I appreciate your effort in making everything you talk about interesting and easy to listen to. Never stop!

Thank you so much for your hard work on these videos! You are wonderful at taking complex things and chunking it down to concepts that are understandable. If you ever offer an online course(beyond what amazing stuff you do here), please let me know and I'd sign up instantly.

It takes skill to deliver an accessible explanation of so many concepts in one video, nice job.

The production value of your vids just keep getting better and better! Really awesome nerdy technical stuff presented in such a fun and lighthearted way, thank you Dr.

"My arch nemesis at the minute is grass" I laughed at that way too much xD

2:27 "Depending on the accretion dixxs temperature" My chuckle moment of today :p

Black hole: I will eat everything Physics: You can‘t Black hole: crying

2 of my favorite things, You AND Jeniffer Lawrence , in one video. I love your enthusiasm and passion. And how you talk with your hands.

I could look at and listen to you all day. Informative video. The bloopers at the end was also funny. Looking forward to more.

You do an excellent job at explaining such complex phenomena

9:55 “wwwwweeeeeeeeeeeee!!!!!!!!” That’s all I can offer on this video. I ain’t none too smartest. 😆😆

Surely D_isco=2*R_isco

I appreciate your ability and attitude for science education! This is good youtube channel.

Very nice talk on a complex subject. Many thanks Rebecca.

Thanks Becky for an intelligent and fascinating insight into the properties of black holes, you are a breath of fresh air, we need more people like you to educate and share knowledge, keep up the good work.

Thanks Becky, learned something new today ... size limit of black holes and them winking out.

Thanks for including 3C 273 -- my favourite object to show people at public viewing sessions

Awsome,beauty,humor,and brain do mix very well. I like yours video, thank you

That book was a Fantastic read. Anyone who enjoys Dr. Becky already knows this. Thanks for the video.

Thanks for the great video Dr.. One of your guests asked a question that most laypeople wonder (because we just don't know enough to not ask) and that is: "Tom Hathaway - Wouldn't a black hole with all the matter in the universe in it essentially be the same as it was before the big bang?" PLEASE address this because if you don't we'll go around spreading this rumor and it'll all be your fault. hugs & kisses

It was discovered in the 50's in mexico in tonazintla puebla radio telescope, and it was in the catalogue number 618, hence the name ton 618, but still they can't see it's host galaxy due to be so bright the hyper luminous quasar that it almost blocks the whole galaxy

You put the dart in the bullseye once again! Love the introductions of comic spoofs from modern media. It really lightens the heavy material that seems to broaden the appeal to include more folk. I'm intreagued by your prep work and would luv to see your notes. Not only fo you not refer to them, you hardly take a breath for the entire video. That's your enthusiasm & excitement from how much you enjoy what you are doing! 😎

Another fascinating topic. I may not follow everything you discuss, but I still learn something new every time. I do have one request - given the enormous size and the huge variation in scale of just about everything in the various images you display, would it be possible to add a legend or scale to these images? I often get lost wondering whether a galaxy you've displayed is tens of thousands light years across or a few million.

This is the first time I’ve found a clear explanation for how a black hole forms the jet streams of a quasar. Fascinating video! Thanks! You look great, too.

4.38 that's going to be my new tattoo! Wanted black hole tat! That's the one! Thanks Dr bex xx

2:28 did I hear that right? 😂

I love your videos, you make learning alot of fun and easier to understand. I can't wait for your book to hit the market. Please keep the amazing videos coming. Much love from backwoodsTennessee. 🤣

