I think it's funny -- "both haha" funny and "strange" funny -- that we have almost no clue about 72% of the Universe.
That nearly 3/4 chunk of the cosmic budget is dark energy, the mysterious force (or pressure, really) that appears to be making the expansion of the Universe accelerate. We've known the Universe is expanding since the early 20th century, but everyone assumed, logically, that the combined gravity of all the objects in space was slowing the expansion, like tension in a rubber band.
Then, in 1998, two independent teams of astronomers and physicists found out that not only is the Universe not slowing its bloating, but in fact is bloating ever-faster. This turned physics on its head and even now, on this 10th anniversary of the discovery, we're still trying to figure out the basics of the phenomenon. We don't know what's causing the acceleration, we don't know what this energy is, what form it takes, nothing. All we can do is observe its effects and speculate.
If you're confused about all this, it's totally OK-- we are too. But we do have some clue about what's going on, and there's a lot going on. People, smart people, are on the case, and plans are being made. Telescopes targeted to study dark energy's effects are in the works, for example. Particle accelerators like the LHC may reveal clues. Your tax dollars (and others') are at work here.
One way scientists are spending money is on making sure you, the public, know as much about this as you can. So NASA created the Joint Dark Energy Mission website, which has info on this matter. JDEM is a space-based astronomical mission that will involve both NASA and the U.S. Department of Energy -- because they have a lot of expertise in the field of particle physics and the basic forces ruling the Universe-- and will be designed to look to the farthest reaches of space where the effects of dark energy are easiest to see.
The website is still a little sparse, but it does have links to sites with more information about the history of the discovery of dark energy (which is actually pretty interesting) and the science of it as well. It's Friday, and admit it: you're bored at work. Why not investigate one of the biggest current mysteries in all of science?
Addendum: I know this'll sound like I'm making it up, but I'm not: it was only after writing this that I realized I do talk about dark energy in the new book, since it has a huge role in how the Universe evolves over trillions of years, and even longer periods of time. Much longer. I don't go into huge detail in the book, but I explain how this plays into the eventual death of the cosmos itself... and maybe even its rebirth.