The Biggest Possible Black Hole - Sixty Symbols

[@sixtysymbols]

A Brief History of Black Holes by Becky Smethurst... (Amazon links)... US: amzn.to/3u0b4BN and UK: amzn.to/3VxlNPV

[@a.randomjack6661]

You should pin your comment📌so it stays at the top.

[@Globovoyeur]

My copy is on order...

[@mussalo]

Can one get it from anywhere else than Amazon? From EU preferably.

[@juliocardenas4485]

Purchased 👍🏾

[@bentoth9555]

Don't have the free funds to purchase it myself, but I definitely suggested my local library do so.

[@N.I.R.A.T.I.A.S.]

I feel like Dr Becky's ability to freehand draw a black hole and accretion disk is more impressive than I realise.

[@sixtysymbols]

I too was impressed.

[@QirnsChannel]

@@sixtysymbols I appreciate that you ask folks to draw things so often. Math and Science need more drawings! Even when it's just a drawing of a mouse.

[@lukaskern9163]

@@QirnsChannel WORST - MOUSE - EVER!! x'D

[@EPMTUNES]

Anything for the merch

[@88CBAUGH]

10:58 for your viewing pleasure.

[@Booster45]

Dr Becky is back on sixty symbols!

[@Felipehez]

Thanks Brady for keeping this channel alive for so many years! I love your videos and dr Becky!

[@WouterWeggelaar]

I am in love with Becky's enthusiasm and I will absolutely be getting the book!

[@sixtysymbols]

Nice work - hope you enjoy it!

[@writingfriction]

Forget the book- I'm in love with Dr Becky.

[@vzr314]

@@writingfriction welcome to the club mate

[@cynomyS]

@@writingfriction get in line

[@samcooke343]

@@writingfriction You're all too late, sorry 😏

[@julyanjohns1237]

this vid makes me happy on so many levels A black hole expert discussing the subject of their latest book with a renowned science documentary maker, or from a regular's perspective - Becky and Brody having a wholesome catch up :) inspiring to see how a simple idea over ten years ago of doing vids of professors talking about symbols has had so many positive knock on effects for the people involved with it.

[@TON-ei7ht]

I’ve worked so hard to be featured on this channel. It’s about time!

[@gqqggq7127]

Nothing escapes you!

[@stevenhanaway920]

Glad to finally see a video about TON 618! I imaged this with my astrophotography rig/observatory a few years ago, as there aren't many full, true color images of this quasar, especially taken by amateurs/citizen scientists like myself. I wish I had a spectrometer to measure the red/blue shift of objects like this, perhaps one day I will be able to buy or build one. Clear Skies!

[@ogexo]

Phoenix a is bigger

[@ScienceAsylum]

Thanks for the self-gravitational radius info! Looks like I'll be running some new black hole simulations soon.

[@realspacemodels]

Dr. Becky's book is amazing. I got the audiobook, so hours of hearing her talk to you. It's great!

[@kidmohair8151]

I'll add to Dr Becky's thank-you by also thanking you for bringing us *all* the other wonderful scientists from U Nott to youtube! You, sir *are* a gentleman *and* a scholar!

[@artemkras]

Sixty Symbols is where I first saw Dr. Becky a long time ago.

[@S1nwar]

what people often dont realize is that you couldnt even look at a black hole if you're anywhere near it because the accretion disc is brighter than any star could ever be since the heat production from THAT gravitational pull outscales the energy output of any kind of fusion process

[@WylliamJudd]

WOW!

[@nocare]

Well ton 618 in particular. It outshines every star in the milky way combined many times over. Its 160 trillion times brighter than the sun.

[@bierrollerful]

Sounds like the ultimate boss fight for redheads.

[@nocare]

@Josh Smith that is not true. Black holes have been demonstrated in multiple ways. Includeing 2 direct imagines. The part that is almost certainly not real is a singularity since those are infinitely dense and a quirk of the math. Many if not most physicists believe that singularities will disappear once we have a theory of quantum gravity. Also you used theory wrong. In a scientific context theories are proven and well substantiated. Hypothesis is what you wanted.

[@AureliusEnterprises]

@Josh Smith That's not true at all, there is overwhelming scientific evidence for black holes. They recently made a picture of two of them and prior to that they had stars orbiting what seemed to be 'nothing'. They have data of the gravitational waves of two black holes merging.

