zapatos

"Incredible animation shows just how big supermassive black holes can get"

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MGC 4889. Wow!.  You'd only fit 1 in our entire solar system.  :o  Makes you wonder what it fed on for 14 million years to get so big. Did it suck up any advanced civs or has it just spent it's time munching on developing star systems/solar systems. Did it start very big and stabilize or has it grown slowly or in spurts. I guess you could write a book in speculation as to how it came to be and what it ate. Is it possible to estimate or calculate the age of such a thing?

 

#feeingsmallandhumbled

 

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22 hours ago, DrP said:

Makes you wonder what it fed on for 14 million years to get so big

You mean 14 Billion years.

 

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1 hour ago, michel123456 said:

You mean 14 Billion years.

 

Yes I do.

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23 hours ago, DrP said:

MGC 4889. Wow!.  You'd only fit 1 in our entire solar system.  :o  Makes you wonder what it fed on for 14 million years to get so big. Did it suck up any advanced civs or has it just spent it's time munching on developing star systems/solar systems. Did it start very big and stabilize or has it grown slowly or in spurts. I guess you could write a book in speculation as to how it came to be and what it ate. Is it possible to estimate or calculate the age of such a thing?

Supermassive black holes are quite hard to explain! It isn't known if the black hole came before the galaxy, or was created from material in the galaxy, or they both developed at the same time.

There is a limit to how fast black holes can "feed" (because the heat generated by infalling matter blows away some of the material). Current models do not allow black holes to get to that sort of size by absorbing material. It is also hard to see how that much matter could get that closes well.

One plausible hypothesis is "direct collapse" where a large cloud of gas collapsed directly to form the black hole, instead of forming stars as it collapsed. But I don't know how well confirmed this is yet. In this model, I think the black hole becomes a seed for the later formation of the galaxy.

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39 minutes ago, Strange said:

Supermassive black holes are quite hard to explain! It isn't known if the black hole came before the galaxy, or was created from material in the galaxy, or they both developed at the same time.

There is a limit to how fast black holes can "feed" (because the heat generated by infalling matter blows away some of the material). Current models do not allow black holes to get to that sort of size by absorbing material. It is also hard to see how that much matter could get that closes well.

One plausible hypothesis is "direct collapse" where a large cloud of gas collapsed directly to form the black hole, instead of forming stars as it collapsed. But I don't know how well confirmed this is yet. In this model, I think the black hole becomes a seed for the later formation of the galaxy.

I was wondering where a black hole the size of our solar system would have picked up so much matter. (do they mean the physical part is the size of the solar system or that is where the event horizon extends to? I took it to mean the actual physical mass). The speculation that they might be involved in the formation of a galaxy would explain away the need for it to feed on so much matter - maybe they already kept their mass from the initial expansion of all matter from the beginning.  

How did the initial 'hot dense state' of the universe before expansion compare to the make up of black holes? Could it have been similar to one single giant black hole that was the entire universe before it was broken up during expansion? One super singularity.   (sorry for the wild speculation - I am not an astrophysicist).

 

 

 

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1 hour ago, DrP said:

I was wondering where a black hole the size of our solar system would have picked up so much matter. (do they mean the physical part is the size of the solar system or that is where the event horizon extends to? I took it to mean the actual physical mass).

It is the size of the event horizon (the radius is directly proportional to the mass). This is slightly larger than the one in M87 that was imaged recently by the Event Horizon Telescope.

1 hour ago, DrP said:

How did the initial 'hot dense state' of the universe before expansion compare to the make up of black holes? Could it have been similar to one single giant black hole that was the entire universe before it was broken up during expansion? One super singularity.  

In both cases, we don't know what happens (happened) in the ultimate condition. We know the early universe was uniformly hot and dense and if you keep extrapolating back you get infinities from the math (a singularity). Similarly, with black holes, when you use GR to predict what happens to the matter, you end up with a singularity.

I don't think anyone considers singularities to be physically realistic; they are just an indication that the math no longer makes sense.

However, there are two big differences between the universe and a black hole. A subtle one is that the singularity for the early universe is in the past while one for a black hole is in the future (the radial dimension of the black hole becomes time instead of space when you pass the event horizon).

