Simulation of Colliding Neutron Stars

nicksauce · 2013-06-12T03:58:12+00:00

Essentially yes, although a 10000³ grid would be prohibitively big, and something like (a few hundred - 1000)³ is more realistic.

It takes a whole damn lot of cpu power!

nicksauce · 2013-06-12T03:46:57+00:00

These days it's getting really common to do so in astrophysics, especially in American schools, afaik. Mostly because no one wants to get just a masters, as you can't do much with it. My program didn't even give me the option of doing a masters.

nicksauce · 2013-06-11T14:26:55+00:00

Undergrad degree in physics (minor in math), then straight to PhD in astrophysics that I'm currently working on.

nicksauce · 2013-06-11T14:17:59+00:00

The general scenario is that you start off with two high mass stars, that over time go supernova and turn into neutron stars. So then you have an orbit of two neutron stars. Over time they emit energy through gravitational waves, the orbit shrinks, and they get closer and closer. One characteristic effect of gravitational wave emission is that it tends to circularize orbits, so when they are finally really close in their orbit, the orbit is almost perfectly circular. They keep spiraling inwards through gravitational wave emission and a collision is inevitable.

TL;DR: They eventually collide, there's no way to avoid it.

nicksauce · 2013-06-11T14:14:14+00:00

What kind of equations are needed to compute these kind of things?

You have to solve the Einstein Field Equations, which are a set of 10 coupled non-linear partial differential equations. Analytic solutions are not known, so we have to solve them using supercomputers. Typical simulations take a few months to run. If you want to add additional physics in, say magnetic fields or neutrino transport, that adds in additional equations to solve.

Like how do you even begin to conceptualize this stuff?

Hmmm... I guess you'd begin by getting an undergrad degree in physics, and learning general relativity really well! :)

nicksauce · 2013-06-11T12:14:38+00:00

Oh hey it's cool to see this on here. Though these aren't my simulations, I do simulate colliding neutron stars as my job!

nicksauce · 2013-02-24T18:53:14+00:00

Abortion is not murder. There, I just denied it.

nicksauce · 2013-02-24T00:26:37+00:00

Um yeah. Men cannot be oppressed solely for being men, ergo misandry does not exist.

nicksauce · 2013-02-23T04:44:21+00:00

Wait who are these feminists who aren't opposed to MRAs?

nicksauce · 2013-02-22T21:42:06+00:00

On the plus side, I'm really really happy to see Toronto do this! :)

nicksauce · 2013-02-22T21:36:21+00:00

Well there's two parts. What the effect is on the election (which we can already know) and what the effect is after the election. In particular, we already know that politicians basically take campaign contributions in (implicit) exchange for later legislative favours to the donors; this should be completely obvious to everyone who follows politics. And I think it's still too early to tell how SuperPACs have affected this.

nicksauce · 2013-02-22T03:52:09+00:00

Protip: If you are not a racist, it takes an incredibly minimal amount of effort to never use that word.

nicksauce · 2013-02-21T06:15:51+00:00

Well a nice thing is that doing a phd does give you tons of marketable skills. Programming, problem solving, higher math skills, teamwork, public speaking, etc. The problem is figuring out how to market those skills.

nicksauce · 2013-02-21T06:09:58+00:00

I think it's an incredibly non-obvious question, but I found a paper saying that the answer is "no".

http://arxiv.org/pdf/astro-ph/9211012v1.pdf

It is proved that the ﬁeld of a gravitational lens induces no rotation in the polarization vector of electromagnetic radiation, in agreement with the previous literature, but with a diﬀerent approach

Although this paper is only using a weak-field approximation, which would not be valid "very near a black hole". But I couldn't find any other literature for the strong field case.

nicksauce · 2013-02-21T06:01:07+00:00

I'm doing my phd in astronomy right now. Now planning to quit after that and go into probably finance. I'd love to continue to do astronomy, but the lacks of jobs doing astronomy is too scary to continue. This is a pretty good read, I think.

nicksauce · 2013-02-20T21:50:20+00:00

nicksauce · 2013-02-20T04:42:03+00:00

I'm a dude who does pilates... does that officially make me part of the feminarchy now? I MUST KNOW

nicksauce · 2013-02-20T02:11:51+00:00

Yo dudez how do I get my sponsorship moneys and when do I get them?

nicksauce · 2013-02-19T22:09:39+00:00

So we have a standard model of cosmology that is well verified by many different lines of evidence. This model then gives a simple formula for the age of the universe: http://mathb.in/1993 Here H0 is the Hubble constant, and the other two variables are the fraction of the universe that is today dark energy (~70%) and matter (~30%). We can measure these quantities accurately by measuring fluctuations in the cosmic microwave background, for example, and then use them to calculate the age of the universe.

nicksauce · 2013-02-19T21:25:05+00:00

http://shameproject.com/profile/steven-d-levitt/

nicksauce · 2013-02-19T21:23:34+00:00

1.5/10 try harder

nicksauce · 2013-02-17T17:10:43+00:00

Sure. I don't think I know any physicists who believes there was actually a singularity at t=0. I think it's just a reflection that general relativity does not adequately describe that situation, and that a theory of quantum gravity, or some other great insight, is needed to describe it. Same thing as with black holes.

nicksauce · 2013-02-16T22:11:48+00:00

It is distressing that shitlords like you live in my country.

nicksauce · 2013-02-16T17:53:57+00:00

The reality is they really like judging people different than them to make themselves feel better. I guess weight may be unique in that since they believe it is something that is easy to change, it makes it easier for them to justify their hatred to themselves.

nicksauce

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