My childhood illustration of a black hole was Figure 14-17 from "Astronomy: The Structure of the Universe" (William J. Kaufmann, III (1977) p. 449). I have a copy from the same printing in my lap as I type. There's a lovely half-tone illustration of the old spacetime funnel swallowing inbound line drawings of a radio, a loaf of sliced bread (the slices are falling out of the wrapper), a clawfoot bathtub complete with shower head, a quill pen, and, best of all, a dinosaur! Sadly, all that remains of these explorers after passage through the funnel is "Mass, Charge, Angular Momentum". I recently reacquired this childhood astronomy text because I want to compare what was known in childhood with what's known today in astronomy. This video from Dr Becky has me dusting off my Kaufmann and opening Chapter 13, which describes the discovery of as much as was known about quasars in 1977. The big new anomaly to explain was the quasars' massive redshifts. Perhaps it was gravitational: the quasars could be supermassive so as to drag local spacetime to such an extent that the emitted light was redshifted at the factory, so to speak. But the masses required would undergo gravitational collapse and necessarily be black holes (what a foretaste of glory divine, I'm not a physicist but it seems they were reaching the right answer, but for the wrong reason). Another idea, that quasars represented nearby objects expelled from local galaxies at enormous speed, was easier to dispose of: if that were the case, there would be as many coming towards us as away (blueshifted v. redshifted), and all the known quasars were redshifted, none blueshifted. The emerging dominant idea therefore placed the quasars out among the distant galaxies, but there were problems. The most distant galaxy yet seen was 8.5 billion light years away, and the quasars' redshifts placed them enormously farther away, 15 to 20 billion light years away, more than double the distance to the edge (in 1977) of the observable universe. The brightest galaxies then observed, cD Ellipticals, would never be detectable to the best telescopes of the day at such a distance, so quasars must be stupid bright: the equivalent of billions of suns, for them to be observable in 1977. So they must be big, to generate so much power. But they were observed to be variable, which means they're compact, much smaller than the diameter of a galaxy. Kaufmann ends the section with these words: "When someone finally figures out what quasars are, mankind will have made a major breakthrough in discovering new laws of nature and will have arrived at a much deeper level of understanding physical reality." Looking back from 2021, knowing only what I know (as the 52 year old version of the ten year old me that marveled at the Kaufmann book), it seems that the data on the true nature of quasars was staring them in the face. Accurately measured redshifts only fit great distances for the quasars. Late 20th century astronomers were masters (and mistresses) of accurately measuring brightnesses, too, for sure, with their super sensitive films, 200 inch telescope, heterodyning radio receivers and massive radio antenna arrays, etc. I'm sure we have sharper data now, but what they had was accurate to known limits of experimental error. Why was it still a question? It seems now that there was the need for a leap of the imagination, to believe the data before them, which implied that the universe was far larger in size than that implied by the feeble light from the most distant galaxy then observed. What Timothy Ferris, in his "Coming of Age in the Milky Way", calls "Raising (and Lowering) the Roof". Thanks for such a wonderful series, Dr Becky, it's a thrill to contemplate how much has been learned just in our lifetimes.

This is brilliant! Such a great explanation. Really enhanced my understanding. Thank you!

The reck it ralph cut away really got me

Great video! Just one feedback: you don't need to insert random video clips throughout the video. Your videos are interesting enough by themselves :)

I love your videos so much I pre ordered the book

I don't understand, if Fgrav=Frad then that means stable forces, so means no material would be moving in any direction, so what the Black Hole absorbs/accrets energy from that dynamic equilibrium? I like your bloopers at the end, your human side, funny and sweet :D

My wife was asking who is the Becky you keep telling me about astronomy from. I showed her your channel she's relativitly happy now.

Thanks for your content! You have a very easy manner and explain things quite well. Keep up the good work; a star in the making with a nebula, you are.

That is insane, I cant even wrap my head around something of that mass! Thanks for the explanation, very compelling indeed!

Of all the youtube and other hype that's followed the pictures of the supermassive black hole, this is by far the most interesting calculation and conclusion I've heard. Before this I always thought that black holes would just continue to grow and grow over the age of the universe. Now granted over trillions of years mergers will produce black holes larger than this limit in the black hole era, but it's interesting to know that before then the size will be limited.

My favorite channel.

"ISCO ISCO ISCO ISCO" ok, I'm dead from laughing! :-)

Very informative and entertaining, and you explain things clearly. Nice style of videos :) Regarding the formation of black holes way back when in the early universe, it might also be interesting to mention a theory about 'direct-collapse black holes'. These are theorized to have formed during the 'primordial' universe, not from the death of a star, but directly from an extremely hot, unstable gas cloud. They're predicted to be able to weigh up to 10^4 to 10^6 solar masses at their 'birth'! Pretty crazy. Anyway, yeah, I'm going to watch another one of your videos now, haha :)

Nice closing line in this video :) Sort of dramatic and funny :D

Amazon to notify me when the book is available. Since I don't have you available to tell me bedtime science stories..... I got the book instead. :P Love your videos.... awesome.

