I wonder if any of the more scientifically minded people on here could help me, please.
- Thread starter Horsa
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I know that blood pressure is measured in mm of Mercury or mmHg. I just wondered why. I know it has nothing to do with old thermometers. The link with the measurement & thermometers was that they're both medical instruments or measurements & they both mention mercury, 1 because of the measurement unit (mm of mercury) & the other 1 because it contained mercury that gave the temperature reading.
I have. What I wanted to know is why blood pressure was measured in mm of mercury as in what mercury has to do with the reading of blood pressure for the unit of measurement to be mm of mercury in the 1st place. I don't understand why you said mmHg is the old measurement because that would call millimetres, centimetres & metres when old measurements are in feet & inches.
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mmHg are old units. New units are Pascals. Metheorologists use hPa since ~20y (even in USA!). Before they used "milibars" (I don't even bother understanding that), and even before that, (until 1980s I think) they used mmHg. Hydrologists use Pascals (or KPa) and plumbers also follow, even though they used PSI (pound per inch) - an old US unit. I don't know when the switch in plumbing industry happened because I rarely talk to those guys - I do all plumbing maintenance in my house by myself. But when I call my water company recently to enquire about main pressure they offered two answers in PSI and in kPa.
Docs (or healthcare inductry in general) are 30-40y behind meteorologists (and even behind plumbers) in adaptating to the evolving units. They are pariahs here with respect to other professions. just like US is a pariah nation with their feet & miles while the world measures in metres and 10^3 order derivatives.
I hope that clarifies your understanding.
Thank you very much. I just wondered how you classed mmHg as an old measurement when mm, cm & m are new measures & inches & feet were old measurements but I get you now.
I'll revisit a couple of questions I asked & were answered. I've found the answers in the format I was expecting but Chris's information was very interesting anyway.
1. I asked how far away the sun was from us. The answer I found out depends on where the earth is when it's going around the sun because the earth's orbit isn't round but elliptical so the sun is between about 91 & 94 million miles away from us.
2. I also asked what was the diameter of the earth. The answer I found out depends on whether you want the diameter of the earth from pole to pole or along the equator as the earth is not a proper sphere but an oblate spheroid which is flattened out a bit at the top & bottom. The polar diameter is 7,900 miles & the equatorial diameter is 7,927 miles.
1. I asked how far away the sun was from us. The answer I found out depends on where the earth is when it's going around the sun because the earth's orbit isn't round but elliptical so the sun is between about 91 & 94 million miles away from us.
2. I also asked what was the diameter of the earth. The answer I found out depends on whether you want the diameter of the earth from pole to pole or along the equator as the earth is not a proper sphere but an oblate spheroid which is flattened out a bit at the top & bottom. The polar diameter is 7,900 miles & the equatorial diameter is 7,927 miles.
What are Rontgen Rays? N.B. there should be an umlaut over the o of Rontgen but I don't know how to type an umlaut.
The Northern pine is pinus sylvestris. 1 of the ancestors of the horse is equus sylvestris. What does sylvestris mean please? I'm just asking because I want to see the connection.
The Northern pine is pinus sylvestris. 1 of the ancestors of the horse is equus sylvestris. What does sylvestris mean please? I'm just asking because I want to see the connection.
When @mrzz & @Chris Koziarz 1st mentioned both Quantum mechanics & classical mechanics I automatically thought that cars & bicycles were going to be involved somewhere along the lines because I think mechanics & I automatically think of people repairing motor vehicles or bicycles & that doesn't interest me but I asked because I wanted to understand what was being said & I found what they had to say fascinating. I've just read a bit of my book which mentioned mechanical physics which seems interesting. I know I've had to ration my reading time to rest my eyes so I've tried to make my reading count as well as watching more t.v., making hats & drawing instead of just reading & typing so much & doing what I need to do. I've even been going to bed early. I overdid it yesterday though & ended up with the Mother of all headaches which I've still got now. I wonder if 1 of you could answer my questions please.
- What are kinematics?
- What are centrodes?
- What are axodes?
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mrzz
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@Horsa, I will drop just a few lines... as you know I tend to enjoy more conceptual discussions than straight forward q&a, so I will focus on the conceptual misunderstanding you made (or just mentioned, but anyway) in the build up of your question.
When we mentioned classical and quantum mechanics, we were talking about two branches of physics which are not exactly what people mean when they use the term "mechanics" in a more day-to-day sense. "Classical Mechanics", in a theoretical physics sense, deals with movement of physical bodies (a lot of times assumed to be particles). It is basically the way Isaac Newton (and also Leibniz) found out to describe a particle's motion -- the famous three laws. If you add a lot more complexity, you get to describe the movement of actual physical three dimensional bodies. This of course has connections with the common use of the word "mechanics", but it is kind of a linguistic accident that the two words are exactly the same.
By the way, answering 1, kinematics is a part of classical mechanics -- it deals with the description of movement, ignoring its causes. I guess we discussed what quantum mechanics is some posts above. Sorry if this post is a bit more clumsy than usual...
When we mentioned classical and quantum mechanics, we were talking about two branches of physics which are not exactly what people mean when they use the term "mechanics" in a more day-to-day sense. "Classical Mechanics", in a theoretical physics sense, deals with movement of physical bodies (a lot of times assumed to be particles). It is basically the way Isaac Newton (and also Leibniz) found out to describe a particle's motion -- the famous three laws. If you add a lot more complexity, you get to describe the movement of actual physical three dimensional bodies. This of course has connections with the common use of the word "mechanics", but it is kind of a linguistic accident that the two words are exactly the same.
