29,790 reputation
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.


Jun
30
comment Why does the speed of the propellant limit the speed of a space ship in open space?
@this If you created photons, I assure you you had a source of fuel that lost mass in the process. Also, for all intents and purposes, antimatter-powered anything is science fiction.
Jun
30
comment Why aren't all photons virtual particles even in the “vacuum” of empty space?
Possible duplicate of Does radio use virtual photons? Or at least the title and last sentence are. The whole middle paragraph seems to be on a completely separate topic, which is a duplicate of John Rennie's link.
Jun
29
comment Driving car with (almost) the speed of the light and switch the headlights on
possible duplicate of Double light speed
Jun
28
comment What does the size of an object have to do with it's color?
Hi Arul, could you specify whether you asking "how does an object's size relate to color in the normal sense?" or "how does an object's size relate to color in the quark sense?" or "what's the difference between normal color and quark color?"
Jun
28
comment When we look in different directions in the universe how do we know we're not seeing the same thing?
Your impression of the Big Bang has problems. There is no point at which it occurred. Really. Seriously. But I don't see what that has to do with your main question anyway.
Jun
27
comment What does a wing do that an engine can't?
So as I read the OP, the question is "why don't we just angle the engines to begin with?" You've answered "Given that the engines are pointed perfectly horizontally, large wings give us the needed lift with the least amount of drag." But why not angle the engine so as to not need lift at all? This is after all similar to what a helicopter does (if we think of its blades as an engine).
Jun
27
comment What does a wing do that an engine can't?
This explains why we use planes instead of helicopters, but isn't the OP asking why we use planes instead of rockets?
Jun
27
comment Is a plasma a distinct phase of matter?
Just a nitpick - can't we avoid the liquid-vapor phase transition in e.g. water by going around the critical point in temperature-pressure space? So if avoidance of a proper phase transition is sufficient to declare plasma the same phase as gas, doesn't that also mean liquid is part of that same phase? This is probably pushing the definition further than it was intended, but it's something to think about.
Jun
27
comment Is a plasma a distinct phase of matter?
I don't think the time ordering is the issue here - I'm sure everyone agrees you can go both ways. Also, while the universe started out as a plasma, most of the material became neutral gas at recombination a few hundred thousand years after the big bang. It was then reionized a few hundred million years later.
Jun
27
comment Quantum Mechanics or Classical Mechanics?
Since when is QM used to study galaxies or exoplanets?
Jun
26
comment Can a difference in the “speed of time” introduce acceleration?
Flat spacetime in non-Cartesian coordinates also has nonzero Chrisoffel symbols. For example in spherical coordinates, 9 of the 64 symbols are nonzero. Not that this thwarts the argument.
Jun
26
comment Euler equation with single state variables
Hi Thomas, and welcome to Physics Stackexchange! I fixed up the formatting of your equations, but please make sure I got it right. In particular, I think you were missing the time derivative, and also standard notation is that $\vec{v} = (v_1, v_2, v_3)$ (note the lack of arrows over the components).
Jun
23
comment Terminologies for moment of inertia
Perhaps @TadeusPrastowo wants the words "moments of inertia about principle axes" for $I_2$ and $I_3$?
Jun
23
comment Why does evaporation take place?
Side note: 25 degrees is not 1/4 of 100 degrees unless you are using a temperature scale zeroed at absolute 0. You are never allowed to use multiplication or division with temperatures unless they are absolute.
Jun
23
comment Why is the intensity of Hawking radiation dependent on the size of the black hole it comes from?
That's the basic idea. For more on how Hawking radiation (under a different name) can depend on your state of acceleration, see the Unruh effect.
Jun
23
comment What happens if the earth stops rotating?
Hi aPhysicist, and welcome to Physice Stackexchange! Note that we have Latex-style formatting enabled, so for instance $1300\ \mathrm{W/m^2}$ renders as "$1300\ \mathrm{W/m^2}$," which can improve readability.
Jun
23
comment Determine $p_x$ from $[x,p_x]=i\hbar $
possible duplicate of Does the canonical commutation relation fix the form of the momentum operator?
Jun
22
comment Why is the intensity of Hawking radiation dependent on the size of the black hole it comes from?
Not a direct answer, but your intuition started to go wrong way in the beginning when you implicitly assumed "event horizon" was a local concept. Event horizons have nothing to do with escape velocity, and everything to do with the global causal structure of spacetime. In other words, one cannot look at a small patch of spacetime and conclude it is part of an event horizon. So the horizon in some sense "knows" about the mass of the BH.
Jun
21
comment Why does my gravity simulation do this?
Yes! Leapfrog! +1. I plug this every chance I get. (Of course that fixes problems the OP hasn't encountered yet; force softening is more important here.)
Jun
21
comment Why does my gravity simulation do this?
Unless I'm misremembering, standard Runge-Kutta, as ubiquitous as it is, isn't symplectic. So it's not as unconditionally unstable as forward-Euler, but it's still not very good for long-term N-body simulations.