Dark means invisible to the eye or electron mocroscope.\nDArk matter= masseless?
214704
This is a very intriguing question which I plan on researching. I have a conception of light and its physical properties and also the tremendous mysteries of a 'Black Hole'Where current day Physics is just beginning to grasp.NOTHING escapes the gravity of a 'Black Hole',not even light!Through the efforts  of dilligent astronomers, one was actually 'seen' and filmed as it passed in front of a known group of stars...outlining the very hole itself.(like passing an object in front of a bright light source and observing the outline of the object...i.e. Solar eclipse...,) knowing of there existence and how to track them now ,has given a whole new meaning to the destructive forces of a 'Black Hole' as it swallows up Stars, that Dwarf our Sun in comparrison,and the Solar System it may support.This is Truly Dark Matter on the 'Anti' side...Anti-matter...a Black Hole is given birth by a Star,such as our Sun, that is dying.As this Star,once a source of Light that supported a probable solar system, goes through its Final death throws it eventually explodes, but it just doesnt explode! as its  surface layers are  blasted outwards, its  core is smashed inwards. The center of the star  collapses in on itself. Billions upon Billions of tons of Star stuff crushed smaller and smaller until the whole Star is squeezed to a microscopic point,and from the remains of the dying Star, ....a BLACK HOLE is born....in our Galaxy,the Milky Way, a Massive Star explodes and creates another black hole every 1000 years. There is a estimated 10 Million Black Holes roaming our Glaxy today, creating Havoc sucking matter in around them... NOTHING escapes! As we know, anything of SUBSTANCE has mass, microscopic as well as Galatic.Once realized that the incredible forces hatched by a black hole having the ability to bend light and distort the Space/Time continuum which in itself is invisible to the eye, is it a possibility that this very same process is taking place at a molecular level? If manipulated correctly, is 'Cloaking' a possibility? your Question is very intriguing indeed!
345598
eye = light \nears = sound\nnose = chemical
504653
1) darkness or a shadow\n\n2) the sides of it
208297
Assuming they are completely blind, it's like having no eyes at all, in which case they would "see" nothingness.  Blackness would indicate an ability for your eyes to pick up at least some form of light, and completely blind people can't pick up any forms of light at all.
30748
Dark.\n\nJ.R.R Tolkien rules.
301450
A black object is only visible when surrounded by light reflecting items.  Example: if you wrote on a completely black piece of paper with a black marker you would not be able to see it, but you would if it were white paper
143806
You have to remember these are descriptions based on experiments. Light can act as both- as do other particles. Keep in mind that the map is not the territory.....
277052
We choose many things as convention. For example, we look at heat flowing from hot to cold. So to cool down a room, we remove heat instead of add cold. To heat a room we add heat instead of remove cold.\n\nElectricity is the same. By convention, we look at it as the movement of electrons. But, sometimes it's more beneficial to look at the positively charged holes left by the electrons. They move in the opposite direction at the same speed.\n\nSo it is by convention that we look at the movement of photons as the direction of light. We could just as easily look at a light as a dark sucker and thus the dark would recede at the same rate that the light moves out.
387168
Yes. Since black is absence of color, absence of light, it is often seen as evil because darkness suggests the unknown. People fear the unknown. Therefore, they conclude, that black is evil because they fear evil. But the unknown is only unknown until someone or something sheds light on it. Then, we often find that those things hidden to us are not always as scary as we seem to think they are.
610647
IANA Physicist, but....\n\nWe're not really sure.  The assumption that they exist is based on the fact that there isn't enough visible matter to keep the universe in the state that it's in.  That is, in order for the universe to behave in the manner that it is, there should be enough matter to generate the proper amount of gravity, but we can only see about a third(?) of the amount of matter required.  Therefore, the rest of the required gravity must be coming from matter that we can't see, hence - Dark Matter.
94137
In cosmology, dark matter refers to hypothetical matter particles, of unknown composition, that do not emit or reflect enough electromagnetic radiation to be detected directly, but whose presence can be inferred from gravitational effects on visible matter such as stars and galaxies. The dark matter hypothesis aims to explain several anomalous astronomical observations, such as anomalies in the rotational speed of galaxies (the galaxy rotation problem). Estimates of the amount of matter present in galaxies, based on gravitational effects, consistently suggest that there is far more matter than is directly observable. The existence of dark matter would also resolve a number of inconsistencies in the Big Bang theory, and is crucial for structure formation.\n\nIf dark matter does exist, it has vastly more mass than the "visible" part of the universe. Only about 4% of the total mass in the universe (as inferred from gravitational effects) can be seen directly. About 23% is thought to be composed of dark matter. The remaining 73% is thought to consist of dark energy, an even stranger component, distributed diffusely in space, that probably cannot be thought of as ordinary particles. Determining the nature of this missing mass is one of the most important problems in modern cosmology and particle physics.
221514
The universe is theorized to contain dark energy and dark matter. There have been some confirmation of it's existence but really just speculation at this point. The idea of dark matter had been identified by Einstein but it wasn't till the discovery that the universe is accelerating it's expansion and contains up to 70% more matter that the idea of dark matter and energy became serious areas of study. If you mean a vacuum to mean absence of air it is a vacuum but within that "vacuum" there definitely is matter.
55757
Energy = mass times the speed of light squared\n\nIt conveys that a very small amount of matter actually represents/can be turned into a very large amount of energy, as in nuclear power, or a nuclear explosion.
20026
The correct answer is that no one knows.  We don't even know what most of the universe is made of (right now it's being called dark matter, because all we know about it is that we can't see it).\n\nIf I had to make a bet, I would go with total energy equals zero.  \n\nThere is a lot of matter in the universe, as everyone is saying, and that makes for a lot of mass energy.  But, the flip side is that there is a lot of mass in the universe, and that makes for a lot of negative gravitational potential energy.  It is possible they cancel.
93705
light has mass....light is made up of photons....light has both wave and particle properties...rest mass of photon is zero and that the effective mass of photon is about 5.42MeV in the symmetric nuclear matter at the saturation density ρ0 = 0.16fm-3 and about 2.0MeV at the surface of }238U.
39698
There's more than one: light, a hole, darkness, and shadows to name a few.  Also a hallucination.\n\n*Yankeesrock26ws, air actually does have mass, it's just that it's effectively constant on Earth so we tend not to notice it.\n\nhandsome_stranger wrote:\n>>>actually light can be changed to mass so i think it is not a good >>>answer\nBut then it's not light anymore.
380073
There is actually no such thing as "cold". What we mean by cold is really the "absence of heat". The heat is what is flowing out of your hand and into the ice, causing the ice to melt. Cold does not flow because cold does not exist. \nWhen I was in college we decided that it would be fun to invent the "electric dark bulb". It would shine darkness out in all directions, leaving well lit shadows behind objects that got in the way of the dark rays. But try as we might, we could never get a bulb that would shine dark rays. Cold is like that. I wish Arnold Schwartzenegger had known this when he decided to attack Gotham City with his freeze ray. It was doomed from the start, whether Batman showed up or not.