Dark matter and dark energy equivalence?

Question

Given that matter and energy are related by E = mc², could the same or similar be true of dark matter and dark energy?

Answer 1

Sadly, it is not that straightforward. And perhaps dark energy is a bad name.

The observation that has led to its postulation is that the expansion of the universe is accelerating, not slowing as might be expected.

Other observations have already indicated the presence of mass in the universe that interacts through gravity but NOT the electrostatic force (dark matter - a good name, because it does nto interact with light).

The acceleration of expansion was a surprise though.

In general relativity a term was added by Einstein called the cosmological constant to allow for solutions to equations for gravity that allowed a static universe. However, this constant can also be adjusted to give the observed rate of expansion. In this case it is equivalent to a constant contribution to the vacuum energy. It is then excluded from other contributions to gravity (ie by E = mc^2) which would lead to double counting otherwise.

Answer 2

In cosmology

dark matter is a term used to describe matter in the universe that cannot be seen and does not interact with the electromagnetic force but can be detected by its gravitational effects on visible matter.

dark energy is a hypothetical type of energy that may make up 65 % of the Universe it is gravitationally repulsive, due to a negative effective pressure it plays a role in the acceleration of universe's expansion.

I think that there is a considerable similarity or analogy.

Answer 3

Unlikely, the distribution of it is wrong.  You're correct that technically the terms dark matter and dark energy mean exactly the same thing.  But in astronomy/cosmology lingo, they refer to two different phenomena that are probably unrelated.

Answer 4

The dark matter does have an associated rest energy according to E = m c².

However, this is not the same thing as the "dark energy" that we talk about in cosmology. Just because we use the same adjective "dark," to indicate that we have to observe these things indirectly, doesn't mean that they are the same objects. We just have trouble seeing both of them: we see the dark matter only by using gravitational observations (since photons don't interact with it), and we see the dark energy only by looking at the rate at which the universe is expanding.