Kelper & Tycho - how did they come to their conclusions?

fret_wimp2

Most people with an interest in astronomy are familiar with Tycho Brahe & Johannes Kelpers discoveries regarding orbits of the planets.
A quick google provides lots of info on what they discovered.

What I cant figure out and can find no info on is HOW they made their discoveries. Can anyone elaborate on the details of the experiments and measurements they took, and how they were done.

I just want to know what they did and get a view of how that proves what they discovered.

Zubeneschamali

fret_wimp2 wrote: »

What I cant figure out and can find no info on is HOW they made their discoveries. Can anyone elaborate on the details of the experiments and measurements they took, and how they were done.

Wikipedia can tell you.

Tycho built and used instruments that measured the positions of the stars in the sky very precisely. The lack of measurable parallax for "new stars" and comets showed that they were far away, like the stars, not in the atmosphere. This disproved the idea that the heavens were unchanging.

Tycho's precise measurements of the positions of the planets allowed Kepler to work out his laws.

gkell11

fret_wimp2 wrote: »

Most people with an interest in astronomy are familiar with Tycho Brahe & Johannes Kelpers discoveries regarding orbits of the planets.
A quick google provides lots of info on what they discovered.

What I cant figure out and can find no info on is HOW they made their discoveries. Can anyone elaborate on the details of the experiments and measurements they took, and how they were done.

I just want to know what they did and get a view of how that proves what they discovered.

Again, I am a newbie and can't post the necessary links which help explain what Kepler did and how he did it.

Kepler along with all his contemporaries tracked the motion of the planets and watched as they periodically stopped and went backwards against the background stars before resuming their motion against the background stars.

"Copernicus, by attributing a single annual motion to the earth, entirely rids the planets of these extremely intricate coils ,leading the individual planets into their respective orbits
,quite bare and very nearly circular. In the period of time shown in the diagram, Mars traverses one and the same orbit as many times as the 'garlands' you see looped towards the centre,with one extra, making nine times, while at the same time the
Earth repeats its circle sixteen times " Kepler

There is an image on the main description of Kepler on the Wikipedia page where you can see the constellations symbols and the motion of Mars tracked over a 16 year period.Any APOD description of Mars in retrograde will show the same thing.

Get this far and you are half way there.

fret_wimp2

Thanks guys. To get more specific ( my question was badly phrased), lets say just using the standard tools in my garrage or perhaps purchase a rudamentary instrument that would have been easily constructed back at the time of copernicus or Kelper, how could I, in my back garden prove the same thing they did.

Im interested in the exact method of how they did what they did without very accurate clocks or advanced equipment.

Zubeneschamali

fret_wimp2 wrote: »

lets say just using the standard tools in my garrage or perhaps purchase a rudamentary instrument that would have been easily constructed back at the time of copernicus or Kelper, how could I, in my back garden prove the same thing they did.

You couldn't. Tycho didn't use rudimentary instruments, he used extremely precise instruments, which are not at all easily constructed.

gkell11

fret_wimp2 wrote: »

Thanks guys. To get more specific ( my question was badly phrased), lets say just using the standard tools in my garrage or perhaps purchase a rudamentary instrument that would have been easily constructed back at the time of copernicus or Kelper, how could I, in my back garden prove the same thing they did.

Im interested in the exact method of how they did what they did without very accurate clocks or advanced equipment.

Sure, it takes many years to become accustomed to their exact methods but if you want what is effectively the ' inverse square law' even though it isn't a law nor is it a description of planetary dynamics .

"The proportion existing between the periodic times of any two planets is exactly the sesquiplicate proportion of the mean distances of the orbits, or as generally given,the squares of the periodic times are proportional to the cubes of the mean distances." Kepler

If you have a real interest in what Kepler did and how he did it you would do something I can't which is post the relevant image showing the motion of the Earth and the motion of Mars over a 16 year period because there is nothing in your garage that will help you. If you want a more expanded version of Kepler's statement above then here it is -

"But it is absolutely certain and exact that the ratio which exists between the periodic times of any two planets is precisely the ratio of the 3/2th power of the mean distances, i.e., of the spheres themselves; provided, however, that the arithmetic mean between both
diameters of the elliptic orbit be slightly less than the longer diameter." Kepler

What he and his contemporaries did is gauge the length of time it took a planet to pass through the background field of stars and return to the same position against those stars. It takes the Earth one year to return to the same position, Jupiter 12 years, Saturn roughly 30 years and so on. Now there is a lot of work involved and it is not always as straightforward as this however ,for the purpose here, you are looking at a correlation between the time it takes a planet to make a circuit of the Sun and its distance from the Sun.

"And so if any one take the period, say, of the Earth, which is one year, and the period of Saturn, which is thirty years, and extract the cube roots of this ratio and then square the ensuing ratio by squaring the cube roots, he will have as his numerical products the most just ratio of the distances of the Earth and Saturn from the sun. For the cube root of 1 is 1, and the square of it is 1; and the cube root of 30 is greater than 3, and therefore the square of it is greater than 9. And Saturn, at its mean distance from the sun, is slightly higher than nine times the mean distance of the Earth from the sun." Kepler

You have all this explained by Kepler rather than me but there are now tools which help the contemporary observer streamline these insights into visual narratives where they can be then used properly.

Zubeneschamali

gkell11 wrote: »

What he and his contemporaries did is gauge the length of time it took a planet to pass through the background field of stars and return to the same position against those stars.

