[sithcdw (OP)]

Alright, scientists have determined that most galaxies simply do not have enough matter to produce the gravity needed to hold them together. They hypothesized that something must be conctributing to the galaxies gravity; and of course the only thing that can produce gravity is matter. So scientists dubbed this unviewable matter  "dark matter".

We know there isnt alot of "stray" matter in the universe. It pretty much has all "bound" together by gravity over the course of our universe's life (galaxies, nebulas, etc.).

My question is this:
What if this dark matter is "actual" matter, but just in an alternate dimension or universe? Perhaps there are alternate realities within or own space-time blanket. What if our galaxies are "wrapped" around curvatures in space-time that are actually alternate unvierses? What if the matter within these alternate universes attract the matter within ours? Is that possible? Couldnt that also contribute as to why this supposed "dark matter" does not interact with electromagnetic radiation? And since most of our universe is said to be dark matter is it possible that we are a smaller universe within a much larger one?



Mod edit - I've altered your title to be a question - please can you do this in future to help keep the forum tidy and easy to navigate?  Thanks!

[Soul Surfer]

There is absolutely nothing unusual about the existence of dark matter.  In fact I am surprised that its possible existence was not expected before its discovery. Consider the sorts of particles we have.  We have the familiar electromagnetically interacting particles protons and electrons then we have neutral particles that interact only with strong or weak interactions neutrons and neutrinos respectively.  All these particles interact gravitationally but the effects are too small to have any observable interactions.  It is therefore perfectly normal to expect that there will be particles that interact only gravitationally.  Such particles are those comprising dark matter.  Dark energy was a bit of a surprise but it is probably just a way of expressing the energy within these dark matter particles.

[graham.d]

There is absolutely nothing unusual about the existence of dark matter.  In fact I am surprised that its possible existence was not expected before its discovery.

I don't think I would go that far SS. The idea of WIMPs (Weakly Interacting Massive Particles) is quite contraversial and nobody really knows what the nature of DM is. However I guess your point is, and I agree, that DM is a whole lot simpler explanation than the ones suggested by sithcdw.

SS there is no reason to suppose that DM and Dark Energy (DE) are related in any way, except in the sense that they both seem to be part of the universe. The phenomena are wholly unrelated except that DE was given an unfortunate name that keeps confusing people.

Sithcdw, many things are possible but very few probable. When a phenomenon is found there are an infinite number of possible explanations. Generally speaking it is better to examine the simplest ones first and eliminate those that do not fit the facts. If we do not do this we are in the infinite realms of science fiction.

It is not that dark matter is needed to hold galaxies, or clusters of galaxies, together but rather that the distribution of the mass in these structures and its variation in velocity with distance from the centre of rotation cannot be explained without DM. The basis for this is the virial theorem and measurements speeds (via Doppler shifts) and mass estimation (from brightness and other factors).