Expert: Jayendra Upadhye - 2/12/2009

Question
QUESTION: My google search for the Milky Way's (Galactic) Plane brought up your answer to a question on page: http://en.allexperts.com/q/Astronomy-1360/2008/2/earth-orbital-plane-vis.htm.
My question is about the frequency of this bob that you describe. I am wondering and tending to lean towards 3600 years versus the 740,000 thousand year cycle. Would you be about to verify this timeframe that I am interested in?

ANSWER: Hi,
Thanks for bringing up that answer.
It was very interesting.

Especially now that the view is gaining upper hand that the sun is actually not native to the milkyway galaxy, but gobbled up from the irregular galaxy sagittarius dwarf galaxy.
[refer:- http://www.viewzone.com/milkyway.html].

The Sun oscillates up and down relative to the galactic plane approximately 2.7 times per orbit and an orbit aroumd the galactic center takes about 225 to 250 million years.

refer:- http://en.wikipedia.org/wiki/Sun
Refer para titled "Location within the galaxy".

You may draw conclusions based on that.

regards
Jayen

---------- FOLLOW-UP ----------

QUESTION: Thank you for your answer of 2.7 times per orbit. But I haven't in any of my investigation, seen a figure of about 90 million years? May I ask you, who's evidence are you referencing for the solarsystems oscillation timeframe thru the galactic plane? I've heard of new research from some Russian scientists, but nothing yet about their findings. Anyways hope this secondary question can put to rest and resolve the original question.

Answer
Mike,

I gave my reference !refer:- http://en.wikipedia.org/wiki/Sun
further links:
1 - http://en.wikipedia.org/wiki/Mass_extinction#Galactic_plane_oscillations
2 - http://en.wikipedia.org/wiki/Mass_extinction
which is main link for 1 above.
3 - http://www.wonderquest.com/extinctions-safetyglass-magnetslasers.htm
This mentions the figure 90 million clearly.
4 - http://www.bpccs.com/lcas/Articles/massextinctions.htm
A highly technical paper. Refer para 'Galactci tide'.

In the past 540 million years there have been five major events when over 50% of animal species died. Life as we know it has been around since last 600 million years approx. Algal life forms have existed for a much longer period. (converting the atmosphere to the present oxygen rich one, over a slow 2 billion period, before sex was invented and the cambrian explosion happened.

dividing 540 by 5 yields 108 million years, a figure closer to 90.
Actually, estimates of the number of major mass extinctions in the last 540 million years range from as few as five to more than twenty. These differences stem from the threshold chosen for describing an extinction event as "major", and the data chosen to measure past diversity.


We are entering a phase of rapid extinctions as we speak.

The current rate of extinction based on statistical modelling of populations of species for which data is easily obtainable, is estimated to be 10 to 100 times the usual background level,[46] and has been elevated above the background level since the Pleistocene. It is feared that 50% of species could be extinct by the end of the 21st century.[47] Factors such as deforestation, habitat destruction, hunting, the introduction of non-native species, pollution and climate change have reduced biodiversity profoundly.

regards
Jayen