Why would a black hole grow in size???

originally posted by: Macenroe82
What's just as weird is that every single galaxy that we know of in observable space has a black hole in its centre.
So many "whys" out there.
I need me some "here's whys"

Smaller galaxies do not contain super massive black holes. Something about larger galaxies cause them to form. Basically milky way size and larger have them. This means they are caused by large galaxies. As to why we don't exactly know.

originally posted by: galadofwarthethird
a reply to: Golantrevize
Pictures or it does not exist.

Ah! Just messing, not expecting a picture of light. But a picture of this elusive fabric of space time would do.

Here this shows space time curves around massive objects.

www.nasa.gov...

originally posted by: Golantrevize
If the density is already infinite inside the eventhorizon then why would it get bigger in size by absorbing more matter? Also ive been reading about the bh in ngc 1277 that is the size of neptunes orbit and the mass of 17 billions suns and if a bh starts with the size of a city then how can it grow so much and why would it even grow if density is already infinite there is no reason to grow in size to accomodate more matter? Maybe i just dont get how bh work. Thx fir answering me

It depends on what you mean by 'gets bigger'.

If you mean the 3D physical size of the singularity, it may not get 'bigger' in 3D space terms, I'm not sure of the math on that point.

On the other hand, if you mean the mass of the singularity, then of course it gets more massive as material crosses the event horizon.

And the more massive the singularity, the larger in 3D physical size of the event horizon.

Since the 'black hole' is not 'just' the singularity, but the whole system of singularity, event horizen, and transition space (my term) in between, it should be fairly clear why it gets 'bigger'.

On the other hand, if new material crossing the event horizon is less massive than the Hawking Radiation, the black hole will evaporate (perhaps more accurately: sublime) away and get smaller over time.

originally posted by: Golantrevize
If the density is already infinite inside the eventhorizon then why would it get bigger in size by absorbing more matter? Also ive been reading about the bh in ngc 1277 that is the size of neptunes orbit and the mass of 17 billions suns and if a bh starts with the size of a city then how can it grow so much and why would it even grow if density is already infinite there is no reason to grow in size to accomodate more matter? Maybe i just dont get how bh work. Thx fir answering me

Firstly, the infinite density is "inside" the singularity, not the whole of the black hole.

What gets bigger is the event horizon radius, which is linked to how much mass the black hole has. Even horizon is the volume around the singularity where curvature of space-time is so strong that the escape velocity there equals to speed of light, meaning nothing (not even light) can escape from below the event horizon.

The curvature of spacetime (which we perceive as gravity) is caused by mass. The more mass, the stronger the curvature. As the black hole gains mass from in-falling material, it distorts the space-time around itself more and more, which means that the radius where this distortion creates an event horizon becomes larger.

I hope that explains it to you

The key thing to remember is that black holes are not objects like stars or planets are. They are simply places in space where space-time is curved so much that nothing can escape it. I guess you could say that the singularity at the centre of each black hole is the object, since it has mass. The rest of the black hole is just curved space-time.

Supermassive black holes may gobble up stellar black holes and primordial black holes ?
Stellar black holes may consume primordial black holes of which there may be many many in every galaxy ?
This may add to the event horizon circumference expanding ?

www.nasa.gov...

Primordial black holes have been linked to Dark matter ? They also could be linked to dark energy ?

Dark matter is a mysterious substance composing most of the material universe, now widely thought to be some form of massive exotic particle. An intriguing alternative view is that dark matter is made of black holes formed during the first second of our universe's existence, known as primordial black holes. Now a scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, suggests that this interpretation aligns with our knowledge of cosmic infrared and X-ray background glows and may explain the unexpectedly high masses of merging black holes detected last year 2015.

www.nasa.gov...

en.wikipedia.org...

www.sciencedirect.com... ( DEEP : Summary below ))

