Wikipedia:Reference desk/Archives/Science/2018 January 5

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January 5

House of mirrors lighting

Both rooms have one hanging light in the centre.

• Room 1: Four walls, all painted white

• Room 2: Four walls, two white facing each other, two mirrored

If you're sitting in the middle reading a paper, which has better lighting?

Anna Frodesiak (talk) 11:37, 5 January 2018 (UTC)

"Better" is subjective. As such, the white paint.

I have to assume that "one hanging light" is reasonably modern, thus powerful (whether it's probably incandescent or maybe LED). We're thus concerned about more factors than simple total light levels. This would be different if it were an oil lamp.

As such, evenness of lighting becomes much more of a factor than total luminance. In particular, the avoidance of glare and "hot spots". A mirror will give specular reflection, thus glare. White paint will give diffuse reflection, thus avoiding it. The albedo of the white paint can be reasonably high, so the lost luminance is inconsequential.

In general for lighting design, unless deliberate, don't have simple paths from light source to eye via a single mirror. They're distracting. If this is needed to get the luminance high enough (even for reflected sunlight), allow for a diffuse reflection diffuser somewhere too. Andy Dingley (talk) 11:57, 5 January 2018 (UTC)

If you care about such things, we have a decent article about the integrating sphere, an instrument designed to get light "even". Tigraan^{Click here to contact me} 16:27, 5 January 2018 (UTC)

I actually have such a thing (home made) in the workshop. I make lighting, it's hard to judge some things (like the latest in cheap LED lamps) without one. Calibrating it is impossible though! Andy Dingley (talk) 20:28, 5 January 2018 (UTC)

If you're purely asking about how much light will be absorbed, then the mirror room will be brighter. White paint has a Light reflectance value in the high 70s or low 80s (example), but mirrors are typically over 90%.

I think I'd probably prefer to read in the white room, though. The mirror room will be brighter on average but it might not be lit evenly and it might be hard to find a spot where there aren't weird shadows or reflections playing across your paper.ApLundell (talk) 16:37, 5 January 2018 (UTC)

Indeed.

We fondly believe in the fable
that luxmeters cannot lie;
forgetting: one lux on the table
is better than ten in the eye.

— "DE LUX: A general rule." Grooks 5, Piet Hein, 1973.

TenOfAllTrades(talk) 23:37, 5 January 2018 (UTC)

• It depends on the floor and ceiling. If they are black, they will absorb a lot of the light before it has the chance to reach the reader. If they are white, the two rooms are essentially equivalent. Looie496 (talk) 23:34, 5 January 2018 (UTC)

I'm so sorry. I wasn't clear. The thing I'm after is, when there is a facing mirror thing, you know, where facing mirrored walls show that image of yourself again and again smaller and smaller off into the distance? So, the light in the room will be shown many times. Does that make the person in the room have more light or less? Anna Frodesiak (talk) 23:38, 5 January 2018 (UTC)

It will not multiply the light a zillion times until you're blinded, no.

Most mirrors will reflect about 90-98% of the light that hits it, while a white wall will only reflect about 75-80%.

Whether it reflects it in a specular way (like a mirror) so you can still see the image, or in a diffuse even way (like a white wall) , doesn't effect the total amount of light in the room.

So, the mirror room might be slightly brighter, but not for exactly the reason you're imagining.

ApLundell (talk) 23:55, 5 January 2018 (UTC)

Thank you all! Anna Frodesiak (talk) 19:30, 6 January 2018 (UTC)

Cat questions.

Do cats take care of their parents when their parents are old?

Anyone own have cats that lived to death and lived with their kittens, what do their children act when their parents are about to die, do they just sit around and stare? And what about old cats in the wild, do they have young cats look out for them? The Internet and Wikipedia is full of articles on cats taking care of their kittens, but I could hardly find anything about taking care of their parents.

I also wondering if father cats can take care of or raise their kittens, like if you put the mother away. I do know in the wild, female cats can live together and raise each other's kittens, but male cats do not. 12.204.64.35 (talk) 17:31, 5 January 2018 (UTC).

No, they do not take care of their parents. When they become adults they treat their parents similar to any other cats. And they do just stare when they parents die. Ruslik_Zero 20:02, 5 January 2018 (UTC)

Think that is a bit over simplistic. Young hunter cats bring home some of their kill back to the den for the benefits of young kittens and others (which includes older cats). As to what they do when an old cat nears the end, it is no different to their behaviour toward humans. Cat predicts 50 deaths in RI nursing home. Staring is effectively... 'watching over' -which is exactly what humans do when 'watching over' relatives in the terminal stages of life. Toms may not appear to take an active role but their nature makes them act against threats to the propagation of their genes when the need arises (Pro re nata). They have claws and know how to use them ! Aspro (talk) 22:36, 5 January 2018 (UTC)

Aspro, do you have a cite for any of this behavior you're describing? It seems to contradict most of what the Cat article, and its sources, say about cat behavior. (Are you thinking of Lions?)

