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#61
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OT: little tommy's little rocket
On Thu, 28 Jan 2021 14:43:33 -0800, Tom Kunich scribed:
Come on Ralph, even though we can't tell within a mile or two where Pluto is going to be, we can correct course when we get near it. I could design all of the course correction and rocket motion stuff without a problem. This was my business. Which was my exact point. Just because you can’t find an exact analytical solution, doesn’t mean you can’t get the job done. |
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#62
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YouTube - We Still Don’t Know How Bicycles Work
On Thursday, January 28, 2021 at 10:08:34 PM UTC-5, News 2021 wrote:
On Thu, 28 Jan 2021 20:02:42 -0600, AMuzi scribed: On 1/28/2021 5:54 PM, Frank Krygowski wrote: I think "orbit" by definition excludes an object with escape velocity. To orbit means to do it more than once. But I agree that an object passing by then escaping would have a hyperbolic trajectory. They're not exclusive, periodic comets f'instance. Err, are they not "orbiting something, real or imaginary, in space to be periodic? Yes indeed. A periodic comet is in orbit around the sun, although it may be an extremely eccentric orbit, with a period of hundreds or thousands of years. Those paths would be elliptical. An object doing a "fly by" like the one a couple years ago would have a hyperbolic trajectory. - Frank Krygowski |
#63
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OT: little tommy's little rocket YouTube - We Still Don´t Know How Bicycles Work
On Thursday, January 28, 2021 at 11:19:24 PM UTC-5, Ralph Barone wrote:
On Thu, 28 Jan 2021 14:43:33 -0800, Tom Kunich scribed: Come on Ralph, even though we can't tell within a mile or two where Pluto is going to be, we can correct course when we get near it. I could design all of the course correction and rocket motion stuff without a problem. This was my business. Which was my exact point. Just because you can’t find an exact analytical solution, doesn’t mean you can’t get the job done. +1 - Frank Krygowski |
#64
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YouTube - We Still Don’t Know How BicyclesWork
Frank Krygowski writes:
On 1/28/2021 4:50 PM, Radey Shouman wrote: Tom Kunich writes: On Thursday, January 28, 2021 at 9:08:18 AM UTC-8, AMuzi wrote: On 1/28/2021 6:00 AM, Rolf Mantel wrote: Am 27.01.2021 um 19:19 schrieb Tom Kunich: On Wednesday, January 27, 2021 at 1:34:38 AM UTC-8, Rolf Mantel wrote: Am 25.01.2021 um 22:44 schrieb Tom Kunich: On Monday, January 25, 2021 at 10:57:32 AM UTC-8, Frank Krygowski wrote: But a warning: Those guys use math. Why don't you tell us about that math that can measure the circumference of a oval? Math does not "measure" but "calculate". Before you can start using math, you need a precise description what you mean by "oval" (and as soon as you give a precise definition, someboda can find a formula for its circumference). The simplest version of an oval (also called "stadium" according to wikipedia) is a circle cut through in the middle where the halves are connected by straight lines, so it is defined by r = "Radius of each semi-circle" a = "distance between the two centers of the semi-circles" https://en.wikipedia.org/wiki/Stadium_(geometry) For this oval, the formula is quite simply 2( pi * r + a) Please do not argue the meanings of words when you know what is meant. And do not take a single special case that can be measured accurately and pretend that it is fitting for all cases. Tell us the perimeter of the orbit of Pluto and then we can see your accuracies? Do you understand what is Mathematics and what is not Mathematics? The "Orbit of Pluto" is not Mathematics, it's Astronomy, and it is not an oval by any definition (Wikipedia claims it's chaotic due to the 2:3 resonance with Neptune; the Mathematician and Astronomer Pointcare proved in the 1890's that the Newtonian interaction of three celestrial bodies usually leads to "chaos", defining for the first time what chaos is mathematically). Only when an Astronomer says "Pluto's orbit can be approximated by an ellipse with long axis 49 AU and short axis 30 AU for my purposes", the mathematician can start calculating the perimeter