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bio website david.carybros.com
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visits member for 3 years, 10 months
seen Oct 15 at 17:24

Sep
20
answered Why does Energy-Momentum have a special case?
Sep
13
answered How to determine your position underground?
Aug
29
revised How do you add temperatures?
fix glaring typo; mention "average"
Aug
29
suggested suggested edit on How do you add temperatures?
Jul
11
comment Is it possible to overload a lightning rod?
Ah, right. However, several 2-story buildings in my area have a wire from the lightning rods on the roof to a ground rod pounded into the ground. I hear "Lightning Cable must have at least 59,450 circular mils of conductivity." (which is approximately 1/4" diameter). A 0.022"x2" strap is about 56,000 circular mils -- less beefy, right? P. 5 of "How Does a Lightning Rod Work" mentions "The US lightning code suggest approximately 1/4 in. diameter copper wire".
Jul
11
comment Is it possible to overload a lightning rod?
Why do your calculations based on the thick, rigid ground rod hammered into the ground, and not on the (relatively) flexible 1/4 inch copper wire or 3/8 inch aluminum wire connecting the lightning rod to the ground?
Jun
3
awarded  Promoter
Jun
1
asked Is it more efficient to stack two Peltier modules or to set them side by side?
Mar
31
comment How is gravity consistent when you split an object into multiple pieces?
If you already know some calculus, there's a good proof at hyperphysics: "Gravity Force of a Spherical Shell" and more-or-less the same proof at Wikipedia: "shell theorem".
Mar
1
comment Toroidal Planets
@AlanSE: Yes, the plots indicate local gravitational+centrifugal acceleration of a co-rotating object. There is a local minimum outside the outer equator, which is geosynchronous orbit.
Mar
1
comment Toroidal Planets
@AlanSE: Huh? Are you even reading the same article I'm reading? The io9 article I read says "The cross-section is neither circular nor elliptic but rather egg-shaped, with a slightly sharper inside curvature than on the outside. ... having a low gravity equator and high gravity poles does not mean stuff will roll or drift towards the poles: ... the surface is an equipotential surface, so gravity (plus the centrifugal correction) is always perpendicular to it."
Jan
18
revised Intuitively, how can the work done on an object be equal to zero?
edit, as requested
Jan
18
suggested suggested edit on Intuitively, how can the work done on an object be equal to zero?
Jul
21
comment Can a moon have another large body as a satellite, and are there any examples of such?
This reminds me of the rings of Rhea.
Jul
21
comment Is it possible to orbit the sun next to Earth?
@dmckee: I agree with most of what you say, but I would have said people have "very little practical experience" with solar sails, given the success of IKAROS, MESSENGER, etc.
Jul
17
awarded  Yearling
Jul
16
comment (If and) Why does cold temperature affect semiconductors?
+1. The point of "cooling" a CPU is not to lower its temperature. The point of "cooling" a CPU is to try to keep the core CPU temperature below the melting point.
Jul
16
answered Does the Black's equation work for immortal wires / interconnections (or only for mortal ones)?
Jun
23
comment Why do electrons drift in an ideal conductor, since there's no field?
Again, yes, the known superconductors have many other surprising and exotic properties that I would not expect from their definition. My understanding is that a "superconductor" is defined as "a conductor" (i.e., a material filled with movable electrical charges) "that has zero resistance" (i.e., electrical charges do not scatter). Do you have a better definition?
Jun
23
comment Why do electrons drift in an ideal conductor, since there's no field?
@mgphys: Yes, real superconductors have many exotic and surprising properties. And yes, ballistic conduction does occur in non-superconductors. Are you implying that real superconductors are not filled with movable electrons that move without scattering? I would find that surprising, and would like to learn more.