Science a GoGo's Home Page Forums General Discussion General Science Discussion Forum Galaxy bow shock and biodiversity cycle

OUTLINE:

Out-of-This-World Hypothesis: Cosmic Forces Control Life on Earth

http://news.yahoo.com/s/space/20070423/s...trollifeonearth

"The rise and fall of species on Earth might be driven in part by the undulating motions of our solar system as it travels through the disk of the Milky Way, scientists say.
_____________

DETAILS:

Spectral Analysis of Biodiversity Cycles and Galactic Dynamics

HTML format (hard to read, indistinct text)
http://72.14.235.104/search?q=cache:8B2n63m_A6UJ:www.phys.ufl.edu/~fry/cycles.ppt+galaxy+bow+shock+and+biodiversity&hl=en&ct=clnk&cd=1&gl=uk

From the site above, click this link to download a 5MB Powerpoint file version. It's very good.
http://www.phys.ufl.edu/~fry/cycles.ppt. (direct link from here doesn't work)
___

From Dept of Physics & Astronomy - University of Kansas: "Biodiversity oscillations, galactic dynamics, and cosmic rays" (pages 5 & 6)

Warning! 20MB file!(only 2 relevant pages, but some interesting unrelated material)

http://www.physics.ku.edu/momentum/momentum06.pdf
______________

A brief abstract from a meeting of the American Physical Society (very small file)
http://absimage.aps.org/image/MWS_APR07-2007-000303.pdf

Nice one Rede. From the article:

"The galactic bow shock is only present on the north side of the Milky Way's galactic plane, because that is the side facing the Virgo Cluster as it moves through space"

Where are we at the moment does anyone know? I didn't look at the other sites. Our computer is fairly basic and slow. Perhaps the extinctions over the last 40,000 years are not the fault of humans after all! But seriously, it does open an interesting line of research. And your last link says the cycle is connected more to generation of biodiversity rather than extinction.

That's right, Terry. This has nothing to do with mass extinctions. It focuses on the discovery, in 2003, of a 62My biodiversity cycle.
_________

The theory assumes a shock front for the galaxy similar to the one observed in a galaxy in the 'Stephan's Quintet' cluster. The shock front results from the Milky Way's motion, at ~200km/s, toward the Virgo Cluster, in the direction designated "galactic north" (perpendicular to the galactic plane).

The theory says that every ~ 62My there's an increase in the strength of cosmic rays arriving at Earth. This is due to the solar system's known oscillation normal to the galactic plane. If such effects only occur at galactic north, we get the right period and a phase concidence.

There's considerable experimental and statistical evidence that cosmic rays provide ionization sources increasing low-altitude cloud cover. This in turn would probably cool the climate, which leads to aridity, and is associated with biodiversity decline. A new experiment startup (CLOUD) at the CERN Proton Synchrotron will provide more data, and more insight will come from climate models.

Cosmic rays ionize the atmosphere, producing nitrous oxide, catalyzing ozone depletion, passing increased solar UVB (90% is normally absorbed by ozone layer). Modest increases in UVB are typically lethal to phytoplankton. Nitric acid in rain may increase weathering and Strontium 87 content. This would lead to increased cancer, mutations, etc. A consistent feature associated with the 62 My period is origination of new genera (a period of increased biodiversity) after some extinction events, but there are no associated mass extinctions.

Interpretation:

1. biodiversity drops
2. stress on organisms leads to preferred gene duplication
3. as the stress is removed, species expand to fill new ecological niches
4. resulting in the origination of new taxa.
_________

See also, from March 2005:

Fossil Records Show Biodiversity Comes and Goes
http://www.lbl.gov/Science-Articles/Archive/Phys-fossil-biodiversity.html

"BERKELEY, CA – A detailed and extensive new analysis of the fossil records of marine animals over the past 542 million years has yielded a stunning surprise. Biodiversity appears to rise and fall in mysterious cycles of 62 million years for which science has no satisfactory explanation."

Thanks Rede. It gets more and more interesting. I'm sure everyone will agree with this comment from your link:

“It is often said that the best discoveries in science are those that raise more questions than they answer, and that is certainly the case here.”

