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Apr
25
comment How is Mössbauer spectroscopy so resistant to thermal motion?
@CuriousOne: So you average the motion over about one half-life to estimate how much thermal effects smear things? Also it would be far-field (one-way) resonant coupling?
Apr
25
comment How is Mössbauer spectroscopy so resistant to thermal motion?
@Jon Custer The thermal motions are going to populate too many phonons to ever get stillness on the mm/s scale regardless of recoil. The odds that ~cm/s small-scale-collective motions all the way to ~100 m/s single-atom motions will lay dormant are very rare, yet we see ~mm/s sharp peaks.
Jan
7
comment Why do circularly connected springs have a mode with zero frequency?
@garyp: your answer is right. I explained it a bit more.
Dec
21
comment Flow through a rifled pipe
@CuriourOne: I was thinking of en.wikipedia.org/wiki/Internally_rifled_boiler_tubes. Maybe this is different. And paywalls suck!
Dec
21
comment Flow through a rifled pipe
@CuriousOne: I think this is for two phase boiling water flow for which the liquid phase gets centrifuged out to the sides of the pipe and improves heat transfer.
Apr
30
comment Is “eco” shower mode actually using less power?
@name: Yuck! Unless its a countercurrent heat exchanger.
Jan
19
comment Can work hardening of a metal be avoided?
Annealing maybe?
Jan
15
comment Why do I hear a deep rumble when I cover my ears?
No it's a barrier and it's density is mass per unit area, or kg/m^2.
Jan
12
comment Show bigger amplitude of physical pendulum means bigger period
The "hot water freezes faster" can't happen IF the entire system is described by one degree of freedom: the temperature. Real life hot water can freeze faster (cdn.phys.org/newman/gfx/news/hires/…) when the actual system is more complex. A pendulum bob has 2 degrees of freedom: force and velocity. A faster bob can surpass a slower one because velocities are different. Temperature does not have a "velocity term" appearing in the differential equation that governs it's change. Position does.
Jan
12
comment Why is it so hard to find out the sign of the cosmological constant?
Don't we know that the expansion is accelerating en.wikipedia.org/wiki/Accelerating_universe (only possible with a positive constant).
Jan
9
comment Some applications of the Einstein-Podolsky-Rosen (EPR) paradox?
The Mermin-Peres magic square game?
Jan
9
comment Why are gasses difficult to see?
Yes, but: there isn't that wide a range for which photochemical sensors can work, and the atmosphere is transparent enough over most of this range. Vision at other wavelengths, like snake pits, has very low resolution.
Jan
8
comment what is the electric field intensity inside a charged metallic shell if there is a point charge inside the shell?
You are right but it's the charges that appear at the surface are not the same charges you put in. If you put in a bunch of a + charge calcium ions, electrons will leave the surface to give it a positive charge. No calcium ions need to make it to the surface.
Jan
8
comment Is a suit that hides a soldier's heat signature fundamentally possible?
Yes these would need power, but with enough energy could be done.
Jan
8
comment Is a suit that hides a soldier's heat signature fundamentally possible?
Evaporation of water can keep the suits surface at ambient temperature, just as we keep cool when it gets hotter outside than our body temperature.
Jan
8
comment Do objects launched from Earth retain the Earth's lateral inertia (67,000mph)
The voyager was helped by this, otherwise it would have fallen into or near the sun and gotten incinerated. Orbital mechanics are more complex when you consider the influence of the suns gravity, but it still starts out with the 67k boost.
Jan
4
comment Resource cost and noise effects in quantum teleportation of multible (entangled) qbits
I guess its not obvious it will work because you have to observe each qubit you get, and observing a qubit will destroy entanglement with other qubits. But somehow it does not.
Dec
29
comment Why are crystals so useful for quantum isolation?
So crystal periodicity is conducive wave function coherence, it seems.
Dec
29
comment Resource cost and noise effects in quantum teleportation of multible (entangled) qbits
That answer is exactly what I was looking for. Do you have references?
Dec
18
comment What's the escape velocity of Naked Singularities?
Imaginary escape velocity simply means that particles placed there will shoot outward to infinity (an another universe, perhaps?). The RN singularity is REPULSIVE. That being said, anything within the inner horizon isn't thought to be RN geometry, as "mass inflation" results.