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Re: Lyrid Meteor Showers

In a message dated 98-04-19 14:13:08 EDT, you write:

<< 
 Apologies to the list,
 
 I hate abusing all these dead Equidae, so this will be my last post to
 the list on this.  Geo and I will settle it 'underground' lest this
 become another bolide/fireball episode.  Also, Bernd seems to be having
 trouble getting on line to respond.<<

Julie, I don't think there's much more I can say to make what I'm saying any
clearer to you. If this turns into another bolide/fireball episode so be it,
but I see no abuse being done with either discussion. As long as no one is
questioning each others parenthood or the location of their heads etc, I see
these discussions productive in the long run. 

 
 Julie>>Parallelism can refer to 'a similar course'.   Bernd's induction of
the
 'classical' example pertaining to railroad tracks holds in this case
 only with regard to perspective, not to the definition of 'parallel'
 regarding lines that never meet.
 My anaylsis of our communcation problem is that, while orbits can be
 parallel elliptical or concentric, orbits containing many grain sized
 objects demand the use of the broader definition of  'travelling in a
 similar course (parallel)'-  just don 't invoke the RR track example.
 It was intended to convey perspective and true parallel lines that never
 meet.<<

While in space, think of the objects as being somewhat parallel in their
travel. When they enter the atmosphere, they don't appear parallel to an
observer but radiate from a common area. Two distant meteors from the same
shower will converge to this area and not appear parallel. The convergence is
an illusion.
 
 Julie>>Now we could really have some fun if I hop on a train travelling at a
 velocity of 90mph headed due West, Geo floats down the Mississppi at 10
 knots (boat optional) and Bernd lassos the closest comet* in time to
 observe both us and the showers to give us all true perspective.
  >>

In order for it to be said that two meteors belong to the same shower, there
are three criteria that must be met. 1) The most common one is whether or not
the meteors are in alignment with a radiant area.  2) Another is the meteors
path length in relation to i'ts appearance distance from the radiant.
Basically saying that you will have very short meteors very close to the
radiant while having longer meteors further away from the radiant. If you have
a radiant above your head and a 15 degree long meteor appeared 5 degrees
directly from the radiant, it is not a shower member. 3) Meteor Velocity. All
the meteors will have the same velocity. Except here an observer will have to
be aware of the various conditions that will make a meteor's apparent velocity
seem different. But the degrees per second will be the same. This again
involves the meteors appearance in relation to it's proximity to the radiant
and or the location of the meteor's appearance in relation to where the
radiant is located at. So...your analogy of me floating 10 mph down the
Mississippi and you traveling 90 mph on a train wouldn't work. for all intents
and purposes, we would be of two different meteor streams because of the
difference in velocities.
George Zay