Yes, ladies and gents, for those playing at home we are now having to defend the Equation of Time against Oriel's denials of its existence.

Iain wrote;"Yes, ladies and gents, for those playing at home we are now having to defend the Equation of Time against Oriel's denials of its existence."

You discovered what Newton was refering to when he defined and distinguished absolute time and relative time as the Equation of Time ,did'nt you.

Now what are you going to do,stick with your 23 hours 56 min with the Equation of Time hanging over your head.Do yourself a favor and build a roaring fire with your relativity books.

Yes, Oriel, I do understand.

Absolute time: The average length of a solar day can be divided into 24 hours exactly, no more no less.

Relative time: The messy quantity you get when you try to measure the time directly from the sun, because the Earth's orbit is slightly elliptical.

No mention of anything exterior to the solar system there. Its a great system for comparing the correct time shown on a clock to the position of the sun in the sky in order to calculate your position on the globe, and also know where the other planets in our solar system are located.

I have depressingly small doubt you'll inform me I've gone wrong somwhere. And even more depressingly small doubt you won't bother to identify exactly where.

Again, I really don't understand why you keep claiming that this has a single thing to do with relativity. Newton gave us a theory of it, and also the EoT, but one has nothing to do with the other.

](*,)

I'm out of here. [-(

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Okay, Oriel, let's do this step by step. You have said that the Equation of Time compensates for the inequal natural day to an equable 24-hour day. I have taken this to mean that if you take any two consecutive noons (solar transits) and measure the time between them, it will probably not be exactly 24 hours. Some will be less, some more. Over the course of an entire year, the average is 24 hours.

So, with our clocks measuring exactly 24 hours between one noon and the next, the solar transit will not occur when the clocks say noon. The Equation of Time tells us, for any given day, how far ahead of (or behind) the clock's noon the solar transit actually occurs. Is this correct?

Again, let's keep this simple. No talk about Einstein, or relativity, or the "fixed stars," or anything else. Is what I have described here in this post correct?

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SeanF

"Ask to understand, but don't challenge unless you have the knowledge."--NEOWatcher

The contents of this post are ©2008 by SeanF and may not be copied or retransmitted in any form without the express written consent of SeanF

SeanF wrote;"So, with our clocks measuring exactly 24 hours between one noon and the next, the solar transit will not occur when the clocks say noon. The Equation of Time tells us, for any given day, how far ahead of (or behind) the clock's noon the solar transit actually occurs. Is this correct?"

The Equation of Time allows rotation of the Earth in 24 hours to remain constant against the variation in a natural day.Note noon at your longitude location (this is good from North to South pole) apply the Equation for that day and start your stopwatch ticking.After 24 hours exactly reapply the Equation value for that day and you come up with the natural noon alignment.Of course in reapplying the Equation,you turn the negative values in positive values and visa versa if you work off a constant 24 hours by your stopwatch to come up with the natural longitudinal noon alignment each and every time.



Sean F wrote;"Again, let's keep this simple. No talk about Einstein, or relativity, or the "fixed stars," or anything else. Is what I have described here in this post correct?"

The thing is simple,a child can understand them,if you can't even get the rotation rate of the Earth in 24 hours via clocks and the EoT right,why bother trying to tamper with definitions which reflect the difference between an unequal natural day and a 24 hour clock day.It does'nt take a genius to work out that the EoT isolates the axial rotation of the Earth from its annual orbital yet Albert could'nt work out that this is exactly what Newton was defining and distinguishing between absolute time and relative time.


To be fair,Newton asks too much of his readers in sorting out why if you use a 24 hour clock to determine the pace of things,there is no natural external celestial motion corresponding to 24 hours yet Foucault's pendulum helps in isolating the motion of the Earth to the longitude/clock system that clever men worked out,15 degrees per hour and 360 degrees per 24 hours.

You can read Newton's phrasing of the difference between the natural unequal day and the 24 hour clock day with the EoT as a bridge between the two without having to harp on the word 'absolute'.I don't particularily like what Newton attempted to do to suit his own agenda but fundamentally there is nothing remotely wrong astronomically with his definitions.

"Absolute time, in astronomy, is distinguished from relative, by the equation or correlation of the vulgar time. For the natural days are truly unequal, though they are commonly considered as equal and used for a measure of time; astronomers correct this inequality for their more accurate deducing of the celestial motions. It may be, that there is no such thing as an equable motion, whereby time may be accurately measured. All motions may be accelerated and retarded, but the true, or equable, progress of absolute time is liable to no change. The duration or perseverance of the existence of things remains the same, whether the motions are swift or slow, or none at all: and therefore, it ought to be distinguished from what are only sensible measures thereof; and out of which we collect it, by means of the astronomical equation. The necessity of which equation, for determining the times of a phænomenon, is evinced as well from the experiments of the pendulum clock, as by eclipses of the satellites of Jupiter." Principia

I'll jump in again, but not with much hope of success...
This is incorrect! This is not what the Equation of Time does. The Equation of Time transforms between an elliptic Keplerian orbit of the Earth, inclined relative to the rotational axis, and a perfect circular orbit, in a plane perpendicular to the Earth's rotational axis. The time-scale constructed is still the result of the combined rotational and orbital motion of the Earth.

