Many scientists believe there is a set limit to lifespan because the body's organs and tissue begin to wear out at a steady rate over time.

BBC: How old can we get?

If asking a billionaire to pay the same tax rate as a janitor makes me a warrior for the working class, I wear that with a badge of honor.

WHITEHOUSE: Congressional Black Caucus Foundation Phoenix Awards Dinner | The White House

"Those with wear will continue wearing down their teeth and ... if you keep grinding at this rate, you won't have any teeth, " she said.

CNN: Don't let stress be such a grind