I still don't get it. If a black hole is a collapsed matter into itself, how come they can be bigger or smaller? Doesn't the matter collapse into a single point in the middle of a black hole? If a black hole swallows let's say a star, isn't the material of a star forever lost in a singularity of a black hole? Sorry if I sound ignorant but I'm not a physicist and I would really love to be able to wrap my mind around that.

so happy i stumbled upon this channel. it is always a pleasure to watch your videos

I'm having a lot of fun pressing the '5' key :-)

Thanks for your amazing videos :) Could you please expand on what you mean when you say that black holes will simply wink out of existence if they get too big to acrete any more material? Wouldn't they still just hang around?Thanks.

I just came across your site. You don’t talk down to people as others are. You are the best astronomer I’ve come across. I do have a question, when Pluto was photographed a few years ago it was bright enough to look like how the moon looks.. how could it be so bright when the sun is a pin prick in the sky?

Quasars winking out and the expansion of the universe eventually making other galaxies unobservable makes me wonder how many other phenomena observers might have seen a few billion years ago that we'll never know about.

It depends on how empty the space is around it. The size of black holes is regularly massively underestimated because the speed of their discs is underestimated given how slow the speed of time is near a black hole where time practically stops inside.

A young star in the making! Thanks for educating, please keep doing it.

Awesome video!

Absolutely love your videos! Recommendation on editing... Please lose or minimize the injected clips. It makes things feel a bit like it's trying too hard. Your amazing perspectives are quite exactly what I come here for. You don't need to become another generic science communication show. Great question and great answers. My favorite was whether or not black holes accrete dark matter, well done.

I've actually been thinking of galaxies as giant accretion discs for giant black holes. Glad to see that wasn't such a crazy idea! :D

This was an interesting video. As a consequence, I hovered my mouse pointer above the icon reminiscent of a stylised upturned thumb and clicked the left mouse button, thus registering the fact that I "liked" the video. I have to go now. My planet needs me.

Hey Becky! I would love to see a video about "how can black holes grow at all, given time dilation from the perspective of an external observer." So not "how does matter fall into a black hole (coordinate transformation)." but "why do we see black holes grow?" That would be awesome! Love your show!

LOL I love your blurb inserts.

Q: How big can black holes grow? A: Yes

Black holes, black holes, black holes, we all love you so much, but not enough to want to meet you in person.

Got my book order in!

I really like your content, just kind tripped over it this weekend and already watched a few of your older ones! Keep up the great work! I can listen to space all day! Your Friend from the Esoteric order of Dagon.

Dang it! I missed so much information because I kept thinking about mergers...need to listen again.

Dr. B, when do you move into your new digs? I want to see your diploma hanging on the wall! Thank you for another great video. It seems that so much astronomy is anti intuitive. Having a limit to how much material a black hole can accrete is an example!

Makes me think that the big-bounce theory could be more likely than a single big-bang Universe. Always had a sneaky little penchant for that one over a single event.

Thank you so much for uploading this video. It is helping me to get through the pandemic!

I've always wanted to ask: because of time dilation due to gravity, do events or mass even exist at the singularity? If there is no time, no meaningful kinetic energy and so no time, no particles, how could anything exist?

Hey there I have have a question. If the big crunch did happen wouldn't all the black holes merge together?

So.. at what mass would the accretion disc be spinning at the speed of light? Would all the matter in the universe be enough?

nice explanation

Book called, Space : Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space.....the end.

All-encompassing black hole: "...so its not like thats a possible doomsday scenario" Reason that thats not happening: another doomsday scenario.

Seems to me that once you get the innermost stable orbit out to the point where gas self-gravitates to form stars, you don't stop accretion entirely, because the stars and other things formed out of the orbiting gas would still interact with each other gravitationally, thereby still enabling momentum transfer so that the inner things can still spiral into the black hole in the course of causing other things to be ejected (or, given enough time, in the course of throwing off gravitational radiation). So the accretion process wouldn't look like a quasar any more, but it would still feed matter into the black hole, even if not as rapidly (and as the black hole continued to scale up, the rate would scale up accordingly as long as more material was available).

