The strongest evidence for dark matter is the interactions between clusters and superclusters of galaxies, and for the rotational speed of galaxies (for the rim to spin so fast, there must be tons more matter than we think). Dark matter does NOT have to be mass-less, for the neutrino (a type of neutral cosmic electron) was part of the "dark matter", but after being discovered, it was proved to have mass.
Dark Matter - particles and stuff we don't know about yet because we don't know how to detect it.
Moose, light will NOT travel faster than c, it will NOT, no matter what. If you run at a light source at the speed of light, that light you're running at will not be traveling at you at 2c, it'll be traveling at c.
T' = T (1 - c)
This means that the time elapsed for a person traveling at something c (like 0.9c), for say, 20 seconds for someone watching them stationary, will actually seem like 2 seconds for the person traveling. This is also the basis for spacetime, for when you bend time like this, you also bend space. For the person standing still, in those 20 seconds, the traveling person traveled 6 million kilometers. For the person traveling at 0.9c, that same distance is actually 600,000 kilometers, one tenth of the stationary person's measurement. How can this happen? Bending spacetime, you can travel an infinite amount of distance in as little time you want (you can travel at 0.9999c, and travel a million kilometers [to a stationary person] in only 0.0003 seconds, but you will measure the same distance as only 90 kilometers). This means you can travel to the other side of the universe in the tiniest fraction of a second if you wanted to, but it'll still seem like forever for a stationary person. What gets REALLY confusing is special relativity, which states that no one has the right to say that they're moving and someone else is not, which means that how do you know which person is experiencing what time change? The answer is unbelievably crazy, I learned about it, and it went into one ear and out the other. Supposedly, when something like the example happens, it already happened in the past, and is being experienced a time after it started (does not have anything to do with fate...). It's like, when the person starts traveling, time for the stationary person is I think in the past (I really can't remember at all...). I don't know, whatever, I'm not Einstein...
If you want to scratch your noodle (no Paul, not
that noodle!), then you may want to read this:
http://superstringtheory.com/
It's called the Superstring Theory, and states that all matter are not "particles", but are tiny vibrating strings. Do I believe it? Pfft, who knows...
Oh, and dimensions exist... we live in the 3rd and experience the 4th.
