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    surbitonsurbiton Posts: 13,549
    Fishing said:

    It's crap of course.

    I make it at LEAST Empire 4.0:

    - first empire was the American colonies, lost in 1783
    - second empire was the Indian/African/Australasian/Canadian show, which we shed after 1947
    - third empire was the post-war Commonwealth, which many of the second empire joined.

    And that's not counting medieval and early modern rule in Ireland, etc.
    Someone should tell Sam Coates of "The Times" that the correct spelling is "their" and not there in the context he is using.

    It used to be the newspaper for records.
  • Options
    MonikerDiCanioMonikerDiCanio Posts: 5,792

    Fishing said:

    It's crap of course.

    I make it at LEAST Empire 4.0:

    - first empire was the American colonies, lost in 1783
    - second empire was the Indian/African/Australasian/Canadian show, which we shed after 1947
    - third empire was the post-war Commonwealth, which many of the second empire joined.

    And that's not counting medieval and early modern rule in Ireland, etc.
    Empire Vista?
    Already done. AKA The Darien Scheme.
  • Options
    RobDRobD Posts: 58,985
    surbiton said:

    Fishing said:

    It's crap of course.

    I make it at LEAST Empire 4.0:

    - first empire was the American colonies, lost in 1783
    - second empire was the Indian/African/Australasian/Canadian show, which we shed after 1947
    - third empire was the post-war Commonwealth, which many of the second empire joined.

    And that's not counting medieval and early modern rule in Ireland, etc.
    Someone should tell Sam Coates of "The Times" that the correct spelling is "their" and not there in the context he is using.

    It used to be the newspaper for records.
    Can't believe you complained about that and did not mention "hv" :p
  • Options
    OmniumOmnium Posts: 9,796

    Mrs C, boo hiss to metric monstrosities, huzzah for imperial measurements!

    I would hate to do science or technology in imperial units. Foot-pounds per yard? Poundals per square inch?
    Astronomers in particular make up their own units. What's 200 solar masses in kilograms?

    And WTF is "kilo" doing in a base unit anyway?
    Sorry, but astronomers are metric. They use megaparsecs, kiloparsecs, millarcseconds, etc.

    200 solar masses = 3.978 x10^32 kg
    A mega-furlong is metric in that sense. Astronomical units aren't SI units, which I guess most people would regard as 'metric'. There's such a huge gap between these measures though that it isn't really a concern - your hallway isn't going to be fitted for carpet in AU.

    They're quite poor units anyway - the distance between the earth and the sun changes, as does the mass of the sun.
  • Options
    Carolus_RexCarolus_Rex Posts: 1,414

    Mrs C, the Babylonian mathematicians gave use units of 12, handily divisible by 6, 4, 3, 2, as well as the 360 degrees of a circle, (hence nearly the same number of days in a year), 24 hours in a day and so on.

    Edited extra bit: the past provides countless lessons that could be applied for future advantage.

    If Blair had read Thucydides' History of the Peloponnesian War he might have realised invading Iraq made as much sense as the Athenian invasion of Sicily.

    Interestingly, Donald Kagan in the third volume of his history of the war makes an interesting case for the invasion of Sicily. As I recall the argument is that there were sound strategic reasons for it, but sending too many ships and men and dividing the command between Nicias, Alcibiades Lamachus doomed it to failure.
  • Options
    rottenboroughrottenborough Posts: 58,277

    Mr. Borough, quarterly returns (mandatory digital) is bloody stupid. Why Osborne wanted them and Hammond didn't axe them is beyond me.

    I assume the idea is being driven by HMRC itself rather than Hammond to be honest. iirc there is supposed to be some extra tax collected as it will be harder to hide holes and discrepancies. But that is a forecast.
  • Options
    Beverley_CBeverley_C Posts: 6,256
    edited March 2017
    RobD said:


    A parsec is the distance at which 1 au subtends 1 arcsecond on the sky. They are intimately linked.

    I am not denying that. What I am saying is that if I need to use parsecs then there is virtually point to using AUs for that measurement. If something is 2.2 M parsecs away then I will say that rather than 453,783,000,000 AUs

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    Ishmael_ZIshmael_Z Posts: 8,981

    Ishmael_Z said:

    Mrs C, boo hiss to metric monstrosities, huzzah for imperial measurements!

    I would hate to do science or technology in imperial units. Foot-pounds per yard? Poundals per square inch?
    Astronomers in particular make up their own units. What's 200 solar masses in kilograms?

    And WTF is "kilo" doing in a base unit anyway?
    Sorry, but astronomers are metric. They use megaparsecs, kiloparsecs, millarcseconds, etc.

    200 solar masses = 3.978 x10^32 kg
    But parsecs are parallax seconds of arc, 60 of them to a minute of arc, and the distance underlying the parallax is the A.U., which is a feature of the real world and it's irrelevant how you measure it. so mega- and kiloparsecs are hideous hybrids.
    On the scale at which you start using parsecs, the AU is virtually unnoticeable, so they matter very little.

    On a side issue, there are approximately 63,000 AU in a lightyear and approximately 63,000 inches in a mile, so if you make scale the distance from the Earth to the Sun as one inch, then distances to the stars in lightyears translates to miles so the nearest start would be 4.3 miles away :)

    You what? The AU is baked in to the definition of a parsec. That's like saying it doesn't much matter how well we understand how atoms work given how small they are.
  • Options
    surbitonsurbiton Posts: 13,549
    Ishmael_Z said:

    Mrs C, boo hiss to metric monstrosities, huzzah for imperial measurements!

    I would hate to do science or technology in imperial units. Foot-pounds per yard? Poundals per square inch?
    Astronomers in particular make up their own units. What's 200 solar masses in kilograms?

    And WTF is "kilo" doing in a base unit anyway?
    Sorry, but astronomers are metric. They use megaparsecs, kiloparsecs, millarcseconds, etc.

    200 solar masses = 3.978 x10^32 kg
    But parsecs are parallax seconds of arc, 60 of them to a minute of arc, and the distance underlying the parallax is the A.U., which is a feature of the real world and it's irrelevant how you measure it. so mega- and kiloparsecs are hideous hybrids.
    The AU is understandable to most who are interested in such things unless we are talking about a near object like our moon which is usually referred to as 250k miles or 400k km away.

    When New Horizons reached Pluto, I think it was 38 AU from the sun [ for those who are unaware, AU = Distance from the Sun to Earth ]. It is something one can relate to.

    I would have thought parsecs refer to how much "angle" the object covers.
  • Options
    RobDRobD Posts: 58,985
    edited March 2017
    Omnium said:

    Mrs C, boo hiss to metric monstrosities, huzzah for imperial measurements!

    I would hate to do science or technology in imperial units. Foot-pounds per yard? Poundals per square inch?
    Astronomers in particular make up their own units. What's 200 solar masses in kilograms?

    And WTF is "kilo" doing in a base unit anyway?
    Sorry, but astronomers are metric. They use megaparsecs, kiloparsecs, millarcseconds, etc.

    200 solar masses = 3.978 x10^32 kg
    A mega-furlong is metric in that sense. Astronomical units aren't SI units, which I guess most people would regard as 'metric'. There's such a huge gap between these measures though that it isn't really a concern - your hallway isn't going to be fitted for carpet in AU.

    They're quite poor units anyway - the distance between the earth and the sun changes, as does the mass of the sun.
    The au has been detached from the Earth-Sun orbit, and now has a fixed value. While the mass of the Sun is changing, it is only at a very small rate relative to its total mass.
  • Options
    Beverley_CBeverley_C Posts: 6,256
    Omnium said:

    Mrs C, boo hiss to metric monstrosities, huzzah for imperial measurements!

    I would hate to do science or technology in imperial units. Foot-pounds per yard? Poundals per square inch?
    Astronomers in particular make up their own units. What's 200 solar masses in kilograms?

    And WTF is "kilo" doing in a base unit anyway?
    Sorry, but astronomers are metric. They use megaparsecs, kiloparsecs, millarcseconds, etc.

    200 solar masses = 3.978 x10^32 kg
    A mega-furlong is metric in that sense. Astronomical units aren't SI units, which I guess most people would regard as 'metric'. There's such a huge gap between these measures though that it isn't really a concern - your hallway isn't going to be fitted for carpet in AU.

    They're quite poor units anyway - the distance between the earth and the sun changes, as does the mass of the sun.
    :+1:

    A bit like the original definition of Fahrenheit - 100F was the temperature of Mrs Fahrenheit's armpit. This caused a standards crisis on the date of her demise :D
  • Options
    RobDRobD Posts: 58,985

    RobD said:


    A parsec is the distance at which 1 au subtends 1 arcsecond on the sky. They are intimately linked.

    I am not denying that. What I am saying is that if I need to use parsecs then there is virtually point to using AUs for that measurement. If something is 2.2 M parsecs away then I will say that rather than 453,783,000,000 AUs

    But that doesn't change the fact it is the basis of the parsec ;)
  • Options
    Beverley_CBeverley_C Posts: 6,256
    surbiton said:

    I would have thought parsecs refer to how much "angle" the object covers.

    The parsec is useful because it can be used in direct measurement. If star shows an annual parallax of 0.2 arcsecs then it is 1 / 0.2 = 5 parsecs away

  • Options
    Ishmael_ZIshmael_Z Posts: 8,981

    Mrs C, the Babylonian mathematicians gave use units of 12, handily divisible by 6, 4, 3, 2, as well as the 360 degrees of a circle, (hence nearly the same number of days in a year), 24 hours in a day and so on.

    Edited extra bit: the past provides countless lessons that could be applied for future advantage.

    If Blair had read Thucydides' History of the Peloponnesian War he might have realised invading Iraq made as much sense as the Athenian invasion of Sicily.

    Two-thirds relevantly, place these (currently ordered alphabetically) in size order: the Peloponnese, Sicily, Wales. No googling.
  • Options
    surbitonsurbiton Posts: 13,549
    RobD said:

    surbiton said:

    Fishing said:

    It's crap of course.

    I make it at LEAST Empire 4.0:

    - first empire was the American colonies, lost in 1783
    - second empire was the Indian/African/Australasian/Canadian show, which we shed after 1947
    - third empire was the post-war Commonwealth, which many of the second empire joined.

    And that's not counting medieval and early modern rule in Ireland, etc.
    Someone should tell Sam Coates of "The Times" that the correct spelling is "their" and not there in the context he is using.

    It used to be the newspaper for records.
    Can't believe you complained about that and did not mention "hv" :p
    Isn't that how it is spelled ? No, I have this irrational reaction to spell check words. Their/There, were/where. I have even seen No/know * and right / wright though for the last two examples I don't think spellchecking is responsible.
  • Options
    Carolus_RexCarolus_Rex Posts: 1,414
    Ishmael_Z said:

    Mrs C, the Babylonian mathematicians gave use units of 12, handily divisible by 6, 4, 3, 2, as well as the 360 degrees of a circle, (hence nearly the same number of days in a year), 24 hours in a day and so on.

    Edited extra bit: the past provides countless lessons that could be applied for future advantage.

    If Blair had read Thucydides' History of the Peloponnesian War he might have realised invading Iraq made as much sense as the Athenian invasion of Sicily.