of that ellipse as a meaningful approximation for the Astronomer. Rolf Basically yes but it's not an ellipse. (a figure with two foci: https://www.assignmentpoint.com/wp-c.../Ellipse-1.jpg ) A planet's orbit can be observed and described. It could probably be measured but probably not calculated given all of human knowledge to here as the inputs are myriad (not only Neptune!) and dynamic. Argue this with NASA if you like "All orbits are elliptical, which means they are an ellipse, similar to an oval. For the planets, the orbits are almost circular. The orbits of comets have a different shape. Even if third bodies are ignored entirely, all orbits are not elliptical. Some are hyperbolic. This happens with comets that are traveling relative to the sun at higher than escape velocity -- they enter the solar system and then leave, never to return. I think "orbit" by definition excludes an object with escape velocity. To orbit means to do it more than once. I see many uses of the term "hyperbolic orbit", eg https://history.nasa.gov/conghand/traject.htm As we've just discussed, real world "elliptic" orbits aren't really closed paths either. But I agree that an object passing by then escaping would have a hyperbolic trajectory. -- |
#65
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YouTube - We Still Don’t Know How BicyclesWork
Frank Krygowski writes:
On Thursday, January 28, 2021 at 10:08:34 PM UTC-5, News 2021 wrote: On Thu, 28 Jan 2021 20:02:42 -0600, AMuzi scribed: On 1/28/2021 5:54 PM, Frank Krygowski wrote: I think "orbit" by definition excludes an object with escape velocity. To orbit means to do it more than once. But I agree that an object passing by then escaping would have a hyperbolic trajectory. They're not exclusive, periodic comets f'instance. Err, are they not "orbiting something, real or imaginary, in space to be periodic? Yes indeed. A periodic comet is in orbit around the sun, although it may be an extremely eccentric orbit, with a period of hundreds or thousands of years. Those paths would be elliptical. An object doing a "fly by" like the one a couple years ago would have a hyperbolic trajectory. Wikipedia will give you a list: https://en.wikipedia.org/wiki/List_of_hyperbolic_comets |
#66
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YouTube - We Still Don’t Know How BicyclesWork
Frank Krygowski writes:
On 1/28/2021 4:54 PM, Radey Shouman wrote: Ralph Barone writes: AMuzi wrote: On 1/28/2021 6:00 AM, Rolf Mantel wrote: Am 27.01.2021 um 19:19 schrieb Tom Kunich: On Wednesday, January 27, 2021 at 1:34:38 AM UTC-8, Rolf Mantel wrote: Am 25.01.2021 um 22:44 schrieb Tom Kunich: On Monday, January 25, 2021 at 10:57:32 AM UTC-8, Frank Krygowski wrote: But a warning: Those guys use math. Why don't you tell us about that math that can measure the circumference of a oval? Math does not "measure" but "calculate". Before you can start using math, you need a precise description what you mean by "oval" (and as soon as you give a precise definition, someboda can find a formula for its circumference). The simplest version of an oval (also called "stadium" according to wikipedia) is a circle cut through in the middle where the halves are connected by straight lines, so it is defined by r = "Radius of each semi-circle" a = "distance between the two centers of the semi-circles" https://en.wikipedia.org/wiki/Stadium_(geometry) For this oval, the formula is quite simply 2( pi * r + a) Please do not argue the meanings of words when you know what is meant. And do not take a single special case that can be measured accurately and pretend that it is fitting for all cases. Tell us the perimeter of the orbit of Pluto and then we can see your accuracies? Do you understand what is Mathematics and what is not Mathematics? The "Orbit of Pluto" is not Mathematics, it's Astronomy, and it is not an oval by any definition (Wikipedia claims it's chaotic due to the 2:3 resonance with Neptune; the Mathematician and Astronomer Pointcare proved in the 1890's that the Newtonian interaction of three celestrial bodies usually leads to "chaos", defining for the first time what chaos is mathematically). Only when an Astronomer says "Pluto's orbit can be approximated by an ellipse with long axis 49 AU and short axis 30 AU for my purposes", the mathematician can start calculating