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November 28

Are there any volatile gold compounds?

Title. Let's say "boiling point under 500°C" counts (as long as it actually boils and doesn't decompose). :) Double sharp (talk) 03:11, 28 November 2024 (UTC)[reply]

Gold(III) fluoride apparently undergoes "sublimation above 300 °C". Tracing the dewiki article's data suggests this comes from CRC 10th ed. doi:10.1016/0022-328X(87)80355-8 is a lead article about volatile gold compounds, but these (and others I found) are generally about transferring as a vapor for CVD, nanoparticle formation, or other short-timeframe processes, so probably low pressure and maybe not highly stable in the vapor phase. DMacks (talk) 03:58, 28 November 2024 (UTC)[reply]

The compound [Me₂AuOSiMe₃]₂ sublimes at 40 °C (0.001 mmHg) without decomposition. (doi:10.1002/anie.196706831) --Leiem (talk) 04:24, 28 November 2024 (UTC)[reply]

Closure, does it exist in physics?

In mathematics, closures are pretty common, e.g. a sum of positive/negative numbers is a positive/negative sum - respectively, and a space of two/three dimensional bodies is a two/three dimensional space - respectively, and so forth.

I wonder if closures also exist in physics, i.e. when the closed properties are physical rather than mathematical, i.e. I'm not interested in applying mathematical properties - like a sum or a space - in physics: e.g. when we say that "a sum of two electric forces is an electric force": It's a bad example for closures in physics, because a "sum" is a methematical property, whereas I'm only interested in purely physical examples.

The above-mentioned example for closures in physics is bad also for another reason: Whereas there is a concrete difference between an electric field and a magnetic field (e.g. by how they influence a stationary body), there is no concrete difference between an electric force and a magnetic force: They influence a given body by the same way, e.g. if their value is 1 kg N they will accelerate a given body by the same acceleration, so the only difference (if at all) between an electric force and a magnetic force and a gravitaional force is "historical", i.e. it only tells us whether the source of that force, was an electric field or a magnetic field or a gravitational field.

HOTmag (talk) 08:35, 28 November 2024 (UTC)[reply]

1 kg is the unit of mass and not of force for which physicists have another unit Newton (the force to accelerate 1 kg at 1 m/s²⁾ and your Greengrocer uses a scale that displays W(kg)=mg. Mathematical Addition (or summation), whether of scalar or vector quantities, is defined in abstract symbols. Those symbols may represent any physically real quantities and the summation result is equally real. That is no set-limited exercise or example-setting in Set theory and physical science is well enough aware that that there can be four (not just 3) fundamental forces viz. gravity, electromagnetism, weak interaction and strong interaction that act in combination and cease to be explicitly separable in the result. Philvoids (talk) 13:40, 28 November 2024 (UTC)[reply]

Yes, I really meant Newton (sometimes people tend to replace weight by mass, but this mistake is so widespread - mainly in daily life, that it should be forgiven when readers understand what the speaker meant). Additionally I didn't want to mention the other forces becuase they are not useful in daily life.

As for your main response, I didn't fully understand the bottom lime: Do you eventually claim that there don't exist purley physical closures (although there are purely mathematical closures)? HOTmag (talk) 14:08, 28 November 2024 (UTC)[reply]

Are Symmetry (physics) and Conservation law what you're after?

Not necessarily, but could you give a concrete example? HOTmag (talk) 14:27, 28 November 2024 (UTC)[reply]

In mathematics, a closure is always the closure if a set. The set of positive numbers is closed under addition. The concept of closure requires the notion of an operation such as addition that can be performed on elements of the set. What is closed is not a property but a set. --Lambiam 15:08, 28 November 2024 (UTC)[reply]

A property is usually interpreted as a set. E.g. the property "Asian" is the set of all Asian objects, and when we say that a given object is Asian we only mean that it belongs to that set.

Here is a surprising example of closure: "a space of two/three dimensional objects is a two/three dimensional space - respectively". It really points at a closure because: on one hand, the operation is "to collect objects in a space": the result of this operation is the space in which those object are collected. On the other hand, the property is "two/three dimensional" (choose one option): this property is represented by the set of all two/three dimensional objects (respectively).

My original question was, if there was any physical property (i.e. a set of physical objects sharing an indentical physical property), closed under a physical operation. HOTmag (talk) 17:59, 28 November 2024 (UTC)[reply]

Do you mean, in lay terms, 'is there any physical property of a physical object that can never be changed?' (I assume by a physical process – I don't think changing the host's accident by transubstantiation counts.)

I'd guess that Dark matter can't be changed into Baryonic matter and vice versa, but I might well be wrong. {The poster formerly known as 87.81.230.195} 94.1.211.243 (talk) 10:01, 29 November 2024 (UTC)[reply]

Active galaxys

What are active galaxies? NoBrainFound (talk) 17:29, 28 November 2024 (UTC)[reply]

See Active galactic nucleus, first paragraph. Perhaps there should be a redirect for this topic. -- Verbarson ^talk_edits 18:11, 28 November 2024 (UTC)[reply]

Oh. There is one: Active galaxy. It's a bit annoying that the search bar does the redirect invisibly. -- Verbarson ^talk_edits 19:10, 28 November 2024 (UTC)[reply]