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21h
reviewed Leave Open What causes a materials distinc sound?
21h
reviewed Leave Open Does QM unequivocally violate the law of bivalence?
21h
comment Can the density of a black hole be altered (if at all) by absorption?
You should go back and reconsider the notion that black holes are necessarily dense. A billion solar mass black hole (as exists at the centers of some galaxies) has a density of about $20\ \mathrm{kg/m^3}$, $50$ times less dense than water.
21h
reviewed Leave Open Physical explanation of Pascal’s Law
21h
reviewed Leave Open Can Gravity be used as an energy source?
21h
reviewed Leave Open Why an impact exerts so much force?
21h
revised Why an impact exerts so much force?
edited tags
1d
answered Energy conservation around a black hole
1d
comment Converting between matrix multiplication and tensor contraction
@Dargscisyhp The key is the word represent. There is a well-defined, right and proper representation of rank-2 tensors as matrices. The problem is matrices are insufficiently rich objects to represent rank-(1,1), rank-(0,2), and rank-(2,0) tensors simultaneously in any sort of consistent way. An analogy might be streamlines representing either electric or magnetic fields, but if you have both simultaneously your diagrams are quickly going to get messy, since streamlines don't capture the relationship between $E$ and $B$.
2d
revised What is $\omega \times v$?
math and grammar
2d
comment Ideal gas equation and atmosphere of Venus
I didn't mean to imply you were dishonest, certainly -- just that scientific culture could construe it that way were it to come from someone more familiar with the practices.
2d
comment Ideal gas equation and atmosphere of Venus
@pr1268 That only makes Floris's comment all the more important to pay attention to. We do not know the pressure that precisely, so you cannot calculate density that precisely either. And the standard for scientific communication is that reporting so many significant figures implies that you in fact have calculated the result so precisely. That is, reporting so many significant figures is not just cumbersome, it is misleading and almost dishonest.
Apr
25
comment How do we know the Schwarzschild solution contains an object of mass $M$?
@knzhou Moreover, if you want to involve other branches of physics you're going to have to do more than just that. Any real matter will couple to itself, and so the sum of individual masses ("baryonic mass" to some) differs from the $M$ you want to recover ("gravitational mass") by the binding energy. This is a very measurable effect, being ${\sim}10\%$ or so in neutron stars.
Apr
25
awarded  Nice Answer
Apr
24
comment Relative velocity of light beams
@MohamedOsama No, Einstein said the laws of physics hold in all reference frames. At the same time, relativity says that there is no valid reference frame moving at the speed of light relative to another. That is, physics doesn't even have the concept of how things might appear if moving at the speed of light.
Apr
23
revised What is the word describing the pairs: temperature and energy, chemical potential and particle number?
edited tags
Apr
23
reviewed Close electrostatics and elecrtic field
Apr
23
reviewed Close If black hole is a “hole”, how can its position be pinpointed from every position in universe?
Apr
23
reviewed Leave Open Arms of Parallal Plate Capacitor
Apr
23
reviewed Leave Open Help with uncertainties! pixels and pinholes