My full title is Dr Robert Eagle CBE BSc PhD. I studied at Kings College London, BSc Physics and PhD Nuclear Physics. And if I can do it, then so can you. All good wishes for your continuing studies and for the future.

The world's best physics teacher right here!

Now we need an advanced video about black holes.

Your videos are simply amazing. I have nothing to do with this type of physics, I'm a petroleum engineer (so more like fluid dynamics and things), but I am very interested in relativity and quantum and particle physics. It all comes from my love to cosmology and craving for answers. I feel my life is wasted. Started studying systematically on my own and bumped into your videos. Fell in love immediately. You explain so well. Keep up the good work! Thinking about changing career, despite I like petroleum eng. I couldn't financially support one more degree at 25, but have been thinking about astrophotography. Thanks

Just finished my A-level physics exams, your videos were a great help, thanks a lot !

I love the way that you simplify this information, so that anyone with a basic understanding of Algebra can understand, what otherwise, seems so complicated. I honestly feel like watching your videos has raised my IQ! Ty so much!!!

every time I have a doubt in physics and I see you have a video on that topic I suddenly have a sense of comfort who else agrees?

best description on black holes I've ever heard and beats everything I've read about them so far! Thank you for taking the time to go into this as throughly as you did here!

THE BEST IN THE WORLD....YOU ARE MY INSPIRATION❤️

I just wanted to thank you for your great lecture. I really just clicked on your clip just to see what the clip is about and I found myself listening to your entire lecture. You truly explained the theories in a very interesting and simple way! Thank you! Can't wait to see the other clips!

Decided that a bucket list accomplishment of mine will be to understand the math of black holes, so here I am.

One of the finest teachers of physics.You are good Doc.

Simply AWESOME! I've been looking for an explanation to Bekenstein formula for MONTHS, in order to understand the Holographic Principle. THANKS A LOT, you made it so simple, you are amazing. Greetings from Argentina! :D :D

I actually prepared myself a cup of tea before watching the video, wouldn't you know.

The Alice and Bob example was greeeeeeaaat!!! Congratulations.

I couldn’t understand this with out knowing general relativity. So lucky this guy has great videos on litterally everything.

wonderful explanation... thank you..

This is amazing! So interesting. Gave me a break from studying quantum mechanics which is blowing my mind.

I absolutely love your videos, nothing can replace knowledge, some math, and good old fashioned piece of paper and a pen.

I'm yet to see someone explaining such complex subjects with such clarity. Great job!!

This is extremly well and simple explained. Thank you

Sir...this is possibly the best explanation i hv ever seen in my life..the u hv put up the freaking mathematics and the way u hv merged it wid the cosmos,i believe that u truly deserve at least a compliment...keep it up😄

This has been by far the best explanation I have ever heard! Thank-you so much!

Fantastic video!! Thank you do much for creating these; I'm sure it's very time-consuming, and you can see a lot of work goes into them, so it's truly great of you to do it :)

Wait. Is this channel real!?! I love you, Dr. Physics! Thanks for what you're doing!

best physics vids on youtube!

I always taught Black hole mathematics could only be understood by a prodigy. You simplified iT so even highschool students can understand. Thank you Robert

In the examples I give you cannot go backwards in time since there is no known mechanism for doing so. If you do make assumptions about capabioity of going back in time you have to develop some important rules to stop changing the past which might lead to conflcts (eg killing your own grandparents before your parents were born). Thanks for your kind comments.

In celebration of the first image of a black hole, I'm gonna watch this.

Just for understanding: So if something falls into a black hole, it increases the mass of the black hole and therefore the schwarzschild radius?

Bob Eagles: what a phenomenon! Who else could explain complex physics with a felt tip pen and a roll of paper? Quite extraordinary. Thanks Bob.

Best teacher to explain cosmology

Hi, I do not hold a degree in science; however, listening to your class was so clear and interesting. Thank you very much.

I found one of these down the end of my back yard. I came online to try and learn more about them. I kept throwing the garden clippings and raked leaves in it for the last few weeks, will that be a problem? Does anyone know how to get rid of one? I've lost two cats to it and three cricket balls. It's starting to become a bit of a pain in the arse. I think maybe it was my neighbor; finally had one too many McFat burgers and imploded into a singularity.

