If A Primordial Black Hole Hits The Sun

[Persia]

If A Primordial Black Hole Hits The Sun...

...we should be able to see the oscillations generated by the collision, say astrophysicists

http://www.technologyreview.com/blog/arxiv/26839/?p1=Blogs

[danielost]

i dont think a black hole the size of an astroid hitting the sun, would cause any more ripples than an astroid hitting the sun. now after it hit the sun, it might feed off the sun and get bigger the event horizon of this type of black hole would be the size of the astroid before it became a black hole.

[Waspie_Dwarf]

i dont think a black hole the size of an astroid hitting the sun, would cause any more ripples than an astroid hitting the sun.

Firstly we are not talking about a black hole the SIZE of an asteroid, we are talking about one the MASS of an asteroid. Such an object would be microscopic (a black hole the mass of the Earth would be less than 2cm across). The sort of object this paper is discussing is atomic sized.

Secondly, whilst an asteroidal mass black hole could hit the sun (and as this paper suggests) travel straight through it, an asteroid would be vaporized by the intense heat long before it reached the surface. So what exactly is you mechanism for such an asteroid causing ripples on the sun Daniel?

This paper is based on a fundamental understanding of the principles involved and mathematical calculations. What is you conclusion based on?

[danielost]

Firstly we are not talking about a black hole the SIZE of an asteroid, we are talking about one the MASS of an asteroid. Such an object would be microscopic (a black hole the mass of the Earth would be less than 2cm across). The sort of object this paper is discussing is atomic sized.

Secondly, whilst an asteroidal mass black hole could hit the sun (and as this paper suggests) travel straight through it, an asteroid would be vaporized by the intense heat long before it reached the surface. So what exactly is you mechanism for such an asteroid causing ripples on the sun Daniel?

This paper is based on a fundamental understanding of the principles involved and mathematical calculations. What is you conclusion based on?

the gravity strength of the black hole is going to be the same as the astroid it came from, outside of its event horizon. this is the same for any black hole. if the sun became a black hole, the planets would all stay in the orbits they are in now. the only difference is we would no longer get the light.

besides didnt we just have a thread on an astroid that did in fact hit the sun and may have caused a mass explusion.

and i never said that the astroid would survive the impact.

as for an astroid causing ripples, ever heard of something called gravity.

[Waspie_Dwarf]

the gravity strength of the black hole is going to be the same as the astroid it came from, outside of its event horizon. this is the same for any black hole. if the sun became a black hole, the planets would all stay in the orbits they are in now. the only difference is we would no longer get the light.

Yes I understand that. Do you understand why this is not relevant in this case. I suspect not. Read on.

besides didnt we just have a thread on an astroid that did in fact hit the sun and may have caused a mass explusion.

No, we had a thread on a COMET which was destroyed by the sun at the same time as there was a CME. The very point of the thread was that there was no known connection between a comet and a CME.

and i never said that the astroid would survive the impact.

Really? You said:

would cause any more ripples than an astroid hitting the sun.

My emphasis.

Again you fail to understand a VERY simple point. There will be no impact. The asteroid will be destroyed before it can impact the sun.

as for an astroid causing ripples, ever heard of something called gravity.

I have. You do know that the gravitational field of an object is dependent on the density of that object, not just it's mass don't you? The gravitational field is dependent on the mass of the object and distance from the centre of that object...

Every planetary body (including the Earth) is surrounded by its own gravitational field, which exerts an attractive force on all objects. Assuming a spherically symmetrical planet (a reasonable approximation), the strength of this field at any given point is proportional to the planetary body's mass and inversely proportional to the square of the distance from the center of the body.

Read more...

This is why your example above is irrelevant... if the sun were to suddenly change into a black hole they planets would remain in the same orbit BECAUSE they are at the same distance. Hence the gravitational field afecting the planets will remain unchanged.

HOWEVER..

