Posts by ChrisW
Last ←Newer Page 1 2 3 4 5 Older→ First
-
Lake Paringa blues again - sky, shadows and reflections thereof.
-
Capture: Got the blues, in reply to BenWilson,
Trust you've had a well-earned sleep after that, Ben. I work differently - have to let someone be wrong on the internet after 10pm, and generally (really should!) even if it's myself or my own unfinished business if I want to sleep.
When beyond "terrestrial" heights, it becomes clearer your formulation measuring the eye-horizon straightline distance is not what we usually think of as the distance of interest, the map/chart-distance over the surface of the earth. In the case of your 100,000 km eye-height, the 'real' horizon distance would be just a little under your quarter of 40,000 km approximation to the earth circumference.
(Metre intended to be a 10- *millionth* of that pole-equator meridian - but one of the guys Mechain who did the precision survey work in the 1790s lost much sleep over an error he knew about - went back to northern Spain to fix it and died in the attempt. Good story, read the book - lost in the mental archives for now. Upshot - the standard metre was a poorer approximation to the earth's dimension than intended, 6366 km not the best radius to use. But good for checking the numbers from first principles!)
Not even blue-skies research!
-
Speaking of persons on another planet, curvature and all that – I was surprised this afternoon to see these curved posters neatly interpolated with those advertising exhibitions on at Tairawhiti Museum.
Coastal peoples were aware of the curvature of the earth and hence its mysterious spherical shape from the time of coastal sea-faring, where canoes, small boats and ships gradually disappear over the horizon yet appear again if one climbs a modest sand dune or small hill. The idea that Europeans at least thought Earth to be flat in mediaeval times pre-Columbus is a lie or a myth if you prefer, invented in the 19th century.
Totally unhelpful to denigrate Climate Change/AGW denialists as flat-earthers etc – but you do have to wonder what planet they are on and wonder at the imagery they use on these posters. And why is this *orator*, a stranger to the truth as well as science, given space to advertise a commercial venture on our ratepayer-funded museum/art gallery’s site? I’ll be making enquiries.
-
In reply to Ben -
Truth is stranger than fiction. I looked this one up before I wrote it,
And what planet are you on? Apparently planet Kulthea! Strange to say - you looked up fiction in the quest for truth! ;-)
Fortunately, Kulthea has only a slightly larger radius than planet Earth. So the horizon distances on Earth are near enough those on Kulthea, a little shorter e.g. 4.8 km for your 1.8 m eye height rather than 5.0 km.And David's formula -
I'll back up Ben's general math about horizon distance, the formula is
SquareRoot(eye height above water in cm / 6.752) = distance to horizon in kmcomes from another slightly larger planet than ours too. Replace 6.752 with 7.848 for Earth.
The mathematically inclined are less likely to mistake their planet if working nearer to first principles. Horizon distance y = SQRT (2r*h) where 2r is Earth's diameter (mean diameter 12742 km) and observer/eye height h in the same units - this is the quadratic formula y squared = 2rh as an approximation to the arc of a circle, accurate for practical purposes for all human to mountain-scale heights.
Square root of 12742 km * 0.0018 km = 4.79 km.
For David's formulation - 100,000 cm/km / 12742 km = 7.848 rather than 6.752And of course - yachts, ships "hull-down" on/over the horizon are absolutely normal everyday stuff, nothing surprising, whereas substantial mirages rely on strongly stratified air temperature variations close to the sea surface, which is not going to happen in the Hauraki Gulf in the middle of a mild onshore breezy day in late summer with warm sea surface temperatures.
-
Capture: Got the blues, in reply to Biobbs,
No need for an oops - and your photo certainly not repetitious (though far be it from me to suggest anything of the sort?)
Good to know the site too. Do you know Kendrick Smithyman's poem 'Tomarata'? I've been to similar places perhaps in the North, but feel I know much about (Lake) Tomarata the place as itself as well as more broadly from this great poem. Actually going there is on the list too.
-
West Coast again, harakeke and kahikatea and all. The blue sky amplified by reflection in the dark water of Lake Paringa.
-
Capture: Got the blues, in reply to Biobbs,
Harakeke a surprise from Denmark - and surprisingly narrow upright blades - I wondered whether this might be a response to Danish winters.
But then, aha! - I see evidence of a (SI) West Coast context for such a photo from a previous post of yours.
Not Danish harakeke in the Danish blue ... -
This one doesn't need any words, but I have to write something or my photo won't load. What shall I do?
-
Otago colours again, but at home - kowhai/golden yellow against the high window.
-
Capture: Got the blues, in reply to Alan Macdougall,
Good Otago colours!
Here too. Wireless is all that's needed for communications at Styx, beyond the Maniatoto.Richard Langston had an excellent 17 min interview with Brian Turner on radio this Sunday Morning, including his reading three short poems. "Crypt" towards the end of those 17 mins ending with "enabling us to see into the blue crypt beyond" - and subsequent discussion of this and the aura of infinity around blue, blue skies and Central Otago blue skies.
Brought to mind (many things, but in particular) this image of mainly the blue sky at Styx. Much better than Stygian black?
