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#11
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Isolating the direction of the Earth's orbital motion
Reed Riddle wrote in message ...
The Earth rotates in 23h 56m 4s with respect to the stars (and galaxies and quasars). That is all that matters. 1 axial rotation through 360 degrees = 23 hours 56 min 04 sec 2 axial rotations through 360 degrees = 47 hours 52 min 08 sec I assure anyone who checks using a stopwatch that it is a mathematical and astronomical certainty that a star will NOT return to the same position in the sky after 47 hours 52 min 08 sec (which corresponds to 2 sidereal days). The conclusion is simple,Flamsteed's 1677 premise and method of proof for determining the constant axial rotation of the Earth is incorrect. [Mod. note: this is getting a little close to `because I say so' speculation. Any more assertions that all modern observational astronomy is wrong should perhaps be justified with argument -- mjh] |
#12
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Isolating the direction of the Earth's orbital motion
In message , Oriel36
writes I have requested an astronomer of distinction to handle a heliocentric treatment of the material,despite the fact that it is not at all difficult to determine the disasterous maneuvering of Flamsteed no such astronomer has come forward.I cannot therefore be faulted for taking it to a group of people who can handle the material which predates the gravitational agenda of Newton and resolve the issue as to why there exists dual rotation rates for the Earth and why the 23 hour 56 min 04 sec value and the method by which that value is ascertained is incorrect. Instead of flogging this dead horse any more, could you post Flamsteed's text, instead of links to a simplified description of sidereal time and an even more simplified picture of an elliptical orbit. Your links don't mention him. For the umpteenth time (Hah - my spell checker accepts that :-) the 23 hour 56 minute 04 second value is measured, and the 24 hour value is a convention to allow days and hours of constant length. I've been corrected as to whether Newton was writing about relativity (and I'm rather disappointed !) but he did understand the Equation of Time. [Mod. note: quoted text trimmed -- mjh] -- What have they got to hide? Release the Beagle 2 report. Mail to jsilverlight AT merseia.fsnet.co.uk is welcome. |
#13
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Isolating the direction of the Earth's orbital motion
Jonathan Silverlight wrote in message ...
In message , Oriel36 writes I have requested an astronomer of distinction to handle a heliocentric treatment of the material,despite the fact that it is not at all difficult to determine the disasterous maneuvering of Flamsteed no such astronomer has come forward.I cannot therefore be faulted for taking it to a group of people who can handle the material which predates the gravitational agenda of Newton and resolve the issue as to why there exists dual rotation rates for the Earth and why the 23 hour 56 min 04 sec value and the method by which that value is ascertained is incorrect. Instead of flogging this dead horse any more, could you post Flamsteed's text, instead of links to a simplified description of sidereal time and an even more simplified picture of an elliptical orbit. Your links don't mention him. Here is the basis of the Flamsteed's incorrect procedure. http://www.burnley.gov.uk/towneley/tryall/eot1.htm For the umpteenth time (Hah - my spell checker accepts that :-) the 23 hour 56 minute 04 second value is measured, and the 24 hour value is a convention to allow days and hours of constant length. It is required to determine the equable 24 hour day First in order to determine the Earth's orbital period as 365 days 5 hours 49 min on which the sidereal reasoning is based. http://www.burnley.gov.uk/towneley/tryall/eot3.htm Somehow you fail to comprehend that the assumption of constant axial rotation through 360 degrees existed as the 24 hour/360 degree equivalency centuries before Flamsteed,the principles of developing accurate clocks for solving the Longitude problem are based on the 24 hour/360 degree longitude equivalency are based on the assumption of constant axial rotation. You cannot prove by direct observation that the Earth axially rotates through 360 degrees in 24 hours,what you can do is assume constant axial rotation and use the Equation of Time adjustment to equalise the variations over the course of an annual orbit. There are no 'leap' factors in the Equation of Time,it simply facilitates the seamless transition from one 24 hour day to the next by the appropriate addition and subtraction of minutes and seconds for each axial rotation in order to maintain the 24 hour/360 degree longitude equivalency. I've been corrected as to whether Newton was writing about relativity (and I'm rather disappointed !) but he did understand the Equation of Time. [Mod. note: quoted text trimmed -- mjh] I have seen the correction and it is incorrect.Newton knew the principles behind accurate clocks for solving the Longitude problem and doubted that such an accurate mechanism could be constructed.The benchmark for clock accuracy in Newton's era was the noon determination and the Equation of Time application therefore the principles which dictate constant axial rotation to the longitude equivalency are permanently fixed to the geometry and geography of the planet and its rotation It was unethical of Flamsteed to piggyback on this already existing assumption of constant axial rotation in accordance with the principles of longitude and clocks.He transfers or rather hides an axial rotational coordinate to an orbital .986 degree/3 min 56 sec orbital coordinate,great if you wish to catalogue stars based on a stellar circumpolar framework or condition celestial motion into the civil calendar but ultimately destroys the work of Kepler and the exquisite Equation of Time correlation between the natural unequal day and the 24 hour clock day. http://astrosun2.astro.cornell.edu/a...1/sidereal.htm If you wish to adhere to Flamsteed's reasoning,the above graphic is an astronomical justification of it.It is a poor choice. |
#14
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Isolating the direction of the Earth's orbital motion
In message , Oriel36
writes You cannot prove by direct observation that the Earth axially rotates through 360 degrees in 24 hours,what you can do is assume constant axial rotation and use the Equation of Time adjustment to equalise the variations over the course of an annual orbit. People measure the rotation of the Earth all the time, for many different reasons and to a high degree of accuracy. The name Foucault comes to mind, both for his pendulum and his naming of the gyroscope. He'd probably have been fascinated by Gravity Probe B. |
#16
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Isolating the direction of the Earth's orbital motion
Jonathan Silverlight wrote in message ...