Let's assume that an asteroid can survive to hit the sun. The gravitational field at the surface of the asteroid will be fairly small in comparison to that of the black hole. The reason for this is that the surface of the asteroid is many miles from the centre, where as the surface of the black hole is less than an atom's diameter from it's centre. This means that they will act in very different ways. You could have worked out that the two objects would not behave the same with a very small amount of understanding and a very small amount of thought. After all you spend your entire life surviving an encounter with an Earth mass planet but do you really think you would survive an encounter with an Earth mass black hole?

Now that we've established that I have heard of gravity a question for you... have you ever heard of scientific method? Are you going to provide us with the data that lead you to your conclusion or are you just making another wild guess?

[danielost]

the gravity of an object is dependent on the mass, and the distance it is from another object. density doesnt matter.

saturn is much more massive than earth, but its density is less than that of water. ie it would float in a lake.

[Waspie_Dwarf]

the gravity of an object is dependent on the mass, and the distance it is from another object. density doesnt matter.

saturn is much more massive than earth, but its density is less than that of water. ie it would float in a lake.

What would the surface gravity of Saturn be if it had the same diameter as the Earth Daniel? Saturn has a mass 75 greater than the Earth, yet it's escape velocity at the surface is not 75 greater, it is only slightly more than 3 times greater. How is this possible if density doesn't matter?

Yet again you are in over your head and you are arguing basic stuff despite not understanding it.

If you back and actually read what I said you will find I said this...

Density matters AT THE SURFACE OF THE OBJECT. Since a black hole is much denser than an asteroid it's gravitational field AT IT'S SURFACE will be much greater. Since it will be the surface of the black hole which interacts with the surface of the sun should they collide this fact is very important. It is why the asteroid mass black hole would not behave in the same way as an asteroid.

I notice you have still provided no evidence to back up your claims that as asteroid will affect the sun in the same way as an asteroid mass black hole.

I asked if you had heard of scientific method... there is a little thing called BURDEN OF PROOF. Have you heard of that? It requires that anyone making claims have to provide the evidence to support those claims. It is why just guessing is about as unscientific as it is possible to be.

In science Daniel, opinion means nothing, evidence is king. In thread after thread you make claim after claim based on pure guess work (in most cases, like this one after not even having understood the initial post)... most of those guesses are easily proved wrong. I have never yet seen you provide any evidence to support your guesses. I have seen you claim that you are thinking "outside the box". Science allows you to think as much outside of the box as you like... AS LONG AS YOU HAVE EVIDENCE.

Where are your calculations? Where are your links? I'm waiting still.

[danielost]

i dont know if that is the cause of density or being closer to the source of gravity or both. but i did forget that a black hole is the extreme in density. i think that all black holes would have the same density, not the same mass. since they are all a singularity. super massive black holes have more mass due to them eating/merging with other black holes. besides outside the even horizen, the gravity of the black hole is no greater than it was for the object that became the black hole. be it a star, an astroid or an atom. unless of course it merges/eats other objects. that means of saturn was the same size as the earth, its gravity would still be the same. you would just be closer to the source of the gravity, ie the core.

and according to what i just read, if the sun were to become a black hole its event horizon would be about 3 meters. so going by that we wouldnt even notice an astroid sized black hole going through our own bodies.

i will see if i can find the link again.

Edited June 5, 2011 by danielost

[danielost]

But I digress. What if the Sun *did* become a black hole for some reason? The main effect is that it would get very dark and very cold around here. The Earth and the other planets would not get sucked into the black hole; they would keep on orbiting in exactly the same paths they follow right now. Why? Because the horizon of this black hole would be very small -- only about 3 kilometers -- and as we observed above, as long as you stay well outside the horizon, a black hole's gravity is no stronger than that of any other object of the same mass.

http://cosmology.berkeley.edu/Education/BHfaq.html#q6

sorry my mistake 3 kilometers. since this is from berkeley i think i will take their word for it.