Loved your explanation, makes my head spin, great video Dr Becky. FYI Real Madrid have an Isco too 😄

How long does it take light to travel the distance from the event horizon to the edge/end of its gravitational effluence? Could the effect of time dilation render that light older than the universe?

متوهجة دائما في سماء المبدعين

I always sort of assumed that a black hole could eventually absorb everything, and still not be full.

im hooked on her videos!

I am delighted to learn about extraterrestrial space by watching your talks! :)

Well done Becky

In the first minutes of universe, just after the Big Bang, what prevented the whole mass to collapse under its own gravity and become a black hole?

Around a decade ago, they were saying that the most massive a BH can get is only about 10 billion solar masses, but now we know of several over that size. So how confident are you that your limits are real now? Also what do you think of the calculation that shows that the entire mass of the observable universe can fit inside a BH with an event horizon of around 500 billion light years?

THANKS ! Great Lesson ! Good Luck on your allergies. You remind me of Dr. Wendy O. Welch. Thanks for learn'n me! Enjoyed the topic !

Doesn’t frame dragging also play a key role in black hole accretion? Also isn’t it possible that SMBHs are primordial so their starting mass could have been large?

That was Great!!! Never seen anyone explaine that before, and I watch a LOT of this stuff.

I think, looking at the universe, this is what imagination looks like if you could step outside and see it, the resonance of curiosity beauty and wonder.

Question / video request - why didnt the big bang immediately collapse into a black hole given the matter/ energy density.

66B is the max mass BH can form an accretion disk, without an AD, it's not easy to see a BH across the visible universe, so, the fact is we are not really sure whether there are more massive ones hiding out there.

In with a bang,out with a whimper? This is beginning to sound like an Azimov story! Maybe "The Last Question"? Or "The Final Question"? Its been years! I enjoy your vids! Keep em coming!

Love the effort you take in simply explaining some rather complex concepts. Any chance of tackling dark energy?

I see massive black holes every day when I look into my co-workers faces and ask them to help me with some task. I have trouble with the disc image of matter spinning around a black hole and it not being a full sphere of material like a giant cloud spinning in all directions at once. I guess the subatomic model doesn't apply here. Also, if matter is "disappearing into the black hole and, I thought, going somewhere out of our universe, then why would a black hole get larger?

To infinity and beyond

Dr. Becky, have you had any videos, or could you talk about Hawking radiation in regards to Black holes dissipating? Thank you! Keep up the Science!

I can't remember where or when, but Isaac Azimov wrote an essay in which he supposed that the entire universe is already a giant black hole. The density calculations work out, apparently.

I love your videos Dr Becky, they are always so interesting and informative not to mention entertaining...also it always makes me laugh when you use the word piddly.:)

How big would the radius of that 10^60kg black hole be?

Dr. Becky - Please make a video covering Time Dilation. Many thanks and love the video

66 Billion! A few weeks ago the biggest one I read about was only 16 Billion! Whew!

12:23 Don't you mean "winked out of visibility"? The quasar will go dark because there's no accretion disk, anymore, but the black hole is still there and will still spaghettify anything that gets too close, right?

Hi Becky, are you saying, when the BH gets big enough, it cannot have a stable circular orbit because the matter in the galaxy around it is attracted to itself to the same extent as it is attracted to the black hole, so things get kind of muddled around there, and things that get preferentially attracted to the black hole just fall directly into it?

Thanks for this great video! Love your channel :) There is a question which is killing me for years. I'm gonna ask it here in case you read that comment and have time to answer :) From the point of view of an observer, away from a black hole, an object falling towards the black hole will have its time slowed down until being totally stopped at the event horizon. Is that right? If yes, how come a black hole can grow, from our point of view (earth)? Any object (accretion disk, other black holes, stars, etc.) would never pass beyond the event horizon as, from our point of view, the object is frozen in time. I know I am wrong somewhere, cause black holes can grow. Would you please be able to explain me what I am missing? Please note that I am aware that from the point of view of the object falling towards the black hole, time passes normally for itself. Thanks in advance :)

I am interested to know how black holes and dark energy and dark matter is affecting eachother! Is dark matter in such high percentage of space it should have some effect on the black hole I would think!