(C) Daily Kos This story was originally published by Daily Kos and is unaltered. . . . . . . . . . . Top Comments: How the Galaxy Might Affect Earth's Climate [1] ['This Content Is Not Subject To Review Daily Kos Staff Prior To Publication.'] Date: 2024-06-16 Here at Top Comments we strive to nourish community by rounding up some of the site's best, funniest, most mojo'd & most informative commentary, and we depend on your help!! If you see a comment by another Kossack that deserves wider recognition, please send it either to topcomments at gmail or to the Top Comments group mailbox by 9:30pm Eastern. Please please please include a few words about why you sent it in as well as your user name (even if you think we know it already :-)), so we can credit you with the find! No one could be blamed for thinking that the factors controlling climate are the limited to things here on Earth (atmospheric and ocean currents and compositions, etc) and the behavior of the Sun. In fact, before today, I would have thought very little outside of such factors would have an effect, and, in fact, nothing outside the Solar System would have any effect at all. A new study suggests otherwise. Just as the Moon revolves around the Earth, and the Earth revolves around the Sun, similarly, the Solar System itslef revolves around the Milky Way Galaxy. However, the density and composition of the galaxy varies dramatically along the path of the Solar System’s galactic orbit. The Solar System is currently in a 1,000-light-year-wide "Local Bubble", or "local interstellar cloud" (LIC). This "bubble" is a lot less dense than typical interstellar space, with 0.001 particles per cubic centimeter compared to the typical 0.1 atoms per cubic centimeter. The Solar System will leave this sparse region of space in the next few thousand years and head once more into the interstellar medium. Over the course of millions of years, the Solar System has passed through regions of varying densities. Whether the path of the Solar System’s orbit happens to be above or below the principal plane of the galaxy, or whether it’s entering or exiting a galactic arm can dramatically change the environment surrounding the Solar System. What effect could these variations have on the planets of the Solar System, and more specifically, on Earth? First, it’s important to understand that there is a shield of sorts that protects the entire Solar System from the interstellar medium (ISM), that is, the stuff that actually occupies what we tend to (mistakenly) call “empty space.” That shield is the solar wind. The nuclear processes that caus the Sun to produce prodigious amounts of light also produce a vast stream of particles racing out in all directions; this is what’s called the solar wind. The solar wind peters out at about three times the diameter of the orbit of Pluto, and this stream of particles helps to keep out any foreign material from the ISM. This region of protection is called the heliosphere. Our species has only experienced our environment as the Solar System was traveling though a low density environment. The new study quantitatively speculates what might happen if that density were significantly higher. The prediction is that the heliosphere will contract, becoming a less effective shield from the interstellar medium. "Large amounts of neutral hydrogen as a result of an encounter with cold clouds with densities above 1,000 cm−3 will alter the chemistry of Earth’s atmosphere," the team wrote. "Very few works have investigated the climatic effects of such encounters quantitatively in the context of encounters with dense giant molecular clouds. Some argue that such high densities would deplete the ozone in the mid-atmosphere (50–100 km [31–62 miles]) and eventually cool the Earth." The team says that geological evidence of increased amounts of 60Fe (iron 60) and 244Pu (plutonium 244) isotopes found in ice cores, the oceans, Antarctic snow, and samples of the Moon, could be evidence of these particles reaching Earth as we traversed the Local Lynx of Cold Cloud 2 million years ago. These isotopes are spat out by supernovas and neutron star mergers, which then become trapped by interstellar dust. These isotopes in the geological record have previously been explained as being sent here by a close supernova, but the current team believes they could be explained better by particles trapped in the cloud, as a close-by supernova would collapse the heliosphere to distances of 1 AU (the distance between the Earth and the Sun), while a further afield supernova would not deposit enough 60Fe on Earth. Two cautions here: First, The Solar System won’t be entering a region of increased density for something on the order of another million years. Second, in its 4.6 billion year lifetime, the Solar System has passed through regions where the ISM is dense many times, and while it may have had an effect, even a dramatic one, life was never wiped out entirely. It would be interesting to see if scientists can correlate climate changes in the fossil record with ISM density variations along the Solar System’s galactic orbit. Normally, I would say at this point that “Comments are below the fold.” Unfortunately, as you may know, the script that runs the picture quit was borked, so that element has been missing for a week. Further, the Top Mojo script has ceased working, so I am unable to provide the list of comments with the highest number of recommends either. Finally, there were no nominations tonight, so that cupboard is also bare. Please, particularly NOW, where we have nothing else to offer due to technological issues, we would greatly appreciate your comment nominations, so that we can provide the thing we advertize. Top Comments (June 16, 2024): No nominations or highlights tonight. Top Mojo (June 15, 2024): The Top Mojo script is currently not working. Apologies. Top Photos (June 15, 2024): The Top Pictures script is currently not working. Apologies. [END] --- [1] Url: https://www.dailykos.com/stories/2024/6/16/2247017/-Top-Comments-How-the-Galaxy-Might-Affect-Earth-s-Climate?pm_campaign=front_page&pm_source=latest_community&pm_medium=web Published and (C) by Daily Kos Content appears here under this condition or license: Site content may be used for any purpose without permission unless otherwise specified. via Magical.Fish Gopher News Feeds: gopher://magical.fish/1/feeds/news/dailykos/