A good starting point is On Continued Gravitational Contraction by J. R. Oppenheimer and H. Snyder. If I remember it correctly that is the nice paper where light cones fall graceful along the geodetic lines of the metric of the black hole into it, explaining the event horizon virtually by means of illustration ... a point that could be appealing to a graphic artist.

Dear Jofre,

Thank you for your reply. I don't see your response on the website but I did get an email. Unfortunately, I must be doing something wrong. My input is this:

1. time in rest frame (what or where is the rest frame?): 90 years
2. gravitational acceleration: 1.52 x 10^12g
3. radius: 30km

My answer is -1.423 x 10^9 i seconds. I don't know what i means, and I'm not seeing where I wait 63 years to watch my friend age 90 years. It also contradicts an astronomer who only would say I'd wait "less than a blink of an eye." I apologize for the confusion. This subject is a bit thicker than I'm used to :-)

<<If you know very little about general relativity (even though you might be a great graphic artist!) how can you write a small book about black holes for middle school students? Are you partnering with a physicist who is well versed in gravitational physics? Are you an expert in that yourself? If not, how good the students get a good book?>>

First, thanks for your reply and the recommendation of Lawrence Krauss. I will see if I can get in touch with him.

You ask a very good question about how good the book will be. The book (really a reader) is twenty pages and 2000 words, plus pictures. I've been studying black holes for a year now and believe me, there's enough there for 2000 pages even for the average graphic artist. It's very hard to write about this subject without getting into the tall weeds, and some concepts are difficult to wrap the brain around. How do you explain general relativity in two sentences for a 10-year-old? That's the challenge. I'm working on the first draft of the manuscript, which will then go to my editor who's an expert in educational writing. It will then indeed be fact checked and discussed with a physics expert. And then the book will be leveled for the appropriate age, and then, most likely, be fact checked again. It's a long process.

Although I don't have a deep understanding of the physics, I have a reasonable comprehension of the facts and concepts. I do understand time dilation, the equivalence principle, and even a bit of the Lorentz transformation, but for the finer mathematical details I get lost in the equations. And yes, I did watch all two hours of Dr. Physics. Even grasped some of it :-) https://www.youtube.com/watch?v=foRPKAKZWx8

The purpose of the books isn't to provide a comprehensive study but an introduction. Hopefully, kids (and maybe even adults) will find black holes and relativity as fascinating as you and I do, and inspire "Hey Dad, I bet you didn't know about this . . . !!!"

Thanks again for your help and best regards,

Jack

Dear David,

Thank you for your reply. Unfortunately, I need further clarification here too. What does 0.00707089 correspond to? Is that how many seconds of my time near the black hole passes relative to my friend's at a safe distance?

I looked into your book on Amazon ($175!). Remember -- I'm a graphic artist and haven't done algebra in twenty years. I can tell you the difference between Helvetica and Helvetica Neue, or make you a darn good logo ;-)

Hello,

I am also trying to use the time dilation tool for a supermassive black hole, specifically, TON 618, which has approximately 66 Billion solar masses. However. I continue to get imaginary numbers. Here is the rundown:

So this gives us a horizon radius of 1.949x10^14 m, or 1.949x10^11 km

Converting to g, this gives us 23.515 g (doesn't this seem really low?)

Entering these figures, I keep getting imaginary numbers. Does I make a mistake somewhere along the line? Thanks in advance.