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#31
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Lat/Long and timekeeping system for Mars
On Tuesday, December 4, 2018 at 11:39:31 AM UTC-7, Gerald Kelleher wrote:
I am sure the ISIS branch of astronomy would find 'sidereal vs solar' convictions acceptable We have not come to destroy, but to fulfill. John Savard |
#32
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Lat/Long and timekeeping system for Mars
On Tue, 4 Dec 2018 21:27:54 -0800 (PST), Quadibloc
wrote: But I'm talking about trying to be understood by people who are not astronomers. And to ordinary people, a "day" is a unit of time between successive periods of light or of dark, without rotation even entering into their thoughts. I don't disagree. But the page you were complaining about was specifically written to educate people about an astronomical concept! |
#33
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Lat/Long and timekeeping system for Mars
On Tuesday, December 4, 2018 at 10:37:17 PM UTC-7, Chris L Peterson wrote:
I don't disagree. But the page you were complaining about was specifically written to educate people about an astronomical concept! That's true. But if they *need* educating, then they aren't already educated when they start reading it. So, in order that they can understand what the page says, so they can learn something from it, it should be written in language that makes sense to them. John Savard |
#34
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Lat/Long and timekeeping system for Mars
Mars will have its own distinct hours minutes and seconds values where the Equatorial speed will be 889.3 km per Martian hour just as the Earth's Equatorial speed is 1,669.8 km per Earth hour.
Only a small subculture prevents a system being applied to Mars and more importantly, the stranglehold of an RA/Dec system which by itself is fine for certain tasks but useless for timekeeping, planetary geometry and rotation just as it is for this planet. "The application of a Timekeeper to this discovery is founded upon the following principles: the earth's surface is divided into 360 equal parts (by imaginary lines drawn from North to South) which are called Degrees of Longitude; and its daily revolution Eastward round its own axis is performed in 24 hours; consequently in that period, each of those imaginary lines or degrees, becomes successively opposite to the Sun (which makes the noon or precise middle of the day at each of those degrees and it must follow, that from the time any one of those lines passes the Sun, till the next passes, must be just four minutes, for 24 hours being divided by 360 will give that quantity; so that for every degree of Longitude we sail Westward, it will be noon with us four minutes the later, and for every degree Eastward four minutes the sooner, and so on in proportion for any greater or less quantity. Now, the exact time of the day at the place where we are, can be ascertained by well known and easy observations of the Sun if visible for a few minutes at any time from his being ten degrees high until within an hour of noon, or from an hour after noon until he is only 10 degrees high in the afternoon; if therefore, at any time when such observation is made, a Timekeeper tells us at the same moment what o'clock it is at the place we sailed from, our Longitude is clearly discovered." John Harrison |
#35
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Lat/Long and timekeeping system for Mars
On Tue, 04 Dec 2018 13:03:36 -0500, Davoud wrote:
I must confess that I have never heard of a "sidereal hour;" Then you haven't computed the local altitude or azimuth for a celestial object either, or it's rise and set time. When doing so, sidereal time is useful. When doing so for the Sun, you can avoid sidereal time by using the Equation of Time instead. https://en.wikipedia.org/wiki/Sidereal_time Nowadays planetarium software takes care of these details for most stargazers, who are happily unaware of the software's use of sidereal time. no such interval exists in the Système international. An hour is an hour is an hour, 3600 seconds. It is the second that is the base unit of time in SI units, not the hour, which is too broad a brush. True. Solar time does not exist in SI either. Only atomic time is defined in the SI system of units. And if you want to strictly follow SI, you should avoid using minutes, hours, days, months, years and instead use KS, Ms, Gs, Ts, etc etc. One day = 86.4 ks One year = ca 31.56 Ms One human lifetime = ca 2.6 Gs The age of the universe = ca 0.43 Ps Sidereal and solar hours aren't the only non-SI units used by astronomers. We also have the stellar magnitude (apparent, absolute and bolometric) , the light year and the parsec, solar masses, Earth masses and the Astronomical Unit. There are probably more non-SI units used by astronomers. What about giving a stars apparent brightness in nanolux instead of its visual magnitude? Or it's absolute brightness in Petalumens? Or it's bolometric brightness in PW? That's whar we would have to do if we were to strictly use only SI units. |
#36
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Lat/Long and timekeeping system for Mars
The system of equal hours,minutes and seconds is anchored in the creation of the 24 hour day which in turn is anchored to the noon cycle (day/night). The mean value relies on the mathematical principle that when different amounts are combined and divided equally they give an average or mean value, in this case what would be different hours,minutes and seconds for each noon cycle is reduced to an average or constant value.
