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3rd Kepler law, twin stars, centres, and semi major axis



 
 
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  #11  
Old February 21st 16, 09:52 AM posted to sci.astro
Poutnik[_5_]
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Posts: 68
Default 3rd Kepler law, twin stars, centres, and semi major axis

Dne 21/02/2016 v 09:52 Peter Riedt napsal(a):

Newton copied his law from Kepler, not the other way.

You got it wrong. In science, everything new
is built on the top of what was known before.
It is not like copying in art.

Kepler laws are not laws, but empirical rules,
based on Tycho de Brahe data.

They are rules of planetry kinematic,
they say nothing about gravitational interaction,
being proportional to masses
and reciprocal to squared distance.

Newton law is low of gravitational interaction,
similarly as the Coulomb law for electrostatic interaction.

All Kepler laws(rules) are direct consequence of the Newton law,
that furthermore is not limited to ellipses.


--
Poutnik ( the Czech word for a wanderer )

Knowledge makes great men humble, but small men arrogant.
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  #12  
Old February 21st 16, 11:15 AM posted to sci.physics.relativity,sci.physics,sci.astro
Thomas 'PointedEars' Lahn
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Posts: 76
Default 3rd Kepler law, twin stars, centres, and semi major axis

Poutnik wrote:

Dne 20/02/2016 v 23:07 Thomas 'PointedEars' Lahn napsal(a):
Poutnik wrote in sci.physics, sci.astro, and sci.physics.relativity:
Dne 20/02/2016 v 17:55 Thomas 'PointedEars' Lahn napsal(a):
I do not see the reason why did you hijacked my post to SPR,
as nature of topic is not SR/GR related.

Nothing was "hijacked […] to SPR", especially not "your post".

You have crossposted without Followup-To (which is unwise at best) to
sci.physics and sci.astro, and I have set Followup-To to the newsgroup
where I think that this discussion belongs. You might disagree, but
that does not give you the right to throw insults.


Follow-to is not mandatory,


That depends on the server that one uses; there are servers that would not
allow crossposting without Followup-To, or crossposting to more than three
newsgroups. There are newsreaders that would issue a warning on attempt.
At least it is the polite and recommended behavior to respect the
organization of Usenet into *topics*, and set Followup-To accordingly.
Likewise, it is the polite and recommended behavior to trim one’s quotes to
the parts that one is referring to. You did neither.

default behavior is following to crossposted groups.


Which is why it is a bad idea.

“No posting is relevant to more than a handful of newsgroups.
If World War III is announced, it will be announced in
news.announce.important.”
–Peter da Silva (translated)

See also “no spam” in http://www.eternal-september.org/index.php?language=en&showpage=terms.

Similarly ReplyTo in mails is not mandatory,
with default reply to the sender.


The important difference being that the e-mail is still directed to only a
few people or one person.

Most of stars of binary systems are not twins,
while twin stars are most probably not
a part of the same binary system.


It is the modern definition of a binary star (system) that it is actually
two stars revolving around a common center of mass. You are confusing
*double* stars with *binary* stars and *twin* stars.

A “twin star”, by contrast, would be *one* star that has approximately
the same characteristics as another star (cf. “twin planet”) where
nothing would be implied about their orbits. But your definition above
proves that you were not referring to that.


No, you have misinterpreted my words.
You can see there is no redundancy.
2 stars being twins and being bonded in binary system
are 2 indenpendent pieces of information.


I have not misinterpreted your words. You have claimed that “twin stars are
most probably not a part of the same binary system.” Lack of evidence
notwithstanding, as “twin star” usually means something else than you think
it does, your statement is nonsense. You can invent your own terminology,
but you should not be surprised if that leads to misunderstandings and
others frown when you insist on that only your private terminology is the
correct one.

Therefore, as Isaac Newton (1687) showed already, Kepler’s laws are
only an approximation of the observed planetary motion.

^^^^^^^^^^^^^^^^
But it is not fully the case of the 3rd law with sum of masses.

^^^^^^^^^^^^^^^^^^
I beg your pardon?


..obsessive nitpicking arrogance...


/Ad hominem/ again because you cannot face the fact that your statement
is wrong. In fact, both you and the resource that you cite claim that
the approximation of Kepler’s laws *holds* in the case of binary stars.

It is applicable as well for planet-moon systems


No doubt about that, although there appears to be no official (IAU)
definition what distinguishes a planet–moon system from a double planet
system.


It does not really matter, it can be generalized to all 2 body systems,


Then there was no reason to mention this as a special case, was there?

where GR effects can be still beglegted.


YSCIB.

GR effects for stars of Sun mass at distance 2 AU are very minor,


There are stars in binary star systems that have masses greater than the
Sun and a minimum distance from each other less than 2 AU. For example,

Eta
Carinae A has ≈120 to {170 to 200} M☉, and Eta Carinae B has 30 to 80 M☉
[1], while the minimum distance between the stars is estimated to be 1.6
[AU 2] (the orbits are highly eccentric, which is why it took so long to
recognize that Eta Carinae is actually a binary star system).

https://en.wikipedia.org/wiki/Eta_Carinae


I am aware about Eta Carinae.


