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originally posted by: anonentity
a reply to: Hanslune
When all is said and done, do you really need longitude except for placing a landmass on a map? Lattitude is easy enough to work out, then all you have to do is decide if it's left or right. In the old sailing ships from Britain, it was sail south till the butter melts and then turn right. You always ended up in the Caribean as long as you didn't sink.
originally posted by: anonentity
a reply to: Hanslune
Yes point taken, dead reckoning has its limitations. But you can still clear Cape horn by latitude, just by making sure you are well off.
originally posted by: Harte
originally posted by: bloodymarvelous
originally posted by: Harte
originally posted by: bloodymarvelous
If we want to go back on topic: do you think the Torquetum was invented by Aristothenes? Or do you think he found it in one of the many books the library kept?
No. That instrument dates no earlier that the 12th Century AD.
originally posted by: bloodymarvelousCould an extremely ancient civilization have had the technology to determine longitude, long prior to the invention of reliable clocks?
No. And you can't use the torquetum to establish longitude.
You're right. I confused the words "Tanawa" and "Torquetum".
Apparently the purpose of the "Tanawa" was to allow you to accurately measure the Moon's position in the sky, and then knowing what day it is, you could calculate what hour it was by looking at the stars behind the Moon.
Knowing the correct time is what allows navigators to determine their longitude (unless they have GPS, in which case they would use that today.)
In order to find longitude on a trip, you have to know what time it is at a different, known, longitude - such as the longitude of the spot your trip began from - at the moment of your observation.
You also have to have a system of latitude and longitude, which the ancients certainly didn't have.
Harte
originally posted by: anonentity
a reply to: fromunclexcommunicate
Harte says you can't get longitude without a clock. But the rising of the stars and the position of the moon and the sun are the hands of a celestial clock. Better than a mechanical clock as it's the real thing, not a proxy. All the angles are peculiar to your position on the globe at that particular time of the year.
So the question would be how much did the ancient navigators know, did they just calculate in degrees or minutes and seconds. Because if they calculated in Minutes of arc, they must have had some way to do the timing, as they would have known that a degree is sixty nautical miles on the earth's surface measured from its center anywhere on the surface. Which makes a minute as a sixtieth of that which is, of course, one nautical mile.
originally posted by: Hanslune
originally posted by: Harte
originally posted by: anonentity
a reply to: fromunclexcommunicate
Harte says you can't get longitude without a clock. But the rising of the stars and the position of the moon and the sun are the hands of a celestial clock. Better than a mechanical clock as it's the real thing, not a proxy. All the angles are peculiar to your position on the globe at that particular time of the year.
Harte points out that, although you can tell time at sea, you can't get your longitude from what time it is.
Harte thinks you need to learn about how longitude is calculated.
Harte
There is a way to measure longitude without a clock but it requires that you can observe the full moon when you are near the equator (don't recall the 'safe area'). Not to sure how useful that would be in the real world and it would be difficult to do in a bobbing boat but is possible if on land and have a stable base and accurate enough equipment and have a previously obtain information on the angles of the moon and a star that can be observed.
academic.oup.com...
originally posted by: anonentity
a reply to: Hanslune
When all is said and done, do you really need longitude except for placing a landmass on a map? Lattitude is easy enough to work out, then all you have to do is decide if it's left or right. In the old sailing ships from Britain, it was sail south till the butter melts and then turn right. You always ended up in the Caribean as long as you didn't sink.
originally posted by: Harte
originally posted by: Hanslune
originally posted by: Harte
originally posted by: anonentity
a reply to: fromunclexcommunicate
Harte says you can't get longitude without a clock. But the rising of the stars and the position of the moon and the sun are the hands of a celestial clock. Better than a mechanical clock as it's the real thing, not a proxy. All the angles are peculiar to your position on the globe at that particular time of the year.
Harte points out that, although you can tell time at sea, you can't get your longitude from what time it is.
Harte thinks you need to learn about how longitude is calculated.
Harte
There is a way to measure longitude without a clock but it requires that you can observe the full moon when you are near the equator (don't recall the 'safe area'). Not to sure how useful that would be in the real world and it would be difficult to do in a bobbing boat but is possible if on land and have a stable base and accurate enough equipment and have a previously obtain information on the angles of the moon and a star that can be observed.
academic.oup.com...
Requires a previously existing system of longitude.
You can't locate your longitude on the Earth's surface unless you know the longitude of the place you started from.
Harte
Harte
originally posted by: Harte
originally posted by: Hanslune
originally posted by: Harte
originally posted by: anonentity
a reply to: fromunclexcommunicate
Harte says you can't get longitude without a clock. But the rising of the stars and the position of the moon and the sun are the hands of a celestial clock. Better than a mechanical clock as it's the real thing, not a proxy. All the angles are peculiar to your position on the globe at that particular time of the year.
Harte points out that, although you can tell time at sea, you can't get your longitude from what time it is.
Harte thinks you need to learn about how longitude is calculated.
Harte
There is a way to measure longitude without a clock but it requires that you can observe the full moon when you are near the equator (don't recall the 'safe area'). Not to sure how useful that would be in the real world and it would be difficult to do in a bobbing boat but is possible if on land and have a stable base and accurate enough equipment and have a previously obtain information on the angles of the moon and a star that can be observed.
academic.oup.com...
Requires a previously existing system of longitude.
You can't locate your longitude on the Earth's surface unless you know the longitude of the place you started from.
Harte
Harte
originally posted by: anonentity
a reply to: Harte
Also bearing in mind that a voyaging canoe was made out of wood, if they were in an inferno of bad weather it just filled up with water and you hung on till it passed. If the hulls filled up you were stable. Then you bailed it out and if you still had a mast sailed on, if you didn't you rowed. They were also fast so time at sea and the risk of bad weather problems were lessened. Cook saw an outrigger doing about eighteen knots in Hawai, and was dumbstruck. Also, the arctic tern leaves Alaska in winter and heads for New Zealand, if you followed their migration pattern you were going to end up where they rested.
We think in terms of metals and plastics, but a good carpenter will tell you there is a wood for most practicable applications. Even things like sextants. Bearings etc. They had lathes back then as you can see the centering marks on those Dendera Bowles, so who really knows.
Cook observed that the Tahitian pahi could sail faster than the Endeavour: “...their Large canoes sails much faster than this Ship, all this I believe to be true & therefore they may with Ease sail 40 Leagues a day or more
It must have been a terrible place to risk the wide pacific not knowing if you were even going to make it.