Greatest of all time? Simone Biles is in the conversation

In 56 years of sports watching and 40 years of sports writing, two eyewitness moments rise above all others:

1. Usain Bolt sprinting through the curve in the 200 meters in Beijing, moving at a speed that seemed impossible.

2. Simone Biles twisting and levitating in Rio on her way to the all-around gold medal.

Most debates about the greatest athlete of all time skew toward our most popular sports and most celebrated performers.

Jim Brown was an otherworldly running back who also excelled at lacrosse and probably could have excelled at the decathlon. LeBron James is a 6-8, 250-pound physical specimen who is supremely conditioned and coordinated.

Michael Jordan and Tom Brady are our most celebrated major-sport winners, and it's possible that no athlete has ever won at all levels the way Maya Moore has. Bolt set world records in events that may represent the purest form of sport — no judges, officials or teammates come into play.

But I'm starting to wonder if Biles is the most remarkable, and perhaps greatest, athlete I've seen.

She is a dominant athlete in a sport not known for longevity. She is stunningly fast, powerful and agile, and as is the case with all gymnasts, she is required to possess enough athletic bravery to even attempt maneuvers that would land lesser athletes on their heads, and in the hospital.

Lynx coach Cheryl Reeve notes Biles' "extreme grace."

"Athleticism is one thing, but to combine that with grace …" Reeve said. "I recognize that in her because grace was not my thing.

"She was already talented, but this has gone to this place that is incredible to watch. I can't wait for what lies ahead for her. The God-given ability, the athleticism, combined that with a competitive fire and the most extreme grace, that's Simone Biles. It's incredible."

Comparing athletes from different sports and eras is an intriguing parlor game because of the impossibility of the task. You can't compare Michael Jordan and Simone Biles, or Bolt and Serena Williams.

Jordan was a dominant player, but he didn't win as many titles as Bill Russell or score as many points as Kareem Abdul-Jabbar. To believe that Jordan is the greatest is to impose your own parameters on the debate.

Here's why Biles has a chance to at least enter the conversation, for me if not for more traditional sports fans: She is doing what other humans can't do, what other women have never done, and is doing so in a way that fulfills the dictionary definition of "awesome."

The degree of difficulty in her sport is off any chart. I grew up hearing the saying, "The hardest thing to do in sports is hit a round baseball with a round bat." I would posit that performing a triple-double during a floor routine in which you hurl yourself to the ceiling and can't afford to make a single misstep is a little tougher.

Even comparing Biles and Bolt makes for an intriguing debate. Bolt mastered the purest form of sport — running faster than anyone ever had at two distances.

He is unique because of his performance, not because of his skill. He is not even considered a great technical runner by those capable of judging. He simply runs fast, employing a skill that most begin practicing, without instruction, at the age of 2.

Jim Thorpe. Jim Brown. Jordan. LeBron. Bo Jackson. Serena. Pele. Michael Phelps. Muhammad Ali. Bolt.

That list might contain the greatest athlete in history, but I've never seen any of them produce something as otherworldly as a Simone Biles floor routine — not even when Bolt flew through the curve in Beijing.