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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).


Sep
10
comment Is it possible to determine whether distant galaxies are gravitationally bound
Let's not forget Tully-Fisher and Faber-Jackson. I hesitate to make this an answer though - I have no experience with the practical method of determining cluster membership given incomplete data.
Sep
8
comment Equation regarding the Riemann tensor in the Cartan formalism
I don't know if you are intentionally overstacking the indices on the Riemann tensor, but in case not: $R^{\alpha\beta}{}_{\nu\rho}$ can be hacked R^{\alpha\beta}{}_{\nu\rho} or {R^{\alpha\beta}}_{\nu\rho}. The former risks breaking across line wraps, and the latter is semantically wrong, but they work in a pinch.
Sep
8
comment Is data which rides on the carrier frequency dangerous?
-1 For "substantial danger": You can strap your cell phone or wireless router to your head and crank up the transmission all you want - absolutely nothing will happen.
Sep
8
comment Measuring more accurately the distance of remote galaxies
A very good question about a subtle issue. I think this touches on the oft-neglected aspect of cosmology (which would certainly be an appropriate tag here) that homogeneity/isotropy kicks in only at a certain scale, but I'm not confident enough to turn such into an answer. By the way, there's no fixed definition of "group" - just whatever algorithm you choose to employ.
Sep
7
comment Riemann curvature tensor notation in Wald
Since it appears you're just starting in GR, might I suggest you start with a different book? Wald is great for some things, but, for instance, it was only the third GR text I read in depth. If it had been my first, I'm sure I would have gotten hung up on the notation and missed the physics he was trying to convey.
Sep
7
comment (Why) is dumping liquid nitrogen on your head dangerous?
AHHHHHHH!!!! Don't do that. Leidenfrost protects you from a drop of LN2. That was incredibly risky and utterly irresponsible to demonstrate as part of a viral trend.
Sep
6
comment The study of the physical universe
Obligatory
Sep
5
comment How can interstellar space have a temperature of 2-3K?
@Phaptitude There are hundreds of millions of CMB photons per cubic meter. As for how they have a temperature, that deserves a longer answer (which I'll bet has been asked here before). The key phrase to look up is "blackbody radiation."
Sep
5
comment How can interstellar space have a temperature of 2-3K?
@BowlOfRed For an ideal gas of particles with no (or no excited) internal degrees of freedom, temperature is identical to average kinetic energy.
Sep
4
comment Motorbike with parachute vs normal skydive
@Johan "it is not lethal to glide on the tarmac at 200km/h" - citation very much needed.
Sep
3
comment Why group velocity represents energy or information transmission? What relation between phase velocity and special relativity
It is a common misconception that group velocity represents information transmission. It does not. It is perfectly reasonable to have superluminal group velocities.
Sep
2
comment Gravitational binding energy of a white dwarf at Chandrasekhar limit?
@akrasia I don't know where they get that number from, because every supernova researcher has a different opinion on Type Ia progenitors. It may be that most are double degenerate, it may be that none are. A lot more work needs to be done.
Sep
2
comment Einstein and the existence of Black Holes
Note that other big names in the field were also hesitant to accept black holes. See Wikipedia's history of the Chandrasekhar limit for how Eddington convinced everyone Chandrasekhar's argument must somehow be wrong.
Sep
2
comment Gravitational binding energy of a white dwarf at Chandrasekhar limit?
Very good question. Clearly one needs a better theory than the basic Chandrasekhar arguments. Kippenhahn and Weigert mention that pycnonuclear reactions and inverse $\beta$ decay become important at the high-mass end, and they refer to Hamada and Salpeter for more details. Perhaps someone can pick up here and make a full answer...
Sep
2
comment Mass of small fluctuation around vacuum
Hi milli, and welcome to Physics Stackexchange! Just so you know, we support MathJax for LaTeX-like formatting so you don't have to include equations as images. Most basic stuff is supported, as covered in this extensive guide.
Sep
1
comment Dark matter a medium for light propagation
Things can only propagate stuff they interact with. Dark matter's sole reason for existing is that we see evidence of stuff that interacts via gravity and essentially nothing else. So it can have gravitational effects, but e.g. gravitational waves, like light, don't need a medium to propagate in.
Aug
31
comment What does the notation $\Psi_k/(\Psi_k,\Psi_k)^{1/2} $ mean?
In math, $(\cdot, \cdot)$ is linear in the first argument and conjugate linear in the second, whereas in modern physics $\langle \cdot | \cdot \rangle$ is linear in the second argument. I wonder which one Weinberg (and Karolyhazy) use.
Aug
30
comment Solar stills with Wine
@namehere that's a good question I would hope an actual chemist or chemical engineer would calculate for me, but I'll think about it...
Aug
30
comment What is the meaning of this “let there be light” joke?
Related: physics.stackexchange.com/q/51753
Aug
30
comment Scientists observe the laws of the physics but, Where do they come from?
For the record, I don't think this is a bad question per se, nor that scientists shouldn't give it some thought now and again. It's just that, for better or for worse, physics proper decoupled from metaphysics 250 years ago, and this question certainly belongs in the latter category. Have a look at Philosophy.