Well, no. Anyone can do that in their back yard, using just their bare eyes. Ptolemy knew that stuff around 150 AD.

Tycho measured the distances to the planets using parallax, and disproved Ptolemy's system. You can't measure parallax without precise, accurate instruments.

(Tycho also drew entirely the wrong conclusions from his measurements of stellar parallax, which is why he is always mentioned with Kepler, who used Tycho's data to better effect).

gkell11

Zubeneschamali wrote: »

Well, no. Anyone can do that in their back yard, using just their bare eyes. Ptolemy knew that stuff around 150 AD.

Tycho measured the distances to the planets using parallax, and disproved Ptolemy's system. You can't measure parallax without precise, accurate instruments.

(Tycho also drew entirely the wrong conclusions from his measurements of stellar parallax, which is why he is always mentioned with Kepler, who used Tycho's data to better effect).

Make yourself useful and post this APOD image for me - ' Jupiter and Saturn Pas De Deux' .

djpbarry

fret_wimp2 wrote: »

Thanks guys. To get more specific ( my question was badly phrased), lets say just using the standard tools in my garrage or perhaps purchase a rudamentary instrument that would have been easily constructed back at the time of copernicus or Kelper, how could I, in my back garden prove the same thing they did.

Im interested in the exact method of how they did what they did without very accurate clocks or advanced equipment.

You think you can whack something together in your shed and replicate the work of Tycho Brahe?

It never ceases to depress me when people are so incredibly dismissive of brilliant science.

gkell11

djpbarry wrote: »

You think you can whack something together in your shed and replicate the work of Tycho Brahe?

It never ceases to depress me when people are so incredibly dismissive of brilliant science.

He asked a basic and valid question and is likely to be bombarded with bluff and voodoo when he can easily read what Kepler wrote and ,with the aid of graphics and images, can see how the original astronomers worked out the Earth is sandwiched between the inner and outer planets in our common orbit around the Sun.

I am hampered by not being able to demonstrate the original astronomical arguments which set the Earth and other planets in motion around the Sun using imaging along with the words of the great astronomers but it is all very simple to the eyes and the mind.

Zubeneschamali

gkell11 wrote: »

He asked a basic and valid question and is likely to be bombarded with bluff and voodoo when he can easily read what Kepler wrote and ,with the aid of graphics and images, can see how the original astronomers worked out the Earth is sandwiched between the inner and outer planets in our common orbit around the Sun.

Tycho made all of those brilliant observations, measured the distances to the Sun and planets and proved Ptolemy wrong, but he still concluded that the Earth was stationary at the centre of the universe, and that the sun went around it.

gkell11

Zubeneschamali wrote: »

Tycho made all of those brilliant observations, measured the distances to the Sun and planets and proved Ptolemy wrong, but he still concluded that the Earth was stationary at the centre of the universe, and that the sun went around it.

The original question in the title of this thread is how did Kepler arrive at his conclusions and there are multiple considerations to take into account but most can be easily identified with imaging,graphics and so on.

One of the main arguments relied on the time it took a celestial object to return to the same area against the background stars or the 'periodic times' argument -

" The 10th argument,taken from the periodic times, is as follows; the apparent movement of the Sun has 365 days which is the mean measure between Venus' period of 225 days and Mars' period of 687 days.Therefore does not the nature of things shout out loud that the
circuits in which those 365 days are taken up has a mean position between the circuits of Mars and Venus around the Sun and thus this is not the circuit of the Sun around the Earth -for none of the primary planets has its orbit arranged around the Earth,as Brahe admits,but the circuit of the Earth around the resting Sun,just as the other planets,namely Mars and Venus,complete their own periods by running around the Sun." Kepler.

Now, I am hamstrung with the inability to present imaging to demonstrate the methods used to provide greater detail to these points however there is a huge modification made possible by contemporary imaging which allows observers to appreciate the difference between inner and outer planetary retrogrades.

fret_wimp2

djpbarry wrote: »

You think you can whack something together in your shed and replicate the work of Tycho Brahe?

It never ceases to depress me when people are so incredibly dismissive of brilliant science.

Hang on a second.
1. I dont think i can replicate anything, hence why i asked the question.
2. Not once has the brilliance of any of these giants of science been questioned.

My question stems from the fact that although these men were brilliant, they didnt have satellites, computers, a wealth of knowledge in a library, very accurate clocks, the internet or even electricity. Yet they still managed to come to amazing conclusions.

To try and explain my question a bit better, we know their conclusions are true, but if all the books, internet and electricity disappeared tomorrow how would you prove it all again, with the limited means available?


It never ceases to depress me how condescending some people can be when they expect everyone to be at their level of knowledge, and put down those who ask questions to try to learn.

ps200306

fret_wimp2 wrote: »

Hang on a second.
1. I dont think i can replicate anything, hence why i asked the question.
2. Not once has the brilliance of any of these giants of science been questioned.

My question stems from the fact that although these men were brilliant, they didnt have satellites, computers, a wealth of knowledge in a library, very accurate clocks, the internet or even electricity. Yet they still managed to come to amazing conclusions.

To try and explain my question a bit better, we know their conclusions are true, but if all the books, internet and electricity disappeared tomorrow how would you prove it all again, with the limited means available?


It never ceases to depress me how condescending some people can be when they expect everyone to be at their level of knowledge, and put down those who ask questions to try to learn.

