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Well, it looks like passing through the middle of the galactic plane might have its own share of risks: an increased number of comets might be hurled towards the Earth because of gravitational interaction with the densest parts of our galaxy.
And here’s the bad news. According to their calculations, the Solar System will be passing through the galactic plane in the near future, and should see an increased risk of impact. Our risk of impact could increase 10-fold.
by: Jessica Kloss
Institution: Princeton University
Date: May 2008
A recent study at the Cardiff Centre for Astrobiology suggests that mass life extinctions on Earth correspond to the solar system's movement in the galaxy. Center director Professor Chandra Wickramasinghe and the Cardiff team developed a computer simulation that mapped the movement of the solar system in our galaxy, the Milky Way, and found that times of greater comet bombardment , and therefore mass extinctions , are linked to our movement through the galaxy.
The Sun and the stars that make up the Milky Way rotate around the galactic center, forming a disk called the galactic plane. But the Cardiff team found that the Sun's movement is not perfectly aligned with this disk. Instead, the plane of the Sun's orbit is slightly tilted compared to the galactic plane, so that approximately every 35 to 40 million years, we "bounce" up and down through the densest region of the galactic plane. During this time, the chance of comet collision increases tenfold.
Unfortunately for species on Earth, as the solar system passes through the densest part of the galactic plane, new comets plunge into the solar system , some of them colliding with the Earth. Evidence from the craters on the Earth confirms that about every 36 million years, there is a period when the Earth suffers a greater number of collisions. "It's a beautiful match between what we see on the ground and what is expected from the galactic record," said Professor William Napier of the Cardiff Centre for Astrology, who co-wrote a paper on the subject to be published in the Monthly Notices of the Royal Astronomical Society.
The current position of the solar system in the Milky Way suggests that another period of greater comet bombardment is not far away. But while such bombardments are believed to have been the end of the dinosaurs, and are generally treated by species on Earth as bad news, it may also help spread life to other parts of the universe. When comets slam into the Earth, debris containing micro-organisms is thrown into space , and could have a chance to spread in the universe.
- See more at: www.jyi.org...
Both the impact cratering record and the Sun’s position near the Galactic plane imply that we are in a bombardment episode now.
The current position of the solar system in the Milky Way suggests that another period of greater comet bombardment is not far away.
We calculate the expected flux profile of comets into the planetary system from the
Oort cloud arising from Galactic tides and encounters with molecular clouds.
We find that both periodic and sporadic bombardment episodes, with amplitudes an
order of magnitude above background, occur on characteristic timescales 25–35 Myr.
Bombardment episodes occurring preferentially during spiral arm crossings may be
responsible both for mass extinctions of life and the transfer of viable microorganisms
from the bombarded Earth into the disturbing nebulae.
Good agreement is found between the theoretical expectations and the age distribution of large,
well-dated terrestrial impact craters of the past 250 million years.
A weak periodicity of 36 Myr in the cratering record is consistent with the Sun’s
recent passage through the Galactic plane, and implies a central plane density 0.15 M⊙ pc−3.
This leaves little room for a significant dark matter component in the disc.
Both our position relative to the Galactic plane (Joshi
2007 and references therein) and the impact cratering record
indicate that we are presently in, or very close to, the peak
of an impact episode.
Giant molecular clouds are concentrated within the spiral
arms of the Galaxy. Leitch & Vasisht (1998) identify
two great mass extinctions, the Cretaceous-Tertiary (65 Myr
BP) and end Permian (225 Myr BP) with Sagittarius-Carina
and Scutum-Crux arm crossings respectively. Gies & Heisel
(2005), on the other hand, find the mid-points of recent spiral
arm crossings at 80 and 156 Myr BP. Svensmark (2006)
has modelled the motion of the Sun in relation to the spiral
arm pattern using a model-dependent hypothesis which
has the Earth’s past temperature as a proxy for encounters
with spiral arms.
With this model, the solar system
passed through the Sagittarius-Carina arm 34 Myr BP
and the Scutum-Crux arm 142 Myr BP. Both these dates
coincide with exceptionally strong bombardment episodes
(Napier 2006). It seems that, at present, uncertainties in
both the modelling of spiral arm kinematics and the strong
incompleteness of the impact crater record preclude a secure
identification of impact episodes or mass extinctions
with specific spiral arm crossings.
Both the impact cratering record and the Sun’s position
near the Galactic plane imply that we are in a bombardment
Exactly which part of this research are you disagreeing?
Because it doesn't say we should expect "more of these larger impacts" (Not to mention that the impact in the OP was not particularly large. A 1 meter object is not really very large.) Because it doesn't say we are entering any particular area of the galaxy. Because it doesn't say we are entering any particular area of the Solar System. We passed through the galactic plane millions of years ago. According to Wickramasinghe this may have disrupted the orbits of Oort cloud objects, sending them into the inner Solar System. According to Wickramasinghe we are still experiencing the effects of the last time we passed through the Galactic plane, millions of years ago. According to Wickramasinghe we are now at or near the peak of activity as a result of passing through the Galactic plane, millions of years ago. According to Wickramasinghe we are not entering the Galactic plane. According to Wickramasinghe (and his source), we left the Galactic plane millions of years ago.