[danielost]

What would the surface gravity of Saturn be if it had the same diameter as the Earth Daniel? Saturn has a mass 75 greater than the Earth, yet it's escape velocity at the surface is not 75 greater, it is only slightly more than 3 times greater. How is this possible if density doesn't matter?

Yet again you are in over your head and you are arguing basic stuff despite not understanding it.

If you back and actually read what I said you will find I said this...

Density matters AT THE SURFACE OF THE OBJECT. Since a black hole is much denser than an asteroid it's gravitational field AT IT'S SURFACE will be much greater. Since it will be the surface of the black hole which interacts with the surface of the sun should they collide this fact is very important. It is why the asteroid mass black hole would not behave in the same way as an asteroid.

I notice you have still provided no evidence to back up your claims that as asteroid will affect the sun in the same way as an asteroid mass black hole.

I asked if you had heard of scientific method... there is a little thing called BURDEN OF PROOF. Have you heard of that? It requires that anyone making claims have to provide the evidence to support those claims. It is why just guessing is about as unscientific as it is possible to be.

In science Daniel, opinion means nothing, evidence is king. In thread after thread you make claim after claim based on pure guess work (in most cases, like this one after not even having understood the initial post)... most of those guesses are easily proved wrong. I have never yet seen you provide any evidence to support your guesses. I have seen you claim that you are thinking "outside the box". Science allows you to think as much outside of the box as you like... AS LONG AS YOU HAVE EVIDENCE.

Where are your calculations? Where are your links? I'm waiting still.

you do know that surface gravity is determined by how close you are to the center of gravity and not the mass of the object. it is mass that determines an objects over all gravity. i

if you leave the surface of the earth, escape volicity is 7 mps. how ever if you start at the top of the atmo it drops down to about 6 mps. did the gravity of earth change no, did the mass of the earth change no. all that changed is you got further away from the center of gravity.

[Waspie_Dwarf]

but i did forget that a black hole is the extreme in density.

How could you forget that, it is the VERY definition of a black hole, an object so dense that it has an escape velocity greater than the speed of light. If you do not understand this then you understand nothing where black holes are concerned. Despite the fact that you are apparently clueless as to what a black hole is you are still going to give your opinion on them to the rest of us. Incredible!

i think that all black holes would have the same density, not the same mass. since they are all a singularity.

This would be right if all black holes had an infinity small (or zero) diameter. As it is they are increadibly small and so they will have a density approaching infinity. As you will see from the definition of density I give below density is dependent on mass. As long as black holes have a finite diameter (no matter how small) then they will have different densities.

that means of saturn was the same size as the earth, its gravity would still be the same. you would just be closer to the source of the gravity, ie the core.

WRONG!!!!!

What part of "at it's SURFACE" are you not getting? What part of "escape velocity" are you not getting? Once again you are totally confused by very basic science. Is that why you have totally failed to answer my question?

and according to what i just read, if the sun were to become a black hole its event horizon would be about 3 meters.

What part of "irrelevant" do you not understand?

so going by that we wouldnt even notice an astroid sized black hole going through our own bodies.

Are you seriously claiming that an object that has a mass of millions of tons and which can cause ripples on the surface of a star (you do remember the original article don't you) could pass through a human body and not be noticed? That is hilarious. I'd love to see you back that up with evidence (mind you I'd like to see you back up any of the drivel you post in the science section with evidence... but I doubt I'll live that long).

So we can add kinetic energy to the long list of basic scientific concepts that you don't know or don't understand.

The one time that mass IS the most important thing and you blow it. The kinetic energy of an object is defined as half mass x the square of the velocity. An object with a mass of 1,000,000,000,000,000 tonnes (the approximate mass of the objects being discussed in the original article) is going to be carrying a huge amount of energy. It may pass straight through you but the only reason you won't notice it is because you would be dead.