A more significant difference is that a black hole is a concentration of mass at one place (our mathematical models of black holes actually describe an unchanging black hole in an otherwise empty universe; but this is a reasonable approximation to reality). The universe on the other hand has always been uniformly (approximately) full of matter. 

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2 hours ago, Strange said:

It is the size of the event horizon (the radius is directly proportional to the mass).

OK - that mental picture is way more manageable for my brain. lol  a BH whose actual singularity was the size of the solar system would probably have an EH larger than the universe, lol.  (It's OK - I know it doesn't really work like that - they are all the same 'size' - a singularity, whatever that is the size it is and is 'mathematically' considered an infinitely small point in space.).

 

2 hours ago, Strange said:

I don't think anyone considers singularities to be physically realistic; they are just an indication that the math no longer makes sense.

Speculation:-

I think it could make sense if the conditions inside the centre of the BH, the singularity, were such that all the collapsed matter is so compressed that every wave form from every subatomic particle chucks any exclusion laws out of the window and super impose themselves on each other into a single wavefunction for the whole mass. A bit like one giant collapsed super nucleus. A super giant single quantum entity made from the entire mass. I can envision 2 perspective states here - 

1 - where the mass of the collapsed nucleus would effect the actual physical diameter of the thing (I know mathematically it has no dimensions - it's a singularity) - we would still see it as a singularity but of course could only comment on its mass by the size of it's event horizon and it's gravitation effects on other bodies. The actual singularity would be about the size of a few atoms maybe and would change size slightly with mass although still look like a singularity from the maths.
2 - where not only the smallest quantization of subatomics are squished together, but, they actually superimpose on each other due to the extreme conditions into a single sub atomic quantum super particle/entity which would indeed appear as a singularity or as close as you can possibly imagine. The individual wave functions of each and every subatomic particle overlapping into a single entity the size of the smallest sub atomic particle but with immense mass. (like a Bose-Einstien condensate, although something different obviously that we haven't worked out yet  (because it's in a BH)).

 

I know none of this is testable. Reading it back it sounds awful - I know what I am trying to say but might not be getting it across very well (I've been ridiculed for the idea before....  but only I feel because none of this is testable).  A Bose-Einstien condensate is the condition at absolute zero. What about the absolute opposite? At 'infinite temperature pressure and smallest volume... maybe a different state occurs where exclusion laws no longer work on a much greater scale than at 0K.

Sorry - I'm waffling now.  Thoughts?  Mindless babble and speculation probably - none of it is testable or falsifiable right now. 

 

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1 minute ago, DrP said:

Sorry - I'm waffling now.  Thoughts?  Mindless babble and speculation probably - none of it is testable or falsifiable right now. 

Until we have a theory of quantum gravity, your guess is a s good as mine!

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I like the speculation based on case 2. If particles can coalesce into a single quantum state at absolute zero, seemingly defying exclusion laws/principles, then why can't something similar or yet to be discovered abnormally cause a similar overlap at the other extreme of temperature and pressure but on a greater scale?  I used to think the BH was like a giant neutron star... but I am starting to think the actual singularity could be possible with this super imposition of matter to a point the size of a sub atomic particle or some kind of super nucleus.

How will the quantum gravitation theory shed light on this? I still do not see how we can get any info our from behind the EH so whatever we come up with will be pure speculation without being able to do any actual measurements beyond the EH, no?

 

 

 

 

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I was at an observatory in my hometown and they said something that black holes can have the density of water or something all I know is that they related the two when they were trying to explain the scale of black holes and the like. what was that about I might have misheard but could you guys explain what that might be? (sorry if this is a split)

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34 minutes ago, peterwlocke said:

I was at an observatory in my hometown and they said something that black holes can have the density of water or something all I know is that they related the two when they were trying to explain the scale of black holes and the like. what was that about I might have misheard but could you guys explain what that might be? (sorry if this is a split)

The volume of a black hole increases proportionally to the cube of the mass so the density goes down as the square of the mass. So the bigger a black hole, the lower its density. So, yes, for a supermassive black hole the (average) density can be less than water.

(Note that density doesn't really mean anything because (a) we don't know how the matter is distributed inside the black hole and (b) the "volume" is not well defined: inside the black hole the radius is time!)

