Comments on: Nice Model.

By: The Asteroid Belt -- The Scientific Gamer The Scientific Gamer

The Asteroid Belt -- The Scientific Gamer The Scientific Gamer — Mon, 15 Oct 2012 12:27:04 +0000

[...] to eject the other ninety-nine percent. “Whatever happened” is overwhelmingly likely to be the chaotic gravitational interactions, peturbations and resonances of the solar system’s early years. For example, there’s lots of [...]

By: Sam

Sam — Mon, 20 Feb 2012 12:55:21 +0000

The general way that simulations work is that you throw more physics at a problem until you either a) get the right answer or b) realise that the program you’re using has some fatal flaw, and carry on anyway. Examples include particle hydrodynamics not capturing instabilities properly, Riemann-problem-based grid hydrodynamics inducing weird instabilities in grid-aligned shocks (that or being too dissipative), etc. That and the problem is inherently nonlinear, so it’s not like you can perfectly rebuild a real system like the Milky Way anyway.

The thing I think school physics doesn’t get across is how messy the real world is. Doing at least one non-linear system would be useful, since people come away with the idea that if you get better computers you can solve any problem, whereas the five-day forecast is actually about as good as we’ll ever get with weather forecasting, weather engineering aside.

(Incidentally, this is Gap Gen from Sekrit)

By: hentzau

hentzau — Fri, 17 Feb 2012 17:54:00 +0000

I shall have a look see. If it’s about how black holes are going to kill us all then I may be able to gin something up because that sort of thing really pisses me off.

By: slimbuk

slimbuk — Fri, 17 Feb 2012 13:07:17 +0000

hentzau, did you see the Horizon episode on Black holes last night? A post about that, rebuttal or otherwise would be awesome!

By: hentzau

hentzau — Fri, 17 Feb 2012 10:41:59 +0000

The detailed mechanics of how stars work is slightly above my pay grade (I do planet-scale stuff mostly) but I’m constantly amazed that we’ve even managed to work out the things we currently know about stars and star formation. After all it’s not like we can watch it happening in any meaningful sense, or cut open a star to see what’s going on inside. So, you know, there’s a lot of stuff astronomers don’t know, and since they have to figure things out with the scientific equivalent of guy wire and scotch tape it’s likely that understanding the fine detail of star and planet formation will remain beyond us for a good long time to come.

I think, anyway.

By: Sam

Sam — Fri, 17 Feb 2012 10:36:54 +0000

And yes, discs form because the gas has some angular momentum to begin with, so it collapses in the direction it has no rotational support. And sure, it’s not a “real” force, but whatever. Call it the Galilean invariant acceleration if you like. I tend to say that a disc is rotationally supported rather than using centrifugal force, but it’s just terminology.

By: Sam

Sam — Fri, 17 Feb 2012 10:31:08 +0000

I seriously need to learn more about star and planet formation. I don’t particularly know much about gas dynamics below a parsec (and above atmospheric scales, I guess). It’s becoming increasingly clear that astronomers don’t really know much about why there are certain numbers of stars of different sizes (i.e. what the stellar initial mass function is or why it’s that).

By: MD Game Pro

MD Game Pro — Thu, 16 Feb 2012 11:30:43 +0000

Impressive stuff!!! Mind blowing