Summary and discussion: The detection by aLIGO of gravitational waves emitted by the merging of two massive BHs opens a new way to probe the abundance, the clustering and the mass distribution of PBHs. The merging rates expected for various local densities and mass distributions have been calculated and compared to the bounds 2–400 Gpc−3 yr−1 inferred by aLIGO, in the case PBHs have the right abundance for being the dark matter. A uniform distribution of PBHs inside galactic halos cannot reproduce such high rates. But we find that if PBHs are clustered in sub-halos with densities comparable to the one of DM-dominated ultra-faint dwarf galaxies, the merging rate lies precisely within that range. We suggest a model where PBHs are massive – a few tens of solar masses – and have a broad mass spectrum, like the one generated by hybrid inflation with a mild waterfall phase [10], such that a subdominant number of very massive PBHs can be the seeds of the SMBH at the center of galaxies, as well as of the IMBHs expected to be at the origin of ultra-luminous X-ray sources. Such a PBH–DM model would have interesting observational consequences and could solve the long-standing missing satellite and too-big-to-fail problems of CDM cosmology. Finally, by studying the merging rates with different progenitor masses in the range , we find that the detection of thousands of merging events by LIGO, VIRGO and future GW detectors like KAGRA, would allow the reconstruction the PBH mass

a reply to: skywatcher44

That's a great post and a great video, thanks. I didn't know about primordial black holes.

Yes, there are many cases when black holes swallow other black holes or simply merge together. This always results in one bigger black hole.

A black hole is like the Blob; throwing anything at it will just make it bigger.

originally posted by: Gothmog

originally posted by: intrptr
a reply to: Gothmog

No dimension has mass nor energy.

Did you just say, 'Nothing has nothing'?

Or put another way, nothing means nothing.

Welcome to the new science, anything goes...

As stated - No dimension has mass or energy. Mass and energy exist in all dimensions. And maybe "outside" any dimension at all.

Outside is still a side. Still a part of the whole.

All the multiverses exist altogether in one place, the Universe.

I tend to see a whole, not divided. We are conditioned to divisiveness, beginnings and endings. Those don't exist, except n our minds.

Black holes have to do with escape velocity of light. They are not infinitely dense. No matter the size of the black hole, once the escape velocity exceeds the speed of light, it becomes a black hole. The more matter that falls below that horizon, the large the black hole becomes. But with such high gravity, they would grow very slowly.

Recent ScienceNews article..

Astronomers can’t figure out why some black holes got so big so fast..

The existence of supermassive black holes in the early universe has never made much sense to astronomers. Sightings since 2006 have shown that gargantuan monsters with masses of at least a billion suns were already in place when the universe was less than a billion years old – far too early for them to have formed by conventional means. One or two of these old massive objects could be dismissed as freaks, says theoretical astrophysicist Priyamvada Natarajan of Yale University. But to date, astronomers have spotted more than 100 supermassive black holes that existed before the universe was 950 million years old. “They’re too numerous to be freaks now,” she says. “You have to have a natural explanation for how these things came to be.” The usual hypotheses are that these black holes were either born unexpectedly big, or grew up fast. But recent finds are challenging even those theories and may force astronomers to rethink how these black holes grow. In the modern universe, black holes typically form from massive stars that collapse under their own gravity at the ends of their lives. They usually start out smaller than 100 solar masses and can grow either by merging with another black hole (SN: 3/19/16, p. 10) or by accreting gas from their environment (SN Online: 12/6/17).

www.sciencenews.org...

www.sciencenews.org... ( Pairing BH )


www.sciencenews.org... ( Accreting Quazar )

Of i remember correctly, the density would be infinite within the singularity, the event horizon is just the point of no return. Remember that everything we believe about black holes is all theory
y /speculation and down right guessing. Physics/quantum theory and even good old common sense stop existing when talking about black holes.
Now, to the question....I have no idea. I do find all the extremes of the universe fascinating. Magnatars, quasars, supernovas...It goes on and on. A black hole the size of Jupiter's orbit?!? Seems impossible. I think black hole's purposes is to ever do slowly, collect all of the universe's matter and recycle into the next big bang or whatever starts it off all over again. Sucks to think how little we will understand about everything in our lifetime.

a reply to: Hr2burn

The infinite density of the singularity comes from the math breaking down with infinities.
We don't know what happens inside a black hole.
That is why scientists are trying to get Quantum Physics and General Relativity to play together.

