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Aug
25
comment Was Leverrier-Adams prediction of Neptune a lucky coincidence?
Maybe this is better migrated to Astronomy?
Aug
20
awarded  Popular Question
Aug
8
awarded  Notable Question
Jul
21
answered How can space be cold? Its a vacuum?
Jun
21
comment Time inside a Black hole
You are making answer not accounting for BH evaporation to a question which explicitely asks about evaporation. -1. You can never reach the horizon before the BH evaporates.
Jun
21
revised Is there a proof of existence of time?
edited tags
May
29
comment Explain why quantum behavior is not observed in daily life
Too high temperature at the first place
May
29
comment Is there a definite boundary between a powder and a fluid?
are there any examples?
May
29
comment Is there a definite boundary between a powder and a fluid?
Can one mechanically get such fine powder that it becomes a thermal system? For instance, loses angle of repose?
May
29
comment Is there a definite boundary between a powder and a fluid?
Is there some substance that cannot be reliably classified neither to liquid nor powder?
May
29
comment Is there a definite boundary between a powder and a fluid?
what is the smallest powder one can make from ice or iron?
May
29
comment Is there a definite boundary between a powder and a fluid?
At no pressure water can only be solid or gaseous.
May
29
comment Is there a definite boundary between a powder and a fluid?
"the absence of wind is equivalent to considering water with no air around," - prove. Water with no air will sublime and fill the whole volume or be a solid ice with no fluidity (in one case no angle of repose, in the later - 90 degrees). Sand without wind has definite angle of repose, less than 90 degrees.
May
29
comment Is there a definite boundary between a powder and a fluid?
"If you drop $10^{15}$ sand particles in the desert, it will disappear," - no. In ansence of wind it will not disappear. This is what angle of repose is about: it is a constant for given granular material. You cannot change it by adding more substance.
May
29
comment Is there a definite boundary between a powder and a fluid?
totally wrong. Meniscus is caused by surface tension. In a body of water far from the ages in contact with other materials a drop will disappear without a trace. Water has ZERO angle of repose.
May
29
comment Is there a definite boundary between a powder and a fluid?
"As far as anyone can tell there is no mountain to climb in order to enter this desert, so we could say that its angle of repose is roughly zero." - no, you cannot say so, sand has fixed angle of repose, far from zero. Non-existence of a high mountain is due to wind and initial conditions, but you do not need a high mountain to measure the angle of repose. You need just a handsome of sand (for a high mountain in absence of wind the angle of repose would be essentially the same).
May
29
comment Is there a definite boundary between a powder and a fluid?
"theoretically you could make a liquid out of grains, but the energy required to grind them will be gigantic." - source and examples
May
29
comment Is there a definite boundary between a powder and a fluid?
" And yes, given a large enough number of particles or small enough sizes, the angle of repose tends to zero." - source?
May
28
comment Is there a definite boundary between a powder and a fluid?
Fullerene is a crystallic solid: chemistry.about.com/od/periodictableelements/ig/… How do u know that the grains consist of single molecules?
May
16
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