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I am a graduate student studying astrophysics at Princeton. I received my bachelor's in physics and mathematics from Caltech (2011).

My primary interest is in general relativistic magnetohydrodynamics simulations of black hole accretion.


Dec
13
comment Where did the energy released due to gravitational binding energy of the Earth go?
"the current internal energy contributes positive mass-energy to the Earth" -- sure, but since the rest-mass energy of Earth is over $5\times10^{41}\ \mathrm{J}$, I'd say this is pretty negligible.
Dec
13
comment Solar spectrum units
Something to ponder: what would the area under the curve represent in the two cases? (Hint: only one case makes any sense.)
Dec
13
comment Greiner or Landau for Math major student?
Are you looking to understand physical principles, or are you looking to have exposure to useful equations in physics? These are different things.
Dec
12
comment Would it be possible to “recycle” nuclear warheads into nuclear energy?
The world isn't powered by nuclear energy because (1) people are ignorantly afraid of the safest power source known to humanity, and (2) it's not overwhelmingly price competitive to operate nuclear plants as opposed to other plants. The availability of fuel has little to do with the politics and economics of the situation, especially since there's plenty of fuel that doesn't come from nation-states voluntarily surrendering their military investment.
Dec
12
comment How would night sky look like if the speed of light was infinite?
@pentane solid angle goes down as the square, which is what Tim S. surely meant.
Dec
12
comment How would night sky look like if the speed of light was infinite?
@Peteris Opaque things would block light, but then they would heat up until they were the same temperature as stellar surfaces and thus they would glow just as bright. In such a universe opaque objects essentially delay the inevitable, slowing down the effective speed of light (even if it is infinite otherwise). So I'm assuming either the age of the universe is larger than the thermal equilibrium time, or simply that we refer to the effective $c$ when we say it is infinite.
Dec
12
comment How would night sky look like if the speed of light was infinite?
@DavidRose It doesn't. The two bullets together are necessary and sufficient for Olbers paradox to manifest. The speed of light only enters the second bullet.
Dec
12
comment How would night sky look like if the speed of light was infinite?
@RobJeffries I don't think that's really even a valid question. Of course no "actual" physics works with infinite $c$. For any scenario, I can find a reference frame where finite $c$ and infinite $c$ differ arbitrarily much in their predictions. But at the same time, we don't tell students "don't bother with classical mechanics, since the errors in your results are unboundedly large in appropriately chosen formulations of the problem." Exploring the implications of a working theory that doesn't try to consistently explain everything in the universe is still physics.
Dec
12
comment How would night sky look like if the speed of light was infinite?
To everyone voting to close as non-mainstream, I remind that this is exactly the cosmology of Newton's time.
Dec
12
comment Difference between astronomy and astrophysics
See also the tag wikis for astronomy and astrophysics. (I personally edited much of that info in, but I think they do a fair job of representing the field's opinions. But really the terms are often interchangeable.)
Dec
12
comment field solutions for covariant derivative of vector field constrained to zero
Interesting question. Well $\nabla_\mu A_\nu$ is halfway to the left-hand side of the Killing equation, so any solutions are trivially Killing fields. It also looks like a tensor that comes up in some forms of the geodesic deviation equation. And if $n$ is geodesic and taken to be the unit normal vector field of a family of hypersurfaces, then $\nabla_\mu n_\nu$ comprise the second fundamental forms of those surfaces. I wish I could say something more definitive.
Dec
12
comment Plants and Quantum Mechanics!
@TAbraham Insisting on path integrals seems rather... strange. Path integrals are a tool for calculating probabilities of various processes happening, nothing more, and they get the same results as any other method. If you are thinking they integrate over the path the photon takes... then I fear there is a more fundamental misunderstanding about what path integrals are. Note that path integrals are advanced QM -- many universities don't even teach them to undergrads.
Dec
11
comment How far away must a galaxy be for its light never to reach us due to the expansion of the universe?
(And since pretty much every astro paper is open access, at least after 1 year, there's no reason not to link to the nicely polished final version rather than the oft poorly formatted and error-prone preprint.)
Dec
11
comment How far away must a galaxy be for its light never to reach us due to the expansion of the universe?
It's probably good practice to link to arxiv abstract pages rather than direct to PDFs -- this way people don't accidentally download large files, and there is more readily available metadata. Actually, in astro, links to adsabs.harvard.edu are just as good (see Gott et al. and Davis & Lineweaver), especially since they link to not only the arxiv versions but also the final publications, e.g. here
Dec
11
comment How far away must a galaxy be for its light never to reach us due to the expansion of the universe?
You know, if this question gets closed as duplicate, you should consider migrating (deleting and reposting) to the duplicate (or just posting an answer there, not sure how frowned-upon posting dupe answers is), since this is the correct answer, unlike much of what's posted on the other thread.
Dec
10
comment How can comets have sand dunes without atmospheric erosion?
possible duplicate of What mechanism is responsible for the creation of these dunes on Comet 67P/Churyumov-Gerasimenko? Not that we have definitive answers there, but it is the same question.
Dec
10
comment From affine space to a manifold?
$\lambda$ is introduced as $\mathcal{R}\times\mathcal{R}\to\mathcal{V}$, then it becomes $M\times\mathcal{V}\to\mathcal{V}$ in property 1, then it is $M\times(\mathcal{V}?)\to M$ in property 2.
Dec
9
comment What happens in the twin paradox if the ship doesn't return?
Also we receive time signals from the satellites, not the other way around, so even without gravity and acceleration there is still a broken symmetry.
Dec
9
comment Shape of accretion disk surrounding the black hole in Interstellar (film)
@hello_there_andy Alas I don't know of any. Astronomy is particularly fluid/unpredictable in its definitions -- just look at whether Pluto counts as a planet. In fact, defining Pluto to not be a planet may be the only "official" definition the astronomy community has ever put forth.
Dec
9
comment Shape of accretion disk surrounding the black hole in Interstellar (film)
By the way, when I hear "debris disk" I tend to think more about the disk of material around a young star that's forming planets. In the context of stuff falling into a black hole it is more often called an "accretion disk."