Although your first link may provide the answer to this earlier problem.

With recent news regarding the fact that there is NO bow shock, this topic is rendered Sooooo mute.

There seems to be some bow shock confusion. The thread topic is about a bow shock on the northern aspect of the Milky Way - perpendicular to the galactic plane - due to its motion through space toward the Virgo Cluster at about 200 miles/s. Since our solar system oscillates from north to south of the galactic plane in cycles of 60+ million years, it is believed that it would be exposed to commensurate periodic variations in cosmic radiation.



http://www.sott.net/article/220248-Earths-Exposure-to-Radiation-Stresses-Biodiversity-Study-Says

The hypothetical bow shock referred to by gelliot is a different one, and is due to the motion of the heliosphere through the interstellar medium. Recent research indicates that instead of a bow shock there's a bow wave. In other words, there's no abrupt discontinuity at the edge of the heliosphere.



http://www.sciencedaily.com/releases/2012/05/120510141957.htm

Here's another bow shock:



One needs to be aware of which bow shock is being discussed.

I think that the suggestion of any kind of a bow shock
or a bow wave due to any movement of a galaxy would denote movement of a galaxy against a medium such as space , however
as I have found recently science says that galaxies are not moving and that it is the space expanding between galaxies
that cause galaxies to appear to be moving.

so could there really be any type of interaction that would cause
any type of bow shock or bow wave given this new method of thinking about the way that galaxies actually are not moving?

like a boat in a river floating on top of the water makes no waves.

how then could a galaxy floating along in space make waves?

but mike , that sounds like it should happen all along the
periphery of a solar system , not just in the direction that it is not moving in , or maybe its still correct to say that the solar systems inside a galaxy can and do actually move.

as for a galaxy that is not what is happening , the bow wave
or shock wave is not along the entire periphery of the galaxy
it is in one direction and that direction is now the direction that space is expanding into away from the center of the universe or just in one direction away from the earth or in front of the motionless galaxy.

Im not sure if I got that right.

its getting more and more difficult to discuss what science has laid out before us.

I can understand how a bow wave or a shock wave or both would occur given that a galaxy is actually moving THROUGH a medium , but not a galaxy that is simply being carried along as space expands.


[img]http://www.dailygalaxy.com/.a/6a00d8341bf7f753ef0133f436ddcf970b-500pi[/img]


http://www.dailygalaxy.com/my_weblog/201...nd-feature.html




the above shows a definite bow wave or shock wave , so I suppose that stars really do move through galaxies.


I cant seem to find any images of a bow wave or bow shock wave of a galaxy , the most I can find is a shock wave caused by
a collision or explosion.

Nothing wrong with your argument, Paul. However, observations, as pointed out by Mike, inform us that relative motions of many galaxies within a given cluster are predominantly affected by their local gravitational fields (mainly by the dark matter in their vicinity), not by expanding space. What we see is many galaxies in various stages of collision. A prime example will be the collision of the Andromeda galaxy and the Milky Way***

At this point in cosmic history, the rate of expansion of space is insufficient to overcome those effects, but if the rate of expansion continues to increase, as predicted, then one can reasonably expect that collisions will gradually cease, galaxy clusters will be pulled apart and, eventually, each remaining galaxy will be its own 'island universe', with no evidence of other galaxies in its sky.

*** Up to 2012, there was no way to know whether the possible collision was definitely going to happen or not. In 2012, researchers came to the conclusion that the collision is definite after using the Hubble Space Telescope between 2002 and 2010 to track the motion of Andromeda. Such collisions are relatively common..."
http://en.wikipedia.org/wiki/Andromeda%E2%80%93Milky_Way_collision

well , that's the way I used to see it.

the expanding space in the expanding universe was not itself expanding it was because everything in the space inside the universe was or used to be moving away from a point in space inside the universe.

and local occurrences could affect how they used to move.

so , does this mean that the space between andromeda and the milky way is compressing , and the compression of space is drawing the two galaxies closer together?

after all the galaxies are motionless so it is only
the expansion or compression of space that causes galaxies
to appear to move.

could the milky way and the andromeda galaxies have been
drawn into some kind of eddy current in space?

