Despite all of the incredible things humans have figured out, we don’t know everything.

1. What’s inside a black hole?

We’ll probably never know. Nothing can communicate from inside of one—light, radio waves, anything. Even if we could send something (like a signal) into a black hole, we couldn’t get it back. The closest thing we have to an answer employs two established theories (gravity and quantum mechanics). Scientists even have a name for this combined theory—quantum gravity—but they still don’t get how it works. For now, they think everything sucked into a black hole is bunched up and stacked on top of itself in its center, like a big, galactic dogpile. Other people think black holes could be a gate to another universe. But until someone goes into one and comes back? No idea.

2. Why do we have an appendix?

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Total mystery! It’s just there (unless you had it removed). A 2007 issue of the Journal of Theoretical Biology posited that the vestigial organ once acted as a storehouse for “good” bacteria, so when pre-medicine bodies were hit with dire illnesses affecting the gut, an appendix could help repopulate the stomach with disease-fighting bacteria. Scientists agree that this guess is as good as they come, but the author of the study admitted there’s no way to confirm it without a “very expensive, heinous” experiment that might involve infecting people who don’t have access to modern medicine with dysentery. No thanks!

3. What’s the CIA hiding about JFK’s assassination?

Abbie Rowe. White House Photographs. John F. Kennedy Presidential Library and Museum, Boston.

Maybe nothing—or not. In 1963, Lee Harvey Oswald applied for a visa to travel to Cuba, via the Soviet embassy in Mexico City. The CIA picked up on it. Five senior CIA officers signed off on a cable basically saying Oswald wasn’t a concern (whoops). Of the approximately 3,600 JFK files that remain sealed in the National Archives, 1,100 concern the CIA. And while the JFK Records Act of ’92 mandated all files related to the assassination be released in 2017, it also holds provisions that if the files could potentially compromise national security upon release, they can remain classified ... of course.

4. Does Tony die in The Sopranos finale?

Alamy

In the most infamous last scene in TV, Tony Soprano eats onion rings to “Don’t Stop Believin’” in a sketchy New Jersey diner, then...nothing. It cut to black. Outrage and conspiracy theories abounded! Show creator David Chase was mostly mum on it until an April 2015 Directors Guild of America interview: “I never considered the black a shot. I just thought that what we see is black. The biggest feeling I was going for ... was don’t stop believing. Life is short. Either it ends here for Tony or some other time. But in spite of that, it’s really worth it.” In other words: You’ll never know.