Frank Wang’s Black Hole Admiration Suite (and Why I Built One)

WellΒ you’ve found it. Congratulations!

Catpic used under (cat’s) permission.

The big black hole

Do you know that according to the maths (as I understand it) of General Relativity, a “gravitational lens” could be demonstrated in my living room (without myself eating 10^24kg of pizza)?

I will show you how I used an optical “gravitational” lens to produce an Einstein Ring, and then discuss how we realized it in Space Engine (Get SE here! As part of the community, I am pleased to advertise that Space Engine has been featuring lively – and safe – black holes for a long time.)

We will be using a home-made iron stand, a selection of light sources and a wine glass. That’s all.

Experimental Setup
Close-Up at the “lens”. I couldn’t afford to break the cup and only use this part… Sorry.

It’s then easy – and somehow intuitive, unlike most ofΒ RelativityΒ in daily life – to observe an Einstein Ring for yourselves.

Place your light receptacle (eyes, for example) right above the opening of the cup, and shine light upwards, from the bottom.

I managed to get one like this.


More GIF! A blackhole passing in front of a star cluster in SE

Pierre de Fermat said that light always takes “the path of least time” in optical instruments. Similar to that, a ray ofΒ light in a perfectΒ vacuum travels entirely in straight lines, although sometimes spacetime – “straightness” – itself can be distorted.

Representing 3-D space in some lower dimensions is a familiar way of representing its distortions. And it – you bet – at times looks just like a wine glass.
Image Source:Β

On the ginormous scales, we have evidence of the very phenomena, BTW. Ask any researcher working at the OGLE or MOA Projects, or simply look at the picture below, in which a sufficiently weighty elliptical galaxy, a “lens”, wears aΒ distorted image of the more distant galaxy as her necklace.

Source: Wikipedia

Computationally, the analogy of wineglass optics was how the developing team approached the problem in SE. Thanks to the use of a good distance buffer, Space Engine could sample snapshots, “blackhole billboards”, of what is directly behind the black hole from the camera, and apply the lensing effects to them, iterating 2 to 8 times on different distance and detail levels based on user settings.

To save processing power, however, the entire lensing system is only active for “very dense” objects such as black holes, neutron stars and white dwarves.

After 2015, fancier things happened to Space Engine. Black holes sometimes generate with accretion disks and fake blueshift effects (its vicinity to the player tints the sky bluer… The current SE only works in the visible spectrum of things), making them even more stunning to behold.


Another Black Hole, in SE 0.9.8

I built this black hole, in the way that I did not build it. It was rendered using our program. However, since we had created an entire universe, laying down all the rules to allow for procedural emergence, this very object was not met until a long time after my expeditions into our own creation.

Maybe Space Engine is more like TRON than Stellarium?
I love OpenGL.

FW, 2016

“z1” was a clever URL choice.

You may always escape this black hole by clicking on the (now obsolate) logo below:


2018 Edit

Yesssss. I took Physics 139 (Special and General Relativity) and realized that this pages deserves a review long overdue.