[@pr0hobo]

I wish they explained why the self gravitational radius doesn’t grow or doesn’t grow as fast as the isco.

[@garethdean6382]

The SGO depends in part on the 'gravity gradient' across an object, the tidal forces. Just as Jupiter prevented a planet forming between it and Mars, a black hole can stop 'clumping' of its disk. While the ISCO grows directly with the hole's mass (Twice as heavy, twice as large, relating directly to the strength of gravity at a distance from the hole) the SGO for an object of a certain size rises with the mass of the hole to the 1/3 power. (Relying on the DIFFERENCE between the strength of gravity at either side of the object.) One is just more directly related to the hole's mass and gravity.

[@bluzedogg]

This is easily one of the best science videos I've ever seen on KZbin. Dr. Smethurst you are awesome.

[@artdonovandesign]

Great interview! Thank you, Dr. Becky.

[@TheDirge69]

Thank you Brady for giving Dr Becky her start on KZbin, from all of us..

[@mikmop]

I love all Brady's video channels and I use to love watching Becky on Sixty Symbols before she started her own channel. I was hoping she would do that because I would go out of my way to watch her appearances. Anyway, glad to see her back doing a cameo on this channel again and that dedication in her book to Brady I thought was just beautiful.

[@adamwulf]

I’m curious if hawking radiation would eventually cause these max-sized black holes to shrink small enough to begin accreting again. If so, does that mean the black holes would all hover around that max size, growing to it but no further, and not shrinking much smaller because they’d grow up again

[@danilooliveira6580]

hawking radiation is very, VERY week, it would take a unimaginable amount of time for a blackhole to noticeably shrink through this process. it would probably grow more through eating rogue material flying at it than it would lose mass through hawking radiation. I would hazard to argue that light, neutrinos and other high energy particle hitting the blackhole from all directions would give it more mass than it would lose, but that is just speculation from my part.

[@jackhand4073]

I could be wrong but by the time hawking radiation is a problem, matter and inturn accretion won't be. The time scales are ridiculous. Can someone let me know if my thinking is wrong?

[@prdoyle]

@@jackhand4073 Hawking radiation takes on the order of a googol years to evaporate a big black hole. It could be the slowest process in the universe.

[@adamwulf]

@YeYaTeTeTe Very interesting! Thanks for the calculations - mind boggling time scales indeed!

[@TechSY730]

The rate that Hawking radiation loses energy ("temperature" so to speak) is _inversely_ proportional to mass* Meaning more massive black holes will lose mass _slower_ . In addition to having more mass to lose. In fact, cubically so (how long it takes to fully evaporate is proportional to the mass cubed) * for black holes at least, but this effect is a property of event horizons in general. See Unruh effect for another event horizon caused by acceleration of a reference frame.

[@bierrollerful]

"Thanks for giving me my start on youtube." That's so sweet. And true. Thanks Sixty Symbols for introducing us to such bright minds.

[@rarelycomments]

Genuinely disappointed that it wasn't called the Disc (of) Innermost Stable Circular Orbits. Disco.

[@AsmodeusMictian]

Always awesome to hear about black holes. Thanks for the amazing video!

[@michaelpettersson4919]

I see Dr. Becky, I click. Only after starting the video did I realise that this isn't her channel.

[@christiananderson6761]

Love Dr. Becky and her enthusiasm

[@dpie4859]

We all love Becky! ❤

[@BleuSquid]

I was so confused to hear Brady's voice at the start. I though this was a Dr. Becky video when I clicked on it! Love you both!

[@mighty8357]

She is just so cheerfull and passionate about her field :)

[@DouwedeJong]

Probably the best video I have seen from Dr. Becky.

[@thisistopsy]