There's a reason these guys are famous. The observations and their interpretation were extremely far from easy or obvious. The poster who wants to show you the pictures that makes it all obvious to the modern mind is, perhaps, missing the point of your question: the answer is "it was damn hard". They were also hamstrung by earlier scientific, mathematical, religious and occult prejudices. The Tychonic system attempts to combine Ptolemy and Copernicus, but gets it wrong. Kepler was obsessed at one stage about a possible relationship between the planetary periods and the Platonic solids, based on the assumption that God created the universe according to a mathematical plan. He also fumbled for the right mathematical tools to perform his analysis and along the way contributed to the development of calculus.

You say "we know their conclusions were true", but remember the typical potted history of science winnows out all the missteps, the blind alleys, the bowing to conventional wisdom ... and leaves what looks like an unerring trajectory toward the modern viewpoint. Some of their conclusions were true, and the rest are generally glossed over. In the end, I think, the reason they are remembered is that Tycho was obsessive about the quality and accuracy of his measurements, and Kepler was honest in their interpretation, going where the data led, as well as having profound insights about their relationships.

Depending on how deep you want to delve, you will find a great deal of information online about the two men, their contemporaries, their influences, and the state of contemporary science and maths. If you want to start with Tycho and his amazing instruments, which were the most advanced of the pre-telescopic era, you could start with the evolution of the mural quadrant during the time of the medieval Arabic astronomers, and from even earlier marine navigational aids. I found some great online material (not Wikipedia) previously, will see if I can dig it out.

You will see that improvement in observational accuracy was a painstaking, incremental process. Mostly it was used to provide updates to Ptolemy's Almagest which was still the basic seminal work for 1300 years. (And even it built on the lost work of Hipparchus, 300 years earlier). These efforts could still not be reproduced by "the man in the street" without specialist education.

gkell11

ps200306 wrote: »

There's a reason these guys are famous. The observations and their interpretation were extremely far from easy or obvious. The poster who wants to show you the pictures that makes it all obvious to the modern mind is, perhaps, missing the point of your question: the answer is "it was damn hard".

The question was how did they come to their conclusions rather than whether it was hard or not. My point is that there is nothing difficult about these things nowadays as long term observations can be condensed into easily understandable form where the planets move around the Sun and against the backdrop of the field of stars.

I sat in the waiting room of my gp and picked up a brochure about quitting smoking and the description was focused on how hard it is to stop and all the nicotine replacements that are available to curb the pangs however I did read a book a dozen years ago by Allan Carr which said the absolute opposite in that it is easy to stop smoking and I found it to be the case. The parallel point is that observers today approach astronomy with a fear that there is something difficult about the endeavor when nothing could be further from the truth and especially now when visual narratives translate long term imaging into context of the Earth's motion,the structure of the solar system, cause and effect between dynamics and terrestrial sciences and so on.

Kepler and Brahe worked off a particular perspective that becomes troublesome when dealing with observations seen from Earth separating the inner and outer planets but this involves actually looking at the motions as they appear to us and dealing with them. I would ask the moderator to remove the newbie block on links needed to present the arguments but respect that it may not be possible.

gkell11

"There's a reason these guys are famous. The observations and their interpretation were extremely far from easy or obvious. The poster who wants to show you the pictures that makes it all obvious to the modern mind is, perhaps, missing the point of your question: the answer is "it was damn hard". " ps200306

The question was how did they come to their conclusions rather than whether it was hard or not. My point is that there is nothing difficult about these things nowadays as long term observations can be condensed into easily understandable form where the planets move around the Sun and against the backdrop of the field of stars.

I sat in the waiting room of my gp and picked up a brochure about quitting smoking and the description was focused on how hard it is to stop and all the nicotine replacements that are available to curb the pangs however I did read a book a dozen years ago by Allan Carr which said the absolute opposite in that it is easy to stop smoking and I found it to be the case. The parallel point is that observers today approach astronomy with a fear that there is something difficult about the endeavor when nothing could be further from the truth and especially now when visual narratives translate long term imaging into context of the Earth's motion,the structure of the solar system, cause and effect between dynamics and terrestrial sciences and so on.

Kepler and Brahe worked off a particular perspective that becomes troublesome when dealing with observations seen from Earth separating the inner and outer planets but this involves actually looking at the motions as they appear to us and dealing with them. I would ask the moderator to remove the newbie block on links needed to present the arguments but respect that it may not be possible.

ps200306

gkell11 wrote: »

The question was how did they come to their conclusions rather than whether it was hard or not. My point is that there is nothing difficult about these things nowadays as long term observations can be condensed into easily understandable form where the planets move around the Sun and against the backdrop of the field of stars.

The question was how they worked it all out without benefit of modern equipment or hindsight.

gkell11

ps200306 wrote: »

The question was how they worked it all out without benefit of modern equipment or hindsight.

Be my guest, you have the Panis Quadragesimalis of Kepler in front of your on Wikipedia page showing the extent of retrogrades as the Earth overtakes Mars and the variations with each orbital pass but that won't help you with Venus and Mercury as the inputs are different.

Care to present the image where I cannot as a newbie along with an APOD image of Mars in retrograde to give it a contemporary treatment ?.

Zubeneschamali

gkell11 wrote: »

Kepler and Brahe worked off a particular perspective that becomes troublesome when dealing with observations seen from Earth separating the inner and outer planets but this involves actually looking at the motions as they appear to us and dealing with them.

