which computer you would need to

[felipe]

generate a whole galaxy with all the planets,stars,black holes,etc

[SyzygyΣE]

A computer that can simulate the physics of billions of stars and planets all at once? I don't think that's likely. It's far too intensive to do all at once. Even if a computer could generate an entire galaxy, the actual physics would have to be constrained to a very small area where the player occupies and updates as the player moves through the galaxy. The rest of the galaxy would either have to be paused or in "on-rail" movements.

[emarksmi]

Well, assuming you don't mean as part of this program, you could probably create a supercomputer that would do it.  The biggest question is how fast would it run?  Some of the orbits are very fast which means small time steps.  Those small time steps are meaningful within solar systems (did you want moons too?  Asteroids and comets?) but are just wasted computation time on a stellar scale.

I think what I'm saying is that you could probably make a supercomputer that would do it, but the simulation would be agonizingly slow.

[Austritistanian]

NASA's supercomputer

[tkulogo]

Just for some perspective humanity has only catalogued around .03% of the stars in our galaxy and maybe a billionth of the planets. To make matters worse 99% of the stars we've cataloged we know nothing besides the location in our sky, so we don't know distance, luminosity, temperature, mass, or age of almost all the stars we've recorded.

[Sumofluffy]

Well, if you want some really basic calculations. Just remember these are extremely rough calculations, and I mean really rough, but at the very least I should get the scale of how powerful a computer you'd need.

On my system, I have a gtx 970 and an i7 4970k. When I run the solar system, it sits at a stable 144 fps. When I have 2 solar systems, it drops to about 30 fps. Assuming that every solar system in the universe is on average identical to ours, then you'd need a computer about 150 billion times more powerful than mine to run at 30 fps to generate our galaxy (Just the solar systems) at the level of detail Universe Sandbox ² provides at 15 days per real-time second. This is assuming that the scaling of the fps drop is linear, too.

Putting that into perspective, you'll usually hear how our current computers are hundreds of millions of times faster than the supercomputers they used at NASA during the moon launch.

Even our fastest supercomputer at the moment of this post, the Sunway TaihuLight at 93 Petaflops, wouldn't be able to run a galaxy generated with Universe Sandbox ². If we assume that flops is the absolute way to measure computing power and that our computers and super computers work the same way (Which it isn't and they don't, but let's just assume it is), then my computer is about 5 teraflops, so in terms of raw calculation, the Sunway TaihuLight is only 186,000 times faster. Nowhere near enough.

[Planetoid_75]

I have a 2017 iMac with Intel Core i7 Quad Core 3.6 GHz 7th generation, with 32 GB of RAM and Radeon Pro 560 4 GB Video RAM.  I think you would need a computer with more than 10¹⁵ times my current settings to simulate an entire galaxy full of stars. In my estimation, to simulate an entire universe full of galaxies and stars, you would need more than 10¹⁰¹²⁰ times our current supercomputer's speeds to run an entire universe.