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Message: <blockquote data-quote="KarinsDad" data-source="post: 6042453" data-attributes="member: 2011">Thank you for your more detailed and thought provoking discussion. As I mentioned earlier, MOND does have weaknesses when discussing clusters of galaxies.But, have Dark Matter theories never been adjusted as more data is acquired? The fact that adjustments have to be made to MOND appears to be what good science should do. Adjust theories to match observations.As for cluster issues, doesn't LCDM some times have problems with clusters? For example, in the Bullet Cluster, shouldn't the relative velocity between the two clusters be faster using Dark Matter? The lensing works, but the velocity doesn't? Isn't the Bullet Cluster a problem for both types of theories?Actually from what I've read, MOND makes very good predictions in many areas (and not just galaxy speed), not so good ones in others. To focus on just those where it falters and say that it is probably wrong because of those isn't objective science. No doubt, MOND is minimally incomplete and even possibly incorrect because it cannot explain everything. Dark Matter also has areas where it does not make good predictions (or at least consistent predictions from one galaxy to the next).There are a lot of recent articles that are starting to support MOND more and more, but some of the more (apparently, who can actually tell) objective sources that I've recently read seem to indicate that it is not winning the fight quite yet. And, this is how you appear to view it.But, I wouldn't be surprised if the final answer is a combination of a few current theories. The gravitational equations might be wrong and there might be invisible matter out there. There also might be other forces at work beyond just gravity or gravity might not work exactly as thought.<a href="http://blogs.scientificamerican.com/critical-opalescence/2012/06/11/is-dark-matter-a-glimpse-of-a-deeper-level-of-reality/" target="_blank">http://blogs.scientificamerican.com/critical-opalescence/2012/06/11/is-dark-matter-a-glimpse-of-a-deeper-level-of-reality/</a>But, when someone like Physics Nobel Prize winner Martinus Veltman (who helped architect the standard model of particle physics) states that he doubts that Dark Matter exists at all, other scientists should at least listen:<a href="http://www.scientificamerican.com/article.cfm?id=lindau-dark-energy" target="_blank">http://www.scientificamerican.com/article.cfm?id=lindau-dark-energy</a>He might be wrong. Only time and a lot of hard work will tell.An absence of data in the case of Neptune? Actually, this analysis is a bit flawed.Scientists did have data. They knew the distance from the Sun to Neptune. They had an idea of its mass and chemical composition. They had information on the amount of solar wind that arrived at Earth and models to predict how much would arrive at the other planets. They did have some information on wind speed on other gas giants in the solar system like Jupiter and Saturn and had even more wind speed data once Voyager 1 and 2 got to Jupiter and Saturn, a decade before Voyager 2 got to Neptune.To insinuate that scientists had no data and then "Wow, now we have data" is incorrect. They had quite a bit of data there. Their theories and models were just incorrect based on the data that they had at the time. But, there wasn't a total lack of data there.If one does a matrix diagram of Dark Matter theories and Gravity Modification theories, one finds that both types of theories cover some observations very well and other observations, not so well.The problem that has been creeping more and more into at least the literature (and opinions like Martinus Veltman's) is a) DM has its flaws just like MOND or other theories, but more importantly b) DM just hasn't been found yet. Period. Not even a hint of it. At least to the lay person, DM sounds like magic. We don't know what it is, we've spent many hundreds of thousands of manhours of some of the brightest people on the planet, and many millions of dollars trying to figure out what it is and/or detect it, but we are teaching our students that it must be true because the equations tell us that it is true.Well, of course one is going to have thousands of scientists the world over that believe it is true if that is what they were taught in school and there is no alternative theory that explains it all better. Just look at how quickly the students in the video above were ready to defend DM. Why? Because that is what they were taught as true science. They know about alternative theories, but they discard them out of hand without putting any real work into them.</blockquote>

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