    Two-thirds relevantly, place these (currently ordered alphabetically) in size order: the Peloponnese, Sicily, Wales. No googling.
    I would guess Sicily.
  • Options
    OmniumOmnium Posts: 9,796
    RobD said:

    Omnium said:

    Mrs C, boo hiss to metric monstrosities, huzzah for imperial measurements!

    I would hate to do science or technology in imperial units. Foot-pounds per yard? Poundals per square inch?
    Astronomers in particular make up their own units. What's 200 solar masses in kilograms?

    And WTF is "kilo" doing in a base unit anyway?
    Sorry, but astronomers are metric. They use megaparsecs, kiloparsecs, millarcseconds, etc.

    200 solar masses = 3.978 x10^32 kg
    A mega-furlong is metric in that sense. Astronomical units aren't SI units, which I guess most people would regard as 'metric'. There's such a huge gap between these measures though that it isn't really a concern - your hallway isn't going to be fitted for carpet in AU.

    They're quite poor units anyway - the distance between the earth and the sun changes, as does the mass of the sun.
    The au has been detached from the Earth-Sun orbit, and now has a fixed value. While the mass of the Sun is changing, it is only at a very small rate relative to its total mass.
    Ok so I presume the standard is defined as a number of metres. And thus a number of caesium spectral wavelengths, or whatever it is - but so far as I know you can't say 1 AU = 10^x metres where x is some nice integer - and if astronomical units were really 'metric' in the common sense of the world you would be able to.
  • Options
    Beverley_CBeverley_C Posts: 6,256
    RobD said:

    RobD said:


    A parsec is the distance at which 1 au subtends 1 arcsecond on the sky. They are intimately linked.

    I am not denying that. What I am saying is that if I need to use parsecs then there is virtually point to using AUs for that measurement. If something is 2.2 M parsecs away then I will say that rather than 453,783,000,000 AUs

    But that doesn't change the fact it is the basis of the parsec ;)
    *sigh*

    Yes... you correct. It is the basis of the parsec

    But nobody measures stellar distance in AUs
  • Options
    surbitonsurbiton Posts: 13,549

    surbiton said:

    I would have thought parsecs refer to how much "angle" the object covers.

    The parsec is useful because it can be used in direct measurement. If star shows an annual parallax of 0.2 arcsecs then it is 1 / 0.2 = 5 parsecs away

    I see. Trigonometry. But surely a star very, very far away even after 6 months will not reveal much movement, or am I wrong ?
  • Options
    RobDRobD Posts: 58,985

    RobD said:

    RobD said:


    A parsec is the distance at which 1 au subtends 1 arcsecond on the sky. They are intimately linked.

    I am not denying that. What I am saying is that if I need to use parsecs then there is virtually point to using AUs for that measurement. If something is 2.2 M parsecs away then I will say that rather than 453,783,000,000 AUs

    But that doesn't change the fact it is the basis of the parsec ;)
    *sigh*

    Yes... you correct. It is the basis of the parsec

    But nobody measures stellar distance in AUs
    Sure, but it doesn't make it metric just by sticking a mega in front of it...
  • Options
    Morris_DancerMorris_Dancer Posts: 60,994
    edited March 2017
    Mr. Rex, must admit I only have the single volume history by Kagan (still very good, mind).

    Mr. Z, utter guess but I'd say Wales, Peloponnese, Sicily.

    This sort of thing is not my strong point.

    Mr. D, sometimes call the hound, Meg-a-dog.
  • Options
    Ishmael_ZIshmael_Z Posts: 8,981
    surbiton said:

    Ishmael_Z said:

    Mrs C, boo hiss to metric monstrosities, huzzah for imperial measurements!

    I would hate to do science or technology in imperial units. Foot-pounds per yard? Poundals per square inch?
    Astronomers in particular make up their own units. What's 200 solar masses in kilograms?

    And WTF is "kilo" doing in a base unit anyway?
    Sorry, but astronomers are metric. They use megaparsecs, kiloparsecs, millarcseconds, etc.

    200 solar masses = 3.978 x10^32 kg
    But parsecs are parallax seconds of arc, 60 of them to a minute of arc, and the distance underlying the parallax is the A.U., which is a feature of the real world and it's irrelevant how you measure it. so mega- and kiloparsecs are hideous hybrids.
    The AU is understandable to most who are interested in such things unless we are talking about a near object like our moon which is usually referred to as 250k miles or 400k km away.

    When New Horizons reached Pluto, I think it was 38 AU from the sun [ for those who are unaware, AU = Distance from the Sun to Earth ]. It is something one can relate to.

    I would have thought parsecs refer to how much "angle" the object covers.
    No, it is the distance the position of the object apparently "jumps" when viewed at opposite ends of the year. It could in principle do what you want it to do, but no objects that far away are big enough to cover a measurable bit of arc.

    Nice explanatory drawing on top right of page here: https://en.wikipedia.org/wiki/Parsec
  • Options
    Beverley_CBeverley_C Posts: 6,256
    Ishmael_Z said:

    You what? The AU is baked in to the definition of a parsec. That's like saying it doesn't much matter how well we understand how atoms work given how small they are.

    The metre was at one point defined as (approx) 1,600,000 wavelengths of Krypton 86. If I want carpet I am not going to ask them for 6,400,000 kyrpton 86 wavelets of carpet please.


  • Options
    Ishmael_ZIshmael_Z Posts: 8,981

    RobD said:

    RobD said:


    A parsec is the distance at which 1 au subtends 1 arcsecond on the sky. They are intimately linked.

    I am not denying that. What I am saying is that if I need to use parsecs then there is virtually point to using AUs for that measurement. If something is 2.2 M parsecs away then I will say that rather than 453,783,000,000 AUs

    But that doesn't change the fact it is the basis of the parsec ;)
    *sigh*

    Yes... you correct. It is the basis of the parsec

    But nobody measures stellar distance in AUs
    That is unnecessarily rude; you are the one missing the point, and making the erroneous statement in the first place that parsecs are metric.
  • Options
    Beverley_CBeverley_C Posts: 6,256
    surbiton said:

    surbiton said:

    I would have thought parsecs refer to how much "angle" the object covers.

    The parsec is useful because it can be used in direct measurement. If star shows an annual parallax of 0.2 arcsecs then it is 1 / 0.2 = 5 parsecs away

    I see. Trigonometry. But surely a star very, very far away even after 6 months will not reveal much movement, or am I wrong ?
    The amount of movement is indeed very small, but is measurable. The Kepler satellite was able to make these measurements to discover planets of nearby stars.

    Also, see the Hipparcos satellite which determined the distances of the nearest 100,000 stars using this method

    https://en.wikipedia.org/wiki/Hipparcos
  • Options
    MortimerMortimer Posts: 13,951
    Just a reminder that in two days time, Weds 29th March, PBers can congregate and celebrate/commiserate the Article 50 triggering with like minds at Truckles of Pied Bull Yard, Bloomsbury. Area booked for 6pm in the name of 'Mr Mortimer of PB' (if they follow instructions, that is!).
  • Options
    OmniumOmnium Posts: 9,796
    surbiton said:

    surbiton said:

    I would have thought parsecs refer to how much "angle" the object covers.

    The parsec is useful because it can be used in direct measurement. If star shows an annual parallax of 0.2 arcsecs then it is 1 / 0.2 = 5 parsecs away

    I see. Trigonometry. But surely a star very, very far away even after 6 months will not reveal much movement, or am I wrong ?
    Trigonometry is used to establish the distance of close stars. That defines the units, and then other measures are used to establish the distances of objects further away, and those distances are expressed in parsecs, or light-years, or whatever.

    I believe that the most common measurement of how far away a star is is the degree of red shift in its emission spectrum, and that then translates to how quickly it's moving away from us, and then if you assume that there was a big bang you can derive a distance. That worked nicely when everyone believed in a big bang, and a simple expansion thereafter, but I'm not sure how well it works now.
  • Options
    Morris_DancerMorris_Dancer Posts: 60,994
    In good news, hoping to have the first part of a serial released in the next month or two:
    http://thaddeuswhite.weebly.com/writing-blog/a-delicious-chinese-serial-out-soon

    Heavily influenced by Chinese classics* and Robin Hood. The relationships have also been influenced by The Last of Us and The Witcher 3.

    *If you've read Outlaws of the Marsh, you'll be most of the way there. I have reduced the sexism and casual murdering, however.
  • Options
    AlistairAlistair Posts: 23,670

    Alistair said:

    I have worked in I.T. for decades. I think it is crazy too. I see adverts on the telly for central heating that you can control from your phone. Why? I set mine and leave it alone forever. If the house gets cold the sensors pick it up and turn the heating on. Why would I want to fiddle with it? Do I really want to reboot my toaster after the nightly security update?

    Fridges, toasters, kettles: certainly not. Utter nonsense (like Victorian steam-driven gadgets, just because they could do it, doesn't mean it's sensible to do it).

    However, internet control of central heating is extremely useful if you travel a lot or have a second home. Ditto security alarms.
    No, the steam gadgets were awesome. More steam driven gadgets please.
    Read William Gibson and Bruce Sterling's "The Difference Engine" for a vision of Victorian England with steam-powered computers. Now that would have been awesome.
    As a roleplayer I have GM'd Steampunk games (as in Difference Engine style grim Steampunk rather than the big cog and shiny goggles Utopian Steampunk of more modern times). Grim class-bound, oppressive society with dirty technology as the tool of oppression. So many possibilities.
  • Options
    Morris_DancerMorris_Dancer Posts: 60,994
    Mr. Alistair, did you see this video? I did post it in the past, and it's quite interesting:
    https://www.youtube.com/watch?v=vGlDsFAOWXc

    Mr. Mortimer, hope you and other PBers have a splendid time.
  • Options
    Beverley_CBeverley_C Posts: 6,256
    Ishmael_Z said:

    RobD said:

    RobD said:


    A parsec is the distance at which 1 au subtends 1 arcsecond on the sky. They are intimately linked.

    I am not denying that. What I am saying is that if I need to use parsecs then there is virtually point to using AUs for that measurement. If something is 2.2 M parsecs away then I will say that rather than 453,783,000,000 AUs

    But that doesn't change the fact it is the basis of the parsec ;)
    *sigh*

    Yes... you correct. It is the basis of the parsec

    But nobody measures stellar distance in AUs
    That is unnecessarily rude; you are the one missing the point, and making the erroneous statement in the first place that parsecs are metric.
    The parsec is no more metric than the metre. The metre is 1.6(ish) million wavelengths of light or the distance travelled by light in 1/299,000(ish) of a second. But it is divided up in a regular way just like the metre, milliparsecs, parsecs, kiloparsecs, megaparsecs gigaparsecs. We do not have an "oddball" conversion factor like 1 parfoot = 12 parsecs or 1 parinch = 1/36 of a parsec

  • Options
    surbitonsurbiton Posts: 13,549

    surbiton said:

    surbiton said:

    I would have thought parsecs refer to how much "angle" the object covers.

    The parsec is useful because it can be used in direct measurement. If star shows an annual parallax of 0.2 arcsecs then it is 1 / 0.2 = 5 parsecs away

    I see. Trigonometry. But surely a star very, very far away even after 6 months will not reveal much movement, or am I wrong ?
    The amount of movement is indeed very small, but is measurable. The Kepler satellite was able to make these measurements to discover planets of nearby stars.