Tycho disproved Ptolemy using parallax - and you cannot see that at all without extremely precise instruments.

Kepler used the same data to deduce that orbits are elliptical, rather than circular, and that the speed of a planet in it's orbit depends on its distance from the sun. Nothing you are going to observe yourself in your back yard will prove that, either.

Retrograde motion is nothing to do with parallax or elliptical orbits - Ptolemy's tables described retrograde motion 1000 years before Tycho.

gkell11

Zubeneschamali wrote: »

gkell11 wrote: »

Tycho disproved Ptolemy using parallax - and you cannot see that at all without extremely precise instruments.

Kepler used the same data to deduce that orbits are elliptical, rather than circular, and that the speed of a planet in it's orbit depends on its distance from the sun. Nothing you are going to observe yourself in your back yard will prove that, either.

Retrograde motion is nothing to do with parallax or elliptical orbits - Ptolemy's tables described retrograde motion 1000 years before Tycho.

The general run of these things is that participants create a firewall of voodoo and moderation rather than inspect the details of what was observed and how these observations were translated into context. I did call for the relevant images so that if people do genuinely wish to know how Kepler, Galileo and Copernicus looked at these topics using observations they would supply the observations for everyone to inspect ,add comments from the original innovators or create new perspectives. I haven't seen anyone lift a finger in that respect confirming an observation (rather than a complaint) that Galileo made to Kepler even though it is a little bit self-congratulatory -

"My dear Kepler, I wish that we might laugh at the remarkable stupidity of the common herd. What do you have to say about the principal philosophers of this academy who are filled with the stubbornness of an asp and do not want to look at either the planets, the moon or the telescope, even though I have freely and deliberately offered them the opportunity a thousand times? Truly, just as the asp stops its ears, so do these philosophers shut their eyes to the light of truth" Galileo

In short, astronomy at this level is still a visual pursuit so that were observers interested in what Copernicus,Galileo or the other astronomers achieved they would,of necessity, walk the same path as they did. There is an unresolved issue concerning retrogrades which can only now be explained using modern tools and involving the partitioning between inner and outer planetary retrogrades resolutions but this is a huge undertaking even for those committed to such an endeavor.

It is not an issue about putting anyone on the spot or how well they can use stock phrases that are meaningless but rather on the rare occasion when somebody does ask about the methods used by the original heliocentric astronomers it is an opportunity for engagement.

djpbarry

fret_wimp2 wrote: »

It never ceases to depress me how condescending some people can be when they expect everyone to be at their level of knowledge, and put down those who ask questions to try to learn.

I didn’t mean to be condescending, but have another look at your post. You asked how you could replicate the work of Kepler using “standard tools” in your garage or “rudimentary instruments that would have been easily constructed at the time of Copernicus and Kepler”. You wanted to know how to reproduce their work without “very accurate clocks or advanced equipment”. The simple answer is that you can’t. You could certainly try, but without extremely accurate instruments capable of precise measurements, you are very unlikely to succeed.

gkell11

djpbarry wrote: »

I didn’t mean to be condescending, but have another look at your post. You asked how you could replicate the work of Kepler using “standard tools” in your garage or “rudimentary instruments that would have been easily constructed at the time of Copernicus and Kepler”. You wanted to know how to reproduce their work without “very accurate clocks or advanced equipment”. The simple answer is that you can’t. You could certainly try, but without extremely accurate instruments capable of precise measurements, you are very unlikely to succeed.

The original poster asked how they came to their insights -

"What I cant figure out and can find no info on is HOW they made their discoveries. Can anyone elaborate on the details of the experiments and measurements they took, and how they were done.

I just want to know what they did and get a view of how that proves what they discovered."

There is a step by step process which was not available online,at least until now, so although he may assume that there is some garage experiment that explains the insight of Kepler the fact is that he is looking in the wrong place.

A simple watch can be used to prove Kepler's variations in orbital speed from day-to-day observations however such a proof takes a lot of groundwork by following the path of those astronomers up to a certain point. That is the exciting bit however it does require an effort on the part of the inquirer to supply visual perspectives that I can't presently.

Zubeneschamali

gkell11 wrote: »

A simple watch can be used to prove Kepler's variations in orbital speed from day-to-day observations

Please, do explain how.

gkell11

Zubeneschamali wrote: »

Please, do explain how.

The original poster of this thread has to work for it by following a particular set of observations that can be reproduced using images and links along with the original descriptions of the astronomers themselves. I cannot do this presently due to a newbie status nor would I do it anyway,after all, it is a journey rather than a chore.

gkell11

djpbarry wrote: »

I didn’t mean to be condescending, but have another look at your post. You asked how you could replicate the work of Kepler using “standard tools” in your garage or “rudimentary instruments that would have been easily constructed at the time of Copernicus and Kepler”. You wanted to know how to reproduce their work without “very accurate clocks or advanced equipment”. The simple answer is that you can’t. You could certainly try, but without extremely accurate instruments capable of precise measurements, you are very unlikely to succeed.

That is incorrect, with two strings, a stopwatch and a normal watch he can demonstrate Kepler's insight that a planet varies its speed as it moves through space. Of course Kepler had none of these things and he made an incorrect assertion regarding the important observation which affirms his own work.

