Drakkith said:
Instead of using those symbols, I'd type <unintelligible> or something similar. Usually when people put symbols like this into a sentence it means that the words are curse words. To answer your question, he started to say something and then switched. I believe it was, "the fact that the matter got into that word is forcing people to-well I have another idea, I bet it's not matter it's something else."
Self-interaction means that dark matter is interacting with itself. That's why the "self" is placed before "interaction". An interaction between dark matter and baryonic matter is just called an interaction. Also, trying to quantify this as "0.5% of dark matter interacts with baryonic matter" is meaningless without further context. Is 0.5% of dark matter composed of particles that interact with bayonic matter, while the other 99.5% don't? Is this 0.5% talking about the strength of the interaction? is it some sort of cross section? I realize you probably don't have an answer for this and are just trying to ask a question, but my point is that it would greatly benefit you to try to think of these things before asking. Otherwise you'll just get frustrated when people consistently can't answer your question or keep correcting you.
I mean "interaction".. I didn't read it again or i'll catch it. I'm familiar with the distinctions. Yesterday I was watching about dark matter at youtube. And I came across this 1 hour Lisa Randall video:
When I saw her book "Dark matter and the Dinosaurs" before.. I thought she was just talking about them as part of universe and didn't know she was describing a mechanism whereby they could be connected (i'll read her book sometime next week)... this is the best illustration I found on the net:
The gist of the idea is simply there is a thin dark matter disk at plane of galaxy that can disrupt comets, etc. or as Lisa put it in
https://www.scientificamerican.com/...the-dinosaurs-a-q-a-with-author-lisa-randall/
"People have debated whether dark matter has any nongravitational interactions at all. But [my colleagues and I] thought, maybe just a fraction of dark matter does. Just the way ordinary matter is only 15 percent of all the matter in the universe, maybe there’s a fraction of dark matter—even 5 percent of the matter in the universe—that has its own interactions. It’s not the usual dark matter that forms this spherical halo [around the galaxy], it’s a new type of dark matter. So you still have the ordinary halo but in addition you have this dark matter disk."
or more details at http://www.dailygalaxy.com/my_weblog/2016/05/-the-milky-ways-dark-disk-did-it-seed-the-existence-of-the-central-supermassive-black-hole-weekend-m.html
"The extinction of the dinosaurs, however, is just one theory that will have to be re-examined if Randall and Reece’s theory proves true.”
Our Sun orbits around the Galactic center, taking approximately 250 million years to make a complete revolution. However, this trajectory is not a perfect circle. The Solar System weaves up and down, crossing the plane of the Milky Way approximately every 32 million years, which coincides with the presumed periodicity of the impact variations. This bobbing motion, which extends about 250 light years above and below the plane, is determined by the concentration of gas and stars in the disk of our Galaxy.
This ordinary “baryonic” matter is concentrated within about 1000 light years of the plane. Because the density drops off in the vertical direction, there is a gravitational gradient, or tide, that may perturb the orbits of comets in the Oort cloud, causing some comets to fly into the inner Solar System and periodically raise the chances of collision with Earth. However, the problem with this idea is that the estimated galactic tide is too weak to cause many waves in the Oort cloud.
In their study, Randall and Reece focus on this second hypothesis and suggest that the galactic tide could be made stronger with a thin disk of dark matter. Dark disks are a possible outcome of dark matter physics, as the authors and their colleagues recently showed. Here, the researchers consider a specific model, in which our Galaxy hosts a dark disk with a thickness of 30 light years and a surface density of around 1 solar mass per square light year (the surface density of ordinary baryonic matter is roughly 5 times that, but it’s less concentrated near the plane).
Although one has to stretch the observational constraints to make room, their thin disk of dark matter is consistent with astronomical data on our Galaxy. Focusing their analysis on large (>20km) craters created in the last 250 million years, Randall and Reece argue that their dark disk scenario can produce the observed pattern in crater frequency with a fair amount of statistical uncertainty."
For those already familiar with Lisa proposal. It's nothing new.. but I just learned about this last night... now to get in the mood. Lisa commented in the same url "“If you were to look at our world and assume there was only one type of particle, you’d be pretty wrong,” said Randall. “I think it’s definitely a worthwhile theory to explore, because even if this is only a small fraction of dark matter, there is six times more dark matter in the universe than ordinary matter. We care a lot about ordinary matter, and that’s precisely because it has interactions. So if there is a small portion of dark matter that has those interactions, that may be what we should pay attention to, perhaps even more so than other dark matter.”
Now my question.
What if 0.5% of dark matter has interactions with matter yet doesn't affect the cosmos gravitationally. For example.. supposed, just for sake of discussion (note this is just for sake of discussion, ok?)... life has evolved in the dark matter sector and these produced the jinns of myth and legends (said to be made of "smokeless fire" and different from matter)...
And let's say these jinns don't affect the gravitational behavior of the galaxy or solar system or even planets.. can these beings still be referred as dark matter? If not.. then these can be referred to as normal baryonic matter but only invisible? Supposed one needs to address this to the world physicists as intel briefing.. must dark matter be used or invisible normal baryonic matter to describe them? Again this is just an example because I can't think of one right now although i'll watch more dark matter videos in the youtube to give more accurate descriptions or examples.
Galaxies and galaxy clusters are distributed in such a way as to roughly mirror the distribution of dark matter, so you'll often see long filaments of dark matter "connecting" galaxies together over cosmological distances. However, nothing is connecting individual star systems to others.