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19 minutes ago, Strange said:

inside the black hole the radius is time!)

I don't get it. Time is 1D, Space is 3D. So when you swap time with 1D of space (radius) you still retain unchanged the other 2D of space. So what happened really? Looks like nothing changed to me.

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7 minutes ago, michel123456 said:

I don't get it. Time is 1D, Space is 3D. So when you swap time with 1D of space (radius) you still retain unchanged the other 2D of space. So what happened really? Looks like nothing changed to me.

You can think of it as a rotation: as you get closer to the event horizon, the radial (spatial) dimension is increasingly swapped with the time dimension (hence time dilation). Inside the event horizon the centre of the black hole is now in your future. There are still three spatial dimensions, but one of them used to be time. I don't think anyone can really understand what that means in practical terms!

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On 5/17/2019 at 12:17 PM, Strange said:

The volume of a black hole increases proportionally to the cube of the mass so the density goes down as the square of the mass. So the bigger a black hole, the lower its density. So, yes, for a supermassive black hole the (average) density can be less than water.

(Note that density doesn't really mean anything because (a) we don't know how the matter is distributed inside the black hole and (b) the "volume" is not well defined: inside the black hole the radius is time!)

thanks for clearing that up.

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On ‎5‎/‎17‎/‎2019 at 8:17 PM, Strange said:

The volume of a black hole increases proportionally to the cube of the mass so the density goes down as the square of the mass. So the bigger a black hole, the lower its density. So, yes, for a supermassive black hole the (average) density can be less than water. 

(Note that density doesn't really mean anything because (a) we don't know how the matter is distributed inside the black hole and (b) the "volume" is not well defined: inside the black hole the radius is time!)

Although the parenthesis addresses this a little - how could you possible know the volume of a BH? Are you talking about the volume inside the EH again? Other wise it makes no sense to me - how do you measure/calculate/estimate the volume of the singularity inside a BH without knowing what it even is and being totally blind beyond the EH? Without knowing anything about the packing of matter in the singularity (which is what we were speculating about earlier) how can anything be speculated with regard to volume and density of it?

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20 minutes ago, DrP said:

Although the parenthesis addresses this a little - how could you possible know the volume of a BH? Are you talking about the volume inside the EH again?

Correct. This is the equivalent volume of a sphere with the Schwarzschild radius of the black hole.

 

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On ‎5‎/‎16‎/‎2019 at 3:31 PM, Strange said:

Until we have a theory of quantum gravity, your guess is a s good as mine!

How would that work?  Would we need an equation that defines the energy of a gravity wave or something? If we have detected a gravity wave then can we measure the energy of it (Like h.mu or something)? I expect that h might not have anything to do with it but if the energy of the wave can be defined then we can use know formulas for energy maybe to swap out E for mC2? Get an equation that relates mass to gravitational potential energy or something? idk - I am not making sense as I don't fully understand it, thus my question. How does a theory of quantum gravity help us define the substance and state of matter inside the singularity itself (or even speculate upon its nature)? 

 

 

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QM is mostly a mystery to me, but my understanding is that QM allows only discrete, and non-zero, 'sizes'. Hence for example an electron cannot appear halfway between two orbitals. Relativity on the other hand does not have this limitation and thus the unlikely possibility of a singularity. At the size of a singularity, Relativity is in conflict with QM. Hence the need for a Theory of Quantum Gravity in order to understand black holes. 

Hope someone corrects any misunderstanding I might have expressed here.

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43 minutes ago, zapatos said:

QM is mostly a mystery to me, but my understanding is that QM allows only discrete, and non-zero, 'sizes'.

For some things. Such as electric charge or energy levels in an atom. Other things (mass, length, etc) are not, as far as we know, quantised.

44 minutes ago, zapatos said:

Relativity on the other hand does not have this limitation and thus the unlikely possibility of a singularity. At the size of a singularity, Relativity is in conflict with QM. Hence the need for a Theory of Quantum Gravity in order to understand black holes.

Pretty much, yes. QM and GR are in conflict at all levels, but it only becomes significant at extreme conditions such as black holes and the early universe.

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