The deficient observers launches into impressive values with multiples decimal places with first identifying where the 24 hour day comes from, what references are used and how it relates timekeeping to geometry/geography via longitude and Latitude. To create a geostationary satellite system for Mars requires the planet have its own timekeeping system constructed around the planet's Lat/Long system and although the latter is easy enough to construct, the Martian hour is not. Considering the hapless go out of their way to promote the idea that the Earth has more rotations than 24 hour days (day/night cycles) as their system demands it, there is every reason to put our planet's timekeeping evolution in historical and technical context. |
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Lat/Long and timekeeping system for Mars
On Wednesday, December 5, 2018 at 7:44:02 AM UTC, Paul Schlyter wrote:
On Tue, 04 Dec 2018 13:03:36 -0500, Davoud wrote: I must confess that I have never heard of a "sidereal hour;" Then you haven't computed the local altitude or azimuth for a celestial object either, or it's rise and set time. When doing so, sidereal time is useful. When doing so for the Sun, you can avoid sidereal time by using the Equation of Time instead. https://en.wikipedia.org/wiki/Sidereal_time Even after two decades, it is remarkable how the hapless still try to justify a direct link between the planet's rotation with celestial sphere rotation and then attempt to paste in a 24 noon cycle as an afterthought. The Lat/Long system for both the Earth and Mars is based on the average 24 hour noon cycle as no two cycles are alike. The background stars only form the basis of a calendar framework and even then it is strictly the transition from evening to morning appearance parallel to the orbital plane and minus celestial sphere rotation. All this thread has shown is nobody is up to the job which correlates one Martian hour with 15 degrees of rotation for that planet, something a GPS system requires to make sense of location on the planet. |
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Lat/Long and timekeeping system for Mars
On Wednesday, December 5, 2018 at 5:56:49 AM UTC-7, Gerald Kelleher wrote:
Even after two decades, it is remarkable how the hapless still try to justify a direct link between the planet's rotation with celestial sphere rotation and then attempt to paste in a 24 noon cycle as an afterthought. The only thing that's remarkable is that even after two decades, you haven't realized there's nothing wrong with this, and you're the one who is mistaken. John Savard |
#39
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Lat/Long and timekeeping system for Mars
Clearly the other contributors to this thread are neither mathematicians nor astronomers. The sample mean for variations in the natural noon cycle amount to 24 hours as each cycle when the Sun crosses the observer's meridian is not 24 hours.
https://en.wikipedia.org/wiki/Arithmetic_mean The average 24 hour day for Mars will also be derived from the same inequalities in the natural noon cycle but a Martian hour, Martian minute and Martian second within that average will be entirely different yet will mesh with the planet's 360 degree Latitude and Longitude system organised around the planet's Equator. This will be the structure of a GPS system for vehicles on Mars or other purposes. You guys continue with theoretical stuff that nobody can admire but this great endeavour is for those who actually appreciate how the system on Earth was put together. |
#40
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Lat/Long and timekeeping system for Mars
Davoud:
I must confess that I have never heard of a "sidereal hour;" Paul Schlyter: Then you haven't computed the local altitude or azimuth for a celestial object either, or it's rise and set time. When doing so, sidereal time is useful. When doing so for the Sun, you can avoid sidereal time by using the Equation of Time instead. https://en.wikipedia.org/wiki/Sidereal_time Nowadays planetarium software takes care of these details for most stargazers, who are happily unaware of the software's use of sidereal time. I have done all of that. Perhaps I used the wrong nomenclature? Sidereal Hour Angle. I am happily aware of TheSkyX Pro's use of sidereal time, but I am also happy to let TheSkyX Pro take care of the math while I enjoy the view.* no such interval exists in the Système international... It is the second that is the base unit of time in SI units, not the hour, which is too broad a brush. And if you want to strictly follow SI, you should avoid using minutes, hours, days, months, years and instead use KS, Ms, Gs, Ts, etc etc. One day = 86.4 ks One year = ca 31.56 Ms One human lifetime = ca 2.6 Gs The age of the universe = ca 0.43 Ps In this case I interpret "strictly" as "dogmatically" I can't bring myself to tell my neighbor "I'm taking a short vacation; I'll be back in about 604.8 ks." *Figuratively speaking. Due to macular degeneration I do not look through telescopes any more. I can still focus on a laptop display, however https://www.flickr.com/photos/primeval/30364292358, https://www.flickr.com/photos/primeval/29296501697. -- I agree with almost everything that you have said and almost everything that you will say in your entire life. usenet *at* davidillig dawt cawm |
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