    Also, see the Hipparcos satellite which determined the distances of the nearest 100,000 stars using this method

    https://en.wikipedia.org/wiki/Hipparcos
    Thanks to both of you. I wasn't aware that is how we knew of planets orbiting other stars. I thought it was the diminution of light when these planets passed in front of their star which revealed their existence.

    That is why we can measure the distance of solar system planets so accurately. Presumably, now-a-days that is done with lasers or radar. The moon has reflectors on it. That's why we sent astronauts there and to jump about.
  • Options
    Ishmael_ZIshmael_Z Posts: 8,981

    Mr. Rex, must admit I only have the single volume history by Kagan (still very good, mind).

    Mr. Z, utter guess but I'd say Wales, Peloponnese, Sicily.

    This sort of thing is not my strong point.

    Mr. D, sometimes call the hound, Meg-a-dog.

    Correct!

    Wales 20,641 square kilometres
    Peloponnese 21,549 square kilometres
    Sicily 25,711 square kilometres

    Close enough that you can substitute either of the other 2 for the traditional "about the size of Wales"
  • Options
    surbitonsurbiton Posts: 13,549

    Ishmael_Z said:

    RobD said:

    RobD said:


    A parsec is the distance at which 1 au subtends 1 arcsecond on the sky. They are intimately linked.

    I am not denying that. What I am saying is that if I need to use parsecs then there is virtually point to using AUs for that measurement. If something is 2.2 M parsecs away then I will say that rather than 453,783,000,000 AUs

    But that doesn't change the fact it is the basis of the parsec ;)
    *sigh*

    Yes... you correct. It is the basis of the parsec

    But nobody measures stellar distance in AUs
    That is unnecessarily rude; you are the one missing the point, and making the erroneous statement in the first place that parsecs are metric.
    The parsec is no more metric than the metre. The metre is 1.6(ish) million wavelengths of light or the distance travelled by light in 1/299,000(ish) of a second. But it is divided up in a regular way just like the metre, milliparsecs, parsecs, kiloparsecs, megaparsecs gigaparsecs. We do not have an "oddball" conversion factor like 1 parfoot = 12 parsecs or 1 parinch = 1/36 of a parsec

    But surely the original "metre" was the distance from the North pole to the equator divided by 10000. Obviously, only the French could think like that.
  • Options
    Morris_DancerMorris_Dancer Posts: 60,994
    Mr. Z, huzzah!

    I must admit, I thought it was the opposite order. Ahem. Mind you, I once backed Perez at surprisingly generous odds to be top 6, and then discovered the odds reflected he had a grid penalty. But he finished top 6 anyway.

    Sicily's had a very interesting history. Plenty of cities dotted about, so I knew it was a fair old size.
  • Options
    surbitonsurbiton Posts: 13,549
    Ishmael_Z said:

    Mr. Rex, must admit I only have the single volume history by Kagan (still very good, mind).

    Mr. Z, utter guess but I'd say Wales, Peloponnese, Sicily.

    This sort of thing is not my strong point.

    Mr. D, sometimes call the hound, Meg-a-dog.

    Correct!

    Wales 20,641 square kilometres
    Peloponnese 21,549 square kilometres
    Sicily 25,711 square kilometres

    Close enough that you can substitute either of the other 2 for the traditional "about the size of Wales"
    I read yesterday that Saarland is used precisely like that. As a measure. If a country or region is smaller than Saarland then it is very small !
  • Options
    RobDRobD Posts: 58,985

    surbiton said:

    surbiton said:

    I would have thought parsecs refer to how much "angle" the object covers.

    The parsec is useful because it can be used in direct measurement. If star shows an annual parallax of 0.2 arcsecs then it is 1 / 0.2 = 5 parsecs away

    I see. Trigonometry. But surely a star very, very far away even after 6 months will not reveal much movement, or am I wrong ?
    The amount of movement is indeed very small, but is measurable. The Kepler satellite was able to make these measurements to discover planets of nearby stars.

    Also, see the Hipparcos satellite which determined the distances of the nearest 100,000 stars using this method

    https://en.wikipedia.org/wiki/Hipparcos
    The Kepler satellite measured star brightnesses, not positions, but you are correct for Hipparcos. The succesor satellite GAIA has a precision of 1 microarcsecond, which is equivalent to the width of a 5p coin at 100,000 miles. :o
  • Options
    Beverley_CBeverley_C Posts: 6,256
    edited March 2017
    Omnium said:

    I believe that the most common measurement of how far away a star is is the degree of red shift in its emission spectrum, and that then translates to how quickly it's moving away from us, and then if you assume that there was a big bang you can derive a distance. That worked nicely when everyone believed in a big bang, and a simple expansion thereafter, but I'm not sure how well it works now.

    What you are describing Mr Omnium is cosmological redshift caused by the stretching of spacetime, There is also gravitational redshift and a spectral redshift caused by motion.

    Cosmological redshift is tiny and so it only is noticeable over truly vast differences. To measure the speed of a nearby star we need to use spectral redshift. This gives the speed directly towards or away from the observer, it is purely a line-of-sight velocity.

    Parallax lets us measure the distance of the star if it is close enough and we can determine two of the orthogonal velocity vectors on the celestial sphere. One we know the radical motion from the spectrum then we have all three vectors and the distance and we know the distance and true motion of the star. In parsecs!

  • Options
    RobDRobD Posts: 58,985

    Ishmael_Z said:

    RobD said:

    RobD said:


    A parsec is the distance at which 1 au subtends 1 arcsecond on the sky. They are intimately linked.

    I am not denying that. What I am saying is that if I need to use parsecs then there is virtually point to using AUs for that measurement. If something is 2.2 M parsecs away then I will say that rather than 453,783,000,000 AUs

    But that doesn't change the fact it is the basis of the parsec ;)
    *sigh*

    Yes... you correct. It is the basis of the parsec

    But nobody measures stellar distance in AUs
    That is unnecessarily rude; you are the one missing the point, and making the erroneous statement in the first place that parsecs are metric.
    The parsec is no more metric than the metre. The metre is 1.6(ish) million wavelengths of light or the distance travelled by light in 1/299,000(ish) of a second. But it is divided up in a regular way just like the metre, milliparsecs, parsecs, kiloparsecs, megaparsecs gigaparsecs. We do not have an "oddball" conversion factor like 1 parfoot = 12 parsecs or 1 parinch = 1/36 of a parsec

    We do have the odd-ball conversion 1 pc = 3.26 light years :p
  • Options
    Beverley_CBeverley_C Posts: 6,256
    RobD said:

    surbiton said:

    surbiton said:

    I would have thought parsecs refer to how much "angle" the object covers.

    The parsec is useful because it can be used in direct measurement. If star shows an annual parallax of 0.2 arcsecs then it is 1 / 0.2 = 5 parsecs away

    I see. Trigonometry. But surely a star very, very far away even after 6 months will not reveal much movement, or am I wrong ?
    The amount of movement is indeed very small, but is measurable. The Kepler satellite was able to make these measurements to discover planets of nearby stars.

    Also, see the Hipparcos satellite which determined the distances of the nearest 100,000 stars using this method

    https://en.wikipedia.org/wiki/Hipparcos
    The Kepler satellite measured star brightnesses, not positions, but you are correct for Hipparcos. The succesor satellite GAIA has a precision of 1 microarcsecond, which is equivalent to the width of a 5p coin at 100,000 miles. :o
    :+1:
  • Options
    rcs1000rcs1000 Posts: 54,031
    Mortimer said:

    Just a reminder that in two days time, Weds 29th March, PBers can congregate and celebrate/commiserate the Article 50 triggering with like minds at Truckles of Pied Bull Yard, Bloomsbury. Area booked for 6pm in the name of 'Mr Mortimer of PB' (if they follow instructions, that is!).

    I shall be in the City of Angels, but will be thinking about you all.
  • Options
    JosiasJessopJosiasJessop Posts: 39,054
    surbiton said:

    surbiton said:

    surbiton said:

    I would have thought parsecs refer to how much "angle" the object covers.

    The parsec is useful because it can be used in direct measurement. If star shows an annual parallax of 0.2 arcsecs then it is 1 / 0.2 = 5 parsecs away

    I see. Trigonometry. But surely a star very, very far away even after 6 months will not reveal much movement, or am I wrong ?
    The amount of movement is indeed very small, but is measurable. The Kepler satellite was able to make these measurements to discover planets of nearby stars.

    Also, see the Hipparcos satellite which determined the distances of the nearest 100,000 stars using this method

    https://en.wikipedia.org/wiki/Hipparcos
    Thanks to both of you. I wasn't aware that is how we knew of planets orbiting other stars. I thought it was the diminution of light when these planets passed in front of their star which revealed their existence.

    That is why we can measure the distance of solar system planets so accurately. Presumably, now-a-days that is done with lasers or radar. The moon has reflectors on it. That's why we sent astronauts there and to jump about.
    I think only the Moon is done with lases; the signal is so weak by the time it is received back that it is just a few photons.

    I think (*) that they can also tell via radar, and have inf act images Venus's surface from Earth by this mechanism. I think!

    (*) You'll be reading that word alot! :)
  • Options
    Morris_DancerMorris_Dancer Posts: 60,994
    F1: minor story, but Hamilton's ditched his personal trainer:
    http://www.bbc.co.uk/sport/formula1/39410617

    I suspect he''ll be fine (not his first year), but there's an off-chance he'll either overdo it or (less likely) not prepare sufficiently. Seems a slightly odd decision, but he first raced in F1 in 2007, so he'll probably be alright.
  • Options
    malcolmgmalcolmg Posts: 42,062

    A log burner in a fire place is good, but a lot of the heat goes up the chimney and into the bricks. We've got ours in the lounge, but against a wall, with the maximum allowed exposed flue plugged into the side of the chimney breast. It's only small, but can be unbearable. A few weeks ago when we had a mini cold snap, I walked around with the Hive thermostat. It was 36 degrees on the sofa, 25 in the hallway, and 22 in our bedroom. Trouble is, the temperature difference is so great, it feels freezing in the bedroom! I've got a Stirling fan on the top of the stove, which does seem to push the heat around a little.

    TFS you are a wimp , when I were a lad we had no heating , coal fire in the living room was it, we had ice on the inside of the bedroom windows.
  • Options
    malcolmgmalcolmg Posts: 42,062
    TGOHF said:

    Thats the end of the road then - it will be declined and that's that.
    Ha Ha Ha
  • Options
    sladeslade Posts: 1,932
    By-election news: Lord Colgrain has won the by-election for hereditory peers. He beat 26 other candidates including Earl Stockton, Earl Lloyd-George, and Lord Harlech. Can honestly say I had never heard of him.
  • Options
    rcs1000rcs1000 Posts: 54,031
    Having spent a great deal of time in the US, I have decided that I prefer metric measurements, if only because there are subtle differences between countries with some measures. So, a UK gallon is slightly different to a US one, and a ton is different in each country too. Plus some people use the very weird idea of fluid ounces, which are a measurement of volume, not weight.


  • Options
    Morris_DancerMorris_Dancer Posts: 60,994
    Mr. G, coal? Oh, we dreamed of burning coal. We had to sting ourselves with nettles to try and warm ourselves. And we had to pay landlord for privilege of picking his nettles.
  • Options
    Beverley_CBeverley_C Posts: 6,256
    Time to go....