That's ok, we know where the center of the universe is. It is right here in downtown Tulsa.
Journey to the Center of the Universe … in Oklahoma

Bill Gill

cool

I like the video.
featuring a BS detector.

The space between galaxies is expanding just as is the space in every atom of your body; however, in both cases their are fields countering the expansion. In the first case the field is gravity, and in the second it's the strong nuclear force that holds nucleons together. The essential difference is that the space between galaxies can be so great that they are dragged apart by the expansion of space. Galaxies are not motionless in space. A galaxy is part of a cluster of galaxies, and clusters of galaxies form superclusters. The superclusters form strings of superclusters, so that on the largest scale, there appears to be a mesh of superclusters that might be said to have a foam-like form. All the massive constituents of this 'foam' - the matter and the dark matter - are gravitationally interacting with their neighbours. Hence, their motion through space. You can reasonably be assured that M31 is on a collision course with the Milky Way due to whatever gravitational forces have acted upon both since their formation.

so are you saying that the universe is more like an
explosion.

each particle is being propelled by the initial blast , and
particles lump together and interact as they are being carried
away by the expanding explosion.

if not then what caused the expansion to begin?

the only significant force around that causes galaxies to interact with each other is gravity and gravity attracts it does not repel.

I think of the universe as an explosion that
has taken place , I think of the acceleration of the universe
as a loss of mass as the stars become lighter due to the exhaustion of fuel.

and the stars drag / accelerate everything along with them as they travel.

I think that is a logical way of thinking about it , so what
is the logic behind space expanding for no apparent reason?

or what is the reason that space is expanding in your own words
or thoughts?

Yes, but not a conventional explosion. The currently favored theory states that there was, initially, an inconceivably rapid expansion of space known as Inflation, and first formally proposed by Alan Guth:
http://en.wikipedia.org/wiki/Alan_Guth


The expansion didn't (and doesn't) propel particles through space.


Yes, assuming we are referring to the expansion of space as a kind of explosion.


I don't know.


True. Nonetheless, space has been expanding, and continues to do so at an increasing rate. So, the assumption is that there's an unidentified force that's acting like anti-gravity, and it's been given the tag 'dark energy'.


I've no idea what's driving the acceleration, Paul. No one claims to know what it is (with the possible exception of some forum contributors). But acceleration requires energy, and this unknown energy has been dubbed 'dark energy'.

acceleration requires energy only if mass remains constant.

lets use this anology.

you have a spaceship that has been propelled to a certain speed.

onboard the spaceship there are two very large pressure vessels

1 contains hydrogen
1 contains oxygen

the mass of the hydrogen and oxygen are as follows.

hydrogen 2 million kg
oxygen 1 million kg

a fuel cell is used to convert the hydrogen and oxygen into electricity to operate a single electric motor.

the motor is not connected to anything.
while the motor is being powered the electricity is
being converted into heat and nothing else.

as time passes the hydrogen and oxygen become depleted
more and more.

mass is being lost through heat transfer to the spaceships surroundings.

heat is not matter.

In a closed system
(one that does not exchange any matter with the outside and is not acted on by outside forces)
the total momentum is constant.


since mass is being lost the spaceship must accelerate.

p=mv

m = p/v

when mass decreases = momentum will remain constant / so velocity must increase (requiring no additional energy)

ok that wont work because the hydrogen and oxygen become water.

and the water would still be in the spaceship or it would need to be dumped outside the ship.

but a star does loose mass over time.

so I guess the best analogy would be a star with a certain speed and billions of years , and the star is constantly loosing mass.

also the star doesnt make water or add any mass to itself as
it produces the heat.

yep , that sounds logical.



or maybe its just as above , what appears like an unidentified force acting like anti-gravity is nothing more than the simple
mass loss of stars.

Nice try Paul, but wrong. When mass decreases, momentum decreases. The only way to accelerate that mass, reduced or not, is to apply an unbalanced force.