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Apr
21
comment GR and my journey to the centre of the Earth
In the twin paradox, only one twin rides a geodesic; the other rides a timelike curve that is not a geodesic (although some sub-segments of the curve may be coincident with a geodesic, i.e. parts of the trip where the travelling twin is not accelerating).
Apr
21
comment GR and my journey to the centre of the Earth
A quibble: you're maximizing, not minimizing, the proper time along your worldline. Any deviation from a geodesic incurs time dilation and results in a shorter proper time (c.f. the twin paradox).
Jan
16
awarded  Yearling
Dec
25
comment What is a peryton?
This answers where they come from, but not what a peryton is...
Jul
31
comment Does RF have any non-orthagonal properties?
A photon is a photon, no matter the frequency, so yes, in principle you could do the same sort of thing with RF...I'm guessing it would be much more difficult to generate individual RF photons than visible light photons, though, due to the very low energies of RF photons.
Jul
22
comment Is it normal for radiation levels to be elevated near a medical imaging lab?
TBBT, did you mix up microsieverts and millisieverts? 365.24 * 24 * 0.96 = 8400, not 8.5...
Jul
22
awarded  Civic Duty
Jul
22
comment Is it normal for radiation levels to be elevated near a medical imaging lab?
Google suggests the "federal occupational limit" of radiation exposure is 5000 millirem/year, which converts to 5.7 μSv/h. So a level of 0.96 μSv/h (intermittently) doesn't seem excessive by that standard, FWIW. See also the xkcd radiation chart
Jul
22
comment Is black a color? If so, does space have a color?
Define what you mean by "black" and by "color" and then you can answer these questions according to your definitions. Of course, someone else with different definitions may give different answers...
Jul
20
comment How many dimensions does a singularity have?
But the diagram suppresses two space dimensions, so aren't the singularities three-dimensional then? (Just like the event horizon, though it appears one-dimensional in the diagram as well.)
Jul
18
comment Curvature of spacetime and the equivalence principle
@MaddeAnerson Yes, it's true that would not be very revolutionary. The content of the EEP is more than just "any curvature cannot be noticed in an infinitesimal area", though. I've added some more to my answer about that.
Jul
18
revised Curvature of spacetime and the equivalence principle
add note comparing gravitation to EM
Jul
18
comment Curvature of spacetime and the equivalence principle
@MaddeAnerson However sensitive your instruments are, you can always restrict yourself to a small enough region that you cannot see the curvature - formally, an infinitesimal region - and in that small region you can't tell the difference. That's the meaning of "local" in the equivalence principle.
Jul
18
revised Curvature of spacetime and the equivalence principle
added 32 characters in body
Jul
18
answered Curvature of spacetime and the equivalence principle
Jul
13
revised Why do decompositons like $16 \otimes 16 = 10 \oplus 120 \oplus 126$ tell us which Higgs representations we can use?
improved math formatting of angle brackets
Jul
13
suggested approved edit on Why do decompositons like $16 \otimes 16 = 10 \oplus 120 \oplus 126$ tell us which Higgs representations we can use?
Jul
6
answered How do you convert RGB lux into a singular value?
Jun
30
awarded  Popular Question
Jun
24
comment Does gravity play a role in the Earth's equatorial bulge?
Just guessing, but a balloon full of a very viscous liquid, like honey, might be a better model than a ball of dirt. It has a solid skin surrounding a liquid interior. The Earth's mantle isn't exactly a liquid, but it sort of behaves that way. On the other hand, the Earth's crust isn't stretchy like a rubber balloon. My guess is if gravity were turned off, the Earth's crust and mantle would fracture and fly apart under its centrifugal force, leaving only the solid core.