    Thanks for the chat everyone :)
  • Options
    malcolmgmalcolmg Posts: 42,062

    I don't believe that Brexit will change the pizzeria: chippie ratio in Eire. However, the U.K. regaining its ancestral fishing waters could see a boom in well-priced fish restaurants there.

    Do not be surprised if access to our fish is part of the Brexit agreement.

    Especially the Scottish part.
  • Options
    surbitonsurbiton Posts: 13,549
    slade said:

    By-election news: Lord Colgrain has won the by-election for hereditory peers. He beat 26 other candidates including Earl Stockton, Earl Lloyd-George, and Lord Harlech. Can honestly say I had never heard of him.

    Was it by STV, AV, FPTP ? That is the only thing I am interested in.
  • Options
    Y0kelY0kel Posts: 2,307
    Various downthread re: NI Assembly

    My understanding is that about 5 different approaches have been prepared by civil service types for dealing with a non-functioning Assembly before going to election and its not that its pick one or the other either, they could use 2 or 3 at different times to put a circle around things until people want to get real again.
  • Options
    Ishmael_ZIshmael_Z Posts: 8,981
    surbiton said:

    Ishmael_Z said:

    RobD said:

    RobD said:


    A parsec is the distance at which 1 au subtends 1 arcsecond on the sky. They are intimately linked.

    I am not denying that. What I am saying is that if I need to use parsecs then there is virtually point to using AUs for that measurement. If something is 2.2 M parsecs away then I will say that rather than 453,783,000,000 AUs

    But that doesn't change the fact it is the basis of the parsec ;)
    *sigh*

    Yes... you correct. It is the basis of the parsec

    But nobody measures stellar distance in AUs
    That is unnecessarily rude; you are the one missing the point, and making the erroneous statement in the first place that parsecs are metric.
    The parsec is no more metric than the metre. The metre is 1.6(ish) million wavelengths of light or the distance travelled by light in 1/299,000(ish) of a second. But it is divided up in a regular way just like the metre, milliparsecs, parsecs, kiloparsecs, megaparsecs gigaparsecs. We do not have an "oddball" conversion factor like 1 parfoot = 12 parsecs or 1 parinch = 1/36 of a parsec

    But surely the original "metre" was the distance from the North pole to the equator divided by 10000. Obviously, only the French could think like that.
    The most annoying number in the world, after Don Bradman's batting average, is the speed of light at 299 792 458 m / s. If only, if only we could redefine the metre as 1/300000000 of the distance light travels in a vacuum in 1 second.
  • Options
    malcolmg said:

    A log burner in a fire place is good, but a lot of the heat goes up the chimney and into the bricks. We've got ours in the lounge, but against a wall, with the maximum allowed exposed flue plugged into the side of the chimney breast. It's only small, but can be unbearable. A few weeks ago when we had a mini cold snap, I walked around with the Hive thermostat. It was 36 degrees on the sofa, 25 in the hallway, and 22 in our bedroom. Trouble is, the temperature difference is so great, it feels freezing in the bedroom! I've got a Stirling fan on the top of the stove, which does seem to push the heat around a little.

    TFS you are a wimp , when I were a lad we had no heating , coal fire in the living room was it, we had ice on the inside of the bedroom windows.
    I had that as a lad in a council house in a small village outside Leicester late 60, early 70s.. I remember the worst winter, the water in the inside toilet froze! I vowed never to be cold and poor as an adult. I've not always kept the vow, unfortunately!
  • Options
    RobDRobD Posts: 58,985
    surbiton said:

    slade said:

    By-election news: Lord Colgrain has won the by-election for hereditory peers. He beat 26 other candidates including Earl Stockton, Earl Lloyd-George, and Lord Harlech. Can honestly say I had never heard of him.

    Was it by STV, AV, FPTP ? That is the only thing I am interested in.
    I think the peers vote via AV.
  • Options
    JosiasJessopJosiasJessop Posts: 39,054

    surbiton said:

    surbiton said:

    I would have thought parsecs refer to how much "angle" the object covers.

    The parsec is useful because it can be used in direct measurement. If star shows an annual parallax of 0.2 arcsecs then it is 1 / 0.2 = 5 parsecs away

    I see. Trigonometry. But surely a star very, very far away even after 6 months will not reveal much movement, or am I wrong ?
    The amount of movement is indeed very small, but is measurable. The Kepler satellite was able to make these measurements to discover planets of nearby stars.

    Also, see the Hipparcos satellite which determined the distances of the nearest 100,000 stars using this method

    https://en.wikipedia.org/wiki/Hipparcos
    From memory, there are several main mechanisms to detect an exoplanet:
    1) 'wobble' of a star's orbit (the gravitational effect of the planes)
    2) Dimunation of a star's light as a planet passes in front of it. This requires the star and planet to be on the same plane relative to us.
    3) Gravitational lensing (rare, and mostly suitable for very long distances).
    4) Direct imaging; the light reflected from the planet.

    Both 1 and 2 are best at detecting larger planets (as they dim the light more, and cause more wobbles). Planet of Earth mass are harder to detect. ISTR some planets have been detected by both 1 and 2, which is reasonable confirmation of the techniques. 3 is just weird. :)
  • Options
    Ishmael_ZIshmael_Z Posts: 8,981
    rcs1000 said:

    Having spent a great deal of time in the US, I have decided that I prefer metric measurements, if only because there are subtle differences between countries with some measures. So, a UK gallon is slightly different to a US one, and a ton is different in each country too. Plus some people use the very weird idea of fluid ounces, which are a measurement of volume, not weight.


    It gets worse: in the world of shipping a ton is in some contexts a measure of volume (100 cubic feet).
  • Options
    OmniumOmnium Posts: 9,796

    Omnium said:

    I believe that the most common measurement of how far away a star is is the degree of red shift in its emission spectrum, and that then translates to how quickly it's moving away from us, and then if you assume that there was a big bang you can derive a distance. That worked nicely when everyone believed in a big bang, and a simple expansion thereafter, but I'm not sure how well it works now.

    What you are describing Mr Omnium is cosmological redshift caused by the stretching of spacetime, There is also gravitational redshift and a spectral redshift caused by motion.

    Cosmological redshift is tiny and so it only is noticeable over truly vast differences. To measure the speed of a nearby star we need to use spectral redshift. This gives the speed directly towards or away from the observer, it is purely a line-of-sight velocity.

    Parallax lets us measure the distance of the star if it is close enough and we can determine two of the orthogonal velocity vectors on the celestial sphere. One we know the radical motion from the spectrum then we have all three vectors and the distance and we know the distance and true motion of the star. In parsecs!

    Well yes. That was what I thought I said! :). All red-shift must be spectral. Close things are measured by trig, somewhat less close things by red-shift. You can combine in between. The confidence with which one can ascribe a distance based on the receding velocity (redshift) is dependent on the confidence that we have that the object is receding at a rate proportional to its distance. Our confidence in such things isn't great with very big distances. You're quite right that anything heavy in the way totally messes up any measurement too.

    Bloke from Ulm deserves a mention.

  • Options
    rcs1000rcs1000 Posts: 54,031
    Ishmael_Z said:

    surbiton said:

    Ishmael_Z said:

    RobD said:

    RobD said:


    A parsec is the distance at which 1 au subtends 1 arcsecond on the sky. They are intimately linked.

    I am not denying that. What I am saying is that if I need to use parsecs then there is virtually point to using AUs for that measurement. If something is 2.2 M parsecs away then I will say that rather than 453,783,000,000 AUs

    But that doesn't change the fact it is the basis of the parsec ;)
    *sigh*

    Yes... you correct. It is the basis of the parsec

    But nobody measures stellar distance in AUs
    That is unnecessarily rude; you are the one missing the point, and making the erroneous statement in the first place that parsecs are metric.
    The parsec is no more metric than the metre. The metre is 1.6(ish) million wavelengths of light or the distance travelled by light in 1/299,000(ish) of a second. But it is divided up in a regular way just like the metre, milliparsecs, parsecs, kiloparsecs, megaparsecs gigaparsecs. We do not have an "oddball" conversion factor like 1 parfoot = 12 parsecs or 1 parinch = 1/36 of a parsec

    But surely the original "metre" was the distance from the North pole to the equator divided by 10000. Obviously, only the French could think like that.
    The most annoying number in the world, after Don Bradman's batting average, is the speed of light at 299 792 458 m / s. If only, if only we could redefine the metre as 1/300000000 of the distance light travels in a vacuum in 1 second.
    Surely if we simply changed the value of a second, that problem would solve itself.
  • Options
    BarnesianBarnesian Posts: 7,997

    malcolmg said:

    A log burner in a fire place is good, but a lot of the heat goes up the chimney and into the bricks. We've got ours in the lounge, but against a wall, with the maximum allowed exposed flue plugged into the side of the chimney breast. It's only small, but can be unbearable. A few weeks ago when we had a mini cold snap, I walked around with the Hive thermostat. It was 36 degrees on the sofa, 25 in the hallway, and 22 in our bedroom. Trouble is, the temperature difference is so great, it feels freezing in the bedroom! I've got a Stirling fan on the top of the stove, which does seem to push the heat around a little.

    TFS you are a wimp , when I were a lad we had no heating , coal fire in the living room was it, we had ice on the inside of the bedroom windows.
    I had that as a lad in a council house in a small village outside Leicester late 60, early 70s.. I remember the worst winter, the water in the inside toilet froze! I vowed never to be cold and poor as an adult. I've not always kept the vow, unfortunately!
    You had an inside toilet!
  • Options
    RobDRobD Posts: 58,985
    edited March 2017

    surbiton said:

    surbiton said:

    I would have thought parsecs refer to how much "angle" the object covers.

    The parsec is useful because it can be used in direct measurement. If star shows an annual parallax of 0.2 arcsecs then it is 1 / 0.2 = 5 parsecs away

    I see. Trigonometry. But surely a star very, very far away even after 6 months will not reveal much movement, or am I wrong ?
    The amount of movement is indeed very small, but is measurable. The Kepler satellite was able to make these measurements to discover planets of nearby stars.

    Also, see the Hipparcos satellite which determined the distances of the nearest 100,000 stars using this method

    https://en.wikipedia.org/wiki/Hipparcos
    From memory, there are several main mechanisms to detect an exoplanet:
    1) 'wobble' of a star's orbit (the gravitational effect of the planes)
    2) Dimunation of a star's light as a planet passes in front of it. This requires the star and planet to be on the same plane relative to us.
    3) Gravitational lensing (rare, and mostly suitable for very long distances).
    4) Direct imaging; the light reflected from the planet.

    Both 1 and 2 are best at detecting larger planets (as they dim the light more, and cause more wobbles). Planet of Earth mass are harder to detect. ISTR some planets have been detected by both 1 and 2, which is reasonable confirmation of the techniques. 3 is just weird. :)
    For 4, it has primarily been measuring the flux emitted by the planets themselves, they are too far away from their host star for reflected light.
  • Options
    malcolmgmalcolmg Posts: 42,062

    Mr. G, coal? Oh, we dreamed of burning coal. We had to sting ourselves with nettles to try and warm ourselves. And we had to pay landlord for privilege of picking his nettles.

    LOL, certainly made you tough if it did not kill you MD.
  • Options
    JosiasJessopJosiasJessop Posts: 39,054
    RobD said:

    surbiton said:

    surbiton said:

    I would have thought parsecs refer to how much "angle" the object covers.