By the way, answering 1, kinematics is a part of classical mechanics -- it deals with the description of movement, ignoring its causes. I guess we discussed what quantum mechanics is some posts above. Sorry if this post is a bit more clumsy than usual...
Thank you very much, Mrzz. I know. You prefer to have either proper conversations, a vent or a laugh & joke, however I have a dispute about you calling Q & A sessions straight-forward which is that you asked me earlier to answer easy questions as the questions I were asking were hard (If I asked hard questions how can Q & A be straight-forward & some of the answers given as you rightly mentioned above took a bit of thought to understand so how can Q & A be straight-forward?) & you told me to carry on asking questions as the questions were generating interesting answers therefore the more questions the more interesting the answers are probably going to be. However, I realise that I've asked more questions than an inquisitive 6 year old & that like you've hinted a few times before I'm more than capable of finding out for myself & have the resources available to me in order to do that so should be doing so.
I know that now as you explained a bit since. I was just telling you what I thought originally. I already knew about the laws of motion & about particles as I learnt about them in science at school. Why is the same word used for 2 completely different things? I also thought I had to explain why I was asking the questions & thought that you'd both like to know that you'd inspired me.
You did. Thank you very much. It's o.k. I understand. I'm very sorry for bothering you at a troubling & busy time for you when I should be more understanding. I'm also sorry for being so inconsiderate recently. I hope everything goes as well as it possibly can do under the circumstances & that you & yours are safe & well. I also hope that you get everything done you want & need to do & have time to relax & have fun too. Take care.
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Rontgen rays is the different name for x-rays: the electromagnetic rays from about 10 nanometers and shorter: sitting above visible & UV light rays in EM spectrum. Sometimes we use former name to honour Wilhelm Röntgen who discovered them, but most people want simplicity and avoidance of your spelling/typing problem, so they simply use the term x-ray which means exactly the same.
Read this:
https://en.wikipedia.org/wiki/X-ray
which will remind you where (medical imaging/airport security) and what specific length of x-rays are used. Why certain tissues are penetrable and other tissues (bones) are not, health impacts, etc.
You can ask further questions if you want because my knowledge in this field is decent, e.g. my workspace have been conducting research into using x-ray interference to obtain more precise medical images with less dosage, Interesting stuff.
sylvestris means "coming from a forest". So, it's no surprise that the most common conifer tree in the Eurasian continent - Scots pine - is called pinus sylvestris. BTW, I read that in Britain, esp N part (Scotland) Scots pine is ironically, rather rare and deciduous trees prevail in forests therein, correct?.
So, by induction, equus sylvestris should mean "horse coming from a forest", perhaps such name makes sense?
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Yes, changes in Earth's orbit are all interesting facts, having big implications on Earth's climate: roughly 100ky cycles (so called Millankovic cycles). My knowledge is quite good in this field but the details are perhaps out of scope here.
I wonder why you using miles (like an old-timer Brit or American that you're not) while most of the world uses kms. (I use Mm - mega-metres - Gm, Tm, etc but that's my personal computer science bias). Perhaps your miles are simply an outcome that you just quote the sources your search engine finds, and with "English US" settings, your search engine brings mostly American web pages?
It just means your teacher is very smart and considerate by not denigrating left-handedness as my primary school teachers, long ago in rural Poland, used to be. I hated them back then and now regret both my hatred and that I missed a wonderful emotion of life admiration that a healthy pupil-teacher relationship excites. I wish you that experience with your knitting teacher.
I don't know much about these particular birds but I note they belong to different families (Muscicapidae and Turdidae), so the common name "Robin" for both is just coincidence and more precisely ignorance of early taxonomists describing American wildlife.
Identical case in my part of the world is a common name "Australian Magpie" (Gymnorhina tibicen) which belongs to Artamidae family (i.e. butcherbird) & has nothing to do with European magpie (Pica pica) belonging to corvidae family (i.e. raven).
Thank you very much for the information. It's fascinating.
I know why X-rays are used. I've had some at the hospital & dentists.
Do you think that there will ever be non-carcinogenic X-rays?
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Thank you very much for the information
I've been to the highlands of Scotland many times & the trees I saw in the forests were mainly pines & firs.
It does. Thank you very much.
Thank you very much for the information. It is fascinating.
I do use the new measurements sometimes but was taught in some old measurements & my friends & family use old measurements. I love antiques including books & read the antique books I've got. I don't do research on the internet unless forced but I read a lot. Most of what I say comes straight off the top of my head & I ask questions before looking things up using research as a last resort but if I'm doing research I normally do it the old way which means if I get my information from old books I use old measurements. I can read books for longer without taking a break as Health & Safety advises only being on a P.C. for 2 hours at a time + my internet is quite slow so I prefer to research the old way though sometimes I give myself a bit of a bit of a break & watch T.V. series I've got on D.V.D.'s with the answer on. It's the lazy way I know but I work myself so hard I need to give myself a bit of a break sometimes. Mind you, I remember doing dictation class at school & when I do research from T.V. series I've got on D.V.D. I dictate then I look through, pick out what I really need to know & copy that out then re-read to make sense of it before paraphrasing it & putting a bit of me into it. I don't just quote without acknowledging & using quotation marks.
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Mother taught me. I'm right-handed. I write & do everything else with my right hand.