Black Holes .

[Write4U]

It's interesting to follow the history of the term "planet".

The issue of a clear definition for planet came to a head in January 2005 with the discovery of the trans-Neptunian object Eris, a body more massive than the smallest then-accepted planet, Pluto.

In its August 2006 response, the International Astronomical Union (IAU), recognised by astronomers as the world body responsible for resolving issues of nomenclature, released its decision on the matter during a meeting in Prague. This definition, which applies only to the Solar System, states that a planet is a body that orbits the Sun, is massive enough for its own gravity to make it round, and has "cleared its neighbourhood" of smaller objects around its orbit.

Under this new definition, Pluto and the other trans-Neptunian objects do not qualify as planets. The IAU's decision has not resolved all controversies, and while many scientists have accepted the definition, some in the astronomical community have rejected it outright.
In particular, some favor a strictly geophysical definition of a plane

Of course it all started some way back;

The definition of planet, since the word was coined by the ancient Greeks, has included within its scope a wide range of celestial bodies. Greek astronomersemployed the term asteres planetai (ἀστέρες πλανῆται), "wandering stars", for star-like objects which apparently moved over the sky. Over the millennia, the term has included a variety of different objects, from the Sun and the Moon to satellites and asteroids.

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

Which of course is much broader in scope than it is now.

 

[davewhite04]

Thank you Janus58 for that excellent explanation of the definitive differences in terms.

I tend to categorize things by common denominators, rather than by what sets them apart.
This does get me in trouble once in awhile.....

You'd get sacked if you were a high school science teacher. A good thing.

 

[DaveC426913]

In effect yes, you did say that only planets orbit stars.

I said nothing of the sort, 'in effect' or otherwise.
You have misread something, which explains why your responses are non sequitur.

Everything revolves around other things, its a basic universal phenomenon that explains gravity

We agree on this. No one has said otherwise. Please review the thread.
If you're uncertain, feel free to quote something, we I can see where you went awry.

 

[DaveC426913]

I tend to categorize things by common denominators, rather than by what sets them apart.

Yes, and this has its place. But sometimes it does not have its place, and simply leads to confusion.

A implies B.
It does not follow that B implies A.

'Planet' implies 'orbit'. (except for rogues, this is pretty much true)

'Orbit' implies 'planet'. (False. Orbit implies a large list of things not planet-like: asteroid, moon, spaceship, star, galaxy, supercluster etc.)

That is the trap you fell into in post 172.

 

[davewhite04]

Yes, and this has its place. But sometimes it does not have its place, and simply leads to confusion.

A implies B.
It does not follow that B implies A.

'Planet' implies 'orbit'. (except for rogues, this is pretty much true)

'Orbit' implies 'planet'. (False. Orbit implies a large list of things not planet-like: asteroid, moon, spaceship, star, galaxy, supercluster etc.)

That is the trap you fell into in post 172.

It's just scientific schematics, who cares?

 

[DaveC426913]

It's just scientific schematics, who cares?

'Scientific schematics'? You mean like blueprints?

Write4U seems to care.

 

[davewhite04]

'Scientific schematics'? You mean like blueprints?

Write4U seems to care.

Well if you want to join the science blueprint you'll never be right, over time.

 

[DaveC426913]

Well if you want to join the science blueprint you'll never be right, over time.

You follow a cryptic comment with another cryptic comment.

I retain some faint hope that some on-topic content may yet rise from the ashes of this thread on black holes.

 

[Write4U]

'Scientific schematics'? You mean like blueprints?

Write4U seems to care.

Yes, and it seems I am not alone. Geologists particularly are not happy with the current definition.

In 2006, during their 26th General Assembly, the International Astronomical Union (IAU) adopted a formal definition of the term "planet". This was done in the hopes of dispelling ambiguity over which bodies should be designated as "planets", an issue that had plagued astronomers ever since they discovered objects beyond the orbit of Neptune that were comparable in size to Pluto.

..................