    The parsec is useful because it can be used in direct measurement. If star shows an annual parallax of 0.2 arcsecs then it is 1 / 0.2 = 5 parsecs away

    I see. Trigonometry. But surely a star very, very far away even after 6 months will not reveal much movement, or am I wrong ?
    The amount of movement is indeed very small, but is measurable. The Kepler satellite was able to make these measurements to discover planets of nearby stars.

    Also, see the Hipparcos satellite which determined the distances of the nearest 100,000 stars using this method

    https://en.wikipedia.org/wiki/Hipparcos
    From memory, there are several main mechanisms to detect an exoplanet:
    1) 'wobble' of a star's orbit (the gravitational effect of the planes)
    2) Dimunation of a star's light as a planet passes in front of it. This requires the star and planet to be on the same plane relative to us.
    3) Gravitational lensing (rare, and mostly suitable for very long distances).
    4) Direct imaging; the light reflected from the planet.

    Both 1 and 2 are best at detecting larger planets (as they dim the light more, and cause more wobbles). Planet of Earth mass are harder to detect. ISTR some planets have been detected by both 1 and 2, which is reasonable confirmation of the techniques. 3 is just weird. :)
    For 4, it has primarily been measuring the flux emitted by the planets themselves, they are too far away from their host star for reflected light.
    Thanks. IANAE. Just an interested observer. :)
  • Options
    Morris_DancerMorris_Dancer Posts: 60,994
    Mr. G, the nettle example was actually used by Spartan children. They were taken from their parents and 'educated' at an institution. I believe it was around 12 when they were given their first garment (one cloak). They were also given insufficient food to survive, and punished for stealing more (not for stealing, but for getting caught).

    My mother occasionally spoke of getting frost on the inside of the windows.

    Does put into perspective the nonsense of relative poverty.
  • Options
    Ishmael_ZIshmael_Z Posts: 8,981
    rcs1000 said:

    Ishmael_Z said:

    surbiton said:

    Ishmael_Z said:

    RobD said:

    RobD said:


    A parsec is the distance at which 1 au subtends 1 arcsecond on the sky. They are intimately linked.

    I am not denying that. What I am saying is that if I need to use parsecs then there is virtually point to using AUs for that measurement. If something is 2.2 M parsecs away then I will say that rather than 453,783,000,000 AUs

    But that doesn't change the fact it is the basis of the parsec ;)
    *sigh*

    Yes... you correct. It is the basis of the parsec

    But nobody measures stellar distance in AUs
    That is unnecessarily rude; you are the one missing the point, and making the erroneous statement in the first place that parsecs are metric.
    The parsec is no more metric than the metre. The metre is 1.6(ish) million wavelengths of light or the distance travelled by light in 1/299,000(ish) of a second. But it is divided up in a regular way just like the metre, milliparsecs, parsecs, kiloparsecs, megaparsecs gigaparsecs. We do not have an "oddball" conversion factor like 1 parfoot = 12 parsecs or 1 parinch = 1/36 of a parsec

    But surely the original "metre" was the distance from the North pole to the equator divided by 10000. Obviously, only the French could think like that.
    The most annoying number in the world, after Don Bradman's batting average, is the speed of light at 299 792 458 m / s. If only, if only we could redefine the metre as 1/300000000 of the distance light travels in a vacuum in 1 second.
    Surely if we simply changed the value of a second, that problem would solve itself.
    I believe there are nutters about who contend that the speed of light is not constant but changes over time. Either your change, or mine, would make it very difficult for them to formulate their claim..
  • Options
    BarnesianBarnesian Posts: 7,997

    Ishmael_Z said:

    RobD said:

    RobD said:


    A parsec is the distance at which 1 au subtends 1 arcsecond on the sky. They are intimately linked.

    I am not denying that. What I am saying is that if I need to use parsecs then there is virtually point to using AUs for that measurement. If something is 2.2 M parsecs away then I will say that rather than 453,783,000,000 AUs

    But that doesn't change the fact it is the basis of the parsec ;)
    *sigh*

    Yes... you correct. It is the basis of the parsec

    But nobody measures stellar distance in AUs
    That is unnecessarily rude; you are the one missing the point, and making the erroneous statement in the first place that parsecs are metric.
    The parsec is no more metric than the metre. The metre is 1.6(ish) million wavelengths of light or the distance travelled by light in 1/299,000(ish) of a second. But it is divided up in a regular way just like the metre, milliparsecs, parsecs, kiloparsecs, megaparsecs gigaparsecs. We do not have an "oddball" conversion factor like 1 parfoot = 12 parsecs or 1 parinch = 1/36 of a parsec

    When I was the marketing manager of a major wallpaper brand, a roll of wallpaper measured half a long elephant. This was roughly 21" by 16' 6".

    On metrication I met with sales, production and distribution to agree the simplest metric units. After a long discussion, we agreed on 529mm by 4990mm.
  • Options
    jayfdeejayfdee Posts: 618
    Ishmael_Z said:

    rcs1000 said:

    Having spent a great deal of time in the US, I have decided that I prefer metric measurements, if only because there are subtle differences between countries with some measures. So, a UK gallon is slightly different to a US one, and a ton is different in each country too. Plus some people use the very weird idea of fluid ounces, which are a measurement of volume, not weight.


    It gets worse: in the world of shipping a ton is in some contexts a measure of volume (100 cubic feet).
    I spent my life in the chemical industry, trained in SI units but had to live in an old fashioned world. I remember using degrees Twaddle for SG. Anyway I agree ,I prefer metric. I communicate with many in the US and find it increasingly difficult as time goes by and I cannot remember a gallon of water weighs 10 lbs, unless it is an US gallon.
  • Options
    malcolmgmalcolmg Posts: 42,062

    malcolmg said:

    A log burner in a fire place is good, but a lot of the heat goes up the chimney and into the bricks. We've got ours in the lounge, but against a wall, with the maximum allowed exposed flue plugged into the side of the chimney breast. It's only small, but can be unbearable. A few weeks ago when we had a mini cold snap, I walked around with the Hive thermostat. It was 36 degrees on the sofa, 25 in the hallway, and 22 in our bedroom. Trouble is, the temperature difference is so great, it feels freezing in the bedroom! I've got a Stirling fan on the top of the stove, which does seem to push the heat around a little.

    TFS you are a wimp , when I were a lad we had no heating , coal fire in the living room was it, we had ice on the inside of the bedroom windows.
    I had that as a lad in a council house in a small village outside Leicester late 60, early 70s.. I remember the worst winter, the water in the inside toilet froze! I vowed never to be cold and poor as an adult. I've not always kept the vow, unfortunately!
    Certainly a bit easier switching on the CH but nothing to beat an open fire. I miss having one, have a
    glass log fir ebut not quite the same. I do have a working fireplace in my other place I rent.
    I would get a woodburner if I stay long term , but as modern house with the big gas log fire I have at present you can only have it on a short while and you are melted, should have put in a smaller one methinks.
  • Options
    BarnesianBarnesian Posts: 7,997

    Mr. G, the nettle example was actually used by Spartan children. They were taken from their parents and 'educated' at an institution. I believe it was around 12 when they were given their first garment (one cloak). They were also given insufficient food to survive, and punished for stealing more (not for stealing, but for getting caught).

    My mother occasionally spoke of getting frost on the inside of the windows.

    Does put into perspective the nonsense of relative poverty.

    My sister and I used to amuse ourselves by breathing on frost covered windows in our bedroom and watching the frost reform in intricate fern shaped patterns.
  • Options
    JosiasJessopJosiasJessop Posts: 39,054
    Ishmael_Z said:

    rcs1000 said:

    Ishmael_Z said:

    surbiton said:

    Ishmael_Z said:

    RobD said:

    RobD said:


    A parsec is the distance at which 1 au subtends 1 arcsecond on the sky. They are intimately linked.

    I am not denying that. What I am saying is that if I need to use parsecs then there is virtually point to using AUs for that measurement. If something is 2.2 M parsecs away then I will say that rather than 453,783,000,000 AUs

    But that doesn't change the fact it is the basis of the parsec ;)
    *sigh*

    Yes... you correct. It is the basis of the parsec

    But nobody measures stellar distance in AUs
    That is unnecessarily rude; you are the one missing the point, and making the erroneous statement in the first place that parsecs are metric.
    The parsec is no more metric than the metre. The metre is 1.6(ish) million wavelengths of light or the distance travelled by light in 1/299,000(ish) of a second. But it is divided up in a regular way just like the metre, milliparsecs, parsecs, kiloparsecs, megaparsecs gigaparsecs. We do not have an "oddball" conversion factor like 1 parfoot = 12 parsecs or 1 parinch = 1/36 of a parsec

    But surely the original "metre" was the distance from the North pole to the equator divided by 10000. Obviously, only the French could think like that.
    The most annoying number in the world, after Don Bradman's batting average, is the speed of light at 299 792 458 m / s. If only, if only we could redefine the metre as 1/300000000 of the distance light travels in a vacuum in 1 second.
    Surely if we simply changed the value of a second, that problem would solve itself.
    I believe there are nutters about who contend that the speed of light is not constant but changes over time. Either your change, or mine, would make it very difficult for them to formulate their claim..
    There's also someone who says that gravity isn't a fundamental force:
    https://phys.org/news/2016-11-theory-gravity-dark.html
  • Options
    malcolmgmalcolmg Posts: 42,062

    Mr. G, the nettle example was actually used by Spartan children. They were taken from their parents and 'educated' at an institution. I believe it was around 12 when they were given their first garment (one cloak). They were also given insufficient food to survive, and punished for stealing more (not for stealing, but for getting caught).

    My mother occasionally spoke of getting frost on the inside of the windows.

    Does put into perspective the nonsense of relative poverty.

    For sure and we were happy as could be , always had plenty food and was great to run down in morning and get dressed in front of a roaring fire.
  • Options
    Morris_DancerMorris_Dancer Posts: 60,994
    Mr. Jessop, is he joking? Sounds like a theory of levity.

    /fetchescoat
  • Options
    GeoffMGeoffM Posts: 6,071
    slade said:

    By-election news: Lord Colgrain has won the by-election for hereditory peers. He beat 26 other candidates including Earl Stockton, Earl Lloyd-George, and Lord Harlech. Can honestly say I had never heard of him.

    Who, indeed, would be expected to have heard of a hereditary peerage created after WW2?
  • Options
    GeoffM said:

    slade said:

    By-election news: Lord Colgrain has won the by-election for hereditory peers. He beat 26 other candidates including Earl Stockton, Earl Lloyd-George, and Lord Harlech. Can honestly say I had never heard of him.

    Who, indeed, would be expected to have heard of a hereditary peerage created after WW2?
    Jobs for the boys.....
  • Options
    RobDRobD Posts: 58,985

    RobD said:

    surbiton said:

    surbiton said:

    I would have thought parsecs refer to how much "angle" the object covers.

    The parsec is useful because it can be used in direct measurement. If star shows an annual parallax of 0.2 arcsecs then it is 1 / 0.2 = 5 parsecs away

    I see. Trigonometry. But surely a star very, very far away even after 6 months will not reveal much movement, or am I wrong ?
    The amount of movement is indeed very small, but is measurable. The Kepler satellite was able to make these measurements to discover planets of nearby stars.

