Depends what you mean by "significance."
We know there is SOMETHING out there in our Universe that exerts a gravitational force but does not otherwise interact with ordinary, baryonic matter. However, we do not yet know what this stuff IS. So, in the same way that highly penetrating rays are still called 'X' rays -- even though they are no longer so mysterious that we need to give them the moniker 'X' -- we presently call this stuff "dark matter."
When we finally are able to figure out what dark matter is, it will most likely radically change our understanding of the nature of our Universe -- in the same way that x-rays did.
It may turn out that dark matter will have no effect on our daily life. Or, once we understand what this stuff is, it may turn out to be as important to us as x-rays are today. In that sense dark matter may or may not have much "significance" to most people.
Many theories were already said and explained, and I don't think people would use their brains to do this, soooooo. I'm just gonna do a theory that has already been explained.
There is still not a lot of direct evidence supporting the claim that dark matter is real. All we know is there is an invisible force that can affect a matter's gravity.
So the theory is that Dark matter is real, that's all folks.
Dark matter doesn't emit light, nor does it interact with light. It is therefore hard to detect. So far, it has only been inferred by the effect of its gravitation.
Other Comment: Dark matter cannot be directly detected; i.e. it neither emits nor absorbs light or other electromagnetic radiation at any significant level. Instead, its existence and properties are inferred from its gravitational effects on visible matter, radiation, and the large-scale structure of the universe.
Since dark matter is pretty much defined as "the stuff, whatever it happens to be, that explains the observed rotational velocities of galaxies, as well as the observed gravitational curvature of space," I would say its existence is more than just conjecture. Exactly WHAT it is composed of, is still a matter of study.
Whether you want to call it a "law" or a "theory" (which, BTW, in science does NOT mean "an unsupported hypothesis") is up to you.
The big problem is that there isn't a theory of dark matter, there are lots of theories about dark matter, and we don't know which if any of them are true.
Could be WIMPs (weakly interacting massive particles ... just to clarify, "weakly interacting" in that phrase means "interacting through the weak force"), could be something to do with supersymmetry or string theory. Nobody really knows.
It interacts with other matter only by gravity.
There's no such thing as a "dark matter microscope." The whole point of dark matter is that it doesn't interact with electromagnetic radiation... if it did, it wouldn't be dark matter.
Dark matter's strength is proportional to it's mass. This means that more dark matter in one spot is stronger then a little bit of dark matter in that same spot.
Dark Matter - series - was created in 2004.
At present we do not know. It might be almost motionless, it might have a high velocity, it might have a velocity near that of light. These three hypotheses of the nature of dark are called (respectively); cold dark matter, warm dark matter, and hot dark matter.
The Universe contains matter, energy, dark matter, dark energy, empty space - and of course, lots of structures made up of those.The Universe contains matter, energy, dark matter, dark energy, empty space - and of course, lots of structures made up of those.The Universe contains matter, energy, dark matter, dark energy, empty space - and of course, lots of structures made up of those.The Universe contains matter, energy, dark matter, dark energy, empty space - and of course, lots of structures made up of those.
There aren't any. Even the smallest particle of the dark matter theory, the axion, is quadrillions of times more dense than an electron.
Dark matter is everywhere, there really is no place that has the most dark matter.
Dark matter is an unknowm form of matter.
There's no such thing as a "dark matter microscope." The whole point of dark matter is that it doesn't interact with electromagnetic radiation... if it did, it wouldn't be dark matter.
The opposite of dark matter is visible matter.
Matter
Dark matter's strength is proportional to it's mass. This means that more dark matter in one spot is stronger then a little bit of dark matter in that same spot.
dark matter
Dark matter is invisible. It doesn't interact with light.
Dark Matter - series - was created in 2004.
Hooray for Dark Matter was created in 2005.
Cold Dark Matter was created in 1992.