Heyyyy. This is a very fascinating topic. Thank you for covering this! By the way, we actually found a much bigger black hole. It is the black hole of Phoenix A, the central galaxy of the Phoenix Cluster. It is presumed to have 100 billion solar masses, vs. TON 618's 66 billion. It was inferred based on the properties of the galaxy Phoenix A (its Sérsic profile, a very complicated topic). But what excites me the most is that the James Webb Space Telescope, our favorite space telescope, is scheduled to observe the Phoenix Cluster and the galaxy Phoenix A specifically by July 29-31, 2023. They will not go for the black hole specifically, but they will try to uncover the mystery of the Phoenix Cluster's cooling flow. This is actually a very mysterious topic that we only knew of recently, and the Phoenix Cluster is the quintessential case. Its cooling flow is the strongest we ever observed. A brief summary: cooling flow is when the gases in the very center of the galaxy cluster cools very rapidly, and since cold gas collapses and has no radiation, the outlying gas surrounding the cluster, which is hotter, will come crashing down and "flow" towards the cooler gas at the center. We actually knew very little of why this happens, but it is presumed that the central black hole has got something to do with it. Black holes produce a lot of radiation through their accretion disks, thereby heating the gas around them. So I presume it would be obligatory for JWST to take a closer look at Phoenix A's monster black hole. And more importantly, it may help us understand galaxy clusters and how they work, since cooling flow is considered a feature of a short but very significant phase of a galaxy cluster's evolutionary stage.

[@edwardp7725]

How can you not love Dr. Becky?

[@Triantalex]

??

[@jacobopstad5483]

I asked this very question on a Dr. Becky video a while back. I'm so glad to get an answer!

[@TheInselaffen]

Dr Becky and Dr Brady, a collab of such joy.

[@Exoil]

Awesome, I just looked at saw that my audio book provider have Beckys book. I've been looking for something to listen to for a while now!

[@alsmith20000]

I didn't understand why the Innermost Stable Circular Orbit being the same size or larger than the Self Gravitational Radius would stop accretion. I assume the latter is basically an interpretation of the Roche limit and the typical sizes of stars? It sounded like a star would disintegrate when approaching a black hole, but its material could still orbit the black hole in a stable way, somewhat further in. If the ISCO was larger than the SGR, wouldn't that just mean that stars are doomed to fall in before they are torn apart?

[@Macieks300]

From what I understood if the ISCO is larger than the SGR then the only thing you can have orbiting the black hole is "clumps" which are probably mostly stars. That means that you can't have the accretion disc because all the stuff orbiting would always start clumping together.

[@caconym358]

I had the same question. IIUC, in a "normal" black hole friction within the accretion disk is responsible for sapping the orbital energy of accreting particles until they hit the ISCO and spiral in. If the theoretical outer boundary of the accretion disk is inside the ISCO, the black hole has no mechanism for reducing the orbits of objects that might otherwise join its accretion disk, and highly elliptical/hyperbolic orbits may even skim within the ISCO without being trapped since they have a lot of excess energy? So you're left with the only ways for an object to enter the black hole being the sort of "bulls-eye" Dr. Becky mentioned, where I guess you'd need a closest approach somewhere between the event horizon and the ISCO depending on the orbital energy of the object, and objects that independently place themselves in circular orbits at or within the ISCO, which don't occur in nature AFAIK. Intuitively it feels like a black hole that massive wouldn't *need* an accretion disk to pull in matter-it could just sweep through space like a giant eraser-but the effect this video's talking about may come down to the fact that a hypermassive black hole doesn't have a proportionally hypermassive accretion disk to pull in matter, so its growth is slowed to what's effectively a stop *relative to its size*. All speculation. :)

[@garethdean6382]

If the ISCO is too large then clumps of matter (Stars, clusters...) will be stable. At that point 'friction' between clumps becomes negligible, in the way that it's very rare for two stars in our galaxy to interact. Compared with an accretion disk where its glow is a direct energy loss, this drastically cuts down the amount of material falling to the center in the same way our sun is not swallowing planets on a regular basis.

[@jip5889]

The thing to keep in mind is that all that mass is concentrated in a point in the center, an infinitely small point. I think we intiuitively mistake the event horizon circle as having the mass evenly spread which is not the case. This is why we get these three other outer circles, EH, ISCO and SGR.

[@B-System]

@@jip5889 That's what I was missing. Thanks.

[@coopergates9680]

Great stuff. Note that black holes too massive for accretion disks are large enough to intercept vast amounts of radiation, whether light or otherwise, so they will keep growing even if they don't swallow bulk matter.

[@RedRocket4000]

Yep they finally large enough to hit a lot of stuff. Smaller black holes fairly tiny targets.

[@dreadnought1109]

There are two statements in this video that didn't feel right and when I looked them up seem to be way off. Anyone know if I am just not seeing the data right or if it was just misspoken? "Bigger than the mass over everything in the entire milky way..." Ton: 66b solar mass; Milky Way: ~1.2t solar mass. Wiki says bigger than the mass of the *stars* of the milky way so I can see that difference and where the confusion may be. "crushed down into a space smaller than the solar system" Again Ton 618: 390b km; Solar System: 26b km (Heliopause) So it looks like Ton 618 is bigger than the solar system even at the most generous size. I couldn't find a definition that makes this work.