    Also, see the Hipparcos satellite which determined the distances of the nearest 100,000 stars using this method

    https://en.wikipedia.org/wiki/Hipparcos
    From memory, there are several main mechanisms to detect an exoplanet:
    1) 'wobble' of a star's orbit (the gravitational effect of the planes)
    2) Dimunation of a star's light as a planet passes in front of it. This requires the star and planet to be on the same plane relative to us.
    3) Gravitational lensing (rare, and mostly suitable for very long distances).
    4) Direct imaging; the light reflected from the planet.

    Both 1 and 2 are best at detecting larger planets (as they dim the light more, and cause more wobbles). Planet of Earth mass are harder to detect. ISTR some planets have been detected by both 1 and 2, which is reasonable confirmation of the techniques. 3 is just weird. :)
    For 4, it has primarily been measuring the flux emitted by the planets themselves, they are too far away from their host star for reflected light.
    Thanks. IANAE. Just an interested observer. :)
    New space telescopes such as WFIRST will be looking for reflected light planets - the goal for those is to search for earth like planets. Currently direct imaging is focussed on looking for Jupiter-like planets which are still warm from their formation (~1000K compared to Jupiter's ~100K).
  • Options
    Morris_DancerMorris_Dancer Posts: 60,994
    Anyway, now we've settled that imperial measures are super and metric measures are Frenchist failure, I'm off.
  • Options
    OmniumOmnium Posts: 9,796
    Ishmael_Z said:

    rcs1000 said:

    Ishmael_Z said:

    surbiton said:

    Ishmael_Z said:

    RobD said:

    RobD said:


    A parsec is the distance at which 1 au subtends 1 arcsecond on the sky. They are intimately linked.

    I am not denying that. What I am saying is that if I need to use parsecs then there is virtually point to using AUs for that measurement. If something is 2.2 M parsecs away then I will say that rather than 453,783,000,000 AUs

    But that doesn't change the fact it is the basis of the parsec ;)
    *sigh*

    Yes... you correct. It is the basis of the parsec

    But nobody measures stellar distance in AUs
    That is unnecessarily rude; you are the one missing the point, and making the erroneous statement in the first place that parsecs are metric.
    The parsec is no more metric than the metre. The metre is 1.6(ish) million wavelengths of light or the distance travelled by light in 1/299,000(ish) of a second. But it is divided up in a regular way just like the metre, milliparsecs, parsecs, kiloparsecs, megaparsecs gigaparsecs. We do not have an "oddball" conversion factor like 1 parfoot = 12 parsecs or 1 parinch = 1/36 of a parsec

    But surely the original "metre" was the distance from the North pole to the equator divided by 10000. Obviously, only the French could think like that.
    The most annoying number in the world, after Don Bradman's batting average, is the speed of light at 299 792 458 m / s. If only, if only we could redefine the metre as 1/300000000 of the distance light travels in a vacuum in 1 second.
    Surely if we simply changed the value of a second, that problem would solve itself.
    I believe there are nutters about who contend that the speed of light is not constant but changes over time. Either your change, or mine, would make it very difficult for them to formulate their claim..
    I'm in the nutters camp then! I think it's more likely that it does change than that it doesn't. I can't see why it might be constant. Even such obviously constant things like the number of dimensions in the universe might not actually be so. I guess I draw my personal line with things like prime numbers - I do believe that a number that is prime now will be prime forever. Tory government is looking like a candidate for another good example!

  • Options
    SandyRentoolSandyRentool Posts: 20,655
    Y0kel said:

    Various downthread re: NI Assembly

    My understanding is that about 5 different approaches have been prepared by civil service types for dealing with a non-functioning Assembly before going to election and its not that its pick one or the other either, they could use 2 or 3 at different times to put a circle around things until people want to get real again.

    Do any of them involve baseball bats?
  • Options
    SimonStClareSimonStClare Posts: 7,976
    Barnesian said:

    Mr. G, the nettle example was actually used by Spartan children. They were taken from their parents and 'educated' at an institution. I believe it was around 12 when they were given their first garment (one cloak). They were also given insufficient food to survive, and punished for stealing more (not for stealing, but for getting caught).

    My mother occasionally spoke of getting frost on the inside of the windows.

    Does put into perspective the nonsense of relative poverty.

    My sister and I used to amuse ourselves by breathing on frost covered windows in our bedroom and watching the frost reform in intricate fern shaped patterns.
    You had windows!, you lucky bar steward...
  • Options
    RobDRobD Posts: 58,985

    Anyway, now we've settled that imperial measures are super and metric measures are Frenchist failure, I'm off.

    I'm glad we got that sorted :D
  • Options
    rcs1000rcs1000 Posts: 54,031
    Ishmael_Z said:

    rcs1000 said:

    Ishmael_Z said:

    surbiton said:

    Ishmael_Z said:

    RobD said:

    RobD said:


    A parsec is the distance at which 1 au subtends 1 arcsecond on the sky. They are intimately linked.

    I am not denying that. What I am saying is that if I need to use parsecs then there is virtually point to using AUs for that measurement. If something is 2.2 M parsecs away then I will say that rather than 453,783,000,000 AUs

    But that doesn't change the fact it is the basis of the parsec ;)
    *sigh*

    Yes... you correct. It is the basis of the parsec

    But nobody measures stellar distance in AUs
    That is unnecessarily rude; you are the one missing the point, and making the erroneous statement in the first place that parsecs are metric.
    The parsec is no more metric than the metre. The metre is 1.6(ish) million wavelengths of light or the distance travelled by light in 1/299,000(ish) of a second. But it is divided up in a regular way just like the metre, milliparsecs, parsecs, kiloparsecs, megaparsecs gigaparsecs. We do not have an "oddball" conversion factor like 1 parfoot = 12 parsecs or 1 parinch = 1/36 of a parsec

    But surely the original "metre" was the distance from the North pole to the equator divided by 10000. Obviously, only the French could think like that.
    The most annoying number in the world, after Don Bradman's batting average, is the speed of light at 299 792 458 m / s. If only, if only we could redefine the metre as 1/300000000 of the distance light travels in a vacuum in 1 second.
    Surely if we simply changed the value of a second, that problem would solve itself.
    I believe there are nutters about who contend that the speed of light is not constant but changes over time. Either your change, or mine, would make it very difficult for them to formulate their claim..
    As an aside, I have also solved the problem of Bradman's average. If we simply change the number of runs gotten with a "4" to 4.062, then his average gets to 100.

    Of course, we'll need to go back an rescore all historic cricket matches, but I think you'll agree that is a small price to pay.
  • Options
    sladeslade Posts: 1,932
    GeoffM said:

    slade said:

    By-election news: Lord Colgrain has won the by-election for hereditory peers. He beat 26 other candidates including Earl Stockton, Earl Lloyd-George, and Lord Harlech. Can honestly say I had never heard of him.

    Who, indeed, would be expected to have heard of a hereditary peerage created after WW2?
    On investigation he is just what the Lords needs - a banker and a scion of clan Campbell.
  • Options
    surbitonsurbiton Posts: 13,549
    rcs1000 said:

    Ishmael_Z said:

    rcs1000 said:

    Ishmael_Z said:

    surbiton said:

    Ishmael_Z said:

    RobD said:

    RobD said:


    A parsec is the distance at which 1 au subtends 1 arcsecond on the sky. They are intimately linked.

    I am not denying that. What I am saying is that if I need to use parsecs then there is virtually point to using AUs for that measurement. If something is 2.2 M parsecs away then I will say that rather than 453,783,000,000 AUs

    But that doesn't change the fact it is the basis of the parsec ;)
    *sigh*

    Yes... you correct. It is the basis of the parsec

    But nobody measures stellar distance in AUs
    That is unnecessarily rude; you are the one missing the point, and making the erroneous statement in the first place that parsecs are metric.
    The parsec is no more metric than the metre. The metre is 1.6(ish) million wavelengths of light or the distance travelled by light in 1/299,000(ish) of a second. But it is divided up in a regular way just like the metre, milliparsecs, parsecs, kiloparsecs, megaparsecs gigaparsecs. We do not have an "oddball" conversion factor like 1 parfoot = 12 parsecs or 1 parinch = 1/36 of a parsec

    But surely the original "metre" was the distance from the North pole to the equator divided by 10000. Obviously, only the French could think like that.
    The most annoying number in the world, after Don Bradman's batting average, is the speed of light at 299 792 458 m / s. If only, if only we could redefine the metre as 1/300000000 of the distance light travels in a vacuum in 1 second.
    Surely if we simply changed the value of a second, that problem would solve itself.
    I believe there are nutters about who contend that the speed of light is not constant but changes over time. Either your change, or mine, would make it very difficult for them to formulate their claim..
    As an aside, I have also solved the problem of Bradman's average. If we simply change the number of runs gotten with a "4" to 4.062, then his average gets to 100.

    Of course, we'll need to go back an rescore all historic cricket matches, but I think you'll agree that is a small price to pay.
    I blame Hollies. He should have allowed Bradman to score a 4 and then get him out.
  • Options
    JosiasJessopJosiasJessop Posts: 39,054
    RobD said:

    RobD said:

    surbiton said:

    surbiton said:

    I would have thought parsecs refer to how much "angle" the object covers.

    The parsec is useful because it can be used in direct measurement. If star shows an annual parallax of 0.2 arcsecs then it is 1 / 0.2 = 5 parsecs away

    I see. Trigonometry. But surely a star very, very far away even after 6 months will not reveal much movement, or am I wrong ?
    The amount of movement is indeed very small, but is measurable. The Kepler satellite was able to make these measurements to discover planets of nearby stars.

    Also, see the Hipparcos satellite which determined the distances of the nearest 100,000 stars using this method

    https://en.wikipedia.org/wiki/Hipparcos
    From memory, there are several main mechanisms to detect an exoplanet:
    1) 'wobble' of a star's orbit (the gravitational effect of the planes)
    2) Dimunation of a star's light as a planet passes in front of it. This requires the star and planet to be on the same plane relative to us.
    3) Gravitational lensing (rare, and mostly suitable for very long distances).
    4) Direct imaging; the light reflected from the planet.

    Both 1 and 2 are best at detecting larger planets (as they dim the light more, and cause more wobbles). Planet of Earth mass are harder to detect. ISTR some planets have been detected by both 1 and 2, which is reasonable confirmation of the techniques. 3 is just weird. :)
    For 4, it has primarily been measuring the flux emitted by the planets themselves, they are too far away from their host star for reflected light.
    Thanks. IANAE. Just an interested observer. :)
    New space telescopes such as WFIRST will be looking for reflected light planets - the goal for those is to search for earth like planets. Currently direct imaging is focussed on looking for Jupiter-like planets which are still warm from their formation (~1000K compared to Jupiter's ~100K).
    Just as long as they don't get them this early:
    https://public.nrao.edu/static/pr/planet-formation-alma.html

    (That's one of my favourite astronomy images)
  • Options
    GeoffMGeoffM Posts: 6,071

    GeoffM said:

    slade said:

    By-election news: Lord Colgrain has won the by-election for hereditory peers. He beat 26 other candidates including Earl Stockton, Earl Lloyd-George, and Lord Harlech. Can honestly say I had never heard of him.

