The accuracy of Quantum Mechanics according to Richard Feynman?

Richard Feynman compared the [the precision of quantum mechanics] to predicting a distance as great as the width of North America to an accuracy of one human hair's breadth. (Dawkins, 2006, pg.36).

I can almost but not quite get my head around this quote, what exactly does it mean, what is meant by predicting the width of North America, based on what?

Does it simply mean that it would be possible to gauge the width of the continent to the scale of the breadth of a single human hair?

Thanks.

The accuracy of Quantum Mechanics according to Richard Feynman?

It has never been proven to be wrong. Accuracy to one part on 100 billion.

Proof:

3 000 x 5 280 x 12 = 190 080 000

each hair diameter= .001 inch

3 000 x 5 280 x 12 x 1 000 = 190 080 000 000 = 10^11

The accuracy of Quantum Mechanics according to Richard Feynman?

He's basically saying that in Quantum physics, things are VERY precise!

The accuracy of Quantum Mechanics according to Richard Feynman?

This quote from Richard Feynman is about the accuracy of quantum mechanics. The human hair / North America phrase is just attempting to give a model that we might comprehend in the world of our physical and everyday experience to show just what the mathematical precision on that microscopic scale would be if scaled-up to our macroscopic (life sized) environment.

The accuracy of Quantum Mechanics according to Richard Feynman?

In physics, theories live or die at the hands of the experimenters.

What Feynman is saying is that the theory of QED has been tested by the experimenters and found to agree within the limits of experimental error. That the experimental errors are so low that they are equivalent to being able to measure the width of the USA to the nearest hairs breadth.