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January 1

Oxidation states of noble gases

Do argon monofluoride, krypton monofluoride, and xenon monochloride have the noble gas in +1 oxidation state? I’m not sure do exciplexes are valid noble gas compounds. Nucleus hydro elemon (talk) 04:53, 1 January 2024 (UTC)[reply]

I would say yes, they are formally Ng(I), but at the same time I think exciplexes are not quite the same thing as normal compounds indeed. Double sharp (talk) 05:29, 1 January 2024 (UTC)[reply]

I can't find a ref for anything special about oxidation-state analysis of exciplexes, and given they are a bound state (molecular-orbital-like electronic analysis) I would not expect there to be any difference either. However, is there anything unusual about oxidation-state analysis of electronically excited states in general? DMacks (talk) 06:39, 1 January 2024 (UTC)[reply]

My problem with treating exciplexes on the same footing as normal noble gas compounds is just my philosophical taste, to be honest. It has nothing to do with oxidation state analysis not working: it works just as well to my knowledge (though it's not something I think about very often). It has more to do with the fact that excited He and Ne for example do not have closed-shell configurations at all, so there is no reason to expect them to be inert. So while they are indeed noble gas compounds in some sense, they lose part of what makes it impressive to force a noble gas into compounds, and I'd rather make a distinction between the bonded excited states of He₂ and predicted species with chemical bonds to ground-state He. Same story with positive oxidation states of F. Double sharp (talk) 08:39, 1 January 2024 (UTC)[reply]

New Year's countdown broadcast delay ≈ 11 seconds ??

I know about the seven second delay in TV broadcasting. So, why is it that, when watching the countdown for the Times Square Ball to drop tonight, I heard my clock strike midnight when the countdown was at 12 seconds? I know what you're thinking, and I got on my computer to check the time as my clock struck one, and my computer said it was 00:59:59. My computer was within 0.3 second of the correct time according to both [time.gov] and [time.is], so I will say that the countdown as it appeared on my TV was 11 seconds out.

Did they lengthen the seven-second delay to eleven seconds or something? Or does the fact that TV is now digital account for the missing four seconds? Or what? 32.217.240.174 (talk) 06:28, 1 January 2024 (UTC)[reply]

Yes the extra delay is due to various factors in the digital technology. As well as just taking time to send bits out and fill buffers etc they also have a lot of redundancy and error correction which depends on delaying the final picture a bit so glitches can be fixed before anything is displayed. I guess you could call it the digital version of the seven second delay so you get a clean signal :-) NadVolum (talk) 11:24, 1 January 2024 (UTC)[reply]

There are tons of potential bottlenecks here. For starters how were you receiving the TV program? Were you watching over-the-air TV via a digital antenna connected to the TV system? Or some other means? Slowking Man (talk) 04:50, 4 January 2024 (UTC)[reply]

Walking in partial gravity

This question from 2019 inspired me to ask: approximately what's the minimum gravity that humans could actually recognisably walk in (as opposed to jumping off the ground and floating for an awkwardly long time before going back down)? Is Luna's gravity (0.165g) enough? Triton's (0.080g)? Umbriel's (0.023g)?

(Assuming a hypothetical space station with an Earthlike environment rotating for partial gravity, to avoid having to factor in the spacesuit. So, while Apollo is a useful datapoint, it does not quite answer the question.) Double sharp (talk) 08:49, 1 January 2024 (UTC)[reply]

Define walk. I don't think a definite answer is possible. We habitually exert a downward force when we walk, so it's actually easier for someone unaccustomed to less gravity to jump. It's perfectly possible to "walk" on the moon, with a bit of practice, though it might look more like a shuffle at first. Shantavira|^{feed me} 09:32, 1 January 2024 (UTC)[reply]

Well, let's say it's "walking" when you always have at least one foot on the ground. I suppose there's probably an intermediate zone where you can technically walk, but it's not the best way to get around. Double sharp (talk) 09:32, 1 January 2024 (UTC)[reply]

Friction is an issue. Assuming dry friction, the backward force a walker can exert when taking a step is proportional to their weight. In microgravity it is very low. On the surface of the Moon, no air resistance needs to be overcome, so once a certain speed is reached it can be maintained and gradually be increased. In an air-filled space station, however, there is a maximal attainable speed, which depends on the coefficient of friction between the walker's footwear (or foot if barefoot) and the flooring, as well as on the aerodynamic properties of tthe walker. --Lambiam 10:57, 1 January 2024 (UTC)[reply]

Let's assume that the most comfortable walking speed is when your legs move at their natural frequency, acting as a pendulum. Then your speed is proportional to the square root of gravity. Air resistance grows with the square of velocity, so when walking at your most comfortable speed, the ratio of air drag to weight is independent of gravity. Of course, the main source of drag in an ordinary walk on a hard and level surface is the viscosity of your own bodily fluids.

I don't think there's a gravity below which walking becomes impossible. With reducing gravity, walking gets increasingly slower, whilst hopping gets easier. At some point, hopping is more practical than walking. For the Apollo astronauts, that was the case. Their spacesuits contributed to that, but experiments on Earth with people moving whilst 5/6 suspended by ropes also indicate that hopping is preferred. PiusImpavidus (talk) 11:11, 2 January 2024 (UTC)[reply]

Below a certain gravity just exhaling through their nose will send the walker up like a rocket. --Lambiam 15:14, 2 January 2024 (UTC)[reply]

Relevant interesting paper about walking on Mars. As expected from PiusImpavidus' comment, the speed is about √0.378 times that of Earth walking, as Martian gravity is about 0.378g. Though explicit simulations of lunar gravity suggest that the model doesn't work so well that low (0.165g). I still wonder about ultra-low cases like Ceres (0.029g). Double sharp (talk) 15:34, 2 January 2024 (UTC)[reply]

Also, apparently WP:WHAAOE: Transition from walking to running. Double sharp (talk) 15:42, 2 January 2024 (UTC)[reply]