Perhaps we will be hearing more of these larger impacts given the area of solar system and galaxy we are entering.
Both our position relative to the Galactic plane (Joshi 2007 and references therein) and the impact cratering record
indicate that we are presently in, or very close to, the peak of an impact episode.
And here’s the bad news. According to their calculations, the Solar System will be passing through the galactic plane in the near future, and should see an increased risk of impact.
maybe the last race of humanoids got off earth before the last impact, and then when earth physically healed, they came back to a planet where the only species of animal that was as close a match to them was the ape. they inserted their own humanoid strands into the DNA of these primitive apes, and the evolution of man began. they have come back from time to time, and were considered god(s)....
Is there a genocidal countdown built into the motion of our solar system? Recent work at Cardiff University suggests that our system's orbit through the Milky Way encounters regular speedbumps - and by "speedbumps" we mean "potentially extinction-causing asteroids".
Professor William Napier and Dr Janaki Wickramasinghe have completed computer simulations of the motion of the Sun in our outer spiral-arm location in the Milky Way (image left of spiral arms).
These models reveal a regular oscillation through the central galactic plane, where the surrounding dust clouds are the densest. The solar system is a non-trivial object, so its gravitational effects set off a far-reaching planetoid-pinball machine which often ends with comets hurled into the intruding system.
The sun is about 26,000 light-years from the center of the Milky Way Galaxy, which is about 80,000 to 120,000 light-years across (and less than 7,000 light-years thick). We are located on on one of its spiral arms, out towards the edge. It takes the sun -and our solar system- roughly 200-250 million years to orbit once around the Milky Way. In this orbit, we are traveling at a velocity of about 155 miles/sec (250 km/sec).
Many of the ricocheted rocks collide with planets on their way through our system, including Earth. Impact craters recorded worldwide show correlations with the ~37 million year-cycle of these journeys through the galactic plane - including the vast impact craters thought to have put an end to the dinosaurs two cycles ago.
Almost exactly two cycles ago, in fact. The figures show that we're very close to another danger zone, when the odds of asteroid impact on Earth go up by a factor of ten. Ten times a tiny chance might not seem like much, but when "Risk of Extinction" is on the table that single order of magnitude can look much more imposing. Worse, Bruce Willis will only be available to save us for another fifty years at most. But you have to remember that ten times a very small number is still a very small number - and Earth has been struck by thousands of asteroids without any exciting extinction events. A rock doesn't just have to hit us, it has to be large enough to survive the truly fearsome forces that cause most to burn up on re-entry.
Of course the Sun won't keep on going in this direction forever. In fact we approximate it's motion by an 'epicycle' on top of the mean motion around the Galaxy. The period of oscillation in and out of the plane of the galaxy (up and down) is about 70 million years. This means that we pass through the Galactic midplane about every 35 million years which some people have compared with the period between mass extinctions on Earth to come up with yet another doomsday theory. In fact it is true that the number of cosmic rays which hit the Earth will increase during the (about a) hundred thousand years we are closer to the Galactic plane. There have also been some plausible theories about the overall temperature of the Earth increasing (with the relevent climatic changes that implies).
In the plane of the galaxy the Sun is located in the small spiral arm we call the Orion arm (or local arm) which is really just connection between the two nearest major spiral arms (the Sagitarius and Perseus arms). There is a neat page on these structures: SEDS Milky Way Spiral Structure page. We pass through a major spiral arm about every 100 million years, taking about 10 million years to go through. During the transit, there would be a higher rate of 'nearby' supernova and possibly other so called 'environmental stresses' which could alter the climate of the Earth.
The idea presented in the collision model is not new in the scientific community. In 1998, researchers concluded that at least two mass extinctions of life forms on Earth had taken place at a time when the Sun was passing through the spiral arms of the galaxy. The Cardiff team, composed of Dr. Janaki Wickramasinghe and Professor Bill Napier, has uncovered further evidence to support this theory. According to their calculations, the Sun goes through the plane of the galaxy every 35-40 million years. The researchers evaluated the age of craters on the face of the Earth, and discovered that every 36 million years or so, the collision frequency of comets with the Earth increases by an order of magnitude.
Scientists from the Cardiff Center for Astrobiology have developed a model showing that our solar system goes through the plane of the galaxy every 35-40 million years. This is accompanied by comets hurtling into the inner solar system, coinciding with mass life extinctions on Earth. The researchers estimate that we are now in one of the predicted collisions’ period.
The researchers have produced a mathematical model demonstrating that our Sun ‘bounces’ up and down through the plane of the Milky Way Galaxy. According to the model, as we pass through the densest parts of the galaxy’s plane, gravitational forces tear comets from their paths, and send them plunging into the depths of our solar system. Inevitably, some of them collide with Earth.
The researchers deduce from both the impact crater records and the Sun’s position near the Galactic plane that we are currently in a potential bombardment period. Luckily for human kind, the collisions’ period has a half-life of about two million years, meaning that the collisions are spread over a long time. This also means that the risk for the next mass extinction might be nearer we suspect, and we must prepare ourselves for that option. Should we be caught unprepared, the result may be the end of the human race. - See more at: thefutureofthings.com...
Thanks Phage. Nice analysis. the real bad news? we live in a Universe that is pretty much designed to exterminate life where ever it may take hold.