Horace Heffner wrote:
The Northern exposure idea would require a full galactic N-S traversal
(bobbing up and down) period, or about 130-200 M years, while the period
between extinctions is often roughly half that.
Hmmm ...Are you reading the same article I am? ... the complete cycle is
said to be half your ~130 my assumption and occurs exactly 4 times in
one complete galactic 250 year revolution - which is probably based on
our Milky Way galaxy having two radial spiraling "arms," as do many
observable galaxies.
Menvedev sez: "We propose that the cycle may be caused by modulation of
cosmic ray (CR) flux by the Solar system vertical oscillation (64 My
period) in the galaxy, the galactic north-south anisotropy of CR
production in the galactic halo/wind/termination shock (due to the
galactic motion toward the Virgo cluster), and the shielding by galactic
magnetic fields."
The Virgo cluster would be in the vector of "great attractor".
Plus a secondary problem would be in assuming that every complete period
must result in an extinction event.
There could well be two interacting cycles which are in play in this
scenario - one is the ~62+ m.y. wobble, and the other would be this:
what is going-on, at that time-frame, within the "great attractor"
itself - i.e. causing it to spew out the high level of cosmic rays,
which are the sine qua non - needed to disrupt the Oort/Nemesis cloud.
On some of the cyclical "windowing" events (62-63 m.y. complete cycle)
the "great attractor" itself may be rather calm (no extinction) while on
other exposures, the "great attractor" is very active.
It could have been relatively calm for an extended period prior to 600
m.y..
BTW the "fudge factor" which can and does make all of these dates
line-up exactly is the fact that a cosmic ray barrage will alter the
decay rates of the minerals which we routinely use to do the dating.
The past extinction event is said to be 65 million years ago - BUT - if
the decay rate of the minerals we use to make that determination, had
been speeded-up by the radiation of the event itself - the "real date"
would need to be pushed back.
Jones
