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location Princeton, NJ
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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.


Feb
26
comment What is the reasoning behind the idea that light cannot escape from a black hole?
@SeñorO No, I'm sorry, Jim is right. A Newtonian black hole would be qualitatively different from a GR one. In particular, you could escape from inside a Newtonian black hole without ever going faster than light, just as you can escape from Earth without ever reaching escape velocity. And light emitted from inside a Newtonian black hole would leave, go a long distance away, and eventually turn around and come back.
Feb
26
comment Is there a limit as to how fast a black hole can grow?
Good answer. I would just note that "speculative" means that we aren't sure which details are right, not that we have no good ideas. Overcoming Eddington is easy in principle -- just break spherical symmetry, letting matter flow inward in some places and radiation flow outward elsewhere. It's not like accretion disks are spherically symmetric anyway.
Feb
26
comment Does placing a cold bottle next to an incubator cool the incubator through convection or radiation?
And this exactly the same reason one feels "the same" indoors in winter only with a higher air temperature than in summer -- the walls are colder, so there is less heat than usual coming from radiation.
Feb
26
comment Computing the gravitational force on a planet in a particular system
Yes, that formula should work fine.
Feb
25
comment Is it valid to apply Einstein's Relativity to scenarios involving expansion of space?
That would only hold under certain definitions of how time for us relates to time for them. I should point out that any definition of time that had it flowing at a different rate for distant galaxies is rather anthropocentric. Why should we be at the center of the universe?
Feb
25
comment Computing the gravitational force on a planet in a particular system
In addition to the chaos, though, there's a question of if the system is bound. The potential energy between a pair of objects is $-Gm_im_j/r$. Sum this over all pairs. The kinetic energy for each object is $m_iv_i^2/2$. Sum this over all objects. If the total energy is positive, the system is unbound and at least one object will fly off to infinity, never to return.
Feb
25
comment Computing the gravitational force on a planet in a particular system
The trigonometry vanishes here because of relations like $\cos(\tan^{-1}(\Delta y/\Delta x)) = \Delta x / \sqrt(\Delta x^2+\Delta y^2). As for the orbits, they will definitely be nothing like circles. For one, you haven't included a central star dominating the gravity. For another, the initial velocities aren't pointing along circular paths around the origin (where the star presumably would be). Really, this setup is more of a miniature globular cluster than a solar system.
Feb
24
comment Physical examples where changing the order of limits yields wrong result
One such situation came up in chat recently. DanielSank described an LC circuit ladder, where any finite segment has an imaginary impedance, but the whole thing seems to have a real impedance. The resolution is that there is another limit involved in calculating these quantities, and the order of limits (response time, number of segments) is tacitly switched between the two cases.
Feb
23
comment When heat is applied to the top of a stack of pennies, why does the bottom penny melt first?
@CuriousProgrammer See my above comment. It's illegal as a profit-making enterprise on a large scale, but not for individuals doing frivolous things on a small scale.
Feb
23
comment When heat is applied to the top of a stack of pennies, why does the bottom penny melt first?
@WernerCD See this pdf: "The prohibition contained in § 82.1 against the treatment of 5-cent coins and one-cent coins shall not apply to the treatment of these coins for educational, amusement, novelty, jewelry, and similar purposes as long as the volumes treated and the nature of the treatment makes it clear that such treatment is not intended as a means by which to profit solely from the value of the metal content of the coins." "Treatment" is defined in 82.3.e to include smelting.
Feb
22
comment When heat is applied to the top of a stack of pennies, why does the bottom penny melt first?
Those are US pennies, and in the US destroying coins (as opposed to bills) is only illegal if intended for fraud. You can't mint your own coins, or debase the currency by taking a little bit of the metal out of a coin, but you can completely destroy the coins.
Feb
20
comment Why does the electric field escape a black hole?
Related, though I wouldn't call it an exact duplicate: physics.stackexchange.com/q/937
Feb
17
comment What Planck units are limits?
And the Planck mass is somewhere around the mass of a single biological cell, just going to show that Planck units are mostly numerology.
Feb
16
comment X-ray pulse more powerful than national grid?
@JoshuaBenabou These facilities store energy slowly over time, for instance in large capacitors, and then release it all at once. This way the average power in the long run (average includes long periods of time when the laser is not firing) can't exceed the grid supply, but the instantaneous power can.
Feb
16
comment How can a gas giant be about the same size but six times more massive than Jupiter?
@Aron Fusion requires high temperatures, and the Chandrasekhar mass is 1.4 solar masses. Neither is applicable in the case of anything reasonably called a planet, whereas degeneracy in fact is important starting around a Jupiter mass.
Feb
14
comment Molecular simulation applied to astrobiology
Honestly, astrobiology is just hypothetical/theoretical Biology. Organic molecules and cell membranes function the same no matter where they are in the universe, and it's not like astronomers or rocket engineers are simulating them.
Feb
12
comment Is there a phase transition between a gas and plasma?
Hi mike, and welcome to Physics Stackexchange! This isn't a bad answer, but you may want to break up long posts into more than one paragraph for readability. Also, you can typeset math with Latex-style MathJax on this site. (If you're not familiar with the notation, here is a very complete reference.)
Feb
11
comment Would an Alcubierre drive actually allow FTL travel?
possible duplicate of How does "warp drive" not violate Special Relativity causality constraints? (see Jerry Schirmer's answer, which is the clearest and is quite correct)
Feb
10
comment Cosmology: proper evolution of energy density ratios with time?
@Kagaratsch Yes, see the edit.
Feb
9
comment Intuitive understanding of Lagrange point L3
For the first equation, the exact formula (for circular geometry) would have an extra $r/R$ multiplying the RHS, since you really want to set the gravitational acceleration equal to the centripetal acceleration at $r$ rather than $R$, keeping angular velocity constant. Not that this changes the approximation.