Zubeneschamali

gkell11 wrote: »

That is incorrect, with two strings, a stopwatch and a normal watch he can demonstrate Kepler's insight that a planet varies its speed as it moves through space.

He is not asking how to demonstrate it, he is asking how Tycho and Kepler made their measurements and deductions. Demonstrating it after you already know the answer is a whole different ballgame.

Kepler's insight that the orbit of Mars is an ellipse was based on years and years of observations: to measure the position of a point on Mars orbit (relative to the Earth) requires a pair of observations one Mars year apart: 687 days. That's the minimum time you'd need to observe Mars to reproduce Kepler's result. Of course, you can't observe Mars every night -sometimes it is too near the Sun and only up during the day. Sometimes the weather is bad.

So in practice, you need observations over a much longer period to give you pairs of measurements 687 days apart.

Of course, given the positions, you can do Kepler's geometry yourself. But Kepler also had to deal with the errors in Tycho's measurements (which were the best ever up to that date, but still only good to 2 or 3 arc-minutes), and the fact that Tycho wasn't trying to measure things exactly one Mars year apart for all those years.

gkell11

Zubeneschamali wrote: »

He is not asking how to demonstrate it, he is asking how Tycho and Kepler made their measurements and deductions. Demonstrating it after you already know the answer is a whole different ballgame.

The title of the thread is -

"how did they come to their conclusions?"

Post the original graphic showing the motion of the Earth and the motion of Mars over a 16 year period, this image is found on the Wikipedia page within the topic of 'Johannes Kepler'.

"Copernicus, by attributing a single annual motion to the earth, entirely rids the planets of these extremely intricate coils ,leading the individual planets into their respective orbits
,quite bare and very nearly circular. In the period of time shown in the diagram, Mars traverses one and the same orbit as many times as the 'garlands' you see looped towards the centre, with one extra, making nine times, while at the same time the Earth
repeats its circle sixteen times " Astronomia Nova 1609

This accounts for the motion of the outer planets but does not account for inner planetary retrogrades so Kepler fills in the gap using the periodic times argument which inserts the Earth between Mars and Venus as a means to complete solar system structure from Mercury to Saturn (at leas tin his time).

If the original inquirer wishes to affirm Kepler's insight that a planet's speed varies by a garden experiment he can now do so easily by bypassing the complicated references used by Kepler and his contemporaries as accurate watches allow for a new approach. Of course the person who asked the question has to follow the path of those astronomers up to a point but there is no real difficulty in this day and age with visual tools making it a cinch.

Zubeneschamali

gkell11 wrote: »

This accounts for the motion of the outer planets but does not account for inner planetary retrogrades so Kepler fills in the gap using the periodic times argument which inserts the Earth between Mars and Venus as a means to complete solar system structure from Mercury to Saturn (at leas tin his time).

Telling the OP how Kepler discovered things which Copernicus published before Kepler was even born is perhaps not entirely constructive.

gkell11

Zubeneschamali wrote: »

Telling the OP how Kepler discovered things which Copernicus published before Kepler was even born is perhaps not entirely constructive.

When it comes to inner planetary retrogrades then you run into trouble as the periodic times argument which sets the planets in motion against the background stars along with using the Sun's annual motion through the Zodiac fails.

" The 10th argument,taken from the periodic times, is as follows; the apparent movement of the Sun has 365 days which is the mean measure between Venus' period of 225 days and Mars' period of 687 days.Therefore does not the nature of things shout out loud that the
circuits in which those 365 days are taken up has a mean position between the circuits of Mars and Venus around the Sun and thus this is not the circuit of the Sun around the Earth -for none of the primary planets has its orbit arranged around the Earth,as Brahe admits,but the circuit of the Earth around the resting Sun,just as the other planets,namely Mars and Venus,complete their own periods by running around the Sun." Kepler

These threads are so rare that I am sadly prepared to let it drift due to lack of interest however there are so many enjoyable avenues to explore with one path richer than the next were observers willing to look at how those astronomers really looked at the motions of the planets as it appeared to them and their conclusions. There is a modern shortcut which affirms Kepler's variable planetary speed insight using a watch, a stopwatch and a few minutes each day for a week but that too must go to another audience.

Zubeneschamali

gkell11 wrote: »

When it comes to inner planetary retrogrades then you run into trouble as the periodic times argument which sets the planets in motion against the background stars along with using the Sun's annual motion through the Zodiac fails.

This is complete gibberish. Copernicus understood perfectly well about inner and outer planets:

gkell11

Zubeneschamali wrote: »

This is complete gibberish. Copernicus understood perfectly well about inner and outer planets:

The planets move against the background stars so you had better show variations in the motion of Mars with each pass of the Earth as it overtakes that planet and the basis for Kepler's insight that planetary motion is not constant for otherwise retrogrades for each individual planet would not vary.

The original inquirer can post multiple APOD images of Mars in retrograde and then we can talk. Of course inner planetary retrogrades are different and not even Galileo got this right -

"Now what is said here of Jupiter is to be understood of Saturn and Mars also. In Saturn these retrogressions are somewhat more frequent than in Jupiter, because its motion is slower than Jupiter's, so that the Earth overtakes it in a shorter time. In Mars they are rarer, its motion being faster than that of Jupiter, so that the Earth spends more time in catching up with it. Next, as to Venus and Mercury, whose circles are included within that of the Earth, stoppings and retrograde motions appear in them also, due not to any motion that really exists in them, but to the annual motion of the Earth. This is acutely demonstrated by Copernicus . ." Galileo

Zubeneschamali

gkell11 wrote: »

There is a modern shortcut which affirms Kepler's variable planetary speed insight using a watch, a stopwatch and a few minutes each day for a week but that too must go to another audience.