[@GodwynDi]

90% of that mass is dark matter. Which may or may not exist

[@garethdean6382]

Yes. The statement is one of those factoids that gets repeated a lot because it sounds impressive and simple. In truth TON 618 is about as massive as all the stars of the milky way, compressed into an object with a volume less than the Kuiper Belt. It's roughly true but falls apart on analysis.

[@Worldwave]

yaaaaay Becky on one of Brady's videos! Two of my favorite KZbinrs!

[@GGoAwayy]

0:10 Woah! What are these totally obscure pop culture references?

[@RobinWildlife]

Dr. Smethurst is awesome!

[@rickseiden1]

Great Video. Bonus Dr. Becky!

[@Geezimac]

Nice to see you back on sixty symbols… for a minute I thought YT dumped an old video in my feed.

[@Droopy95mkDS]

Yaaay Beckyyy ! One of the greatest physics doctor on KZbin (like Dr. Don Lincoln from Fermilab both are amazing imo)

[@uncertainukelele]

This video was awesome, but thanks for the book plug as well, I didn't know about it.

[@___Kelli___]

Very interesting, thank you for making a video on this subject.

[@fliesbyme]

Once again Becky. Great video. Absolutely fascinating.

[@pwhite2579]

ordered your hardcover book by Amazon. It is not available in the states at Barnes and Noble (a week ago). Can't wait to read it!

[@themaverickproject4577]

I liked that video a lot. A nice conversation with Becky. Please think about doing more.

[@bradwood556]

DR Becky is so awesome!

[@Neloish]

Dr. Becky is the best.

[@judychurley6623]

Takes me back! I used to sign my photo students' yearbooks with a drawing of a camera!

[@cryptic_daemon_]

I really like Dr Becky, she should make her own youtube channel!!

[@potterma63]

Funny I find this video today. I was just reading the chapter about ultramassive black holes last night!

[@piratecheese13]

Becky is my favorite place to get deep space picture news

[@wixom01]

Oh, wow, I hadn't heard of this new book. Thumbs up for the video so that I can now go get my Kindle version!

[@travelservices1200]

It's an excellent book, I certainly recommend it.

[@stephaniejean2426]

Hey friends I'm new here but wow I'm impressed... This channel seems a bit like Numberphile but with physics instead of maths. 💯💜

[@MyNameIsNotCraig]

Really really interesting video. Thank you!

[@danielross7983]

5:54 Why does the self gravitational radius not increase in radius as the black hole grows?

[@BreakerBinge]

Just got your book on audible😁

[@richard8176]

Is there a theoretical maximum size for a star? If there is what is it, and what would be its radius?

[@HutchCA]

Doesn't Hawking radiation cause black holes evaporate faster as they grow bigger? Edit: My mistake, they evaporate slower as they grow.

[@jb76489]

1:13 is that true? I thought the Milky Way was on the order of 1E12 solar masses

[@TheTyme99]

I believe this estimation includes dark matter. In terms of normal matter it would be significantly smaller.

[@jb76489]

@@TheTyme99 seems rather disingenuous to exclude the stuff that makes up the vast majority of the milky ways mass when talking about the milky ways masss

[@GodwynDi]

@@jb76489 Because it still isn't proven.

[@jb76489]

@@GodwynDi what exactly? That the majority of mass in our galaxy doesn’t interact with light?

[@garethdean6382]

It's roughly true, when considering all visible mass in the milky way. Which makes it one of those facts that gets repeated (Like the fact that you need a light year of lead to have half a chance of stopping a neutrino.) It sounds impressive but is factually dubious.

[@olivermechling7975]

love this channel

[@MasterHigure]

I feel the need to correct the graphics at 3:00: On an image of a black hole, the circular black shadow (which is all we can see of the actual hole) is the limit for which light can come from elsewhere towards the black hole, get close to the black hole, and then get back out to us. The boundary of that sphere is about twice as far out from the center as the actual event horizon. The event horizon is the boundary for where a person can shine a light at us and we can see it. The black shadow is the boundary for where in addition, this person can at the same time shine a light in the exact opposite direction, and that light can escape the black hole. Alternately, the black shadow fills the region of your field of vision where if you shine a light in that direction, the light eventually ends up inside the black hole. It is not difficult to imagine that this lies strictly outside the event horizon, and if I recall correctly, it is a pretty standard calculation (for anyone familiar with the Schwarzschild metric) to find the actual radius. But it has been a decade since I did that math myself, so I don't remember the details.

