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Milky Way's Spiral Arms Could Not Have Caused Climate Change
KentuckyFC writes "One of the puzzles of Earth's climate history is an apparent 140-million-year cycle in the climate record. Various astronomers think this can be explained by the passage of the Sun through the spiral arms of the Milky Way, which also seems to have had a period of about 140 million years. The thinking is that in regions of denser star populations, supernovas would have been more common, bathing the Earth in cosmic rays more often. These cosmic rays would then have seeded the formation of clouds that cool the planet. But in recent years, astronomers have mapped out the structure of the galaxy in much more detail. And now a pair of US astronomers have reanalyzed this climate change idea in light of the new evidence. Their conclusion is that the climate change cycle cannot possibly have coincided with the movement of the Sun through the spiral arms. So whatever caused the 140-million-year climate change cycle on Earth, it wasn't the Sun's passage through the galaxy."
So what? Heart disease is more responsible for human deaths than murder, and yet we still take action against murderers.
Tom Swiss | the infamous tms | my blog
You cannot wash away blood with blood
Because now the political "we don't cause GW" arguments will begin, and the bickering....
It shouldn't even be about global warming. It should be about national security. If you have no renewable resources, and rely on other (enemy) nations to provide that stuff to you and your way of life, you have a severe problem.
Let's get off oil if for nothing else, to bankrupt every middle eastern country out there. We won't bother maintaining a presence there if there's nothing to take advantage of.
The price is always right if someone else is paying.
This is the very technical (and long-winded) explanation for something along the lines of "We are telling you, Miss Daisy, that your cat was not put into that tree by giant ninja robots from outer space."
If you can read this, I forgot to post anonymously.
Both Shaviv's and Melott's papers are based upon models of the Milky Way that are built from observations taken from a single point in the universe, and made during a negligible time frame. This model is then kept valid and unchanged for a timeframe of about 1.000.000.000 years, neglecting for example errors in measuring accelerations of the galaxy and of the solar system, the 3D structure of the galaxy, dark matter influence (and existence...) on the motion of the galaxy, etc. Still too much unknowns before reaching a definite answer, isn't it ?!?
One of the problems with the suggestion of moving through the galactic plane being a major issue is that the Sun is currently very close to the main galactic plane at the moment. That is something that has to be explained if you want to use this concept to prove or disprove a hypothesis regarding the orbit our solar system takes through the galaxy.
What I would be curious about is the "CO2 data" that they are using, and the assumption that global temperatures have a direct correlation to this substance, not to mention the reliability of the measurement process over the scale of billions of years to calculate what levels of this gas were through more than just a couple of galactic years. Yes, I know there are attempts to measure global temperatures over time using the geologic record, but it seems to me that both the CO2 measurements as well as measurements of the orbit of the solar system have such huge margins of error that doing a statistical comparison of the two could give you virtually any kind of conclusion that you want.
I have to assume that this paper addresses these issues in some detail (I would love to read the original paper).
One other thing that struck me, in looking at the supposed solar system orbit that they plotted in this paper, is if they have accounted for the fact that the galaxy is a dynamic and not a static place? They calculated the path of the Sun over apparently three galactic years, but at the same time all of the objects that they used for measuring protuberance of the orbit are also moving in their own galactic orbits. If there is a model that they were able to develop that shows the galactic evolution of the Milky Way over the past 500 million years. Seriously, I had no idea that stellar parallax measurements (to accurately plot the positions of stars) were so accurate and have been for long enough to not only get a good fix on the position of a large number of stars in the Milky Way to be able to also plot the apparent trajectories of this many stars and galactic nebulae. That is some trick, and such a model would have a great many other uses besides trying to prove anthropogenic global warming (or disproving an alternative hypothesis).
My understanding was that stellar parallax measurements were only good to about 1 or 2 significant digits and getting the order of magnitude down. That may have improved with the Hubble and some other star surveys with really accurate telescopes, but I don't think it is too much better than that.