20,515 reputation
44581
bio website
location Princeton, NJ
age 25
visits member for 2 years, 2 months
seen 3 hours ago

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


Aug
27
comment WHY does the “order” of a differential equation = number of “energy storage” elements in a system?
For math, we have MathJax to imitate LaTeX. For a more thorough guide as to what you can do with it, see here. As for the low activity on this question, I suspect it has to do with different ways of communicating between physics and engineering. Your question is intriguing (and I'm digesting your answer), but I must say I never deal with Laplace transforms, nor do I think in terms of energy storage units.
Aug
26
comment What is the metric of Vaidya black-hole horizon?
...or the induced metric on the surface $r=2m$?
Aug
26
comment Why does a green glass block more UVA/B rays than a blue one?
Indeed since rubies' red also comes from chromium impurities, environment probably plays a very large role in how it acts.
Aug
26
comment Having trouble weighing the sun
Other side note: Historically, it was very easy to determine relative distances $R$ and velocities $v$ in the solar system. It was much harder but doable to get absolute values for $R$ and $v$. It was harder still to get $GM_\odot$ independently, so really we know this last quantity only because of applying the formula you have. (And the most difficult measurement of all is $G$ itself, which is why we know $GM_\odot$ better than $M_\odot$.)
Aug
26
comment Having trouble weighing the sun
Side note: the relation you cited is for circular orbits (a good approximation for many stars in the galaxy) orbiting a spherically symmetric mass. That many galaxies look like disks should give you pause when applying the formula.
Aug
25
comment How can I calculate the center of an object relative to a focal point and a moving observer?
I'm not sure about programming per se. This is more about rendering, and the math behind (one particular choice of) artistic technique. gamedev.stackexchange.com seems more appropriate.
Aug
25
comment The charm of the gyroscope
Conservation laws are never mechanisms. But if applying the law yields a unique solution to the problem (which it does here, where the question is "How fast will she spin after torquing the wheel?"), then you know that solution has to be the right one.
Aug
25
comment Convention in physics for [],{} and operators (QM)
Just a comment because I have no idea what {} means. (1) -> (2) and (3) -> (4) is just the difference between a function and a function evaluated at a given input. (4) is an operator-valued (hat on $H$) function depending on non-operator parameter $\{R\}$, applied to $r$; contrast this with (5), which is takes operators as parameters (hat on $\{R\}$) and inputs (hat on $r$) and is either a scalar value (no hat on $H$) or inherits its value from its inputs (think programming in languages with malleable typing rules).
Aug
25
comment spacecraft thrust through means other than liquid propellants
That quantum fluctuation propulsion violates the most cherished laws of physics, and no respectable scientist believes it has any hope of being possible. That entire NASA division is dedicated to defrauding the public with whimsical fantasies derived from science fiction that we know can never work.
Aug
24
comment geodesic conjugate points
Huh - every source I've ever read would call that an instance of the Raychaudhuri equation, and google returns scarce few hits for RNP equation outside of finance. So who would tack on an N and a P to R? Ah, Penrose himself apparently.
Aug
24
comment The Thermodynamic Limit of Quantum Statistical Mechanics & Interpretation of Quantum Field Theory
"is way too mathematically advanced for 99% of philosophers to understand" - A fair number of the philosophers I've learned from had graduate degrees in pure mathematics. And honestly, 99% of professional physicists don't know what a C*-algebra is, nor have they ever touched non-commutative geometry. Don't be so quick to assume a whole group of people is entirely stupid or incompetent.
Aug
24
comment How powerful would a series of rail guns or bombs need to be to destabilize a hurricane?
What does it mean to destabilize a hurricane? Storms are driven by gradients (in temperature or humidity or better yet entropy) between different altitudes and/or latitudes. When the gradients are steep enough, the atmosphere becomes unstable in that small flows build on themselves. Getting rid of storms amounts to either engineering a planet-wide method of calm equilibration (giant metal pipes everywhere?), or just doing away with the gradient altogether (permanently melt the ice caps perhaps?).
Aug
24
comment A Sphere of Black Holes
@Blackbody The actual definition of "event horizon" is the boundary you cannot cross to get to the rest of the universe, ever. And it has no effect other than this - you can't know you are crossing an event horizon from any local experiment, even in principle. Thus in a very real sense there is only ever an "outer" event horizon. The "inner" ones you're picturing don't demarcate anything of importance, and in fact wouldn't exist according to the definition by the time the outer one formed.
Aug
24
comment How and under what principle are measurements made at quantum level?
This really is a bit broad and non-specific. What kind of measurements are you talking about? What does "quantum level" mean? At some level quantum mechanics is everywhere, and we observe predictions of quantum theory the same way we observe any other experiments - with instruments designed to aid our senses. For example, a Stern–Gerlach apparatus is at its heart just a beam of silver atoms and a magnet. Classical physics predicts one pattern on the detector, quantum mechanics predicts another.
Aug
23
comment Presence of planets in Milky Way and other galaxies
Well, it's not like we can see M-dwarfs very well in the Magellanic clouds (or even in most of our own galaxy). And certainly we can't see fainter things like white dwarfs.
Aug
22
comment Why doesn't the light from galaxies appear stretched?
This is a good question, but the big bang/inflation aspect is something of a confusing tangent. Galaxies had not formed by the time of recombination, and in fact most images of galaxies are from at most a few billion light years away.
Aug
20
comment Alcubierre drive and inertia.
Realize that you are asking for details regarding a physically impossible device. If you allow for the existence of a warp bubble, you may as well import anything else you desire from science fiction to help alter its properties.
Aug
15
comment How did Fizeau make his famous speed-of-light experiment?
Hopefully the laser came with some specs. Not just power output (btw you were lucky to get an actual high power one from amazon - most of the lasers online are many times worse than advertised) but also "beam divergence" or something similar. That could at least help in diagnosing why your particular setup didn't work.
Aug
15
comment How accurate are constants in cgs units?
I would think that for most major solar system bodies, $GM$ is known far better than $G$ or $M$, and this isn't going to change any time soon. The only non-$GM$ ways of getting mass I can think of are compositional inference and shoving the thing with a known force.
Aug
14
comment Wouldn't the presence of dark matter slow the expansion of the universe?
@allanemery be careful about jumping to hypotheses like that. The "dark" in both is a complete coincidence of naming. And moreover the ratio of dark matter to dark energy changes with the scale of the universe.