So you were deliberately misrepresenting the facts, i.e. lying? Because Eta
Carinae, for example, shows that you are proceeding from a false assumption,
namely that GR would never be needed to describe binary star systems
*properly*.

and negligible wrt to accuracy of data.

Either do the math or cite evidence in which the math is done.


If you think about it more, you will agree,
considering accuracy of the periods and distances.


IOW, you are not able or willing to substantiate your claims. Figures.

Score adjusted.

F'up2 sci.physics.relativity

PointedEars
--
Q: What did the female magnet say to the male magnet?
A: From the back, I found you repulsive, but from the front
I find myself very attracted to you.
(from: WolframAlpha)
  #13  
Old February 21st 16, 11:46 PM posted to sci.astro
Peter Riedt
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Posts: 83
Default 3rd Kepler law, twin stars, centres, and semi major axis

On Sunday, February 21, 2016 at 5:52:24 PM UTC+8, Poutnik wrote:
Dne 21/02/2016 v 09:52 Peter Riedt napsal(a):

Newton copied his law from Kepler, not the other way.

You got it wrong. In science, everything new
is built on the top of what was known before.
It is not like copying in art.

Yes.

Kepler laws are not laws, but empirical rules,
based on Tycho de Brahe data.

And Kepler's own observations.

They are rules of planetry kinematic,
they say nothing about gravitational interaction,
being proportional to masses
and reciprocal to squared distance.

Explicit yes, implicit no.

Newton law is low of gravitational interaction,
similarly as the Coulomb law for electrostatic interaction.

Mean what?

All Kepler laws(rules) are direct consequence of the Newton law,
that furthermore is not limited to ellipses.

Newton is a consequence of Kepler's laws. Yes Newton covers inertia.

--
Poutnik ( the Czech word for a wanderer )

Knowledge makes great men humble, but small men arrogant.


  #14  
Old February 22nd 16, 05:51 AM posted to sci.astro
Poutnik[_5_]
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Posts: 68
Default 3rd Kepler law, twin stars, centres, and semi major axis

Dne 22/02/2016 v 00:46 Peter Riedt napsal(a):


Newton law is low of gravitational interaction,
similarly as the Coulomb law for electrostatic interaction.

Mean what?


That any gravitational interaction obeys it,
in context of non relativistic physics.

All Kepler laws(rules) are direct consequence of the Newton law,
that furthermore is not limited to ellipses.


Newton is a consequence of Kepler's laws. Yes Newton covers inertia.


Exactly the opposite, even if it is younger.

Aside of that,
the 2nd law is consequence of law of angular momentum conservation.

--
Poutnik ( the Czech word for a wanderer )

Knowledge makes great men humble, but small men arrogant.
  #15  
Old February 22nd 16, 06:08 AM posted to sci.astro
Poutnik[_5_]
external usenet poster
 
Posts: 68
Default 3rd Kepler law, twin stars, centres, and semi major axis

Dne 22/02/2016 v 00:46 Peter Riedt napsal(a):
On Sunday, February 21, 2016 at 5:52:24 PM UTC+8, Poutnik wrote:



All Kepler laws(rules) are direct consequence of the Newton law,
that furthermore is not limited to ellipses.


Newton is a consequence of Kepler's laws. Yes Newton covers inertia.


Kepler laws-rule are just observed patterns of behaviour,
that occur at very special conditions,
they do not have general validity needed for the law.

It is enough if mass ratio is not high enough,
if speed is too high
or if there are more than 3 objects,
to rule these rules out.

But as pattern of behaviour, they prepared the ground
to discovering the law, that rules over all this phenomena,
manifesting itself in special cases as Kepler laws.

--
Poutnik ( the Czech word for a wanderer )

Knowledge makes great men humble, but small men arrogant.
  #16  
Old February 22nd 16, 06:28 AM posted to sci.astro
Poutnik[_5_]
external usenet poster
 
Posts: 68
Default 3rd Kepler law, twin stars, centres, and semi major axis

Dne 22/02/2016 v 00:46 Peter Riedt napsal(a):
On Sunday, February 21, 2016 at 5:52:24 PM UTC+8, Poutnik wrote:



They are rules of planetary kinematic,
they say nothing about gravitational interaction,
being proportional to masses
and reciprocal to squared distance.


Explicit yes, implicit no.


Because implicitly,
they hide the Newton law laying behind them,
that was waiting to be discovered.

Kepler laws are inaccurate, up to useless in 3 body cases,
like in case of an asteroid,
orbiting the Sun near the Jupiter orbit.

But Newton law describes its irregular orbit well,
in context of classical physics.


