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  #61  
Old January 29th 21, 05:19 AM posted to rec.bicycles.tech
Ralph Barone[_4_]
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Posts: 853
Default 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  
Old January 29th 21, 05:41 AM posted to rec.bicycles.tech
Frank Krygowski[_2_]
external usenet poster
 
Posts: 7,511
Default 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  
Old January 29th 21, 05:42 AM posted to rec.bicycles.tech
Frank Krygowski[_2_]
external usenet poster
 
Posts: 7,511
Default 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  
Old January 29th 21, 06:01 AM posted to rec.bicycles.tech
Radey Shouman
external usenet poster
 
Posts: 1,747
Default 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  
Old January 29th 21, 06:03 AM posted to rec.bicycles.tech
Radey Shouman
external usenet poster
 
Posts: 1,747
Default 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  
Old January 29th 21, 06:05 AM posted to rec.bicycles.tech
Radey Shouman
external usenet poster
 
Posts: 1,747
Default 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  
Old January 29th 21, 08:03 AM posted to rec.bicycles.tech
Jeff Liebermann
external usenet poster
 
Posts: 4,018
Default 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  
Old January 29th 21, 06:20 PM posted to rec.bicycles.tech
Frank Krygowski[_4_]
external usenet poster
 
Posts: 10,538
Default 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  
Old January 29th 21, 06:27 PM posted to rec.bicycles.tech
Tom Kunich[_4_]
external usenet poster
 
Posts: 2,196
Default 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  
Old January 29th 21, 06:32 PM posted to rec.bicycles.tech
Frank Krygowski[_4_]
external usenet poster
 
Posts: 10,538
Default 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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