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Re: (meteorobs) Fwd: How fast do Meteors go?



On 8 May 2001, at 20:29, Marco Langbroek wrote:

> For our mathematical freaks:
> 
> According to Jachia et al. (1967) the relationship between mass, velocity,
> entry-angle and brightness is:
> 
> log M(m)=2.98-0.44m-3.89log V[inf]-0.67log(sin h)
> 
> in which m=magnitude, M=mass in kg, V[inf] is speed (infinite, not
> geocentric) and h is the zenith distance of the radiant.
> 

Well, in normal convention the log M(m) means the logarithm 
[base10] of the mass as a function of magnitude... However, the 
dependency is incomplete - it should say log M(m,V[inf],h) but 
thats just being picky. 

The real problem with this formula is in the last term. the log(sin h). 
If h is the distance of the radiant from the zenith, as stated above, 
that would be the complement of what we usually describe as the 
radiant elevation above the horizon. However, in the definition 
above, it doesnt make sense, because as the radiant approaches 
the zenith, then h->0, so sin h ->0, so log (sin h) -> infinity. That 
would imply an infinite mass is required for all radiants at the 
zenith! Makes no sense at all.

This formula has got problems.

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