[@GeoffryGifari]

another thing about black hole size, is there a size distribution? where most supermassive black holes should have radius R, some larger but many smaller, things like that?

[@tugbacnarl6060]

This is like a avengers movie❤❤❤ I love and learn a lot from Dr Becky’s content😎😎

[@MauroMarzorati]

Hmm, if the suggestion made @7:58 is accurate, would that phenomenon not also explain the "unaccounted for" matter in our models?

[@atlantic_love]

She's burning up astronomy. ❤‍🔥❤‍🔥❤‍🔥❤‍🔥❤‍🔥

[@dewaard3301]

Man, just in time for the Christmas gift season too!

[@djscottdog1]

This is actually a pretty basic idea if you double your size and gravity the diameter of your closest stable orbit doesnt double because of the inverse square law. It doesnt take twice the distance for the gravity to tail off

[@LMarti13]

When you ask "Is there an upper limit to the mass of a black hole" you go on to answer the question assuming a NATURAL black hole. But what if some hyper-advanced civilization decided to park a sphere of unimaginable mass outside the accretion disk and then launch all of it, all at once, at the speed of light, into the black hole? Surely that would increase the mass higher than the "limit" you describe? I think it's important to distinguish between physical limits and stochastic limits.

[@4623620]

Just a thought that came to my mind: if there is a limit to the maximum mass of a black hole, what happens when two black holes, with a combined mass greater than that limit, collide ?

[@mrfurieux9587]

the limit is not a hard limit, it's just a limit for acquiring mass "easily" via an accretion disk. The thing can still grow via other means

[@4623620]

@@mrfurieux9587 Thanks for your reply, but it still leaves the question, does anything special happens when the mass goes beyond this limit ? Also, if it is no "hard" limit, it seems that a title like "The Biggest Possible" is a bit misleading.

[@mrfurieux9587]

@@4623620 apparently nothing special happens, except that the hole goes dark because of the loss of the disk. You're right about the title, it's not a "biggest possible" limit

[@4623620]

@@mrfurieux9587 🖖😎👍 ❗

[@peteman-ur9gi]

So there's sort of an unofficial upper bound of how big they are likely to get naturally, but lets say you had the power to shove more and more matter into a black hole. Is there a limit to the size then? Like... is there a point where they evaporate faster than they can eat matter?

[@garethdean6382]

No, indeed their evaporation becomes SLOWER as they get more massive.

[@hissingsidll750]

The thinking mans crumpet ..........thought I`d drag it down to my level 😆

[@AnnoyingNewslettersPage6]

Office hours with Dr. Becky!

[@tomschmidt381]

That was interesting, I had not thought about black holes having a maximum size.

[@Kevin_Street]

I thought they just grew and grew until they ate everything nearby. It's really surprising to hear they may have a maximum size.

[@trollerjakthetrollinggod-e7761]

@@Kevin_Street it is understandable. The bigger it is, the weaker the surface gravity. At a certain point it's almost nothing

[@nosuchthing8]

I doubt there I'd an actual limit

[@adamplentl5588]

@@nosuchthing8 is that based on something other than your tummy feelings?

[@pikiwiki]

That drawing. very cool

[@TheGiantHog]

It’s so weird, black holes give me this existential fear like nothing else

[@Astro_Oogo]

I feel the same way! I view it as, we know of our own mortality as humans. But in a much larger scale, black holes are the inevitable ‘death’ of most matter in the universe. Learning about black holes, my atoms are vibrating with anxiety!

[@georgejones3526]

The whole universe gives me the heebee-jeebees.

[@Triantalex]

??

[@MrGemaxos]

Why does the selfgravitational radius not grow with the mass of the black hole/with the size of its eventhorizon?

[@boredgrass]

Finally Sixty Symbols is complete again!

