Wikipedia:Reference desk/Archives/Science/2024 February 20

= February 20 =

The increasing role of relativistic effects in heavy elements, since the speed of the 1s electron is not far less than c (speed of light)
The increasing role of relativistic effects in heavy elements, since the speed of the 1s electron is not far less than c (speed of light). Thus if the reciprocal of the fine-structure constant is 299792458 rather than 137, then the physical properties and the chemical properties of the elements in the period 8 will be completely different? 125.230.19.122 (talk) 07:01, 20 February 2024 (UTC)
 * I suppose by changing α you really mean changing c, implicitly using atomic units. (See this Physics Stack Exchange answer for the subtleties involved in such "alternate-physics" discussions.) So this really amounts to increasing the speed of light until relativistic effects are no longer important. In that case, not only is period 8 probably completely different, but also differences should be noticeable in periods 6 and 7. Without relativistic effects, mercury would be solid at room temperature, and lead-acid batteries would not work (because relativistic effects stabilise PbII relative to PbIV; without them, Pb would be much more like Sn than it really is). Double sharp (talk) 07:56, 20 February 2024 (UTC)

steel flexture lifetime
I was watching this video when I noticed that at 0:30 they claim: "Infinite lifetime", "no friction, no wear".

I think this is a flexure mechanism, and I'm not too familiar with them. But I do know a little bit about springs, and springs have a finite design lifetime, because every time a spring is compressed fatigue is introduced. Springs "wear", in other words.

Since springs have a finite lifetime, and undergoes wear during operation, wouldn't the same principle apply to the device shown in the video? OptoFidelty (talk) 21:33, 20 February 2024 (UTC)


 * They also advertize their gear as "frictionless" on the very first frame, which I think is not physically possible. --Lambiam 01:22, 21 February 2024 (UTC)


 * According to Plasticity (physics) however, load should not exceed the yield strength associated with a given material for it to retain its plasticity. It's a simple rule that may be perhaps not practical to observe in most real-life situations; and it always ended in failure at some point in all situations I studied, but that might be a matter of scale. Then the video is about a product intended to be used in a very sterile, quiet, and, finally, previsible environment. Thus, the notion of fatigue as we know it must also have a subjective dimension in it in some way. --Askedonty (talk) 01:27, 21 February 2024 (UTC)


 * Steel has a so-called endurance limit for stress, and according to this there is no limit to the fatigue life if you stay under it. According to an experienced test engineer, this is more a result of poor test technique than physics. Ultimately if you keep flexing steel, migration of discontinuities will continue, they will form cracks and then it breaks. Sorry, no refs. Greglocock (talk) 08:24, 21 February 2024 (UTC)


 * I would be very cautious about any claims within this advert since, as far as I can see, it indirectly claims to be breaking the laws of physics. Electric fan and direct radiant heaters already convert well over 90% of their drawn electrical energy to heat, so the inferences that these devices can heat a room much more quickly ("in seconds" – how many seconds?) much more cheaply ("for pennies" – how many pennies?) than existing devices seem dubious. {The poster formerly known as 87.81.230.195} 176.24.45.226 (talk) 15:21, 22 February 2024 (UTC)
 * What advert are you talking about? The OP posted a video about a steel flex mechanism with no electric heater mentioned. Philvoids (talk) 21:06, 22 February 2024 (UTC)
 * That's odd! When I first clicked on it, I saw a YouTube ad I'd seen before for what is essentially a small electric hot-air blower that mounts directly on to a wall socket. I guess it must have been prefixed by YouTube to the actual video the OP was referencing. {The poster formerly known as 87.81.230.195} 176.24.45.226 (talk) 21:57, 24 February 2024 (UTC)


 * Plus heat pumps are far better at heating than directly converting electric currents into heat. NadVolum (talk) 22:50, 22 February 2024 (UTC)