Wikipedia:Reference desk/Archives/Science/2019 October 5

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October 5

Natural law of Multiplication

The following discussion is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.

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The law of nature allows us to add, subtract and multiply only like groups unless per is involved in mixing of groups which has a useful meaning such as chairs per person or in the formula of v=s/t (m/s).

This means we can’t multiply 3 goats with 5 televisions, as it doesn’t have any useful meaning. If this is true then why mass is multiplied with velocity in making the formula of momentum. Did Newton not know about the aforementioned law of nature? This applies to all other similar equations of mathematics (physics, chemistry etc) where unlike groups are multiplied or added and subtracted.

I don’t see any difference when momentum = m v OR momentum = m + v as both equations are wrong mathematically.

Similarly, two or more different variables are also found in the form of multiplication in algebra unless it has a useful meaning as said e.g. x +y + xy=0Eclectic Eccentric Kamikaze (talk) 18:42, 4 October 2019 (UTC)

You say the "mixing of groups", as you call it, is acceptable when it has a "useful meaning". Well, multiplying mass and velocity has a useful meaning: that's exactly what momentum is. For that matter you can multiply (or divide) things even when the meaning is not useful: 3 goats times 5 televisions equals 15 goat televisions. That's not useful as far as we know, but if some future Newton ever finds a use for doing it, we know how. This is called dimensional algebra, and I am surprised to see that Wikipedia does not have an article on it.

Note that adding (or subtracting) is different from multiplying; you can't meaningfully 'add' mass and velocity. --76.69.116.4 (talk) 18:52, 4 October 2019 (UTC)

Dimensional analysis is the article "dimensional algebra" you look for Gem fr (talk) 23:56, 4 October 2019 (UTC)

Thanks for finding that! Could you or someone please create a redirect? It appears to me that "dimensional analysis" is the more general term while "dimensional algebra" refers to what the article calls "the factor-label method" and related operations, or something like that; some wording should be added to the article too, but I won't try to be precise enough to suggest what it should be. Here are some examples showing that the term "dimensional algebra" in use: [1]; [2] (page 3); [3] (original page 55 = rubber-stamped page 59 = PDF page 58); [4] (original page 5 = PDF page 12). --76.69.116.4 (talk) 06:43, 5 October 2019 (UTC)

What "law of nature" are you talking about? And by the way, does your car show "miles per hour"? ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:55, 4 October 2019 (UTC)

I appreciate your reply but IMPOV it's not unless we fool ourselves as it is unwise to say something like 15 goat .television. Although we are used to it to say N = kg.m/sec^2 but technically it's wrong and in reality, it has no meaning at all. The natural law of multiplication is called something universal fact. I think by dimensional algebra you mean dimensional analyses. Thanks, BTW.— Preceding unsigned comment added by Eclectic Eccentric Kamikaze (talk • contribs)

Your "law of nature" doesn't really make any sense unless you're using the definition of "multiply" that means "reproduce". Let's just take your example. If you have 3 goats and 5 televisions, you cannot add them, sure, since they are different objects. But multiplication is different. 3g x 5t = 15gt, algebraically. We could describe this as, "each of my three goats is carrying five televisions, so how many televisions do they have altogether?" You could even define 'gt' to be a new unit called "the goat television", which means a television carried by a goat. This results in 15gt having the same meaning whether you did 3g x 5t or 5g x 3t - in either case you have fifteen goat televisions. In the context of momentum equaling mv, that's literally just it's definition, and it makes the math of classical mechanics work, and that math continues to work even if you don't like it. Someguy1221 (talk) 20:50, 4 October 2019 (UTC)

I wouldn’t comment on what is in your mind but we just count either like groups or unlike groups together in your example.

If someone asks about the chattels (possession of how many goats and televisions altogether) then it would be 3 goats and 15 televisions not altogether 15 goat.television (meaningless to me). it can be 15 televisions, not 15 goat.televisions.

It also means if one goat can carry 5 televisions then how many goats will be required to carry 15 televisions? Similarly, if one goat can carry 5 televisions then 3 goats will carry 5x3 = 15 television – simple

It can be added too in order to find the total weight for transportation purposes.

Unlike groups can be multiplied (freedom of expression) but neither it has no real meaning nor technically correct. It seems correct to us to say N=kg.m/sec^2 because we are so so used to it but technically it is wrong to multiply acceleration and mass. Newton would have reconsidered if it was in his mind or someone objected while formulating his equation.

Whatever name (universal fact or natural law) we give it to but it means unlike groups can’t be multiplied unless per is involved. — Preceding unsigned comment added by Eclectic Eccentric Kamikaze (talk • contribs) 23:33, 4 October 2019 (UTC)

I'm not sure what you mean by "it has no real meaning nor technically correct". On what are you basing this conclusion? Where did your natural law come from? Did you learn it, or did you invent it? Can you give it a precise and unambiguous definition? And if your law results in these types of expressions having no meaning or being incorrect, what is the consequence of that? Someguy1221 (talk) 00:07, 5 October 2019 (UTC)

Is there a prize for someone who fancies himself smarter than Isaac Newton? ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:23, 5 October 2019 (UTC)

Momentum (see article) is defined as the product of the mass and velocity of an object i.e. :$\mathbf {p} =m\mathbf {v} ,$. That formula is not to be dismissed as somehow "wrong". The OP should ask if they doubt the properties of momentum. Introducing an incorrect, obviously different formula :$\mathbf {p} =m+\mathbf {v} ,$ is a Red herring that serves no rational purpose. DroneB (talk) 00:42, 5 October 2019 (UTC)

The discussion above is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.

Is there a relation between famine and skin darkening - scientifically?

According to the bible (for example: Lam 5:10) hunger causes darkness of skin (Hyper-pigmentation?). I want to ask from the side of the science: Is there a relation between famine and skin darkening? ThePupil (talk) 03:14, 5 October 2019 (UTC)

Not in general, but perhaps there was on Franklin's lost expedition, where lead from lead cans may have caused lead poisoning concurrent with starvation, darkening their bodies: [5]. There are other possible explanations, too. SinisterLefty (talk) 03:26, 5 October 2019 (UTC)

Not consistently, but it can happen depending on the circumstances. Long term lack of niacin causes pellagra, whose symptoms can include skin darkening, though it can also cause skin to appear lighter due to peeling. It is worth noting that modern English translations of Lam 5:10 directly from the Masoretic Text do not refer to blackened skin. However, Lam 4:8 and Job 30:30 are translated to refer to blackened skin. But in context, this is a metaphor for the "burning hunger" felt by someone who is starving, as if their skin has literally charred from the heat. Someguy1221 (talk) 03:50, 5 October 2019 (UTC)

[Edit conflict] Aside from any more complicated medical effects, in times of famine members of an iron-age culture such as the one under discussion would likely spend more time outdoors, looking for food, than they would spend in times of plenty, leading to more tanning.

Aside from that, the effects of starvation can indeed lead to skin darkening. For example in The Effects of Lack of Food By W.R. Aykroyd, 'The Conquest of Famine', Chapter 2, Summarized by Josef Skoldeberg we read that, amongst other signs: "The skin becomes dry and inelastic. Dark pigmentation can start to appear on the face and trunk, it is probably caused by a glandular disturbance."

In Kwashiorkor on the NHS website, 'Symptoms of kwashiorkor' include "red, inflamed patches of skin that darken and peel or split open." {The poster formerly known as 87.81.230.195} 2.121.161.82 (talk) 04:02, 5 October 2019 (UTC)