[@ibrahimswiss8714]

It was difficult to understand, that's due to my simple brain. I need to buy the book to understand more, thank you for explaining. 🙏🏼

[@OvidiuHretcanu]

another example of the explanation that is waaay more interesting that the answer itself

[@robotaholic]

I think the most distant jswt photos show galaxies not all merged or grouping enough to explain the observations that early in the big bang. Like they aren't merging which others enough to explain size today

[@feynstein1004]

I find it interesting that black holes are the only things in the universe that are infinitely scalable. You could take a microscopic black hole, add a planet's worth of mass to it, and it would still be a black hole, all the way up to galactic scales.

[@Ylyrra]

From our perspective outside the event horizon that's self-defining. If we could see inside then maybe we'd have different names for the different behaviours we'd see, and consider them to be different beasts entirely.

[@feynstein1004]

@@Ylyrra I had that thought too but as of yet, we can't peer inside the event horizons, so they're all black holes 😅

[@davidwilkie9551]

Or from the Holographic Principle Imagery POV, Spacetime is the orthogonal-normal distribution of Black hole Singularity-point positioning by Sublimation-Tunnelling, mathematically speaking in Susskind's version of ER=EPR information In-form-ation.

[@b0hab]

Is there an upper limit to how large they can get through mergers? Or do the same principles apply to entire black holes as to other accreting material?

[@garethdean6382]

Yes, the expansion of the universe prevents everything being gravitationally bound, once all the mass of a galaxy cluster collapses into a black hole there'd be nothing left for it to consume. The limit there is perhaps 10x that of accretion.

[@ericeaton2386]

Actually, black holes orbiting each other and eventually merging really do follow different rules. The gas in the accretion disk is losing energy (and thus it's orbit is decaying) through collisions. Two black holes orbiting aren't colliding with anything, but their orbits still decay. They are actually losing energy through gravitational waves, and it can be a *substantial* amount of energy. Like, several solar masses worth.* But that means that as long as they can get close enough to orbit, they can merge, regardless of size. So the only limit is the expansion of the universe pushing things so far apart that they'll never encounter another black hole. *See R. Abbott et al., "GW190521: A Binary Black Hole Merger with a Total Mass of 150 M⊙" for an instance of an 85 M⊙ black hole and 66M⊙ black hole merging to produce a 142M⊙ black hole. But 85+66=151. So they collectively lost 9M⊙ worth of energy as gravitational waves. Super cool stuff.

[@neoanderson7]

Can’t wait to receive my copy. Amazon is taking forever

[@RFC-3514]

9:50 - You can see the mental effort. _"Don't say 'galaxy clusterfuck', don't say 'galaxy clusterfuck'..."_

[@principal4816]

How do we measure the mass of a black hole in the first place ?

[@garethdean6382]

The best way is via orbital dynamics, that is, to measure how fast things are orbiting around them. We can get this from the Doppler shift of light at different distances from the hole, or directly if a bright star is orbiting. In our own galaxy we see stars in the center orbiting 'nothing' as speeds that can reach 5% that of light.

[@Algo-sk6ot]

@@garethdean6382 Thanks a lot for the answer, it makes sense. I guess emission by the accretion disc of some wavelengths (X-rays, maybe even gamma rays ?) can also be a signature of very massive black holes, when the latter are active. In the method you describe based on orbital dynamics, how can we know than this is due to a massive black hole rather than a smaller black hole + some dark matter ?

[@garethdean6382]

@@Algo-sk6ot Generally by looking at a range of objects at different distances. For example, whatever's in the center of our milky way doesn't have a diffuse mass, objects twice as far away orbit at 1/4 the speed, as would be expected from a point mass. The 'rotation curve' of our galaxy by contrast shows clear evidence of dark matter throughout it. Stars twice as far out can be orbiting at the SAME speed. If closely orbiting objects show 'messy' orbits, this is evidence of something more complex at the center. A single black hole provides the simplest scenario, an almost platonic ideal.

[@silverXnoise]

Throwback! Am I eating dinner at UNC Greensboro circa 2010?

[@imcoolpramesh]

For us it will take 4 rough billions for milkey way and andromeda to collide but for the center of those blackhole, its happening in few seconds or even less than 0.000001s. I think time, mass, and there are few more elements which shape the basics of our dimention. its a grand puzzle.

[@josipgrgic2409]

Couldn't we detect the black hole by its effect on other nerby stars? Even though the black hole reached the maximum size above which there is no disk of stuff, still the hole has some mass and is affecting the path of the stars that pass by or orbit it?