--
Poutnik ( the Czech word for a wanderer )

Knowledge makes great men humble, but small men arrogant.
  #17  
Old February 22nd 16, 11:34 PM posted to sci.astro
Peter Riedt
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Posts: 83
Default 3rd Kepler law, twin stars, centres, and semi major axis

On Monday, February 22, 2016 at 2:28:14 PM UTC+8, Poutnik wrote:
Dne 22/02/2016 v 00:46 Peter Riedt napsal(a):
On Sunday, February 21, 2016 at 5:52:24 PM UTC+8, Poutnik wrote:



They are rules of planetary kinematic,
they say nothing about gravitational interaction,
being proportional to masses
and reciprocal to squared distance.


Explicit yes, implicit no.


Because implicitly,
they hide the Newton law laying behind them,
that was waiting to be discovered.

Kepler laws are inaccurate, up to useless in 3 body cases,
like in case of an asteroid,
orbiting the Sun near the Jupiter orbit.

But Newton law describes its irregular orbit well,
in context of classical physics.

Orbits of any solar object is calculated by Kepler's laws not Newton's.
  #18  
Old February 23rd 16, 07:10 AM posted to sci.astro
Poutnik[_5_]
external usenet poster
 
Posts: 68
Default 3rd Kepler law, twin stars, centres, and semi major axis

Dne 23/02/2016 v 00:34 Peter Riedt napsal(a):


Orbits of any solar object is calculated by Kepler's laws not Newton's.

False. think about it little bit more.

Calculate orbit of an asteroid 20 km big with density 2 g/ccm
with an orbit identical to the Jupiter one, but 5 percent smaller,
being at t=0 in conjunction.

Tell by Kepler laws, how the orbit will look after 1000 years,
considering gravitational disturbation of the Jupiter.

---------
Kepler laws are by design focused on 2 body systems only.
They are principally inaccurate for systems with more than 2 bodies,
as they do not take into account the influence of other bodies.

This influence is very significant especially for small objects
as asteroids and comets that frequently change their orbits due big
objects. Close passes and orbit resonances are especially powerful.

--
Poutnik ( the Czech word for a wanderer )

Knowledge makes great men humble, but small men arrogant.
  #19  
Old February 23rd 16, 07:18 AM posted to sci.astro
Poutnik[_5_]
external usenet poster
 
Posts: 68
Default 3rd Kepler law, twin stars, centres, and semi major axis

Dne 23/02/2016 v 00:34 Peter Riedt napsal(a):
On Monday, February 22, 2016 at 2:28:14 PM UTC+8, Poutnik wrote:



Because implicitly,
they hide the Newton law laying behind them,
that was waiting to be discovered.

Kepler laws are inaccurate, up to useless in 3 body cases,
like in case of an asteroid,
orbiting the Sun near the Jupiter orbit.

But Newton law describes its irregular orbit well,
in context of classical physics.

Orbits of any solar object is calculated by Kepler's laws not Newton's.

What the Kepler laws ARE used for
is estimation of the total mass of mutually orbiting objects
from the period and their distance/orbiting speed.

E.g. by analysis spectrum of spectroscopical binary star.
--

But any precise calculations within our Solar system
uses Newton laws with multiple bodies.

--
Poutnik ( the Czech word for a wanderer )

Knowledge makes great men humble, but small men arrogant.
  #20  
Old February 23rd 16, 09:07 AM posted to sci.astro
Martin Brown
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Posts: 1,707
Default 3rd Kepler law, twin stars, centres, and semi major axis

On 21/02/2016 08:52, Peter Riedt wrote:
On Sunday, February 21, 2016 at 4:26:41 PM UTC+8, Poutnik wrote:
Dne 21/02/2016 v 03:23 Peter Riedt napsal(a):



Kepler's third law (from the early 1600s) gave us the relative
sizes of the orbits. T^2 ~ a^3

Isaac Newton's version of Kepler's third law
T^2 == (2π)^2 a^3 / G(M+m)

where (2π)^2/G is just a constant of proportionality.


The fundamental point it that Newton proved that the solar system
movements were the result of an inverse square law. It is arguable that
Hooke guessed this mentioned it to Newton who had the mathematical
techniques to prove it. But either way they added a lot to
understanding. Kepler's laws were empirical derived from observations
Newtons was derived theoretically from a set of starting axioms.

Orbits of earth and solar system satellites today are described by
their Keplerian Elements.
https://en.wikipedia.org/wiki/Orbital_elements

Science not only grasped the significance of Kepler's third law,
but make use of it 24/7.


The point is, Kepler laws are laws just by name,
being empirical rules as consequence of the Newton gravity law.

Not the otherwise.


Newton copied his law from Kepler, not the other way.


No.

Newton explained it in terms that we use in classical mechanics as
conservation of energy and conservation of angular momentum.

There are analogous conserved quantities in GR too.

It should be no surprise that each successive improvementof a theory
contains all previous models as a limiting subset of the new model.

--
Regards,
Martin Brown
 




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