    Who, indeed, would be expected to have heard of a hereditary peerage created after WW2?
    Jobs for the boys.....
    Originally when the peerage was created - a Job for an Eton-educated banker!
  • Options
    jayfdeejayfdee Posts: 618
    Barnesian said:

    Mr. G, the nettle example was actually used by Spartan children. They were taken from their parents and 'educated' at an institution. I believe it was around 12 when they were given their first garment (one cloak). They were also given insufficient food to survive, and punished for stealing more (not for stealing, but for getting caught).

    My mother occasionally spoke of getting frost on the inside of the windows.

    Does put into perspective the nonsense of relative poverty.

    My sister and I used to amuse ourselves by breathing on frost covered windows in our bedroom and watching the frost reform in intricate fern shaped patterns.
    I have had the pleasure, sorry non pleasure, of camping in a tent at 20,000ft(sorry about the Imperial), and the frost on the inside was like snow, tap the fabric and you had a snowfall inside.
  • Options
    OmniumOmnium Posts: 9,796
    rcs1000 said:

    Ishmael_Z said:

    rcs1000 said:

    Ishmael_Z said:

    surbiton said:

    Ishmael_Z said:

    RobD said:

    RobD said:


    A parsec is the distance at which 1 au subtends 1 arcsecond on the sky. They are intimately linked.

    I am not denying that. What I am saying is that if I need to use parsecs then there is virtually point to using AUs for that measurement. If something is 2.2 M parsecs away then I will say that rather than 453,783,000,000 AUs

    But that doesn't change the fact it is the basis of the parsec ;)
    *sigh*

    Yes... you correct. It is the basis of the parsec

    But nobody measures stellar distance in AUs
    That is unnecessarily rude; you are the one missing the point, and making the erroneous statement in the first place that parsecs are metric.
    The parsec is no more metric than the metre. The metre is 1.6(ish) million wavelengths of light or the distance travelled by light in 1/299,000(ish) of a second. But it is divided up in a regular way just like the metre, milliparsecs, parsecs, kiloparsecs, megaparsecs gigaparsecs. We do not have an "oddball" conversion factor like 1 parfoot = 12 parsecs or 1 parinch = 1/36 of a parsec

    But surely the original "metre" was the distance from the North pole to the equator divided by 10000. Obviously, only the French could think like that.
    The most annoying number in the world, after Don Bradman's batting average, is the speed of light at 299 792 458 m / s. If only, if only we could redefine the metre as 1/300000000 of the distance light travels in a vacuum in 1 second.
    Surely if we simply changed the value of a second, that problem would solve itself.
    I believe there are nutters about who contend that the speed of light is not constant but changes over time. Either your change, or mine, would make it very difficult for them to formulate their claim..
    As an aside, I have also solved the problem of Bradman's average. If we simply change the number of runs gotten with a "4" to 4.062, then his average gets to 100.

    Of course, we'll need to go back an rescore all historic cricket matches, but I think you'll agree that is a small price to pay.
    If a bowler was automatically awarded 2 runs for every wicket he took then you'd not have to work so hard.
  • Options
    surbitonsurbiton Posts: 13,549
    Barnesian said:

    Ishmael_Z said:

    RobD said:

    RobD said:


    A parsec is the distance at which 1 au subtends 1 arcsecond on the sky. They are intimately linked.

    I am not denying that. What I am saying is that if I need to use parsecs then there is virtually point to using AUs for that measurement. If something is 2.2 M parsecs away then I will say that rather than 453,783,000,000 AUs

    But that doesn't change the fact it is the basis of the parsec ;)
    *sigh*

    Yes... you correct. It is the basis of the parsec

    But nobody measures stellar distance in AUs
    That is unnecessarily rude; you are the one missing the point, and making the erroneous statement in the first place that parsecs are metric.
    The parsec is no more metric than the metre. The metre is 1.6(ish) million wavelengths of light or the distance travelled by light in 1/299,000(ish) of a second. But it is divided up in a regular way just like the metre, milliparsecs, parsecs, kiloparsecs, megaparsecs gigaparsecs. We do not have an "oddball" conversion factor like 1 parfoot = 12 parsecs or 1 parinch = 1/36 of a parsec

    When I was the marketing manager of a major wallpaper brand, a roll of wallpaper measured half a long elephant. This was roughly 21" by 16' 6".

    On metrication I met with sales, production and distribution to agree the simplest metric units. After a long discussion, we agreed on 529mm by 4990mm.
    Why didn't someone just say let's make it 5000mm x 500mm ? 5m x 0.5m
  • Options
    AndyJSAndyJS Posts: 29,395
    Pong said:

    AndyJS said:

    Great to see NOP back again. What happened to Gallup, Harris and Angus Reid?

    Pb rule 108b;

    We don't talk about Angus Reid.
    Thanks for the tip.
  • Options
    OmniumOmnium Posts: 9,796
    surbiton said:

    Barnesian said:

    Ishmael_Z said:

    RobD said:

    RobD said:


    A parsec is the distance at which 1 au subtends 1 arcsecond on the sky. They are intimately linked.

    I am not denying that. What I am saying is that if I need to use parsecs then there is virtually point to using AUs for that measurement. If something is 2.2 M parsecs away then I will say that rather than 453,783,000,000 AUs

    But that doesn't change the fact it is the basis of the parsec ;)
    *sigh*

    Yes... you correct. It is the basis of the parsec

    But nobody measures stellar distance in AUs
    That is unnecessarily rude; you are the one missing the point, and making the erroneous statement in the first place that parsecs are metric.
    The parsec is no more metric than the metre. The metre is 1.6(ish) million wavelengths of light or the distance travelled by light in 1/299,000(ish) of a second. But it is divided up in a regular way just like the metre, milliparsecs, parsecs, kiloparsecs, megaparsecs gigaparsecs. We do not have an "oddball" conversion factor like 1 parfoot = 12 parsecs or 1 parinch = 1/36 of a parsec

    When I was the marketing manager of a major wallpaper brand, a roll of wallpaper measured half a long elephant. This was roughly 21" by 16' 6".

    On metrication I met with sales, production and distribution to agree the simplest metric units. After a long discussion, we agreed on 529mm by 4990mm.
    Why didn't someone just say let's make it 5000mm x 500mm ? 5m x 0.5m
    That sort of thing gets you sacked.
  • Options
    jayfdeejayfdee Posts: 618
    surbiton said:

    Barnesian said:

    Ishmael_Z said:

    RobD said:

    RobD said:


    A parsec is the distance at which 1 au subtends 1 arcsecond on the sky. They are intimately linked.

    I am not denying that. What I am saying is that if I need to use parsecs then there is virtually point to using AUs for that measurement. If something is 2.2 M parsecs away then I will say that rather than 453,783,000,000 AUs

    But that doesn't change the fact it is the basis of the parsec ;)
    *sigh*

    Yes... you correct. It is the basis of the parsec

    But nobody measures stellar distance in AUs
    That is unnecessarily rude; you are the one missing the point, and making the erroneous statement in the first place that parsecs are metric.
    The parsec is no more metric than the metre. The metre is 1.6(ish) million wavelengths of light or the distance travelled by light in 1/299,000(ish) of a second. But it is divided up in a regular way just like the metre, milliparsecs, parsecs, kiloparsecs, megaparsecs gigaparsecs. We do not have an "oddball" conversion factor like 1 parfoot = 12 parsecs or 1 parinch = 1/36 of a parsec

    When I was the marketing manager of a major wallpaper brand, a roll of wallpaper measured half a long elephant. This was roughly 21" by 16' 6".

    On metrication I met with sales, production and distribution to agree the simplest metric units. After a long discussion, we agreed on 529mm by 4990mm.
    Why didn't someone just say let's make it 5000mm x 500mm ? 5m x 0.5m
    Most seem to be about 10 metres now, suppose that was a full Elephant.
  • Options
    RobDRobD Posts: 58,985

    RobD said:

    RobD said:

    surbiton said:

    surbiton said:

    I would have thought parsecs refer to how much "angle" the object covers.

    The parsec is useful because it can be used in direct measurement. If star shows an annual parallax of 0.2 arcsecs then it is 1 / 0.2 = 5 parsecs away

    I see. Trigonometry. But surely a star very, very far away even after 6 months will not reveal much movement, or am I wrong ?
    The amount of movement is indeed very small, but is measurable. The Kepler satellite was able to make these measurements to discover planets of nearby stars.

    Also, see the Hipparcos satellite which determined the distances of the nearest 100,000 stars using this method

    https://en.wikipedia.org/wiki/Hipparcos
    From memory, there are several main mechanisms to detect an exoplanet:
    1) 'wobble' of a star's orbit (the gravitational effect of the planes)
    2) Dimunation of a star's light as a planet passes in front of it. This requires the star and planet to be on the same plane relative to us.
    3) Gravitational lensing (rare, and mostly suitable for very long distances).
    4) Direct imaging; the light reflected from the planet.

    Both 1 and 2 are best at detecting larger planets (as they dim the light more, and cause more wobbles). Planet of Earth mass are harder to detect. ISTR some planets have been detected by both 1 and 2, which is reasonable confirmation of the techniques. 3 is just weird. :)
    For 4, it has primarily been measuring the flux emitted by the planets themselves, they are too far away from their host star for reflected light.
    Thanks. IANAE. Just an interested observer. :)
    New space telescopes such as WFIRST will be looking for reflected light planets - the goal for those is to search for earth like planets. Currently direct imaging is focussed on looking for Jupiter-like planets which are still warm from their formation (~1000K compared to Jupiter's ~100K).
    Just as long as they don't get them this early:
    https://public.nrao.edu/static/pr/planet-formation-alma.html

    (That's one of my favourite astronomy images)
    Yes, very nice, and shows just how awesome ALMA is (thank God we aren't leaving ESA/ESO!)
  • Options
    BarnesianBarnesian Posts: 7,997
    surbiton said:

    Barnesian said:

    Ishmael_Z said:

    RobD said:

    RobD said:


    A parsec is the distance at which 1 au subtends 1 arcsecond on the sky. They are intimately linked.

    I am not denying that. What I am saying is that if I need to use parsecs then there is virtually point to using AUs for that measurement. If something is 2.2 M parsecs away then I will say that rather than 453,783,000,000 AUs

    But that doesn't change the fact it is the basis of the parsec ;)
    *sigh*

    Yes... you correct. It is the basis of the parsec

    But nobody measures stellar distance in AUs
    That is unnecessarily rude; you are the one missing the point, and making the erroneous statement in the first place that parsecs are metric.
    The parsec is no more metric than the metre. The metre is 1.6(ish) million wavelengths of light or the distance travelled by light in 1/299,000(ish) of a second. But it is divided up in a regular way just like the metre, milliparsecs, parsecs, kiloparsecs, megaparsecs gigaparsecs. We do not have an "oddball" conversion factor like 1 parfoot = 12 parsecs or 1 parinch = 1/36 of a parsec

    When I was the marketing manager of a major wallpaper brand, a roll of wallpaper measured half a long elephant. This was roughly 21" by 16' 6".

    On metrication I met with sales, production and distribution to agree the simplest metric units. After a long discussion, we agreed on 529mm by 4990mm.
    Why didn't someone just say let's make it 5000mm x 500mm ? 5m x 0.5m
    I suggested that, but Production said it would cost a lot to alter the width of the rollers. I was easily persuaded in those days. Still am, come to think of it.
  • Options
    Omnium said:

    rcs1000 said:

    Ishmael_Z said:

    rcs1000 said:

    Ishmael_Z said:

    surbiton said:

    Ishmael_Z said:

    RobD said:

    RobD said:


    A parsec is the distance at which 1 au subtends 1 arcsecond on the sky. They are intimately linked.

