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My academic interests are in power plants of all types, shapes, and sizes, and how well they play with each other. My hobbyist interest are kind of all over the place. I like the maker movement, I'm most interested in the sensors and data, the "internet of things" kind of stuff. In physics, I'm probably the most curious about general relativity topics, but I'm all over the place. We once had a Nuclear Engineering proposal on Area 51, but it failed.


4h
comment Is the planet Mesklin as described in Hal Clement's Mission of Gravity correct?
@EmilioPisanty You are, of course, strictly correct. But for that matter, when you start walking, you'll kick in dynamic components like the Coriolis force. Thus, we can't conclusively accept your narrative from a map of the field by itself (or without other assumptions, like walking "slowly"). For Mesklin itself, it would be like a cross-continent train ride raises your head less than 60 feet. For Saturn, it would be like 2 inches.
6h
revised Is the planet Mesklin as described in Hal Clement's Mission of Gravity correct?
added 361 characters in body
Apr
24
comment Is the planet Mesklin as described in Hal Clement's Mission of Gravity correct?
@TimB Ugh, I just realized one of those nasty more complicated details. The field I drew is not conservative, which means you could make energy from it. It also means that the blue line isn't truly equipotential. However, for the rotating planet, the field is conservative by some geometry tricks. We would need to imagine curved lines for the gravity vector, and that the lines are perpendicular to the blue line as well. That's not quite what I drew, and I'm sorry about that.
Apr
24
comment Is the planet Mesklin as described in Hal Clement's Mission of Gravity correct?
@TimB Potential energy is relative, so that's a little difficult to answer. Potential is constant along the ground, and it's also constant along the blue line. 1 arrow's length always represents the same change in potential (this is the relationship between fields and potential).
Apr
24
answered Is the planet Mesklin as described in Hal Clement's Mission of Gravity correct?
Apr
20
awarded  Nice Question
Apr
15
awarded  Popular Question
Apr
2
comment Why planes have propellers in front but watercraft have them behind?
@Rick My understanding is that boats remove the fluid ingress via the "flush hole". Having an exit path for ingress is almost always the better option. The pressure difference is also critically important, which clearly exists here.
Apr
2
awarded  Popular Question
Mar
30
answered Is an atom charged after undergoing beta emission?
Mar
29
awarded  Nice Answer
Mar
25
comment What would it be like “inside” a star?
@DevSolar That is exactly what I had in mind. However, I was hesitant to elaborate on one detail, and upon further research, my doubts are warranted. As you go deeper into the sun, the visible wavelengths will not decrease in intensity, because increasing temperature only adds more in shorter wavelengths, but doesn't subtract from long wavelengths. So you'll be microwaved, but you'll still be blinded in the visible spectrum.
Mar
25
answered What would it be like “inside” a star?
Mar
11
comment Could a Nuclear Reactor Run (controllably) in Prompt-Critical Mode?
@DOS4004 I had to look check, but I think I know where you get the "delayed-supercritical" wording from. This is specifically the scenario where the reactor is increasing power. In this state, you could say that it is "prompt-subcritical", because the prompt neutrons alone are insufficient to maintain criticality. You're asking if we could replace the regular ramp-up with a controled prompt-supercritical ramp-up. I don't know of any control element which is non-mechanical. Unless you can find a truly electric control method, then I think the control could be fast enough.
Mar
10
awarded  Popular Question
Mar
10
answered Could a Nuclear Reactor Run (controllably) in Prompt-Critical Mode?
Mar
8
comment Why are neutron absorption cross sections high at low incident energy?
It seems pretty clear that out of the 2 possibilities the OP laid out, it is the 1/v behavior dominating. We just have a multitude of justifications for that behavior operating at different levels of physics. I read this question as asking for a genuine quantum explanation of that 1/v behavior, which is a perfectly valid question.
Mar
7
comment How to calculate the colour a human eye sees when looking at a light spectrum?
@ByteCommander The sensitivity curves are applied in a simple convolution integral. To apply that to a single spectral line, you just multiply the intensity by the value of the sensitivity curves at that wavelength. After that, there is a matrix to directly convert to RGB. You may want to adjust the gross brightness of your final result because that's divorced from the hue. I wrote an answer which covered the steps, which I assume is the same mathematically as what the other user suggested. physics.stackexchange.com/questions/46574/…
Mar
7
comment Why does the value of gravity decrease as we dig into the Earth, but also decrease as we enter the upper atmosphere?
Gravity does not decrease as you dig into Earth (initially) because it is not uniform as the question implicitly assumes.
Feb
25
answered In terms of scale, where does the concept of Reynold's number cease to have meaning?