It happened exactly 30 years ago. Remember?

It was the day a page turned in the baseball record book that once seemed unturnable. And it brought together, on the same firework-speckled stage, two fabled figures named Peter Edward Rose and Tyrus Raymond Cobb.

At the moment Rose's 4,192nd hit dropped into the empty spaces in left field and Cobb descended to No. 2 on the all-time hit list, the legacies of those two men seemed so clear. Rose was one of baseball's most beloved figures. Cobb was one of its most reviled.

Yes, it was all so clear -- until it wasn't.

Thirty years ago, when Pete Rose became baseball's all-time hits leader, who would've ever thought he'd be in the position he's in now? Rich Pilling/Getty Images

Three decades later, think how much has changed. Three decades later, it's Rose who has become baseball's biggest outcast. Three decades later, a remarkable new book has made us reconsider the endlessly repeated narrative of Cobb as baseball's ultimate, spike-sharpening racist.

There's a lesson in there someplace for all of us. Let's talk about it. Let's think about it.

We want our heroes to be saintly and cool, handsome and funny, likable and real. So when a guy like that comes along, we latch onto him. We root for him. We distance him from the bums, the cheaters, the scoundrels and the egomaniacs.

We write fairy tales in our heads where good and evil are sharply defined. We're sure we can always tell the difference, distinguish the good guys from the bad guys, know exactly who should wear the white hats and the black hats.

If only that were true. If only it were that obvious, that uncomplicated.

Rose was so easy to like, so easy to pull for. He was the Hit King and the quip king. We debated if he'd be the first unanimous Hall of Famer. As he belly flopped through the dust, he seemed to represent everything that was right about baseball.

And then his tale began to turn, becoming the sad story of a man who committed baseball's most serious crime -- betting on baseball games. Of a man who was banned for life, ostracized from the Hall of Fame, sent to prison, consigned to a world of card shows and casinos, all accompanied by a soundtrack of his never-ending pleas of innocence.

Wow. How'd that happen?

If someone had told you, back on Sept. 11, 1985, that that's where the next 30 years would be leading Pete Rose, how hard would you have laughed? How fast would you have replied: "Sober up?" How impossible would it have been to believe any of that?

And then there was Cobb. He was baseball's first transcendent star, the first man elected to the Hall of Fame (with more votes than Babe Ruth, by the way), one of the most talked-about personalities in turn-of-the-century America. But ...

His dark side was always there, always hovering. His bursts of anger, his willingness to use his fists to get his point across, his deliberately intimidating style of play made him a lightning rod in his time. But how much of what people thought they knew about him was actually true?

Tales spread across a land with no TV, no internet, no Twitter to provide images or context. Cobb pummeled a black groundskeeper, duked it out with a construction worker, brawled with a hotel bellboy. Truth or fiction?

He went into the seats to pound a fan with a disability, tangled with teammates, was charged by mobs in the stands who believed he'd spiked opponents on purpose, out of spite or downright nastiness. Real or unreal?

The legend of Ty Cobb was messy and complex. But it was never fully examined until this year. Until the release of Charles Leerhsen's fabulous new book, "Ty Cobb: A Terrible Beauty."

Isn't it amazing how actual reporting -- a real and thorough search for the facts -- can make us re-examine what we thought we knew, particularly about a man like this?

Ty Cobb is still one of baseball's most reviled figures. But should that be the case? B Bennett/Getty Images

Until now, Cobb was so widely believed to be a vicious, racist, wicked man that he showed up in a 2004 book titled "American Monsters," listed alongside such vile figures as Charles Manson, John Wilkes Booth and (of course) O.J. Simpson.

Cobb's reputation was so heinous that Ron Shelton, director of the 2004 film "Cobb," told Leerhsen: "It is widely known that Ty Cobb may have killed as many as three people."

His alleged unlikability was such an accepted "fact" that in "Field of Dreams," Shoeless Joe Jackson went out of his way to make sure Kevin Costner knew that Cobb didn't emerge from the corn field because "none of us could stand the son of a bitch when we were alive, so we told him to stick it."

Get the picture? This was a man so villainous, so loathsome, he made Lance Armstrong look like Roger Federer. He made Alex Rodriguez look like Tony Gwynn.

Except for one minor problem: A lot of those tales turned out not to be what's known in the reporting biz as, well, "true."

And Leerhsen admitted that that came as a shock to him, too. His experience in reporting and writing this book, he wrote, "taught me a lesson about how assumptions can shape our thinking, and hence our lives. Just because you've heard something a thousand times doesn't mean it's true."

But that's not just a lesson for him. That's a lesson for all of us.

As we find ourselves reflecting on Rose, Cobb and their historic anniversary, the commissioner of baseball, Rob Manfred, finds himself reflecting on Rose's turbo-charged case for reinstatement and for the Hall of Fame. Manfred began his baseball journey as a lawyer. So it's facts, not folktales or opinion polls, he'll be looking for.

But it's a funny thing about "facts." As I read Leerhsen's book, as I started thinking about the real meaning of this momentous 30th anniversary of Rose passing Cobb, I found myself pondering something I first learned in journalism school.

So many things we think of as "facts" are really assumptions. Pete Rose reminds us of that, loud and clear. Ty Cobb reminds us of that, just as loud, just as clear.

I'm a Hall of Fame voter. I'm surrounded by hundreds of voters whose mission in life has become to keep all the cheaters and scoundrels out of the Hall of Fame. But I often think, as I agonize over my ballot every fall: "Are we sure we can tell the cheaters and the scoundrels from the heroes and the role models?"

I'm pretty sure I can't. It's too complicated, too nuanced. Who knows how we'll view Pete Rose 10 years from now? Or 20? Or 30? Who knows how we'll view the stars of the PED era? Who knows how the next wave of voters will view anyone or anything? Who knows which "facts" will turn out to be all wrong, and which myths will turn out to be "facts"?

I've spent a lot of time kicking around the Ty Cobb saga with one of my editors, Matt Marrone. He read the Cobb book first and started off this conversation. He had a thought this week that was too eloquent not to share, because it sums up the moral of this story so perfectly.

"History isn't written in stone," he said, "even after it's etched into Hall of Fame plaques."

On this date 30 years ago, we thought we knew exactly how history would reflect the life and times of Peter Edward Rose and Tyrus Raymond Cobb. History, however, had other plans.