I would be interested to learn what you are talking about here.

gkell11

Zubeneschamali wrote: »

I would be interested to learn what you are talking about here.

Look, this is for readers who have,at the very least, looked at the founding principle which govern how the planets move against the background stars,the length of time it takes each planet to complete a circuit, the difference in luminosity and speed of each planet and all the other things which occupied the original astronomers.

". . . the ancient hypotheses clearly fail to account for certain important matters. For example, they do not comprehend the causes of the numbers, extents and durations of the retrogradations and of their agreeing so well with the position and mean motion of the sun. Copernicus alone gives an explanation to those things that provoke astonishment among other astronomers, thus destroying the source of astonishment, which lies in the ignorance of the causes." 1596, Mysterium Cosmographicum

There is a problem with an element of that description by Kepler and an incredibly important one at that yet it is a path that contemporary observers have to take but with the aid of imaging,graphics and so on. It has to do with the resolution for inner planetary retrogrades and lacking the ability to demonstrate exactly what the difference is is made even worse by the fact that nobody will lift a finger to make the important partitioning of retrograde resolutions.

Better off to just drop the matter.

Zubeneschamali

The Earth's orbital speed varies by only 4% in 6 months. Showing that it changes in a week with a stopwatch would be a good trick - I would like to see it done.

gkell11

Zubeneschamali wrote: »

The Earth's orbital speed varies by only 4% in 6 months. Showing that it changes in a week with a stopwatch would be a good trick - I would like to see it done.

By definition, if I say that variable orbital speed can be proved within a week then it can be done.So,what do you think of Kepler's assertion about the Equation of Time and the Earth's motion ?. Of course you need the 'Epitome of Copernican astronomy' in front of you and like the original poster said , there is little or nothing online regarding the methods by which Kepler arrived at his conclusions. This part of the proof would have been beyond Kepler as they used a different set of references based on everything moving through the Zodiac and the fact that accurate watches didn't exist.

Contemporary imaging and especially sequential imaging introduces a partitioning of retrograde resolutions between the inner and outer planets which none of the original astronomers would have been able to discern as the Earth's own orbital inputs influence observations in two separate ways. The outer planets (Mars,Jupiter,Saturn) are easy enough as the Earth overtakes the slower moving planets causing them to temporarily fall behind in view but the inner planetary retrogrades are a different story.

I ask for images an nobody lifts a finger insofar as this type of astronomy without imaging is like showing people musical notation without actually playing the music hence the disappointment.

mickmackey1

Okay okay :pac:

Zubeneschamali

gkell11 wrote: »

there is little or nothing online regarding the methods by which Kepler arrived at his conclusions.

I linked to an article giving you step by step instructions for reproducing Kepler's geometrical work showing that Mars orbit is an ellipse just a little while back.

gkell11

mickmackey1 wrote: »

Okay okay :pac:

Ah,at last so we are on the journey proper rather than it being a chore using words.

So what that time lapse footage shows is the Earth overtaking Jupiter and Saturn with the nearer Jupiter taking longer to overtake as it is moving faster along with the principle fact that with each pass of those planets they will be in a different orbital position (as will the Earth) hence the extent of retrogrades will be different and subsequently it gives a hint that planets move faster at certain times than at others. A series of APOD images of Mars will show exactly that.

As promised,there are many different paths to take and looking at the APOD footage it should be second nature by now to discern why the definition of a planet shouldn't have been disturbed from its original meaning in context of their observed motions in space as distinct from the apparent direct motion of the Sun through the same zodiac -

"Moreover, we see the other five planets also retrograde at times, and stationary at either end [of the regression]. And whereas the sun always advances along its own direct path, they wander in various ways, straying sometimes to the south and sometimes to the north; that is why they are called "planets" [wanderers]. " Copernicus

It is important for the simple reason that inner planetary retrogrades require a different set of references although Venus and Mercury also wander against the background stars as the outer planets do however as they move faster than the Earth it requires a shift in perspective. What we need next is a YouTube video entitled 'May's Planet Dance' to make this important distinction which in turns works in with proof of Kepler's insight on variable speed.

Zubeneschamali

This is like pulling teeth! Here:

gkell11

Zubeneschamali wrote: »

I linked to an article giving you step by step instructions for reproducing Kepler's geometrical work showing that Mars orbit is an ellipse just a little while back.

I give you Kepler's own words with a description of how he looked at Mars from a moving Earth so make yourself useful and reproduce the plotting of Mars against the background stars over a 16 year period -

"Copernicus, by attributing a single annual motion to the earth,entirely rids the planets of these extremely intricate coils,leading the individual planets into their respective orbits,quite bare and very nearly circular. In the period of time shown in the diagram, Mars traverses one and the same orbit as many times as the 'garlands' you see looped towards the center,with one extra, making nine times, while at the same time the Earth repeats its circle sixteen times " Kepler

The description you give previously is contrived rubbish which can't be matched with Kepler's graphic nor modern representation of retrogrades seen as the Earth overtakes Jupiter and Saturn in that time lapse footage. This is not an excuse for the thread to turn sour as these thread are far too rare to be sabotaged when reasoning becomes intricate. Again,I would rather see the thread die than watch that happen.