But I digress. What if the Sun *did* become a black hole for some reason? The main effect is that it would get very dark and very cold around here. The Earth and the other planets would not get sucked into the black hole; they would keep on orbiting in exactly the same paths they follow right now. Why? Because the horizon of this black hole would be very small -- only about 3 kilometers -- and as we observed above, as long as you stay well outside the horizon, a black hole's gravity is no stronger than that of any other object of the same mass.

http://cosmology.berkeley.edu/Education/BHfaq.html#q6

sorry my mistake 3 kilometers. since this is from berkeley i think i will take their word for it.

I never disputed this, I did tell you that it was irrelevant to the discussion and I explained why.

you do know that surface gravity is determined by how close you are to the center of gravity and not the mass of the object. it is mass that determines an objects over all gravity. i

if you leave the surface of the earth, escape volicity is 7 mps. how ever if you start at the top of the atmo it drops down to about 6 mps. did the gravity of earth change no, did the mass of the earth change no. all that changed is you got further away from the center of gravity.

Wow, you don't understand any of this do you? I repeat, what part of "at it's SURFACE" do you not understand?

You haven't even grasped the relationship between the mass and diameter of a body and it's density. This is very basic stuff. How can you argue the complex stuff if you don't understand the elementary stuff as taught to school children?

Let me explain density for you.

The mass density or density of a material is defined as its mass per unit volume.

Read more...

This means that the more compact it is the more dense it is.

Notice that density is dependent on volume. I assume you know that the volume of a spherical object, such as a planet, large asteroid or black hole is dependent on it's diameter.

Now let me explain why that determines the surface gravity of an object...

If an object is more dense then, for the same mass, it will have a smaller diameter. With me so far? If it has a smaller diameter then the surface of that object must, logically, be closer to the objects centre? Still with me. The one thing you have grasped is that the escape velocity increases the closer you get to the centre of the object. Therefore escape velocity will be higher on a denser object than on a less dense one. This is why you were wrong about Saturn. If Saturn were the same diameter as the Earth it would have an escape velocity 75 times greater than the Earth, not 3 times greater.

Now on to surface gravity.

The surface gravity, g, of an astronomical or other object is the gravitational acceleration experienced at its surface.

Read more...

The article goes on to say...

The surface gravity of a white dwarf is very high, and of a neutron star even more. The neutron star's compactness gives it a surface gravity of up to 7×10¹² m/s² with typical values of a few ×10¹² m/s² (that is more than 10¹¹ times of that of Earth). One measure of such immense gravity is the fact that neutron stars have an escape velocity of around 100,000 km/s, about 33% of the speed of light.

Read more...

So surface gravity is dependent on "compactness"...

compact ¹ (km-pkt, km-, kmpkt)

adj.

1. Closely and firmly united or packed together; dense

Read more...

So, having done what you have failed to do, presented evidence to back up my claims, it would seem that surface gravity IS dependent on density and your argument is quite simply wrong.

Science is not about guess work Daniel, it is about facts and evidence.

Edited June 5, 2011 by Waspie_Dwarf

[sepulchrave]

Kudos to you, Waspie_Dwarf, for trying.

------------------------------

Just to put things into perspective;

1 metre away from the surface of the Sun (mass = 1.989 x 10³⁰ kg, radius = 6.955 x 10⁸ m) and the acceleration due to gravity is about 28 g

1 metre away from the surface of the primordial black hole (mass = 10²¹ kg, radius = negligible) and the acceleration due to gravity is about 6 800 000 000 g.

1 metre away from the surface of an iron asteroid (mass = 10²¹ kg, radius = 672 000 m, based on the ambient density of iron at 787.4 kg/m³) and the acceleration due to gravity is about 0.015 g.

(I guess an iron asteroid might not be very realistic, but this is just an example.)

Look danielost, the mathematics isn't that complicated.

The equation is:

a = Gm / r

²

Here G = 6.674 x 10^-11 m³/kg/s² (Newton's gravitational constant), m is the mass of the object (in kg), and r is the distance away from the centre of that object (in m).

