Dark energy is everywhere. Yes, really.

Pick ten random items. Odds are, seven of them will be dark energy. Scary, isn't it? And yet, absolutely true.

Of course, we're using the term "items" loose here. You can't really pick up dark energy, despite its omnipresence. As our universe expands, dark energy is what fills the empty space. It takes up 70% of, well... everything.

(For those curious what the other 30% make up, it's 25% dark matter, 4% intergalactic gas, which leaves about 1% for stars, neutrinos, and, you know, stuff you can actually pick up. That comes in at .03%. We truly are insignificant specs.)

In any case, dark energy was discovered simultaneously in 1998 by two groups, both led by Jews: previously-profiled Saul Perlmutter and currently-profiled Adam Riess. Which is all fantastic, but leaves one question open:

If dark energy is indeed everywhere, why was it so hard to discover?