the 23 hour 56 minute 04 second value is measured, and the 24 hour value is a convention to allow days and hours of constant length. The length of the mean solar day is measured to be 24 hours, and not assigned by convention. If the mean solar day were significantly different from 24 hours, then with respect to our good clocks that repeat their indications every 24 hours, we would soon see the Sun rising and setting at strange hours. Of course, the mean solar day is not *exactly* 24 hours, i.e., 86400 seconds where the second is defined in terms of the frequency of a certain atomic vibration. The difference is small, so that after roughly 100 intervals of exactly 24 hours each, an angular discrepancy corresponding to one second of time will have accrued ("leap second"). For the benefit of the original poster, the shortness of the sideral day with respect to the mean solar day can be calculated by noting that in a given amount of time, namely one year, the Earth makes 365.25 turns from the point of view of the Sun, and 366.25 turns from the point of view of the distant stars. The extra turn in the stars' viewpoint is the turn the Earth makes by orbiting the Sun. According to the same effect, in one month the Moon makes one more turn in the view of the stars than it does in the view of the Earth. (For a total of one turn per month in the view of the stars: as all know, the Moon makes zero turns per month in the view of the Earth because its rotation has been stopped by tidal effects.) So, (3 min, 56 s per day) x 366.25 days = 24.010 hours. The "equation of time" referred to by the original poster is somewhat unrelated. The amount of time from noon to noon, i.e., the solar day, varries throughout the year. Somes days are shorter and some longer than 24 hours, while 24 hours is the average taken over one year. The discrepancy is as large as a few minutes. The variation is caused, in roughly equal amounts, by the ellipticity of the Earth's orbit and the inclination of the Earth's rotation axis with respect to the plane of its orbit. These irregularities are taken into account by the equation of time. Sundial readings, corrected with the equation of time, give local mean time. With an additional adjustment for longitude (and daylight savings time if it is in effect), sundial readings then agree with the civil time kept by 24 hour, atomic-second clocks. The amount of time from one meridian transit of a star to the next transit of that star (this would be "noon" as defined by a star) shows very little variation. So little as to be not possible to detect directly until the advent of atomic clocks. With the greatest regularity, this time is 23h 56m 4s. If the Earth's axis were not inclined and its orbit not eccentric, there would be no equation of time effect, but the solar day would still be longer than the sideral day. -Arnie |
#17
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Isolating the direction of the Earth's orbital motion
[Mod. note: this thread seems to be getting repetitive. Please
consider whether you have anything new to say before posting -- mjh] (Arnie King) wrote in message ... If the Earth's axis were not inclined and its orbit not eccentric, there would be no equation of time effect, but the solar day would still be longer than the sideral day. -Arnie This is incorrect in terms of the axial and orbital motions of the Earth,the natural observational limitation dictate that these combined motion can only be isolated seperately as assumptions and especially in relation to the Sun. The Earth's axial orientation and therefore its equatorial orientation remains constant as a property of the Earth's axial rotation which is independent of orbital motion .The time lapse image against Polaris and stellar circumpolar motion adequately demonstrates this - http://ottawa.rasc.ca/pictures/pdelorme/polaris.jpg The erroneous justification of equatorial orientation or axial tilt to the Sun as a component of the Equation of Time is taken by observers who propose the analemma. http://www.wengersundial.com/Analemma/analemma.jpg As equatorial orientation remains constant as a property of axial rotation,the error emerges from not considering that the Earth's changing orbital orientation hence axial tilt does not cause the daylight/darkness asymmetry but is a property of the Earth's orbital position and that independent motion.Axial tilt in combination with constant axial rotation cannot accelerate or retard the return of the Earth axial longitude coordinates (assuming constant axial rotation) back to the Sun/Earth line (noon) hence there is no justification in incorporating it into the Equation of Time,as the analemmatic figure 8 or bottom line. http://www.longwoodgardens.org/Sundial/Analemma.html Orbital orientation as a consequence of independent orbital motion is not at all difficult to gauge.It does not follow axial longitude coordinates and represents the portion of the Earth orientated to the Sun and the other portion generating an orbital shadow.The behavior of this orientation and the division between daylight and shadow correlates with Kepler's second law - http://www.mhhe.com/physsci/astronom...ages/04f15.jpg The effort to reduce all effects on the calculation of the equable 24 hour day to axial rotational coordinates comes at the expense of ignoring the influences of orbital orientation notwitstanding that everyone seems to bypass the Sun and the orbital motion of the Earth altogether to achieve synchonicity with the axial rotational/stellar circumpolar equivalency. |
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