Dark Energy is the name for the phenomenon an accelerated expansion of the Universe. This was measured by observing distance and velocity of distant supernova, and later also with other techniques (galaxy clusters for exampl). Dark Energy is the additional energy available for driving this, which is not accounted for in light-emitting baryons.

What causes the Dark Energy is another question, and that, indeed, has not been solved ("proven") to date.

> here has never been any proof that dark energy actually exists,

By definition. "Dark Energy" is like Terra Incognita, or "10th Planet".

It is a placeholder for something hypothesised, but not yet discovered.

> As far as I know, there has never been any proof that dark energy actually exists, only theories only conjectures.

Dark Energy , and Dark Matter, aren't really theories in the sense we usually use in science. They are placeholders to describe missing variables in the math used to describe gravitational behavior as it deviates from the otherwise highly reliable Einsteinian and Newtonian accounts for it.

Dark Matter, because the maths and observations seem to show a *lot* more mass in galaxies than we can accou

Writing derogative statements is easy. Coming up with better theories is hard.

So you are taking the easy way out, the Ignoramus Ignorabimus.

Special relativity models constant lightspeed pretty well, general relativity models gravitational lensing pretty well and builds on the former. Those can be experimented with on earth or with observations near the sun in the sky, you don't need any three degrees of separation cosmology.

How can dark matter account for dark energy? Dark matter generates gravity while dark energy pushes matter apart. Wouldn't more dark matter require more dark energy to accommodate?

Dark energy and dark matter were not "invented". And any physicist worth his/her/its salt will tell you that. For the umpteenth time (and read the responses above), dark energy and dark matter are merely place holders in equations that say, "something goes in here but these are the properties it must fulfill to earn its place in place of these place holders." Why is that so difficult for you to understand?

A big crunch very well may create a black hole. But they are orthogonal concepts.

> how different from a "big crunch" is a black hole?

It is a matter of time and space. If you are inside a supermassive black hole, you have at best days to live. Outside, you have many billions of years.

Sure, the result is the same, but I have a preference.

In both cases, all world-lines converge. One space-like and local, one time-like and universal. For a better answer, the maths is beyond my comprehension horizon.

A black hole is an object of some kind that exist in "normal" space, whatever that is.

Depending on which philosophical interpretation of gravity you embrace, it either has a "singularity" inside it, which exists because its gravity distorts the space around it (and the sticks you measure it with) to some infinity; or a real object, which looks "distorted" to you because you perceive it with sticks that are distorted by its gravity.

The difference to you is nil, though, because outside of some fringe issues (

Try investing in land in Florida. Now that la Presidenta has canceled global warming with a swish of his Sharpie, it is safe to put all your money in there. Better yet, buy an acre in Florida, excavate a reasonable sized hole, and dump your money in. If you cover it up real fast no one will know where you hid it. You don't even have to worry about hurricanes now due to la Presidenta's Sharpie Woo.