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  • (bell rings)

  • - Hello and welcome to a black hole coding challenge.

  • Time has really slowed down for me,

  • or maybe it's sped up.

  • I can't remember which is which because

  • I'm actually now recording this many days

  • after the actual livestreamed coding challenge.

  • In a little bit, I will change my clothes and

  • travel into the past through the black hole.

  • I don't know how it's all going to work,

  • but you will see me live coding,

  • writing the code to do this simulation.

  • In truth, it's less simulation than visualization.

  • On April 10th,

  • the first ever image of a black hole was published.

  • This image was put together by a team of scientists

  • known at the Event Horizon Telescope.

  • It was compiled from data from many telescopes

  • all over the Earth all synchronized.

  • I looked at this image and I thought,

  • it looks kind of fuzzy and glowy and

  • maybe there's some way I could reproduce

  • this image through a simulation.

  • I started to sort of dig into this.

  • I quickly realized I'm many, many steps away from doing that

  • and I wanted to find the place to start,

  • somewhere where I could at least begin to

  • simulate or visualize the behavior of

  • space time and black holes.

  • Here are the resources that I used to learn about this.

  • First, let me thank Veritasium's video,

  • the how to understand the image of a black hole.

  • This video was actually published

  • the day before the image was revealed,

  • which is really kind of amazing.

  • If you watch this video, the explanation is superb.

  • In particular, there's a short animation in the video

  • that depicted beams of light traveling

  • towards the black hole,

  • some disappearing into the black hole,

  • some wrapping around in an orbit.

  • That's my starting point where I was interested in.

  • I also learned quite a bit from Chris Orbin

  • and the STEM Coding YouTube channel.

  • STEM Coding, if you're not familiar

  • with that YouTube channel,

  • you should definitely check it out.

  • They have a lot of videos about physics and science

  • taught through the lens of coding and visualization.

  • In particular, they have a video called

  • Slingshot with Gravity and Chris Orbun

  • published an article explaining how that

  • code example could be tweaked a little bit

  • to kind of get at some of the ideas

  • around how gravity and black holes.

  • Finally, there's a wonderful paper from 1978.

  • Thank you to Veritasium also for this reference

  • called Image of a Spherical Black Hole

  • with Thin Accretion Disk.

  • This paper has diagrams and the mathematics

  • behind the photon trajectories around a black hole.

  • It gives you a lot of background into

  • what you would want to do to visualize a black hole.

  • Of course, I'm not the first one to try this.

  • Many people have made beautiful visualizations

  • and artistic renderings of black holes.

  • There's the one that you might remember

  • from the move Interstellar.

  • Kip Thorn, a Caltech physicist,

  • was actually an advisor on that film,

  • but there's a lot of artistic license there.

  • I also want to point out to you Ricardo Antonelli

  • who's written this wonderful article

  • How to Draw a Black Hole,

  • Geodesic Raytracing in Curved Space Time.

  • In the article he goes through step-by-step

  • a bunch of different computer graphic tricks and techniques

  • along with the sort of physics of black holes themselves

  • to create a 3D visual of what a black hole might look like.

  • If you've watched me before,

  • you know I am not a physicist, I'm not a scientist.

  • There are many caveats.

  • I don't play a physicist on YouTube.

  • I'm just here wanting to make something

  • in 2D Canvas JavaScript.

  • In fact, I already did it.

  • What I'm here right now,

  • let me talk to you about the pieces

  • that I want to put in this visualization

  • as a sort of reference point for when I start coding.

  • The black hole that I want to visualize is in the galaxy M87.

  • It previously didn't have a name.

  • It was just called M87 star, the star for black hole,

  • but it was recently named Powehi.

  • I'm not sure if I'm pronouncing that correctly,

  • but it is from a Hawaiian chant

  • and it means something like adorn, dark,

  • fathomless creation, something like that.

  • Very appropriate for a black hole.

  • This is what's known as a super massive black hole.

  • Not all black holes are super massive,

  • but this one is and its mass is equivalent to

  • 2.6 billion solar masses, or suns.

  • Take the sun, our sun,

  • the one up in the sky that shines on us,

  • and put together 2.6 billion of those

  • and you have a black hole.

  • It's so massive, we can't see it.

  • Why?

  • Because the gravitational pull is so strong,

  • there's so much matter in there,

  • that any light traveling towards it,

  • once it gets to a certain proximity, can no longer escape.

  • You couldn't be inside the black hole

  • and shine a flashlight.

  • You could be there, but outside the black hole,

  • you couldn't see it 'cause the light can't get out.

  • Of course, you couldn't also be there because

  • you would be dead, very, very dead in the black hole,

  • or you'd just be like Matthew McConaughey,

  • one or the other is true.

  • This little ring here,

  • this distance from the center of black hole

  • at which nothing can escape, not even light,

  • not even the fastest thing we know about light can escape,

  • is known as the event horizon.

  • There's actually a formula for calculating

  • the distance from the center of black hole

  • to that event horizon itself,

  • the Schwarzschild radius, or R sub S.

  • The Schwarzschild radius is calculated as two times G,

  • the universal gravitational constant, times M,

  • the mass of the black hole itself,

  • remember, 2.6 billion solar masses,

  • divided by C squared where C is the speed of light.

  • Of course, the event horizon isn't really a circle.

  • It's a sphere, but for us in our 2D simulation,

  • we're going to make it flat.

  • In order to actually calculate this,

  • I need some of these values.

  • I have the mass, I also need C, the speed of light,

  • which I'm looking over there, I don't have this memorized,

  • which is 299,792,458 meters per seconds squared.

  • That's very, very fast.

  • Not seconds squared.

  • I don't know why I put seconds squared there.

  • It's just meters per second.

  • This number, meters per second.

  • That's the speed of light.

  • I also need G, the universal gravitational constant,

  • which is 6.67 times 10 to the negative 11th power.

  • Now, with these values, with the mass of the black hole,

  • with the universal gravitational constant,

  • with the speed of light, you can actually calculate this.

  • I will leave that to you to calculate

  • and leave your answer in the comments,

  • or you could probably looks it up

  • because people are calculating this stuff all the time.

  • Another element that I want to include

  • in my visualization is the accretion disk.

  • The accretion disk is a whole lot of matter

  • that's outside of the event horizon

  • orbiting the black hole and sort of feeding the black hole.

  • This is a particularly active one.

  • Again, a black hole isn't emptiness.

  • It's we think of it as emptiness.

  • There's just so much matter there

  • that the light cannot escape so it's nothingness.

  • So crazy.

  • The accretion disk is this orbit that's

  • outside of matter orbiting.

  • It has a specific measurement where it is,