Now, what do you think of Kepler's assertion of the Equation of Time and the Earth's motion and if you are not familiar with it I will type it out by hand as there is nowhere online his work is reproduced.

gkell11

Zubeneschamali wrote: »

This is like pulling teeth! Here:

If it is like pulling teeth then you are free to withdraw as the whole point is a way to partition inner and outer planetary retrogrades by adopting two separate perspectives seen from Earth. From there you then move into variations in planetary speeds but not before then. It is a path and a visual one at that.

Now you all have to resolve the retrogrades of Venus and Mercury by assigning the orbital inputs of the Earth into those observations as distinct from outer planetary retrogrades where those planets temporarily fall behind in view against the background stars as the faster Earth overtakes them.

Anyone wish to try ?. This is all new so no need to fear this new perspective as genuine observers will love it.

Zubeneschamali

gkell11 wrote: »

This is all new so no need to fear this new perspective as genuine observers will love it.

This was all old news to Kepler, since Copernicus explained it before he was born, as the picture I pasted in earlier shows.

gkell11

Zubeneschamali wrote: »

This was all old news to Kepler, since Copernicus explained it before he was born, as the picture I pasted in earlier shows.

You are fine, not even the truly brilliant Galileo understood the need to partition the perspectives between inner and outer planetary retrogrades and separate resolution -

"In the Ptolemaic hypotheses there are the diseases, and the Copernican their cure. . . . With Ptolemy it is necessary to assign to the celestial bodies contrary movements, and make everything move from east to west and at the same time from west to east, whereas with Copernicus all celestial revolutions are in one direction, from west to east. And what are we to say of the apparent movement of a planet, so uneven that it not only goes fast at one time and slow at another, but sometimes stops entirely and even goes backward a long way after doing so? To save these appearances, Ptolemy introduces vast epicycles, adapting them one by one to each planet, with certain rules about incongruous motions -- all of which can be done away with by one very simple motion of the Earth." Galileo

The kind poster who posted Jupiter and Saturn as the Earth overtakes it will find nothing about the retrogrades of Venus and Mercury even though they truly exist but require a different treatment. The YouTube video I asked you to post basically makes inner planetary retrogrades self explanatory but a number of major adjustments are needed from outer retrogrades and the way they are explained.

Maybe somebody else will try and succeed. If they do they will post another sequence of images which will help them along , this time I need the sequence of images showing the phases of Venus in an arc representing our grandstand view of the planet as it swings out from behind the Sun to its widest point from our point of view,stops and then swing in front of the Sun. Then they will come to understand the different perspectives between inner and outer retrogrades .

Zubeneschamali

gkell11 wrote: »

You are fine, not even the truly brilliant Galileo understood the need to partition the perspectives between inner and outer planetary retrogrades and separate resolution

Just in case the OP is still reading, this is complete nonsense.

Far from not understanding the motions of the inner planets, Kepler was able to predict the transit of Mercury across the face of the Sun to the day, allowing it to be observed for the first time in history.

In the case of the transit of Mercury in 1631, Kepler had been extremely uncertain of the parameters for Mercury, and advised observers to look for the transit the day before and after the predicted date. Pierre Gassendi observed the transit on the date predicted, a confirmation of Kepler's prediction.[74] This was the first observation of a transit of Mercury

gkell is trying to help us get our heads around the Copernican system, which is nice of him. Apparently, he thinks it is difficult, and that lots of people have problems with it.

But gkell's posts about retrogrades are always qualitative, never any numbers. The whole point of Tycho and Kepler's work is that it is quantitative: they didn't just look at the motions of the planets, they measured them accurately, and then used a bunch of hard sums to learn stuff that you cannot learn by looking at APOD.

gkell11

Zubeneschamali wrote: »

gkell is trying to help us get our heads around the Copernican system, which is nice of him. Apparently, he thinks it is difficult, and that lots of people have problems with it.

I am overwhelmed by the enthusiasm for the new approach to retrogrades and their resolution by using two separate perspectives seen from Earth. The rule is that the faster moving Earth overtaking the outer planets causes them to temporarily fall behind in view before they resume their motion much like being in a car moving on a roundabout sees slower moving cars in outer lanes fall behind in view.

The new approach to inner retrogrades allows us a grandstand view of the motions of Venus and Mercury as they swing out from behind the Sun and then swing back in front of the Sun. I ask for the images of Venus that we see as phases and organized as an arc to bolster the new perspective but obviously few are interested in helping promote this perspective.

Zubeneschamali wrote: »

But gkell's posts about retrogrades are always qualitative, never any numbers. The whole point of Tycho and Kepler's work is that it is quantitative: they didn't just look at the motions of the planets, they measured them accurately, and then used a bunch of hard sums to learn stuff that you cannot learn by looking at APOD.

'Hard sums' you say !, my goodness if you want to prove that the planet's speed varies using a stopwatch and a normal watch over a 7 day period you must follow the path laid out by the resolution of inner planetary retrogrades as the Earth's own orbital motion, in terms of an input into observations, is crucial for appreciating the observation that the Earth's speed varies each day .

It is not an imperative directed at you however readers are directed back to the YouTube video of Venus,Mercury and Jupiter over a period of a month and they can work with the Earth's own orbital motion and how it influences the picture of what we are seeing and how to deal with the motions of Mercury and Venus as they move in the opposite direction to the background stars and then move in the opposite direction, hence retrogrades.

