length" to an "object". Objects have lengths as a property and there are different ways to measure them. In addition, not all objects tick in any obvious way and measure time, so of course clocks are mentioned. Twins do attain different ages per the Twin paradox. :-) Modocc (talk) 22:01, 21 July 2024 (UTC)[reply]

The first article does not attribute "length" to an "object". Objects have lengths as a property. Maybe you didn't interpret me well. By "to attribute X to Y" I mean "to mention X as the property of Y". The expression "a person's feelings" attributes feelings to a person, just as the expression "an object's length" attributes "length" to an "object". Both lengths and feelings are properties attributed to an object/person - respectively, i.e. a length/feeling is a property - an object/person has - respectively.

not all objects - [mark and] tick [moments] in any obvious way - and measure time, so of course clocks are mentioned [in the lead of our article time dilation]. The same is true for rulers: Not all objects - mark and tick centimeters in any obvious way - and measure length, so rulers should apparently have been mentioned in the lead of our article length contraction. So why weren't they mentioned in that lead, even though they should've been mentioned in that lead, just as clocks are mentioned in the lead of our article time dilation? HOTmag (talk) 23:30, 21 July 2024 (UTC)[reply]

IMHO the articles' ledes are fine, as is, and they appear to be written in accordance with the literature and my understanding of it. Without going into what would amount to original research I don't believe I have anything more to contribute here today. Modocc (talk) 23:41, 21 July 2024 (UTC)[reply]