timmdeeg said:
To say "we know nothing about the dark matter more so dark energy" isn't quite correct.
I think the point is that we don't have a good understanding of the properties and nature of what causes the phenomena attributed to dark matter and dark energy, in other words, their physical mechanisms. We can fit them to parameters in an abstract model, but that is about it.
Viable proposals for dark matter range from axion-like particle dark matter made of particles a thousand to millions of times less massive the neutrinos to primordial black hole candidates with masses on the order of asteroids. In some theories it is completely collisionless and doesn't interact at all with anything other than gravitationally, while in others dark matter interacts with other dark matter nearly as strongly as a short-range version of the electromagnetic force. In other theories, it even has slight non-gravitational interactions with ordinary matter (which are weaker than the weak force, but stronger than gravity). There are viable proposals to explain dark matter phenomena with gravitational modifications as well.
We know a lot about what dark matter is not. And, we have some rough outlines of how it behaves. But there is very little we can say definitively about what it is.
The situation is better with dark energy, and it isn't really fair to say that we know nothing about it, although the certainty of that knowledge shouldn't be overrated.
To a rough approximation, dark energy acts as a constant energy density per volume in the Universe in otherwise empty space, that grows as the size of the Universe grows.
This may not be exactly right. Indeed, there are lots of strong observational hints that it isn't exactly right, although none to the strict standards that astrophysicists would require to consider the plain vanilla cosmological constant in the GR equations hypothesis disproven. But, while there are a variety of explanations, mostly, they aren't terribly dissimilar to each other.
It is also worth noting that while the "70% of the mass-energy in the Universe is dark energy" is a pretty overwhelmingly way to think about it, that intuitively you would think would have a huge impact on daily life, dark energy effects are quite subtle. In terms of mass-energy per cubic meter
it is estimated to be:
So, about the same mass-energy as thee and a half hydrogen atoms per cubic meter. This turns out to be negligible for calculations even at the scale of an entire galaxy, particularly because the effect cancel out at the scale since the distribution is the same in all directions.
By comparison, a cubic meter of water has a mass of 1000 kg and has about 3.33*10
28 oxygen atoms and 6.66*10
28 hydrogen atoms.