The answer is in m/s², if you want to convert it to g just divide by the acceleration of Earth's gravity (~9.81 m/s²).

So next time, please try to plug in some numbers and get an actual answer.

[Waspie_Dwarf]

Kudos to you, Waspie_Dwarf, for trying.

I don't do it for the sake of danielost, I suspect, where science is concerned, he is beyond help. Nor is my constant battle with him personal. I do it because I believe people are entitled to know what the facts are. As long as nonsense is posted in the science section I will do my best to highlight that nonsense and counter it with facts.

[danielost]

dwarf you are wrong, you do not increase the mass of an object when you increase it's density. gravity is a measure of mass not density. density is like a lens it focuses that gravity. you take a magnifing glass and let the sun go through it what do you get, i bright spot on the ground. if you take that same lense and use it to focus the suns ray what do you get a fire. now according to you because you focused the ray of the sun you have increased the heat from the sun.

Gravitation , or gravity, is a natural phenomenon by which physical bodies attract with a force proportional to their mass. In everyday life, gravitation is most familiar as the agent that gives weight to objects with mass and causes them to fall to the ground when dropped. Gravitation causes dispersed matter to coalesce, and coalesced matter to remain intact, thus accounting for the existence of the Earth, the Sun, and most of the macroscopic objects in the universe. Gravitation is responsible for keeping the Earth and the other planets in their orbits around the Sun; for keeping the Moon in its orbit around the Earth; for the formation of tides; for natural convection, by which fluid flow occurs under the influence of a density gradient and gravity; for heating the interiors of forming stars and planets to very high temperatures; and for various other phenomena observed on Earth.

http://en.wikipedia.org/wiki/Gravity

a black hole is just the ultimate focusing lens for gravity. it takes the mass and pulls it all down to a single point. this is why escape velocity is so great not because the gravity has increased.

now what i expect is going to happen is your going to tell me that you wont accept this because it came from wiki. but then you wouldn't accept it if it came from Berkley either would you.

your so focused on being right you cant admit when your wrong.

now if you had said you take saturn and increase its density to that of earth, then i would agree because you would need to add lots of mass to it. but you didnt all you did is take the same amount of mass and decrease its volume.

[sepulchrave]

dwarf you are wrong, you do not increase the mass of an object when you increase it's density.

Waspie_Dwarf is correct, his argument (and your original argument) was about surface gravity.

gravity is a measure of mass not density. density is like a lens it focuses that gravity.

Gravity is dependent upon mass and distance. If we are considering surface gravity, then it is better to talk about mass and density, since the distance is fixed (i.e. the distance from the core to the surface of the object).

This is amply demonstrated by the values I posted above, both the black hole and the asteroid have the same mass, but the black hole has a much smaller size (and correspondingly a much higher density). Hence the black hole's gravitational acceleration is some 11 orders of magnitude greater than the asteroid's just above the surface of each.

If you were 1 metre away from the core of the asteroid (i.e. inside the asteroid), the gravity would be almost negligible.

you take a magnifing glass and let the sun go through it what do you get, i bright spot on the ground. if you take that same lense and use it to focus the suns ray what do you get a fire. now according to you because you focused the ray of the sun you have increased the heat from the sun.

Yes you would increase the heat of the sun, at the point in question.

a black hole is just the ultimate focusing lens for gravity. it takes the mass and pulls it all down to a single point. this is why escape velocity is so great not because the gravity has increased.

How is the escape velocity greater if the gravity has not increased?

How do you measure the ``strength of gravity'' ? Magnitude of the force at a single point? Escape velocity? Volume integral of the field? Total energy of the field?

[Waspie_Dwarf]

now what i expect is going to happen is your going to tell me that you wont accept this because it came from wiki. but then you wouldn't accept it if it came from Berkley either would you.

I have no problem with the quotes you use danielost, it is your inability to interpret them correctly that is the problem. You are making claims about complex science without understand the basic, underlying principles.