the perimeter of that ellipse as a meaningful approximation for the Astronomer. Rolf Basically yes but it's not an ellipse. (a figure with two foci: https://www.assignmentpoint.com/wp-c.../Ellipse-1.jpg ) A planet's orbit can be observed and described. It could probably be measured but probably not calculated given all of human knowledge to here as the inputs are myriad (not only Neptune!) and dynamic. Interestingly enough, even with the theoretical impossibility of predicting Pluto’s orbit, we still managed to fly a probe past it and take pictures. I guess it was just a theoretical impossibility, and a little bit of negative feedback was enough to make it a practical possibility. https://www.space.com/18377-new-horizons.html Meteorologists can predict the weather reasonably well a week in advance. Two years, not so much. Astronomers have a very good idea of where Pluto will be in a ten years, but figuring out where it will be in a million years is really hard. But do we care? About the weather in two years? Yes, absolutely, think of how many more outdoor weddings there would be. |
#67
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YouTube - We Still Don’t Know How Bicycles Work
On Thu, 28 Jan 2021 11:14:47 -0800 (PST), Tom Kunich
wrote: Planetary orbits, even those of minor satellites are ellipses. This is what I was getting at when I said you cannot absolutely define the perimeter of an ellipse because you cannot know the precise measurements of an oval. Johannes Kepler did a fairly good job of reducing observations to orbital parameters in about 1597. https://en.wikipedia.org/wiki/Johannes_Kepler https://en.wikipedia.org/wiki/Orbital_elements ftp://ftp.lowell.edu/www_users/gerard/q_refs/keplerian%20elements%20for%20approx%20positions%20 of%20major%20planets.pdf If I wanted to track Pluto, the elements (parameters) are commonly available: https://www.princeton.edu/~willman/planetary_systems/Sol/Pluto/ Keplerian elements are also used to predict the orbits of earth satellites some of which are really eccentric. I download weekly copies of the latest Keplerian Elements from the ARRL for the various ham radio satellites: http://www.arrl.org/w1aw-bulletins-archive-keplerian and use them to aim an antenna on my roof and compensate for Doppler shift. Please don't tell me that I can't precisely track a planet or orbiting satellite because it's quite commonly done: https://www.nlsa.com More satellite tracking softwa https://www.google.com/search?q=satellite+tracking+software The bottom line is that moving celestial objects can be tracked by predicting their position based on observations. That boils down to how much accuracy do you want or need? Here's a PDF on what it takes for hams to track Voyager 1 and 2: http://www.learnbydestroying.com/jeffl/crud/Voyager-communications.pdf Such efforts would not have a chance of working unless we knew where to point the antenna. Please note the Earth is not a stationary platform and is spinning and orbiting continuously. For the 8.4GHz 20 meter diameter dish in the example, the -3dB beamwidth would be: 57 deg/radian * 0.0367 meters_wavelength / 20 meters_dish_diameter = 0.105 degrees. In order to aim such an antenna, one needs to be accurate to within: +/- 0.053 degrees. It's impossible without having a really good idea where the object you're pointing at is located in the sky (and have a really stable mount and pedestal). Even aiming a common Dish or DirecTV 0.6 meter DBS (direct broadcast satellite) dish is difficult without aiming (elevation, azimuth, LNB skew) information where the satellites are spaced 2 degrees apart along the ecliptic. What did you do at NASA? https://groups.google.com/g/rec.bicycles.tech/c/CCfxzu4WFgY/m/1MNTZOPxAgAJ "For someone without an education that didn't seem to trouble Laurence Livermore Laboratories, Laurence Berkeley Laboratories or NASA." Drivel: KSCO C-Band satellite feeds from hell: http://www.learnbydestroying.com/jeffl/antennas/dish-move-project/index.html http://www.learnbydestroying.com/jeffl/antennas/dish-new-install-project/index.html http://www.learnbydestroying.com/jeffl/antennas/dish-move-03/index.html I didn't need Keplerian elements to locate these satellites because they were all geosychronous satellites, which don't move (much) in the sky. However, aiming was still very difficult. -- Jeff Liebermann PO Box 272 http://www.LearnByDestroying.com Ben Lomond CA 95005-0272 Skype: JeffLiebermann AE6KS 831-336-2558 |
