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, default behavior is following
to crossposted groups. Similarly ReplyTo in mails is not mandatory,
with default reply to the sender.



Twin is adjective describing stars of a binary star system,
while binary is adjective describing their relation.

Nonsense. https://en.wikipedia.org/wiki/Binary_star



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.






Kepler’s laws (1609–1619 CE) are laws of *planetary* motion. They were
........
Church, for which he was burned at the stake in 1600.]

I am quite familiar with this history.

Obviously you *were* not. And you have not only distorted, but completely
destroyed the context of my statement. Learn to quote.

You should do so at the first place, responding to the OP.
BTW, it was general comment to the paragraph. Everybody can review the
full version. IF I was reacting to particular statements, I would
mention them.

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...


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,
where GR effects can be still beglegted.

and binary star systems.

But the error increases with mass and decreases with minimum distance.

I do not object and I am aware of it.
But I suppose the evaluate the masses first by the Kepler law
from observed periods and distances.
Then, if combination of masses and distance calls for GR application,
that is is done.

See e.g. http://www.astro.caltech.edu/~george...Ay20-Lec4x.pdf
Kepler’s Laws, Binaries, and Stellar Masses.

Interesting. So much more… surprising that you have not cited this in your
OP, but mispresented those findings as your own.

I have not cited as I have found it AFTER your response.
But I was aware of this application even before I have found it.

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.

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.

Generally, not limited to binary stars,
there are cases where usage of Newton gravity is not justified
and
there are cases where usage of GR is not justified.



--
Poutnik ( the Czech word for a wanderer )

Knowledge makes great men humble, but small men arrogant.