    I am not denying that. What I am saying is that if I need to use parsecs then there is virtually point to using AUs for that measurement. If something is 2.2 M parsecs away then I will say that rather than 453,783,000,000 AUs

    But that doesn't change the fact it is the basis of the parsec ;)
    *sigh*

    Yes... you correct. It is the basis of the parsec

    But nobody measures stellar distance in AUs
    That is unnecessarily rude; you are the one missing the point, and making the erroneous statement in the first place that parsecs are metric.
    The parsec is no more metric than the metre. The metre is 1.6(ish) million wavelengths of light or the distance travelled by light in 1/299,000(ish) of a second. But it is divided up in a regular way just like the metre, milliparsecs, parsecs, kiloparsecs, megaparsecs gigaparsecs. We do not have an "oddball" conversion factor like 1 parfoot = 12 parsecs or 1 parinch = 1/36 of a parsec

    But surely the original "metre" was the distance from the North pole to the equator divided by 10000. Obviously, only the French could think like that.
    The most annoying number in the world, after Don Bradman's batting average, is the speed of light at 299 792 458 m / s. If only, if only we could redefine the metre as 1/300000000 of the distance light travels in a vacuum in 1 second.
    Surely if we simply changed the value of a second, that problem would solve itself.
    I believe there are nutters about who contend that the speed of light is not constant but changes over time. Either your change, or mine, would make it very difficult for them to formulate their claim..
    As an aside, I have also solved the problem of Bradman's average. If we simply change the number of runs gotten with a "4" to 4.062, then his average gets to 100.

    Of course, we'll need to go back an rescore all historic cricket matches, but I think you'll agree that is a small price to pay.
    If a bowler was automatically awarded 2 runs for every wicket he took then you'd not have to work so hard.
    That would certainly improve the average of New Zealand ex-fast bowler Chris Martin.
  • Options
    rcs1000rcs1000 Posts: 54,031
    RobD said:

    RobD said:

    RobD said:

    surbiton said:

    surbiton said:

    I would have thought parsecs refer to how much "angle" the object covers.

    The parsec is useful because it can be used in direct measurement. If star shows an annual parallax of 0.2 arcsecs then it is 1 / 0.2 = 5 parsecs away

    I see. Trigonometry. But surely a star very, very far away even after 6 months will not reveal much movement, or am I wrong ?
    The amount of movement is indeed very small, but is measurable. The Kepler satellite was able to make these measurements to discover planets of nearby stars.

    Also, see the Hipparcos satellite which determined the distances of the nearest 100,000 stars using this method

    https://en.wikipedia.org/wiki/Hipparcos
    From memory, there are several main mechanisms to detect an exoplanet:
    1) 'wobble' of a star's orbit (the gravitational effect of the planes)
    2) Dimunation of a star's light as a planet passes in front of it. This requires the star and planet to be on the same plane relative to us.
    3) Gravitational lensing (rare, and mostly suitable for very long distances).
    4) Direct imaging; the light reflected from the planet.

    Both 1 and 2 are best at detecting larger planets (as they dim the light more, and cause more wobbles). Planet of Earth mass are harder to detect. ISTR some planets have been detected by both 1 and 2, which is reasonable confirmation of the techniques. 3 is just weird. :)
    For 4, it has primarily been measuring the flux emitted by the planets themselves, they are too far away from their host star for reflected light.
    Thanks. IANAE. Just an interested observer. :)
    New space telescopes such as WFIRST will be looking for reflected light planets - the goal for those is to search for earth like planets. Currently direct imaging is focussed on looking for Jupiter-like planets which are still warm from their formation (~1000K compared to Jupiter's ~100K).
    Just as long as they don't get them this early:
    https://public.nrao.edu/static/pr/planet-formation-alma.html

    (That's one of my favourite astronomy images)
    Yes, very nice, and shows just how awesome ALMA is (thank God we aren't leaving ESA/ESO!)
    I'm afraid HYUFD has spoken, and apparently there is no possibility we will pay to be members of any EU administered bodies.
  • Options
    BarnesianBarnesian Posts: 7,997
    jayfdee said:

    surbiton said:

    Barnesian said:

    Ishmael_Z said:

    RobD said:

    RobD said:


    A parsec is the distance at which 1 au subtends 1 arcsecond on the sky. They are intimately linked.

    I am not denying that. What I am saying is that if I need to use parsecs then there is virtually point to using AUs for that measurement. If something is 2.2 M parsecs away then I will say that rather than 453,783,000,000 AUs

    But that doesn't change the fact it is the basis of the parsec ;)
    *sigh*

    Yes... you correct. It is the basis of the parsec

    But nobody measures stellar distance in AUs
    That is unnecessarily rude; you are the one missing the point, and making the erroneous statement in the first place that parsecs are metric.
    The parsec is no more metric than the metre. The metre is 1.6(ish) million wavelengths of light or the distance travelled by light in 1/299,000(ish) of a second. But it is divided up in a regular way just like the metre, milliparsecs, parsecs, kiloparsecs, megaparsecs gigaparsecs. We do not have an "oddball" conversion factor like 1 parfoot = 12 parsecs or 1 parinch = 1/36 of a parsec

    When I was the marketing manager of a major wallpaper brand, a roll of wallpaper measured half a long elephant. This was roughly 21" by 16' 6".

    On metrication I met with sales, production and distribution to agree the simplest metric units. After a long discussion, we agreed on 529mm by 4990mm.
    Why didn't someone just say let's make it 5000mm x 500mm ? 5m x 0.5m
    Most seem to be about 10 metres now, suppose that was a full Elephant.
    A long elephant. http://bit.ly/2o36Edc
  • Options
    MortimerMortimer Posts: 13,951
    rcs1000 said:

    RobD said:

    RobD said:

    RobD said:

    surbiton said:

    surbiton said:

    I would have thought parsecs refer to how much "angle" the object covers.

    The parsec is useful because it can be used in direct measurement. If star shows an annual parallax of 0.2 arcsecs then it is 1 / 0.2 = 5 parsecs away

    I see. Trigonometry. But surely a star very, very far away even after 6 months will not reveal much movement, or am I wrong ?
    The amount of movement is indeed very small, but is measurable. The Kepler satellite was able to make these measurements to discover planets of nearby stars.

    Also, see the Hipparcos satellite which determined the distances of the nearest 100,000 stars using this method

    https://en.wikipedia.org/wiki/Hipparcos
    From memory, there are several main mechanisms to detect an exoplanet:
    1) 'wobble' of a star's orbit (the gravitational effect of the planes)
    2) Dimunation of a star's light as a planet passes in front of it. This requires the star and planet to be on the same plane relative to us.
    3) Gravitational lensing (rare, and mostly suitable for very long distances).
    4) Direct imaging; the light reflected from the planet.

    Both 1 and 2 are best at detecting larger planets (as they dim the light more, and cause more wobbles). Planet of Earth mass are harder to detect. ISTR some planets have been detected by both 1 and 2, which is reasonable confirmation of the techniques. 3 is just weird. :)
    For 4, it has primarily been measuring the flux emitted by the planets themselves, they are too far away from their host star for reflected light.
    Thanks. IANAE. Just an interested observer. :)
    New space telescopes such as WFIRST will be looking for reflected light planets - the goal for those is to search for earth like planets. Currently direct imaging is focussed on looking for Jupiter-like planets which are still warm from their formation (~1000K compared to Jupiter's ~100K).
    Just as long as they don't get them this early:
    https://public.nrao.edu/static/pr/planet-formation-alma.html

    (That's one of my favourite astronomy images)
    Yes, very nice, and shows just how awesome ALMA is (thank God we aren't leaving ESA/ESO!)
    I'm afraid HYUFD has spoken, and apparently there is no possibility we will pay to be members of any EU administered bodies.
    Darn.

    I guess that means Hilary Benn will definitely be Labour's Michael Howard to Corbyn's IDS, too.

  • Options
    RobDRobD Posts: 58,985
    rcs1000 said:

    RobD said:

    RobD said:

    RobD said:

    surbiton said:

    surbiton said:

    I would have thought parsecs refer to how much "angle" the object covers.

    The parsec is useful because it can be used in direct measurement. If star shows an annual parallax of 0.2 arcsecs then it is 1 / 0.2 = 5 parsecs away

    I see. Trigonometry. But surely a star very, very far away even after 6 months will not reveal much movement, or am I wrong ?
    The amount of movement is indeed very small, but is measurable. The Kepler satellite was able to make these measurements to discover planets of nearby stars.

    Also, see the Hipparcos satellite which determined the distances of the nearest 100,000 stars using this method

    https://en.wikipedia.org/wiki/Hipparcos
    From memory, there are several main mechanisms to detect an exoplanet:
    1) 'wobble' of a star's orbit (the gravitational effect of the planes)
    2) Dimunation of a star's light as a planet passes in front of it. This requires the star and planet to be on the same plane relative to us.
    3) Gravitational lensing (rare, and mostly suitable for very long distances).
    4) Direct imaging; the light reflected from the planet.

    Both 1 and 2 are best at detecting larger planets (as they dim the light more, and cause more wobbles). Planet of Earth mass are harder to detect. ISTR some planets have been detected by both 1 and 2, which is reasonable confirmation of the techniques. 3 is just weird. :)
    For 4, it has primarily been measuring the flux emitted by the planets themselves, they are too far away from their host star for reflected light.
    Thanks. IANAE. Just an interested observer. :)
    New space telescopes such as WFIRST will be looking for reflected light planets - the goal for those is to search for earth like planets. Currently direct imaging is focussed on looking for Jupiter-like planets which are still warm from their formation (~1000K compared to Jupiter's ~100K).
    Just as long as they don't get them this early:
    https://public.nrao.edu/static/pr/planet-formation-alma.html

    (That's one of my favourite astronomy images)
    Yes, very nice, and shows just how awesome ALMA is (thank God we aren't leaving ESA/ESO!)
    I'm afraid HYUFD has spoken, and apparently there is no possibility we will pay to be members of any EU administered bodies.
    I believe they are independent bodies, the EU hasn't absorbed them quite yet.
  • Options
    FrancisUrquhartFrancisUrquhart Posts: 76,285
    edited March 2017
    Rachel Dolezal - the white US woman who said she was black - says "the idea of race is a lie".

    Speaking in an interview with Emily Maitlis, she argued that the concept of "transracial" - similar to that of transgender - is useful in describing people such as herself.

    http://www.bbc.co.uk/news/world-us-canada-39410805

    Looks like LGBTIQ....is going to need some more letters...I suggest N....for Nutter.
  • Options
    TheWhiteRabbitTheWhiteRabbit Posts: 12,388

    Rachel Dolezal - the white US woman who said she was black - says "the idea of race is a lie".

    Speaking in an interview with Emily Maitlis, she argued that the concept of "transracial" - similar to that of transgender - is useful in describing people such as herself.

    http://www.bbc.co.uk/news/world-us-canada-39410805

    Looks like LGBTIQ....is going to need some more letters...

    Those two statements are contradictory already.
This discussion has been closed.