#68
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YouTube - We Still Don’t Know How Bicycles Work
On 1/29/2021 12:01 AM, Radey Shouman wrote:
Frank Krygowski writes: On 1/28/2021 4:50 PM, Radey Shouman wrote: Tom Kunich writes: On Thursday, January 28, 2021 at 9:08:18 AM UTC-8, AMuzi wrote: On 1/28/2021 6:00 AM, Rolf Mantel wrote: Am 27.01.2021 um 19:19 schrieb Tom Kunich: On Wednesday, January 27, 2021 at 1:34:38 AM UTC-8, Rolf Mantel wrote: Am 25.01.2021 um 22:44 schrieb Tom Kunich: On Monday, January 25, 2021 at 10:57:32 AM UTC-8, Frank Krygowski wrote: But a warning: Those guys use math. Why don't you tell us about that math that can measure the circumference of a oval? Math does not "measure" but "calculate". Before you can start using math, you need a precise description what you mean by "oval" (and as soon as you give a precise definition, someboda can find a formula for its circumference). The simplest version of an oval (also called "stadium" according to wikipedia) is a circle cut through in the middle where the halves are connected by straight lines, so it is defined by r = "Radius of each semi-circle" a = "distance between the two centers of the semi-circles" https://en.wikipedia.org/wiki/Stadium_(geometry) For this oval, the formula is quite simply 2( pi * r + a) Please do not argue the meanings of words when you know what is meant. And do not take a single special case that can be measured accurately and pretend that it is fitting for all cases. Tell us the perimeter of the orbit of Pluto and then we can see your accuracies? Do you understand what is Mathematics and what is not Mathematics? The "Orbit of Pluto" is not Mathematics, it's Astronomy, and it is not an oval by any definition (Wikipedia claims it's chaotic due to the 2:3 resonance with Neptune; the Mathematician and Astronomer Pointcare proved in the 1890's that the Newtonian interaction of three celestrial bodies usually leads to "chaos", defining for the first time what chaos is mathematically). Only when an Astronomer says "Pluto's orbit can be approximated by an ellipse with long axis 49 AU and short axis 30 AU for my purposes", the mathematician can start calculating the perimeter of that ellipse as a meaningful approximation for the Astronomer. Rolf Basically yes but it's not an ellipse. (a figure with two foci: https://www.assignmentpoint.com/wp-c.../Ellipse-1.jpg ) A planet's orbit can be observed and described. It could probably be measured but probably not calculated given all of human knowledge to here as the inputs are myriad (not only Neptune!) and dynamic. Argue this with NASA if you like "All orbits are elliptical, which means they are an ellipse, similar to an oval. For the planets, the orbits are almost circular. The orbits of comets have a different shape. Even if third bodies are ignored entirely, all orbits are not elliptical. Some are hyperbolic. This happens with comets that are traveling relative to the sun at higher than escape velocity -- they enter the solar system and then leave, never to return. I think "orbit" by definition excludes an object with escape velocity. To orbit means to do it more than once. I see many uses of the term "hyperbolic orbit", eg https://history.nasa.gov/conghand/traject.htm I'm sure there are plenty of casual uses of the term "orbit," even (as you showed) by NASA. But ISTM the definition of "orbit" from a reputable source makes reference to the path being repeated. For example, https://www.nasa.gov/audience/forstu...-orbit-58.html -- - Frank Krygowski |
#69
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YouTube - We Still Don’t Know How Bicycles Work
On Thursday, January 28, 2021 at 6:03:13 PM UTC-8, AMuzi wrote:
On 1/28/2021 5:54 PM, Frank Krygowski wrote: On 1/28/2021 4:50 PM, Radey Shouman wrote: Tom Kunich writes: On Thursday, January 28, 2021 at 9:08:18 AM UTC-8, AMuzi wrote: On 1/28/2021 6:00 AM, Rolf Mantel wrote: Am 27.01.2021 um 19:19 schrieb Tom Kunich: On Wednesday, January 27, 2021 at 1:34:38 AM UTC-8, Rolf Mantel wrote: Am 25.01.2021 um 22:44 schrieb Tom Kunich: On Monday, January 25, 2021 at 10:57:32 AM UTC-8, Frank Krygowski wrote: But a warning: Those guys use math. Why don't you tell us about that math that can measure the circumference of a oval? Math does not "measure" but "calculate". Before you can start using math, you need a precise description what you mean by "oval" (and as soon as you give a precise definition, someboda can find a formula for its circumference). The simplest version of an oval (also called "stadium" according to wikipedia) is a circle cut through in the middle where the halves are connected by straight lines, so it is defined by r = "Radius of each semi-circle" a = "distance between the two centers of the semi-circles" https://en.wikipedia.org/wiki/Stadium_(geometry) For this oval, the formula is quite simply 2( pi * r + a) Please do not argue the meanings of words when you know what is meant. And do not take a single special case that can be measured accurately and pretend that it is fitting for all cases. Tell us the perimeter of the orbit of Pluto and then we can see your accuracies? Do you understand what is Mathematics and what is not Mathematics? The "Orbit of Pluto" is not Mathematics, it's Astronomy, and it is not an oval by any definition (Wikipedia claims it's chaotic due to the 2:3 resonance with Neptune; the Mathematician and Astronomer Pointcare proved in the 1890's that the Newtonian interaction of three celestrial bodies usually leads to "chaos", defining for the first time what chaos is mathematically). Only when an Astronomer says "Pluto's orbit can be approximated by an ellipse with long axis 49 AU and short axis 30 AU for my purposes", the mathematician can start calculating the perimeter of that ellipse as a meaningful approximation for the Astronomer. Rolf Basically yes but it's not an ellipse. (a figure with two foci: https://www.assignmentpoint.com/wp-c.../Ellipse-1.jpg ) A planet's orbit can be observed and described. It could probably be measured but probably not calculated given all of human knowledge to here as the inputs are myriad (not only Neptune!) and dynamic. Argue this with NASA if you like "All orbits are elliptical, which means they are an ellipse, similar to an oval. For the planets, the orbits are almost circular. The orbits of comets have a different shape. Even if third bodies are ignored entirely, all orbits are not elliptical. Some are hyperbolic. This happens with comets that are traveling relative to the sun at higher than escape velocity -- they enter the solar system and then leave, never to return. I think "orbit" by definition excludes an object with escape velocity. To orbit means to do it more than once. But I agree that an object passing by then escaping would have a hyperbolic trajectory. They're not exclusive, periodic comets f'instance. Comets in Earth orbit are always scary because their orbits cannot be calculated with any true accuracy. Every time they pass it could be a collision course. It was the cause of at least one extinction event. |
#70
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YouTube - We Still DonÂ’t Know How Bicycles Work
On 1/29/2021 2:03 AM, Jeff Liebermann wrote:
Please don't tell me that I can't precisely track a planet or orbiting satellite because it's quite commonly done: https://www.nlsa.com More satellite tracking softwa https://www.google.com/search?q=satellite+tracking+software I'm not disagreeing with the above. But vaguely related: For a few years I've been working on a Reflecting Ceiling Sundial. Something similar to this https://diallist.files.wordpress.com...-600-x-450.jpg in which a horizontal bit of mirror bounces a moving dot of sunlight onto the ceiling. (The curves are analemmas - you can look that up.) I began by marking the position of the "sundot" on the ceiling at various times of day. But this is one of the cloudiest areas of the country, and I've got a huge elm tree overhanging my house, so it's often difficult to get the data point I want. For a while, I thought I'd be better off simply computing the coordinates of the sundot, starting with the precise position of the sun at any date and time. It turns out it's surprisingly difficult to get a truly precise result for position of the sun and it's "sundot"! I eventually abandoned the calculation and went back to simply marking hundreds of points on the ceiling. -- - Frank Krygowski |
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