1,124 reputation
8
bio website
location
age
visits member for 9 months
seen 3 mins ago

16h
revised Diameter of any galaxy
added 270 characters in body
16h
comment Diameter of any galaxy
You're right, it depends on the user's perspective. I guess foreshortening might be an issue for irregular galaxies although I'm not sure how this is related to the equation in the question?
17h
answered Diameter of any galaxy
17h
comment Diameter of any galaxy
But is foreshortening not 'just' an optical illusion? If you use instrumentation to measure the angular diameter, this should not be a problem?
1d
awarded  Custodian
1d
reviewed Approve suggested edit on Do all stars have an oort cloud or is it a rare occurance?
1d
awarded  Custodian
1d
reviewed Looks OK How do we know that the speed of the influence of gravity is instant?
1d
comment Star class according to initial mass
@Py-ser Yes, I know. Though luminosity class is kind of a strange name if you consider Main Sequence stars (luminosity class V), which have absolute magnitudes from 14 to -9. ;-)
2d
revised Star class according to initial mass
added 356 characters in body
2d
revised Star class according to initial mass
added 356 characters in body
2d
answered Star class according to initial mass
Oct
16
comment Planets and Pluto? Neptune?
Thank you, this (together with your answer on physics.SE) makes it quite clear!
Oct
16
comment Planets and Pluto? Neptune?
@KyleKanos No I don't disagree, though I would prefer if the IAU was more clear in its definition.
Oct
16
comment Planets and Pluto? Neptune?
@LocalFluff I hadn't considered the PR side. You may be right.
Oct
15
answered Planets and Pluto? Neptune?
Oct
14
comment Mapping selenographic coordinates onto a sphere
I'm not sure what your question is but the source code seems to be ok if you take $y$ to be the axis along the polar axis. Usually $z$ is used for this axis.
Oct
13
comment What happens if gravity shuts down for only one second?
Of course, but I assume the collapse into a black hole happened long before turning of gravity. Do we know what happens to matter in a black hole?
Oct
13
comment What happens if gravity shuts down for only one second?
I'm not sure but I always thought that the issue with black holes was that even the pressure from electron or neutron degeneracy could not stop gravitational collapse.
Oct
13
comment What happens if gravity shuts down for only one second?
The expansion would happen because of the pressure. Stars are in hydrostatic equilibrium (gravity balances pressure) so if gravity falls away, the star starts to expand because of the pressure. But black holes are NOT in equilibrium. Where would the pressure come from?