Do you realise that Newton and Einstein are talking about effects which differ enormously in magnitude?
- The difference between a "vulgar day" and a "clock day" is a few seconds every day. Accumulated throughout the year, they give the double-wave form, with a max deviation of 16 minutes in mid-november.
- The difference between a sidereal day and a "clock day" is approx 4 minutes every day. Accumulated effects are one entire day per year
- Einstein's corrections relate to the precession of Mercury, which is 43 arcseconds per century.

The laws of Kepler, Newton and so forth can only be applied in a sidereal frame, where the position of the observer - where he is on the surface, as well as the Earth's position in its orbit - has been removed from consideration. Planets do not move in ellipses as seen from the Earth, they move in ellipses as seen from a point that is not orbiting the sun, but is fixed relative to the stars!

Also, the effects Newton was studying are far larger than those Einstein set out to explain. It would not have been possible for Einstein to work at all unless those larger modifications had already been applied!

But this is actually a pointless debate. When Einstein says "relative time", he's talking about what Newton called "absolute time". Different terminology, same concept.

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Iain wrote;"Again, I really don't understand why you keep claiming that this has a single thing to do with relativity. Newton gave us a theory of it, and also the EoT, but one has nothing to do with the other."

You either get this or you don't,an astronomical day is 24 hours and the last thing you do is this -

"The visible fixed stars are bodies for which the law of inertia certainly holds to a high degree of approximation. Now if we use a system of co-ordinates which is rigidly attached to the earth, then, relative to this system, every fixed star describes a circle of immense radius in the course of an astronomical day, a result which is opposed to the statement of the law of inertia."

http://www.bartleby.com/173/4.html

Do you wish to inform your colleagues just how badly wrong that astronomically is or perhaps you may not see it yourself.

I'm with Kaptain K. If you won't listen, there is no point in discussing. Good bye and good riddance.

Iain wrote;"I'm with Kaptain K. If you won't listen, there is no point in discussing. Good bye and good riddance."

Funny,funny,funny !,Albert tied the circumpolar motion of the 'fixed stars' to the astronomical 24 hour day,you gotta love it.

I would'nt want to look that bad but there you have it,a whole bunch of guys basing the rotation of the Earth on 23 hours 56 min.I mean relativists are begging to be laughed at

http://zapatopi.net/geriatric.html

I guess you want to continue infecting youngsters with your rubbish and that I object to,they could keep the damn concept for sci-fi but that it all is proposed as fact reflects badly on those of us who are parents,relativity is a cult no better or worse than creationism,continue for a while you will but last you won't.

Sorry, did anyone hear a point being made?

Thought not.

Considering that the website to which you link is obviously meant to be a joke, I think that he/she wants people to laugh.

However, the physics in that link is wrong. Clocks on the equator do not run slower than clocks at the poles. The time dilation effect due to the speed is not the only effect. The change in the gravitational redshift due to the oblateness of the earth cancels it. Clocks on the geoid all run at the same rate. On need only correct for altitude - so you're better off living in Denver. And, oriel36, this is a real effect - primary frequency standards have to account for their height above the geoid in order for them to run at the proper frequency, at about a part in 10^16 per meter.

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I don't understand your first sentence here. You say "The Equation of Time allows rotation of the Earth in 24 hours..." The EoT is just that, an equation. It can't affect the Earth's rotation - the Earth was spinning on its axis long before life developed, and certainly long before humanity devloped the EoT.

So, let me try this again. If I take an accurate clock, set it to 12:00noon at the exact time of the solar transit on January 1, and then simply note the time my clock is showing on each successive solar transit, I will find that sometimes the transit occurs prior to 12:00 and sometimes the transit occurs after 12:00. Right?

(I snipped all the other stuff about Einstein(!), Newton, the Principia, and Foucault's Pendulum because you're getting ahead of me. I'm not ready to get into that yet. )

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SeanF

"Ask to understand, but don't challenge unless you have the knowledge."--NEOWatcher

The contents of this post are ©2008 by SeanF and may not be copied or retransmitted in any form without the express written consent of SeanF

Swansont wrote;"However, the physics in that link is wrong. Clocks on the equator do not run slower than clocks at the poles. The time dilation effect due to the speed is not the only effect. The change in the gravitational redshift due to the oblateness of the earth cancels it. Clocks on the geoid all run at the same rate. On need only correct for altitude - so you're better off living in Denver. And, oriel36, this is a real effect - primary frequency standards have to account for their height above the geoid in order for them to run at the proper frequency, at about a part in 10^16 per meter."

For the benefit of Iain I will condense the passage further,an astronomer should get sick looking at it but I suggest you may as well laugh at it .