I sincerely appreciate the accuracy and detail in each of your videos. You are able to convey a grand amount of pertinent information in very little time. Through conceptual ideas and examples you are able to explain complex theories in physics (and other subjects) very effectively. I wanted to let you know that your attention to detail and effort does not go unnoticed :) Thanks a bunch! Merry Xmas!

Thank you for this invaluable information. I need to re-watch this to really pound it into my brain. I'm not going to school to be a physicist but physics itself has always fascinated me and I've taken the red pill ever since grade school.

Wait, what's velocity again?

A delightfully clear and fascinating video as always, DrPhysicsA never disappoints ^_^ Just out of curiosity, do you think it could be theoretically possible to some day work out so clever a formula that the infinities would cease to be a problem and we could obtain more detailed information? I ask at least partially because I am vaguely aware that similar issues occur when trying to reconcile relativity and quantum mechanics, and wouldn't be too terribly disappointed if such problems were solved within our lifetimes. Please forgive any obvious face-palm worthy facts I may have overlooked, I'm just watching these videos out of curiosity after a month or two out of the game.

Hey Doc, these videos are fantastic and I love the contributions you've made to the community.

The best explanation of black holes ever

DrPhysicsA - In the Alice and Bob explanation, you kind of tricked us there. In the example, Bob always sees Alice as slowly approaching a point, but Alice has no problem in seeing Bob, i.e. The Accelerating person has a perception of the constant velocity person as getting slower. When you moved towards the Black Hole counterpart, you reversed it by saying that the person who is observing from outside sees the person in the Spaceship getting slower and slower. Shouldn't it be the opposite? Shouldn't the person in the spaceship (like Bob) see the outside observer (like Alice) getting slower as the spaceship approaches the Black Hole, but the outside observer has no problem in seeing the Spaceship enter the Black hole and eventually get destroyed? Isn't it?

"As long as you're here, you musn't be there" XD

*Gripping teacher, top tier.*

I must say you seem to be a natural at teaching! I can't thank you enough!

You're talking about advanced concepts, but you're making what we MIT graduates consider freshman-level mistakes: 1. Confusing definite and indefinite integrals; 2. Using formulas outside the ranges in which these formulas are valid; and 3. Confusing arbitrary choices of scale with real physical phenomena. Your reasoning then elaborates these errors into absurdity, which you don't recognize because black holes really are weird. The force of earth's gravity decreases inside the earth, falling to zero at the earth's center. The formula for gravity isn't valid for r less than the radius of the earth. Potential energy from earth's gravity is only zero at the center of the earth; it's positive everywhere else and has a finite, positive maxium at infinity. (A light-year is close enough to infinity to be infinity for almost all practical purposes.) The gravitational potential energy of a mass on the surface of the earth is something large and positive, maybe over half of its potential energy at infinity. The formula for the sun's gravity is invalid for values of r less than the radius of the sun. You take formulas that are only valid for r values greater than thousands of miles and then draw conclusions from them as r goes to zero. That's nonsense. If the truth is more complicated then talk to a real physicist and make things more complicated. Your errors make me not trust anything you say

Very kind. Thanks for kind comments.

Very well explained and written and calculated! Many thanks. It always helps to digest the information by writing it down in (as) simple physics as possible!

I genuinely wish I had the intelligence and skill to come to these conclusions myself. I know the general rules behind Black Holes but to see the math representing it explained makes me genuinely want to get in this field. I'm glad I discovered your channel and not only did I subscribe but now I'm making a genuine effort to get better at math.

I am so happy I found this channel. Thank you!

You're such a genius. Thank's a lot for all your videos; I have only seen a few but they're fantastic

Thank you for this concise, clear explanation of black holes; you managed to first introduce new concepts and THEN apply it to the physics of a black hole, which helped me understand those processes. Wonderful video!

Thank you dr Physics, for your neat explanation and for introducing me to dr. Susskind whose whimsical teaching is so complementary to yours

Now I can guess but as I said years ago you are the best. I feel honoured that once you answered my question some 7-8 years back. Your versatility might have brought you everything that you could have wished for it has lost us you. Best wishes.

What a simple consise logical approach to a complex concept. Well done.