Cat fathers do not defend their children. Any suggestion that they do is completely wrong.

Toms don't even know their children. They don't stick around with the mother. (A single litter may have multiple fathers, anyway.)

I'm also very suspicious about the claim that cats will give food to other adult cats, and would like to see a citation for it. The fact that some cats give food to adult humans is a behavioral mystery exactly because they never do it among themselves.

In general, cats are solitary animals, and even when population density forces them to form packs they show virtually no cooperation. ApLundell (talk) 00:18, 6 January 2018 (UTC)

? Quote from article: “or trying to help their human as if feeding "an elderly cat, or an inept kitten"”. Etc. Also, when Top Cat is Top Cat he is also ensuring the success of his prodigy by being master of his territory but not by being there to change his kittens diapers ! Toms also bring home food. Finally: 'showing no co-operation'... View The Secret Life of the Cat which shows cats co-operating. They are solitary hunters but not solitary animals - big difference. Have you actual read this article or just skimmed through it, with eyes half closed, whilst taking a cat-nap? Aspro (talk) 01:17, 6 January 2018 (UTC)

You took the quotes out of context. Morris' hypothesis is just a hypothesis of one man and one that appears not to be confirmed: " Morris's hypothesis is inconsistent with the fact that male cats also bring home prey, despite males having negligible involvement with raising kittens". And BBC does claim anything like you said above. Ruslik_Zero 19:22, 6 January 2018 (UTC)

I did read the entire article, and some of the sources. I didn't just, as you seem to have done, cherry pick a few lines that mean something different when you take them out of context. That's why I was concerned with your original answer.

I read that article you just now linked from beginning to end, and can't find any assertion that there was any cooperation shown. (Even if there was, that was a show for public entertainment. The narratives are formed in the editing room.[1]) If you're claiming that cats cooperate and feed their elders, that's a surprising fact that contradicts both our article, and everything I know about cats, so I would like a real reference for it. (And then, ideally, I'd like for that information to be added to the article.)

ApLundell (talk) 22:54, 6 January 2018 (UTC)

Horizon (UK TV series) is not a public entertainment show. They do a lot of background research before presenting the current view of notable experts in the field. They have to, because they are not accountable to advertisers and sponsors (like Fox documentaries, etc) but to the BBC board. In that sense, Horizon is as RS as National Geographic documentaries if not more so. So can't see where your criticisms and unsupported pontifications are coming from unless you're being willingly ignorant of the nature of cats – which even 'you' can observe before your very own eyes. Aspro (talk) 21:37, 7 January 2018 (UTC)

If your claims are so self-evident, then surely you could, here on the reference desk, provide a reference? ApLundell (talk) 17:30, 8 January 2018 (UTC)

Private Eye was critical of the scientific value of the programme saying: “By all means, if the BBC wants to, make a series called The Secret Life of Cats; but don’t insult the history of television by branding it, however obliquely, as a Horizon”.[11] I'd also note that this [2] from one? of the science advisors which seems to mostly relate to tracking rather than claims about feeding elderly cats mentions how the person involved is still analysing the data, and it's clear this is after the programme has already broadcast. Not surprisingly since real science, unlike TV "science" often takes time. I'd also note that the only real comments in that interview that in any relate to inter-cat relations suggest anything but cooperation, instead mentioning maintaining territory given close proximity to others cats and time sharing. Incidentally, the only thing I could find related to elderly cats involving the show is this Daily Mail (i.e. non RS) commentary about one cat who was stealing food from another elderly cat [3]. Nil Einne (talk) 14:45, 10 January 2018 (UTC)

Private Eye is a satirical mag and has been sued more times than the infamous Daily Mail, so we can confidently set aside their esteemed critic of the program - If you know anything about Private Eye, they where simply having a dig at the BBC and the way it spends the license fee. They do it all the time against all organizations, because this is what a good satirical publication does. Nil Einne is correct in saying that the project that the Horizon program followed was focused tracking cats. As a necessary part of this, it also included life in their home domain – where they where seen to cooperate - as any cat owner witnesses (unless they only have solitary 'house' cat). Another misunderstanding that ApLundell appears to have, is that the BBC license fee does not cover scientific research, rather it provides a skilled documentary team to follow academics in 'their' research – not the BBC's. The televised documentary was naturally presented as a Horizon documentary – as it was recored by the Horizon team, which is a big difference from what ApLundell is suggesting ! It is really up to ApLundell to come up with reference to show common accepted knowledge and observations by cat owners is scientifically wrong. There is a similar example on Channel 4 where the work of archeologist was documented into a TV series. Am waiting a reply with bated breath... and be quick. It is about to roll off the top of the page. Aspro (talk) 18:05, 11 January 2018 (UTC)