What is the difference between dark matter and dark energy?

Answer 1

The two are quite unrelated. It would be harder to find similarities than differences.

More exactly, the two are only related by the fact that (as of 2013) we don't understand either -- thus the name "dark."

Dark matter is the type of matter that exists throughout our Universe, which interacts with baryonic matter (ie, the stuff we understand) only through gravity. This stuff (whatever it happens to be) warps space and prevents galaxies from flying apart as they spin; but does not interact via the electromagnetic force, the strong force, or the weak force. Its mass density in our Universe, as best we can tell, is about six times greater than that of bayronic matter.

Dark energy is whatever is causing the space within our Universe to increase the rate of expansion. Gravity SHOULD be slowing down that expansion over billions of years, but SOMETHING is causing the rate to go higher. What is causing this? -- we have no idea!!

Answer 2

I just read an article from Hubble site on the theoretical idea of dark energy, it implies that due to the dimming of light emitted contrasts of supernovae from different time periods such as 1 2 3 4 5 billion years apart they theorized that the invisible must be pulling apart the mass of universe because the dimming from these supernovae are not the same and they should be.

Well here is what i think, if anyone believes that the invisible, dark matter, space what ever you want to call it, is responsible for expansion of universe, you are nuts. First of all, nothing gives you nothing. If one is to believe that dark space is energy then the nuclear age is a myth and all scientific formula need thrashing or perhaps there must be alternate ways of starting universes. What!

If one is to accept the idea of dark energy then one must forget the laws of physics such as the laws of conservation and thermodynamics.

Maybe if the nothing exists and it is energy then it would explain all the ghost stories I have heard.

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The previous paragraphs demonstrate a profound lack of understanding of the nature of science.

The space within our Universe IS expanding. This is as much a fact about our Universe as gravity. Don't like this fact? Too bad -- you'll just have to move to a different universe, because it IS occurring here, no matter what you may think of it.

The laws of General Relativity show that matter within our Universe should slow down this expansion. The only question is HOW MUCH is the mass in our Universe slowing it down. Ever since Hubble Expansion was first discovered over eighty years ago, we've noted that the rate of expansion seems to be constant over many billion years, so the amount of mass in our Universe (more precisely, the DENSITY of mass in our Universe) is very close to almost no slow-down over time. Again, don't like this fact? - then you'll have to leave this universe.

> if anyone believes that the invisible, dark matter, space

> what ever you want to call it, is responsible for expansion of universe, you are nuts.

Dark matter and dark energy are completely separate entities. One of them (dark matter, since it is gravitational) would cause the expansion of our Universe to slow down. It's dark ENERGY that's causing the expansion rate to speed up.

In the 1990s, we FINALLY developed a "standard candle" (look it up) to precisely measure the rate of expansion of very distant galaxies -- ie, ones that were part of expansion many billion years ago. With this, it was hoped that we could FINALLY see how much the mass in our Universe was slowing down the expansion of the Universe.

What we found was that the rate of Hubble Expansion has NOT been decreasing over time -- it has been INCREASING.

What's causing the rate of Hubble Expansion to increase over time? WE HAVE NO IDEA!! Some form of energy, about which we have no clue, is causing the rate of expansion of the space in our Universe to go faster over time.

We call it DARK energy precisely because don't understand it.

> If one is to accept the idea of dark energy then one must forget the laws of physics

This, at least, is correct. To understand dark energy -- whatever it happens to be -- we WILL have to forget the laws of physics AS WE NOW UNDERSTAND THEM. Believe it or not, our understanding of our Universe -- what we call the "laws" of physics -- CHANGES as we acquire new information. 100 years ago, we didn't even know galaxies existed, let alone that we were at the periphery of one, let alone that the space between our galaxy and others was expanding, let alone that the rate of this expansion was increasing over time. Each of these concepts -- and hundreds of others -- were uncovered due to well-done experiments, and forced us to re-write the "laws" with which we use to deal with the Universe we find ourselves in.

> First of all, nothing gives you nothing

Actually, we now know, as an absolute fact, that empty space, even if completely devoid of matter, is teeming with energy. And it does so with no violation of conservation of energy whatsoever. Don't like this fact? I think you know the answer.

Answer 3

Dark matter is a name given to matter from which we see its gravitational influence (through astronomical observations) but we do not see the matter itself. It is therefore called dark matter as opposed to light matter such as stars. We do not know what dark matter itself is; it may consists of particles or objects we have no knowledge of today.

The Higgs boson is a particle predicted by theories of particle physics, but it is not a dark matter candidate (i.e. not a particle that can reasonably explain the large amount of dark matter we see).

Dark matter candidates are for example heavier particles (arising from for example supersymmetry), primordial black holes and even heavy neutrinos.

Answer 4

Dark Energy is a strong repelling force that drives all matter not held strong enough gravitationally to each other apart. Dark Matter is a form of matter that only interacts with other matter gravitationally, and hence is invisible and undetectable other than its force to keep galaxies together.