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location Austin, TX
age 34
visits member for 3 years, 11 months
seen 43 mins ago

I am a Ph.D. general relativist working as a software engineer. I like to still go and do physics as a hobby, and to keep up my skill and knowledge.


17h
comment What would happen if Newton's Cradle was made of other geometrical objects rather than spheres?
I could see making them cubes would increase the chance that spurious motion parallel to the direction of the surface could cause energy loss due to friction.
1d
comment How much further can I throw a baseball (148 grams) than a grenade (453 grams)?
If nothing else, I would think that another competing model would be "constant torque applied to 'arm plus projectile' system" and your constant of proportionality would be something like $m_{a} + 3 m_{p}$ (assuming that the arm is a uniform rod)
2d
comment Importance of periodic orbits
@user929304: a proper derivation of that result is a whole chapter of the Landau/Lifschitz classical mechanics book. I refer you to there if you're interested. And really, if you're interested in questions like this, you should already have the Landau/Lifschitz book.
2d
comment Importance of periodic orbits
NOte, however, that the only central forces of the form $F = -kr^{n}$ that have stable orbits are those that have $n = 1 $ or $-2$
Oct
27
comment Are there models/simulations of antigravitational antimatter-galaxies?
@TobiasKienzler: that's actually the point. Their gravitational potential energy would have the opposite sign to the particles, so moving the antiparticle from point A to point B would give you an exactly opposite amount of energy from moving the particle from point a to point B.
Oct
25
comment Is Japan truly the “Land of the Rising Sun”?
Beyond this, the continents are younger than the earth -- the sun was rising before the continents existed.
Oct
24
comment Gravitation Field inside hollow sphere
You're not integrating over the sphere, you're integrating over the charge distribution, which means you're integrating over the shell.
Oct
24
comment Black hole “no hair” theorem
After all, a straight wire with an oscillating current is axisymmetric, but it will also radiate EM radiation.
Oct
24
comment Black hole “no hair” theorem
@RobJeffries: there's more to the no-hair theorem, certainly, because angular momentum muddies the whole thing. There is no strong theorem like this when you relax spherical symmetry to axisymmetry, which you need to do to consider spin.
Oct
24
comment Why are extra dimensions necessary?
@TrevorAlexander: Well, the idea would be that the universe would be shaped like a tiny cylinder or something like that in those directions, so the total volume of the space in those directions would be vanishingly small.
Oct
23
comment No length contraction!
The tape will be moving and will therefore length contract.
Oct
22
comment Why are extra dimensions necessary?
@TrevorAlexander: the idea would be that the extra dimensions would be spatial dimensions, just in directions we can't move in.
Oct
22
comment Drift Speed and Current in Two Different Inertial Frames
Well, you could argue that you get a spin on an electron due to relativity. YOu certainly need relativity to get the relationship between the electron spin and the magnitude of it's magnetic moment correct.
Oct
22
comment Gravity - Force or Result?
@CuriousOne: I have seen a quantum theory of sound -- the phonon theory that they use in solid state. I guess it's possible that gravitational waves and the metric tensor could be something like soliton states in some bigger theory, but I think we can both agree that that is probably not the most likely outcomes.
Oct
21
comment Gravity - Force or Result?
@CuriousOne: not everyone thinks that gravtons exist? Who doesn't think that gravitational waves should have quanta in some fundamental theory? There's no known way to couple classical degrees of freedom to quantum degrees of freedom, and the black hole entropy stuff is screaming that there needs to be some sort of quantization of gravity.
Oct
20
comment Why do we believe in a “force” driven universe?
They're likely to be harsher on physicsoverflow, but feel free to give it a try. It's a much slower place over there.
Oct
20
comment Why do we believe in a “force” driven universe?
@AlistairRiddoch: we're not invested in these paradigms, so much as they work, and they explain a ton of unexpected things. In each instance, they're actually simpler than what came before, as you can really easily see formulating electrodynamics with and without special relativity, for instance.
Oct
20
comment Understanding fields and their correlation to forces
@Key: fundamentally, all magnetic forces are due to the Lorentz force on moving charges. Even ferromagnets have their roots in the spinning of charged electrons.
Oct
16
comment How much energy does a photon need to form a black hole?
@CountIblis: LQG quantizes area at the planck scale, so I would assume that you lose Lorentz invariance at similar length scales.
Oct
16
comment How much energy does a photon need to form a black hole?
@21joanna12: there is no answer in LQG yet. The theory, as it currently exists, is a theory of gravity alone. There is no matter content in it, and thus, no concept of "a photon" in a full, quantum sense.