Your lectures are absolutely GREAT! Thank you!

The reason you got hyped sometimes while briefing, I couldn't escape your video.

Now this is Oxford English we non natives all learned in school. Understand every single word he says. Very good. A very good teacher anyway.

this video is really good because you explain it so well anybody can understand, hope there were more teachers like you

This is what we pay tuition for and you gave it to us for free. Thanks for what you do. We appreciate your time.

Very fun and precise lecture! Thanks for the vid and keep up the great work!

Thanks for kind comments.

Nothing escapes from a black hole once it has been trapped (leaving aside the Hawking radiation effect). But the black hole may form something along the lines of an accretion disk by drawing material from a nearby object (eg close orbiting star). It is the effect on that material (which is not yet absorbed into the black hole) that gives rise to the various emissions.

Thanks. You raise a good point. Of course, you can never see the black hole as such, you just see all the material that is falling into it appearing to approach the black hole at ever slower velocities. Since it is in fact accelerating toward the BH (and thus away from the observer) and at high speed it would be substantially red shifted.

Thank you. As you might expect, this is a basic video about black holes. Once you cross the Schwarzchild radius you enter into a very peculiar space time in area where no path will lead you out. If you were accelerating away from the black hole in order not to fall into it (and on the assumption that you never reached the Schwarzchild radius in the first place) then you would continue to see images of something that was falling into the radius apparently taking forever to do so.

This has helped me no end with my physics coursework, which is on black holes. Thankyou for this video

You are an absolutely amazing human being for sharing this with the world

Man you are good! I watched the first 18mins and I understand singularity! And I even dont know my tables anymore :) Great lesson!

THANKS A LOT. This is wonderful explanation of what a black hole is.

Amazing simplification of a rather cumbersome subject, congrats!

you made me love with physics(cosmology). Thanx..

As some others have pointed out, in order to provide an accessible introduction to the subject, I have had to make things extremely simplified. The point is that once you get beyond the Schwartzchild radius space-time is so curved that there is no route out. You are right in saying that light cannot be slowed down in the sense of reducing its velocity magnitude, but its direction can be changed such that it cannot escape the black hole.

Thanks for the lessons and work please continue.

Simply a wonderful video teaching difficult stuff at the right level, especially for those who understand basic school physics but they don't have the right background for specialization and research at theoretical physics!

Great lectures! Glued me to my chair for whole night.Thank you very much.

I know this is probably one of the many positive comments, but really, you did an incredible job at explaining this. Amazing.

Makes concepts easy to follow. Better than many so-called intellectuals.

You are an amazing educator. Thank you for your videos.

Great content, Very intuitive and easy to follow. Thank you for your effort.

Very clear introduction! Great work!

A fantastic video. I like the way you work through numerical examples.

Just finished the whole thing, great video!

Thank you. And greetings from the UK.

extraordinary demonstration! great teacher! congratulation! thank you !!!!

Wonderful!!!,that really expand my knowledge about black holes...

❤ thank you so much for these wonderful videos. The pen is indeed mighty!

Thanks a lot for taking the time of making this videos, they are very interesting and helpful.

A very good video that explains the basic concepts and maths behind those concepts, of black holes, it has given me a better insight into other videos and information on the subject. very much worth watching if you want a bit more information about black holes without need a degree on the subject to understand it. Many thanks for making and uploading it free to view!

Great videos my friend, you are a natural teacher

Outstanding explanation of multiple topics.

That is generally the convention which I use. But you can of course use any convention as long as you are consistent.

Awesome Lecture , I thoroughly enjoyed every part of it ! Cheers :)

Thank you for this wonderful explanation.

BRAVO! bravo! very, very well explained with such degree and elegance!

Wow! Thank you so very much for this!

wow this is so cool!!! learning nowadays is more easy than ever!!! no excuses..

sir, you r the best teacher i ever attended, simply ur explanation is wonderful, after watching your video im fascinated in physics .

Thank you so much your explanation were as clear as day ,and I hope that everyone reading this a very enjoyable pun(I asked my friend why he likes reading books about black holes. he said “because they are timeless”.)

Very interesting. Thanks for this lesson!

This is terrific 💡

You're simply the BEST!