Try to understand what sepulchrave is telling you here, you might actually learn some VERY basic science for once.

[Fluffybunny]

your so focused on being right you cant admit when your wrong.

If he was wrong, he would say so. Unfortunately you are wrong, but don't understand why and still think you are correct. You seem to not get the basics of physics, and in pushing so hard to be correct you are throwing out information that is wrong, or irrelevant.

Waspie knows what he is talking about. If you don't want to learn from him, then pay attention to the others here who are well schooled on the topic at hand. In every attempt you make to outshine Waspie, you just show how little you do actually understand of the topic.

Take the time and learn from the brilliant people we have around here, so you will understand what is going on, rather than fighting to be right even when you are not even close.

[Picturesque Orion]

the gravity strength of the black hole is going to be the same as the astroid it came from, outside of its event horizon. this is the same for any black hole. if the sun became a black hole, the planets would all stay in the orbits they are in now. the only difference is we would no longer get the light.

besides didnt we just have a thread on an astroid that did in fact hit the sun and may have caused a mass explusion.

and i never said that the astroid would survive the impact.

as for an astroid causing ripples, ever heard of something called gravity.

The bolded part is wrong I'm afraid. And a simple check on Newton's and Kepler's Laws of Universal Gravitation will demonstrate that. With an increase in density comes an increase in mass, an increase in gravitational force would proportionally increase the planet's orbital speed. This also relies on the orbital radius (Kepler'second law)along the orbital ellipse, but it doesn't apply here.

[sepulchrave]

The bolded part is wrong I'm afraid. And a simple check on Newton's and Kepler's Laws of Universal Gravitation will demonstrate that. With an increase in density comes an increase in mass, an increase in gravitational force would proportionally increase the planet's orbital speed. This also relies on the orbital radius (Kepler'second law)along the orbital ellipse, but it doesn't apply here.

Actually danielost is correct.

He is referring (please correct me if I misunderstood you, danielost) to a hypothetical situation where the Sun instantaneously collapses to a black hole, not to the situation where the Sun is replaced by a black hole whose Schwarzschild radius is the same as the radius of the Sun.

In danielost's scenario the mass of the Sun does not change, only the distribution of mass. So the orbits are unaffected.

[Picturesque Orion]

Actually danielost is correct.

He is referring (please correct me if I misunderstood you, danielost) to a hypothetical situation where the Sun instantaneously collapses to a black hole, not to the situation where the Sun is replaced by a black hole whose Schwarzschild radius is the same as the radius of the Sun.

In danielost's scenario the mass of the Sun does not change, only the distribution of mass. So the orbits are unaffected.

I see. Let's be grateful our dear Sol cannot collapse into an infinitely dense object shall we?

[sepulchrave]

I see. Let's be grateful our dear Sol cannot collapse into an infinitely dense object shall we?

Indeed. Every day I check the switchboard in my back room to make sure that the Pauli exclusion principle switch is set to ``on'' and the Coulomb repulsion dial is set to ``positive''. Can't be too safe...

[danielost]

Waspie_Dwarf is correct, his argument (and your original argument) was about surface gravity.

Gravity is dependent upon mass and distance. If we are considering surface gravity, then it is better to talk about mass and density, since the distance is fixed (i.e. the distance from the core to the surface of the object).

This is amply demonstrated by the values I posted above, both the black hole and the asteroid have the same mass, but the black hole has a much smaller size (and correspondingly a much higher density). Hence the black hole's gravitational acceleration is some 11 orders of magnitude greater than the asteroid's just above the surface of each.

If you were 1 metre away from the core of the asteroid (i.e. inside the asteroid), the gravity would be almost negligible.

Yes you would increase the heat of the sun, at the point in question.

How is the escape velocity greater if the gravity has not increased?