From this more basic set of parameters, Runyon and his colleagues have suggested the following definition:
"A planet is a sub-stellar mass body that has never undergone nuclear fusion and that has sufficient self-gravitation to assume a spheroidal shape adequately described by a triaxial ellipsoid regardless of its orbital parameters."

As Runyon told Universe Today in a phone interview, this definition is an attempt to establish something that is useful for all those involved in the study of planetary science, which has always included geologists:
"The IAU definition is useful to planetary astronomers concerned with the orbital properties of bodies in the solar system, and may capture the essence of what a 'planet' is to them. The definition is not useful to planetary geologists. I study landscapes and how landscapes evolve. It also kind of irked me that the IAU took upon itself to define something that geologists use too.

https://phys.org/news/2017-02-geophysical-planet-definition.html

 

[river]

third hole to my planet ...

ode to the black hole sun
you are my schwarzschild radius



pure essence ...

So you can't define the essence of a BH , in the physical ; it is purely a mathematical concept .

 

[Write4U]

So you can't define the essence of a BH .

If you're looking for gravity;

The Schwarzschild radius (sometimes historically referred to as the gravitational radius) is a physical parameter that shows up in the Schwarzschild solution to Einstein's field equations, corresponding to the radius defining the event horizon of a Schwarzschild black hole. It is a characteristic radius associated with every quantity of mass.

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

i.e. the Schwarzschild radius is a geometric potential and therefore an essence of a BH.

 

[river]

So you can't define the essence of a BH , in the physical ; it is purely a mathematical concept .

Gravity?

Yet gravity waves emanate; not turn inwards upon themselves . If they did , turn inwards , the gravity wave would never exist .

 

[DaveC426913]

So you can't define the essence of a BH , in the physical ; it is purely a mathematical concept .

Well, since we can point to it, and say 'that there doohickey's a black hole'
and since stars in our galactic core are orbiting it,
and, since if we get too close to it we get our asses kicked
I'd say it's about as physical as you can get.

Look, just because you don't understand it doesn't mean it doesn't exist.

 

[river]

Well, since we can point to it, and say 'that there doohickey's a black hole'
and since stars in our galactic core are orbiting it,
and, since if we get too close to it we get our asses kicked
I'd say it's about as physical as you can get.

Look, just because you don't understand it doesn't mean it doesn't exist

What of the galactic core in the first place ? Since ALL Galactic cores have a BH at their core.

Yet you can't tell me what this BH is physically based on .

 

[DaveC426913]

Since ALL Galactic cores have a BH at their core.

You have been told already that this is false.

Yet you can't tell me what this BH is physically based on .

Can and have.
The fact that you don't understand it - that's on you, not me.

 

[river]

river said: ↑
Since ALL Galactic cores have a BH at their core.

You have been told already that this is false.

Then the BH theory is false .

 

[DaveC426913]

Then the BH theory is false .

Don't be silly.

 

[Janus58]

Yet gravity waves emanate; not turn inwards upon themselves . If they did , turn inwards , the gravity wave would never exist .

Nonsense. You are confusing gravitational waves which carry information about changes in gravity, and the gravitational field. Gravitational waves cannot escape the event horizon of a black hole, But the gravitational field, which exists outside the BH was there before the BH formed and remains after the BH forms. The gravitational waves detected an were the result of BHs colliding were generated outside of the event horizons.

 

[river]

river said: ↑
Since ALL Galactic cores have a BH at their core.

Don't be silly.

What is silly about my last post ?

 

[river]

river said: ↑
Yet gravity waves emanate; not turn inwards upon themselves . If they did , turn inwards , the gravity wave would never exist .

Nonsense. You are confusing gravitational waves which carry information about changes in gravity, and the gravitational field. Gravitational waves cannot escape the event horizon of a black hole, But the gravitational field, which exists outside the BH was there before the BH formed and remains after the BH forms. The gravitational waves detected an were the result of BHs colliding were generated outside of the event horizons.

To your last statement ; how so ?

Why would BHs collide ?