" Now if we use a system of co-ordinates which is rigidly attached to the earth, then, relative to this system, every fixed star describes a circle of immense radius in the course of an astronomical day,"

http://www.bartleby.com/173/4.html


I have to ask,if the BA is prepared to go along with that I assume that he does not have the best interests of children in mind,either that or simply does not have the capacity to make those necessary judgements.It is not a matter of understanding or not understanding relativity but to tie the observed stellar circumpolar to the axial rotation of the Earth in terms of the astronomical day is hideous or hilarious.

Your relativistic concept is not a human achievement,it is an intellectual holocaust.

So: In the kind of coordinate system you're so opposed to, where the stars are rotating, the laws of Newton and Kepler cannot be applied. And this is why nether of these gentlemen, nor Einstein, uses that kind of coordinate system.

He's explaining what a Galileian system of coordinates is by showing the counter-example. He's not using the counter-example, just showing it to us briefly.

__________________
"We do not require reality to conform to the expectations of the ignorant"

SeanF wrote;"I don't understand your first sentence here. You say "The Equation of Time allows rotation of the Earth in 24 hours..." The EoT is just that, an equation. It can't affect the Earth's rotation - the Earth was spinning on its axis long before life developed, and certainly long before humanity devloped the EoT."

The Equation of Time permits you to isolate the axial rotation of the Earth to 24 hours,It is not so much a formula as it is an addition and subtraction of minutes and seconds for appropriate days to remove the natural inequality due to the distance the Earth covers in its elliptical orbit as it axially rotates to face the Sun directly and then repeats it.

Sean F,there is nothing stopping you from doing this yourself,any book or website on longitude,clocks and the EoT explain this far better than I could.With a clearer view of why clocks are based on the rotation of the Earth in 24 hours,you will find nothing wrong with how Newton compares the 24 clock day with the unequal natural day in terms of the difference between absolute time and relative time.

You will find people like Einstein and Mach wrong when they try to make sense of things that you will come to understand quite easily and especially Newton's difference between absolute time/24 hour clock and relative time/unequal natural day.

"Absolute time, in astronomy, is distinguished from relative, by the equation or correlation of the vulgar time. For the natural days are truly unequal, though they are commonly considered as equal and used for a measure of time; astronomers correct this inequality for their more accurate deducing of the celestial motions." Principia

The only reason that the EoT is useful today is that it only refers to the rotations of the Earth,both axial and orbital,wrt to the Sun and leaves the stars out of the picture.Perhaps if you ever ask how we know the local stars are rotating around the galactic axis,the simple answer is that like being on a carousel the local stars change their position over time to the remaining galaxies,even if we can't see it ,it happens in principle.It becomes complicated after that by using supernova data as markers for distant parent galaxies but at least in recognising the rotation of the Milky Way stars at least that is a start.

Without understanding the most fundamental rotation of all,the Earth's rotation on its axis and why clocks register it as 24 hours exactly you cannot go to the next rotation,which is its annual elliptical orbit around the Sun,nor the next one,its rotation around the galactic axis and then there is an even greater one but that is for another day.

"Now if we use a system of co-ordinates which is rigidly attached to the earth, then, relative to this system, every fixed star describes a circle of immense radius in the course of an astronomical day, a result which is opposed to the statement of the law of inertia."

It is no longer up to me,the BA either tells you what stellar circumpolar motion actually is,that the astronomical day is 24 hours exactly or he does not.

That guy thought the motion of the 'fixed stars' had an influence of planetary motion but at this stage it does'nt really matter,he mixes the value of 23 hours 56 min with a system based on 24 hours which is just about right for Albert.When he wrote those passages in 1920 the scale of the cosmos in terms of galaxies had yet to be discovered and he is on about the 'fixed stars' in keeping with what was known in his era,the poor bugger must have been upset when galaxies showed up.

http://www.bartleby.com/173/30.html

Go ahead,talk about warped space,multiple universes and fixed star universes but it certainly won't be astronomy.

I have done enough here.

I bolded that particular phrase because I want to refer to it. If the Earth were not orbiting the sun but merely rotating in place, the day would be consistent - the Earth would rotate exactly 360 degrees between one solar transit and the next. Because the Earth moves in its orbit, though, a complete 360-degree rotation does not bring the next solar transit into place. The Earth has to rotate a little bit farther to get to the next solar transit.

But - and I think this is a key point - the Earth's direction of rotation (around its axis) is the same as its direction of revolution (around the Sun). That means that no matter where the Earth is in its orbit, no matter whether it's winter, spring, summer, or autumn, the Earth always has to rotate farther than 360 degrees to get from one solar transit to the next. Because of the eccentricity of Earth's orbit, sometimes it's just a little bit more and sometimes it's quite a bit more, but it's always more, never less, isn't it?

But doesn't that mean that the average 24-hour solar day is more than 360 degrees of rotation?

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"Ask to understand, but don't challenge unless you have the knowledge."--NEOWatcher

The contents of this post are ©2008 by SeanF and may not be copied or retransmitted in any form without the express written consent of SeanF