4 ms·
>The idea that there exists some "stuff" we can't measure (except weakly via observed gravitational effects) that is ~5-6 times the stuff we can measure and int
by AgentME 6y ago
>The idea that there exists some "stuff" we can't measure (except weakly via observed gravitational effects) that is ~5-6 times the stuff we can measure and interact with seems a bit problematic.
This seems to be a common intuition, but is it founded at all? Why should the idea that there's more mass that's weakly-interacting than we're used to be a point against it? Should we have any expectations about the amount of mass that's interactable with us in regular ways we've evolved to deal with?
If we evolved in dark caves to be blind creatures with sensitive hearing and no concept of light, then when we first considered the possibility of outer space, would we be right to write it off just because it supposes that most matter couldn't possibly be heard by us?
If we imagined that all particles we know about may be made up of some smaller building block particles connected together, or concentrations of some kind of stuff, wouldn't it actually be more surprising if all of that building-block stuff had ended up becoming concentrated into normal particles? This might not be literally how it works, but it's interesting that it seems easy to imagine plenty of possible ways the world could be where it turns out that most building-block stuff is never pushed to combine into normal mass, and instead most of it stays in an uncombined form that's only weakly-interacting.
- Ma8ee 6y agoI think that it is supposedly a lot of something that hasn’t been predicted or detected in any other way that is considered problematic. It has to interact at least with other dark matter in some other form than via gravity to clump together.
- spiralx 6y agoDark matter doesn't clump together though, that's part of what makes it different to light matter.
- Ma8ee 6y agoHow come it stays in the vicinity of other matter? It needs to lose kinetic energy somehow.
- sobani 6y agoThe universe didn't form uniformly, so if a bunch of dark matter formed as a clump, it would remain like that. Also dark matter is gravitationally affected by light matter, which does interact. My intuition tells me that the interaction of light matter that creates clumps of light matter will also create clumps of dark matter indirectly. * note: 90% my dark matter knowledge comes from HN. I'm just spitballing here
- Ma8ee 6y agoWhat happens to a comet that enters the solar system if it doesn’t hit anything? It leaves the solar system with the same speed it entered it with. Dark matter cannot hit anything.
- AgentME 6y agoDark matter halos are often found around galaxies, extending far past them. The dark matter fails to stay within the galaxy because it's not slowed down by regular interactions. Also, dark matter is able to pull regular matter to be closer to it. If a galaxy's dark matter is moving too far away from a galaxy, it might pull the galaxy with it. (Or it might separate entirely, as happened with the Bullet Cluster.)