[@AluminumOxide]

1:11 actually it’s 12 times wider than the solar system

[@johnjay6370]

I know this will most likely not get answered or we just don't know, but is there any cosmic event that can cause a black hole not to be black hole anymore? Meaning example if a black hole is very closely orbiting a more massive star that is still undergoing fusion and could the gravity of the larger more massive star cause a disruption in the spacetime of the black hole in such a way that the escape velocity is no longer the speed of light meaning the black hole is getting pulled by the more massive star causing its gravity to change? I just wonder if there is a perfect scenario that can cause something like this to happen, even if it is far fetched?

[@Crushnaut]

no, density is far more important than mass in your scenario and the black hole is always more dense by definition, thus the black hole would always feed off the star the far fetched scenario you are looking for is an black hole rotating extremely fast. Fast enough, and it can theoretically become a naked singularity

[@johnjay6370]

@@Crushnaut Thanks for the replay!

[@GodwynDi]

Or theoretically one could destabilize from hawking radiation decay. It would take a phenomenal amount of time to occur

[@johnjay6370]

@@GodwynDi Really? I thought it still stayed dense, I understand it will lose mass, but not its density. Thanks for the response!

[@AppNasty]

3 questions. 1. What makes everything orbit the milkyways's BH? Does its pull reach as far out as the edge or is it that the nearest stars have their own gravity that holds on to the further out stars and those have gravity that pull on further out stars and on and on? 2. Say you find a BH at its max limit. So much that a grain of sand cannot fall into it. What would happen if you took your perfect tech ology and perfect ship to the edge and force shot a missile at the right angle and speed? Would it automatically change its trajectory and orbit? What would happen if it falls in? Would the BH 'trade' it via ejecting something? Would it create a new object? What if you had 2 of them at their max and say...artificially you could push one of them at the right angle and force them to merge? 3. Is there math we could do that would answer what TIME would be like between 2 of these BH in maximum close orbit of one another? Say 2 got as naturally close to each other as possible. And say you in your perfect space ship are protected and in the middle of them. What would time do?

[@Crushnaut]

Couple questions; 1. Wouldn't these ultra massive black holes still be able to eat via things orbiting them giving off energy via gravitational waves and loosing orbital energy? 2. Is the inner most stable orbit an exact circle? If there was structure inside a black hole (big if) could we learn about this structure by studying the shape of the inner most stable orbit? 3. You say things colliding with this black hole would be rare. Yes space is big, but my calculations have the radius of a 50,000,000,000 solar mass black hole as being about 1000 AU (1.5% of a light year). That seems to be getting into the size that stuff would be bull's eyeing it all the time. Perhaps not a solar mass of stuff, but over time I would think this would still appreciably increase its mass. Am I wrong here? 4. Why didn't you draw the black hole top down? LOL Fun Fact; a black hole this big would take about 1.5 x 10^99 years to decay via hawking radiation, however, currently it would not even emit as much heat as it would gain from the cosmic microwave background radiation. Given the expansion of the universe, this black hole will be one of the last objects in the universe.

[@garethdean6382]

1.) Yes, as well as orbital rearrangements. But this is a VERY slow process compared with accretion and would not appreciably add to the hole's mass in the next 100 billion years. 2.) The ISCO is a spherical region where any disruption causes an object to fall into the hole. If the hole is spinning or not itself perfectly spherical, this region grows larger than expected. So measuring it WILL tell us something3.) about the hole. 3.) Not really. The space around these holes is not random, most objects will be orbiting the hole itself, where the physics tends to prevent them hitting it. It is not just a matter of drawing straight lines through a galaxy and seeing how many cross the hole, objects will be actively positioned and moving to avoid collision. It is remarkably hard to hit a central mass.

[@simonmartin4599]

I think a dumbed down way of describing it is by saying there is a maximum radius to which matter beyond it can't get spaghettified. Galaxies can act galactically outside still.

[@terryarmbruster9719]

Theoretically the uppermost limit no matter the conjectures would be to take total energy/mass of universe translate it into mass then work out the size from there via gravity equations and geometry

[@GeirGunnarss]

Love Dr. Becky.

[@Reddoguk]

I wonder if stars and black holes have a north and south pole. Because the milky way is a huge plate shaped object i'm guessing that any ejection from our black hole wouldn't hit any of the spiral arms but like a spinning top they would just go up and down and miss everything.