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463111
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location Princeton, NJ
age 26
visits member for 3 years, 1 month
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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.


Aug
6
comment Signal-to-Noise ratio given pixel intensity map
Indeed there's a certain amount of subjectivity to defining S/N. Since the pixel value is necessarily S+N, knowing S/N perfectly is equivalent to being able to perfectly remove the noise.
Aug
6
comment What planets are visible to the naked eye from Mars?
I wonder if proximity pushes Ceres into the visible range.
Aug
3
comment Are Hubble Telescope Images in true color?
That explanation for "why are the original images in black and white" seems a bit odd. CCDs are inherently greyscale, and the as-yet-unattained holy grail of scientific imaging is for every pixel to report not just intensity but wavelength for every photon. As the previous paragraph alludes to, all digital cameras are also greyscale, but the camera automatically combines the filtered images according to the manufacturer's preset approximation for human vision.
Aug
2
comment How does the mathematical definition of drag reduce to Stokes or form drag?
That $C_\mathrm{d} \to 1$ as $\mathrm{Re} \to \infty$ is no surprise, since we are then in the ballistic regime and the fluid can be modeled as a collection of non-self-interacting particles reflecting off the object.
Aug
1
comment Is there a phase transition for degenerate matter?
The neutron star evidence you refer to is presumably Cas A (are there others?). Plots like the inset in Figure 3 of Shternin et al make a good case for superfluidity (insofar as one believes the models).
Jul
30
comment Books of dynamo theory
Dynamos definitely require magnetohydrodynamics and might need a bit of plasma physics too. Also you should have a sense of how stability analysis works for dynamical systems.
Jul
28
comment How can I add dark matter to my $N$-body simulation?
What do your normal matter particles do other than gravitate? If the answer is "nothing," then they are not terribly different from dark matter. On large scales where everything is like a fluid, the only difference between dark and normal matter is that the dark matter is pressureless.
Jul
27
comment Why do we see brown light?
The vast majority of colors are not on the rainbow. If you think they are, this is a cultural/linguistic artifact. We don't want 16 million color words, just 20 or so at most. This divides up color space arbitrarily, and some of the regions ("redish," "greenish," etc.) include colors in the rainbow, whereas others ("brownish," "tealish") do not.
Jul
27
comment Why does a free-falling body experience no force despite accelerating?
The last three paragraphs really get to the heart of the issue. There is a force iff there is deviation from a geodesic. In a "good" coordinate system (Riemann normal? Fermi normal? I forget which) deviation from a geodesic looks like a classical acceleration. But many coordinate systems are accelerated with respect to this good one.
Jul
26
comment Gravitational redshift in a general stationary metric
It's interesting that the formula can give a finite, believable result, even in cases where a stationary observer is unphysical (e.g. inside the ergosphere).
Jul
25
comment How can the orbit of Jupiter's moons be used to calculate the speed of light?
@Javier There is also a relativistic effect like what you mention, but it is negligible here since Earth only orbits at 0.0001c.
Jul
25
comment Is there a limit to telescope resolution?
For a distance of 1400 ly, you would need a telescope of diameter (or at least separation between furthest components) of 1 ly in order to resolve 1 mm print in visible light. It's not clear that building a telescope of size 1 ly is any more difficult than traveling 1400 ly and just asking for a copy of the 452b Gazette.
Jul
25
comment Is there a limit to telescope resolution?
possible duplicate of Is there a limit to the resolving power of a mirror telescope?
Jul
24
comment Is time infinite?
This is somewhere between metaphysics and ontology, both of which are considered philosophy rather than physics in this day and age. Note too that there are some wild leaps in your logic from premises to conclusions. Ideally studying philosophy (as opposed to just thinking about it on your own) would help to train your thinking to be more careful.
Jul
24
comment Klein-Gordon equation and wave velocity
I feel insofar as this is about the Klein-Gordan equation, it is not a duplicate of either option. Of course, if the question is just generally about superluminal wave velocities, it is sort of a duplicate. Note that both phase and group velocities can be superluminal, as neither correspond to anything other than a (possibly prearranged) pattern moving.
Jul
23
comment Speed of light and current dimensions of the universe
possible duplicate of Why is the observable universe so big?
Jul
22
comment Why chewing a battery increases its power?
Wait, a battery wasn't working so you tried to eat it? Did something get lost in translation?
Jul
22
comment Help identifying a Fusion approach
@WetSavannaAnimal Perhaps, though the line "leave behind only minimal radiation that would dissipate in a few hours" strikes me as describing neutron radiation. (On the side, I'm trying to imagine how the Moon could possibly be the most cost-effective source of ${}^3$He.)
Jul
21
comment When is Einstein summation implied by Lorentz indices?
Where does dimensional analysis come in? Each of the terms in $A^\mu B_\mu$ has the same dimension (since they are added), so dimension can't tell you whether the author blundered and meant $A^0 B_0$.
Jul
21
comment Could a vacuum airship be possible?
possible duplicate of Beryllium Vacuum Sphere Boat/Aircraft