So, images of the 'phases of Venus' anyone ?

gkell11

Zubeneschamali wrote: »

gkell is trying to help us get our heads around the Copernican system, which is nice of him. Apparently, he thinks it is difficult, and that lots of people have problems with it.

I am overwhelmed by the enthusiasm for the new approach to retrogrades and their resolution by using two separate perspectives seen from Earth. The rule is that the faster moving Earth overtaking the outer planets causes them to temporarily fall behind in view before they resume their motion much like being in a car moving on a roundabout sees slower moving cars in outer lanes fall behind in view.

The new approach to inner retrogrades allows us a grandstand view of the motions of Venus and Mercury as they swing out from behind the Sun and then swing back in front of the Sun. I ask for the images of Venus that we see as phases and organized as an arc to bolster the new perspective but obviously few are interested in helping promote this perspective.

Zubeneschamali wrote: »

But gkell's posts about retrogrades are always qualitative, never any numbers. The whole point of Tycho and Kepler's work is that it is quantitative: they didn't just look at the motions of the planets, they measured them accurately, and then used a bunch of hard sums to learn stuff that you cannot learn by looking at APOD.

'Hard sums' you say !, my goodness if you want to prove that the planet's speed varies using a stopwatch and a normal watch over a 7 day period you must follow the path laid out by the resolution of inner planetary retrogrades as the Earth's own orbital motion, in terms of an input into observations, is crucial for appreciating the observation that the Earth's speed varies each day .

It is not an imperative directed at you however readers are directed back to the YouTube video of Venus,Mercury and Jupiter over a period of a month and they can work with the Earth's own orbital motion and how it influences the picture of what we are seeing and how to deal with the motions of Mercury and Venus as they move in the opposite direction to the background stars and then move in the same direction, hence retrogrades.

So, images of the 'phases of Venus' anyone ?

[ Apologies for my poor proofreading but this correction was necessary]

Zubeneschamali

gkell11 wrote: »

The new approach to inner retrogrades allows us a grandstand view of the motions of Venus and Mercury as they swing out from behind the Sun and then swing back in front of the Sun.

It is a newer approach than Ptolemy's, but 1543 is scarcely new in an absolute sense.

gkell11 wrote: »

So, images of the 'phases of Venus' anyone ?

It's a biggie:
https://briankoberlein.com/wp-content/uploads/venus-phase1.jpg

Zubeneschamali

Phases of Venus were first observed by Galileo in 1610, and noted by him as proof of the Copernican system which predicted them, and concrete disproof of the Ptolemaic one.

Just in case gkell tells you this is news.

gkell11

Zubeneschamali wrote: »

It is a newer approach than Ptolemy's, but 1543 is scarcely new in an absolute sense.

Thank you for posting the image so observers can see already there is a difference between inner and outer planetary retrogrades where an outer planet is brightest at the center of retrogrades as they pass the Earth at the closest distance in our mutual orbits around the central Sun whereas at the center of inner planetary retrogrades the planet disappears behind the glare of the central Sun or is at its darkest (transits).

Going back to the YouTube graphic of Mercury and Venus in motion over the course of a month it is now easy enough to see the sweeping arcs as they move around the Sun and are seen to move in the opposite direction to the background stars first and then in the same direction. This is where we depart from the perspectives of the old astronomers for they gauged all motions through the field of stars including the Sun whereas the resolution for inner retrogrades and the grandstand view of planetary motions around the Sun (shown in your image) demands a shift in perspective to account for the Earth's orbital motion and a fixed reference for the motions of Venus and Mercury.

Anyone wish to try their hand at discerning the Earth's orbital input into observations using the YouTube graphic ?. It means a shift away from the apparent motion of the Sun through the Zodiac and focusing on the apparent motions of Elnath, Castor and Pollux in sequence behind the central Sun. It is a line of sight observation using the Earth's orbital motion and another YouTube graphic entitled ' Constellations of the zodiac' helps observers come to understand what causes the stars to move along the orbital plane and behind the Sun in tandem with the actual motions of the inner planets around the Sun.

YouTube - 'Constellations of the zodiac' . It takes a bit of nimble reasoning but ultimately, as someone once said - ' society is always astonished at a new example of common sense'.

Zubeneschamali

gkell11 wrote: »

This is where we depart from the perspectives of the old astronomers for they gauged all motions through the field of stars including the Sun whereas the resolution for inner retrogrades and the grandstand view of planetary motions around the Sun (shown in your image) demands a shift in perspective to account for the Earth's orbital motion and a fixed reference for the motions of Venus and Mercury.

A shift in perspective championed by Copernicus, and supported (independently) by Galileo and Kepler.

Tycho believed in a different system, but one which explained retrograde motions (and the phases of the inner planets) just as well: The Earth stationary, with the Moon and Sun orbiting it, and all the other planets orbiting the Sun.

gkell11

Zubeneschamali wrote: »

A shift in perspective championed by Copernicus, and supported (independently) by Galileo and Kepler.

Make yourself useful and post that YouTube graphic 'Constellations of the zodiac' ( the only suitable graphic I could find presently) which shows how the Earth's orbital motion accounts for the apparent motion of ElNath,Pollux and Castor in sequence behind the central Sun thereby allowing the grandstand view of retrogrades and what they mean in terms of orbital motion,phases and so on.