How do you measure the ``strength of gravity'' ? Magnitude of the force at a single point? Escape velocity? Volume integral of the field? Total energy of the field?

if you take a rubberband and pull on it, it will stretch so far. if you take that rubberband and fold it in half it will not stretch as far, if you double it again it will not stretch any further. now have you increased the strength of the rubber band yes. have you increased the number of rubberbands no. that is what happens when you pull mass into a high density body until you have a singularity. you are not increasing the amount of gravity, you are only increasing its strength.

the strength of gravity is dependent on its mass and density, the amount of gravity is dependent on mass alone.

i know this wont be accepted but here is a link]

http://answers.yahoo.com/question/index?qid=20090401075751AAUbY0Q

as i said it is how far from the center of gravity that determines its strength but not how much there is.

[Waspie_Dwarf]

the strength of gravity is dependent on its mass and density, the amount of gravity is dependent on mass alone.

BINGO. You finally accept that density IS important. You are beginning to put the pieces together and understand what has been said to you all along.

as i said it is how far from the center of gravity that determines its strength but not how much there is.

No one has ever disputed this.

If you go back and read what sepulchrave and I have been saying it actually relies on this fact. You have been arguing the wrong thing all along. And guess what the name of the strength of gravity at the surface is called... it's called surface gravity.

The surface gravity is dependent on density. The surface gravity is why you can walk on the Earth but would be ripped apart atom by atom on an Earth mass black hole. And the surface gravity is why an asteroid mass black hole would affect the sun in a totally different way to an asteroid if they collided. This was my whole point all along. QED.

[Leonardo]

Actually danielost is correct.

He is referring (please correct me if I misunderstood you, danielost) to a hypothetical situation where the Sun instantaneously collapses to a black hole, not to the situation where the Sun is replaced by a black hole whose Schwarzschild radius is the same as the radius of the Sun.

In danielost's scenario the mass of the Sun does not change, only the distribution of mass. So the orbits are unaffected.

I appreciate this is the popular theory, sepulchrave, but I question the conclusion [that the replacement of the Sun with a Sun-mass black hole would not affect the solar system dynamics].

The centre of mass of the solar system is not the centre of mass of the Sun. Any Sun-mass black hole would assume an orbit around that centre of mass [of the solar system], and the difference in mass distribution of a "black-hole solar system" would then come into play. Orbits would be affected, perhaps it might take a little time to detect, but the end result would be dramatic.

Edited June 9, 2011 by Leonardo

[sepulchrave]

I appreciate this is the popular theory, sepulchrave, but I question the conclusion [that the replacement of the Sun with a Sun-mass black hole would not affect the solar system dynamics].

The centre of mass of the solar system is not the centre of mass of the Sun. Any Sun-mass black hole would assume an orbit around that centre of mass [of the solar system], and the difference in mass distribution of a "black-hole solar system" would then come into play. Orbits would be affected, perhaps it might take a little time to detect, but the end result would be dramatic.

I don't think the centre of mass of the solar system matters, in this situation. The momentum of the "star-Sun" or "black hole-Sun" would be the same, so the dynamics of each in relation to the Solar system centre of mass would be the same.

As long as all the planets, comets, etc. stay far enough away from the "star-Sun" that it can be approximated as a sphere, or outside the event horizon of the "black hole-Sun", then both types of Sun have exactly the same gravitational influence.

Replacing a distributed mass (the "star-Sun") with an equivalent point mass (the "black hole-Sun") has no effect on the total centre of mass of the Solar system as long as the point is placed at the centre of mass of the previous distributed body.

The differences in kinetic-gravitational dynamics of the two Solar systems will only be different for the coments, asteriods, etc. that are on a collision course with the surface of the "star-Sun" (where obviously they would get absorbed by the "star-Sun"), but will miss the event horizon of the "black hole-Sun" and continue on in their orbits.

Of course you are right that eventually things will be different; but I think this would have more to do with the Solar wind, CMEs, magnetic field, heat output, etc. of the "star-Sun" that would be absent in the "black hole-Sun", and the above-mentioned comet and asteroid trajectories.