Explode the myth on blackholes

Dear folks,
of late a lot theories are floated involving blackholes based on myths such as being made up of special particles (neutrinos etc.) or a pass through medium and so on. Systematic calculations reveal that a blackhole can be made of ANY material - solid, liquid or gas, any element or a mixture or compound. All it needs is a critical (minimum) size. Wanna have a blackhole of water ball or air or stone or gold or diamond? It is possible. To know more, visit this blog on 'understanding universe' at www.bsrinivasan.blogspot.com

bye

srini
astronomy

Critical radius calculation for a material of given density

r(critical) = 2*G*M / c**2 = 2 G * density * (4/3) *pi*r(critical)**3 / c**2;
r(critical) = sqrt(3*c**2/(8*G*pi*density) )= sqrt(2.7*10**16/(8*6.67*10**-11*3.14*density))
With density=1000kg/m**3 for water, r(critical) for water = 4*10**12m approx = 4*10**9km.
Now, it follows that given a value for the material density but assuming homogeneity, the critical value of radius at which the material in spherical form just becomes a blackhole. Further, the critical radius for any other material can be uniquely determined given its specific gravity, i.e. how much heavier than water it is. Taking the average value of specific gravity for our Earth as 5.5, the critical radius would then become 4*10**9 / sqrt(5.5) km = 1.7 * 10**9 km (approx).
In essence, the r(critical) varies with specific gravity in an inverse square root fashion.
With 11.6 for lead, r(critical) becomes about 1.2*10**9 km.

srini