First, we don’t know what gravity is. Oh, Newton, Einstein, Feynman, Hawking, Susskind, et. al., can describe the effects of gravity. If you know, F = ma, then you know as much as everyone else!

Neutron stars made the news last year. They are still arguing about them because they are a quantum object. BH are even more strange! Nobody knows how quantum gravity works or even how it might work (a lot of ink has been spilt over it! A lot more to come!!).

You won the internet with your question! But that is science for you.

Here is my “crystal ball” thought. Every great leap in physics includes a “new” math idea. Watch math and think of how it affects physics.

That is as good as I can do for an answer. Lame, but honest.

Stay curious! Keep watching the skis!

a reply to: TheMadTitan

First off infinity is not a real number. It's just something people came up with to help us comprehend extremely large or small numbers.

In terms of density, I would imagine infinite density to mean that all the particles are squashed together so tight that there is NO empty space at all. For example, lets take a bag of M&M's. Most of the bag is filled with air or empty space...the same with atoms. If we melted all of the M&M's in the bag and managed to get it to cool down with no air pockets in it that would be like "infinite density" in the black hole. It would be much smaller than the bag of M&M's originally was because the bag was mostly empty space.

So, if you can imagine all the matter in the black hole with no empty space (meaning all the particles that make up matter were packed in so tightly together that there was no empty space at even at the smallest scale. This would be 100% density. NOW, let's add more matter to that. Where is the matter going to go? If there was truly no empty space at all, and you add more matter, or course the black hole would have to get bigger. There is no room anywhere else for the matter to go.

You can only fit so many M&M's in a bag...even if you melted them together to get rid of all the empty space in the bag. Once that bag is full, if you add in more M&M's, you will need a bigger bag.

a reply to: dumpaling

Nah. The idea is that a singularity has no radius, no volume. So, to derive mass one would be dividing a number (mass) by 0 (volume).

That's not allowed. The result is undefined. That is not the same as infinite. Nor does it have much to do with the radius of the event horizon, which does get larger as more mass is added to the singularity.

a reply to: TEOTWAWKIAIFF

I'd like to add that General Relativity is really a classical theory just like Newton's description of gravity.
General Relativity assumes a smooth space-time like Newton's.

I assume one day space-time will be successfully quantized and will then play nice with Quantum Mechanics.

It's strange to call Einstein's General Relativity classical but it really is.

originally posted by: Golantrevize
If the density is already infinite inside the eventhorizon then why would it get bigger in size by absorbing more matter? Also ive been reading about the bh in ngc 1277 that is the size of neptunes orbit and the mass of 17 billions suns and if a bh starts with the size of a city then how can it grow so much and why would it even grow if density is already infinite there is no reason to grow in size to accomodate more matter? Maybe i just dont get how bh work. Thx fir answering me

perhaps a black hole isn't a hole at all.

opinion:
it is a solid. a dense object with an incredible amount of gravitational pull. so as the solid attracts more items to it, it grows.

a reply to: Phage

You are correct and I correct myself saying the math had infinities.
I should know better.

I should have said the solutions to the math are undefined inside a black hole.

a reply to: Phage

Or else they need more than 62 digits of Pi?
Not that you could prove that in a lab though.

a reply to: dumpaling

Infinity is both real and useful!

Without it we would not have calculus which leads us to these conundrums!

The answers don’t make sense because, as I stated previously, our maths are not complete. It is changing as they are being put a “periodic table” of sorts. And we are seeing connections between disparate fields in math!

Which is why I finally answered with a meaningful answer as all the other stuff had already been stated!

a reply to: Deluxe

I swing the other way!

I have a feeling that Riemann will point the way to the discrete... uh... emerging (???)... from the complex number plane. Then it will apply to other problems involving both continuous and real working with the discrete.

Changes over time, wave function, and prime numbers (which are infinite! lol), all seem to be connected somehow.